[The MRT of the orbit: the value of T1-weighted frequency-selective fat saturation at 1.0 and 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 (TR 400-500 ms/TE 15 ms/AC 3) and fat suppression T1-weighted (TR 370-500 ms/TE 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.