18F-FDG PET/CT oncologic imaging at extended injection-to-scan acquisition time intervals derived from a single-institution 18F-FDG-directed surgery experience: feasibility and quantification of 18F-FDG accumulation within 18F-FDG-avid lesions and background tissues.

BACKGROUND: 18F-fluorodeoxyglucose (18F-FDG) positron emission tomography/computed tomography (PET/CT) is a well-established imaging modality for a wide variety of solid malignancies. Currently, only limited data exists regarding the utility of PET/CT imaging at very extended injection-to-scan acquisition times. The current retrospective data analysis assessed the feasibility and quantification of diagnostic (18)F-FDG PET/CT oncologic imaging at extended injection-to-scan acquisition time intervals. METHODS: (18)F-FDG-avid lesions (not surgically manipulated or altered during (18)F-FDG-directed surgery, and visualized both on preoperative and postoperative (18)F-FDG PET/CT imaging) and corresponding background tissues were assessed for (18)F-FDG accumulation on same-day preoperative and postoperative (18)F-FDG PET/CT imaging. Multiple patient variables and (18)F-FDG-avid lesion variables were examined. RESULTS: For the 32 (18)F-FDG-avid lesions making up the final (18)F-FDG-avid lesion data set (from among 7 patients), the mean injection-to-scan times of the preoperative and postoperative (18)F-FDG PET/CT scans were 73 (± 3, 70-78) and 530 (± 79, 413-739) minutes, respectively (P < 0.001). The preoperative and postoperative mean (18)F-FDG-avid lesion SUV(max) values were 7.7 (± 4.0, 3.6-19.5) and 11.3 (± 6.0, 4.1-29.2), respectively (P < 0.001). The preoperative and postoperative mean background SUV(max) values were 2.3 (± 0.6, 1.0-3.2) and 2.1 (± 0.6, 1.0-3.3), respectively (P = 0.017). The preoperative and postoperative mean lesion-to-background SUV(max) ratios were 3.7 (± 2.3, 1.5-9.8) and 5.8 (± 3.6, 1.6-16.2), respectively, (P < 0.001). CONCLUSIONS: (18)F-FDG PET/CT oncologic imaging can be successfully performed at extended injection-to-scan acquisition time intervals of up to approximately 5 half-lives for (18)F-FDG while maintaining good/adequate diagnostic image quality. The resultant increase in the (18)F-FDG-avid lesion SUV(max) values, decreased background SUV(max) values, and increased lesion-to-background SUV(max) ratios seen from preoperative to postoperative (18)F-FDG PET/CT imaging have great potential for allowing for the integrated, real-time use of (18)F-FDG PET/CT imaging in conjunction with (18)F-FDG-directed interventional radiology biopsy and ablation procedures and (18)F-FDG-directed surgical procedures, as well as have far-reaching impact on potentially re-shaping future thinking regarding the "most optimal" injection-to-scan acquisition time interval for all routine diagnostic (18)F-FDG PET/CT oncologic imaging.