Value of delayed PET/CT on diluted and filled bladder for the detection of bladder cancer

Objective To evaluate the value of increased threshold of SUVmax and delayed imaging on diluted and filled bladder for improving the detection of bladder cancer with 18F-FDG PET/CT.Methods From July 2007 to October 2012,18 F-FDG PET/CT was performed on 63 suspected or treated (with bladder preserved) bladder cancer patients (55 males,8 females,average age 69.1 years).After routine imaging,all patients were given 1 500-2 000 ml of water orally three times and voided three times.Then they underwent delayed pelvic imaging at a full bladder status.The routine images were reanalyzed with increased SUVmax threshold (from 6-8 to 8-20).The final diagnosis was confirmed by pathology or follow-up (＞6 months).The differences of SUVmax in urine,18 F-FDG metabolism in lesions between routine and delayed imaging were compared.Paired t test was used to compare their differences.Results The SUVmax of urine on routine and delayed imaging was 15.11±11.11 and 4.73±2.00 respectively (t=4.15,P＜0.01).Among the 63 patients,there were 15 malignant and 3 benign cases confirmed by pathology,and 45 patients without obvious abnormality during follow-up.All 18 cases were detected by 18F-FDG PET/CT including the 3 benign false positive cases (2 were positive by CT though negative by PET,and 1 FDG-avid cystitis).All 15 true positive cases were confirmed as primary or recurrent bladder carcinoma and 1 false positive case as inflammation.The detection rates of early imaging with routine and increased display threshold of SUVmax were 18.8％(3/16) and 43.8％(7/16),respectively.Conclusion Increased SUVmax threshold for display and delayed imaging with diluted urine under full bladder status could effectively improve the detection rate of primary or recurrent bladder cancer with 18F-FDG PET/CT. Key words: Bladder diseases;  Tomography, emission-computed ;  Tomography, X-ray computed ;  Deoxyglucose