A study on position variation of liver cancer and interested structures during respiration by 4DCT and 3DCT.

Abstract

e13529 Background: The movement of liver cancer targets could be infected by respiration.The aim of this study was to investigate the position difference of liver cancer in free-breathing condition between 3DCT and 4DCT simulation, and to investigate the correlation of position movement of primary tumor with normal tissues and skin markers. Methods: 12 patients with liver cancer after TACE were scanned at free breath condition by simulation 4DCT and 3DCT. A coordinate system was created based on image of T20 (maximum intensity projection) reconstructed from 4DCT, gross tumor volume (GTV), normal tissues and skin markers of end expiration, end inspiration and T20 of 4DCT and 3DCT were contoured. The three dimensional position variation of them were measured and their correlation were analyzed. Results: Corresponding to target position of T20, the targets position of end expiration and end inspiration were different from 3DCT in x-axis(χ2=2.552, p=0.579), y-axis(χ2=6.938, p=0.031), z-axis(χ2=10.606, p=0.005). The target movement range of liver cancer in three dimensional direction was different, that was 8.44±6.52mm in z-axis, 3.78±3.07mm in y-axis, 1.11±1.27mm in x-axis,. 9.88±6.43mm in three dimensional vector. There was statistical significant correlation for movement range of GTV with that of liver, gallbladder, right diaphragmatic dome and right skin marker(r=0.738-0.922, p=0.037-0.001), but there was no significant correlation for movement range of GTV with that of kidney, pancreas, spleen, and middle skin marker. Conclusions: Corresponding to target position of T20, there was great difference between individual GTV position of 3DCT and 4DCT. What's more, it was not all of the movement of abdominal normal tissues correlated to the movement of GTV. These uncertain factors may infer dose mapping of GTV and abdominal risk organs.