INCIDENTALLY DISCOVERED ADRENAL MASSES - EVALUATION WITH GADOLINIUM ENHANCEMENT AND FAT-SUPPRESSED MR-IMAGING AT 0.5 T

The purpose of the study is to evaluate the ability of Gd-enhancement and fat-suppressed MR imaging operating at midfield strength to charac terize incidentally discovered adrenal masses. Sixty patients with 72 adrenal masses incidentally discovered during US or CT exams were stud ied with a 0.51 MR unit following clinical and laboratory evaluation. After Gd-DTPA intravenous administration a modified three-point Dixon technique was pet-formed in all patients. This technique provided thre e images sets: conventional T1-weighted SE images, fat-suppressed T1-w eighted images and water-suppressed T1-weighted images. Diagnosis was established by means of surgery (11 lesions), fineneedle biopsy (21 le sions) and stability on ultrasonographic follow-up for at least 1 year (range, 12-87 months) from adrenal lesion discovery (40 masses). In m ost of adenomas (n = 55) an homogeneous enhancement was observed on po stcontrast T1WI; however, 15 out of these lesions showed a small focal spot of high intensity in Gd-enhanced fat-suppressed images. On the c ontrary, malignant conditions (n = 6) and pheochromocytoma (n = 1), al l had inhomogeneous signal intensities which were relatively higher af ter Gadolinium injection as compared with the liver. The fat suppressi on technique demonstrated areas of bright signal intensity related to high vascularity. The performance of three observers in order to diffe rentiate malignant from benign conditions showed sensitivity, specific ity: diagnostic accuracy, positive and negative predictive values of 1 00, 88.5, 90, 50 and 100% on the basis of gadolinium enhancement only, by utilizing the Dixon technique. In conclusion, although Gd-enhancem ent and fat-suppressed sequence helped correctly differentiate among t he groups of incidentally discovered adrenal masses, the degree of; ov erlap suggests that it is still difficult to characterize individual p atients. However, he modified three-point Dixon technique after contra st material administration appears to be a further capability of midfi eld MRI in the characterization of adrenal tissue. (C) 1997 Elsevier S cience Ireland Ltd.