Comparison of computerized tomography and magnetic resonance imaging for the examination of the pituitary gland in patients with Cushing's disease

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Abstract
The vast majority of patients with Cushing's disease have a corticotroph adenoma, the selective removal of which, through the transsphenoidal route, has the potential to offer a definitive and complete cure. This study was designed to compare the diagnostic accuracy of computerized tomography (CT) and magnetic resonance imaging (MRI) to identify the presence, evaluate the size, and assess the topographic characteristics of pituitary corticotroph adenomas. Forty-two patients with Cushing's disease were included in this prospective study, of whom 16 were subsequently explored transsphenoidally. Computerized tomography used a CE 12,000 CGR apparatus with 1.5-mm coronal slices and a 2-mm interslice gap. Magnetic resonance imaging used an MR Max 0.5T GE apparatus; adjacent 3-mm slices were obtained with a T1-weighted gradient echo before and after gadolinium injection. Lesions compatible with an adenoma were identified in 29 patients by MRI and in 21 patients by CT (69 vs 50%, P < 0.02). Seven macroadenomas were identified as well by the two methods. Eight of the 22 microadenomas detected by MRI were not identified by CT. Evidence for intracavernous tumour extension was found in nine patients: it was more frequently detected by MRI (8 patients) than by CT (4 patients). Fourteen patients with positive MRI had a pituitary examination: in one case the adenoma could not be reached because of purely suprasellar location; of the other 13 all were found by the surgeon and the surgical outcome was successful in 12 cases. MRI is superior to CT for the examination of the pituitary gland in patients with Cushing's disease.