Application of ExacTrac and cone-beam computed tomography image-guided radiotherapy in intensity-modulated radiotherapy for lung cancer

Abstract

Objective To compare set-up error and the positioning and error correction time between the infrared markers automatic positioning+ ExacTrac (A) and the manual positioning+ cone-beam computed tomography (CBCT) image-guided radiotherapy (IGRT)(B) in intensity-modulated radiotherapy (IMRT) for lung cancer. Methods A total of 20 patients with lung cancer were randomly divided into Group A and Group B. In Group A, after automatic positioning, a group of orthogonal X-rays images were taken using kV X-rays, which matched digitally reconstructed radiographs to obtain errors before correction. In group B, after manual positioning, images were taken using CBCT, which matched reference computed tomography images to obtain errors before correction. The positioning and error correction time was recorded in both groups. After error correction, errors after correction were obtained in each group using IGRT. Between-group comparison was made using the paired t test. Results The errors in lateral, longitudinal, vertical, and spinning vertical directions were significantly reduced after correction in both Group A and B (A: 1.8±1.3 vs. 0.4±0.1, P=0.000; 2.7±1.9 vs. 0.5±0.1, P=0.000; 2.8±1.7 vs. 0.4±0.1, P=0.000; 1.6±1.0 vs. 0.3±0.9, P=0.000; B: 2.6±1.9 vs. 0.5±0.5, P=0.000; 3.1±2.5 vs. 0.6±0.6, P=0.000; 2.1±1.8 vs. 0.5±0.5, P=0.000; 0.9±0.7 vs. 0.3±0.1, P=0.000). There were no significant differences in errors after correction between Group A and Group B (0.4±0.1 vs. 0.5±0.5, P=0.204; 0.5±0.1 vs. 0.6±0.6, P=0.257; 0.4±0.1 vs. 0.5±0.5, P=0.518; 0.3±0.9 vs. 0.3±0.1, P=0.755). However, the positioning and error correction time in Group A was significantly shorter than that in Group B (199.1±16.2 vs. 315.2±13.7, P=0.000). Conclusions The application of ExacTrac or CBCT IGRT can substantially reduce set-up errors and improve set-up accuracy in IMRT. In addition, the application of the ExacTrac system can substantially shorten the positioning and error correction time. Key words: Lung neoplasms/intensity-modulated radiotherapy; ExacTrac; CBCT; Set-up errors; Positioning and error correction time