To study the feasibility of defining the internal gross tumor volume for hepatocellular carcinoma applying the enhanced 4DCT images obtained by deformable registration technology

Abstract

Objective To study the feasibility of defining the internal gross tumor volume (IGTV) of hepatocellular carcinoma applying the enhanced four-dimensional computed tomography (4DCT) images with deformable registration technology. Methods Ten HCC patients who accepted radiation therapy were selected in this study. The 4DCT in free breathing, non-enhanced 3DCT and arterial phase enhanced 3DCT in end inspiration breath holding associated with active breathing coordinator were acquired sequentially. 4DCT were sorted into ten series CT images according to breath phase, and named CT00, CT10…CT90. Gross tumor volume (GTV) were contoured on different CT series and the IGTV, was merged by ten phases GTVs of 4DCT. The GTV of enhanced 3DCT was registered to different CT series of 4DCT and the IGTVDR was obtained by merging the GTVs after deformable registration. The target volumes differences were compared by paired t-test. Results The edge of tumor was difficult to define on 4DCT and non-enhanced 3DCT images. The enhanced 3DCT image showed clearer tumor edge, and the GTV increased by mean 37. 99% compared to GTV on 4DCT different series images and non-enhanced 3DCT image (P = 0. 002). The GTV after deformable registration on 4DCT different phase images increased by mean 36. 34% (P = 0. 011) , which were similar to GTV on enhanced 3DCT image (P=0.632). The IGTVDR increased by 19.91% (P= 0.017), compared to IGTV1. Conclusions The contrast-enhanced 4DCT image which was obtained by combining enhanced 3DCT and 4DCT images with deformable registration technology could raise the position precision of the HCC IGTV effectively. Key words: Tomography, X-ray computed, four-dimensional; Deformable registration; Hepatocellular neoplasms/radiotherapy