Cartilage imaging at 3.0T with gradient refocused acquisition in the steady-state (GRASS) and IDEAL fat-water separation.
OBJECTIVE
To demonstrate the feasibility of evaluating the articular cartilage of the knee joint at 3.0T using gradient refocused acquisition in the steady-state (GRASS) and iterative decomposition of water and fat with echo asymmetry and least-squares estimation (IDEAL) fat-water separation.


METHODS
Bloch equation simulations and a clinical pilot study (n = 10 knees) were performed to determine the influence of flip angle of the IDEAL-GRASS sequence on the signal-to-noise ratio (SNR) of cartilage and synovial fluid and the contrast-to-noise ratio (CNR) between cartilage and synovial fluid at 3.0T. The optimized IDEAL-GRASS sequence was then performed on 30 symptomatic patients as part of the routine 3.0T knee MRI examination at our institution.


RESULTS
The optimal flip angle was 50 degrees for IDEAL-GRASS cartilage imaging, which maximized contrast between cartilage and synovial fluid. The IDEAL-GRASS sequence consistently produced high-quality fat- and water-separated images of the knee with bright synovial fluid and 0.39 x 0.67 x 1.0 mm resolution in 5 minutes. IDEAL-GRASS images had high cartilage SNR and high contrast between cartilage and adjacent joint structures. The IDEAL-GRASS sequence provided excellent visualization of cartilage lesions in all patients.


CONCLUSIONS
The IDEAL-GRASS sequence shows promise for use as a morphologic cartilage imaging sequence at 3.0T.
Kijowski
Richard
R
Department of Radiology, University of Wisconsin, 600 Highland Avenue, Madison, WI 53792, USA. r.kijowski@hosp.wisc.edu
Tuite
Michael
M
Passov
Leo
L
Shimakawa
Ann
A
Yu
Huanzhou
H
Hu
Huanzhou
H
Reeder
Scott B
SB
D000328:Adult; D002358:Cartilage, Articular / Q000033:anatomy & histology*; D005240:Feasibility Studies; D006801:Humans; D007719:Knee Joint / Q000033:anatomy & histology; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008875:Middle Aged; D013582:Synovial Fluid