Head-to-head comparison of

Purpose: Delayed PET/CT imaging with Methods: Between 2019 and 2024, 65 PCa patients who underwent early (1 h post-injection) and delayed (3 h p.i.) PSMA and FDG scans were retrospectively analyzed. The delayed scans were conducted to clarify unclear findings in early scans or to increase the tumor lesions uptake in negative early scans. All patients were asked to drink 1 L of water between early and delayed scans. The number of primary and metastatic lesions, sensitivity, specificity, diagnostic accuracy, lesions changes in SUV Results: Overall, 83 and 84 lesions characteristic for PCa in 65 patients clearly presented at 1 h and 3 h p.i. in PSMA scans, respectively. 30 and 45 lesions characteristic for PCa in 65 patients clearly presented at 1 h and 3 h p.i. in FDG scans. The 3-hour delayed imaging of FDG found more primary foci than 1-hour imaging but was much less able to detect metastatic foci than PSMA. PSMA was more sensitive than FDG in delayed imaging (96.15% vs. 84.21%), and the diagnostic accuracy for primary foci was higher for PSMA than FDG in delayed imaging (83.87% vs. 73.91%). However, FDG delayed imaging greatly improved the diagnostic accuracy for primary PCa compared to early imaging (73.91% vs.53.33%). PSMA SUV Conclusion: PSMA PET/CT at 3 h p.i. detected the most lesions characteristic of primary PCa, and it showed higher uptake and contrast than FDG. However, to some extent, FDG delayed PET/CT imaging is still important in primary PCa diagnosis, particularly in hospitals without PSMA.