The increased field in the basal ganglia and correlation with disease duration suggest pathological iron content increases in MS. The peripheral phase rings are consistent with histological data demonstrating iron-rich macrophages at the periphery of a subset of lesions. The clearly defined vessels penetrating MS lesions should increase our ability to detect focal vascular abnormalities specifically related to demyelinating processes.

The purpose of this work was to investigated the feasibility of fully-balanced steady-state free-precession (bSSFP) pulse sequence for trabecular bone and knee cartilage imaging in vivo using ultra-high-field (UHF) MRI at 7T in comparison with pulse sequences previously used at 3T. We showed that bSSFP and spin-echo imaging is possible at higher field strengths within 3.2 W/kg specific absorption rate (SAR) constraints. All pulse sequences were numerically optimized based on measured tissue relaxation parameters from six healthy volunteers (T 1 ‫؍‬ 820 ؎ 128 ms, T 2 ‫؍‬ 43.5 ؎ 3 ms for bone marrow and T 1 ‫؍‬ 1745 ؎ 104 ms and T 2 ‫؍‬ 30 ؎ 4 ms for cartilage). From simulations of the Bloch equation, a signal-to-noise ratio (SNR) increase of more than 1.9 was predicted. Cartilage SNR of bSSFP was 2.4 times higher at 7T (51. Previously, it has been demonstrated that fully-balanced steady-state free-precession (bSSFP) (1) and fully-balanced steady-state spin-echo (bSSSE) (2) sequences are beneficial for imaging of the trabecular bone structure with MRI at 3T. MRI has also proved its utility for imaging the articular cartilage of the knee joint at 3T (3) and more recently at 7T (4). Translation to higher magnetic field strength is primarily motivated by increased signal-to-noise ratio (SNR). SNR is expected to increase linearly with field strength. However, the higher radio frequency (RF) power deposition in the subject and increased susceptibility artifacts stemming from off-resonance frequencies are potential problems using ultra-high-field (UHF)-MRI, and are addressed in this work.Imaging the microarchitecture of bone is of increasing importance in the assessment of fracture risk and the measurement of efficacy of therapeutic interventions in bone diseases (5). In MRI the fatty bone marrow is usually imaged since trabecular bone has extremely low signal intensity. This is due to relatively long spin-lattice relaxation T 1 and short spin-spin relaxation times T 2 (6,7) and to low concentration of water in bone. Thus, using MRI, the trabecular bone appears dark and the measured signal is provided by the bone marrow. Currently, the spatial resolution of MRI is not sufficient to resolve the individual trabeculae, with the average diameter of the trabeculae being in the order of 100 -150 m. The expected increase in SNR of UHF-MRI might be very useful to increase the image resolution to better visualize the microstructural makeup of bone and thus predict mechanical strength more accurately.Osteoarthritis, on the other hand, is a chronic, degenerative, joint disease characterized by the breakdown of joint cartilage and adjacent bone predominantly in weight-bearing joints such as the knee and hip joint. The detection and assessment of injury and loss of articular cartilage are important factors to diagnose, grade, and treat osteoarthritis (3). In particular, exact quantification of cartilage thickness and volume have been advocated as new biomarkers in osteoarthritis (8). The increased SNR provided by UHF-MRI might be us...

To develop phosphorus-31 magnetic resonance (MR) spectroscopy as an indicator of testicular viability, unilateral 720 degrees torsion of the spermatic cord was performed in 11 Copenhagen rats. In six of 11 rats, detorsion was done 1 hour later. The authors used special surface coils to obtain P-31 MR spectra (at 2 T) from both tests, then correlated MR findings with those from gross morphologic and histologic examination. In the normal testis, P-31 MR spectra had prominent phosphomonoester (PME) and adenosinetriphosphate (ATP) peaks. Testicular torsion dramatically reduced ATP to almost undetectable levels and significantly decreased the PME/Pi at 1 hour (1.18 +/- 0.22) in nine rats. In two rats, however, no spectral changes were present. Of the six rats in which detorsion was performed, three showed immediate regeneration of ATP and a normal PME/Pi (2.87 +/- 0.06) 3 hours later; testicles in the other three rats did not recover (PME/Pi = 0.72 +/- 0.01). Because gross morphologic observations and histologic findings prior to detorsion were unable to differentiate viable from nonviable tests, these preliminary data suggest P-31 MR spectroscopy may help clinicians diagnose testicular torsion and assess testicular viability.

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