Comparison of setup accuracy between Catalyst HD and skin markers in stereotactic body radiotherapy of lung cancer

Objective To compare the setup accuracy between Catalyst HD and skin markers in stereotactic body radiotherapy (SBRT) of lung cancer. Methods A total of 24 cases treated with SBRT were selected and all patients were fixed with vacuum pad in the supine position. Patients in group A were positioned by Catalyst HD and those in group B were positioned by shin markers. All patients were matched with the CT images after CBCT scan by rigid registration and the setup errors in six directions (x-, y-, z-axis, Rtn, Pitch and Roll) were obtained. Results The mean±SD in group A and B in the six directions were as follows: (0.13±0.12) cm, (0.25± 0.19) cm; (0.26±0.15) cm, (0.13±0.11) cm; (0.23±0.19) cm, (0.35±0.29) cm; (0.43°±0.40°), (0.80°±0.69°); (0.48°±0.47°), (0.79°±0.64°); (0.62°±0.60°) and (0.88°±0.70°), respectively. Except the x-axis data in group B, all the data in the six directions were not normally distributed. The obtained data significantly differed between two groups (all P 0.5 cm/2°) also significantly differed between two groups (P<0.05). Conclusions The setup errors of Catalyst HD are less than those of the skin markers (except the y-axis). The setup accuracy of Catalyst HD is superior to that of traditional skin markers, which is worthy of application in clinical practice. Key words: Stereotactic body radiotherapy; Catalyst HD system; Setup error