Pituitary microadenomas: experience with Gd-DOTA-enhanced MR imaging at 0.5 Telsa

Purpose: We report our experience with magnetic resonance imaging at 0.5 Tesla in the radiological diagnosis of pituitary adenomas. Methods: Over 2 years we performed a prospective study in 38 patients with pituitary microadenomas to assess the potential additional benefit of gadolinium in the detection of small intrasellar lesions. The protocol included three coronal T1-weighted sequences: precontrast, early postcontrast (obtained less than 2 min after injection) and late postcontrast (obtained 5 min after injection). For each sequence lesions were classified according to their visibility into three categories: definite lesion, probable lesion or absent lesion. Results: Lesions were classified as well-defined in 55% of patients on the precontrast study, 89.5% on the early postcontrast study and 60.5% on the late postcontrast study. Of nine microadenomas not detected on the precontrast scans, all were clearly seen on the early post contrast scans; only four were well-defined on the late postcontrast study. Only one lesion was not seen on the early postcontrast study but was well-defined on precontras study as a spontaneous high-intensity focal area: it was a hemorrhagic microadenoma. Conclusion: Our results suggest that the early postcontrast study is the most useful sequence for the detection of microadenomas. Precontrast image is necessary to detect hemorrhagic lesions; the late postcontrast sequence has a low additional diagnostic yield and seems unnecessary unless the other sequences are inconclusive.