MRI OF THE ORBITA - T-1-WEIGHTED FREQUENC Y-SELECTIVE FAT-SUPPRESSIONAT 1.0 AND 1.5 TESLA

Purpose: To evaluate the diagnostic performance of fat suppression T-1 -weighted compared to conventional T-1-weighted Gadolinium-DTPA-(Gd-)e nhanced spin echo-sequences in orbital imaging. Material and methods: 31 patients with pathologic conditions or clinically suspected patholo gy of the orbita were examined using conventional T-1-weighted (T-R 40 0 -500 ms/T-E 15 ms/AC 3) and fat suppression T-1-weighted (T-R 370-50 0 ms/T-E 15 ms/AC 3) spin echo-sequences before and after i.v. injecti on of 0.1 mmol/kg Gd-DTPA. All images were evaluated by three radiolog ists experienced in MR imaging, concerning anatomical and pathological structures as well. as artifacts. The images were graded on a scale o f 1-5 (5 = excellent to 1 = poor).Results: The evaluation of anatomic structures showed that the fat-suppression technique was superior to t he conventional technique in respect of visualising the extraocular mu scles (4.4 to 3.4, p<0.05) and also with regard to the optic nerve (3. 68 to 3.78). Pathological conditions of the orbit (optic glioma and ne uritis, spread of local tumours to tie orbit), however, were better vi sualised using the fat suppression technique (4.3 to 2.95, p<0.05). Co nclusion: Contrast-enhanced T-1-weighted fat suppressed spin echo-sequ ences are useful in pathological conditions of the orbita. In optic ne uritis they may be the only sequences to show the lesion.