Dual-phase helical CT of nonfunctioning islet cell tumors

Purpose: The aim of this study was to evaluate the utility of dual- phase imaging in the assessment of nonfunctioning islet cell tumors (NFITs). Method: Six patients with histologically and biochemically proven NFIT were evaluated by arterial and portal venous dual-phase helical CT. Scan delay was 20 s for the arterial phase and 70 s for the portal phase. Each phase was assessed by consensus reading and specifically evaluated for tumor conspicuity, hepatic metastases, vascular encasement by tumor, and presence of lymphadenopathy. Results: Overall, tumor conspicuity was greater in the arterial phase (5/6) than in the portal venous phase (1/6) with a mean tumor/normal pancreas attenuation difference of 31.8 HU in the arterial phase compared with 19.2 HU in the portal venous phase. The arterial phase detected a total of 17 liver metastases compared with 9 seen in the portal phase. Lymph node enlargement was noted in three patients, which, although visible in both phases, was more easily discernible in the arterial phase. Venous encasement by tumor was better evaluated on the delayed portal venous phase than the arterial phase. Conclusion: Dual-phase helical CT scanning leads to improvement in the detection and staging of NFITs.