Determination of an Optimal Standardized Uptake Value of Fluorodeoxyglucose for Positron Emission Tomography Imaging to Assess Pathological Volumes of Cervical Cancer: A Prospective Study

PURPOSE: To determine the optimal standardized uptake value (SUV) of (18)F-fluorodeoxyglucose ((18)F-FDG) for positron emission tomography (PET) imaging, at which the PET-defined gross tumor volume (GTV(PET)) best matches with the pathological volume (GTV(PATH)) in the cervical cancer. MATERIALS AND METHODS: Ten patients with the cervical cancer who underwent surgery were enrolled in this study. The excised specimens were processed for whole-mount serial sections and H-E staining. The tumor borders were outlined in sections under a microscope, histopathological images were scanned and the GTV(PATH) calculated. The GTV(PET) was delineated automatically by using various percentages relative to the maximal SUV and absolute SUV. The optimal threshold SUV was further obtained as the value at which the GTV(PET) best matched with the GTV(PATH). RESULTS: An average of 85±10% shrinkage of tissue was observed after the formalin fixation. The GTV(PATH) was 13.38±2.80 cm(3) on average. The optimal threshold on percentile SUV and absolute SUV were 40.50%±3.16% and 7.45±1.10, respectively. The correlation analysis showed that the optimal percentile SUV threshold was inversely correlated with GTV(PATH) (p<0.05) and tumor diameter (p<0.05). The absolute SUV was also positively correlated with SUV(max) (p<0.05). CONCLUSION: The pathological volume could provide the more accurate tumor volume. The optimal SUV of FDG for PET imaging by use of GTV(PATH) as standard for cervical cancer target volume delineation was thus determined in this study, and more cases are being evaluated to substantiate this conclusion.