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Objective: To validate a semi-automated method for thigh muscle and adipose tissue cross-sectional area (CSA) segmentation from MRI., Materials and Methods: An active shape model (ASM) was trained using 113 MRI CSAs from the Osteoarthritis Initiative (OAI) and combined with an active contour model and thresholding-based post-processing steps. This method was applied to 20 other MRIs from the OAI and to baseline and follow-up MRIs from a 12-week lower-limb strengthening or endurance training intervention (n = 35 females). The agreement of semi-automated vs. previous manual segmentation was assessed using the Dice similarity coefficient and Bland-Altman analyses. Longitudinal changes observed in the training intervention were compared between semi-automated and manual segmentations., Results: High agreement was observed between manual and semi-automated segmentations for subcutaneous fat, quadriceps and hamstring CSAs. With strength training, both the semi-automated and manual segmentation method detected a significant reduction in adipose tissue CSA and a significant gain in quadriceps, hamstring and adductor CSAs. With endurance training, a significant reduction in adipose tissue CSAs was observed with both methods., Conclusion: The semi-automated approach showed high agreement with manual segmentation of thigh muscle and adipose tissue CSAs and showed longitudinal training effects similar to that observed using manual segmentation.

The objective of this study was to evaluate the location-specific magnitudes of an exercise intervention on thigh muscle volume and anatomical cross-sectional area, using MRI. Forty one untrained women participated in strength, endurance, or autogenic training for 12 weeks. Axial MR images of the thigh were acquired before and after the intervention, using a T1-weighted turbo-spin-echo sequence (10 mm sections, 0.78 mm in-plane resolution). The extensor, flexor, adductor, and sartorius muscles were segmented between the femoral neck and the rectus femoris tendon. Muscle volumes were determined, and anatomical cross-sectional areas were derived from 3D reconstructions at 10% (proximal-to-distal) intervals. With strength training, the volume of the extensors (+3.1%), flexors (+3.5%), and adductors (+3.9%) increased significantly (P < 0.05) between baseline and follow-up, and with endurance training, the volume of the extensor (+3.7%) and sartorius (+5.1%) increased significantly (P < 0.05). No relevant or statistically significant change was observed with autogenic training. The greatest standardized response means were observed for the anatomical cross-sectional area in the proximal aspect (10-30%) of the thigh and generally exceeded those for muscle volumes. The study shows that MRI can be used to monitor location-specific effects of exercise intervention on muscle cross-sectional areas, with the proximal aspect of the thigh muscles being most responsive., (Copyright © 2010 Wiley-Liss, Inc.)

Quantitative data on muscle volume (MV) are important for estimating maximal muscle power. The objective of this study was to determine the correlation between anatomical cross-sectional areas (ACSAs) and the MV in thigh muscles (extensors, flexors, adductors, and sartorius) in perimenopausal women, and to identify at which proximal-to-distal level a single-slice ACSA measurement with magnetic resonance imaging (MRI) displays the highest correlation in each of these. Axial MRIs of the thigh were acquired in 41 perimenopausal women aged 50.8 +/- 3.2 years. Segmentation of the extensors, flexors, adductors, and the sartorius was performed between the femoral neck (0%) and the distal end of the intermediate vastus (100%). MVs were determined by numerical integration, and the ACSA was calculated from three-dimensional reconstructions at 10% intervals from proximal to distal. The extensors contributed 50%, the flexors 19%, the adductors 28%, and the sartorius 3% of the total thigh MV. Maximal correlations between ACSA and MV were observed at the 20-40% proximal-to-distal level in the extensors (R (2) = 0.73), at 30% in the adductors (R (2) = 0.82), and at 70% in the flexors (R (2) = 0.72) and sartorius (R (2) = 0.85), respectively. ACSA at 50% displayed the highest overall correlations (R (2) >or= 0.69) with MV for all muscle groups. Single-slice ACSAs from MRI displayed high correlations with MVs. Although the (proximal to distal) measurement locations with the highest correlation varied between the muscle groups, a single slice at the 50% location achieved the best compromise in terms of correlation between ACSA and MV across extensors, flexors, adductors and the sartorius.

Introduction:Epidemiological studies show a positive relationship between physical activity and cartilage volume, suggesting that exercise may protect against osteoarthritis. Cross-sectional experimental studies, however, have failed to show significant differences in knee cartilage morphology between athletes and nonathletic controls. The aim of the study was to test the hypothesis that knee cartilage morphology, specifically regional cartilage thickness and global subchondral bone area, is modified in sedentary, untrained adult women who increased their physical fitness during a 3-month supervised exercise intervention. Materials and Methods: Thirty-eight untrained women, aged 45–55 years, were randomly assigned to: endurance training (n = 18), strength training (n = 15) and autogenic training (control group, n = 5). Patellar and femorotibial knee cartilage morphology was determined before and after the 3-month supervised training intervention, using magnetic resonance imaging and state-of-the-art image analysis. Results: Whereas the endurance training group showed a significant increase in cardiorespiratory fitness and the strength training group a significant increase in the maximal voluntary isometric contraction force of the leg, this study did not show significant differences in knee cartilage thickness and volume, subchondral bone area or regional cartilage thickness between baseline and follow-up acquisitions within any intervention group. Discussion:This randomized longitudinal study provides no evidence that a 3-month exercise intervention in untrained middle-aged women can significantly alter knee joint morphology. Longitudinal evidence supporting that a training program, successful in increasing physical fitness, can also induce functional adaptation of articular tissues and may protect against knee osteoarthritis, remains to be presented. Copyright © 2010 S. Karger AG, Basel [ABSTRACT FROM AUTHOR]