A comparative study of four-and three-dimensional computed tomography simulation in determining displacement and volume for target region of primary tumor in esophageal carcinoma

The current study aimed to compare internal gross target volume (IGTV) and its displacement of primary esophageal carcinoma based on fourand three-dimensional computed tomography (4D-CT and 3D-CT) simulation technology. Twenty-two esophageal carcinoma patients proved by pathology examination were included in this prospective study. Each patient sequentially received contrast enhancement free-breathing 3D-CT and respirationsynchronized 4D-CT simulation chest scan. The target volume and displacement in three orthogonal dimensions of three different IGTVs planning methods (including IGTV4D, IGTV4D’ and IGTV3D) were obtained, followed by the calculation of dice similarity coefficient (DSC) and overlap index (OI) between IGTV4D and IGTV4D’ IGTV4D and IGTV3D respectively for different segments of carcinoma. Statistical analysis was made through the Friedman test, variance analysis on repeated measurement data and paired-samples student t test and the difference was regarded as of statistical significance when P < 0.05. There was statistical significance of displacement at left-right, anterior-posterior, and superior-inferior directions of primary esophageal tumor GTV of the ten phases originated from medium-thoracic segments and medium-lower-thoracic segments (P = 0.005 and P = 0.001). There presented a significant difference of primary tumor volume where appeared IGTV3D > IGTV4D > IGTV4D’ (P < 0.05). In other words, the implementation of GTV by means of extending position based on 3D-CT imaging would lead to unnecessary radiation of the surrounding normal tissues (about 9-24%); However, the application of GTV only by means of integrating end-inhalation and end-exhalation phases would result in uncover target area (about 10-34%). 4D-CT simulation technology is superior to 3D-CT simulation technology for Intensity Modulated Radiation Therapy (IMRT) in esophageal cancer.