The Value of High-field MRI (3 Tesla) in the Assessment of Sellar Lesions

Purpose: The aim of this study was the evaluation of the normal sellar anatomy in-vitro and in-vivo with high-field MRI and its application in the diagnosis of sellar pathologies in comparison to standard MRI.

Methods: All high-field MR images were obtained using a 3 Tesla Bruker Medspec 30/80 Scanner with a head birdcage transmit/receive coil and an actively shielded gradient system with a maximum gradient strength of 45mT/m. Firstly an in-vitro study of the sella turcica was performed to depict normal pituitary and sellar anatomy at high fields.After a pilot-study this sequence-protocol was established:For T2-weighted coronal, axial and sagittal images RARE sequence (TR/TE=7790/19ms; matrix size 512×512; RARE factor=8, FOV 200mm) was used.For acquisition of T1-weighted pre- and post-contrast images a 3D gradient echo sequence with magnetization-preparation (MP-RAGE, TR/TE/TI=33.5/7.6/800 ms, matrix size 512×512; FOV 200mm, effective slice thickness1.88mm; 3 averages) was used.Between January 2002 and March 2004 58 patients gave written informed consent to participate in this study. Seven patients were examined for suspected microadenoma and in 51 patients 3T MRI was used to obtain additional information about the sellar lesion already known from standard MRI (characterization of the lesion, assessment of the integrity of the medial cavernous sinus wall).

Results: The infiltration of the medial cavernous sinus wall was suspected on standard MRI on 15 sides (47%), on high-field MRI on 9 sides (28%) and was verified by intraoperative findings on 6 sides (19%). Sensitivity of infiltration was 83% for 3 T and 67% for standard MRI. Specifity was 84% for 3 tesla and 58% for standard MRI. High-field MRI revealed microadenomas in 7 patients with a median diameter of 4mm (range 2–9mm) [Fig.1]. The segments of the cranial nerves were seen as mean 4 hypointense spots (range 2–5 spots) on high-field MRI in contrast to 3 spots (range 0–4 spots) on standard MRI. This difference was statistically significant (p<0.001).

Conclusion: High-field MRI is superior to standard-MRI for prediction of invasion of adjacent structures in patients with pituitary adenomas and improves surgical planning.

Fig. 1 demonstrates the superiority of 3 T (right) in comparison to 1.5 T (left) in the detection of microadenomas. Intraoperatively, the location of the adenoma corresponded well with the left endosellar hypointensity on 3.0 T MRI (arrow). The diagnosis of a prolactinoma was finally confirmed by histology.