MRI of the wrist at 7 tesla using an eight-channel array coil combined with parallel imaging: preliminary results.
OBJECTIVE
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-to-noise ratio (SNR), contrast-to-noise ratio (CNR), and image quality.


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).


CONCLUSIONS
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.
Chang
Gregory
G
Center for Biomedical Imaging/Hospital for Joint Diseases, Department of Radiology, NYU Langone Medical Center, New York, New York, USA. gregory.chang@nyumc.org
Friedrich
Klaus M
KM
Wang
Ligong
L
Vieira
Renata L R
RL
Schweitzer
Mark E
ME
Recht
Michael P
MP
Wiggins
Graham C
GC
Regatte
Ravinder R
RR
D000328:Adult; D005240:Feasibility Studies; D005260:Female; D006801:Humans; D007089:Image Enhancement / Q000295:instrumentation*; D008279:Magnetic Resonance Imaging / Q000295:instrumentation*; D008280:Magnetics / Q000295:instrumentation*; D008297:Male; D019047:Phantoms, Imaging; D010865:Pilot Projects; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D014159:Transducers; D014953:Wrist / Q000033:anatomy & histology*