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Meixner CR, Liebig P, Speier P, Forman C, Hensel B, Schmidt M, Saake M, Uder M, Doerfler A, Heidemann RM, Schmitter S, Nagel AM. High resolution time-of-flight MR-angiography at 7 T exploiting VERSE saturation, compressed sensing and segmentation. Magn Reson Imaging 2019; 63:193-204. [PMID: 31434005 DOI: 10.1016/j.mri.2019.08.014] [Citation(s) in RCA: 16] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/05/2019] [Revised: 08/04/2019] [Accepted: 08/15/2019] [Indexed: 02/06/2023]
Abstract
BACKGROUND 3D Time-of-Flight (TOF) MR-angiography (MRA) substantially benefits from ultra-high magnetic field strengths (≥7 T) due to increased Signal-to-Noise ratio and improved contrast. However, high-resolution TOF-MRA usually requires long acquisition times. In addition, specific absorption rate constraints limit the choice of optimal pulse sequence parameters, especially if venous saturation is employed. PURPOSE To implement and evaluate an arterial TOF-MRA for accelerated high-resolution angiography at ultra-high magnetic field strength. FIELD STRENGTHS/SEQUENCE 7 T modified gradient-echo TOF sequence including venous saturation using Variable-Rate Selective Excitation (VERSE), Compressed Sensing (CS) and sparse application of saturation pulses, called segmentation, were included for acceleration. ASSESSMENT To analyze the acceleration techniques all volunteers were examined with the same protocols. CS with different sampling patterns and regularization factors as well as segmentation were applied for acceleration. For comparison, conventional acceleration techniques were applied (GRAPPA PAT 3 and Partial Fourier (6/8 in slice/phase encoding)). Images were co-registered and 40 mm thick transversal maximum intensity projections were created to calculate the relative number of vessels. To analyze the visibility of small vessels, the lenticulostriate arteries (LSA) were examined. This was done via multiscale vessel enhancement filtering in a VOI and quantification via Fiji ImageJ as well as qualitatively evaluation by two radiologists. Additionally, the venous/arterial vessel-to-background ratios (vVBR/aVBR) were calculated for chosen protocols. RESULTS For the acceleration of a high resolution TOF-MRA (0.31 mm isotropic), under-sampling of 9.6 showed aliasing artifacts, whereas 7.2 showed no aliasing. The regularization factor R had a strong impact on the image quality according to smoothing (R = 0.01 to R = 0.005) and noise (R = 0.0005 to R = 0.00005). With the alternating sampling patterns it was shown that the k-space center should not be under-sampled too much. Additionally segmentation could be verified to be feasible for stronger acceleration with sufficient venous suppression. CONCLUSION The combination of several independent techniques (VERSE, CS with acceleration factor 7.2, R = 0.001, Poisson disc radius of 80%, 3 segments) enables the application of high-resolution (0.31 mm isotropic) TOF-MRA with venous saturation at 7 T in clinical time settings (TA ≈ 5 min) and within the SAR limits.
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Affiliation(s)
- Christian R Meixner
- Institute of Radiology, University Hospital Erlangen, Friedrich-Alexander Universität Erlangen-Nürnberg (FAU), Erlangen, Germany.
| | - Patrick Liebig
- Siemens Healthcare GmbH, Erlangen, Germany; Max Schaldach-Stiftungsprofessur für Biomedizinische Technik (MSBT), Friedrich-Alexander Universität Erlangen-Nürnberg (FAU), Erlangen, Germany
| | | | | | - Bernhard Hensel
- Max Schaldach-Stiftungsprofessur für Biomedizinische Technik (MSBT), Friedrich-Alexander Universität Erlangen-Nürnberg (FAU), Erlangen, Germany
| | - Manuel Schmidt
- Department of Neuroradiology, University Hospital Erlangen, Friedrich-Alexander Universität Erlangen-Nürnberg (FAU), Erlangen, Germany
| | - Marc Saake
- Institute of Radiology, University Hospital Erlangen, Friedrich-Alexander Universität Erlangen-Nürnberg (FAU), Erlangen, Germany
| | - Michael Uder
- Institute of Radiology, University Hospital Erlangen, Friedrich-Alexander Universität Erlangen-Nürnberg (FAU), Erlangen, Germany
| | - Arnd Doerfler
- Department of Neuroradiology, University Hospital Erlangen, Friedrich-Alexander Universität Erlangen-Nürnberg (FAU), Erlangen, Germany
| | | | - Sebastian Schmitter
- Physikalisch-Technische Bundesanstalt, Berlin, Germany; Division of Medical Physics in Radiology, German Cancer Research Center (DKFZ), Heidelberg, Germany
| | - Armin M Nagel
- Institute of Radiology, University Hospital Erlangen, Friedrich-Alexander Universität Erlangen-Nürnberg (FAU), Erlangen, Germany; Division of Medical Physics in Radiology, German Cancer Research Center (DKFZ), Heidelberg, Germany; Institute of Medical Physics, Friedrich-Alexander Universität Erlangen-Nürnberg (FAU), Erlangen, Germany
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Fast Abdominal Contrast-Enhanced Imaging With High Parallel-Imaging Factors Using a 60-Channel Receiver Coil Setup. Invest Radiol 2018; 53:602-608. [DOI: 10.1097/rli.0000000000000481] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
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Ohno N, Miyati T, Niwa Y, Kan H, Ishida S, Kasai H, Shibamoto Y, Gabata T. Novel practical SNR determination method for MRI using double echo with longest second echo time (DELSET). Br J Radiol 2018; 91:20170652. [PMID: 29565674 DOI: 10.1259/bjr.20170652] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022] Open
Abstract
OBJECTIVE We devised a practical method using double echo with the longest second echo time (DELSET) for simple and accurate signal-to-noise ratio (SNR) measurement of MRIs. METHODS The DELSET method is based on the double-echo sequence in which the first and second echo times (TE) are set, respectively, as the clinically acceptable time for the signal image and as the longest time for the noise image. The second TE needs to be at least 8 times longer than T2 (for spin-echo) or T2* (for gradient-echo) of the objective tissue. For example, second TE > 560 ms for the case of T2 = 70 ms: the real part of signal intensity theoretically reaches the same order of magnitude as the quantization limit, due to the T2 relaxation process. SNR was calculated by dividing mean signal intensity in the first echo image by signal standard deviation (SD) in the second echo image in identical regions of interest after necessary noise correction. We determined the SNRs of cylindrical phantom images with different coils [quadrature (QD) and array coils] and sequences (spin-echo and spoiled gradient-echo sequences) and compared them between the DELSET and subtraction or background methods. The ratio of the mean signal intensity and SD in the second echo image with QD coil was determined to confirm whether the signal intensity had reached noise level. RESULTS There were no significant differences in the phantom SNRs with both coils and sequences when DELSET was compared with the other two methods (p > 0.05 for all). The ratios of mean signal intensity and SD in the second echo images with both sequences were found to be in general agreement with a theoretical value. It was possible to obtain SNR images of the phantom, brain and abdomen with the DELSET method. CONCLUSION The DELSET method enables simple and accurate SNR quantification. This practical method is applicable to in vivo parallel imaging. Advances in knowledge: Practical SNR quantification based on the DELSET method is feasible for application in MRI systems used clinically.
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Affiliation(s)
- Naoki Ohno
- 1 Faculty of Health Sciences, Institute of Medical, Pharmaceutical and Health Sciences, Kanazawa University , Ishikawa, Kanazawa , Japan
| | - Tosiaki Miyati
- 1 Faculty of Health Sciences, Institute of Medical, Pharmaceutical and Health Sciences, Kanazawa University , Ishikawa, Kanazawa , Japan
| | - Yoshiaki Niwa
- 1 Faculty of Health Sciences, Institute of Medical, Pharmaceutical and Health Sciences, Kanazawa University , Ishikawa, Kanazawa , Japan
| | - Hirohito Kan
- 2 Department of Radiology, Nagoya City University Hospital , Nagoya, Aichi , Japan
| | - Shota Ishida
- 1 Faculty of Health Sciences, Institute of Medical, Pharmaceutical and Health Sciences, Kanazawa University , Ishikawa, Kanazawa , Japan
| | - Harumasa Kasai
- 2 Department of Radiology, Nagoya City University Hospital , Nagoya, Aichi , Japan
| | - Yuta Shibamoto
- 2 Department of Radiology, Nagoya City University Hospital , Nagoya, Aichi , Japan
| | - Toshifumi Gabata
- 3 Department of Radiology, Kanazawa University Hospital , Kanazawa, Ishikawa , Japan
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Time-of-Flight Magnetic Resonance Angiography With Sparse Undersampling and Iterative Reconstruction. Invest Radiol 2016; 51:372-8. [DOI: 10.1097/rli.0000000000000221] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
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Zhang M, Qin W, Piao Y, Guo D, Zhu Z, Tian X, Li K, Yu C. Longitudinal three-dimensional-T2WI-SPACE study on wallerian degeneration in cat corticospinal tract and underlying pathology changes. J Magn Reson Imaging 2015. [PMID: 26218829 DOI: 10.1002/jmri.24876] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
PURPOSE To investigate the feasibility of T2W-SPACE technique in early detection of WD, the signal evolutions of degenerated corticospinal tract (CST) on T2W-SPACE, and their underlying pathological changes. MATERIALS AND METHODS The WD model of the CST was established in 23 cats through excision of cortical origins of the tract. Eight cats were scanned with the T2W-SPACE technique at 8 sequential time points, i.e. 0 (before modeling), 2, 4, 6, 8, 10, 20 and 30 days after modeling, and then they were pathologically examined. The remaining 15 cats (3 per group) also underwent pathological examination at 2, 4, 6, 10 and 20 days after modeling, respectively. The ratios of T2 signal intensity (rT2s) between the affected and unaffected sides of CST were analyzed. RESULTS During the first 4 days, SPACE could not detect any significant changes of the affected CST, although axonal degeneration was pathologically observed at the second day. From 6 to 10 days, the rT2s decreased monotonously, which is corresponded to histological findings of myelin degeneration and phagocyte proliferation. From 10 to 20 days, rT2s kept relatively stable at a low level and started to recover after that; the pathological changes of this period was characterized by marked phagocytizing activities. CONCLUSION SPACE technique can detect Wallerian degeneration at an early stage, and the signal evolution is consistent with the pathological processes.
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Affiliation(s)
- Min Zhang
- Department of Radiology, Xuanwu Hospital, Capital Medical University, Beijing, China.,Beijing Key Laboratory of Magnetic Resonance Imaging and Brain Informatics, Beijing, China
| | - Wen Qin
- Department of Radiology, Tianjin Medical University General Hospital, Tianjin, China
| | - Yueshan Piao
- Department of Pathology, Xuanwu Hospital, Capital Medical University, Beijing, China
| | - Deyu Guo
- Department of Experimental Animal, Xuanwu Hospital, Capital Medical University, Beijing, China
| | - Zixin Zhu
- Department of Experimental Animal, Xuanwu Hospital, Capital Medical University, Beijing, China
| | - Xin Tian
- Department of Experimental Animal, Xuanwu Hospital, Capital Medical University, Beijing, China
| | - Kuncheng Li
- Department of Radiology, Xuanwu Hospital, Capital Medical University, Beijing, China.,Beijing Key Laboratory of Magnetic Resonance Imaging and Brain Informatics, Beijing, China
| | - Chunshui Yu
- Department of Radiology, Tianjin Medical University General Hospital, Tianjin, China
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Deborah AH, Karima S. Hemodynamic imaging of the auditory cortex. HANDBOOK OF CLINICAL NEUROLOGY 2015; 129:257-75. [PMID: 25726274 DOI: 10.1016/b978-0-444-62630-1.00015-9] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/22/2023]
Abstract
Over the past 20 years or so, functional magnetic resonance imaging (fMRI) has proven to be an influential tool for measuring perceptual and cognitive processing non-invasively in the human brain. This article provides a brief yet comprehensive overview of this dominant method for human auditory neuroscience, providing the reader with knowledge about the practicalities of using this technique to assess central auditory coding. Key learning objectives include developing an understanding of the basic MR physics underpinning the technique, the advantage of auditory fMRI over other current neuroimaging alternatives, and highlighting some of the practical considerations involved in setting up, running, and analyzing an auditory fMRI experiment. The future utility of fMRI and anticipated technical developments is also briefly evaluated. Throughout the review, key concepts are illustrated using specific author examples, with particular emphasis on fMRI findings that address questions pertaining to basic sound coding (such as frequency and pitch).
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Affiliation(s)
- Ann Hall Deborah
- National Institute for Health Research, Nottingham Hearing Biomedical Research Unit, University of Nottingham, Nottingham, UK.
| | - Susi Karima
- Division of Psychology, School of Social Sciences, Nottingham Trent University, Nottingham, UK
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Franke P, Markl M, Heinzelmann S, Vaith P, Bürk J, Langer M, Geiger J. Evaluation of a 32-channel versus a 12-channel head coil for high-resolution post-contrast MRI in giant cell arteritis (GCA) at 3T. Eur J Radiol 2014; 83:1875-80. [DOI: 10.1016/j.ejrad.2014.06.022] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2014] [Accepted: 06/24/2014] [Indexed: 10/25/2022]
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Yu J, Agarwal H, Stuber M, Schär M. Practical signal-to-noise ratio quantification for sensitivity encoding: application to coronary MR angiography. J Magn Reson Imaging 2011; 33:1330-40. [PMID: 21591001 DOI: 10.1002/jmri.22571] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
PURPOSE To develop and evaluate a practical method for the quantification of signal-to-noise ratio (SNR) on coronary MR angiograms (MRA) acquired with parallel imaging. MATERIALS AND METHODS To quantify the spatially varying noise due to parallel imaging reconstruction, a new method has been implemented incorporating image data acquisition followed by a fast noise scan during which radiofrequency pulses, cardiac triggering and navigator gating are disabled. The performance of this method was evaluated in a phantom study where SNR measurements were compared with those of a reference standard (multiple repetitions). Subsequently, SNR of myocardium and posterior skeletal muscle was determined on in vivo human coronary MRA. RESULTS In a phantom, the SNR measured using the proposed method deviated less than 10.1% from the reference method for small geometry factors (≤2). In vivo, the noise scan for a 10 min coronary MRA acquisition was acquired in 30 s. Higher signal and lower SNR, due to spatially varying noise, were found in myocardium compared with posterior skeletal muscle. CONCLUSION SNR quantification based on a fast noise scan is a validated and easy-to-use method when applied to three-dimensional coronary MRA obtained with parallel imaging as long as the geometry factor remains low.
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Affiliation(s)
- Jing Yu
- Department of Biomedical Engineering, Johns Hopkins University, Baltimore, Maryland 21287, USA
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Küper M, Dimitrova A, Thürling M, Maderwald S, Roths J, Elles HG, Gizewski ER, Ladd ME, Diedrichsen J, Timmann D. Evidence for a motor and a non-motor domain in the human dentate nucleus--an fMRI study. Neuroimage 2010; 54:2612-22. [PMID: 21081171 DOI: 10.1016/j.neuroimage.2010.11.028] [Citation(s) in RCA: 81] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2010] [Revised: 10/21/2010] [Accepted: 11/08/2010] [Indexed: 11/16/2022] Open
Abstract
Dum and Strick (J. Neurophysiol. 2003; 89, 634-639) proposed a division of the cerebellar dentate nucleus into a "motor" and "non-motor" area based on anatomical data in the monkey. We asked the question whether motor and non-motor domains of the dentate can be found in humans using functional magnetic resonance imaging (fMRI). Therefore dentate activation was compared in motor and cognitive tasks. Young, healthy participants were tested in a 1.5 T MRI scanner. Data from 13 participants were included in the final analysis. A block design was used for the experimental conditions. Finger tapping of different complexities served as motor tasks, while cognitive testing included a verbal working memory and a visuospatial task. To further confirm motor-related dentate activation, a simple finger movement task was tested in a supplementary experiment using ultra-highfield (7 T) fMRI in 23 participants. For image processing, a recently developed region of interest (ROI) driven normalization method of the deep cerebellar nuclei was used. Dorso-rostral dentate nucleus activation was associated with motor function, whereas cognitive tasks led to prominent activation of the caudal nucleus. The visuospatial task evoked activity bilaterally in the caudal dentate nucleus, whereas verbal working memory led to activation predominantly in the right caudal dentate. These findings are consistent with Dum and Strick's anatomical findings in the monkey.
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Affiliation(s)
- M Küper
- Department of Neurology, University of Duisburg-Essen, Essen, Germany.
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Tang G, Liu Y, Li W, Yao J, Li B, Li P. Optimization of b value in diffusion-weighted MRI for the differential diagnosis of benign and malignant vertebral fractures. Skeletal Radiol 2007; 36:1035-41. [PMID: 17786434 DOI: 10.1007/s00256-007-0358-7] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/12/2006] [Revised: 06/17/2007] [Accepted: 07/08/2007] [Indexed: 02/02/2023]
Abstract
OBJECTIVE The objective was to explore the optimal b value in diffusion-weighted imaging (DWI) of MRI for differential diagnosis of benign and malignant vertebral fractures. MATERIALS AND METHODS Thirty-four consecutive patients with vertebral compression fractures underwent sagittal diffusion-weighted imaging (DWI) with different b values. The group included 14 patients with 18 benign vertebral fractures due to osteoporosis and/or trauma and 20 patients with 27 malignant vertebral fractures due to malignancy. The quality of the images was analyzed qualitatively on a three-point scale and quantitatively by measurement of the signal-to-noise ratio (SNR). Apparent diffusion coefficient (ADC) values were also calculated. RESULTS Smaller b values correlated with better DW image quality. We found significant differences in the qualitative points values among the DW images with different b values (F=302.18, p<0.001). The mean SNR of the images ranged from 21.75+/-3.64 at a b value of 0 s/mm2 to 5.31+/-3.17 at a b value of 800 s/mm2. The SNR of DWI with a b value of 300 s/mm2 (18.62+/-2.47) was significantly different from that with other b values (p<0.01). The mean combined ADC values of malignant fractures were significantly lower than those of benign ones on DWI with a b value of 300 s/mm2 (t=9.097, p<0.01). Four cases of benign vertebral fractures were misdiagnosed as being malignant when b values of 0 s/mm2 and 100 s/mm2 were used. CONCLUSIONS When DWI with multiple b values is used to differentiate benign from malignant vertebral compression fractures, b values within the range of around 300 s/mm2 are recommended, taking into account both SNR and diffusion weighting of water molecules.
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Affiliation(s)
- Guangyu Tang
- Department of Radiology, Affiliated Tenth People's Hospital of Tongji University, Shanghai 200072, China.
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Dimitrova A, de Greiff A, Schoch B, Gerwig M, Frings M, Gizewski ER, Timmann D. Activation of cerebellar nuclei comparing finger, foot and tongue movements as revealed by fMRI. Brain Res Bull 2006; 71:233-41. [PMID: 17113951 DOI: 10.1016/j.brainresbull.2006.09.015] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/14/2006] [Revised: 08/16/2006] [Accepted: 09/07/2006] [Indexed: 11/27/2022]
Abstract
The aim of the present study was to compare possible activation of the interposed and dentate cerebellar nuclei during finger, foot and tongue movements using functional magnetic resonance imaging (fMRI). Nineteen healthy control subjects performed sequential finger and repetitive tongue and foot movement tasks. Thin slices (2.5mm) were acquired of the cerebellar region containing the cerebellar nuclei with high spatial resolution (matrix size 128 x 128 x 10) using a Siemens 1.5T Sonata system. Use of an eight channel head coil provided better signal-to-noise-ratio compared to standard head coils. Only data of those 12 subjects were included in final statistical analysis, who showed significant activation of the cerebellar nuclei at least in one task. Cortical activations of the superior cerebellum were found in accordance to the known somatotopy of the human cerebellar cortex. Nuclear activations were most significant in the sequential finger movement task. Both interposed nuclei and ipsilateral dentate nucleus were activated. Dentate activation was present in the more caudal parts of both the dorsal and ventral nucleus. Activation overlapped with motor and non-motor domains of the dentate nucleus described by Dum and Strick [R.P. Dum, P.L. Strick, An unfolded map of the cerebellar dentate nucleus and its projections to the cerebral cortex, J. Neurophysiol. 89 (2003) 634-639] based on anatomical data in monkey. Tongue movement related activations were less extensive and overlapped with activations of caudal parts of the dentate nucleus in the finger movement task. No nuclear activation was seen following foot movements. The present findings show that both interposed and dentate nuclei are involved in sequential finger movements in humans. Interposed nucleus likely contributes to movement performance. Although no direct conclusions could be drawn based on the present data, different parts of the dentate nucleus may contribute to movement performance, planning and possible non-motor parts of the task.
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Affiliation(s)
- A Dimitrova
- Department of Neurology, University of Duisburg-Essen, Germany
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Klein JC, Behrens TEJ, Robson MD, Mackay CE, Higham DJ, Johansen-Berg H. Connectivity-based parcellation of human cortex using diffusion MRI: Establishing reproducibility, validity and observer independence in BA 44/45 and SMA/pre-SMA. Neuroimage 2006; 34:204-11. [PMID: 17023184 DOI: 10.1016/j.neuroimage.2006.08.022] [Citation(s) in RCA: 146] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/25/2006] [Revised: 08/11/2006] [Accepted: 08/18/2006] [Indexed: 11/17/2022] Open
Abstract
The identification of specialized, functional regions of the human cortex is a vital precondition for neuroscience and clinical neurosurgery. Functional imaging modalities are used for their delineation in living subjects, but these methods rely on subject cooperation, and many regions of the human brain cannot be activated specifically. Diffusion tractography is a novel tool to identify such areas in the human brain, utilizing underlying white matter pathways to separate regions of differing specialization. We explore the reproducibility, generalizability and validity of diffusion tractography-based localization in four functional areas across subjects, timepoints and scanners, and validate findings against fMRI and post-mortem cytoarchitectonic data. With reproducibility across modalities, clustering methods, scanners, timepoints, and subjects in the order of 80-90%, we conclude that diffusion tractography represents a useful and objective tool for parcellation of the human cortex into functional regions, enabling studies into individual functional anatomy even when there are no specific activation paradigms available.
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Affiliation(s)
- Johannes C Klein
- Oxford Centre for Functional Magnetic Resonance Imaging of the Brain, University of Oxford, John Radcliffe Hospital, Oxford OX3 9DU, UK
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Maderwald S, Uffmann K, Galbán CJ, de Greiff A, Ladd ME. Accelerating MR elastography: A multiecho phase-contrast gradient-echo sequence. J Magn Reson Imaging 2006; 23:774-80. [PMID: 16570244 DOI: 10.1002/jmri.20570] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
PURPOSE To demonstrate the feasibility of using a multiecho phase-contrast (PC) gradient-echo sequence with motion-sensitizing gradient (MSG) to accelerate MR elastography (MRE) acquisitions in comparison to single-echo PC sequences. MATERIALS AND METHODS The sequence was implemented and compared with a conventional single-echo sequence as the standard of reference in both agarose phantoms and in vivo in the biceps of three healthy volunteers. For reconstruction of the elasticity modulus, a local frequency estimation (LFE) algorithm was used. ETL factors of 1-16 were evaluated. RESULTS Phantom experiments demonstrated excellent consistency between single-echo and multiecho measurements in terms of wave equivalency, SNR, and reconstructed shear modulus. Additionally, the in vivo MRE examinations showed an excellent correspondence to the single-echo results. Minor loss of wave amplitude was observed at higher ETL factors. CONCLUSION The results demonstrate that a multiecho sequence is suitable for accelerating MRE in nearly homogeneous tissue, such as muscle. It provides equivalent elasticity values in a significantly reduced scan time compared to a single-echo sequence. The maximum achievable ETL factor must be individually determined for the target tissue.
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Affiliation(s)
- Stefan Maderwald
- Department of Diagnostic and Interventional Radiology and Neuroradiology, University Hospital Essen, Essen, Germany.
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Wattjes MP, Lutterbey GG, Harzheim M, Gieseke J, Träber F, Klotz L, Klockgether T, Schild HH. Higher sensitivity in the detection of inflammatory brain lesions in patients with clinically isolated syndromes suggestive of multiple sclerosis using high field MRI: an intraindividual comparison of 1.5 T with 3.0 T. Eur Radiol 2006; 16:2067-73. [PMID: 16649033 DOI: 10.1007/s00330-006-0195-4] [Citation(s) in RCA: 67] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/26/2005] [Revised: 01/16/2006] [Accepted: 02/03/2006] [Indexed: 10/24/2022]
Abstract
The purpose of this study was to determine the sensitivities in the detection of inflammatory lesions in patients with clinically isolated syndromes suggestive of multiple sclerosis at 3.0 T and 1.5 T. MR imaging of 40 patients at both field strengths was performed in separate sessions including contiguous axial slices of T2 turbo spin-echo (T2 TSE), fluid-attenuated-inversion-recovery (FLAIR) and pre- and postcontrast T1 spin-echo (T1 SE). Inflammatory lesions > 3 mm in size were counted and categorized according to their anatomic location. Lesion conspicuity was assessed on a five-point scale. At 3.0 T, 13% more white matter lesions could be identified on the FLAIR sequence and on the T2 TSE sequence. Compared to 1.5 T 7.5% more contrast-enhancing lesions were detected at 3.0 T. The higher detection rate at 3.0 T was significant for the infratentorial (p = 0.02) and juxtacortical (p < 0.01) region on the FLAIR as well as for the infratentorial (p = 0.03), juxtacortical (p = 0.02) and periventricular (p = 0.03) region on the T2 TSE sequence. The lesion conspicuity was significantly better at 3.0 T for FLAIR and T2 TSE sequences (p<0.01; p=0.01). In conclusion, high-field MRI at 3.0 T provides a significantly higher detection rate of inflammatory brain lesions especially in the infratentorial, juxtacortical and periventricular anatomic region.
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Affiliation(s)
- Mike P Wattjes
- Department of Radiology, University of Bonn, Sigmund-Freud-Strasse 25, 53105, Bonn, Germany.
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