SU‐E‐T‐730: The Dosimetry Variation Sourced From Different Kinds of TPSs Should Be Pay Attention in Adaptive Radiation Therapy of Non‐Small Cell Lung Carcinoma SBRT

Purpose: The purpose of this work was to study the differences in dosimetry computed with two treatment planning systems (TPSs) in adaptive radiation therapy of non‐small cell lung carcinoma stereotactic body radiotherapy (SBRT). Methods: 3 patients with non‐small cell lung carcinoma SBRT were selected in this study. Some information, including dose‐volume histogram (DVH) data, image data and structure data, were exported from the TPS‐Eclipse 10.0 (Varian Medical Systems, Palo Alto, CA). All data were imported in Image Guided Radiotherapy Workstation Software (IGRTWS 1.0, Shanghai STFK medical device Co, Ltd, China), which is a kind of software in house for adaptive radiation therapy. Then, dosimetry was recalculated by IGRTWS. Results: There is a clinically variation in the small volume organs calculations between this two kinds of software for identical contours. The DVHs of small volume organs were also obviously different. The max dose, the min dose and the mean dose were also obviously different in small volume organs. However, the large volume of organs were less different in volume, DVHs, max dose, min dose and mean dose. Conclusion: We infer that the CT scan slice and pixel widths, the resolution of dose calculation grids and the TPS manufacturer, may be the main influence factors, which lead to the results.The results indicate that we should pay attention to the dosimetry variation sourced from different kinds of TPSs in adaptive radiation therapy of non‐small cell lung carcinoma SBRT, due to which volume of PTV is much smaller than other kinds of cancer PTV usually.