共查询到20条相似文献,搜索用时 31 毫秒
1.
Ligong Wang PhD Ravinder R. Regatte PhD 《Journal of magnetic resonance imaging : JMRI》2015,41(3):586-600
Magnetic resonance imaging (MRI) offers the direct visualization of the human musculoskeletal (MSK) system, especially all diarthrodial tissues including cartilage, bone, menisci, ligaments, tendon, hip, synovium, etc. Conventional MRI techniques based on T1‐ and T2‐weighted, proton density (PD) contrast are inconclusive in quantifying early biochemically degenerative changes in MSK system in general and articular cartilage in particular. In recent years, quantitative MR parameter mapping techniques have been used to quantify the biochemical changes in articular cartilage, with a special emphasis on evaluating joint injury, cartilage degeneration, and soft tissue repair. In this article we focus on cartilage biochemical composition, basic principles of T1ρ MRI, implementation of T1ρ pulse sequences, biochemical validation, and summarize the potential applications of the T1ρ MRI technique in MSK diseases including osteoarthritis (OA), anterior cruciate ligament (ACL) injury, and knee joint repair. Finally, we also review the potential advantages, challenges, and future prospects of T1ρ MRI for widespread clinical translation. J. Magn. Reson. Imaging 2015;41:586–600. © 2014 Wiley Periodicals, Inc. 相似文献
2.
Chenyang Wang Walter Witschey Mark A. Elliott Arijitt Borthakur Ravinder Reddy 《Magnetic resonance in medicine》2010,64(6):1721-1727
The aim of this study is to demonstrate T1ρ MRI's capability for measuring intervertebral disc osmotic pressure. Self‐coregistered sodium and T1ρ‐weighted MR images were acquired on ex vivo bovine intervertebral discs (N = 12) on a 3 T clinical MRI scanner. The sodium MR images were used to calculate effective nucleus pulposus fixed‐charge‐density (mean = 138.2 ± 27.6 mM) and subsequently osmotic pressure (mean = 0.53 ± 0.18 atm), whereas the T1ρ‐weighted images were used to compute T1ρ relaxation maps. A significant linear correlation (R = 0.56, P < 0.01) between nucleus pulposus fixed‐charge‐density and T1ρ relaxation time constant was observed. More importantly, a significant power correlation (R = 0.72, P < 0.01) between nucleus pulposus osmotic pressure as predicted by sodium MRI and T1ρ relaxation time constant was also observed. The current clinical method for assessing disc pressure is discography, which is an invasive procedure that has been shown to have negative effects on disc biomechanical and biochemical properties. In contrast, T1ρ MRI is noninvasive and can be easily implemented in a clinical setting due to its superior signal‐to‐noise ratio compared with sodium MRI. Therefore, T1ρ MRI may serve as a noninvasive clinical tool for the longitudinal evaluation of disc osmotic pressure. Magn Reson Med, 2010. © 2010 Wiley‐Liss, Inc. 相似文献
3.
Sarma V.S. Akella Ravinder R. Regatte Andrew J. Wheaton Arijitt Borthakur Ravinder Reddy 《Magnetic resonance in medicine》2004,52(5):1103-1109
The influence of radiofrequency (RF) spin‐lock pulse on the laminar appearance of articular cartilage in MR images was investigated. Spin‐lock MRI experiments were performed on bovine cartilage plugs on a 4.7 Tesla small‐bore MRI scanner, and on human knee cartilage in vivo on a 1.5 Tesla clinical scanner. When the normal to the surface of cartilage was parallel to B0, a typical laminar appearence was exhibited in T2‐weighted images of cartilage plugs, but was absent in T1ρ‐weighted images of the same plugs. At the “magic angle” orientation (when the normal to the surface of cartilage was 54.7° with respect to B0), neither the T2 nor the T1ρ images demonstrated laminae. At the same time, T1ρ values were greater than T2 at both orientations throughout the cartilage. T1ρ dispersion (i.e., the dependence of the relaxation rate on the spin‐lock frequency ω1) was observed, which reached a steady‐state value of close to 2 kHz in both parallel and magic‐angle orientations. These results suggest that residual dipolar interaction from motionally‐restricted water and relaxation processes, such as chemical exchange, contribute to T1ρ dispersion in cartilage. Further, one can reduce the laminar appearance in human articular cartilage by applying spin‐lock RF pulses, which may lead to a more accurate diagnosis of degenerative changes in cartilage. Magn Reson Med 52:1103–1109, 2004. © 2004 Wiley‐Liss, Inc. 相似文献
4.
Gabrielle Blumenkrantz Jin Zuo Xiaojuan Li John Kornak Thomas M. Link Sharmila Majumdar 《Magnetic resonance in medicine》2010,63(5):1193-1200
The purpose of this study is (1) to determine the correlation between T1ρ and T2 and degenerative grade in intervertebral discs using in vivo 3.0‐T MRI, and (2) to determine the association between T1ρ and T2 and clinical findings as quantified by the SF‐36 Questionnaire and Oswestry Disability Index. Sixteen subjects participated in this study, and each completed SF‐36 and Oswestry Disability Index questionnaires. MRI T1ρ and T2 mapping was performed to determine T1ρ (77 discs) and T2 (44 discs) in the nucleus of the intervertebral disc, and T2‐weighted images were acquired for Pfirrmann grading of disc degeneration. Pfirrmann grade was correlated with both T1ρ (r = ?0.84; P < 0.01) and T2 (r = ?0.61; P < 0.01). Mixed‐effects models demonstrate that only T1ρ was associated with clinical questionnaires (R2SF‐36 = 0.55, R2O.D.I. = 0.56; P < 0.05). Although the averaged values of T1ρ and T2 were significantly correlated, they presented differences in spatial distribution and dynamic range, thus suggesting different sensitivities to tissue composition. This study suggests that T1ρ may be sensitive to early degenerative changes (corroborating previous studies) and clinical symptoms in intervertebral disc degeneration. Magn Reson Med 63:1193–1200, 2010. © 2010 Wiley‐Liss, Inc. 相似文献
5.
Jiang Du Sheronda Statum Richard Znamirowski Graeme M. Bydder Christine B. Chung 《Magnetic resonance in medicine》2013,69(3):682-687
An ultrashort TE T1ρ sequence was used to measure T1ρ of the goat posterior cruciate ligament (n = 1) and human Achilles tendon specimens (n = 6) at a series of angles relative to the B0 field and spin‐lock field strengths to investigate the contribution of dipole–dipole interaction to T1ρ relaxation. Preliminary results showed a significant magic angle effect. T1ρ of the posterior cruciate ligament increased from 6.9 ± 1.3 ms at 0° to 36 ± 5 ms at 55° and then gradually reduced to 12 ± 3 ms at 90°. Mean T1ρ of the Achilles tendon increased from 5.5 ± 2.2 ms at 0° to 40 ± 5 ms at 55°. T1ρ dispersion study showed a significant T1ρ increase from 2.3 ± 0.9 ms to 11 ± 3 ms at 0° as the spin‐lock field strength increased from 150 Hz to 1 kHz, and from 30 ± 3 ms to 42 ± 4 ms at 55° as the spin‐lock field strength increased from 100 to 500 Hz. These results suggest that dipolar interaction is the dominant T1ρ relaxation mechanism in tendons and ligaments. Magn Reson Med, 2013. © 2012 Wiley Periodicals, Inc. 相似文献
6.
Yongxian Qian Ashley A. Williams Constance R. Chu Fernando E. Boada 《Magnetic resonance in medicine》2010,64(5):1426-1431
Disorganization of collagen fibers is a sign of early‐stage cartilage degeneration in osteoarthritic knees. Water molecules trapped within well‐organized collagen fibrils would be sensitive to collagen alterations. Multicomponent effective transverse relaxation (T2*) mapping with ultrashort echo time acquisitions is here proposed to probe short T2 relaxations in those trapped water molecules. Six human tibial plateau explants were scanned on a 3T MRI scanner using a home‐developed ultrashort echo time sequence with echo times optimized via Monte Carlo simulations. Time constants and component intensities of T2* decays were calculated at individual pixels, using the nonnegative least squares algorithm. Four T2*‐decay types were found: 99% of cartilage pixels having mono‐, bi‐, or nonexponential decay, and 1% showing triexponential decay. Short T2* was mainly in 1‐6 ms, while long T2* was ~22 ms. A map of decay types presented spatial distribution of these T2* decays. These results showed the technical feasibility of multicomponent T2* mapping on human knee cartilage explants. Magn Reson Med, 2010. © 2010 Wiley‐Liss, Inc. 相似文献
7.
Riccardo Lattanzi Christian Glaser Artem V. Mikheev Catherine Petchprapa David J. Mossa Soterios Gyftopoulos Henry Rusinek Michael Recht Daniel Kim 《Magnetic resonance in medicine》2011,66(2):348-355
Early detection of cartilage degeneration in the hip may help prevent onset and progression of osteoarthritis in young patients with femoroacetabular impingement. Delayed gadolinium‐enhanced MRI of cartilage is sensitive to cartilage glycosaminoglycan loss and could serve as a diagnostic tool for early cartilage degeneration. We propose a new high resolution 2D T1 mapping saturation–recovery pulse sequence with fast spin echo readout for delayed gadolinium‐enhanced magnetic resonance imaging of cartilage of the hip at 3 T. The proposed sequence was validated in a phantom and in 10 hips, using radial imaging planes, against a rigorous multipoint saturation–recovery pulse sequence with fast spin echo readout. T1 measurements by the two pulse sequences were strongly correlated (R2 > 0.95) and in excellent agreement (mean difference = ?8.7 ms; upper and lower 95% limits of agreement = 64.5 and ?81.9 ms, respectively). T1 measurements were insensitive to B1+ variation as large as 20%, making the proposed T1 mapping technique suitable for 3 T. Magn Reson Med, 2011. © 2011 Wiley‐Liss, Inc. 相似文献
8.
Xiaojuan Li Alex Pai Gabrielle Blumenkrantz Julio Carballido‐Gamio Thomas Link Benjamin Ma Michael Ries Sharmila Majumdar 《Magnetic resonance in medicine》2009,61(6):1310-1318
T1ρ and T2 relaxation time constants have been proposed to probe biochemical changes in osteoarthritic cartilage. This study aimed to evaluate the spatial correlation and distribution of T1ρ and T2 values in osteoarthritic cartilage. Ten patients with osteoarthritis (OA) and 10 controls were studied at 3T. The spatial correlation of T1ρ and T2 values was investigated using Z‐scores. The spatial variation of T1ρ and T2 values in patellar cartilage was studied in different cartilage layers. The distribution of these relaxation time constants was measured using texture analysis parameters based on gray‐level co‐occurrence matrices (GLCM). The mean Z‐scores for T1ρ and T2 values were significantly higher in OA patients vs. controls (P < 0.05). Regional correlation coefficients of T1ρ and T2 Z‐scores showed a large range in both controls and OA patients (0.2–0.7). OA patients had significantly greater GLCM contrast and entropy of T1ρ values than controls (P < 0.05). In summary, T1ρ and T2 values are not only increased but are also more heterogeneous in osteoarthritic cartilage. T1ρ and T2 values show different spatial distributions and may provide complementary information regarding cartilage degeneration in OA. Magn Reson Med, 2009. © 2009 Wiley‐Liss, Inc. 相似文献
9.
Quantitative cartilage degeneration associated with spontaneous osteoarthritis in a guinea pig model
Fenty MC Dodge GR Kassey VB Witschey WR Borthakur A Reddy R 《Journal of magnetic resonance imaging : JMRI》2012,35(4):891-898
Purpose:
To determine (i) the feasibility and intra‐ and inter‐scan reproducibility of T1ρ MRI in assessing cartilage degeneration in a guinea pig model with naturally occurring joint disease that closely mimics human osteoarthritis (OA), (ii) demonstrate the sensitivity of T1ρ MRI in assessing the age dependent cartilage degeneration in OA progression as compared to histopathological changes.Materials and Methods:
Duncan‐Hartley guinea pigs were obtained at various ages and maintained under an IACUC approved protocol. The left hind stifle joint was imaged using T1ρ MRI on a 9.4 Tesla Varian horizontal 20 cm bore scanner using a custom surface coil. Reproducibility of T1ρ MRI was assessed using 4‐month‐old guinea pigs (N = 3). Three age cohorts; 3 month (N = 8), 5 month (N = 6), and 9 month (N = 5), were used to determine the age‐dependent osteoarthritic changes as measured by T1ρ MRI. Validation of age‐dependent cartilage degeneration was confirmed by histology and Safranin‐O staining.Results:
T1ρ values obtained in the cartilage of the stifle joint in guinea pigs were highly reproducible with an inter‐scan mean coefficient of variation (CV) of 6.57% and a maximum intra‐scan CV of 9.29%. Mean cartilage T1ρ values in animals with late stage cartilage degeneration were 56.3–56.9 ms (5–9 month cohorts) were both significantly (P < 0.01) higher than that obtained from 3‐month‐old cohort (44 ms) demonstrating an age‐dependent variation. T1ρ was shown to be significantly greater than T2. T1ρ dispersion was observed in this animal model for the first time showing an increase of 45% between 500 Hz and 1500 Hz spin‐locking frequency. Cartilage thickness measurements were calculated from single mid‐coronal histology sections from same animals used for T1ρ MRI. Thickness calculations showed insignificant differences between 3‐ and 5‐month cohorts and was significantly decreased by 9 months of age (P < 0.01). A moderate correlation (R2 = 0.45) existed between T1ρ values and signal intensity of Safranin‐O stain.Conclusion:
The data presented demonstrate that T1ρ MRI is highly reproducible in this spontaneous model of OA and may serve as a noninvasive tool to characterize joint cartilage degeneration during OA. Age‐dependent changes, verified with histological measurements of proteoglycan loss, correlated with T1ρ across different age groups. T1ρ has adequate dynamic range and is sensitive to detect and track the progression of cartilage degeneration in the guinea pig model before gross anatomical changes such as cartilage thinning has occurred. This study presents a technological advancement that would permit longitudinal studies of evaluating disease‐modifying therapies useful for treating human OA. J. Magn. Reson. Imaging 2012;35:891–898. © 2011 Wiley Periodicals, Inc. 相似文献10.
Angela Manuel Wei Li Vladimir Jellus Timothy Hughes Pottumarthi V. Prasad 《Magnetic resonance in medicine》2011,65(5):1377-1383
Delayed gadolinium‐enhanced MRI of cartilage is a technique, which involves T1 mapping to identify changes in the structural integrity of cartilage associated with osteoarthritis. Currently, the gold standard is 2D inversion recovery turbo spin echo, which suffers from long acquisition times and limited coverage. Three‐dimensional variable flip angle (VFA) is an alternate technique, which has been shown to be accurate when an estimate of T1 is available a priori. This study validates the variable flip angle method for delayed gadolinium‐enhanced MRI of cartilage of the femoro‐tibial knee cartilage. When amplitude of (excitation) radiofrequency field inhomogeneities were minimized using nonselective pulses and amplitude of (excitation) radiofrequency field correction using an additional acquisition of a amplitude of (excitation) radiofrequency field map, the accuracy of T1 measurements were improved, and slice‐to‐slice variations over the 3D volume were minimized. In conclusion, fast 3D T1 mapping using the variable flip angle method with amplitude of (excitation) radiofrequency field correction appears to be an efficient and accurate method for delayed gadolinium‐enhanced MRI of cartilage of the knee. Magn Reson Med, 2011. © 2010 Wiley‐Liss, Inc. 相似文献
11.
Neha Bhooshan Maryellen Giger Li Lan Hui Li Angelica Marquez Akiko Shimauchi Gillian M. Newstead 《Magnetic resonance in medicine》2011,66(2):555-564
A multiparametric computer‐aided diagnosis scheme that combines information from T1‐weighted dynamic contrast–enhanced (DCE)‐MRI and T2‐weighted MRI was investigated using a database of 110 malignant and 86 benign breast lesions. Automatic lesion segmentation was performed, and three categories of lesion features (geometric, T1‐weighted DCE, and T2‐weighted) were automatically extracted. Stepwise feature selection was performed considering only geometric features, only T1‐weighted DCE features, only T2‐weighted features, and all features. Features were merged with Bayesian artificial neural networks, and diagnostic performance was evaluated by ROC analysis. With leave‐one‐lesion‐out cross‐validation, an area under the ROC curve value of 0.77 ± 0.03 was achieved with T2‐weighted‐only features, indicating high diagnostic value of information in T2‐weighted images. Area under the ROC curve values of 0.79 ± 0.03 and 0.80 ± 0.03 were obtained for geometric‐only features and T1‐weighted DCE‐only features, respectively. When all features were considered, an area under the ROC curve value of 0.85 ± 0.03 was achieved. We observed P values of 0.006, 0.023, and 0.0014 between the geometric‐only, T1‐weighted DCE‐only, and T2‐weighted‐only features and all features conditions, respectively. When ranked, the P values satisfied the Holm–Bonferroni multiple‐comparison test; thus, the improvement of multiparametric computer‐aided diagnosis was statistically significant. A computer‐aided diagnosis scheme that combines information from T1‐weighted DCE and T2‐weighted MRI may be advantageous over conventional T1‐weighted DCE‐MRI computer‐aided diagnosis. Magn Reson Med, 2011. © 2011 Wiley‐Liss, Inc. 相似文献
12.
Bernd Bittersohl Harish S. Hosalkar Young‐Jo Kim Stefan Werlen Siegfried Trattnig Klaus A. Siebenrock Tallal C. Mamisch 《Magnetic resonance in medicine》2010,64(4):1200-1207
This pilot study defines the feasibility of cartilage assessment in symptomatic femoroacetabular impingement patients using intra‐articular delayed gadolinium‐enhanced MRI of cartilage (ia‐dGEMRIC). Nine patients were scanned preliminary to study the contrast infiltration process into hip joint cartilage. Twenty‐seven patients with symptomatic femoroacetabular impingement were subsequently scanned with intra‐articular delayed gadolinium‐enhanced MRI of cartilage. These T1 findings were correlated to morphological findings. Zonal variations were studied. This pilot study demonstrates a significant difference between the pre‐ and postcontrast T1 values (P < 0.001) remaining constant for 45 min. We noted higher mean T1 values in morphologically normal‐appearing cartilage than in damaged cartilage, which was statistically significant for all zones except the anterior‐superior zone. Intraobserver (0.972) and interobserver correlation coefficients (0.933) were statistically significant. This study outlines the feasibility of intra‐articular delayed gadolinium‐enhanced MRI of cartilage for assessment of cartilage changes in patients with femoroacetabular impingement. It can also define the topographic extent and differing severities of cartilage damage. Magn Reson Med, 2010. © 2010 Wiley‐Liss, Inc. 相似文献
13.
The effect of molecular weight, concentration, and structure on 1/T1ρ, the rotating frame relaxation rate, was investigated for several proteins using the on-resonance spin-lock technique, for locking fields B1 < 200 μT. The measured values of 1/T1ρ, were fitted to a simple theoretical model to obtain the dispersion curves 1/T1ρ(ω1) and the relaxation rate at zero B1 field, 1/T1ρ,(O). 1/T1ρ, was highly sensitive to the molecular weight, concentration, and structure of the protein. The amount of intra- and intermolecular hydrogen and disulfide bonds especially contributed to 1/T1ρ. In all samples, 1/T1ρ(O) was equal to 1/T2ρ measured at the main magnetic field Bo = 0.1 T, but at higher locking fields the dispersion curves mono-tonically decreased. The results of this work indicate that a model considering the effective correlation time of molecular motions as the main determinant for 1/T1ρ relaxation in protein solutions is not valid at very low B1 fields. The underlying mechanism for the relaxation rate 1/T1ρ at B1 fields below 200 μT is discussed. 相似文献
14.
José G. Raya Olaf Dietrich Annie Horng Jürgen Weber Maximilian F. Reiser Christian Glaser 《Magnetic resonance in medicine》2010,63(1):181-193
T2 relaxation time is a promising MRI parameter for the detection of cartilage degeneration in osteoarthritis. However, the accuracy and precision of the measured T2 may be substantially impaired by the low signal‐to‐noise ratio of images available from clinical examinations. The purpose of this work was to assess the accuracy and precision of the traditional fit methods (linear least‐squares regression and nonlinear fit to an exponential) and two new noise‐corrected fit methods: fit to a noise‐corrected exponential and fit of the noise‐corrected squared signal intensity to an exponential. Accuracy and precision have been analyzed in simulations, in phantom measurements, and in seven repetitive acquisitions of the patellar cartilage in six healthy volunteers. Traditional fit methods lead to a poor accuracy for low T2, with overestimations of the exact T2 up to 500%. The noise‐corrected fit methods demonstrate a very good accuracy for all T2 values and signal‐to‐noise ratio. Even more, the fit to a noise‐corrected exponential results in precisions comparable to the best achievable precisions (Cramér‐Rao lower bound). For in vivo images, the traditional fit methods considerably overestimate T2 near the bone‐cartilage interface. Therefore, using an adequate fit method may substantially improve the sensitivity of T2 to detect pathology in cartilage and change in T2 follow‐up examinations. Magn Reson Med, 2010. © 2009 Wiley‐Liss, Inc. 相似文献
15.
Qing Wang Sheng‐Kwei Song Huiying Zhang Bruce A. Berkowitz Shiming Chen Samuel A. Wickline Junjie Chen 《Magnetic resonance in medicine》2011,65(6):1793-1798
Retinal degeneration‐1 (rd1) mice are animal models of retinitis pigmentosa, a blinding disease caused by photoreceptor cell degeneration. This study aims to determine magnetic resonance imaging (MRI) changes in retinas of 1‐ and 3‐month‐old rd1 mice. Apparent diffusion coefficient in retina was measured using diffusion MRI. The blood‐retinal barrier leakage was evaluated using gadolinium‐diethylenetriaminepentaacetic acid‐enhanced T1‐weighted MRI before and after systemic gadolinium‐diethylenetriaminepentaacetic acid injection. Photoreceptor degeneration in rd1 retina was apparent by decreased retinal thickness and loss of water diffusion anisotropy in both 1‐ and 3‐month‐old rd1 mice. Furthermore, statistically significant increase of mean retinal apparent diffusion coefficient and gadolinium‐diethylenetriaminepentaacetic acid‐enhanced T1‐weighted MRI signals were observed in 3‐month‐old rd1 mice comparing with age‐matched wild‐type mice. Together, these data suggest that MRI parameter changes can signature common pathological changes in photoreceptor‐degenerated eyes, particularly blood‐retinal barrier leakage‐induced retinal edema. Magn Reson Med, 2011. © 2011 Wiley‐Liss, Inc. 相似文献
16.
Bernd Bittersohl Harish S. Hosalkar Young‐Jo Kim Stefan Werlen Klaus A. Siebenrock Tallal C. Mamisch 《Magnetic resonance in medicine》2009,62(6):1362-1367
The purpose of this study was to assess if delayed gadolinium MRI of cartilage using postcontrast T1 (T1Gd) is sufficient for evaluating cartilage damage in femoroacetabular impingement without using noncontrast values (T10). T1Gd and ΔR1 (1/T1Gd ? 1/T10) that include noncontrast T1 measurements were studied in two grades of osteoarthritis and in a control group of asymptomatic young‐adult volunteers. Differences between T1Gd and ΔR1 values for femoroacetabular impingement patients and volunteers were compared. There was a very high correlation between T1Gd and ΔR1 in all study groups. In the study cohort with Tonnis grade 0, correlation (r) was ?0.95 and ?0.89 with Tonnis grade 1 and ?0.88 in asymptomatic volunteers, being statistically significant (P < 0.001) for all groups. For both T1Gd and ΔR1, a statistically significant difference was noted between patients and control group. Significant difference was also noted for both T1Gd and ΔR1 between the patients with Tonnis grade 0 osteoarthritis and those with grade 1 changes. Our results prove a linear correlation between T1Gd and ΔR1, suggesting that T1Gd assessment is sufficient for the clinical utility of delayed gadolinium MRI of cartilage in this setting and additional time‐consuming T10 evaluation may not be needed. Magn Reson Med, 2009. © 2009 Wiley‐Liss, Inc. 相似文献
17.
Purpose
To demonstrate the feasibility of a novel experimental method to quantitatively analyze fiber‐network deformation in compressed cartilage by angle‐sensitive magnetic resonance imaging (MRI) of cartilage.Methods
Three knee cartilage samples of an adult sheep were imaged in a high‐resolution MRI scanner at 7 T. Main fiber orientation and its “offset” from the direction perpendicular to the bone‐cartilage boundary were derived from MR images taken at different orientations with respect to B0. Bending of the collagen fibers was determined from weight‐bearing MRI with the load (up to 1.0 MPa) applied over the whole sample surface. A “fascicle” model of the cartilage ultrastructure was assumed to analyze characteristic intensity variations in T2‐weighted images under load.Results
T2‐weighted MR images showed a strong variation of the signal intensities with sample orientation. In the T2‐weighted weight‐bearing series, regions of high signal intensity underwent shifts from the lateral to the central parts in all three cartilage samples. The bending of the collagen fibers was determined to be 27.2°, 35.4°, and 40.0° per MPa, respectively.Conclusion
Assuming a “fascicle” model, the presented MRI method provides quantitative measures of structural adjustments in compressed cartilage. Our preliminary analysis suggests that cartilage fiber deformation includes both bending and crimping. 相似文献18.
Adrienne N. Dula Daniel F. Gochberg Holly L. Valentine William M. Valentine Mark D. Does 《Magnetic resonance in medicine》2010,63(4):902-909
Quantitative MRI measures of multiexponential T2 relaxation and magnetization transfer were acquired from six samples of excised and fixed rat spinal cord and compared with quantitative histology. MRI and histology data were analyzed from six white matter tracts, each of which possessed unique microanatomic characteristics (axon diameter and myelin thickness, in particular) but a relatively constant volume fraction of myelin. The results indicated that multiexponential T2 relaxation characteristics varied substantially with variation of microanatomy, while the magnetization transfer characteristics remained close to constant. The most‐often‐cited multiexponential T2 relaxation metric, myelin water fraction, varied by almost a factor of 2 between two regions with myelin volume fractions that differed by only ≈ 12%. Based on the quantitative histology, the proposed explanation for this variation was intercompartmental water exchange, which caused the underestimation of myelin water fraction and T2 values and is, presumably, a greater factor in white matter regions where axons are small and myelin is thin. In contrast to the multiexponential T2 relaxation observations, magnetization transfer metrics were relatively constant across white matter tracts and concluded to be relatively insensitive to intercompartmental water exchange. Magn Reson Med 63:902–909, 2010. © 2010 Wiley‐Liss, Inc. 相似文献
19.
Oliver Bieri Klaus Scheffler Goetz H. Welsch S. Trattnig Tallal C. Mamisch Carl Ganter 《Magnetic resonance in medicine》2011,66(2):410-418
Fast quantitative MRI has become an important tool for biochemical characterization of tissue beyond conventional T1, T2, and T2*‐weighted imaging. As a result, steady‐state free precession (SSFP) techniques have attracted increased interest, and several methods have been developed for rapid quantification of relaxation times using steady‐state free precession. In this work, a new and fast approach for T2 mapping is introduced based on partial RF spoiling of nonbalanced steady‐state free precession. The new T2 mapping technique is evaluated and optimized from simulations, and in vivo results are presented for human brain at 1.5 T and for human articular cartilage at 3.0 T. The range of T2 for gray and white matter was from 60 msec (for the corpus callosum) to 100 msec (for cortical gray matter). For cartilage, spatial variation in T2 was observed between deep (34 msec) and superficial (48 msec) layers, as well as between tibial (33 msec), femoral, (54 msec) and patellar (43 msec) cartilage. Excellent correspondence between T2 values derived from partially spoiled SSFP scans and the ones found with a reference multicontrast spin‐echo technique is observed, corroborating the accuracy of the new method for proper T2 mapping. Finally, the feasibility of a fast high‐resolution quantitative partially spoiled SSFP T2 scan is demonstrated at 7.0 T for human patellar cartilage. Magn Reson Med, 2011. © 2011 Wiley‐Liss, Inc. 相似文献
20.
Ulrike Blume MSc Timothy Lockie MD Christian Stehning PhD Stephen Sinclair DCR Sergio Uribe MSc Reza Razavi MD Tobias Schaeffter PhD 《Journal of magnetic resonance imaging : JMRI》2009,29(2):480-487