Comparative evaluation of CT and CT/MR DWI images for GTV delineation in precision radiotherapy for esophageal squamous cell carcinoma

Abstract

Objective To evaluate the difference between CT and CT/MR DWI images for gross tumor volume (GTV) delineation in precision radiotherapy for esophageal squamous cell carcinoma.Methods 20 patients with pathologically confirmed as esophageal squamous cell carcinoma were selected for target delineation.The GTV based on CT and CT/MR DWI images of the patients were delineated by six radiation oncologists.The mean,standard deviation,coefficient of variation (CV =standard deviation/mean) of GTV volume,the ratio of minimum value and maximum value (ratio =maximum value/minimum value) of the GTV volume were calculated.And the CV and ratio of the GTV by the two methods were compared.Results The biggest difference of GTV volume on CT and on CT/MR DWI images was 55.71 and 13.89 cm3 (F =12.80,P ＜ 0.05).The CV on CT and CT/MR DWI images were 0.30 ± 0.08,0.11-±0.04 (Z =-3.92,P ＜ 0.05),and the ratio of GTV volume were 2.38 ± 0.62,1.34 ± 0.13,respectively (Z =-3.92,P ＜ 0.05).Conclusions CT/MR DWI images could display GTV more directly,which may help to increase consistency of GTV for esophageal squamous cell carcinoma delineation among different radiation oncologists. Key words: Target delineation; Esophageal neoplasm; Diffusion-weighted magnetic resonance imaging; Image fusion