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Results: 1 to 10 of 49

Publication Record


Subject-specific regional measures of water diffusion are associated with impairment in chronic spinal cord injury.
Choe AS, Sadowsky CL, Smith SA, van Zijl PCM, Pekar JJ, Belegu V
(2017) Neuroradiology 59: 747-758
MeSH Terms: Adult, Aged, Anisotropy, Biomarkers, Body Water, Chronic Disease, Female, Humans, Image Interpretation, Computer-Assisted, Injury Severity Score, Male, Middle Aged, Sensitivity and Specificity, Spinal Cord Injuries
Show Abstract · Added April 10, 2019
PURPOSE - We aimed to identify non-invasive imaging parameters that can serve as biomarkers for the integrity of the spinal cord, which is paramount to neurological function. Diffusion tensor imaging (DTI) indices are sensitive to axonal and myelin damage, and have strong potential to serve as such biomarkers. However, averaging DTI indices over large regions of interest (ROIs), a common approach to analyzing the images of injured spinal cord, leads to loss of subject-specific information. We investigated if DTI-tractography-driven, subject-specific demarcation approach can yield measures that are more specific to impairment.
METHODS - In 18 individuals with chronic spinal cord injury (SCI), subject-specific demarcation of the injury region was performed using DTI tractography, which yielded three regions relative to injury (RRI; regions superior to, at, and below injury epicenter). DTI indices averaged over each RRI were correlated with measures of residual motor and sensory function, obtained using the International Standard of Neurological Classification for Spinal Cord Injury (ISNCSCI).
RESULTS - Total ISNCSCI score (ISNCSCI-tot; sum of ISNCSCI motor and sensory scores) was significantly (p < 0.05) correlated with fractional anisotropy and axial and radial diffusivities. ISNCSCI-tot showed strongest correlation with indices measured from the region inferior to the injury epicenter (IRRI), the degree of which exceeded that of those measured from the entire cervical cord-suggesting contribution from Wallerian degeneration.
CONCLUSION - DTI tractography-driven, subject-specific injury demarcation approach provided measures that were more specific to impairment. Notably, DTI indices obtained from the IRRI region showed the highest specificity to impairment, demonstrating their strong potential as biomarkers for the SCI severity.
0 Communities
1 Members
0 Resources
MeSH Terms
30-Second bound and pore water concentration mapping of cortical bone using 2D UTE with optimized half-pulses.
Manhard MK, Harkins KD, Gochberg DF, Nyman JS, Does MD
(2017) Magn Reson Med 77: 945-950
MeSH Terms: Algorithms, Body Water, Cortical Bone, Humans, Image Enhancement, Image Interpretation, Computer-Assisted, Magnetic Resonance Imaging, Porosity, Reproducibility of Results, Sensitivity and Specificity, Signal Processing, Computer-Assisted
Show Abstract · Added February 27, 2017
PURPOSE - MRI of cortical bone has the potential to offer new information about fracture risk. Current methods are typically performed with 3D acquisitions, which suffer from long scan times and are generally limited to extremities. This work proposes using 2D UTE with half pulses for quantitatively mapping bound and pore water in cortical bone.
METHODS - Half-pulse 2D UTE methods were implemented on a 3T Philips Achieva scanner using an optimized slice-select gradient waveform, with preparation pulses to selectively image bound or pore water. The 2D methods were quantitatively compared with previously implemented 3D methods in the tibia in five volunteers.
RESULTS - The mean difference between bound and pore water concentration acquired from 3D and 2D sequences was 0.6 and 0.9 mol H/L (3 and 12%, respectively). While 2D pore water methods tended to slightly overestimate concentrations relative to 3D methods, differences were less than scan-rescan uncertainty and expected differences between healthy and fracture-prone bones.
CONCLUSION - Quantitative bound and pore water concentration mapping in cortical bone can be accelerated by 2 orders of magnitude using 2D protocols with optimized half-pulse excitation. Magn Reson Med 77:945-950, 2017. © 2017 International Society for Magnetic Resonance in Medicine.
© 2017 International Society for Magnetic Resonance in Medicine.
2 Communities
1 Members
0 Resources
11 MeSH Terms
Impact of transcytolemmal water exchange on estimates of tissue microstructural properties derived from diffusion MRI.
Li H, Jiang X, Xie J, Gore JC, Xu J
(2017) Magn Reson Med 77: 2239-2249
MeSH Terms: Animals, Artifacts, Body Water, Cell Line, Tumor, Cell Membrane, Cell Membrane Permeability, Diffusion Magnetic Resonance Imaging, Mice, Neoplasms, Experimental, Reproducibility of Results, Sensitivity and Specificity
Show Abstract · Added November 1, 2016
PURPOSE - To investigate the influence of transcytolemmal water exchange on estimates of tissue microstructural parameters derived from diffusion MRI using conventional PGSE and IMPULSED methods.
METHODS - Computer simulations were performed to incorporate a broad range of intracellular water life times τ (50-∞ ms), cell diameters d (5-15 μm), and intrinsic diffusion coefficient D (0.6-2 μm /ms) for different values of signal-to-noise ratio (SNR) (10 to 50). For experiments, murine erythroleukemia (MEL) cancer cells were cultured and treated with saponin to selectively change cell membrane permeability. All fitted microstructural parameters from simulations and experiments in vitro were compared with ground-truth values.
RESULTS - Simulations showed that, for both PGSE and IMPULSED methods, cell diameter d can be reliably fit with sufficient SNR (≥ 50), whereas intracellular volume fraction f is intrinsically underestimated due to transcytolemmal water exchange. D can be reliably fit only with sufficient SNR and using the IMPULSED method with short diffusion times. These results were confirmed with those obtained in the cell culture experiments in vitro.
CONCLUSION - For the sequences and models considered in this study, transcytolemmal water exchange has minor effects on the fittings of d and D with physiologically relevant membrane permeabilities if the SNR is sufficient (> 50), but f is intrinsically underestimated. Magn Reson Med 77:2239-2249, 2017. © 2016 International Society for Magnetic Resonance in Medicine.
© 2016 International Society for Magnetic Resonance in Medicine.
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2 Members
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11 MeSH Terms
Multisite, multivendor validation of the accuracy and reproducibility of proton-density fat-fraction quantification at 1.5T and 3T using a fat-water phantom.
Hernando D, Sharma SD, Aliyari Ghasabeh M, Alvis BD, Arora SS, Hamilton G, Pan L, Shaffer JM, Sofue K, Szeverenyi NM, Welch EB, Yuan Q, Bashir MR, Kamel IR, Rice MJ, Sirlin CB, Yokoo T, Reeder SB
(2017) Magn Reson Med 77: 1516-1524
MeSH Terms: Adipose Tissue, Body Water, Equipment Design, Equipment Failure Analysis, Magnetic Resonance Imaging, Phantoms, Imaging, Protons, Reproducibility of Results, Sensitivity and Specificity
Show Abstract · Added April 18, 2016
PURPOSE - To evaluate the accuracy and reproducibility of quantitative chemical shift-encoded (CSE) MRI to quantify proton-density fat-fraction (PDFF) in a fat-water phantom across sites, vendors, field strengths, and protocols.
METHODS - Six sites (Philips, Siemens, and GE Healthcare) participated in this study. A phantom containing multiple vials with various oil/water suspensions (PDFF:0%-100%) was built, shipped to each site, and scanned at 1.5T and 3T using two CSE protocols per field strength. Confounder-corrected PDFF maps were reconstructed using a common algorithm. To assess accuracy, PDFF bias and linear regression with the known PDFF were calculated. To assess reproducibility, measurements were compared across sites, vendors, field strengths, and protocols using analysis of covariance (ANCOVA), Bland-Altman analysis, and the intraclass correlation coefficient (ICC).
RESULTS - PDFF measurements revealed an overall absolute bias (across sites, field strengths, and protocols) of 0.22% (95% confidence interval, 0.07%-0.38%) and R  > 0.995 relative to the known PDFF at each site, field strength, and protocol, with a slope between 0.96 and 1.02 and an intercept between -0.56% and 1.13%. ANCOVA did not reveal effects of field strength (P = 0.36) or protocol (P = 0.19). There was a significant effect of vendor (F = 25.13, P = 1.07 × 10 ) with a bias of -0.37% (Philips) and -1.22% (Siemens) relative to GE Healthcare. The overall ICC was 0.999.
CONCLUSION - CSE-based fat quantification is accurate and reproducible across sites, vendors, field strengths, and protocols. Magn Reson Med 77:1516-1524, 2017. © 2016 International Society for Magnetic Resonance in Medicine.
© 2016 International Society for Magnetic Resonance in Medicine.
1 Communities
1 Members
0 Resources
9 MeSH Terms
R1 correction in amide proton transfer imaging: indication of the influence of transcytolemmal water exchange on CEST measurements.
Li H, Li K, Zhang XY, Jiang X, Zu Z, Zaiss M, Gochberg DF, Gore JC, Xu J
(2015) NMR Biomed 28: 1655-62
MeSH Terms: Amides, Animals, Artifacts, Biological Transport, Active, Body Water, Brain Neoplasms, Cell Line, Tumor, Extracellular Fluid, Humans, Intracellular Fluid, Magnetic Resonance Spectroscopy, Molecular Imaging, Protons, Rats, Rats, Inbred F344, Reproducibility of Results, Sensitivity and Specificity, Transcytosis
Show Abstract · Added October 28, 2015
Amide proton transfer (APT) imaging may potentially detect mobile proteins/peptides non-invasively in vivo, but its specificity may be reduced by contamination from other confounding effects such as asymmetry of non-specific magnetization transfer (MT) effects and spin-lattice relaxation with rate R1 (=1/T1). Previously reported spillover, MT and R1 correction methods were based on a two-pool model, in which the existence of multiple water compartments with heterogeneous relaxation properties in real tissues was ignored. Such simple models may not adequately represent real tissues, and thus such corrections may be unreliable. The current study investigated the effectiveness and accuracy of correcting for R1 in APT imaging via simulations and in vivo experiments using tumor-bearing rats subjected to serial injections of Gd-DTPA that produced different tissue R1 values in regions of blood-brain-barrier breakdown. The results suggest that conventional measurements of APT contrast (such as APT* and MTRasym ) may be significantly contaminated by R1 variations, while the R1 -corrected metric AREX* was found to be relatively unaffected by R1 changes over a broad range (0.4-1 Hz). Our results confirm the importance of correcting for spin-lattice relaxation effects in quantitative APT imaging, and demonstrate the reliability of using the observed tissue R1 for corrections to obtain more specific and accurate measurements of APT contrast in vivo. The results also indicate that, due to relatively fast transcytolemmal water exchange, the influence of intra- and extracellular water compartments on CEST measurements with seconds long saturation time may be ignored in tumors.
Copyright © 2015 John Wiley & Sons, Ltd.
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2 Members
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18 MeSH Terms
Influence of water compartmentation and heterogeneous relaxation on quantitative magnetization transfer imaging in rodent brain tumors.
Li K, Li H, Zhang XY, Stokes AM, Jiang X, Kang H, Quarles CC, Zu Z, Gochberg DF, Gore JC, Xu J
(2016) Magn Reson Med 76: 635-44
MeSH Terms: Animals, Body Water, Cell Line, Tumor, Computer Simulation, Image Enhancement, Image Interpretation, Computer-Assisted, Magnetic Fields, Male, Models, Biological, Neoplasms, Experimental, Rats, Rats, Inbred F344, Reproducibility of Results, Sensitivity and Specificity
Show Abstract · Added September 25, 2015
PURPOSE - The goal of this study was to investigate the influence of water compartmentation and heterogeneous relaxation properties on quantitative magnetization transfer (qMT) imaging in tissues, and in particular whether a two-pool model is sufficient to describe qMT data in brain tumors.
METHODS - Computer simulations and in vivo experiments with a series of qMT measurements before and after injection of Gd-DTPA were performed. Both off-resonance pulsed saturation (pulsed) and on-resonance selective inversion recovery (SIR) qMT methods were used, and all data were fit with a two-pool model only.
RESULTS - Simulations indicated that a two-pool fitting of four-pool data yielded accurate measures of pool size ratio (PSR) of macromolecular versus free water protons when there were fast transcytolemmal exchange and slow R1 recovery. The fitted in vivo PSR of both pulsed and SIR qMT methods showed no dependence on R1 variations caused by different concentrations of Gd-DTPA during wash-out, whereas the fitted kex (magnetization transfer exchange rate) changed significantly with R1 .
CONCLUSION - A two-pool model provides reproducible estimates of PSR in brain tumors independent of relaxation properties in the presence of relatively fast transcytolemmal exchange, whereas estimates of kex are biased by relaxation variations. In addition, estimates of PSR in brain tumors using the pulsed and SIR qMT methods agree well with one another. Magn Reson Med 76:635-644, 2016. © 2015 Wiley Periodicals, Inc.
© 2015 Wiley Periodicals, Inc.
0 Communities
3 Members
0 Resources
14 MeSH Terms
Whole-body continuously moving table fat-water MRI with dynamic B0 shimming at 3 Tesla.
Sengupta S, Smith DS, Gifford A, Welch EB
(2016) Magn Reson Med 76: 183-90
MeSH Terms: Adipose Tissue, Adult, Algorithms, Beds, Body Water, Female, Humans, Image Enhancement, Image Interpretation, Computer-Assisted, Magnetic Resonance Imaging, Male, Patient Positioning, Reproducibility of Results, Sensitivity and Specificity, Whole Body Imaging
Show Abstract · Added February 22, 2016
PURPOSE - The purpose of this work was to develop a rapid and robust whole-body fat-water MRI (FWMRI) method using a continuously moving table (CMT) with dynamic field corrections at 3 Tesla.
METHODS - CMT FWMRI was developed at 3 Tesla with a multiecho golden angle (GA) radial trajectory and dynamic B0 field shimming. Whole-body imaging was performed with 4 echoes and superior-inferior coverage of 1.8 meters without shims in 90 s. 716 axial images were reconstructed with GA profile binning followed by B0 field map generation using fast three-point seeded region growing fat-water separation and slice-specific 0(th) and 1(st) order shim calculation. Slice-specific shims were applied dynamically in a repeated CMT FWMRI scan in the same session. The resulting images were evaluated for field homogeneity improvements and quality of fat-water separation with a whole-image energy optimized algorithm.
RESULTS - GA sampling allowed high quality whole-body FWMRI from multiecho CMT data. Dynamic B0 shimming greatly improved field homogeneity in the body and produced high quality water and fat only images as well as fat signal fraction and R2 * relaxivity maps.
CONCLUSION - A rapid and robust technique for whole-body fat-water quantification has been developed with CMT MRI with dynamic B0 field correction. Magn Reson Med 76:183-190, 2016. © 2015 Wiley Periodicals, Inc.
© 2015 Wiley Periodicals, Inc.
1 Communities
1 Members
0 Resources
15 MeSH Terms
Changes in skeletal collagen cross-links and matrix hydration in high- and low-turnover chronic kidney disease.
Allen MR, Newman CL, Chen N, Granke M, Nyman JS, Moe SM
(2015) Osteoporos Int 26: 977-85
MeSH Terms: Amino Acids, Animals, Arginine, Body Water, Bone Matrix, Bone and Bones, Collagen, Diaphyses, Disease Models, Animal, Femur, Lysine, Male, Rats, Renal Insufficiency, Chronic, Stress, Mechanical
Show Abstract · Added January 19, 2015
UNLABELLED - Chronic kidney disease (CKD) increases fracture risk. The results of this work point to changes in bone collagen and bone hydration as playing a role in bone fragility associated with CKD.
INTRODUCTION - Clinical data have documented a clear increase in fracture risk associated with chronic kidney disease (CKD). Preclinical studies have shown reductions in bone mechanical properties although the tissue-level mechanisms for these differences remain unclear. The goal of this study was to assess collagen cross-links and matrix hydration, two variables known to affect mechanical properties, in animals with either high- or low-turnover CKD.
METHODS - At 35 weeks of age (>75% reduction in kidney function), the femoral diaphysis of male Cy/+ rats with high or low bone turnover rates, along with normal littermate (NL) controls, were assessed for collagen cross-links (pyridinoline (Pyd), deoxypyridinoline (Dpd), and pentosidine (PE)) using a high-performance liquid chromatography (HPLC) assay as well as pore and bound water per volume (pw and bw) using a (1)H nuclear magnetic resonance (NMR) technique. Material-level biomechanical properties were calculated based on previously published whole bone mechanical tests.
RESULTS - Cortical bone from animals with high-turnover disease had lower Pyd and Dpd cross-link levels (-21% each), lower bw (-10%), higher PE (+71%), and higher pw (+46%) compared to NL. Animals with low turnover had higher Dpd, PE (+71%), and bw (+7%) along with lower pw (-60%) compared to NL. Both high- and low-turnover animals had reduced material-level bone toughness compared to NL animals as determined by three-point bending.
CONCLUSIONS - These data document an increase in skeletal PE with advanced CKD that is independent of bone turnover rate and inversely related to decline in kidney function. Although hydration changes occur in both high- and low-turnover disease, the data suggest that nonenzymatic collagen cross-links may be a key factor in compromised mechanical properties of CKD.
1 Communities
2 Members
0 Resources
15 MeSH Terms
Multi-parametric MRI characterization of healthy human thigh muscles at 3.0 T - relaxation, magnetization transfer, fat/water, and diffusion tensor imaging.
Li K, Dortch RD, Welch EB, Bryant ND, Buck AK, Towse TF, Gochberg DF, Does MD, Damon BM, Park JH
(2014) NMR Biomed 27: 1070-84
MeSH Terms: Adipose Tissue, Adult, Algorithms, Body Water, Diffusion Tensor Imaging, Humans, Image Interpretation, Computer-Assisted, Male, Multimodal Imaging, Muscle, Skeletal, Reproducibility of Results, Sensitivity and Specificity, Thigh
Show Abstract · Added July 31, 2014
Muscle diseases commonly have clinical presentations of inflammation, fat infiltration, fibrosis, and atrophy. However, the results of existing laboratory tests and clinical presentations are not well correlated. Advanced quantitative MRI techniques may allow the assessment of myo-pathological changes in a sensitive and objective manner. To progress towards this goal, an array of quantitative MRI protocols was implemented for human thigh muscles; their reproducibility was assessed; and the statistical relationships among parameters were determined. These quantitative methods included fat/water imaging, multiple spin-echo T2 imaging (with and without fat signal suppression, FS), selective inversion recovery for T1 and quantitative magnetization transfer (qMT) imaging (with and without FS), and diffusion tensor imaging. Data were acquired at 3.0 T from nine healthy subjects. To assess the repeatability of each method, the subjects were re-imaged an average of 35 days later. Pre-testing lifestyle restrictions were applied to standardize physiological conditions across scans. Strong between-day intra-class correlations were observed in all quantitative indices except for the macromolecular-to-free water pool size ratio (PSR) with FS, a metric derived from qMT data. Two-way analysis of variance revealed no significant between-day differences in the mean values for any parameter estimate. The repeatability was further assessed with Bland-Altman plots, and low repeatability coefficients were obtained for all parameters. Among-muscle differences in the quantitative MRI indices and inter-class correlations among the parameters were identified. There were inverse relationships between fractional anisotropy (FA) and the second eigenvalue, the third eigenvalue, and the standard deviation of the first eigenvector. The FA was positively related to the PSR, while the other diffusion indices were inversely related to the PSR. These findings support the use of these T1 , T2 , fat/water, and DTI protocols for characterizing skeletal muscle using MRI. Moreover, the data support the existence of a common biophysical mechanism, water content, as a source of variation in these parameters.
Copyright © 2014 John Wiley & Sons, Ltd.
1 Communities
4 Members
0 Resources
13 MeSH Terms
Sequence design and evaluation of the reproducibility of water-selective diffusion-weighted imaging of the breast at 3 T.
Zhu H, Arlinghaus LR, Whisenant JG, Li M, Gore JC, Yankeelov TE
(2014) NMR Biomed 27: 1030-6
MeSH Terms: Algorithms, Body Water, Breast, Breast Neoplasms, Diffusion Magnetic Resonance Imaging, Female, Humans, Image Interpretation, Computer-Assisted, Reproducibility of Results, Sensitivity and Specificity
Show Abstract · Added February 12, 2015
Diffusion measurements derived from breast MRI can be adversely affected by unwanted signals from abundant fatty tissues if they are not suppressed adequately. To minimize this undesired contribution, we designed and optimized a water-selective diffusion-weighted imaging (DWI) sequence, which relies on spectrally selective excitation on the water resonance, obviating the need for fat suppression. As this method is more complex than standard DWI methods, we also report a test-retest study to evaluate its reproducibility. In this study, a spectrally selective Gaussian pulse on water resonance was combined with a pair of slice-selective adiabatic refocusing pulses for water-only DWI. Field map-based shimming and manual determination of the center frequency were used for water selection. The selectivity of the excitation pulse was optimized by a spectrally selective spectroscopy sequence based on the same principles. A test-retest study of 10 volunteers in two separate visits was used to evaluate its reproducibility. Our results from all subjects showed high-quality diffusion-weighted images of the breast without fat contamination. Mean apparent diffusion coefficients for b = 0, 600 s/mm(2) and b = 50, 600 s/mm(2) all showed good reproducibility, as 95% confidence intervals of the apparent diffusion coefficients were 4 × 10(-5)  mm(2) /s and 5 × 10(-5)  mm(2) /s and repeatability values were 1.09 × 10(-4) and 1.31 × 10(-4) , respectively. In conclusion, water-selective DWI is a feasible alternative to standard methods of DWI based on fat suppression. The added complexity of the method does not compromise the reproducibility of diffusion measurements in the breast.
Copyright © 2014 John Wiley & Sons, Ltd.
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2 Members
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10 MeSH Terms