Abstract:  Background and purpose: Optical surface imaging system is used in image-guided radiotherapy (IGRT). This study aimed to evaluate the clinical applicability of the Catalyst ^TM system and cone-beam computed tomography (CBCT) in tumor radiation therapy. Methods: Thirty-three patients with thorax tumor were fixed with suitable methods at Fudan University Shanghai Cancer Center. Catalyst ^TM system and CBCT acquired the same time images. The images were aligned with simulation planning CT images. These aligned results for images in x, y and z directions for translation error and pitch (PIT), roll (ROL) and rotation (RTN) directions for rotation error were obtained, and means, standard deviations, systemic error and random error were calculated. Paired samples t test was applied to evaluate the differences. Results: The setup errors of CBCT registration in x, y and z translational directions were (0.95±1.18) mm, (1.28±1.63) mm and (0.97±1.20) mm, respectively. The setup errors of CBCT registration in PIT, ROL and RTN rotational directions were (0.73±0.65)°, (1.07±0.86)° and (0.69±0.69)°, respectively. The setup errors of Catalyst ^TM registration in x, y and z translational directions were (0.96±1.35) mm, (1.43±1.66) mm and (1.59±1.98) mm, respectively. The setup errors of Catalyst ^TM registration in PIT, ROL and RTN rotational directions were (0.86±0.80)°, (0.87±0.74)° and (0.75±0.76)°, respectively. The differences in systemic error and random error between the two methods were less than 1 mm. Conclusion: There is no significant difference between the two approaches. Catalyst ^TM could be used as an alternative to CBCT.

Key words: Cone-beam computed tomography, Catalyst ^TM system, Radiation therapy, Setup errors