Abstract 533 Poster Session I, Saturday, 5/1 (poster 306)

Background: ACTH producing pituitary adenomas are the most common cause of Cushing's Syndrome in childhood. Although Gadolinium-DTPA (Gd) enhanced T1 weighted spin echo magnetic resonance imaging (SE-MRI) has proven to be the most sensitive imaging modality for localizing pituitary adenomas, its diagnostic accuracy does not exceed 40-50% in detecting Cushing's disease (CD). A new T1 weighted three-dimensional gradient echo MRI technique (FSPGR) has been recognized for its superior contrast resolution of the brain and other tissues. We aimed to determine if this technique was able to improve the diagnostic accuracy of pituitary imaging in children with CD.

Patients and Methods: We studied 9 patients with clinical and biochemical evidence of CD (age range 5-18 years) between 7/97 and 7/98. Each child underwent a SE-MRI followed by FSPGR. With both techniques, images were obtained before and after injection of Gd. MRI scans were read by two investigators, blinded to the histologic findings. In the event that the conventional MRI sequence was negative or equivocal, the patient underwent inferior petrosal sinus sampling. Surgical exploration was guided by the results of these preoperative investigations. The MRI findings were compared with the results of the final histology.

Results: No patient had a detectable tumor before Gd injection, whereas post-contrast SE-MRI identified 3 of the 9 tumors. By comparison, post-contrast FSPGR identified tumors in 6 of the 9 patients. All tumors were confirmed histologically; there were no false positive results using either technique.

Conclusions: In a cohort of 9 children with Cushing's disease, FSPGR had double the diagnostic accuracy of post contrast SE-MRI with Gd injection in detecting pituitary adenoma.