Abstract
OBJECTIVE: Previous studies have shown that increased cardiac uptake of (18)F-fluorodeoxyglucose (FDG) on positron emission tomography (PET) may be an indicator of myocardial injury after radiotherapy (RT). The primary objective of this study was to quantify cardiac subvolume dosimetry and (18)F-FDG uptake on oncologic PET using a 17-segment model of the left ventricle (LV) and to identify dose limits related to changes in cardiac (18)F-FDG uptake after RT. METHODS: Twenty-four esophageal cancer (EC) patients who underwent consecutive oncologic (18)F-FDG PET/CT scans at baseline and post-RT were enrolled in this study. The radiation dose and the (18)F-FDG uptake were quantitatively analyzed based on a 17-segment model. The (18)F-FDG uptake and doses to the basal, middle and apical regions, and the changes in the (18)F-FDG uptake for different dose ranges were analyzed. RESULTS: A heterogeneous dose distribution was observed, and the basal region received a higher median mean dose (18.36 Gy) than the middle and apical regions (5.30 and 2.21 Gy, respectively). Segments 1, 2, 3, and 4 received the highest doses, all of which were greater than 10 Gy. Three patterns were observed for the myocardial (18)F-FDG uptake in relation to the radiation dose before and after RT: an increase (5 patients), a decrease (13 patients), and no change (6 patients). In a pairing analysis, the (18)F-FDG uptake after RT decreased by 28.93 and 12.12% in the low-dose segments (0-10 Gy and 10-20 Gy, respectively) and increased by 7.24% in the high-dose segments (20-30 Gy). CONCLUSION: The RT dose varies substantially within LV segments in patients receiving thoracic EC RT. Increased (18)F-FDG uptake in the myocardium after RT was observed for doses above 20 Gy.