Evaluation of Pancreatic Islet Cell Tumors by Fluorine-18 Fluorodeoxyglucose Positron Emission Tomography

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Abstract
Pancreatic islet cell tumors are potentially malignant tumors and are often difficult to detect with current imaging modalities. Positron emission tomography (PET) using fluorine-18–labeled fluorodeoxyglucose (FDG) is an imaging technique with high sensitivity for malignant tumors. The aim of this study was to assess the feasibility of FDG PET to detect pancreatic islet cell tumors. Nineteen lesions of histologically proved islet cell tumors were evaluated in 12 patients (5 men, 7 women; ages 22 to 77 years). FDG uptake was analyzed semiquantitatively as a standardized uptake value. The diagnostic accuracy of PET was compared with that of US, CT, and MRI. Of 19 lesions, 8 showed positive PET results (standardized uptake value > 2.3), and localization was indicated in 2 lesions. In nine tumors that were not detected by PET, seven were small tumors ranging from 1.5 to 8 mm in diameter and were not identified by other imaging methods. The sensitivity rate of PET was 53%, whereas those of US, CT, and MRI were 53%, 50%, and 53%, respectively. Our data suggest that FDG PET has a limitation in that it does not detect some small-sized islet cell tumors, mainly depending on their size, but it has potential utility as a complementary modality for other imaging techniques.