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.

Purpose:To demonstrate the feasibility of quantitatively evaluating and measuring T 1 and T 2 relaxation times of human tibialis anterior (TA) muscles metabolites in vivo at 7T and to compare these results with those of 3T. Materials and Methods:A model lipid phantom (corn oil) and healthy volunteers (n ϭ 4, mean Ϯ SD age 35.6 Ϯ 5.6 years) were scanned on 3T and 7T whole-body MR scanners. A voxel of 10 ϫ 10 ϫ 10 mm 3 was positioned on the lipid phantom and right calf TA muscles using the singlevoxel stimulated echo acquisition mode (STEAM) pulse sequence. All magnetic resonance spectroscopy (MRS) data were processed with Java-based Magnetic Resonance User Interface (JMRUI) using Hankel Lanczos Singular Value Decomposition (HLSVD) filtering to remove the residual water signal.Results: T 1 shows a steady increase while T 2 shows a slight decrease with B 0 and the spectra show larger spectral resolution at 7T than at 3T in the lipid phantom. T 1 values of all the metabolites are higher, while T 2 values are slightly lower at 7T than those of 3T compared to reported results in TA. The maximum percentage of increase in T 1 is about Ϸ488%, the maximum percentage of decrease in T 2 is about Ϸ65%. Conclusion:The preliminary results can potentially be used for calculating relaxation correction factors required for absolute quantitation of skeletal muscle metabolite concentrations and for further protocol and sequence optimization.

Purpose: To determine the feasibility of performing MRI of the wrist at 7 Tesla (T) with parallel imaging and to evaluate how acceleration factors (AF) affect signal-tonoise ratio (SNR), contrast-to-noise ratio (CNR), and image quality. Materials and Methods:This study had institutional review board approval. A four-transmit eight-receive channel array coil was constructed in-house. Nine healthy subjects were scanned on a 7T whole-body MR scanner. Coronal and axial images of cartilage and trabecular bone micro-architecture (3D-Fast Low Angle Shot (FLASH) with and without fat suppression, repetition time/echo time ¼ 20 ms/4.5 ms, flip angle ¼ 10 , 0.169-0.195 Â 0.169-0.195 mm, 0.5-1 mm slice thickness) were obtained with AF 1, 2, 3, 4. T1-weighted fast spin-echo (FSE), proton density-weighted FSE, and multiple-echo data image combination (MEDIC) sequences were also performed. SNR and CNR were measured. Three musculoskeletal radiologists rated image quality. Linear correlation analysis and paired t-tests were performed.Results: At higher AF, SNR and CNR decreased linearly for cartilage, muscle, and trabecular bone (r < À0.98). At AF 4, reductions in SNR/CNR were:52%/60% (cartilage), 72%/63% (muscle), 45%/50% (trabecular bone). Radiologists scored images with AF 1 and 2 as near-excellent, AF 3 as good-to-excellent (P ¼ 0.075), and AF 4 as average-to-good (P ¼ 0.11). Conclusion:It is feasible to perform high resolution 7T MRI of the wrist with parallel imaging. SNR and CNR decrease with higher AF, but image quality remains above-average. MAGNETIC RESONANCE IMAGING has been shown to be a useful technique to detect wrist derangements, including tears of the triangular fibrocartilage complex (TFCC) (1,2), tears of the scapholunate and lunotriquetral ligaments (3), cartilage erosions (4), abnormalities in tendons (5) and peripheral nerves (6), and alterations in trabecular bone micro-architecture (7).There is increasing evidence that high field (HF, 3.0 Tesla [T]) and ultra high field (UHF, 7-9.4T) MRI can provide improved diagnostic capabilities compared with MRI performed at standard clinical field strength (8,9). The main advantage of HF/UHF MRI is the increased signal-to-noise ratio (SNR), which can be translated into increases in spatial resolution or imaging speed, improved spectral resolution, and the ability to perform multi-nuclear imaging. Challenges of performing UHF MRI include: changes in T1 and T2 relaxation rates (increase in T1 and decrease in T2), maintenance of B 0 and B 1 field homogeneity, increased chemical shift artifact, increased acoustic noise, and greater RF energy deposition. Nevertheless, the potential for increased SNR and higher spatial resolution could prove useful in imaging of the wrist, where small structures composing this anatomically complex joint can pose diagnostic imaging challenges.Parallel acceleration techniques and HF/UHF scanners can act in synergy to boost the performance of MRI (10). The additional SNR provided by HF/UHF MRI can compensate for the SNR penalty incurred by im...

Purpose: To rapidly acquire T 1 -weighted images using a three-dimensional fast low angle shot (3D FLASH) sequence in combination with generalized autocalibrating partially parallel acquisitions (GRAPPA) and variable flip angle (VFA) method at 3.0T. Materials and Methods:3D T 1 maps of model systems (gadolinium [Gd] and agarose phantoms), bovine cartilage, and human subjects were constructed on a 3.0T clinical whole-body MR scanner. The T 1 values of model systems measured using the 2D inversion-recovery fast-spin-echo (IR-FSE) sequence were considered as a reference method to validate the rapid 3D method for comparison. Results:The root mean square coefficient of variation percentage (RMS-CV%) of the median T 1 of agarose phantom across different acquisition methods was ϳ6.2%. The RMS-CV% of the median T 1 of bovine cartilage across different acquisition methods was ϳ4.1%. The RMS-CV% of median T 1 of the cartilages among the subjects was between ϳ7.3% to 11.1%. In our study, rapid 3D-T 1 mapping with VFA and parallel imaging with different acceleration factors (AFs) (AF ϭ 1, 2, 3, and 4) seems to have no obvious influence on the T 1 mapping (before and after contrast agent administration). Conclusion:The preliminary results demonstrate that it is possible to quantify 3D-T 1 mapping of the whole knee joint (with 0.7 mm 3 isotropic resolution) under approximately five minutes with excellent in vivo reproducibility at 3.0T.

Magnetic resonance imaging (MRI) at 7.0 T has the potential for higher signal-to-noise ratio (SNR), improved spectral resolution, and faster imaging compared with 1.5-T and 3.0-T MR systems. This is especially interesting for challenging imaging regions like the wrist and the hand because of the small size of the visualized anatomical structures; the increase in SNR could then be directly converted into higher spatial resolution of the images. Practically, imaging at 7.0 T poses a variety of technical challenges such as static (B0) and radiofrequency (B1) homogeneities, shimming, chemical shift artifacts, susceptibility artifacts, alterations in tissue contrast, specific absorption rate limitations, coil construction, and pulse sequence tuning. Despite these limitations, this first experience in anatomical imaging of the wrist and the hand at 7.0 T is very promising. Functional imaging techniques will gain importance at ultra-high-field MRI and need to be assessed in detail in the future.