FAT-SUPPRESSED MR OF THE ORBIT AND CAVERNOUS SINUS - COMPARISON OF FAST SPIN-ECHO AND CONVENTIONAL SPIN-ECHO

PURPOSE: To compare T2-weighted fat-suppressed fast spin-echo imaging with fat-suppressed conventional spin-echo imaging in the detection of normal intraorbital and pericavernous anatomy and orbital disease, an d to determine the efficacy of fat saturation with T2-weighted fast sp in-echo imaging of the cavernous sinus. METHODS: Contrast-to-noise rat ios of normal intraorbital anatomy were calculated and compared in 10 consecutive patients using fat-suppressed fast spin-echo and conventio nal spin-echo T2-weighted images. Contrast-to-noise ratios of common i ntraorbital lesions were calculated and compared using fat-suppressed fast spin-echo and fat-suppressed conventional spin-echo. Qualitative evaluation was performed and compared for normal intraorbital anatomy using both fat-suppressed fast spin-echo and fat-suppressed convention al spin-echo in 16 patients. Qualitative evaluation for the detection of normal anatomic structures of the pericavernous region was performe d and compared using fast spin-echo with and without fat suppression a nd fat-suppressed conventional spin-echo T2-weighted images in 16 pati ents. Fat saturation was performed using standard commercially availab le chemical saturation technique. RESULTS: Reduced imaging time allowe d more acquisitions for fat-suppressed fast spin-echo images, which si gnificantly improved visibility of intraorbital and pericavernous anat omy over fat-suppressed conventional spin-echo. Anatomic visibility wa s also improved because of reduced motion, phase encoding, and suscept ibility artifacts. There was no significant difference between contras t-to-noise ratios for fat-suppressed fast spin-echo and fat-suppressed conventional spin-echo imaging of the lateral and medial rectus muscl es. Contrast-to-noise ratios of fat suppressed fast spin-echo of orbit al disease was significantly greater than contrast-to-noise ratios of fat-suppressed conventional spin-echo. Detection of several normal ana tomic structures of the pericavernous region was significantly improve d with non-fat-suppressed fast spin-echo over fat-suppressed fast spin -echo because of significantly reduced magnetic susceptibility artifac t. CONCLUSIONS: Fat-suppressed fast spin-echo is superior to fat-suppr essed conventional spin-echo for T2-weighted orbital imaging. Non-fat- suppressed fast spin-echo is the preferred pulse sequence for T2-weigh ted imaging of the cavernous sinus because of the minimal susceptibili ty artifact.