MRI of the Wrist at 7 Tesla Using an Eight-Channel Array Coil Combined with Parallel Imaging: Preliminary Results

Purpose: To determine the feasibility of performing MRI of the wrist at 7 Testa (T) with parallel imaging and to evaluate how acceleration factors (AF) affect signal-to-noise 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 = 20 ms/4.5 ms, flip angle = 10 degrees, 0.169-0.195 x 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 < -0.98). 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 = 0.075), and AF 4 as average-to-good (P = 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.