Garry Evan Gold MD, Presenter: Nothing to Disclose

Samuel Edward Fuller MD, Abstract Co-Author: Nothing to Disclose

Ann Shimakawa MS, Abstract Co-Author: Nothing to Disclose

Huanzhou Yu, Abstract Co-Author: Nothing to Disclose

Jane W Johnson, Abstract Co-Author: Nothing to Disclose

Christopher Frederick Beaulieu MD, Abstract Co-Author: Nothing to Disclose

Scott Brian Reeder, Abstract Co-Author: Nothing to Disclose

et al, Abstract Co-Author: Nothing to Disclose

Uniform fat suppression in the ankle with fat-suppressed FSE (FS-FSE) is difficult due to Bo and B1 inhomogeneities. We compared iterative decomposition of water and fat with echo asymmetry and least squares estimation (IDEAL)-FSE to FS-FSE in MR imaging of the ankle.

Ankles of patients (n=33) were imaged in the coronal plane using a GE Signa LX/I 1.5T scanner and an extremity coil. IDEAL-FSE (TR/TE 4600/22ms) had three echoes and FS-FSE (TR/TE 4600/17ms) had two averages. Both IDEAL and FS-FSE used BW=+20 kHz; echo train length=8; FOV=12; slice thickness=3 mm; 24-27 coronal images; 512 x 192 matrix. Scan time was 5:30 for IDEAL-FSE, and 3:46 for FS-FSE. For each method, SNR efficiency was measured in cartilage and joint fluid, and fluid/cartilage CNR efficiency was calculated. Images were scored by consensus of two experienced musculoskeletal radiologists (0-poor; 1-fair; 2-good; 3-excellent) for both fat suppression and diagnostic quality. A paired student t-test was performed to compare SNR and CNR efficiency. Qualitative fat suppression and diagnostic quality scores were compared with a Wilcoxon paired signed rank test. P values < .05 were considered significant.

Articular cartilage and fluid SNR efficiency were similar using both sequences (p > .05). Cartilage-Fluid CNR efficiency was higher with IDEAL-FSE than FS-FSE (p < .05). Diagnostic quality was higher (p < .05) using IDEAL-FSE (2.9) compared with FS-FSE (2.5). Fat saturation was good on FS-FSE (1.9) while water-fat separation was excellent with IDEAL-FSE (3.0) images, which was significant (p < .05). IDEAL-FSE had outstanding water-fat separation in areas of consistent failure of fat saturation on the FS-FSE images: near the medial and lateral malleoli, in the distal tibia, the calcaneus, and near metallic hardware. The IDEAL method also produced water, fat, and combined images corrected for chemical shift.

IDEAL-FSE had excellent water-fat separation, and the water, fat and combined images allowed us to eliminate the coronal T1-weighted series from our ankle protocol, resulting in a net exam time reduction of 2 minutes. IDEAL-FSE is a promising technique for MR imaging of the ankle.

Gold, G, Fuller, S, Shimakawa, A, Yu, H, Johnson, J, Beaulieu, C, Reeder, S, et al, , MR Imaging of the Ankle: Comparison of FS-FSE with IDEAL-FSE.  Radiological Society of North America 2005 Scientific Assembly and Annual Meeting, November 27 - December 2, 2005 ,Chicago IL. http://archive.rsna.org/2005/4415686.html