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Aono S, Tsuneta S, Nishioka N, Aoike T, Hirayama H, Ishizaka K, Kwon J, Yoneyama M, Fujima N, Kudo K. Comparison of Echo-Planar Imaging and Compressed Sensing in the Estimation of Flow Metrics from Aortic 4D Flow MR Imaging: A Healthy Volunteer Study. Magn Reson Med Sci 2024:mp.2023-0011. [PMID: 38556273 DOI: 10.2463/mrms.mp.2023-0011] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 04/02/2024] Open
Abstract
PURPOSE Prolonged scanning of time-resolved 3D phase-contrast MRI (4D flow MRI) limits its routine use in clinical practice. An echo-planar imaging (EPI)-based sequence and compressed sensing can reduce the scan duration. We aimed to determine the impact of EPI for 4D flow MRI on the scan duration, image quality, and quantitative flow metrics. METHODS This was a prospective study of 15 healthy volunteers (all male, mean age 33 ± 5 years). Conventional sensitivity encoding (SENSE), EPI with SENSE (EPI), and compressed SENSE (CS) (reduction factors: 6 and 12, respectively) were scanned.Scan duration, qualitative indexes of image quality, and quantitative flow parameters of net flow volume, maximum flow velocity, wall shear stress (WSS), and energy loss (EL) in the ascending aorta were assessed. Two-dimensional phase-contrast cine MRI (2D-PC) was considered the gold standard of net flow volume and maximum flow velocity. RESULTS Compared to SENSE, EPI and CS12 shortened scan durations by 71% and 73% (EPI, 4 min 39 sec; CS6, 7 min 29 sec; CS12, 4 min 14 sec; and SENSE, 15 min 51 sec). Visual image quality was significantly better for EPI than for SENSE and CS (P < 0.001). The net flow volumes obtained with SENSE, EPI, and CS12 and those obtained with 2D-PC were correlated well (r = 0.950, 0.871, and 0.850, respectively). However, the maximum velocity obtained with EPI was significantly underestimated (P < 0.010). The average WSS was significantly higher with EPI than with SENSE, CS6, and CS12 (P < 0.001, P = 0.040, and P = 0.012, respectively). The EL was significantly lower with EPI than with CS6 and CS12 (P = 0.002 and P = 0.007, respectively). CONCLUSION EPI reduced the scan duration, improved visual image quality, and was associated with more accurate net flow volume than CS. However, the flow velocity, WSS, and EL values obtained with EPI and other sequences may not be directly comparable.
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Affiliation(s)
- Satoru Aono
- Department of Radiological Technology, Hokkaido University Hospital, Sapporo, Hokkaido, Japan
| | - Satonori Tsuneta
- Department of Diagnostic and Interventional Radiology, Hokkaido University Hospital, Sapporo, Hokkaido, Japan
| | - Noriko Nishioka
- Department of Diagnostic and Interventional Radiology, Hokkaido University Hospital, Sapporo, Hokkaido, Japan
| | - Takuya Aoike
- Department of Radiological Technology, Hokkaido University Hospital, Sapporo, Hokkaido, Japan
| | - Hiroyuki Hirayama
- Department of Radiological Technology, Hokkaido University Hospital, Sapporo, Hokkaido, Japan
| | - Kinya Ishizaka
- Department of Radiological Technology, Hokkaido University Hospital, Sapporo, Hokkaido, Japan
| | | | | | - Noriyuki Fujima
- Department of Diagnostic and Interventional Radiology, Hokkaido University Hospital, Sapporo, Hokkaido, Japan
| | - Kohsuke Kudo
- Department of Diagnostic Imaging, Hokkaido University Graduate School of Medicine, Hokkaido University, Sapporo, Hokkaido, Japan
- Global Center for Biomedical Science and Engineering, Faculty of Medicine, Hokkaido University, Sapporo, Hokkaido, Japan
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Yılmaz E, Güldoğan N, Ulus S, Türk EB, Mısır ME, Arslan A, Arıbal ME. Diagnostic value of synthetic diffusion-weighted imaging on breast magnetic resonance imaging assessment: comparison with conventional diffusion-weighted imaging. Diagn Interv Radiol 2024; 30:91-98. [PMID: 37888786 PMCID: PMC10916533 DOI: 10.4274/dir.2023.232466] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/21/2023] [Accepted: 10/22/2023] [Indexed: 10/28/2023]
Abstract
PURPOSE To compare images generated by synthetic diffusion-weighted imaging (sDWI) with those from conventional DWI in terms of their diagnostic performance in detecting breast lesions when performing breast magnetic resonance imaging (MRI). METHODS A total of 128 consecutive patients with 135 enhanced lesions who underwent dynamic MRI between 2018 and 2021 were included. The sDWI and DWI signals were compared by three radiologists with at least 10 years of experience in breast radiology. RESULTS Of the 82 malignant lesions, 91.5% were hyperintense on sDWI and 73.2% were hyperintense on DWI. Of the 53 benign lesions, 71.7% were isointense on sDWI and 37.7% were isointense on DWI. sDWI provides accurate signal intensity data with statistical significance compared with DWI (P < 0.05). The diagnostic performance of DWI and sDWI to differentiate malignant breast masses from benign masses was as follows: sensitivity 73.1% [95% confidence interval (CI): 62-82], specificity 37.7% (95% CI: 24-52); sensitivity 91.5% (95% CI: 83-96), specificity 71.7% (95% CI: 57-83), respectively. The diagnostic accuracy of DWI and sDWI was 59.2% and 83.7%, respectively. However, when the DWI images were evaluated with apparent diffusion coefficient mapping and compared with the sDWI images, the sensitivity was 92.68% (95% CI: 84-97) and the specificity was 79.25% (95% CI: 65-89) with no statistically significant difference. The inter-reader agreement was almost perfect (P < 0.001). CONCLUSION Synthetic DWI is superior to DWI for lesion visibility with no additional acquisition time and should be taken into consideration when conducting breast MRI scans. The evaluation of sDWI in routine MRI reporting will increase diagnostic accuracy.
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Affiliation(s)
- Ebru Yılmaz
- Acıbadem Altunizade Hospital Breast Center, Department of Radiology, İstanbul, Türkiye
| | - Nilgün Güldoğan
- Acıbadem Altunizade Hospital Breast Center, Department of Radiology, İstanbul, Türkiye
| | - Sıla Ulus
- Acıbadem Ataşehir Hospital, Department of Radiology, İstanbul, Türkiye
| | - Ebru Banu Türk
- Acıbadem Altunizade Hospital Breast Center, Department of Radiology, İstanbul, Türkiye
| | - Mustafa Enes Mısır
- Acıbadem Mehmet Ali Aydınlar University, Department of Radiology, İstanbul, Türkiye
| | - Aydan Arslan
- University of Health Sciences Türkiye, Ümraniye Training and Research Hospital, Clinic of Radiology, İstanbul, Türkiye
| | - Mustafa Erkin Arıbal
- Acıbadem Mehmet Ali Aydınlar University, Department of Radiology, İstanbul, Türkiye
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Kim JH, Im JG, Park SH. Measurement of changes in cerebrospinal fluid pulsation after traumatic brain injury using echo-planar imaging-based functional MRI. NMR Biomed 2024; 37:e5061. [PMID: 37839870 DOI: 10.1002/nbm.5061] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/23/2023] [Revised: 09/19/2023] [Accepted: 09/21/2023] [Indexed: 10/17/2023]
Abstract
Traumatic brain injury (TBI) is a major public health concern worldwide, with a high incidence and a significant impact on morbidity and mortality. The alteration of cerebrospinal fluid (CSF) dynamics after TBI is a well-known phenomenon; however, the underlying mechanisms and their implications for cognitive function are not fully understood. In this study, we propose a new approach to studying the alteration of CSF dynamics in TBI patients. Our approach involves using conventional echo-planar imaging-based functional MRI with no additional scan, allowing for simultaneous assessment of functional CSF dynamics and blood oxygen level-dependent-based functional brain activities. We utilized two previously suggested indices of (i) CSFpulse, and (ii) correlation between global brain activity and CSF inflow. Using CSFpulse, we demonstrated a significant decrease in CSF pulsation following TBI (p < 0.05), which was consistent with previous studies. Furthermore, we confirmed that the decrease in CSF pulsation was most prominent in the early months after TBI, which could be explained by ependymal ciliary loss, intracranial pressure increment, or aquaporin-4 dysregulation. We also observed a decreasing trend in the correlation between global brain activity and CSF inflow in TBI patients (p < 0.05). Our findings suggest that the decreased CSF pulsation after TBI could lead to the accumulation of toxic substances in the brain and an adverse effect on brain function. Further longitudinal studies with larger sample sizes, TBI biomarker data, and various demographic information are needed to investigate the association between cognitive decline and CSF dynamics after TBI. Overall, this study sheds light on the potential role of altered CSF dynamics in TBI-induced neurologic symptoms and may contribute to the development of novel therapeutic interventions.
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Affiliation(s)
- Jun-Hee Kim
- Department of Bio and Brain Engineering, Korea Advanced Institute of Science and Technology (KAIST), Daejeon, South Korea
| | - Jae-Geun Im
- Department of Bio and Brain Engineering, Korea Advanced Institute of Science and Technology (KAIST), Daejeon, South Korea
| | - Sung-Hong Park
- Department of Bio and Brain Engineering, Korea Advanced Institute of Science and Technology (KAIST), Daejeon, South Korea
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Numamoto H, Fujimoto K, Miyake KK, Fushimi Y, Okuchi S, Imai R, Kondo H, Saga T, Nakamoto Y. Evaluating Reproducibility of the ADC and Distortion in Diffusion-weighted Imaging (DWI) with Reverse Encoding Distortion Correction (RDC). Magn Reson Med Sci 2023:mp.2023-0102. [PMID: 37952942 DOI: 10.2463/mrms.mp.2023-0102] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2023] Open
Abstract
PURPOSE To compare image distortion and reproducibility of quantitative values between reverse encoding distortion correction (RDC) diffusion-weighted imaging (DWI) and conventional DWI techniques in a phantom study and in healthy volunteers. METHODS This prospective study was conducted with the approval of our institutional review board. Written informed consent was obtained from each participant. RDC-DWIs were created from images obtained at 3T in three orthogonal directions in a phantom and in 10 participants (mean age, 70.9 years; age range, 63-83 years). Images without distortion correction (noDC-DWI) and those corrected with B0 (B0c-DWI) were also created. To evaluate distortion, coefficients of variation were calculated for each voxel and ROIs were placed at four levels of the brain. To evaluate the reproducibility of apparent diffusion coefficient (ADC) measurements, intra- and inter-scan variability (%CVADC) were calculated from repeated scans of the phantom. Analysis was performed using Wilcoxon signed-rank test with Bonferroni correction, and P < 0.05 was considered statistically significant. RESULTS In the phantom, distortion was less in RDC-DWI than in B0c-DWI (P < 0.006), and was less in B0c-DWI than in noDC-DWI (P < 0.006). Intra-scan %CVADC was within 1.30%, and inter-scan %CVADC was within 2.99%. In the volunteers, distortion was less in RDC-DWI than in B0c-DWI in three of four locations (P < 0.006), and was less in B0c-DWI than in noDC-DWI (P < 0.006). At the middle cerebellar peduncle, distortion was less in RDC-DWI than in noDC-DWI (P < 0.006), and was less in noDC-DWI than in B0c-DWI (P < 0.0177). CONCLUSION In both the phantom and in volunteers, distortion was the least in RDC-DWI than in B0c-DWI and noDC-DWI.
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Affiliation(s)
- Hitomi Numamoto
- Department of Advanced Imaging in Medical Magnetic Resonance, Graduate School of Medicine, Kyoto University, Kyoto, Kyoto, Japan
| | - Koji Fujimoto
- Department of Advanced Imaging in Medical Magnetic Resonance, Graduate School of Medicine, Kyoto University, Kyoto, Kyoto, Japan
| | - Kanae Kawai Miyake
- Department of Advanced Imaging in Medical Magnetic Resonance, Graduate School of Medicine, Kyoto University, Kyoto, Kyoto, Japan
| | - Yasutaka Fushimi
- Department of Diagnostic Imaging and Nuclear Medicine, Graduate School of Medicine, Kyoto University, Kyoto, Kyoto, Japan
| | - Sachi Okuchi
- Department of Diagnostic Imaging and Nuclear Medicine, Graduate School of Medicine, Kyoto University, Kyoto, Kyoto, Japan
| | - Rimika Imai
- Canon Medical Systems Corporation, Otawara, Tochigi, Japan
| | - Hiroki Kondo
- Canon Medical Systems Corporation, Otawara, Tochigi, Japan
| | - Tsuneo Saga
- Department of Advanced Imaging in Medical Magnetic Resonance, Graduate School of Medicine, Kyoto University, Kyoto, Kyoto, Japan
| | - Yuji Nakamoto
- Department of Diagnostic Imaging and Nuclear Medicine, Graduate School of Medicine, Kyoto University, Kyoto, Kyoto, Japan
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Stumpe N, Güden-Silber T, Schneckmann R, Wolters K, Lamb H, Grandoch M, Flögel U. In Vivo Mapping of Deep Tissue pO 2 in a Murine Model of Peripheral Artery Disease by Noninvasive 19F MR Relaxometry. Arterioscler Thromb Vasc Biol 2023; 43:597-598. [PMID: 36756882 DOI: 10.1161/atvbaha.122.318548] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/10/2023]
Affiliation(s)
- Nicolas Stumpe
- Institute for Molecular Cardiology, Heinrich Heine University, Düsseldorf, Germany (N.S., T.G.-S., U.F.)
- Cardiovascular Imaging, University Medical Center, Leiden, the Netherlands (N.S., H.L.)
| | - Tuba Güden-Silber
- Institute for Molecular Cardiology, Heinrich Heine University, Düsseldorf, Germany (N.S., T.G.-S., U.F.)
| | - Rebekka Schneckmann
- Institute for Translational Pharmacology, Heinrich Heine University, Düsseldorf, Germany (R.S., K.W., M.G.)
| | - Katharina Wolters
- Institute for Translational Pharmacology, Heinrich Heine University, Düsseldorf, Germany (R.S., K.W., M.G.)
| | - Hildo Lamb
- Cardiovascular Imaging, University Medical Center, Leiden, the Netherlands (N.S., H.L.)
| | - Maria Grandoch
- Institute for Translational Pharmacology, Heinrich Heine University, Düsseldorf, Germany (R.S., K.W., M.G.)
| | - Ulrich Flögel
- Institute for Molecular Cardiology, Heinrich Heine University, Düsseldorf, Germany (N.S., T.G.-S., U.F.)
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Kumazawa S, Yoshiura T. Estimation of undistorted images in brain echo-planar images with distortions using the conjugate gradient method with anatomical regularization. Med Phys 2022; 49:7531-7544. [PMID: 35901497 PMCID: PMC10086945 DOI: 10.1002/mp.15881] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2021] [Revised: 05/27/2022] [Accepted: 07/07/2022] [Indexed: 12/27/2022] Open
Abstract
PURPOSE Although echo-planar imaging (EPI) is widely used for diffusion magnetic resonance (MR) imaging, EPI images suffer from susceptibility-induced geometric distortions. We herein propose a new estimation method for undistorted EPI images using anatomical T1 -weighted images (T1 WIs) based on the physics of MR imaging. METHODS Our proposed method estimates the undistorted EPI image in the image domain while estimating the magnetic field inhomogeneity map using the conjugate gradient method with anatomical regularization. Our method synthesizes the distorted image to match the measured EPI image containing geometric distortions by alternately updating the undistorted EPI image and the magnetic field inhomogeneity map. We evaluated our proposed method and compared it with a nonrigid registration-based distortion correction method using simulated data and using real data. In the evaluation of the estimation of the magnetic field inhomogeneity map, we used the normalized root-mean-squared error (NRMSE) between the estimated results and the ground truth. In the evaluation of the estimation of undistorted images, we used mutual information (MI) between the undistorted EPI image and the anatomical T1 WI. RESULTS Using the simulated data, the means and standard deviations of the NRMSE values in the nonrigid registration-based method and proposed method were 1.29 ± 0.63 and 0.64 ± 0.30, respectively. The MI values in the proposed method were larger than those in the nonrigid registration-based method in all evaluated slices. For the real data, the proposed method improved the distortion, and the MI values in the proposed method were larger than those in the nonrigid registration-based method. In the estimation of the magnetic field inhomogeneity map, the NRMSE values in our method were smaller than those in the nonrigid registration-based method. CONCLUSIONS We demonstrated that our proposed method can estimate the regions with compressed distortions that are not well represented by the nonrigid registration-based methods. The results suggest that the proposed method could be useful in analyses combining EPI images with T1 WIs.
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Affiliation(s)
- Seiji Kumazawa
- Department of Radiological Technology, Faculty of Health Sciences, Hokkaido University of Science, Sapporo, Hokkaido, Japan
| | - Takashi Yoshiura
- Department of Radiology, Graduate School of Medical and Dental Sciences, Kagoshima University, Kagoshima, Kyushu, Japan
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Hong JS, Hermann I, Zöllner FG, Schad LR, Wang SJ, Lee WK, Chen YL, Chang Y, Wu YT. Acceleration of Magnetic Resonance Fingerprinting Reconstruction Using Denoising and Self-Attention Pyramidal Convolutional Neural Network. Sensors (Basel) 2022; 22:s22031260. [PMID: 35162007 PMCID: PMC8838455 DOI: 10.3390/s22031260] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 12/01/2021] [Revised: 01/27/2022] [Accepted: 02/05/2022] [Indexed: 02/01/2023]
Abstract
Magnetic resonance fingerprinting (MRF) based on echo-planar imaging (EPI) enables whole-brain imaging to rapidly obtain T1 and T2* relaxation time maps. Reconstructing parametric maps from the MRF scanned baselines by the inner-product method is computationally expensive. We aimed to accelerate the reconstruction of parametric maps for MRF-EPI by using a deep learning model. The proposed approach uses a two-stage model that first eliminates noise and then regresses the parametric maps. Parametric maps obtained by dictionary matching were used as a reference and compared with the prediction results of the two-stage model. MRF-EPI scans were collected from 32 subjects. The signal-to-noise ratio increased significantly after the noise removal by the denoising model. For prediction with scans in the testing dataset, the mean absolute percentage errors between the standard and the final two-stage model were 3.1%, 3.2%, and 1.9% for T1, and 2.6%, 2.3%, and 2.8% for T2* in gray matter, white matter, and lesion locations, respectively. Our proposed two-stage deep learning model can effectively remove noise and accurately reconstruct MRF-EPI parametric maps, increasing the speed of reconstruction and reducing the storage space required by dictionaries.
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Affiliation(s)
- Jia-Sheng Hong
- Department of Biomedical Imaging and Radiological Sciences, National Yang Ming Chiao Tung University, Taipei 112, Taiwan; (J.-S.H.); (W.-K.L.)
| | - Ingo Hermann
- Computer Assisted Clinical Medicine, Mannheim Institute for Intelligent Systems in Medicine, Medical Faculty Mannheim, Heidelberg University, 68167 Mannheim, Germany; (I.H.); (F.G.Z.); (L.R.S.)
| | - Frank Gerrit Zöllner
- Computer Assisted Clinical Medicine, Mannheim Institute for Intelligent Systems in Medicine, Medical Faculty Mannheim, Heidelberg University, 68167 Mannheim, Germany; (I.H.); (F.G.Z.); (L.R.S.)
| | - Lothar R. Schad
- Computer Assisted Clinical Medicine, Mannheim Institute for Intelligent Systems in Medicine, Medical Faculty Mannheim, Heidelberg University, 68167 Mannheim, Germany; (I.H.); (F.G.Z.); (L.R.S.)
| | - Shuu-Jiun Wang
- Department of Neurology, Neurological Institute, Taipei Veterans General Hospital, Taipei 112, Taiwan;
- College of Medicine, National Yang Ming Chiao Tung University, Taipei 112, Taiwan
- Brain Research Center, National Yang Ming Chiao Tung University, Taipei 112, Taiwan
| | - Wei-Kai Lee
- Department of Biomedical Imaging and Radiological Sciences, National Yang Ming Chiao Tung University, Taipei 112, Taiwan; (J.-S.H.); (W.-K.L.)
| | - Yung-Lin Chen
- Institute of Biophotonics, National Yang Ming Chiao Tung University, Taipei 112, Taiwan; (Y.-L.C.); (Y.C.)
| | - Yu Chang
- Institute of Biophotonics, National Yang Ming Chiao Tung University, Taipei 112, Taiwan; (Y.-L.C.); (Y.C.)
| | - Yu-Te Wu
- Brain Research Center, National Yang Ming Chiao Tung University, Taipei 112, Taiwan
- Institute of Biophotonics, National Yang Ming Chiao Tung University, Taipei 112, Taiwan; (Y.-L.C.); (Y.C.)
- Correspondence:
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Schmitt T, Rieger JW. Recommendations of Choice of Head Coil and Prescan Normalize Filter Depend on Region of Interest and Task. Front Neurosci 2021; 15:735290. [PMID: 34776844 PMCID: PMC8585748 DOI: 10.3389/fnins.2021.735290] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2021] [Accepted: 09/21/2021] [Indexed: 11/23/2022] Open
Abstract
The performance of MRI head coils together with the influence of the prescan normalize filter in different brain regions was evaluated. Functional and structural data were recorded from 26 participants performing motor, auditory, and visual tasks in different conditions: with the 20- and 64-channel Siemens head/neck coil and the prescan normalize filter turned ON or OFF. Data were analyzed with the MRIQC tool to evaluate data quality differences. The functional data were statistically evaluated by comparison of the β estimates and the time-course signal-to-noise ratio (tSNR) in four regions of interest, i.e., the auditory, visual, and motor cortices and the thalamus. The MRIQC tool indicated a better data quality for both functional and structural data with the prescan normalize filter, with an advantage for the 20-channel head coil in functional data and an advantage for the 64-channel head coil in structural measurements. Nevertheless, recommendations for the functional data regarding choice of head coils and prescan normalize filter depend on the brain regions of interest. Higher β estimates and tSNR values occurred in the auditory cortex and thalamus with the prescan normalize filter, whereas the contrary was true for the visual and motor cortices. Due to higher β estimates in the visual cortex in the 64-channel head coil, this head coil is recommended for studies investigating the visual cortex. For most of the research questions, the 20-channel head coil is better suited for functional experiments, with the prescan normalize filter, especially when investigating deep brain areas. For anatomical studies, the 64-channel head coil seemed to be the better choice.
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Affiliation(s)
- Tina Schmitt
- Neuroimaging Unit, School of Medicine and Health Sciences, Carl von Ossietzky Universität Oldenburg, Oldenburg, Germany
| | - Jochem W Rieger
- Neuroimaging Unit, School of Medicine and Health Sciences, Carl von Ossietzky Universität Oldenburg, Oldenburg, Germany.,Department of Psychology, School of Medicine and Health Sciences, Carl von Ossietzky Universität Oldenburg, Oldenburg, Germany.,Cluster of Excellence Hearing4all, Carl von Ossietzky Universität Oldenburg, Oldenburg, Germany
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Ohno N, Yoshida K, Ueda Y, Makino Y, Miyati T, Gabata T, Kobayashi S. Diffusion-weighted Imaging of the Abdomen during a Single Breath-hold Using Simultaneous-multislice Echo-planar Imaging. Magn Reson Med Sci 2021; 22:253-262. [PMID: 34732598 PMCID: PMC10086397 DOI: 10.2463/mrms.mp.2021-0087] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022] Open
Abstract
PURPOSE This multi-scanner study aimed to investigate the validity of single breath-hold (BH) diffusion-weighted imaging (DWI) using simultaneous-multislice (SMS) echo-planar imaging in multiple abdominal organs to enable faster acquisition and reliable quantification of apparent diffusion coefficient (ADC). METHODS SNR, geometric distortion (GD), and ADC in a phantom; the ADC in the liver, renal cortex, paraspinal muscle, spleen, and pancreas; and the signal intensity ratio of the portal vein-to-muscle (SIRPV-M) in healthy volunteers were compared between BH- and respiratory-triggered (RT) DWI with b-values of 0 and 800 s/mm2 in two different MRI scanners. RESULTS The phantom study showed that the SNR of BH-DWI was significantly lower than that of the RT-DWI (P < 0.05 for both scanners), whereas the GD and ADC of BH-DWI did not differ significantly from those of the RT-DWI (P = 0.09-0.60). In the volunteer study, the scan times were 23 seconds for BH-DWI and 184±33 seconds for RT-DWI, respectively. The ADC of the liver in BH-DWI was significantly lower than that in RT-DWI (P < 0.05 for both scanners), whereas there were no significant differences in the ADCs of the renal cortex, paraspinal muscle, spleen, or pancreas between BH-DWI and RT-DWI (P = 0.07-0.86). The SIRPV-M in BH-DWI was significantly smaller than in RT-DWI (P < 0.05 for both scanners). CONCLUSION The proposed method enables the acquisition of abdominal diffusion-weighted images in a single BH.
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Affiliation(s)
- Naoki Ohno
- Faculty of Health Sciences, Institute of Medical, Pharmaceutical and Health Sciences, Kanazawa University
| | | | - Yu Ueda
- MR Clinical Science, Philips Japan, Ltd
| | - Yuki Makino
- Department of Radiological Technology, Kanazawa University Hospital
| | - Tosiaki Miyati
- Faculty of Health Sciences, Institute of Medical, Pharmaceutical and Health Sciences, Kanazawa University
| | | | - Satoshi Kobayashi
- Faculty of Health Sciences, Institute of Medical, Pharmaceutical and Health Sciences, Kanazawa University.,Department of Radiology, Kanazawa University Hospital.,Department of Radiological Technology, Kanazawa University Hospital
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Yoshizako T, Yoshida R, Asou H, Nakamura M, Kitagaki H. Comparison between turbo spin-echo and echo planar diffusion-weighted imaging of the female pelvis with 3T MRI. Acta Radiol Open 2021; 10:2058460121994737. [PMID: 33747551 PMCID: PMC7903838 DOI: 10.1177/2058460121994737] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/03/2021] [Accepted: 01/26/2021] [Indexed: 12/02/2022] Open
Abstract
Background Echo-planar imaging (EPI)-diffusion-weighted imaging (DWI) may take unclear image affected by susceptibility, geometric distortions and chemical shift artifacts. Purpose To compare the image quality and usefulness of EPI-DWI and turbo spin echo (TSE)-DWI in female patients who required imaging of the pelvis. Material and Methods All 57 patients were examined with a 3.0-T MR scanner. Both TSE- and EPI-DWI were performed with b values of 0 and 1000 s/mm2. We compared geometric distortion, the contrast ratio (CR) of the myometrium to the muscle and the apparent diffusion coefficient (ADC) values for the myometrium and lesion. Two radiologists scored the TSE- and EPI-DWI of each patient for qualitative evaluation. Results The mean percent distortion was significantly smaller with TSE- than EPI-DWI (p = 0.00). The CR was significantly higher with TSE- than EPI-DWI (p = 0.003). There was a significant difference in the ADC value for the uterus and lesions between the EPI- and TSE-DWI (p < 0.05). Finally, the ADC values of cancer were significantly different from those for the uterus and benign with both the two sequences (p < 0.05). The scores for ghosting artifacts were higher with TSE- than EPI-DWI (p = 0.019). But there were no significant differences between TSE- and EPI-DWI with regard to image contrast and overall image quality. Conclusion TSE-DWI on the female pelvis by 3T MRI produces less distortion and higher CR than EPI-DWI, but there is no difference in contrast and image quality.
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Affiliation(s)
- Takeshi Yoshizako
- Department of Radiology, Shimane University Faculty of Medicine, Enya Izumo, Japan
| | - Rika Yoshida
- Department of Radiology, Shimane University Faculty of Medicine, Enya Izumo, Japan
| | - Hiroya Asou
- Department of Radiology, Shimane University Faculty of Medicine, Enya Izumo, Japan
| | - Megumi Nakamura
- Department of Radiology, Shimane University Faculty of Medicine, Enya Izumo, Japan
| | - Hajime Kitagaki
- Department of Radiology, Shimane University Faculty of Medicine, Enya Izumo, Japan
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Lobos RA, Hoge WS, Javed A, Liao C, Setsompop K, Nayak KS, Haldar JP. Robust autocalibrated structured low-rank EPI ghost correction. Magn Reson Med 2020; 85:3403-3419. [PMID: 33332652 DOI: 10.1002/mrm.28638] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/21/2020] [Revised: 11/12/2020] [Accepted: 11/16/2020] [Indexed: 12/16/2022]
Abstract
PURPOSE We propose and evaluate a new structured low-rank method for echo-planar imaging (EPI) ghost correction called Robust Autocalibrated LORAKS (RAC-LORAKS). The method can be used to suppress EPI ghosts arising from the differences between different readout gradient polarities and/or the differences between different shots. It does not require conventional EPI navigator signals, and is robust to imperfect autocalibration data. METHODS Autocalibrated LORAKS is a previous structured low-rank method for EPI ghost correction that uses GRAPPA-type autocalibration data to enable high-quality ghost correction. This method works well when the autocalibration data are pristine, but performance degrades substantially when the autocalibration information is imperfect. RAC-LORAKS generalizes Autocalibrated LORAKS in two ways. First, it does not completely trust the information from autocalibration data, and instead considers the autocalibration and EPI data simultaneously when estimating low-rank matrix structure. Second, it uses complementary information from the autocalibration data to improve EPI reconstruction in a multi-contrast joint reconstruction framework. RAC-LORAKS is evaluated using simulations and in vivo data, including comparisons to state-of-the-art methods. RESULTS RAC-LORAKS is demonstrated to have good ghost elimination performance compared to state-of-the-art methods in several complicated EPI acquisition scenarios (including gradient-echo brain imaging, diffusion-encoded brain imaging, and cardiac imaging). CONCLUSIONS RAC-LORAKS provides effective suppression of EPI ghosts and is robust to imperfect autocalibration data.
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Affiliation(s)
- Rodrigo A Lobos
- Ming Hsieh Department of Electrical and Computer Engineering, University of Southern California, Los Angeles, CA, USA.,Signal and Image Processing Institute, University of Southern California, Los Angeles, CA, USA
| | - W Scott Hoge
- Department of Radiology, Brigham and Women's Hospital, Boston, MA, USA.,Department of Radiology, Harvard Medical School, Boston, MA, USA
| | - Ahsan Javed
- Ming Hsieh Department of Electrical and Computer Engineering, University of Southern California, Los Angeles, CA, USA.,Signal and Image Processing Institute, University of Southern California, Los Angeles, CA, USA
| | - Congyu Liao
- Department of Radiology, Harvard Medical School, Boston, MA, USA.,Athinoula A. Martinos Center for Biomedical Imaging, Charlestown, MA, USA
| | - Kawin Setsompop
- Department of Radiology, Harvard Medical School, Boston, MA, USA.,Athinoula A. Martinos Center for Biomedical Imaging, Charlestown, MA, USA
| | - Krishna S Nayak
- Ming Hsieh Department of Electrical and Computer Engineering, University of Southern California, Los Angeles, CA, USA.,Signal and Image Processing Institute, University of Southern California, Los Angeles, CA, USA.,Department of Biomedical Engineering, University of Southern California, Los Angeles, CA, USA
| | - Justin P Haldar
- Ming Hsieh Department of Electrical and Computer Engineering, University of Southern California, Los Angeles, CA, USA.,Signal and Image Processing Institute, University of Southern California, Los Angeles, CA, USA.,Department of Biomedical Engineering, University of Southern California, Los Angeles, CA, USA
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12
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Lee Y, Wilm BJ, Brunner DO, Gross S, Schmid T, Nagy Z, Pruessmann KP. On the signal-to-noise ratio benefit of spiral acquisition in diffusion MRI. Magn Reson Med 2020; 85:1924-1937. [PMID: 33280160 DOI: 10.1002/mrm.28554] [Citation(s) in RCA: 18] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/07/2020] [Revised: 09/15/2020] [Accepted: 09/22/2020] [Indexed: 12/20/2022]
Abstract
PURPOSE Spiral readouts combine several favorable properties that promise superior net sensitivity for diffusion imaging. The purpose of this study is to verify the signal-to-noise ratio (SNR) benefit of spiral acquisition in comparison with current echo-planar imaging (EPI) schemes. METHODS Diffusion-weighted in vivo brain data from three subjects were acquired with a single-shot spiral sequence and several variants of single-shot EPI, including full-Fourier and partial-Fourier readouts as well as different diffusion-encoding schemes. Image reconstruction was based on an expanded signal model including field dynamics obtained by concurrent field monitoring. The effective resolution of each sequence was matched to that of full-Fourier EPI with 1 mm nominal resolution. SNR maps were generated by determining the noise statistics of the raw data and analyzing the propagation of equivalent synthetic noise through image reconstruction. Using the same approach, maps of noise amplification due to parallel imaging (g-factor) were calculated for different acceleration factors. RESULTS Relative to full-Fourier EPI at b = 0 s/mm2 , spiral acquisition yielded SNR gains of 42-88% and 40-89% in white and gray matter, respectively, depending on the diffusion-encoding scheme. Relative to partial-Fourier EPI, the gains were 36-44% and 34-42%. Spiral g-factor maps exhibited less spatial variation and lower maxima than their EPI counterparts. CONCLUSION Spiral readouts achieve significant SNR gains in the order of 40-80% over EPI in diffusion imaging at 3T. Combining systematic effects of shorter echo time, readout efficiency, and favorable g-factor behavior, similar benefits are expected across clinical and neurosciences uses of diffusion imaging.
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Affiliation(s)
- Yoojin Lee
- Institute for Biomedical Engineering, ETH Zurich and University of Zurich, Zurich, Switzerland.,Laboratory for Social and Neural Systems Research, University of Zurich, Zurich, Switzerland
| | - Bertram J Wilm
- Institute for Biomedical Engineering, ETH Zurich and University of Zurich, Zurich, Switzerland
| | - David O Brunner
- Institute for Biomedical Engineering, ETH Zurich and University of Zurich, Zurich, Switzerland
| | - Simon Gross
- Institute for Biomedical Engineering, ETH Zurich and University of Zurich, Zurich, Switzerland
| | - Thomas Schmid
- Institute for Biomedical Engineering, ETH Zurich and University of Zurich, Zurich, Switzerland
| | - Zoltan Nagy
- Laboratory for Social and Neural Systems Research, University of Zurich, Zurich, Switzerland
| | - Klaas P Pruessmann
- Institute for Biomedical Engineering, ETH Zurich and University of Zurich, Zurich, Switzerland
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13
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Patzig F, Mildner T, Schlumm T, Müller R, Möller HE. Deconvolution-based distortion correction of EPI using analytic single-voxel point-spread functions. Magn Reson Med 2020; 85:2445-2461. [PMID: 33220010 DOI: 10.1002/mrm.28591] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/17/2020] [Revised: 10/19/2020] [Accepted: 10/19/2020] [Indexed: 11/11/2022]
Abstract
PURPOSE To develop a postprocessing algorithm that corrects geometric distortions due to spatial variations of the static magnetic field amplitude, B0 , and effects from relaxation during signal acquisition in EPI. THEORY AND METHODS An analytic, complex point-spread function is deduced for k-space trajectories of EPI variants and applied to corresponding acquisitions in a resolution phantom and in human volunteers at 3 T. With the analytic point-spread function and experimental maps of B0 (and, optionally, the effective transverse relaxation time, T 2 * ) as input, a point-spread function matrix operator is devised for distortion correction by a Thikonov-regularized deconvolution in image space. The point-spread function operator provides additional information for an appropriate correction of the signal intensity distribution. A previous image combination algorithm for acquisitions with opposite phase blip polarities is adapted to the proposed method to recover destructively interfering signal contributions. RESULTS Applications of the proposed deconvolution-based distortion correction ("DecoDisCo") algorithm demonstrate excellent distortion corrections and superior performance regarding the recovery of an undistorted intensity distribution in comparison to a multifrequency reconstruction. Examples include full and partial Fourier standard EPI scans as well as double-shot center-out trajectories. Compared with other distortion-correction approaches, DecoDisCo permits additional deblurring to obtain sharper images in cases of significant T 2 * effects. CONCLUSION Robust distortion corrections in EPI acquisitions are feasible with high quality by regularized deconvolution with an analytic point-spread function. The general algorithm, which is publicly released on GitHub, can be straightforwardly adapted for specific EPI variants or other acquisition schemes.
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Affiliation(s)
- Franz Patzig
- Max Planck Institute for Human Cognitive and Brain Sciences, Leipzig, Germany
| | - Toralf Mildner
- Max Planck Institute for Human Cognitive and Brain Sciences, Leipzig, Germany
| | - Torsten Schlumm
- Max Planck Institute for Human Cognitive and Brain Sciences, Leipzig, Germany
| | - Roland Müller
- Max Planck Institute for Human Cognitive and Brain Sciences, Leipzig, Germany
| | - Harald E Möller
- Max Planck Institute for Human Cognitive and Brain Sciences, Leipzig, Germany
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14
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Caparelli EC, Zhai T, Yang Y. Simultaneous Transcranial Magnetic Stimulation and Functional Magnetic Resonance Imaging: Aspects of Technical Implementation. Front Neurosci 2020; 14:554714. [PMID: 33132819 PMCID: PMC7550427 DOI: 10.3389/fnins.2020.554714] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/22/2020] [Accepted: 09/07/2020] [Indexed: 12/02/2022] Open
Abstract
The simultaneous transcranial magnetic stimulation (TMS) and functional magnetic resonance imaging (fMRI) offers a unique opportunity to non-invasively stimulate brain circuits while simultaneously monitoring changes in brain activity. However, to take advantage of this multimodal technique, some technical issues need to be considered/addressed. In this work, we evaluated technical issues associated with the setup and utilization of this multimodal tool, such as the use of a large single-channel radio frequency (rf) coil, and the artifacts induced by TMS when interleaved with the echo-planar imaging (EPI) sequence. We demonstrated that good image quality can be achieved with this rf coil and that the adoption of axial imaging orientation in conjunction with a safe interval of 100 ms, between the TMS pulse and imaging acquisition, is a suitable combination to eliminate potential image artifacts when using the combined TMS-fMRI technique in 3-T MRI scanners.
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Affiliation(s)
- Elisabeth C Caparelli
- Neuroimaging Research Branch, National Institute on Drug Abuse, National Institutes of Health, Baltimore, MD, United States
| | - Tianye Zhai
- Neuroimaging Research Branch, National Institute on Drug Abuse, National Institutes of Health, Baltimore, MD, United States
| | - Yihong Yang
- Neuroimaging Research Branch, National Institute on Drug Abuse, National Institutes of Health, Baltimore, MD, United States
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15
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Ryu JK, Jung WB, Yu J, Son JP, Lee SK, Kim SG, Park JY. An equal-TE ultrafast 3D gradient-echo imaging method with high tolerance to magnetic susceptibility artifacts: Application to BOLD functional MRI. Magn Reson Med 2020; 85:1986-2000. [PMID: 33107102 DOI: 10.1002/mrm.28564] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2020] [Revised: 09/24/2020] [Accepted: 10/01/2020] [Indexed: 12/26/2022]
Abstract
PURPOSE To develop an ultrafast 3D gradient echo-based MRI method with constant TE and high tolerance to B0 inhomogeneity, dubbed ERASE (equal-TE rapid acquisition with sequential excitation), and to introduce its use in BOLD functional MRI (fMRI). THEORY AND METHODS Essential features of ERASE, including spin behavior, were characterized, and a comparison study was conducted with conventional EPI. To demonstrate high tolerance to B0 inhomogeneity, in vivo imaging of the mouse brain with a fiber-optic implant was performed at 9.4 T, and human brain imaging (including the orbitofrontal cortex) was performed at 3 T and 7 T. To evaluate the performance of ERASE in BOLD-fMRI, the characteristics of SNR and temporal SNR were analyzed for in vivo rat brains at 9.4 T in comparison with multislice gradient-echo EPI. Percent signal changes and t-scores are also presented. RESULTS For both mouse brain and human brain imaging, ERASE exhibited a high tolerance to magnetic susceptibility artifacts, showing much lower distortion and signal dropout, especially in the regions involving large magnetic susceptibility effects. For BOLD-fMRI, ERASE provided higher temporal SNR and t-scores than EPI, but exhibited similar percent signal changes in in vivo rat brains at 9.4 T. CONCLUSION When compared with conventional EPI, ERASE is much less sensitive, not only to EPI-related artifacts such as Nyquist ghosting, but also to B0 inhomogeneity including magnetic susceptibility effects. It is promising for use in BOLD-fMRI, providing higher temporal SNR and t-scores with constant TE when compared with EPI, although further optimization is needed for human fMRI.
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Affiliation(s)
- Jae-Kyun Ryu
- Department of Biomedical Engineering, Sungkyunkwan University, Suwon, Republic of Korea.,Center for Neuroscience Imaging Research, Institute for Basic Science, Suwon, Republic of Korea.,Department of Intelligent Precision Healthcare Convergence, Sungkyunkwan University, Suwon, Republic of Korea
| | - Won Beom Jung
- Center for Neuroscience Imaging Research, Institute for Basic Science, Suwon, Republic of Korea
| | - Jaeyong Yu
- Department of Biomedical Engineering, Sungkyunkwan University, Suwon, Republic of Korea.,Department of Intelligent Precision Healthcare Convergence, Sungkyunkwan University, Suwon, Republic of Korea
| | - Jeong Pyo Son
- Center for Neuroscience Imaging Research, Institute for Basic Science, Suwon, Republic of Korea.,Department of Health Sciences and Technology, Samsung Advanced Institute for Health Sciences and Technology, Sungkyunkwan University, Seoul, Republic of Korea
| | - Seung-Kyun Lee
- Department of Biomedical Engineering, Sungkyunkwan University, Suwon, Republic of Korea.,Center for Neuroscience Imaging Research, Institute for Basic Science, Suwon, Republic of Korea.,Department of Intelligent Precision Healthcare Convergence, Sungkyunkwan University, Suwon, Republic of Korea
| | - Seong-Gi Kim
- Department of Biomedical Engineering, Sungkyunkwan University, Suwon, Republic of Korea.,Center for Neuroscience Imaging Research, Institute for Basic Science, Suwon, Republic of Korea.,Department of Intelligent Precision Healthcare Convergence, Sungkyunkwan University, Suwon, Republic of Korea
| | - Jang-Yeon Park
- Department of Biomedical Engineering, Sungkyunkwan University, Suwon, Republic of Korea.,Center for Neuroscience Imaging Research, Institute for Basic Science, Suwon, Republic of Korea.,Department of Intelligent Precision Healthcare Convergence, Sungkyunkwan University, Suwon, Republic of Korea
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16
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Berglund J, van Niekerk A, Rydén H, Sprenger T, Avventi E, Norbeck O, Glimberg SL, Olesen OV, Skare S. Prospective motion correction for diffusion weighted EPI of the brain using an optical markerless tracker. Magn Reson Med 2020; 85:1427-1440. [PMID: 32989859 PMCID: PMC7756594 DOI: 10.1002/mrm.28524] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/12/2020] [Revised: 07/31/2020] [Accepted: 08/28/2020] [Indexed: 01/25/2023]
Abstract
PURPOSE To enable motion-robust diffusion weighted imaging of the brain using well-established imaging techniques. METHODS An optical markerless tracking system was used to estimate and correct for rigid body motion of the head in real time during scanning. The imaging coordinate system was updated before each excitation pulse in a single-shot EPI sequence accelerated by GRAPPA with motion-robust calibration. Full Fourier imaging was used to reduce effects of motion during diffusion encoding. Subjects were imaged while performing prescribed motion patterns, each repeated with prospective motion correction on and off. RESULTS Prospective motion correction with dynamic ghost correction enabled high quality DWI in the presence of fast and continuous motion within a 10° range. Images acquired without motion were not degraded by the prospective correction. Calculated diffusion tensors tolerated the motion well, but ADC values were slightly increased. CONCLUSIONS Prospective correction by markerless optical tracking minimizes patient interaction and appears to be well suited for EPI-based DWI of patient groups unable to remain still including those who are not compliant with markers.
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Affiliation(s)
- Johan Berglund
- Department of Clinical Neuroscience, Karolinska Institutet, Stockholm, Sweden
| | - Adam van Niekerk
- Department of Clinical Neuroscience, Karolinska Institutet, Stockholm, Sweden
| | - Henric Rydén
- Department of Clinical Neuroscience, Karolinska Institutet, Stockholm, Sweden.,Department of Neuroradiology, Karolinska University Hospital, Stockholm, Sweden
| | - Tim Sprenger
- Department of Clinical Neuroscience, Karolinska Institutet, Stockholm, Sweden.,MR Applied Science Laboratory, GE Healthcare, Stockholm, Sweden
| | - Enrico Avventi
- Department of Clinical Neuroscience, Karolinska Institutet, Stockholm, Sweden.,Department of Neuroradiology, Karolinska University Hospital, Stockholm, Sweden
| | - Ola Norbeck
- Department of Clinical Neuroscience, Karolinska Institutet, Stockholm, Sweden.,Department of Neuroradiology, Karolinska University Hospital, Stockholm, Sweden
| | | | | | - Stefan Skare
- Department of Clinical Neuroscience, Karolinska Institutet, Stockholm, Sweden.,Department of Neuroradiology, Karolinska University Hospital, Stockholm, Sweden
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17
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Liu YJ, Lee YH, Chang HC, Chung HW, Wang CW, Juan CH, Chu YH, Lee JC, Juan CJ. Imaging quality of PROPELLER diffusion-weighted MR imaging and its diagnostic performance in distinguishing pleomorphic adenomas from Warthin tumors of the parotid gland. NMR Biomed 2020; 33:e4282. [PMID: 32124504 DOI: 10.1002/nbm.4282] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/11/2019] [Revised: 02/03/2020] [Accepted: 02/04/2020] [Indexed: 06/10/2023]
Abstract
The aim of this study was to evaluate the imaging quality and diagnostic performance of fast spin echo diffusion-weighted imaging with periodically rotated overlapping parallel lines with enhanced reconstruction (FSE-PROP-DWI) in distinguishing parotid pleomorphic adenoma (PMA) from Warthin tumor (WT). This retrospective study enrolled 44 parotid gland tumors from 34 patients, including 15 PMAs and 29 WTs with waived written informed consent. All participants underwent 1.5 T diffusion-weighted imaging including FSE-PROP-DWI and single-shot echo-planar diffusion-weighted imaging (SS-EP-DWI). After imaging resizing and registration among T2WI, FSE-PROP-DWI and SS-EP-DWI, imaging distortion was quantitatively analyzed by using the Dice coefficient. Signal-to-noise ratio and contrast-to-noise ratio were qualitatively evaluated. The mean apparent diffusion coefficient (ADC) of parotid gland tumors was calculated. Wilcoxon signed-rank test was used for paired comparison between FSE-PROP-DWI versus SS-EP-DWI. Mann-Whitney U test was used for independent group comparison between PMAs versus WTs. Diagnostic performance was evaluated by receiver operating characteristics curve analysis. P < 0.05 was considered statistically significant. The Dice coefficient was statistically significantly higher on FSE-PROP-DWI than SS-EP-DWI for both tumors (P < 0.005). Mean ADC was statistically significantly higher in PMAs than WTs on both FSE-PROP-DWI and SS-EP-DWI (P < 0.005). FSE-PROP-DWI and SS-EP-DWI successfully distinguished PMAs from WTs with an AUC of 0.880 and 0.945, respectively (P < 0.05). Sensitivity, specificity, positive predictive value, negative predictive value and accuracy in diagnosing PMAs were 100%, 69.0%, 62.5%, 100% and 79.5% for FSE-PROP-DWI, and 100%, 82.8%, 75%, 100% and 88.6% for SS-EP-DWI, respectively. FSE-PROP-DWI is useful to distinguish parotid PMAs from WTs with less distortion of tumors but lower AUC than SS-EP-DWI.
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Affiliation(s)
- Yi-Jui Liu
- Department of Automatic Control Engineering, Feng Chia University, Taichung, Taiwan, Republic of China
| | - Yi-Hsiung Lee
- Electrical and Communication Engineering, Feng Chia University, Taichung, Taiwan, Republic of China
- Department of Radiology, Tri-Service General Hospital, Taipei, Taiwan, Republic of China
| | - Hing-Chiu Chang
- Department of Diagnostic Radiology, The University of Hong Kong, Hong Kong, China
| | - Hsiao-Wen Chung
- Department of Electrical Engineering, National Taiwan University, Taipei, Taiwan, Republic of China
| | - Chih-Wei Wang
- Department of Radiology, Tri-Service General Hospital, Taipei, Taiwan, Republic of China
| | - Cheng-Hsuan Juan
- Department of Automatic Control Engineering, Feng Chia University, Taichung, Taiwan, Republic of China
| | - Yueng-Hsiang Chu
- Department of Otolaryngology-Head & Neck Surgery, Tri-Service General Hospital, Taipei, Taiwan, Republic of China
| | - Jih-Chin Lee
- Department of Otolaryngology-Head & Neck Surgery, Tri-Service General Hospital, Taipei, Taiwan, Republic of China
| | - Chun-Jung Juan
- Department of Medical Imaging, China Medical University Hsinchu Hospital, Hsinchu, Taiwan, Republic of China
- Department of Radiology, School of Medicine, College of Medicine, China Medical University, Taichung, Taiwan, Republic of China
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18
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Liu X, Hui ES, Chang HC. Elimination of residual aliasing artifact that resembles brain lesion on multi-oblique diffusion-weighted echo-planar imaging with parallel imaging using virtual coil acquisition. J Magn Reson Imaging 2019; 51:1442-1453. [PMID: 31664772 DOI: 10.1002/jmri.26966] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/16/2019] [Accepted: 09/25/2019] [Indexed: 11/07/2022] Open
Abstract
BACKGROUND Single-shot diffusion-weighted echo-planar imaging (ssDW-EPI) acquired with parallel imaging and a multi-oblique scan plane may suffer from residual aliasing artifacts, resembling lesions on the calculated apparent diffusion coefficient (ADC) map. PURPOSE To combine ssDW-EPI and virtual coil acquisition and develop a self-reference reconstruction method to eliminate the residual aliasing artifact on multi-oblique ssDW-EPI sequence with parallel imaging and multiple signal averaging. STUDY TYPE Prospective. SUBJECTS Three healthy subjects and 50 stroke patients. FIELD STRENGTH/SEQUENCE Conventional ssDW-EPI with parallel imaging, and proposed ssDW-EPI with virtual coil acquisition at 1.5T. ASSESSMENT The efficacy of the proposed method was evaluated in 50 stroke patients by comparing the ssDW-EPI with conventional parallel imaging reconstructions. The extent of residual aliasing artifacts were rated on a 5-point Likert scale by three independent raters. Only the data without residual aliasing artifacts on conventional ssDW-EPI were included for the assessment of signal-to-noise ratio (SNR), ghost-to-signal ratio (GSR), and ADC. STATISTICAL TESTS The interobserver agreements for examining residual aliasing artifacts were measured by the intraclass correlation coefficient (ICC). A two-sample t-test was performed for comparing SNR, GSR, and ADC. RESULTS There was a perfect agreement (ICC = 1.00) in the examination of residual aliasing artifacts on images obtained using the proposed method. The incidence rates of the residual aliasing artifact on the ADC maps obtained from the scanner console and proposed method were 60% (ie, 30 out of 50) and 0%, respectively. The proposed method offers significantly lower GSR than conventional parallel imaging reconstruction (P < 0.001). There was no significant difference in SNR (P = 0.20-0.51) and ADC values (P = 0.20-0.94) between conventional parallel imaging reconstructions and the proposed method. DATA CONCLUSION It appears that our method could effectively eliminate artifacts and significantly improve the GSR of b = 0 T2 WI and b > 0 DWI, as well as permit ADC measurement consistent with conventional techniques. Our method may be beneficial to clinical assessment of the brain that utilizes multi-oblique ssDW-EPI. LEVEL OF EVIDENCE 1 Technical Efficacy Stage: 1 J. Magn. Reson. Imaging 2020;51:1442-1453.
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Affiliation(s)
- Xiaoxi Liu
- Department of Diagnostic Radiology, Li Ka Shing Faculty of Medicine, University of Hong Kong, Hong Kong
| | - Edward S Hui
- Department of Diagnostic Radiology, Li Ka Shing Faculty of Medicine, University of Hong Kong, Hong Kong.,State Key Laboratory of Brain and Cognitive Sciences, University of Hong Kong, Hong Kong
| | - Hing-Chiu Chang
- Department of Diagnostic Radiology, Li Ka Shing Faculty of Medicine, University of Hong Kong, Hong Kong
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19
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Haneda J, Hagiwara A, Hori M, Wada A, Fukunaga I, Murata K, Kamagata K, Fujita S, Maekawa T, Irie R, Takamura T, Suzuki M, Kunishima Kumamaru K, Aoki S. A Comparison of Techniques for Correcting Eddy-current and Motion-induced Distortions in Diffusion-weighted Echo-planar Images. Magn Reson Med Sci 2019; 18:272-275. [PMID: 30504640 PMCID: PMC6883088 DOI: 10.2463/mrms.tn.2018-0095] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
The purpose of this study was to show the efficacy of dynamic field correction (DFC), a technique provided by the scanner software, in comparison to the FMRIB Software Library (FSL) post-processing “eddy” tool. DFC requires minimal additional scan time for the correction of eddy-current and motion-induced geometrical image distortions in diffusion-weighted echo-planar images. The fractional anisotropy derived from images corrected with DFC were comparable to images corrected with the “eddy” tool and significantly higher than images without correction, which demonstrates the utility of DFC.
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Affiliation(s)
- Jun Haneda
- Department of Radiology, Koshigaya Municipal Hospital
| | - Akifumi Hagiwara
- Department of Radiology, Juntendo University School of Medicine.,Department of Radiology, Graduate School of Medicine, The University of Tokyo
| | - Masaaki Hori
- Department of Radiology, Juntendo University School of Medicine
| | - Akihiko Wada
- Department of Radiology, Juntendo University School of Medicine
| | - Issei Fukunaga
- Department of Radiology, Juntendo University School of Medicine
| | | | - Koji Kamagata
- Department of Radiology, Juntendo University School of Medicine
| | - Shohei Fujita
- Department of Radiology, Juntendo University School of Medicine.,Department of Radiology, Graduate School of Medicine, The University of Tokyo
| | - Tomoko Maekawa
- Department of Radiology, Juntendo University School of Medicine.,Department of Radiology, Graduate School of Medicine, The University of Tokyo
| | - Ryusuke Irie
- Department of Radiology, Juntendo University School of Medicine.,Department of Radiology, Graduate School of Medicine, The University of Tokyo
| | | | | | | | - Shigeki Aoki
- Department of Radiology, Juntendo University School of Medicine
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20
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Huang W, Liu J, Zhang B, Liang L, Luo X, Mei Y, Zhang S. Potential value of non-echo-planar diffusion-weighted imaging of the nasopharynx: a primary study for differential diagnosis between recurrent nasopharyngeal carcinoma and post-chemoradiation fibrosis. Acta Radiol 2019; 60:1265-1272. [PMID: 30661363 DOI: 10.1177/0284185118822635] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
Affiliation(s)
- Wenhui Huang
- Department of Radiology, Guangdong General Hospital affiliated to South China University of Technology, Guangzhou, Guangdong, PR China
| | - Jing Liu
- Department of Radiology, Guangdong General Hospital affiliated to South China University of Technology, Guangzhou, Guangdong, PR China
- Department of Radiology, Guizhou Medical University Affiliated Hospital, Guizhou, PR China
| | - Bin Zhang
- Medical Imaging Center, the First Affiliated Hospital, Jinan University, Guangzhou, Guangdong, PR China
| | - Long Liang
- Department of Radiology, Guangdong General Hospital affiliated to South China University of Technology, Guangzhou, Guangdong, PR China
| | - Xiaoning Luo
- Department of Radiology, Guangdong General Hospital affiliated to South China University of Technology, Guangzhou, Guangdong, PR China
| | | | - Shuixing Zhang
- Department of Radiology, Guangdong General Hospital affiliated to South China University of Technology, Guangzhou, Guangdong, PR China
- Medical Imaging Center, the First Affiliated Hospital, Jinan University, Guangzhou, Guangdong, PR China
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21
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Viola F, Dyverfeldt P, Carlhäll CJ, Ebbers T. Data Quality and Optimal Background Correction Order of Respiratory-Gated k-Space Segmented Spoiled Gradient Echo (SGRE) and Echo Planar Imaging (EPI)-Based 4D Flow MRI. J Magn Reson Imaging 2019; 51:885-896. [PMID: 31332874 PMCID: PMC7027768 DOI: 10.1002/jmri.26879] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/27/2019] [Revised: 07/10/2019] [Accepted: 07/10/2019] [Indexed: 12/23/2022] Open
Abstract
Background A reduction in scan time of 4D Flow MRI would facilitate clinical application. A recent study indicates that echo‐planar imaging (EPI) 4D Flow MRI allows for a reduction in scan time and better data quality than the recommended k‐space segmented spoiled gradient echo (SGRE) sequence. It was argued that the poor data quality of SGRE was related to the nonrecommended absence of respiratory motion compensation. However, data quality can also be affected by the background offset compensation. Purpose To compare the data quality of respiratory motion‐compensated SGRE and EPI 4D Flow MRI and their dependence on background correction (BC) order. Study Type Retrospective. Subjects Eighteen healthy subjects (eight female, mean age 32 ± 5 years). Field Strength and Sequence 1.5 T. [Correction added on July 26, 2019, after first online publication: The preceding field strength was corrected.] SGRE and EPI‐based 4D Flow MRI. Assessment Data quality was investigated visually and by comparing flows through the cardiac valves and aorta. Measurements were obtained from transvalvular flow and pathline analysis. Statistical Tests Linear regression and Bland–Altman analysis were used. Wilcoxon test was used for comparison of visual scoring. Student's t‐test was used for comparison of flow volumes. Results No significant difference was found by visual inspection (P = 0.08). Left ventricular (LV) flows were strongly and very strongly associated with SGRE and EPI, respectively (R2 = 0.86–0.94 SGRE; 0.71–0.79 EPI, BC0–4). LV and right ventricular (RV) outflows and LV pathline flows were very strongly associated (R2 = 0.93–0.95 SGRE; 0.88–0.91 EPI, R2 = 0.91–0.95 SGRE; 0.91–0.93 EPI, BC1–4). EPI LV outflow was lower than the short‐axis‐based stroke volume. EPI RV outflow and proximal descending aortic flow were lower than SGREs. Data Conclusion Both sequences yielded good internal data consistency when an adequate background correction was applied. Second and first BC order were considered sufficient for transvalvular flow analysis in SGRE and EPI, respectively. Higher BC orders were preferred for particle tracing. Level of Evidence 4 Technical Efficacy Stage 1 J. Magn. Reson. Imaging 2020;51:885–896.
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Affiliation(s)
- Federica Viola
- Division of Cardiovascular Medicine, Department of Medical and Health Sciences, Linköping University, Linköping, Sweden
| | - Petter Dyverfeldt
- Division of Cardiovascular Medicine, Department of Medical and Health Sciences, Linköping University, Linköping, Sweden.,Center for Medical Image Science and Visualization (CMIV), Linköping University, Linköping, Sweden
| | - Carl-Johan Carlhäll
- Division of Cardiovascular Medicine, Department of Medical and Health Sciences, Linköping University, Linköping, Sweden.,Center for Medical Image Science and Visualization (CMIV), Linköping University, Linköping, Sweden.,Department of Clinical Physiology, Department of Medical and Health Sciences, Linköping University, Linköping, Sweden
| | - Tino Ebbers
- Division of Cardiovascular Medicine, Department of Medical and Health Sciences, Linköping University, Linköping, Sweden.,Center for Medical Image Science and Visualization (CMIV), Linköping University, Linköping, Sweden
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22
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Kim LH, Lee EH, Galvez M, Aksoy M, Skare S, O’Halloran R, Edwards MSB, Holdsworth SJ, Yeom KW. Reduced field of view echo-planar imaging diffusion tensor MRI for pediatric spinal tumors. J Neurosurg Spine 2019; 31:607-615. [PMID: 31277060 PMCID: PMC6942637 DOI: 10.3171/2019.4.spine19178] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2019] [Accepted: 04/01/2019] [Indexed: 11/06/2022]
Abstract
OBJECTIVE Spine MRI is a diagnostic modality for evaluating pediatric CNS tumors. Applying diffusion-weighted MRI (DWI) or diffusion tensor imaging (DTI) to the spine poses challenges due to intrinsic spinal anatomy that exacerbates various image-related artifacts, such as signal dropouts or pileups, geometrical distortions, and incomplete fat suppression. The zonal oblique multislice (ZOOM)-echo-planar imaging (EPI) technique reduces geometric distortion and image blurring by reducing the field of view (FOV) without signal aliasing into the FOV. The authors hypothesized that the ZOOM-EPI method for spine DTI in concert with conventional spinal MRI is an efficient method for augmenting the evaluation of pediatric spinal tumors. METHODS Thirty-eight consecutive patients (mean age 8 years) who underwent ZOOM-EPI spine DTI for CNS tumor workup were retrospectively identified. Patients underwent conventional spine MRI and ZOOM-EPI DTI spine MRI. Two blinded radiologists independently reviewed two sets of randomized images: conventional spine MRI without ZOOM-EPI DTI, and conventional spine MRI with ZOOM-EPI DTI. For both image sets, the reviewers scored the findings based on lesion conspicuity and diagnostic confidence using a 5-point Likert scale. The reviewers also recorded presence of tumors. Quantitative apparent diffusion coefficient (ADC) measurements of various spinal tumors were extracted. Tractography was performed in a subset of patients undergoing presurgical evaluation. RESULTS Sixteen patients demonstrated spinal tumor lesions. The readers were in moderate agreement (kappa = 0.61, 95% CI 0.30-0.91). The mean scores for conventional MRI and combined conventional MRI and DTI were as follows, respectively: 3.0 and 4.0 for lesion conspicuity (p = 0.0039), and 2.8 and 3.9 for diagnostic confidence (p < 0.001). ZOOM-EPI DTI identified new lesions in 3 patients. In 3 patients, tractography used for neurosurgical planning showed characteristic fiber tract projections. The mean weighted ADCs of low- and high-grade tumors were 1201 × 10-6 and 865 × 10-6 mm2/sec (p = 0.002), respectively; the mean minimum weighted ADCs were 823 × 10-6 and 474 × 10-6 mm2/sec (p = 0.0003), respectively. CONCLUSIONS Diffusion MRI with ZOOM-EPI can improve the detection of spinal lesions while providing quantitative diffusion information that helps distinguish low- from high-grade tumors. By adding a 2-minute DTI scan, quantitative diffusion information and tract profiles can reliably be obtained and serve as a useful adjunct to presurgical planning for pediatric spinal tumors.
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Affiliation(s)
- Lily H. Kim
- Department of Neurosurgery, Stanford University School of Medicine, Stanford
| | - Edward H. Lee
- Department of Electrical Engineering, Stanford University, Stanford, California
| | - Michelle Galvez
- Department of Radiology, Stanford University School of Medicine, Stanford
| | - Murat Aksoy
- Department of Radiology, Stanford University School of Medicine, Stanford
| | - Stefan Skare
- Clinical Neuroscience, Karolinska Institute, Stockholm, Sweden
| | - Rafael O’Halloran
- Hyperfine Research Inc., Guilford, Connecticut; University of Auckland, New Zealand
| | | | - Samantha J. Holdsworth
- Department of Anatomy and Medical Imaging & Centre for Brain Research, Faculty of Medical and Health Sciences, University of Auckland, New Zealand
| | - Kristen W. Yeom
- Department of Radiology, Stanford University School of Medicine, Stanford
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Yang L, Qiu M, Xia C, Li Z, Wang Z, Zhou X, Wu B. Value of High-Resolution DWI in Combination With Texture Analysis for the Evaluation of Tumor Response After Preoperative Chemoradiotherapy for Locally Advanced Rectal Cancer. AJR Am J Roentgenol 2019; 212:1279-86. [PMID: 30860889 DOI: 10.2214/AJR.18.20689] [Citation(s) in RCA: 16] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
OBJECTIVE. The purpose of this study is to determine the performance of the apparent diffusion coefficient (ADC) value calculated from high-resolution DWI using readout-segmented echo-planar imaging (rs-EPI) and to assess the texture parameters of T2-weighted MR images in identifying pathologic complete response (pCR) after patients with locally advanced rectal cancer (LARC) undergo preoperative chemoradiotherapy (CRT). MATERIALS AND METHODS. A total of 76 patients with LARC who underwent preoperative CRT and subsequent surgery were enrolled in the study retrospectively. All patients underwent post-CRT MRI, which included acquisition of a DWI sequence with use of the rs-EPI technique. The histopathologic tumor regression grade was the reference standard. Patients were subdivided into pCR and non-pCR groups. Two radiologists independently drew whole-tumor ROIs on DW images and T2-weighted MR images to calculate the mean ADC value and first-order texture parameters. RESULTS. Interobserver agreement was good to excellent (intraclass correlation coefficient [ICC], 0.79-0.993) for imaging analysis. Calculated from high-resolution DWI, the mean post-CRT ADC value was significantly higher in the pCR group (p < 0.001). The pCR group also showed lower uniformity (p < 0.001) of the T2-weighted image. The mean ADC value and uniformity were significantly correlated with the tumor regression grade. The mean ADC value was a good indicator for differentiating pCR from absence of pCR (ROC AUC value, 0.912). Uniformity (ROC AUC value, 0.776) showed a moderate ability to identify pCR. Combining the mean ADC value and uniformity yielded an ROC AUC value comparable to that of the mean ADC value (p = 0.125). CONCLUSION. Mean post-CRT ADC values calculated from high-resolution DWI using rs-EPI could effectively select for patients with LARC who have a pCR after preoperative CRT. First-order texture parameters of T2-weighted MR images could also identify patients with pCR by reflecting tumor heterogeneity, even though they could not significantly improve the diagnostic performance.
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24
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Autry AW, Gordon JW, Carvajal L, Mareyam A, Chen HY, Park I, Mammoli D, Vareth M, Chang SM, Wald LL, Xu D, Vigneron DB, Nelson SJ, Li Y. Comparison between 8- and 32-channel phased-array receive coils for in vivo hyperpolarized 13 C imaging of the human brain. Magn Reson Med 2019; 82:833-841. [PMID: 30927300 DOI: 10.1002/mrm.27743] [Citation(s) in RCA: 27] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/18/2018] [Revised: 01/31/2019] [Accepted: 02/27/2019] [Indexed: 01/22/2023]
Abstract
PURPOSE To compare the performance of an 8-channel surface coil/clamshell transmitter and 32-channel head array coil/birdcage transmitter for hyperpolarized 13 C brain metabolic imaging. METHODS To determine the field homogeneity of the radiofrequency transmitters, B1 + mapping was performed on an ethylene glycol head phantom and evaluated by means of the double angle method. Using a 3D echo-planar imaging sequence, coil sensitivity and noise-only phantom data were acquired with the 8- and 32-channel receiver arrays, and compared against data from the birdcage in transceiver mode. Multislice frequency-specific 13 C dynamic echo-planar imaging was performed on a patient with a brain tumor for each hardware configuration following injection of hyperpolarized [1-13 C]pyruvate. Signal-to-noise ratio (SNR) was evaluated from pre-whitened phantom and temporally summed patient data after coil combination based on optimal weights. RESULTS The birdcage transmitter produced more uniform B1 + compared with the clamshell: 0.07 versus 0.12 (fractional error). Phantom experiments conducted with matched lateral housing separation demonstrated 8- versus 32-channel mean transceiver-normalized SNR performance: 0.91 versus 0.97 at the head center; 6.67 versus 2.08 on the sides; 0.66 versus 2.73 at the anterior; and 0.67 versus 3.17 on the posterior aspect. While the 8-channel receiver array showed SNR benefits along lateral aspects, the 32-channel array exhibited greater coverage and a more uniform coil-combined profile. Temporally summed, parameter-normalized patient data showed SNRmean,slice ratios (8-channel/32-channel) ranging 0.5-2.00 from apical to central brain. White matter lactate-to-pyruvate ratios were conserved across hardware: 0.45 ± 0.12 (8-channel) versus 0.43 ± 0.14 (32-channel). CONCLUSION The 8- and 32-channel hardware configurations each have advantages in particular brain anatomy.
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Affiliation(s)
- Adam W Autry
- Department of Radiology and Biomedical Imaging, University of California San Francisco, San Francisco
| | - Jeremy W Gordon
- Department of Radiology and Biomedical Imaging, University of California San Francisco, San Francisco
| | - Lucas Carvajal
- Department of Radiology and Biomedical Imaging, University of California San Francisco, San Francisco
| | - Azma Mareyam
- Athinoula A Martinos Center for Biomedical Imaging, Department of Radiology, Massachusetts General Hospital, Charlestown, Massachusetts
| | - Hsin-Yu Chen
- Department of Radiology and Biomedical Imaging, University of California San Francisco, San Francisco
| | - Ilwoo Park
- Department of Radiology, Chonnam National University Medical School and Hospital, Gwangju, Korea
| | - Daniele Mammoli
- Department of Radiology and Biomedical Imaging, University of California San Francisco, San Francisco
| | - Maryam Vareth
- Department of Radiology and Biomedical Imaging, University of California San Francisco, San Francisco.,Berkeley Institute for Data Science (BIDS), University of California Berkeley, Berkeley
| | - Susan M Chang
- Department of Neurological Surgery, University of California San Francisco, San Francisco, California
| | - Lawrence L Wald
- Athinoula A Martinos Center for Biomedical Imaging, Department of Radiology, Massachusetts General Hospital, Charlestown, Massachusetts.,Harvard Medical School, Boston, Massachusetts.,Harvard-MIT Health Sciences and Technology, MIT, Cambridge, Massachusetts
| | - Duan Xu
- Department of Radiology and Biomedical Imaging, University of California San Francisco, San Francisco
| | - Daniel B Vigneron
- Department of Radiology and Biomedical Imaging, University of California San Francisco, San Francisco
| | - Sarah J Nelson
- Department of Radiology and Biomedical Imaging, University of California San Francisco, San Francisco.,Department of Bioengineering and Therapeutic Science, University of California San Francisco, San Francisco, California
| | - Yan Li
- Department of Radiology and Biomedical Imaging, University of California San Francisco, San Francisco
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25
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van Rijssel MJ, Zijlstra F, Seevinck PR, Luijten PR, Gilhuijs KGA, Klomp DWJ, Pluim JPW. Reducing distortions in echo-planar breast imaging at ultrahigh field with high-resolution off-resonance maps. Magn Reson Med 2019; 82:425-435. [PMID: 30825245 PMCID: PMC6593992 DOI: 10.1002/mrm.27701] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/07/2018] [Accepted: 01/30/2019] [Indexed: 11/11/2022]
Abstract
PURPOSE DWI is a promising modality in breast MRI, but its clinical acceptance is slow. Analysis of DWI is hampered by geometric distortion artifacts, which are caused by off-resonant spins in combination with the low phase-encoding bandwidth of the EPI sequence used. Existing correction methods assume smooth off-resonance fields, which we show to be invalid in the human breast, where high discontinuities arise at tissue interfaces. METHODS We developed a distortion correction method that incorporates high-resolution off-resonance maps to better solve for severe distortions at tissue interfaces. The method was evaluated quantitatively both ex vivo in a porcine tissue phantom and in vivo in 5 healthy volunteers. The added value of high-resolution off-resonance maps was tested using a Wilcoxon signed rank test comparing the quantitative results obtained with a low-resolution off-resonance map with those obtained with a high-resolution map. RESULTS Distortion correction using low-resolution off-resonance maps corrected most of the distortions, as expected. Still, all quantitative comparison metrics showed increased conformity between the corrected EPI images and a high-bandwidth reference scan for both the ex vivo and in vivo experiments. All metrics showed a significant improvement when a high-resolution off-resonance map was used (P < 0.05), in particular at tissue boundaries. CONCLUSION The use of off-resonance maps of a resolution higher than EPI scans significantly improves upon existing distortion correction techniques, specifically by superior correction at glandular tissue boundaries.
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Affiliation(s)
| | - Frank Zijlstra
- Center for Image Sciences, UMC Utrecht, Utrecht, The Netherlands
| | - Peter R Seevinck
- Center for Image Sciences, UMC Utrecht, Utrecht, The Netherlands
| | - Peter R Luijten
- Center for Image Sciences, UMC Utrecht, Utrecht, The Netherlands
| | | | - Dennis W J Klomp
- Center for Image Sciences, UMC Utrecht, Utrecht, The Netherlands
| | - Josien P W Pluim
- Center for Image Sciences, UMC Utrecht, Utrecht, The Netherlands.,Department of Biomedical Engineering, Technische Universiteit Eindhoven, Eindhoven, The Netherlands
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26
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Tyagi N, Cloutier M, Zakian K, Deasy JO, Hunt M, Rimner A. Diffusion-weighted MRI of the lung at 3T evaluated using echo-planar-based and single-shot turbo spin-echo-based acquisition techniques for radiotherapy applications. J Appl Clin Med Phys 2018; 20:284-292. [PMID: 30421496 PMCID: PMC6333125 DOI: 10.1002/acm2.12493] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/29/2017] [Revised: 10/16/2018] [Accepted: 10/17/2018] [Indexed: 01/14/2023] Open
Abstract
Purpose To compare single‐shot echo‐planar (SS‐EPI)‐based and turbo spin‐echo (SS‐TSE)‐based diffusion‐weighted imaging (DWI) in Non‐Small Cell Lung Cancer (NSCLC) patients and to characterize the distributions of apparent diffusion coefficient (ADC) values generated by the two techniques. Methods Ten NSCLC patients were enrolled in a prospective IRB‐approved study to compare and optimize DWI using EPI and TSE‐based techniques for radiotherapy planning. The imaging protocol included axial T2w, EPI‐based DWI and TSE‐based DWI on a 3 T Philips scanner. Both EPI‐based and TSE‐based DWI sequences used three b values (0, 400, and 800 s/mm2). The acquisition times for EPI‐based and TSE‐based DWI were 5 and 8 min, respectively. DW‐MR images were manually coregistered with axial T2w images, and tumor volume contoured on T2w images were mapped onto the DWI scans. A pixel‐by‐pixel fit of tumor ADC was calculated based on monoexponential signal behavior. Tumor ADC mean, standard deviation, kurtosis, and skewness were calculated and compared between EPI and TSE‐based DWI. Image distortion and ADC values between the two techniques were also quantified using fieldmap analysis and a NIST traceable ice‐water diffusion phantom, respectively. Results The mean ADC for EPI and TSE‐based DWI were 1.282 ± 0.42 × 10−3 and 1.211 ± 0.31 × 10−3 mm2/s. The average skewness and kurtosis were 0.14 ± 0.4 and 2.43 ± 0.40 for DWI‐EPI and −0.06 ± 0.69 and 2.89 ± 0.62 for DWI‐TSE. Fieldmap analysis showed a mean distortion of 13.72 ± 8.12 mm for GTV for DWI‐EPI and 0.61 ± 0.4 mm for DWI‐TSE. ADC values obtained using the diffusion phantom for the two techniques were within 0.03 × 10−3 mm2/s with respect to each other as well as the established values. Conclusions Diffusion‐weighted turbo spin‐echo shows better geometrical accuracy compared to DWI‐EPI. Mean ADC values were similar with both acquisitions but the shape of the histograms was different based on the skewness and kurtosis values. The impact of differences in respiratory technique on ADC values requires further investigation.
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Affiliation(s)
- Neelam Tyagi
- Department of Medical Physics, Memorial Sloan Kettering Cancer Center, New York, NY, USA
| | - Michelle Cloutier
- Department of Medical Physics, Memorial Sloan Kettering Cancer Center, New York, NY, USA
| | - Kristen Zakian
- Department of Medical Physics, Memorial Sloan Kettering Cancer Center, New York, NY, USA
| | - Joseph O Deasy
- Department of Medical Physics, Memorial Sloan Kettering Cancer Center, New York, NY, USA
| | - Margie Hunt
- Department of Medical Physics, Memorial Sloan Kettering Cancer Center, New York, NY, USA
| | - Andreas Rimner
- Department of Radiation Oncology, Memorial Sloan Kettering Cancer Center, New York, NY, USA
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27
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Lobos RA, Kim TH, Hoge WS, Haldar JP. Navigator-Free EPI Ghost Correction With Structured Low-Rank Matrix Models: New Theory and Methods. IEEE Trans Med Imaging 2018; 37:2390-2402. [PMID: 29993978 PMCID: PMC6309699 DOI: 10.1109/tmi.2018.2822053] [Citation(s) in RCA: 20] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/16/2023]
Abstract
Structured low-rank matrix models have previously been introduced to enable calibrationless MR image reconstruction from sub-Nyquist data, and such ideas have recently been extended to enable navigator-free echo-planar imaging (EPI) ghost correction. This paper presents a novel theoretical analysis which shows that, because of uniform subsampling, the structured low-rank matrix optimization problems for EPI data will always have either undesirable or non-unique solutions in the absence of additional constraints. This theory leads us to recommend and investigate problem formulations for navigator-free EPI that incorporate side information from either image-domain or k-space domain parallel imaging methods. The importance of using nonconvex low-rank matrix regularization is also identified. We demonstrate using phantom and in vivo data that the proposed methods are able to eliminate ghost artifacts for several navigator-free EPI acquisition schemes, obtaining better performance in comparison with the state-of-the-art methods across a range of different scenarios. Results are shown for both single-channel acquisition and highly accelerated multi-channel acquisition.
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28
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Dong Z, Wang F, Reese TG, Manhard MK, Bilgic B, Wald LL, Guo H, Setsompop K. Tilted-CAIPI for highly accelerated distortion-free EPI with point spread function (PSF) encoding. Magn Reson Med 2018; 81:377-392. [PMID: 30229562 DOI: 10.1002/mrm.27413] [Citation(s) in RCA: 32] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/21/2018] [Revised: 05/31/2018] [Accepted: 05/31/2018] [Indexed: 12/14/2022]
Abstract
PURPOSE To develop a method for fast distortion- and blurring-free imaging. THEORY EPI with point-spread-function (PSF) mapping can achieve distortion- and blurring-free imaging at a cost of long acquisition time. In this study, an acquisition/reconstruction technique, termed "tilted-CAIPI," is proposed to achieve >20× acceleration for PSF-EPI. The proposed method systematically optimized the k-space sampling trajectory with B0 -inhomogeneity-informed reconstruction, to exploit the inherent signal correlation in PSF-EPI and take full advantage of coil sensitivity. Susceptibility-induced phase accumulation is regarded as an additional encoding that is estimated by calibration data and integrated into reconstruction. Self-navigated phase correction was developed to correct shot-to-shot phase variation in diffusion imaging. METHODS Tilted-CAIPI was implemented at 3T, with incorporation of partial Fourier and simultaneous multislice to achieve further accelerations. T2 -weighted, T2 * -weighted, and diffusion-weighted imaging experiments were conducted to evaluate the proposed method. RESULTS The ability of tilted-CAIPI to provide highly accelerated imaging without distortion and blurring was demonstrated through in vivo brain experiments, where only 8 shots per simultaneous slice group were required to provide high-quality, high-SNR imaging at 0.8-1 mm resolution. CONCLUSION Tilted-CAIPI achieved fast distortion- and blurring-free imaging with high SNR. Whole-brain T2 -weighted, T2 * -weighted, and diffusion imaging can be obtained in just 15-60 s.
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Affiliation(s)
- Zijing Dong
- Center for Biomedical Imaging Research, Department of Biomedical Engineering, Tsinghua University, Beijing, China
| | - Fuyixue Wang
- A. A. Martinos Center for Biomedical Imaging, Department of Radiology, Massachusetts General Hospital, Charlestown, Massachusetts.,Harvard-MIT Health Sciences and Technology, MIT, Cambridge, Massachusetts
| | - Timothy G Reese
- A. A. Martinos Center for Biomedical Imaging, Department of Radiology, Massachusetts General Hospital, Charlestown, Massachusetts
| | - Mary Katherine Manhard
- A. A. Martinos Center for Biomedical Imaging, Department of Radiology, Massachusetts General Hospital, Charlestown, Massachusetts
| | - Berkin Bilgic
- A. A. Martinos Center for Biomedical Imaging, Department of Radiology, Massachusetts General Hospital, Charlestown, Massachusetts
| | - Lawrence L Wald
- A. A. Martinos Center for Biomedical Imaging, Department of Radiology, Massachusetts General Hospital, Charlestown, Massachusetts.,Harvard-MIT Health Sciences and Technology, MIT, Cambridge, Massachusetts
| | - Hua Guo
- Center for Biomedical Imaging Research, Department of Biomedical Engineering, Tsinghua University, Beijing, China
| | - Kawin Setsompop
- A. A. Martinos Center for Biomedical Imaging, Department of Radiology, Massachusetts General Hospital, Charlestown, Massachusetts.,Harvard-MIT Health Sciences and Technology, MIT, Cambridge, Massachusetts
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29
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Abstract
Nyquist ghosts are a longstanding problem in a variety of fast MRI experiments that use echo-planar imaging (EPI). Recently, several structured low-rank matrix modeling approaches have been proposed that achieve state-of-the-art ghost-elimination, although the performance of these approaches is still inadequate in several important scenarios. We present a new structured low-rank matrix recovery ghost correction method that we call Robust Autocalibrated LORAKS (RAC-LORAKS). RAC-LORAKS incorporates constraints from autocalibration data to avoid ill-posedness, but allows adaptation of these constraints to gain robustness against possible autocalibration imperfections. RAC-LORAKS is tested in two challenging scenarios: highly-undersampled multi-channel EPI of the brain, and cardiac EPI with a double-oblique slice orientation. Results show that RAC-LORAKS can provide substantial improvements over existing ghost correction methods, and potentially enables new imaging applications that were previously confounded by ghost artifacts.
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Affiliation(s)
- Rodrigo A Lobos
- Signal and Image Processing Institute, University of Southern California, Los Angeles, CA 90089
| | - Ahsan Javed
- Signal and Image Processing Institute, University of Southern California, Los Angeles, CA 90089
| | - Krishna S Nayak
- Signal and Image Processing Institute, University of Southern California, Los Angeles, CA 90089
| | - W Scott Hoge
- Radiology, Brigham and Women's Hospital and Harvard Medical School, Boston, MA 02115
| | - Justin P Haldar
- Signal and Image Processing Institute, University of Southern California, Los Angeles, CA 90089
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Jonathan SV, Grissom WA. Volumetric MRI thermometry using a three-dimensional stack-of-stars echo-planar imaging pulse sequence. Magn Reson Med 2018; 79:2003-2013. [PMID: 28782129 PMCID: PMC5803468 DOI: 10.1002/mrm.26862] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/17/2017] [Revised: 07/13/2017] [Accepted: 07/15/2017] [Indexed: 12/25/2022]
Abstract
PURPOSE To measure temperature over a large brain volume with fine spatiotemporal resolution. METHODS A three-dimensional stack-of-stars echo-planar imaging sequence combining echo-planar imaging and radial sampling with golden angle spacing was implemented at 3T for proton resonance frequency-shift temperature imaging. The sequence acquires a 188x188x43 image matrix with 1.5x1.5x2.75 mm3 spatial resolution. Temperature maps were reconstructed using sensitivity encoding (SENSE) image reconstruction followed by the image domain hybrid method, and using the k-space hybrid method. In vivo temperature maps were acquired without heating to measure temperature precision in the brain, and in a phantom during high-intensity focused ultrasound sonication. RESULTS In vivo temperature standard deviation was less than 1°C at dynamic scan times down to 0.75 s. For a given frame rate, scanning at a minimum repetition time (TR) with minimum acceleration yielded the lowest standard deviation. With frame rates around 3 s, the scan was tolerant to a small number of receive coils, and temperature standard deviation was 48% higher than a standard two-dimensional Fourier transform temperature mapping scan, but provided whole-brain coverage. Phantom temperature maps with no visible aliasing were produced for dynamic scan times as short as 0.38 s. k-Space hybrid reconstructions were more tolerant to acceleration. CONCLUSION Three-dimensional stack-of-stars echo-planar imaging temperature mapping provides volumetric brain coverage and fine spatiotemporal resolution. Magn Reson Med 79:2003-2013, 2018. © 2017 International Society for Magnetic Resonance in Medicine.
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Affiliation(s)
- Sumeeth V. Jonathan
- Vanderbilt University Institute of Imaging Science, Nashville, TN, United States
- Department of Biomedical Engineering, Vanderbilt University, Nashville, TN, United States
| | - William A. Grissom
- Vanderbilt University Institute of Imaging Science, Nashville, TN, United States
- Department of Biomedical Engineering, Vanderbilt University, Nashville, TN, United States
- Department of Radiology, Vanderbilt University, Nashville, TN, United States
- Department of Electrical Engineering, Vanderbilt University, Nashville, TN, United States
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Kim TH, Baek MY, Park JE, Ryu YJ, Cheon JE, Kim IO, Choi YH. Comparison of DWI Methods in the Pediatric Brain: PROPELLER Turbo Spin-Echo Imaging Versus Readout-Segmented Echo-Planar Imaging Versus Single-Shot Echo-Planar Imaging. AJR Am J Roentgenol 2018; 210:1352-8. [PMID: 29570373 DOI: 10.2214/AJR.17.18796] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
OBJECTIVE The purpose of this study is to compare DWI for pediatric brain evaluation using single-shot echo-planar imaging (EPI), periodically rotated overlapping parallel lines with enhanced reconstruction (Blade), and readout-segmented EPI (Resolve). MATERIALS AND METHODS Blade, Resolve, and single-shot EPI were performed for 27 pediatric patients (median age, 9 years), and three datasets were independently reviewed by two radiologists. Qualitative analyses were performed for perceptive coarseness, image distortion, susceptibility-related changes, motion artifacts, and lesion conspicuity using a 5-point Likert scale. Quantitative analyses were conducted for spatial distortion and signal uniformity of each sequence. RESULTS Mean scores were 2.13, 3.17, and 3.76 for perceptive coarseness; 4.85, 3.96, and 2.19 for image distortion; 4.76, 3.96, and 2.30 for susceptibility-related change; 4.96, 3.83, and 4.69 for motion artifacts; and 2.71, 3.75, and 1.92 for lesion conspicuity, for Blade, Resolve, and single-shot EPI, respectively. Blade and Resolve showed better quality than did single-shot EPI for image distortion, susceptibility-related changes, and lesion conspicuity. Blade showed less image distortion, fewer susceptibility-related changes, and fewer motion artifacts than did Resolve, whereas lesion conspicuity was better with Resolve. Blade showed increased signal variation compared with Resolve and single-shot EPI (coefficients of variation were 0.10, 0.08, and 0.05 for lateral ventricle; 0.13, 0.09, and 0.05 for centrum semiovale; and 0.16, 0.09, and 0.06 for pons in Blade, Resolve, and single-shot EPI, respectively). CONCLUSION DWI with Resolve or Blade yields better quality regarding distortion, susceptibility-related changes, and lesion conspicuity, compared with single-shot EPI. Blade is less susceptible to motion artifacts than is Resolve, whereas Resolve yields less noise and better lesion conspicuity than does Blade.
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Liu YJ, Lee YH, Chang HC, Chiu HC, Chiu TW, Hsu K, Pen CM, Hsu HH, Juan CJ. Proton change of parotid glands after gustatory stimulation examined by magnetic resonance imaging. NMR Biomed 2018; 31:e3885. [PMID: 29315960 DOI: 10.1002/nbm.3885] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/27/2017] [Revised: 11/21/2017] [Accepted: 11/22/2017] [Indexed: 06/07/2023]
Abstract
The aim of this study was to investigate proton changes of the parotid gland after gustatory stimulation by semi-quantitative parameters and an empirical mathematical model (EMM) using high-temporal-resolution, double-echo, echo-planar imaging (EPI). Approved by a local institutional review board, this study examined 20 parotid glands from 10 healthy volunteers (male:female = 6: 4; age ± standard deviation =35.1 ± 14.1 years) with written informed consent obtained. All participants underwent 1.5-T, double-echo EPI with gustatory stimulation. Semi-quantitative parameters, including maximal drop ratio (MDR), time to peak (TTP), drop slope (DS), recovery slope (RS) and recovery ratio (RR), were calculated. The effect of temporal resolution on parotid functional parameters was evaluated. An EMM comprising an output function ( Sot=Aoe-kot+B) and an input function ( Sint=Ain1-e-kint) was also applied to fit all dynamic curves. Kruskal-Wallis test, Wilcoxon test, linear regression analysis and goodness of fit were used for statistical analysis. p < 0.05 was considered to be statistically significant. The signal intensity dropped significantly after gustatory stimulation on the proton density (PD) image (p < 0.01). MDR was 8.26% in the PD image. MDR and RR were negatively associated with time interval, whereas DS and TTP were significantly positively associated with time interval (all p < 0.05). EMM parametric values derived from PD-time curves of parotid glands were 12.04 ± 6.81%, 6.43 ± 4.23 min-1 , 88.73 ± 6.18%, 8.41 ± 4.86 min-1 and 1.09 ± 1.35 for Ao , ko , B, Ain and kin , respectively. Semi-quantitative functional parameters and EMM parameters using high-temporal-resolution, double-echo EPI allow the quantification of parotid proton changes after gustatory stimulation.
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Affiliation(s)
- Yi-Jui Liu
- Department of Automatic Control Engineering, Feng Chia University, Taichung, Taiwan, Republic of China
| | - Yi-Hsiung Lee
- PhD Program in Electrical and Communication Engineering, Feng Chia University, Taichung, Taiwan, Republic of China
- Department of Radiology, Tri-Service General Hospital, Taipei, Taiwan, Republic of China
| | - Hing-Chiu Chang
- Department of Diagnostic Radiology, The University of Hong Kong, Hong Kong, China
| | - Hui-Chu Chiu
- PhD Program of Technology Management, Chung Hua University, Hsinchu, Taiwan, Republic of China
| | - Ta-Wei Chiu
- Department of Medicine, Taipei Medical University, Taipei, Taiwan, Republic of China
| | - Kang Hsu
- Department of Dentistry, National Defense Medical Center, Taipei, Taiwan, Republic of China
| | - Cheng-Ming Pen
- PhD Program in Electrical and Communication Engineering, Feng Chia University, Taichung, Taiwan, Republic of China
- Da Vinci Minimally Invasive Surgery Center, Chung Shan Medical University Hospital, Taichung, Taiwan, Republic of China
| | - Hsian-He Hsu
- Department of Radiology, Tri-Service General Hospital, Taipei, Taiwan, Republic of China
- Department of Radiology, National Defense Medical Center, Taipei, Taiwan, Republic of China
| | - Chun-Jung Juan
- Department of Radiology, Tri-Service General Hospital, Taipei, Taiwan, Republic of China
- Department of Radiology, National Defense Medical Center, Taipei, Taiwan, Republic of China
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Abstract
Object: Brain mapping has entered a new era focusing on complex network connectivity. Central to this is the search for the connectome or the brains ‘wiring diagram’. Graph theory analysis of the connectome allows understanding of the importance of regions to network function, and the consequences of their impairment or excision. Our goal was to apply connectome analysis in patients with brain tumours to characterise overall network topology and individual patterns of connectivity alterations. Methods: Resting-state functional MRI data were acquired using multi-echo, echo planar imaging pre-operatively from five participants each with a right temporal–parietal–occipital glioblastoma. Complex networks analysis was initiated by parcellating the brain into anatomically regions amongst which connections were identified by retaining the most significant correlations between the respective wavelet decomposed time-series. Results: Key characteristics of complex networks described in healthy controls were preserved in these patients, including ubiquitous small world organization. An exponentially truncated power law fit to the degree distribution predicted findings of general network robustness to injury but with a core of hubs exhibiting disproportionate vulnerability. Tumours produced a consistent reduction in local and long-range connectivity with distinct patterns of connection loss depending on lesion location. Conclusions: Connectome analysis is a feasible and novel approach to brain mapping in individual patients with brain tumours. Applications to pre-surgical planning include identifying regions critical to network function that should be preserved and visualising connections at risk from tumour resection. In the future one could use such data to model functional plasticity and recovery of cognitive deficits.
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Affiliation(s)
- Michael G Hart
- a Brain Mapping Unit, Department of Psychiatry , University of Cambridge, Sir William Hardy Building , Cambridge , UK ;,b Division of Neurosurgery, Department of Clinical Neurosciences , Cambridge Biomedical Campus , Cambridge , UK
| | - Stephen J Price
- b Division of Neurosurgery, Department of Clinical Neurosciences , Cambridge Biomedical Campus , Cambridge , UK
| | - John Suckling
- c Brain Mapping Unit, Department of Psychiatry, University of Cambridge, Herchel Smith Building for Brain and Mind Sciences , Cambridge , UK
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Bianciardi M, Toschi N, Polimeni JR, Evans KC, Bhat H, Keil B, Rosen BR, Boas DA, Wald LL. The pulsatility volume index: an indicator of cerebrovascular compliance based on fast magnetic resonance imaging of cardiac and respiratory pulsatility. Philos Trans A Math Phys Eng Sci 2016; 374:rsta.2015.0184. [PMID: 27044992 PMCID: PMC4822444 DOI: 10.1098/rsta.2015.0184] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Accepted: 10/26/2015] [Indexed: 05/03/2023]
Abstract
The influence of cardiac activity on the viscoelastic properties of intracranial tissue is one of the mechanisms through which brain-heart interactions take place, and is implicated in cerebrovascular disease. Cerebrovascular disease risk is not fully explained by current risk factors, including arterial compliance. Cerebrovascular compliance is currently estimated indirectly through Doppler sonography and magnetic resonance imaging (MRI) measures of blood velocity changes. In order to meet the need for novel cerebrovascular disease risk factors, we aimed to design and validate an MRI indicator of cerebrovascular compliance based on direct endogenous measures of blood volume changes. We implemented a fast non-gated two-dimensional MRI pulse sequence based on echo-planar imaging (EPI) with ultra-short repetition time (approx. 30-50 ms), which stepped through slices every approximately 20 s. We constrained the solution of the Bloch equations for spins moving faster than a critical speed to produce an endogenous contrast primarily dependent on spin volume changes, and an approximately sixfold signal gain compared with Ernst angle acquisitions achieved by the use of a 90° flip angle. Using cardiac and respiratory peaks detected on physiological recordings, average cardiac and respiratory MRI pulse waveforms in several brain compartments were obtained at 7 Tesla, and used to derive a compliance indicator, the pulsatility volume index (pVI). The pVI, evaluated in larger cerebral arteries, displayed significant variation within and across vessels. Multi-echo EPI showed the presence of significant pulsatility effects in both S0 and [Formula: see text] signals, compatible with blood volume changes. Lastly, the pVI dynamically varied during breath-holding compared with normal breathing, as expected for a compliance indicator. In summary, we characterized and performed an initial validation of a novel MRI indicator of cerebrovascular compliance, which might prove useful to investigate brain-heart interactions in cerebrovascular disease and other disorders.
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Affiliation(s)
- Marta Bianciardi
- Department of Radiology, Athinoula A. Martinos Center for Biomedical Imaging, Massachusetts General Hospital and Harvard Medical School, Building 149, 13th Street, Charlestown, Boston, MA 02129, USA
| | - Nicola Toschi
- Department of Radiology, Athinoula A. Martinos Center for Biomedical Imaging, Massachusetts General Hospital and Harvard Medical School, Building 149, 13th Street, Charlestown, Boston, MA 02129, USA Medical Physics Section, Department of Biomedicine and Prevention, Faculty of Medicine, University of Rome 'Tor Vergata', Via Montpellier 1, 00133 Rome, Italy
| | - Jonathan R Polimeni
- Department of Radiology, Athinoula A. Martinos Center for Biomedical Imaging, Massachusetts General Hospital and Harvard Medical School, Building 149, 13th Street, Charlestown, Boston, MA 02129, USA
| | - Karleyton C Evans
- Department of Psychiatry, Athinoula A. Martinos Center for Biomedical Imaging, Massachusetts General Hospital and Harvard Medical School, Building 149, 13th Street, Charlestown, Boston, MA 02129, USA
| | - Himanshu Bhat
- Siemens Healthcare, Building 149, 13th Street, Charlestown, Boston, MA 02129, USA
| | - Boris Keil
- Department of Radiology, Athinoula A. Martinos Center for Biomedical Imaging, Massachusetts General Hospital and Harvard Medical School, Building 149, 13th Street, Charlestown, Boston, MA 02129, USA Institute for Medical Physics and Radiation Protection, Life Science Engineering, Mittelhessen University of Applied Science, Wiesenstrasse 14, 35390 Giessen, Germany
| | - Bruce R Rosen
- Department of Radiology, Athinoula A. Martinos Center for Biomedical Imaging, Massachusetts General Hospital and Harvard Medical School, Building 149, 13th Street, Charlestown, Boston, MA 02129, USA
| | - David A Boas
- Department of Radiology, Athinoula A. Martinos Center for Biomedical Imaging, Massachusetts General Hospital and Harvard Medical School, Building 149, 13th Street, Charlestown, Boston, MA 02129, USA
| | - Lawrence L Wald
- Department of Radiology, Athinoula A. Martinos Center for Biomedical Imaging, Massachusetts General Hospital and Harvard Medical School, Building 149, 13th Street, Charlestown, Boston, MA 02129, USA
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Zhang Z, Seginer A, Frydman L. Single-scan MRI with exceptional resilience to field heterogeneities. Magn Reson Med 2016; 77:623-634. [PMID: 26901840 DOI: 10.1002/mrm.26145] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/14/2015] [Revised: 12/15/2015] [Accepted: 01/07/2016] [Indexed: 01/01/2023]
Abstract
PURPOSE Single-scan two-dimensional MRI has been generally constrained to acquisitions in high quality magnets. This study introduces a methodology, cross-term spatiotemporal encoding (xSPEN), that delivers such images under much poorer external field conditions. METHODS xSPEN departs from conventional k-space scanning, by relying on spatiotemporally encoding the image being sought. Unlike hitherto proposed SPEN methods, however, xSPEN's image readout does not take place using a field gradient along the direction being probed, but rather with the aid of an ancillary source of inhomogeneous frequency broadening. This ancillary dimension was here imposed by an orthogonal field gradient; for example, images along the "y" axis were read out by application of a "z" gradient. The principles and characteristics of this new approach, compatible with existing scanners and free from the need to collect auxiliary information such as field maps, are presented and discussed. RESULTS Single- and multi-slice in vitro, ex vivo, and in vivo MRI experiments, confirmed the unusual resilience of this new single-shot MRI method to multiple chemical sites on phantoms, animals and humans. CONCLUSION xSPEN can deliver single-scan MRI with good sensitivity and exceptional resilience to field inhomogeneities. This could enable investigations that have hitherto escaped from MRI's scope. Magn Reson Med 77:623-634, 2017. © 2016 International Society for Magnetic Resonance in Medicine.
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Affiliation(s)
- Zhiyong Zhang
- Department of Chemical Physics, Weizmann Institute of Science, Rehovot, Israel
- Department of Electronic Science, Fujian Provincial Key Laboratory of Plasma and Magnetic Resonance, Xiamen University, Xiamen, Fujian, China
| | - Amir Seginer
- Department of Chemical Physics, Weizmann Institute of Science, Rehovot, Israel
| | - Lucio Frydman
- Department of Chemical Physics, Weizmann Institute of Science, Rehovot, Israel
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Lee J, Jin KH, Ye JC. Reference-free single-pass EPI Nyquist ghost correction using annihilating filter-based low rank Hankel matrix (ALOHA). Magn Reson Med 2016; 76:1775-1789. [PMID: 26887895 DOI: 10.1002/mrm.26077] [Citation(s) in RCA: 45] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/06/2015] [Revised: 10/20/2015] [Accepted: 11/13/2015] [Indexed: 11/09/2022]
Abstract
PURPOSE MR measurements from an echo-planar imaging (EPI) sequence produce Nyquist ghost artifacts that originate from inconsistencies between odd and even echoes. Several reconstruction algorithms have been proposed to reduce such artifacts, but most of these methods require either additional reference scans or multipass EPI acquisition. This article proposes a novel and accurate single-pass EPI ghost artifact correction method that does not require any additional reference data. THEORY AND METHODS After converting a ghost correction problem into separate k-space data interpolation problems for even and odd phase encoding, our algorithm exploits an observation that the differential k-space data between the even and odd echoes is a Fourier transform of an underlying sparse image. Accordingly, we can construct a rank-deficient Hankel structured matrix, whose missing data can be recovered using an annihilating filter-based low rank Hankel structured matrix completion approach. RESULTS The proposed method was applied to EPI data for both single and multicoil acquisitions. Experimental results using in vivo data confirmed that the proposed method can completely remove ghost artifacts successfully without prescan echoes. CONCLUSION Owing to the discovery of the annihilating filter relationship from the intrinsic EPI image property, the proposed method successfully suppresses ghost artifacts without a prescan step. Magn Reson Med 76:1775-1789, 2016. © 2016 International Society for Magnetic Resonance in Medicine.
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Affiliation(s)
- Juyoung Lee
- Bio-Imaging & Signal Processing Laboratory, Department of Bio and Brain Engineering, Korea Advanced Institute of Science & Technology (KAIST) 291 Daehak-ro, Yuseong-gu, Daejon, 34141, Republic of Korea
| | - Kyong Hwan Jin
- Bio-Imaging & Signal Processing Laboratory, Department of Bio and Brain Engineering, Korea Advanced Institute of Science & Technology (KAIST) 291 Daehak-ro, Yuseong-gu, Daejon, 34141, Republic of Korea
| | - Jong Chul Ye
- Bio-Imaging & Signal Processing Laboratory, Department of Bio and Brain Engineering, Korea Advanced Institute of Science & Technology (KAIST) 291 Daehak-ro, Yuseong-gu, Daejon, 34141, Republic of Korea
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Geraghty BJ, Lau JYC, Chen AP, Cunningham CH. Accelerated 3D echo-planar imaging with compressed sensing for time-resolved hyperpolarized 13 C studies. Magn Reson Med 2016; 77:538-546. [PMID: 26806525 DOI: 10.1002/mrm.26125] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/21/2015] [Revised: 11/20/2015] [Accepted: 12/18/2015] [Indexed: 01/13/2023]
Abstract
PURPOSE To enable large field-of-view, time-resolved volumetric coverage in hyperpolarized 13 C metabolic imaging by implementing a novel data acquisition and image reconstruction method based on the compressed sensing framework. METHODS A spectral-spatial pulse for single-resonance excitation followed by a symmetric echo-planar imaging (EPI) readout was implemented for encoding a 72 × 18 cm2 field of view at 5 × 5 mm2 resolution. Random undersampling was achieved with blipped z-gradients during the ramp portion of the echo-planar imaging readout. The sequence and reconstruction were tested with phantom studies and consecutive in vivo hyperpolarized 13 C scans in rats. Retrospectively and prospectively undersampled data were compared on the basis of structural similarity in the reconstructed images and the quantification of the lactate-to-pyruvate ratio in rat kidneys. RESULTS No artifacts or loss of resolution are evident in the compressed sensing reconstructed images acquired with the proposed sequence. Structural similarity analysis indicate that compressed sensing reconstructions can accurately recover spatial features in the metabolic images evaluated. CONCLUSION A novel z-blip acquisition sequence for compressed sensing accelerated hyperpolarized 13 C 3D echo-planar imaging was developed and demonstrated. The close agreement in lactate-to-pyruvate ratios from both retrospectively and prospectively undersampled data from rats shows that metabolic information is preserved with acceleration factors up to 3-fold with the developed method. Magn Reson Med 77:538-546, 2017. © 2016 International Society for Magnetic Resonance in Medicine.
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Affiliation(s)
- Benjamin J Geraghty
- Department of Medical Biophysics, University of Toronto, Toronto, Ontario, Canada.,Physical Sciences, Sunnybrook Research Institute, Toronto, Ontario, Canada
| | - Justin Y C Lau
- Department of Medical Biophysics, University of Toronto, Toronto, Ontario, Canada.,Physical Sciences, Sunnybrook Research Institute, Toronto, Ontario, Canada
| | | | - Charles H Cunningham
- Department of Medical Biophysics, University of Toronto, Toronto, Ontario, Canada.,Physical Sciences, Sunnybrook Research Institute, Toronto, Ontario, Canada
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Guhaniyogi S, Chu ML, Chang HC, Song AW, Chen NK. Motion immune diffusion imaging using augmented MUSE for high-resolution multi-shot EPI. Magn Reson Med 2015; 75:639-52. [PMID: 25762216 DOI: 10.1002/mrm.25624] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2014] [Revised: 12/08/2014] [Accepted: 12/31/2014] [Indexed: 11/08/2022]
Abstract
PURPOSE To develop new techniques for reducing the effects of microscopic and macroscopic patient motion in diffusion imaging acquired with high-resolution multishot echo-planar imaging. THEORY The previously reported multiplexed sensitivity encoding (MUSE) algorithm is extended to account for macroscopic pixel misregistrations, as well as motion-induced phase errors in a technique called augmented MUSE (AMUSE). Furthermore, to obtain more accurate quantitative diffusion-tensor imaging measures in the presence of subject motion, we also account for the altered diffusion encoding among shots arising from macroscopic motion. METHODS MUSE and AMUSE were evaluated on simulated and in vivo motion-corrupted multishot diffusion data. Evaluations were made both on the resulting imaging quality and estimated diffusion tensor metrics. RESULTS AMUSE was found to reduce image blurring resulting from macroscopic subject motion compared to MUSE but yielded inaccurate tensor estimations when neglecting the altered diffusion encoding. Including the altered diffusion encoding in AMUSE produced better estimations of diffusion tensors. CONCLUSION The use of AMUSE allows for improved image quality and diffusion tensor accuracy in the presence of macroscopic subject motion during multishot diffusion imaging. These techniques should facilitate future high-resolution diffusion imaging.
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Affiliation(s)
- Shayan Guhaniyogi
- Brain Imaging and Analysis Center, Duke University Medical Center, Durham, North Carolina, USA
| | - Mei-Lan Chu
- Brain Imaging and Analysis Center, Duke University Medical Center, Durham, North Carolina, USA
| | - Hing-Chiu Chang
- Brain Imaging and Analysis Center, Duke University Medical Center, Durham, North Carolina, USA
| | - Allen W Song
- Brain Imaging and Analysis Center, Duke University Medical Center, Durham, North Carolina, USA
| | - Nan-Kuei Chen
- Brain Imaging and Analysis Center, Duke University Medical Center, Durham, North Carolina, USA
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Zhao Y, Zhao T, Raval SB, Krishnamurthy N, Zheng H, Harris CT, Handler WB, Chronik BA, Ibrahim TS. Dual optimization method of radiofrequency and quasistatic field simulations for reduction of eddy currents generated on 7T radiofrequency coil shielding. Magn Reson Med 2014; 74:1461-9. [PMID: 25367703 DOI: 10.1002/mrm.25424] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/25/2014] [Revised: 06/26/2014] [Accepted: 08/04/2014] [Indexed: 01/20/2023]
Abstract
PURPOSE To optimize the design of radiofrequency (RF) shielding of transmit coils at 7T and reduce eddy currents generated on the RF shielding when imaging with rapid gradient waveforms. METHODS One set of a four-element, 2 × 2 Tic-Tac-Toe head coil structure was selected and constructed to study eddy currents on the RF coil shielding. The generated eddy currents were quantitatively studied in the time and frequency domains. The RF characteristics were studied using the finite difference time domain method. Five different kinds of RF shielding were tested on a 7T MRI scanner with phantoms and in vivo human subjects. RESULTS The eddy current simulation method was verified by the measurement results. Eddy currents induced by solid/intact and simple-structured slotted RF shielding significantly distorted the gradient fields. Echo-planar images, B1+ maps, and S matrix measurements verified that the proposed slot pattern suppressed the eddy currents while maintaining the RF characteristics of the transmit coil. CONCLUSION The presented dual-optimization method could be used to design RF shielding and reduce the gradient field-induced eddy currents while maintaining the RF characteristics of the transmit coil.
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Affiliation(s)
- Yujuan Zhao
- Department of Bioengineering, University of Pittsburgh, Pittsburgh, Pennsylvania, USA
| | - Tiejun Zhao
- Siemens Medical Solutions, Pittsburgh, Pennsylvania, USA
| | - Shailesh B Raval
- Department of Bioengineering, University of Pittsburgh, Pittsburgh, Pennsylvania, USA.,Department of Radiology, University of Pittsburgh, Pittsburgh, Pennsylvania, USA
| | | | - Hai Zheng
- Department of Bioengineering, University of Pittsburgh, Pittsburgh, Pennsylvania, USA
| | - Chad T Harris
- Department of Physics and Astronomy, University of Western Ontario, London, Canada
| | - William B Handler
- Department of Physics and Astronomy, University of Western Ontario, London, Canada
| | - Blaine A Chronik
- Department of Physics and Astronomy, University of Western Ontario, London, Canada
| | - Tamer S Ibrahim
- Department of Bioengineering, University of Pittsburgh, Pittsburgh, Pennsylvania, USA.,Department of Radiology, University of Pittsburgh, Pittsburgh, Pennsylvania, USA
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Chang HC, Guhaniyogi S, Chen NK. Interleaved diffusion-weighted improved by adaptive partial-Fourier and multiband multiplexed sensitivity-encoding reconstruction. Magn Reson Med 2014; 73:1872-84. [PMID: 24925000 DOI: 10.1002/mrm.25318] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/25/2013] [Revised: 05/06/2014] [Accepted: 05/22/2014] [Indexed: 11/08/2022]
Abstract
PURPOSE We report a series of techniques to reliably eliminate artifacts in interleaved echo-planar imaging (EPI) based diffusion-weighted imaging (DWI). METHODS First, we integrate the previously reported multiplexed sensitivity encoding (MUSE) algorithm with a new adaptive Homodyne partial-Fourier reconstruction algorithm, so that images reconstructed from interleaved partial-Fourier DWI data are free from artifacts even in the presence of either (a) motion-induced k-space energy peak displacement, or (b) susceptibility field gradient induced fast phase changes. Second, we generalize the previously reported single-band MUSE framework to multiband MUSE, so that both through-plane and in-plane aliasing artifacts in multiband multishot interleaved DWI data can be effectively eliminated. RESULTS The new adaptive Homodyne-MUSE reconstruction algorithm reliably produces high-quality and high-resolution DWI, eliminating residual artifacts in images reconstructed with previously reported methods. Furthermore, the generalized MUSE algorithm is compatible with multiband and high-throughput DWI. CONCLUSION The integration of the multiband and adaptive Homodyne-MUSE algorithms significantly improves the spatial-resolution, image quality, and scan throughput of interleaved DWI. We expect that the reported reconstruction framework will play an important role in enabling high-resolution DWI for both neuroscience research and clinical uses.
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Affiliation(s)
- Hing-Chiu Chang
- Brain Imaging and Analysis Center, Duke University Medical Center, Durham, North Carolina, USA
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Thian YL, Xie W, Porter DA, Weileng Ang B. Readout-segmented echo-planar imaging for diffusion-weighted imaging in the pelvis at 3T-A feasibility study. Acad Radiol 2014; 21:531-7. [PMID: 24594423 DOI: 10.1016/j.acra.2014.01.005] [Citation(s) in RCA: 40] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/19/2013] [Revised: 01/08/2014] [Accepted: 01/08/2014] [Indexed: 12/20/2022]
Abstract
RATIONALE AND OBJECTIVES Diffusion-weighted imaging (DWI) of the pelvis at 3T is prone to artifacts that diminish the image quality. Readout-segmented echo-planar imaging (RS-EPI) is a new DWI technique that can reduce the artifacts associated with standard single-shot echo-planar imaging (SS-EPI) DWI. The purpose of this study was to evaluate the feasibility and image quality of RS-EPI in pelvic DWI compared to SS-EPI on a 3T imaging system. MATERIALS AND METHODS Thirty patients underwent pelvic DWI on a 3T scanner with SS-EPI and RS-EPI techniques. Two blinded readers independently assessed each set of images for geometric distortion, image blurring, ghosting artifacts, lesion conspicuity, and overall image quality on a 7-point scale. Qualitative image scores were compared using paired Wilcoxon signed rank test. Interreader correlation was assessed by Spearman rank correlation. RESULTS Geometric distortion, imaging blurring, ghosting artifacts, lesion conspicuity, and overall image quality were rated significantly better by both readers for RS-EPI technique (P < .01 for all parameters). There was moderate-high correlation between the readers (r = 0.649-0.752) for all parameters apart from lesion conspicuity (r = 0.351). Both readers preferred the RS-EPI set of DWI images in most of the cases (reader 1: 0.87, 95% CI 0.74-0.99; reader 2: 0.77, 95% CI 0.61-0.93). Mean difference and limits of agreement between apparent diffusion coefficient (ADC) values obtained from the two methods were 0.01 (-0.08, 0.10) × 10(-3) mm(2)/s. CONCLUSIONS RS-EPI DWI images showed improved image quality compared to SS-EPI technique at 3T. RS-EPI is a feasible technique in the pelvis for producing high-resolution DWI.
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Cunningham CH, Dominguez Viqueira W, Hurd RE, Chen AP. Frequency correction method for improved spatial correlation of hyperpolarized 13C metabolites and anatomy. NMR Biomed 2014; 27:212-218. [PMID: 24353129 DOI: 10.1002/nbm.3055] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/07/2013] [Revised: 10/31/2013] [Accepted: 11/01/2013] [Indexed: 06/03/2023]
Abstract
Blip-reversed echo-planar imaging (EPI) is investigated as a method for measuring and correcting the spatial shifts that occur due to bulk frequency offsets in (13)C metabolic imaging in vivo. By reversing the k-space trajectory for every other time point, the direction of the spatial shift for a given frequency is reversed. Here, mutual information is used to find the 'best' alignment between images and thereby measure the frequency offset. Time-resolved 3D images of pyruvate/lactate/urea were acquired with 5 s temporal resolution over a 1 min duration in rats (N = 6). For each rat, a second injection was performed with the demodulation frequency purposely mis-set by +35 Hz, to test the correction for erroneous shifts in the images. Overall, the shift induced by the 35 Hz frequency offset was 5.9 ± 0.6 mm (mean ± standard deviation). This agrees well with the expected 5.7 mm shift based on the 2.02 ms delay between k-space lines (giving 30.9 Hz per pixel). The 0.6 mm standard deviation in the correction corresponds to a frequency-detection accuracy of 4 Hz. A method was presented for ensuring the spatial registration between (13)C metabolic images and conventional anatomical images when long echo-planar readouts are used. The frequency correction method was shown to have an accuracy of 4 Hz. Summing the spatially corrected frames gave a signal-to-noise ratio (SNR) improvement factor of 2 or greater, compared with the highest single frame.
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Affiliation(s)
- Charles H Cunningham
- Department of Medical Biophysics and Sunnybrook Health Sciences Centre, Toronto, Canada; Imaging Research, Sunnybrook Health Sciences Centre, Toronto, Canada
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Boujraf S. Strategies for assessing diffusion anisotropy on the basis of magnetic resonance images: comparison of systematic errors. J Med Signals Sens 2014; 4:85-93. [PMID: 24761372 PMCID: PMC3994720] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 06/13/2013] [Accepted: 12/30/2013] [Indexed: 12/04/2022]
Abstract
Diffusion weighted imaging uses the signal loss associated with the random thermal motion of water molecules in the presence of magnetic field gradients to derive a number of parameters that reflect the translational mobility of the water molecules in tissues. With a suitable experimental set-up, it is possible to calculate all the elements of the local diffusion tensor (DT) and derived parameters describing the behavior of the water molecules in each voxel. One of the emerging applications of the information obtained is an interpretation of the diffusion anisotropy in terms of the architecture of the underlying tissue. These interpretations can only be made provided the experimental data which are sufficiently accurate. However, the DT results are susceptible to two systematic error sources: On one hand, the presence of signal noise can lead to artificial divergence of the diffusivities. In contrast, the use of a simplified model for the interaction of the protons with the diffusion weighting and imaging field gradients (b matrix calculation), common in the clinical setting, also leads to deviation in the derived diffusion characteristics. In this paper, we study the importance of these two sources of error on the basis of experimental data obtained on a clinical magnetic resonance imaging system for an isotropic phantom using a state of the art single-shot echo planar imaging sequence. Our results show that optimal diffusion imaging require combining a correct calculation of the b-matrix and a sufficiently large signal to noise ratio.
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Affiliation(s)
- Saïd Boujraf
- Department of Biophysics and Clinical MRI Methods, Faculty of Medicine and Pharmacy, University of Fez, Fez, Morocco,Address for correspondence: Dr. Saïd Boujraf, Department of Biophysics and Clinical MRI Methods, Faculty of Medicine and Pharmacy, University of Fez, BP 1893, Km 2.200, Sidi Hrazem Road, Fez 30000, Morocco. E-mail:
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Bhushan C, Joshi AA, Leahy RM, Haldar JP. Improved B0 -distortion correction in diffusion MRI using interlaced q-space sampling and constrained reconstruction. Magn Reson Med 2013; 72:1218-32. [PMID: 24464424 DOI: 10.1002/mrm.25026] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/03/2013] [Revised: 09/19/2013] [Accepted: 10/11/2013] [Indexed: 11/06/2022]
Abstract
PURPOSE To enable high-quality correction of susceptibility-induced geometric distortion artifacts in diffusion magnetic resonance imaging (MRI) images without increasing scan time. THEORY AND METHODS A new method for distortion correction is proposed based on subsampling a generalized version of the state-of-the-art reversed-gradient distortion correction method. Rather than acquire each q-space sample multiple times with different distortions (as in the conventional reversed-gradient method), we sample each q-space point once with an interlaced sampling scheme that measures different distortions at different q-space locations. Distortion correction is achieved using a novel constrained reconstruction formulation that leverages the smoothness of diffusion data in q-space. RESULTS The effectiveness of the proposed method is demonstrated with simulated and in vivo diffusion MRI data. The proposed method is substantially faster than the reversed-gradient method, and can also provide smaller intensity errors in the corrected images and smaller errors in derived quantitative diffusion parameters. CONCLUSION The proposed method enables state-of-the-art distortion correction performance without increasing data acquisition time.
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Affiliation(s)
- Chitresh Bhushan
- Signal and Image Processing Institute, Ming Hsieh Department of Electrical Engineering, University of Southern California, Los Angeles, California, USA
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Guo W, Liu F, Liu J, Yu L, Zhang Z, Zhang J, Chen H, Xiao C. Is there a cerebellar compensatory effort in first-episode, treatment-naive major depressive disorder at rest? Prog Neuropsychopharmacol Biol Psychiatry 2013; 46:13-8. [PMID: 23800464 DOI: 10.1016/j.pnpbp.2013.06.009] [Citation(s) in RCA: 75] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/05/2013] [Revised: 06/04/2013] [Accepted: 06/13/2013] [Indexed: 01/15/2023]
Abstract
BACKGROUND This study was undertaken to explore whether there is a cerebellar compensatory response in patients with first-episode, treatment-naive major depressive disorder (MDD). The cerebellar compensatory response is defined as a cerebellar hyperactivity which would be inversely correlated with both the activation of the functionally connected cerebral regions and the depression severity. METHODS Resting-state functional magnetic resonance imaging (fMRI) data of 24 patients with MDD and 24 healthy subjects were analyzed with the fractional amplitude of low-frequency fluctuations (fALFF) and functional connectivity (FC) methods. The structural images were processed with the voxel-based morphometry (VBM) method. RESULTS Compared to healthy controls, depressed patients had significantly increased fALFF in the left Crus I and the left cerebellar lobule VI. FC analysis of these two seeded regions found that depressed patients had increased FC between the left Crus I and the right hippocampus, but had decreased FC between the left Crus I and the left inferior parietal lobule (IPL), and between the left cerebellar lobule VI and bilateral inferior temporal gyrus. No correlation was observed between the abnormal fALFF of the seeds and their connected regions and the depression severity or the executive function. The VBM results did not show significant reduction in gray or white matter volume in any above-mentioned region. CONCLUSIONS Our findings suggest that increased cerebellar activity at resting state may be a disease state phenomenon but not a compensatory response to the dysfunction of the default mode network (DMN) in MDD.
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Affiliation(s)
- Wenbin Guo
- Mental Health Center, the First Affiliated Hospital, Guangxi Medical University; Nanning, Guangxi 530021, China.
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Schulte RF, Wiesinger F. Direct design of 2D RF pulses using matrix inversion. J Magn Reson 2013; 235:115-120. [PMID: 24013595 DOI: 10.1016/j.jmr.2013.07.014] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/10/2013] [Revised: 07/17/2013] [Accepted: 07/20/2013] [Indexed: 06/02/2023]
Abstract
Multi-dimensional pulses are frequently used in MRI for applications such as targeted excitation, fat-water separation or metabolic imaging with hyperpolarised (13)C compounds. For the design, the problem is typically separated into the different dimensions. In this work, a method to directly design two-dimensional pulses using the small-tip angle approximation is introduced based on a direct matrix representation. The numerical problem is solved in a single step directly in two dimensions by matrix inversion. Exemplary spectral-spatial excitation and spatio-temporal encoding (SPEN) pulses are designed and validated. The main benefits of the direct design approach include a reduction of artefacts in case of spectral-spatial pulses, a simple and straightforward computer implementation and high flexibility in the pulse design.
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Affiliation(s)
- Rolf F Schulte
- GE Global Research, Freisinger Landstr. 50, 85748 Garching bei München, Germany.
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Thompson GJ, Pan WJ, Magnuson ME, Jaeger D, Keilholz SD. Quasi-periodic patterns (QPP): large-scale dynamics in resting state fMRI that correlate with local infraslow electrical activity. Neuroimage 2013; 84:1018-31. [PMID: 24071524 DOI: 10.1016/j.neuroimage.2013.09.029] [Citation(s) in RCA: 102] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/18/2013] [Revised: 08/07/2013] [Accepted: 09/14/2013] [Indexed: 10/26/2022] Open
Abstract
Functional connectivity measurements from resting state blood-oxygen level dependent (BOLD) functional magnetic resonance imaging (fMRI) are proving a powerful tool to probe both normal brain function and neuropsychiatric disorders. However, the neural mechanisms that coordinate these large networks are poorly understood, particularly in the context of the growing interest in network dynamics. Recent work in anesthetized rats has shown that the spontaneous BOLD fluctuations are tightly linked to infraslow local field potentials (LFPs) that are seldom recorded but comparable in frequency to the slow BOLD fluctuations. These findings support the hypothesis that long-range coordination involves low frequency neural oscillations and establishes infraslow LFPs as an excellent candidate for probing the neural underpinnings of the BOLD spatiotemporal patterns observed in both rats and humans. To further examine the link between large-scale network dynamics and infraslow LFPs, simultaneous fMRI and microelectrode recording were performed in anesthetized rats. Using an optimized filter to isolate shared components of the signals, we found that time-lagged correlation between infraslow LFPs and BOLD is comparable in spatial extent and timing to a quasi-periodic pattern (QPP) found from BOLD alone, suggesting that fMRI-measured QPPs and the infraslow LFPs share a common mechanism. As fMRI allows spatial resolution and whole brain coverage not available with electroencephalography, QPPs can be used to better understand the role of infraslow oscillations in normal brain function and neurological or psychiatric disorders.
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Affiliation(s)
- Garth John Thompson
- Department of Biomedical Engineering, Emory University/Georgia Institute of Technology, 101 Woodruff Circle, Atlanta, GA 30322, USA.
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Wang X, Jiao Y, Tang T, Wang H, Lu Z. Investigating univariate temporal patterns for intrinsic connectivity networks based on complexity and low-frequency oscillation: a test-retest reliability study. Neuroscience 2013; 254:404-26. [PMID: 24042040 DOI: 10.1016/j.neuroscience.2013.09.009] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/04/2013] [Revised: 08/18/2013] [Accepted: 09/04/2013] [Indexed: 11/25/2022]
Abstract
Intrinsic connectivity networks (ICNs) are composed of spatial components and time courses. The spatial components of ICNs were discovered with moderate-to-high reliability. So far as we know, few studies focused on the reliability of the temporal patterns for ICNs based their individual time courses. The goals of this study were twofold: to investigate the test-retest reliability of temporal patterns for ICNs, and to analyze these informative univariate metrics. Additionally, a correlation analysis was performed to enhance interpretability. Our study included three datasets: (a) short- and long-term scans, (b) multi-band echo-planar imaging (mEPI), and (c) eyes open or closed. Using dual regression, we obtained the time courses of ICNs for each subject. To produce temporal patterns for ICNs, we applied two categories of univariate metrics: network-wise complexity and network-wise low-frequency oscillation. Furthermore, we validated the test-retest reliability for each metric. The network-wise temporal patterns for most ICNs (especially for default mode network, DMN) exhibited moderate-to-high reliability and reproducibility under different scan conditions. Network-wise complexity for DMN exhibited fair reliability (ICC<0.5) based on eyes-closed sessions. Specially, our results supported that mEPI could be a useful method with high reliability and reproducibility. In addition, these temporal patterns were with physiological meanings, and certain temporal patterns were correlated to the node strength of the corresponding ICN. Overall, network-wise temporal patterns of ICNs were reliable and informative and could be complementary to spatial patterns of ICNs for further study.
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Affiliation(s)
- X Wang
- School of Biological Science and Medical Engineering, Southeast University, Nanjing 210096, China; Key Laboratory of Child Development and Learning Science (Ministry of Education), Southeast University, Nanjing 210096, China
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Bender JA, Ahmad R, Simonetti OP. The Importance of k-Space Trajectory on Off-Resonance Artifact in Segmented Echo-Planar Imaging. Concepts Magn Reson Part A Bridg Educ Res 2013; 42A:10.1002/cmr.a.21255. [PMID: 24358026 PMCID: PMC3864862 DOI: 10.1002/cmr.a.21255] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/03/2023]
Abstract
Segmented interleaved echo planar imaging (EPI) is a highly efficient data acquisition technique; however, EPI is sensitive to artifacts from off-resonance spins. The choice of k-space trajectories is important in determining how off-resonance spins contribute to image artifacts. Top-down and center-out trajectories are theoretically analyzed, simulated, implemented, and tested in phantom and volunteer experiments. Theoretical results show off-resonance artifact manifests as a simple positional shift for the top-down trajectory, while for the center-out trajectory off-resonance artifact manifests as a splitting of the object, which entails both shift and blurring. These results were validated using simulation and phantom scan data where a frequency-offset was introduced ranging from -300 Hz to +300 Hz. As predicted by the theoretical results, inferior image quality was observed for the center-out trajectory in a single volunteer. Off-resonance produces more severe and complex artifacts with the center-out trajectory than the top-down trajectory.
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Affiliation(s)
- Jacob A Bender
- Department of Biomedical Engineering, The Ohio State University, Columbus, OH ; Dorothy M. Davis Heart and Lung Research Institute, The Ohio State University, Columbus, OH
| | - Rizwan Ahmad
- Dorothy M. Davis Heart and Lung Research Institute, The Ohio State University, Columbus, OH ; Department of Electrical and Computer Engineering, The Ohio State University, Columbus, OH
| | - Orlando P Simonetti
- Department of Biomedical Engineering, The Ohio State University, Columbus, OH ; Dorothy M. Davis Heart and Lung Research Institute, The Ohio State University, Columbus, OH ; Department of Internal Medicine, Division of Cardiovascular Medicine, The Ohio State University, Columbus, OH ; Department of Radiology, The Ohio State University, Columbus, OH
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Holdsworth SJ, Skare S, Newbould RD, Bammer R. Robust GRAPPA-accelerated diffusion-weighted readout-segmented (RS)-EPI. Magn Reson Med 2009; 62:1629-40. [PMID: 19859974 PMCID: PMC2904969 DOI: 10.1002/mrm.22122] [Citation(s) in RCA: 90] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/08/2008] [Accepted: 05/28/2009] [Indexed: 11/11/2022]
Abstract
Readout segmentation (RS-EPI) has been suggested as a promising variant to echo-planar imaging (EPI) for high-resolution imaging, particularly when combined with parallel imaging. This work details some of the technical aspects of diffusion-weighted (DW)-RS-EPI, outlining a set of reconstruction methods and imaging parameters that can both minimize the scan time and afford high-resolution diffusion imaging with reduced distortions. These methods include an efficient generalized autocalibrating partially parallel acquisition (GRAPPA) calibration for DW-RS-EPI data without scan time penalty, together with a variant for the phase correction of partial Fourier RS-EPI data. In addition, the role of pulsatile and rigid-body brain motion in DW-RS-EPI was assessed. Corrupt DW-RS-EPI data arising from pulsatile nonlinear brain motion had a prevalence of approximately 7% and were robustly identified via k-space entropy metrics. For DW-RS-EPI data corrupted by rigid-body motion, we showed that no blind overlap was required. The robustness of RS-EPI toward phase errors and motion, together with its minimized distortions compared with EPI, enables the acquisition of exquisite 3 T DW images with matrix sizes close to 512(2).
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Affiliation(s)
- Samantha J. Holdsworth
- Lucas MRS/I Center, Department of Radiology, Stanford University, Stanford, California, USA
| | - Stefan Skare
- Lucas MRS/I Center, Department of Radiology, Stanford University, Stanford, California, USA
| | - Rexford D. Newbould
- Lucas MRS/I Center, Department of Radiology, Stanford University, Stanford, California, USA
| | - Roland Bammer
- Lucas MRS/I Center, Department of Radiology, Stanford University, Stanford, California, USA
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