Influence of bowel preparation before 18F-FDG PET/CT on physiologic 18F-FDG activity in the intestine

507 Objectives To investigate the benefit of including the brain in the field of view (FOV) of FDG-PET/CTscan in patients with malignant melanoma (MM). Methods Between 01-04-2008 and 30-11-2009 the local database was searched for MM patients who underwent FDG-PET/CT (with inclusion of the entire brain in the FOV) and MRI within 3 months time period. A total of 49 examinations were obtained in 34 patients (17 male, 17 female; mean age 52.7, range 26-80 years) and investigated. According to the AJCC classification 24 patients with stage IV, 7 stage I and 3 stage II were included. The CT part was acquired after IV contrast administration in the venous phase. Gadolinium-enhanced MRI was considered as the gold standard. The average time interval between PET/CT and MRI was 15.8 days. Results On FDG-PET/CT 73 suspected lesions were identified: 3 presented with altered (hyper-)metabolism only, 36 were only seen on CT and 34 were identified on both PET and CT (8 hyper- and 26 hypometabolic). MRI detected 133 lesions, resulting in a sensitivity and accuracy of FDG-PET/CT of 55%. Specificity could not be calculated since there were no true negative lesions present. On scan basis 22/49 FDG-PET/CT examinations were classified as positive. MRI demonstrated the presence of brainmetastases in 23 scans. All of the FDG-PET/CT positive cases were confirmed using MRI. In 18 cases suspected lesions were identified as well on FDG-PET as on contrast enhanced CT, while 4 cases were seen on CT only. In determining the existence of brainmetastases, the sensitivity, specificity and accuracy of the FDG-PET/CT scans in comparison with MRI was 96%, 100% and 98% respectively. Conclusions FDG-PET/CT with the use of contrast enhanced CT and acquisition in the venous phase performs well compared with contrast enhanced MRI in demonstrating the presence of brainmetastases in known MM. In case of negative FDG-PET/CT and suspected clinical findings a contrast enhanced MR remains mandatory