MRT DER ORBITA: WERTIGKEIT DER T₁-GEWICHTETEN FREQUENZSELEKTIVEN FETTSATTIGUNG BEI 1,0 UND 1,5 TESLA

Purpose: To evaluate the diagnostic performance of fat suppression T₁-weighted compared to conventional T₁-weighted Gadolinium-DTPA-(Gd-)enhanced spin echo-sequences in orbital imaging. Material and methods: 31 patients with pathologic conditions or clinically suspected pathology of the orbita were examined using conventional T₁-weighted (T(R) 400-500 ms/T(E) 15 ms/AC 3) and fat suppression T₁-weighted (T(R) 370-500 ms/T(E) 15 ms/AC 3) spin echo-sequences before and after i.v. injection of 0.1 mmol/kg Gd-DTPA. All images were evaluated by three radiologists experienced in MR imaging, concerning anatomical and pathological structures as well as artifacts. The images were graded on a scale of 1-5 (5 = excellent to 1 = poor). Results: The evaluation of anatomic structures showed that the fat-suppression technique was superior to the conventional technique in respect of visualising the extraocular muscles (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 neuritis, spread of local tumours to the orbit), however, were better visualised using the fat suppression technique (4.3 to 2.95, p<0.05). Conclusion: Contrast-enhanced T₁-weighted fat suppressed spin echo-sequences are useful in pathological conditions of the orbita. In optic neuritis they may be the only sequences to show the lesion.