Comparison of region of interest volume between Pinnacle and Eclipse treatment planning system

Objective: To compare the difference region of interest volume (ROI) calculation method between Pinnacle and Eclipse treatment planning system. Methods: To acquire CT image with 3 of slice thickness (1 mm, 3 mm, and 5 mm). Delineate 1, 2 and 5 slices square and circle contours in Pinnacle treatment planning system. Meanwhile 15 cases that include 5 cases with head neck tumor, 5 with thorax tumor and 5 with abdomen tumor were selected. Those image and ROI were transfer to Eclipse treatment plan system by DICOM RT protocol . The ROI volume was compared between two TPS. Results: For ROI with small volume, the volume difference between TPS was obvious (for small volume ROI have 12 times difference, for big volume ROI almost same). The volume difference between TPS was influenced by many factors. The number of ROI slice and the magnitude of ROI was related with the difference between TPS (R2 = 1.000, P = 0.000). The CT thickness (R2 = 0.200, P = 0.972) and the shape of ROI (R2 =0.200, P = 0.089) were not significant factors. The center of ROI on different axis was not affect the volume calculation in Pinnacle, which cause 3% different in Eclipse. The CT thickness was proportional to the ROI volume (Pinnacle R2 = 0.548, P = 0.011; Eclipse R2 = 0.502, P = 0.027). In clinical case, optic chiasm and Len averagely have more than 35% volume difference between those two TPS. Conclusions: We should pay more attention about the difference volume calculation algorithm between Pinnacle and Eclipse, especially when transfer small volume ROI to another TPS, which may have significant difference. (authors)