Rice pads: Novel devices for homogeneous fat suppression in the knee

Abstract

Background: In magnetic resonance imaging (MRI) of the knee joint, when imaging the knee in a flexed position using the chemical-shift-selective (CHESS) method, lingering fat signals in the popliteal region are sometimes seen. Purpose: To investigate whether a pad filled with rice (rice pad) placed in the popliteal space is effective in eliminating the lingering fat signals in MR images of the flexed knee, based on the hypothesis that the use of a rice pad would improve the fat suppression effect. Material and Methods: Subjects were 10 healthy volunteers (five males, five females; age, 20–45 years) from whom images were taken using CHESS. Images were obtained with: 1) the knee extended and nothing placed underneath; 2) the knee bent with a sponge placed underneath; and 3) the knee bent with a rice pad placed underneath. The effectiveness of suppressing fat signals was visually assessed by one radiologist and one radiological technologist. Results: The fat suppression effect in images obtained with the knee extended was good. In contrast, the images made with a sponge under the knee had conspicuous lingering fat signals for nearly all subjects. In the images made with a rice pad under the knee, a uniformly good fat signal suppression effect was seen in all patients, and the assessment score was far higher than that with the sponge pillow ( P<0.001). Conclusion: Lingering fat signals were suppressed with the use of a rice pad, and fat-suppressed images of the knee joint using CHESS were found to be improved.