The diagnostic accuracy of preoperative CT scanning in the evaluation of pituitary prolactinomas. AJNR

Abstract

patients (26 women and nine men) who had coronal CT scans of the sella turcica for suspected ACTH-secreting pituitary adenoma underwent transsphenoidal exploration. The CT examinations were performed with a fourth-generation EMI scanner (CT 7070). The reports of the preoperative CT examinations were compared with the findings at transsphenoidal exploration; in cases with negative CT scans, the decision to operate was based on biochemical evidence of Cushing's disease. In 27 patients, distinct adenomas were found at surgery; in the eight others, total hypophysectomy (four cases) or resection of the central core of the pituitary gland (four cases) was performed. Three patients had macroadenomas, all of which had been identified correctly on preoperative CT scan. Among the 24 microadenomas «10 mm diameter), 14 had been correctly identified on preoperative CT scan while 10 were found in patients with negative scans. The CT examinations in these 35 patients showed probable adenomas in 20 cases, of which 17 (85%) were confirmed at surgery. In the other three cases (15%), adenomas were not found . Among the 15 patients with negative CT scans, 10 (66.6%) had distinct adenomas found at surgery. Coronal CT scans for ACTH-secreting adenomas had a sensitivity of 63%, a specificity of 62.5% , and an overall accuracy rate of 62.8%. Thus, in our experience, CT scanning with current stateof-the-art equipment has poor diagnostic accuracy in Cushing's disease. The possible reasons for this are that most of the adenomas in this series were microadenomas less than 6 mm in diameter, and that ACTH microadenomas probably show almost the same degree of enhancement with contrast medium as the surrounding normal pituitary tissue. In recent years, high-resolution CT of the sella turcica has almost completely replaced all other imaging techniques in the investigation of abnormalities of the pituitary gland. However, there is scant information about the diagnostic accuracy of this procedure, especially in regard to the identification of adenomas in Cushing's disease Subjects and Methods The patients included in this study had been referred for CT of the sella turcica because of clinical and biochemical evidence of pituitary-dependent cortisol hypersecretion. The CT examinations were performed with a fourth-generation scanner (EMI CT 7070). The patients were placed on the scanner couch in the prone position with the neck hyperextended. The scanner gantry was angled 90 0 to a line connecting the outer canthus of the eye to the external auditory meatus (canthomeatalline) in order to obtain direct coronal views . Technical factors were chosen so as to optimize image quality and contrast resolution whi le confining the examination time to a reasonable duration: 120 kVp, 80-99 mA, scan time 3 or 6 sec, slice width 3-5 mm (5 mm slice width was only used for the three macroadenomas , which appeared obvious on the initial plain scans), slice overlap 1 mm , sca