SU‐E‐J‐55: Gradient‐Based Delineation of the Primary GTV on FLT‐PET in Esophageal Cancer and Influence to Radiotherapy Planning
Purpose: The aim of this study was to validate a gradient‐based segmentation method for GTV delineation on FLT‐PET in EC through surgical specimen, in comparison with threshold‐based approaches and CT. Discuss the influences of gradient‐based methods delineate the primary GTV to radiotherapy planning. Methods: Ten patients with esophageal carcinoma treated with radical surgery were enrolled and detected by 18F‐FLT PET/CT before operation transferred the images to MIM software. For each patient, four GTVs were defined. GTV‐ct was based on CT data alone. GTV‐GRAD, GTV‐1.4, GTV‐30%max were automatically segmented on PET images using the gradient‐based method, fixed threshold values at 1.4 and 30% of SUVmax, respectively. The GTV‐GRAD, GTV‐1.4, GTV‐30%max were compared with GTV‐CT by overlap index. Lengths of GTVs were recorded as LCT, LGRAD, L1.4, L30%max, respectively. The length of surgical specimen was recorded as LPath, and compared with LCT, LGRAD, L1.4, L30%max. Next, two radiotherapy plans were designed for each patient based on GTV‐GRAD (plan‐GRAD) and GTV‐CT (plan‐CT). The radiationdose was prescribed as 60 Gy in 30 fractions. The dose‐volume parameters of target volume and normal tissues, CI and HI of plan‐GRAD and plan‐CT were compared. Results: The mean LPath was 6.47±2.7. The mean Lct, LGRAD, L1.4 and L30%max were 7.17±2.28, 6.22±2.61, 6.23±2.80, 5.95±2.5.The correlation coefficients were 0.862, 0.989, 0.920 and 0.920 when compared with LPath, respectively. The overlap index of GTV‐GRAD,GTV‐1.4,GTV‐30%max when compared with GTV‐CT were 0.75±0.12, 0.71±0.12, 0.57±0.10.The values for mean lungdose, total‐lung volume receiving more than 5, 10, 20, and 30Gy, mean heartdose and heart volume receiving more than 30Gy of plan‐GRAD were significant lower than plan‐CT. Conclusions: The gradient‐based method provided the closest estimation of GTV length. The gradient‐based method radiotherapy planning reduced the irradiated volume in the lung,heart and other normal tissues.