3D-FT THIN-SECTIONS MRI OF PROLACTIN-SECRETING PITUITARY MICROADENOMAS

We studied 76 patients with endocrinological features of prolactin-sec reting microadenoma by MRI, using three dimensional (3D) gradient echo acquisition (FLASH) sequences. MRI revealed a focal signal abnormalit y in the pituitary in all 37 patients who had not previously taken bro mocriptine. However, focal abnormality was shown in only half the pati ents had been on dopamine agonist therapy; the MRI findings in these 3 9 patients were not affected by the duration and dosage bromocriptine, nor by the time elapsed since its discontinuation. The microadenoma g ave spontaneous high signal on the unenhanced T1-weighted images in 8 cases; it was not seen on unenhanced images in 25 cases. It appeared a s low signal within the enhancing gland in 51 cases but enhanced in 7 cases. The 3D technique gives thin (1 mm) slices and therefore facilit ates detection of small focal abnormalities in the pituitary gland (2x 2 mm). In the 19 previously treated patients in whom MRI did not demon strate a focal abnormality, it showed localised atrophy of the gland i n 3, a large, round gland with homogeneous signal in 1, and a heteroge neous appearance in 11; it was normal in 4 cases.