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Tsai SY, Hsu YC, Chu YH, Kuo WJ, Lin FH. Combining parallel detection of proton echo planar spectroscopic imaging (PEPSI) measurements with a data-consistency constraint improves SNR. NMR IN BIOMEDICINE 2015; 28:1678-1687. [PMID: 26484749 DOI: 10.1002/nbm.3425] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/29/2015] [Revised: 09/09/2015] [Accepted: 09/10/2015] [Indexed: 06/05/2023]
Abstract
One major challenge of MRSI is the poor signal-to-noise ratio (SNR), which can be improved by using a surface coil array. Here we propose to exploit the spatial sensitivity of different channels of a coil array to enforce the k-space data consistency (DC) in order to suppress noise and consequently to improve MRSI SNR. MRSI data were collected using a proton echo planar spectroscopic imaging (PEPSI) sequence at 3 T using a 32-channel coil array and were averaged with one, two and eight measurements (avg-1, avg-2 and avg-8). The DC constraint was applied using a regularization parameter λ of 1, 2, 3, 5 or 10. Metabolite concentrations were quantified using LCModel. Our results show that the suppression of noise by applying the DC constraint to PEPSI reconstruction yields up to 32% and 27% SNR gain for avg-1 and avg-2 data with λ = 5, respectively. According to the reported Cramer-Rao lower bounds, the improvement in metabolic fitting was significant (p < 0.01) when the DC constraint was applied with λ ≥ 2. Using the DC constraint with λ = 3 or 5 can minimize both root-mean-square errors and spatial variation for all subjects using the avg-8 data set as reference values. Our results suggest that MRSI reconstructed with a DC constraint can save around 70% of scanning time to obtain images and spectra with similar SNRs using λ = 5.
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Affiliation(s)
- Shang-Yueh Tsai
- Graduate Institute of Applied Physics, National Chengchi University, Taipei, Taiwan
- Research Center for Mind, Brain and Learning, National Chengchi University, Taipei, Taiwan
| | - Yi-Cheng Hsu
- Institute of Biomedical Engineering, National Taiwan University, Taipei, Taiwan
| | - Ying-Hua Chu
- Institute of Biomedical Engineering, National Taiwan University, Taipei, Taiwan
| | - Wen-Jui Kuo
- Institute of Neuroscience, National Yang Ming University, Taipei, Taiwan
| | - Fa-Hsuan Lin
- Institute of Biomedical Engineering, National Taiwan University, Taipei, Taiwan
- Department of Biomedical Engineering and Computational Science, Aalto University, Espoo, Finland
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Xing XH, Cheng YS. Magnetic resonance functional and molecular imaging for diagnosis of rectal cancer: Recent research advances. Shijie Huaren Xiaohua Zazhi 2013; 21:1726-1732. [DOI: 10.11569/wcjd.v21.i18.1726] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
Colorectal cancer is one of the most common gastrointestinal malignant tumors in China. Because of the difficulties in early diagnosis, the incidence and mortality of colorectal cancer have been increasing year by year. Molecular and functional imaging plays an important role in detecting rectal cancer earlier and more specifically and reducing patients' mortality. In this paper we discuss the present and future applications of magnetic resonance molecular and functional imaging in the diagnosis of rectal tumors.
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Lin FH, Vesanen PT, Hsu YC, Nieminen JO, Zevenhoven KCJ, Dabek J, Parkkonen LT, Simola J, Ahonen AI, Ilmoniemi RJ. Suppressing multi-channel ultra-low-field MRI measurement noise using data consistency and image sparsity. PLoS One 2013; 8:e61652. [PMID: 23626710 PMCID: PMC3633989 DOI: 10.1371/journal.pone.0061652] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/06/2012] [Accepted: 03/12/2013] [Indexed: 11/18/2022] Open
Abstract
Ultra-low-field (ULF) MRI (B0 = 10–100 µT) typically suffers from a low signal-to-noise ratio (SNR). While SNR can be improved by pre-polarization and signal detection using highly sensitive superconducting quantum interference device (SQUID) sensors, we propose to use the inter-dependency of the k-space data from highly parallel detection with up to tens of sensors readily available in the ULF MRI in order to suppress the noise. Furthermore, the prior information that an image can be sparsely represented can be integrated with this data consistency constraint to further improve the SNR. Simulations and experimental data using 47 SQUID sensors demonstrate the effectiveness of this data consistency constraint and sparsity prior in ULF-MRI reconstruction.
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Affiliation(s)
- Fa-Hsuan Lin
- Institute of Biomedical Engineering, National Taiwan University, Taipei, Taiwan.
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Baumann T, Kannengiesser SAR, Honal M. Temporally constrained respiratory gating improves continuously moving table MRI during free breathing. J Magn Reson Imaging 2012; 38:198-205. [PMID: 23239532 DOI: 10.1002/jmri.23964] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/09/2012] [Accepted: 10/23/2012] [Indexed: 11/09/2022] Open
Abstract
PURPOSE To evaluate a novel breathing motion correction algorithm for continuously moving table magnetic resonance imaging (CMT-MRI) that optimizes motion consistency in a fixed time span. MATERIALS AND METHODS In 22 patients CMT-MRI was performed during free breathing. During a preparatory phase (constant) or continuously during the scan (adaptive) gating thresholds were computed from breathing states that should allow for motion consistent k-space sampling. After data from a first k-space traversal was acquired irrespective of breathing motion, subsequently k-space lines with discordant breathing states were reacquired below the gating threshold. Time constraints of CMT-MRI were respected, because a fixed time was allocated for reacquisition. Image quality and lesion depiction were evaluated on images reconstructed from the first traversal and motion-corrected images. RESULTS Compared to constant thresholds, gating with adaptive thresholds led to a higher number of reacquired k-space lines (60.1%/41.7%) and a larger fraction of motion consistent final k-space lines (96.6%/78.8%). Adaptive gating induced a significant increase in image quality for all regions affected by breathing motion. Only one of 22 lesions was not depicted on the adaptively corrected images, whereas 15 were readily appreciable. CONCLUSION Temporally constrained respiratory gating with adaptive thresholds allows for fully sampled, motion-corrected CMT-MRI acquisitions during free breathing.
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Affiliation(s)
- Tobias Baumann
- Department of Diagnostic Radiology, University Hospital Freiburg, Germany.
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Zhang J, Liu C, Moseley ME. Parallel reconstruction using null operations. Magn Reson Med 2011; 66:1241-53. [PMID: 21604290 PMCID: PMC3162069 DOI: 10.1002/mrm.22899] [Citation(s) in RCA: 40] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/11/2010] [Revised: 01/25/2011] [Accepted: 02/07/2011] [Indexed: 11/11/2022]
Abstract
A novel iterative k-space data-driven technique, namely parallel reconstruction using null operations (PRUNO), is presented for parallel imaging reconstruction. In PRUNO, both data calibration and image reconstruction are formulated into linear algebra problems based on a generalized system model. An optimal data calibration strategy is demonstrated by using singular value decomposition, and an iterative conjugate-gradient approach is proposed to efficiently solve missing k-space samples during reconstruction. With its generalized formulation and precise mathematical model, PRUNO reconstruction yields good accuracy, flexibility, and stability. Both computer simulation and in vivo studies have shown that PRUNO produces much better reconstruction quality than generalized autocalibrating partially parallel acquisition (GRAPPA), especially under high accelerating rates. With the aid of PRUNO reconstruction, ultra-high accelerating parallel imaging can be performed with decent image quality. For example, we have done successful PRUNO reconstruction at a reduction factor of 6 (effective factor of 4.44) with eight coils and only a few autocalibration signal lines.
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Affiliation(s)
- Jian Zhang
- Department of Electrical Engineering, Stanford University, Stanford, California, USA.
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Lin W, Huang F, Duensing GR, Reykowski A. High temporal resolution retrospective motion correction with radial parallel imaging. Magn Reson Med 2011; 67:1097-105. [PMID: 21842499 DOI: 10.1002/mrm.23092] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/08/2011] [Revised: 06/08/2011] [Accepted: 06/20/2011] [Indexed: 11/07/2022]
Abstract
A method for motion correction in multicoil imaging applications, involving both data collection and reconstruction, is presented. A bit-reversed radial acquisition scheme, in conjunction with a rapid self-calibrated parallel imaging method, Generalized auto-calibrating partial parallel acquisition (GRAPPA) operator for wider radial bands (GROWL), is used to achieve motion correction at a high temporal resolution. View-by-view in-plane motion correction is achieved in 2D imaging, while 3D motion correction is achieved for every two consecutive slice-encoding planes in 3D imaging. In the proposed technique, GROWL contributes in two aspects: First, a central k-space circle/cylinder used as the motion-free reference is generated from a small number of radial lines/planes; Second, undersampled k-space regions resulting from rotation and inconsistent (e.g. intraview and nonrigid body) motion can be filled in. When compared with navigator-based motion correction methods, the proposed method does not prolong scan time and can be applied to short-TR sequences. Magn Reson Med, 2011. © 2011 Wiley-Liss, Inc.
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Affiliation(s)
- Wei Lin
- Invivo Corporation, Philips Healthcare, Gainesville, FL, USA.
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Huang F, Lin W, Börnert P, Li Y, Reykowski A. Data convolution and combination operation (COCOA) for motion ghost artifacts reduction. Magn Reson Med 2010; 64:157-66. [PMID: 20572134 DOI: 10.1002/mrm.22358] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Affiliation(s)
- Feng Huang
- Invivo Corporation, Gainesville, Florida 32608, USA.
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Huff S, Honal M, Baumann T, Hennig J, Markl M, Ludwig U. Continuously moving table time-of-flight angiography of the peripheral veins. Magn Reson Med 2010; 63:1219-29. [DOI: 10.1002/mrm.22296] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Affiliation(s)
- Sandra Huff
- Department of Diagnostic Radiology, Medical Physics, University Hospital Freiburg, Freiburg, Germany.
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Lin W, Huang F, Börnert P, Li Y, Reykowski A. Motion correction using an enhanced floating navigator and GRAPPA operations. Magn Reson Med 2010; 63:339-48. [PMID: 19918907 DOI: 10.1002/mrm.22200] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
A method for motion correction in multicoil imaging applications, involving both data collection and reconstruction, is presented. The floating navigator method, which acquires a readout line off center in the phase-encoding direction, is expanded to detect translation/rotation and inconsistent motion. This is done by comparing floating navigator data with a reference k-space region surrounding the floating navigator line, using a correlation measure. The technique of generalized autocalibrating partially parallel acquisition is further developed to correct for a fully sampled, motion-corrupted dataset. The flexibility of generalized autocalibrating partially parallel acquisition kernels is exploited by extrapolating readout lines to fill in missing "pie slices" of k-space caused by rotational motion and regenerating full k-space data from multiple interleaved datasets, facilitating subsequent rigid-body motion correction or proper weighting of inconsistent data (e.g., with through-plane and nonrigid motion). Phantom and in vivo imaging experiments with turbo spin-echo sequence demonstrate the correction of severe motion artifacts.
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Affiliation(s)
- Wei Lin
- Invivo Corporation, Philips Healthcare, Gainesville, Florida 32608, USA.
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Honal M, Leupold J, Huff S, Baumann T, Ludwig U. Compensation of breathing motion artifacts for MRI with continuously moving table. Magn Reson Med 2010; 63:701-12. [DOI: 10.1002/mrm.22162] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
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Jacobs MA, Pan L, Macura KJ. Whole-body diffusion-weighted and proton imaging: a review of this emerging technology for monitoring metastatic cancer. Semin Roentgenol 2009; 44:111-22. [PMID: 19233086 PMCID: PMC2955431 DOI: 10.1053/j.ro.2009.01.003] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Affiliation(s)
- Michael A Jacobs
- The Russell H. Morgan Department of Radiology and Radiological Science, The Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA.
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Baumann T, Ludwig U, Pache G, Fautz HP, Kotter E, Langer M, Schaefer O. Continuously moving table MRI with sliding multislice for rectal cancer staging: image quality and lesion detection. Eur J Radiol 2009; 73:579-87. [PMID: 19179029 DOI: 10.1016/j.ejrad.2008.12.008] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/14/2008] [Revised: 10/04/2008] [Accepted: 12/10/2008] [Indexed: 12/27/2022]
Abstract
PURPOSE To determine image quality and lesion detection of sliding multislice (SMS), a recently developed moving table MRI technique, in patients with rectal cancer. MATERIALS AND METHODS Twenty-seven paired SMS (Avanto, Siemens Medical Solutions) and MDCT (Sensation 64, Siemens Medical Solutions) examinations of abdomen and pelvis were performed in patients with rectal cancer and compared for detection of liver, lymph node and bone metastases by two independent observers. A contrast-enhanced, fat saturated 2D gradient echo sequence (TE, 2.0 ms; TR, 102 ms; slice, 5 mm) was acquired with SMS and a standard contrast-enhanced protocol (100 ml @ 2.5 ml/s; slice, 5 mm) was used for abdominal MDCT. Standard of reference consisted of a consensus evaluation of SMS, MDCT, and all available follow-up examinations after a period of 6 months. Artifact burden and image quality of SMS was assessed in comparison to stationary gradient echo sequences obtained in an age-matched group of 27 patients. RESULTS Whereas SMS achieved a mean quality score of 3.65 (scale, 0-4) for the liver, representing very good diagnostic properties, strong breathing artifacts in the intestinal region were observed in 19 cases by both observers. The retroperitoneum still achieved a mean quality score of 3.52, although breathing artifacts were noted in 12 and 15 cases (observers 1 and 2, respectively). The sensitivities of SMS to detect hepatic metastases were 91.2% and 94.1% for both observers, respectively, compared to 98.5%/98.5% for MDCT. The sensitivities for lymph node metastases were 87.5%/81.3% for SMS compared to 78.1%/81.3% for MDCT. The sensitivities for bone metastases were 91.7%/100% for SMS compared to 8.3%/16.7% for MDCT. CONCLUSION With slightly reduced image quality in the intestinal region, SMS exhibits equal detection of lymph node and liver metastases compared to MDCT. SMS MRI proved to be superior to MDCT in detection of bone metastases.
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Affiliation(s)
- Tobias Baumann
- Department of Diagnostic Radiology, University Hospital Freiburg, Freiburg, Germany.
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Detection of pulmonary nodules with move-during-scan magnetic resonance imaging using a free-breathing turbo inversion recovery magnitude sequence. Invest Radiol 2008; 43:359-67. [PMID: 18496040 DOI: 10.1097/rli.0b013e31816901fa] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
PURPOSE Detection of pulmonary metastases is still a challenging task for magnetic resonance imaging (MRI). It was the aim of this study to evaluate the potential of a free-breathing move-during-scan turbo inversion recovery magnitude sequence for the detection of pulmonary nodules. MATERIALS AND METHODS The sensitivities and positive-predictive values of 2 radiologists to detect pulmonary nodules in 41 move-during-scan MRI examinations of 38 patients with different malignancies were calculated and subgroup analyses according to lesion size and localization were performed. Multidetector computed tomography served as the standard of reference. Additionally, 6 radiologists rated the confidence for the presence of nodular lesions in 212 regions-of-interest, which were randomly selected to represent lesions of various sizes as well as negative findings. Receiver-operator-characteristic was performed. RESULTS Three hundred twenty-one nodules were found in 30 patients by multidetector computed tomography. Sensitivity and specificity of MRI to detect pulmonary nodules larger than 3 mm on a per-patient basis were 81.8% and 94.7%, respectively. On a per-lesion basis, MRI revealed a sensitivity of 79.0% to 80.7% for lesions larger than 3 mm, if high conspicuity ratings were counted as positive, and 84.6%, if medium and high conspicuity ratings were counted as positive. Sensitivity increased uniformly with lesion size, and all lesions larger than 12 mm were detected. Receiver-operator-characteristic analysis revealed a mean accuracy of 0.90 and sensitivities over 90% for lesions larger than 3 mm with a specificity of 96.1%. For lesions larger than 6 mm the accuracy was 0.99. CONCLUSION Detection of pulmonary nodules with a move-during-scan turbo inversion recovery magnitude sequence is feasible. Excellent detection of lesions larger than 6 mm is achievable with free-breathing moving-table MRI.
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Börnert P, Aldefeld B. Principles of whole-body continuously-moving-table MRI. J Magn Reson Imaging 2008; 28:1-12. [DOI: 10.1002/jmri.21339] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022] Open
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