Radiation-induced lung injury on PET/CT: Analysis of FDG uptake response within specific isodose regions of irradiation in non-small cell lung cancer patients ; PET/BT'de radyasyona bağlı akciğer hasarı: Küçük hücreli dışı akciğer kanseri hastalarında belirli eş doz radyasyon bölgelerinde FDG tutulum yanıtının analizi

Objective: Inflammatory response associated with radiation-induced lung injury (RILI) results in an increased 18F-fluorodeoxyglucose (FDG) uptake on positron emission tomography/computed tomography (PET/CT). In this study, we aimed to analyze the degree of FDG uptake within specific isodose regions (IR) of the irradiated lung using standardized uptake value (SUV) measurements, and to correlate posttreatment FDG uptake with radiotherapy (RT) dose parameters, patient characteristics and the imaging time interval after RT completion. Material and Methods: Data from 30 patients with non-small cell lung cancer (NSCLC) who underwent FDG PET/CT imaging at least 12 weeks (72-668 days) after completion of RT were evaluated. In each patient, side-by-side visual registration of the treatment planning CT slices including IR curves with the corresponding PET/CT slices was performed. Using SUV measurements, FDG uptake levels were analyzed within specific IRs of the irradiated lung. The statistical difference between SUVmax of each IR was determined. The RT dose parameters, patient characteristics and time interval between RT and PET/CT were tested for correlation with SUVmax of IRs. Results: The mean SUVmax in the IRs of the lung that received 2000-4000cGy was 1.51 +/- 0.66 (mean +/- SD) (mm-max: 0.69-2.84), 4000-6000cGy was 2.67 +/- 1.16 (min-max: 0.71-6.0), and >6000Gy was 3.55 +/- 1.09 (min-max: 1.2-5.72). We found statistically significant differences between the SUVmax values of all IRs (SUV2000 vs. SUV4000, p = 0.001; SUV2000 vs. 6000, p = 0.002; SUV4000 vs. 6000, p = 0.001). No statistically significant correlation was found between SUVmax and the other variables. Conclusion: The findings of this study showed that, although some overlap occurs between IRs, the degree of radiation-related parenchymal FDG uptake gets higher with increasing dose levels. Persistent high FDG uptake levels may be observed in radiation fibrosis areas on PET/CT even several months after RT. ; Amaç: Radyasyona bağlı akciğer hasarı (RBAH) ile ...