Influence of CT Window Techniques on Gross Tumor Volume Delineation of Lung Cancer

摘要

To determine the variation in delineation of the gross tumor volume(GTV) of lung cancer on CT images with different window width(WW) and window level(WL). Methods: (1) Ten lung cancer cases for conformal radiotherapy (CRT) were selected for simulation CT scanning, then GTVs were delineated by a radiation oncologist under twelve different WW and WL conditions in the treatment planning system(TPS). The GTVs were calculated and analyzed. (2) A wax ball was made to simulate the lesion in lung. After scanning under the same conditions, the outline of ball was delineated with different WW and WL used before in the TPS. The measured values were calculated and compared with the real ball volume. Results: (1) A high variability of GTV under different WW and WL conditions was found, the ratio of the largest to the smallest volume was more than 2 in five patients. About the vary range of GTV volume compared with its mean value in each patient, there were 28% volume values larger than ±20%. (2)The measured volumes of wax ball change with WW or WL. The ratio of the largest to the smallest volume was 1.35. Conclusions: The influences in the GTV delineation caused by CT window techniques can not be ignored, so the optimal choice of WW and WL is significant for the accurate delineation of GTV.