Musculoskeletal MRI at 3.0 T: relaxation times and image contrast.
OBJECTIVE
The purpose of our study was to measure relaxation times in musculoskeletal tissues at 1.5 and 3.0 T to optimize musculoskeletal MRI methods at 3.0 T.


METHODS
In the knees of five healthy volunteers, we measured the T1 and T2 relaxation times of cartilage, synovial fluid, muscle, marrow, and fat at 1.5 and 3.0 T. The T1 relaxation times were measured using a spiral Look-Locker sequence with eight samples along the T1 recovery curve. The T2 relaxation times were measured using a spiral T2 preparation sequence with six echoes. Accuracy and repeatability of the T1 and T2 measurement sequences were verified in phantoms.


RESULTS
T1 relaxation times in cartilage, muscle, synovial fluid, marrow, and subcutaneous fat at 3.0 T were consistently higher than those measured at 1.5 T. Measured T2 relaxation times were reduced at 3.0 T compared with 1.5 T. Relaxation time measurements in vivo were verified using calculated and measured signal-to-noise results. Relaxation times were used to develop a high-resolution protocol for T2-weighted imaging of the knee at 3.0 T.


CONCLUSIONS
MRI at 3.0 T can improve resolution and speed in musculoskeletal imaging; however, interactions between field strength and relaxation times need to be considered for optimal image contrast and signal-to-noise ratio. Scanning can be performed in shorter times at 3.0 T using single-average acquisitions. Efficient higher-resolution imaging at 3.0 T can be done by increasing the TR to account for increased T1 relaxation times and acquiring thinner slices than at 1.5 T.
Department of Radiology, Stanford University, 300 Pasteur Dr., Grant Bldg. S0-68B, Stanford, CA 94305-5105, USA. gold@stanford.edu
Garry E
GE
Gold
Eric
E
Han
Jeff
J
Stainsby
Graham
G
Wright
Jean
J
Brittain
Christopher
C
Beaulieu
D000328:Adult; D001853:Bone Marrow / Q000033:anatomy & histology; D002358:Cartilage, Articular / Q000033:anatomy & histology*; D005260:Female; D006801:Humans; D007717:Knee / Q000033:anatomy & histology*; D007719:Knee Joint / Q000033:anatomy & histology*; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D018482:Muscle, Skeletal / Q000033:anatomy & histology*; D019047:Phantoms, Imaging; D015203:Reproducibility of Results