3 T MR Assessment of Pituitary Microadenomas

Demonstration and accurate localisation of pituitary microadenomas in the adenohypophysis are essential to institute appropriate medical management and aid surgical planning, especially when an endoscopic procedure is envisaged. Given the features of pituitary microadenomas, ideally, high spatial and temporal resolution is required for neuroradiological investigation. There is a consensus in the literature that MR scanning is the method of choice for pituitary imaging and dynamic studies offer greater sensitivity in identifying pituitary microadenomas. However, the spatial resolution and limited number of slices acquired constitute major drawbacks using 1.5 T MR devices. A 3 Tesla Signa Excite MR system (GE Medical Systems) was recently installed in the Neuroradiology Unit of Bellaria Hospital, Bologna. The new device was tested specifically for the study of pituitary microadenomas using an FSE dynamic sequence allowing the acquisition of nine slices (slice thickness 2.5 mm) over the pituitary gland with high spatial resolution in a few seconds. This sequence, repeated six times after gadolinium administration through an injector, displays the gradual enhancement of the adenohypophysis and any microadenomas present in the gland. As the microadenoma uptake of gadolinium is lower than the adenohypophysis uptake, the possible microadenoma presence becomes appreciable only in some of the six sequences as a negative image with respect to the normal parenchyma. Pituitary microadenomas undetected in previous scans using a 1.5 T system were disclosed by this imaging technique with highly accurate morphological localisation.