Our results suggest that both in vivo T(1rho) and T(2) relaxation times increase with the degree of cartilage degeneration. T(1rho) relaxation time may be a more sensitive indicator for early cartilage degeneration than T(2). The ability to detect early cartilage degeneration prior to morphologic changes may allow us to critically monitor the course of OA and injury progression, and to evaluate the success of treatment to patients with early stages of OA.

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PURPOSE-To evaluate differences in T2 values in femoral and tibial cartilage at magnetic resonance (MR) imaging in patients with varying degrees of osteoarthritis (OA) compared with healthy subjects and to develop a mapping and display method based on calculation of T2 z scores for visual grading and assessment of cartilage heterogeneity in patients with OA.MATERIALS AND METHODS-Knee cartilage was evaluated in 55 subjects who were categorized with radiography as healthy (n=7) or as having mild OA (n=20) or severe OA (n=28). Cartilage regions were determined with manual segmentation of an MR image acquired with spoiled gradients and fat suppression. The segmentation was applied to a map of T2 relaxation time and was analyzed in four knee cartilage compartments (ie, the medial and lateral tibia and femur). Differences between cartilage compartment T2 values and subject groups were analyzed with analysis of covariance. Correlations of cartilage T2 values with clinically reported symptoms and cartilage thickness and volume were examined. Cartilage T2 values were converted to z scores per voxel on the basis of normal population values in the same cartilage compartment to better interpret cartilage heterogeneity and variation from normal. RESULTS-Healthy subjects had mean T2 values of 32.1-35.0 msec, while patients with mild and severe OA had mean T2 values of 34.4-41.0 msec. All cartilage compartments except the lateral tibia showed significant (P< .05) increases in T2 relaxation time between healthy and diseased knees; however, no significant difference was found between patients with mild and severe OA. Correlation of T2 values with clinical symptoms and cartilage morphology was found predominantly in medial compartments. Quantitative measures of T2 relaxation times may be useful in the characterization and longterm tracking of OA. Previous reports have demonstrated spatial variation of T2 relaxation times in cartilage explants (4), healthy subjects (5), and substantial changes with age (6), but we are unaware of reports that present T2 relaxation time variation with OA in humans. CONCLUSION-Femoral HHS Public AccessCartilage tissue analysis has shown increased water content in tissue that has been degraded through OA processes (7) and decreased glycosaminoglycan concentration and proteoglycan size in diseased tissue (8,9). These findings support those of previous studies (10) that early cartilage degeneration due to collagen damage and changes in collagen content and arrangement will increase water mobility in the tissue, thus increasing T2 relaxation time. Thus, the purpose of our study was to evaluate differences in femoral and tibial cartilage T2 relaxation times in healthy subjects and patients with varying degrees of OA and to develop a mapping and display method based on calculating T2 relaxation time z scores for visual grading and assessment of cartilage heterogeneity in patients with OA. MATERIALS AND METHODS Patients and StatusUnilateral knee magnetic resonance (MR) imaging was performed from mi...

Quantitative cortical micro-architectural endpoints are important for understanding structure-function relations in the context of fracture risk and therapeutic efficacy. This technique study details new image-processing methods to automatically segment and directly quantify cortical density, geometry, and micro-architecture from HR-pQCT images of the distal radius and tibia. An automated segmentation technique was developed to identify the periosteal and endosteal margins of the distal radius and tibia, and detect intra-cortical pore space morphologically consistent with Haversian canals. The reproducibility of direct quantitative cortical bone indices based on this method was assessed in a pooled dataset of 56 subjects with two repeat acquisitions for each site. The in vivo precision error was characterized using root mean square coefficient of variation (RMSCV%) from which, the least significant change (LSC) was calculated. Bland-Altman plots were used to characterize bias in the precision estimates. The reproducibility of cortical density and cross-sectional area measures was high (RMSCV <1% and <1.5%, respectively) with good agreement between young and elder medians. The LSC for cortical porosity (Ct.Po) was somewhat smaller in the radius (0.58%) compared with the distal tibia (0.84%) and significantly different between young and elder medians in the distal tibia (LSC: 0.75% vs. 0.92%; p<0.001). The LSC for pore diameter and distribution (Po.Dm and Po.Dm.SD) ranged between 15 and 23μm. Bland-Altman analysis revealed moderate bias for integral measures of area and volume, but not density nor microarchitecture. This study indicates HR-pQCT measures of cortical bone density and architecture can be measured in vivo with high reproducibility and limited bias across a biologically relevant range of values. The results of this study provide informative data for the design of future clinical studies of bone quality.

Cartilage lesions, bone marrow edema pattern, and meniscal and ligamentous lesions were frequently demonstrated on MR images in patients with advanced osteoarthritis. Clinical findings showed no significant correlations with KL score and extent of findings at MR imaging.

The results of this pilot investigation provide a potential explanation for the inability of standard BMD measures to explain the elevated fracture incidence in patients with T2DM. The findings suggest that T2DM may be associated with impaired resistance to bending loads due to inefficient redistribution of bone mass, characterized by loss of intracortical bone offset by an elevation in trabecular bone density.

Purpose:To longitudinally evaluate cartilage matrix changes by using magnetic resonance (MR) imaging T1 r (T1 relaxation time in rotating frame) and T2 quantifi cation and to study the relationship between meniscal damage and cartilage degeneration in anterior cruciate ligament (ACL)-reconstructed knees. Materials and Methods:This was an institutional review board-approved, HIPAAcompliant study. Informed consent was obtained. Twelve patients with acute ACL injuries were imaged with 3.0-T MR imaging at baseline (after injury and prior to ACL reconstruction) and 1 year after ACL reconstruction. Ten age-matched healthy subjects were studied as controls. Cartilage T1 r and T2 were quantifi ed in full thickness, superfi cial, and deep layers of defi ned subcompartments at baseline and follow-up in ACL-injured knees and were compared with measures acquired in matched regions of control knees. Meniscal lesions were graded by using modifi ed subscores of the Whole-Organ Magnetic Resonance Imaging Score system. Results:T1 r values of the posterolateral tibial cartilage in ACLinjured knees were signifi cantly elevated at baseline compared with T1 r values of control knees and were not fully recovered at 1-year follow-up. T1 r values of weight-bearing medial femorotibial cartilage in ACL-injured knees were signifi cantly elevated at 1-year follow-up compared with those of control knees. No signifi cant differences in T2 values between ACL-injured and control knees were found. Patients with lesions in the posterior horn of the medial meniscus showed a greater increase of T1 r and T2 from baseline to follow-up in adjacent cartilage than patients without lesions in the medial meniscus. Conclusion:Quantitative MR imaging T1 r and T2 enable detection of changes in the cartilage matrix of ACL-reconstructed knees as early as 1 year after ACL reconstruction.q RSNA, 2010

High resolution magnetic resonance (MR) images of the distal radius were obtained at 1.5 Tesla in premenopausal normal, postmenopausal normal, and postmenopausal osteoporotic women. The image resolution was 156 microm in plane and 700 microm in the slice direction; the total imaging time was approximately 16 minutes. An intensity-based thresholding technique was used to segment the images into trabecular bone and marrow, respectively. Extensions of standard stereological techniques were used to derive measures of trabecular bone structure from these segmented images. The parameters calculated included apparent measures of trabecular bone volume fraction, trabecular thickness, trabecular spacing, and trabecular number. Fractal-based texture parameters, such as the box-counting dimension, were also derived. Trabecular bone mineral density (BMD) and cortical bone mineral content (BMC) were measured in the distal radius using peripheral quantitative computed tomography (pQCT). In a subset of patients, spinal trabecular BMD was measured using quantitative computed tomography (QCT). Correlations between the indices of trabecular bone structure measured from these high-resolution MR images, age, BMD, and osteoporotic fracture status were examined. Cortical BMC and trabecular BMD at the distal radius, spinal BMD, trabecular bone volume fraction, trabecular thickness, trabecular number, and fractal dimension all decreased with age. Trabecular spacing showed the greatest percentage change and increased with age. In addition, significant differences were evident in spinal BMD, radial trabecular BMD, trabecular bone volume fraction, trabecular spacing, and trabecular number between the postmenopausal nonfracture and the postmenopausal osteoporotic subjects. Trabecular spacing and trabecular number showed moderate correlation with radial trabecular BMD but correlated poorly with radial cortical BMC. High resolution MR imaging, a potentially useful tool for quantifying trabecular structure in vivo, may have applications for understanding and evaluating skeletal changes related to age and osteoporosis.