VALUE OF ABDOMINAL SONOGRAPHY AND MR-IMAGING AT 0.5 T IN PREOPERATIVEDETECTION OF PANCREATIC INSULINOMA - A COMPARISON WITH DYNAMIC CT ANDANGIOGRAPHY

Background: Abdominal sonography, computed tomography (CT), angiograph y, and magnetic resonance (MR) imaging are the most widely used modali ties for preoperative localization of insulinomas. CT and angiography are generally considered the techniques of reference, and the role of sonography and MR imaging in these patients is controversial. The purp ose of this study was to compare these four modalities in a group of p atients with pancreatic insulinoma and determine an effective radiolog ical approach to this disease. Methods: Twenty-eight patients with cli nical and biochemical signs of pancreatic insulinoma underwent abdomin al sonography, MR imaging at 0.5 T (spin echo technique), bolus dynami c CT, and digital subtraction angiography. Examinations were evaluated independently for the presence, size, and location of the lesions; pr eoperative diagnoses were compared with surgical findings based on pal pation and intraoperative sonography. Tumoral vascularity was histolog ically graded. Sensitivities of the four imaging techniques were calcu lated and compared with the size, location, and vascularity of the tum ors. Detection rates of combined techniques were finally determined. R esults: At surgery, 29 lesions in the 28 patients were found (range = 0.8-4.3 cm, average = 1.65 cm). Sensitivities of abdominal sonography, MR imaging, CT, and angiography were 79.3%, 65.5%, 44.8%, and 69% res pectively. Correct localization of tumor was achieved in 96.6% of case s by a combination of sonography and MR imaging and in 72.4% of cases by using CT with angiography. Conclusion: In our experience, sonograph y and MR imaging performed well in the preoperative detection of pancr eatic insulinoma. Therefore, we believe that the combination of abdomi nal sonography and MR imaging may represent the first radiological app roach in clinically suspected insulinomas and that CT and angiography should be reserved for negative and/or doubtful cases.