3D-FT thin sections MRI of prolactin-secreting pituitary microadenomas.

We studied 76 patients with endocrinological features of prolactin-secreting microadenoma by MRI, using three dimensional (3D) gradient echo acquisition (FLASH) sequences. MRI revealed a focal signal abnormality in the pituitary in all 37 patients who had not previously taken bromocriptine. However, focal abnormality was shown in only half the patients had been on dopamine agonist therapy; the MRI findings in these 39 patients were not affected by the duration and dosage bromocriptine, nor by the time elapsed since its discontinuation. The microadenoma gave spontaneous high signal on the unenhanced T1-weighted images in 8 cases; it was not seen on unenhanced images in 25 cases. It appeared as low signal within the enhancing gland in 51 cases but enhanced in 7 cases. The 3D technique gives thin (1 mm) slices and therefore facilitates detection of small focal abnormalities in the pituitary gland (2 x 2 mm). In the 19 previously treated patients in whom MRI did not demonstrate a focal abnormality, it showed localised atrophy of the gland in 3, a large, round gland with homogeneous signal in 1, and a heterogeneous appearance in 11; it was normal in 4 cases.