Objective To assess and compare subregional and whole T1rho values (median ± interquartile range) of femorotibial cartilage and menisci in patients with doubtful (Kellgren-Lawrence (KL) grade 1) to severe (KL4) osteoarthritis (OA) at 3T. Materials and Methods 30 subjects with varying degrees of OA (KL1–4, 13 females, 17 males, mean age ± SD = 63.9 ± 13.1 years) were evaluated on a 3T MR scanner using a spin-lock-based 3D GRE sequence for T1rho mapping. Clinical proton density (PD)-weighted fast spin echo (FSE) images in sagittal (without fat saturation), axial, and coronal (fat-saturated) planes were acquired for cartilage and meniscus Whole-Organ MR Imaging Score (WORMS) grading. Wilcoxon rank sum test was performed to determine whether there were any statistically significant differences between subregional and whole T1rho values of femorotibial cartilage and menisci in subjects with doubtful to severe OA. Results Lateral (72±10 milliseconds, median ± interquartile range) and medial (65±10 milliseconds) femoral anterior cartilage subregions in moderate-severe OA subjects had significantly higher T1rho values (P < 0.05) than cartilage subregions and whole femorotibial cartilage in doubtful-minimal OA subjects. There were statistically significant differences in meniscus T1rho values of the medial posterior subregion of subjects with moderate-severe OA and T1rho values of all subregions and the whole meniscus in subjects with doubtful-minimal OA. When evaluated based on WORMS, statistically significant differences were identified in T1rho values between the lateral femoral anterior cartilage subregion in patients with WORMS5–6 (advanced degeneration) and whole femorotibial cartilage and all cartilage subregions in patients with WORMS0–1 (normal). Conclusion T1rho values are higher in specific meniscus and femorotibial cartilage subregions. These findings suggest that regional damage of both femorotibial hyaline cartilage and menisci may be associated with osteoarthritis.

Purpose:To demonstrate the feasibility of acquiring highresolution, isotropic 3D-sodium magnetic resonance (MR) images of the whole knee joint in vivo at ultrahigh field strength (7.0T) via a 3D-radial acquisition with ultrashort echo times and clinically acceptable acquisition times. Materials and Methods:Five healthy controls (four males, one female; mean Ϯ standard deviation [SD] age 28.7 Ϯ 4.8 years) and five patients with osteoarthritis (OA) (three males, two females; mean Ϯ SD age 52.4 Ϯ 5.6 years) underwent 23 Na MRI on a 7T, multinuclei equipped whole-body scanner. A quadrature 23 Na knee coil and a 3D-gradient echo (GRE) imaging sequence with a radial acquisition were utilized. Cartilage sodium concentration was measured and compared between the healthy controls and OA patients. Results:The average signal-to-noise ratio (SNR) for different spatial resolutions (1.2-4 mm) varied from ϳ14 -120, respectively. The mean sodium concentration of healthy subjects ranged from ϳ240 Ϯ 28 mM/L to 280 Ϯ 22 mM/L. However, in OA patients the sodium concentrations were reduced significantly by ϳ30%-60%, depending on the degree of cartilage degeneration. Conclusion:The preliminary results suggest that sodium imaging at 7T may be a feasible potential alternative for physiologic OA imaging and clinical diagnosis.

Objective To evaluate healthy skeletal muscle pre- and post-exercise via 7 T 23Na MRI and muscle proton T2 mapping, and to evaluate diabetic muscle pre- and post-exercise via 7 T 23Na MRI. Methods The calves of seven healthy subjects underwent imaging pre- and post-exercise via 7 T 23Na MRI (3D fast low angle shot, TR/TE=80 ms/0.160 ms, 4 mm × 4 mm × 4 mm) and 1 week later by 1H MRI (multiple spin-echo sequence, TR/TE=3,000 ms/15–90 ms). Four type 2 diabetics also participated in the 23Na MRI protocol. Pre- and post-exercise sodium signal intensity (SI) and proton T2 relaxation values were measured/calculated for soleus (S), gastrocnemius (G), and a control, tibialis anterior (TA). Two-tailed t tests were performed. Results In S/G in healthy subjects post-exercise, sodium SI increased 8–13% (p<0.03), then decreased (t1/2=22 min), and 1H T2 values increased 12–17% (p<0.03), then decreased (t1/2=12–15 min). In TA, no significant changes in sodium SI or 1H T2 values were seen (−2.4 to 1%, p>0.17). In S/G in diabetics, sodium SI increased 10–11% (p<0.04), then decreased (t1/2=27–37 min) without significant change in the TA SI (−3.6%, p= 0.066). Conclusion It is feasible to evaluate skeletal muscle via 3D 23Na MRI at 7 T. Post-exercise muscle 1H T2 values return to baseline more rapidly than sodium SI. Diabetics may demonstrate delayed muscle sodium SI recovery compared with healthy subjects.

OBJECTIVE. The objective of this study was to quantitatively assess cartilage degeneration via T2 mapping to compare patients with and those without meniscal tears. SUBJECTS AND METHODS. Thirty-seven patients (18 men, mean age ± SD, 65.7 ± 7.8 years; 19 women, mean age, 63.8 ± 12.0 years) with clinical symptoms of osteoarthritis were studied on 3-T MRI using a 2D multiecho spin-echo sequence for T2 mapping. Meniscal signal and morphology were qualitatively graded and correlated to the T2 values of cartilage. Analysis of covariance, Bonferroni multiple comparison correction, and Spearman’s correlation coefficients were used for statistical analysis. RESULTS. Patients with meniscal tears (median ± interquartile range, 50.1 ± 6.1 milliseconds) had significantly (p = 0.021) higher T2 values of cartilage than those without meniscal tears (45.7 ± 4.8 milliseconds). T2 values of cartilage were significantly higher in the medial compartment than in the lateral compartment in patients with medial meniscal tears (p = 0.018). CONCLUSION. T2 measurements are increased in patients with meniscal tears; this finding adds support to the theory of an association of osteoarthritis with damage to both the menisci and hyaline cartilage.