Abstract
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Objectives To explore the diagnostic value of 18F-FDG PET/CT delayed imaging after forced diuresis in detecting primary bladder tumor.
Methods 14 patients with primary bladder tumor (cT1~3N0M0) confirmed by pathology were retrospectively analyzed. All patients underwent a standard FDG PET/CT followed by a delayed pelvic imaging after administration of 20 mg furosemide intravenously and extra water intake of about 600~800 ml. SUVmax of the bladder lesion equaled to ±10% of the urine radioactivity was defined as moderate uptake, greater than 10% was high uptake, and less than 10% was low uptake. Bladder tumor with high FDG uptake was considered as positive for malignancy. Correlation of FDG PET/CT with pathology was performed.
Results 14 cases included 12 (85.7%) malignant and 2 (14.3%) benign tumors, the former consisted of 11 (78.6%) urothelium carcinomas and 1 (7.1%) squamous cell carcinoma, the latter were papillary epitheliomas. In standard PET/CT imaging, 3 of 12 malignancies (figure1a) but not the other 9 cases (figure 2a) showed a high FDG uptake, and the 2 benign tumors showed a moderate or low uptake. Thus, sensitivity, specificity, and accuracy were 25.0%, 100.0%, and 35.7% respectively. The diameter of 3 malignancies with high FDG uptake was greater than the other 9 with low or moderate uptake (Z=-2.315, P=0.021) . In delayed pelvic imaging after diuresis, a dramatic reduction of urinary bladder activity occured. 11 of 12 malignancies manifested a high FDG uptake (figure1b, 2b) except 1, the uptake of 2 benign lesions was equivalent to early imaging. Therefore, sensitivity, specificity, and accuracy were 91.7%, 100.0%, and 92.9% respectively.
Conclusions 18F-FDG PET/CT delayed imaging after diuresis and oral hydration contributes to differential diagnosis of primary bladder tumor, which is superior to FDG PET/CT standard imaging significantly.