Feasibility assessment of real-time surface-guided intrafraction radiotherapy for prostate cancer without body immobilization

Abstract Purpose This study will investigate the feasibility of applying OSMS real-time surface guidance during radiotherapy for prostate cancer without body immobilization. Methods A retrospective analysis of data from 165 fractions of real-time surface-guided radiotherapy for five prostate cancer patients without body immobilization was conducted. Cone-beam computed tomography (CBCT) was used before radiotherapy to assess and correct the patients’ setup errors in 6 degrees of freedom (6-DOF). The OSMS gating system was utilized to monitor the real-time 6-DOF position motion average errors during radiotherapy, with corresponding average values recorded. Post-radiotherapy a verification cone-beam computed tomography (VCBCT) of the body position was performed. Paired sample t-tests were conducted on the OSMS average errors and VCBCT average errors to identify discrepancies. Results The CBCT setup errors before radiotherapy were: Lateral (1.78 ± 1.15) mm, Longitudinal (3.24 ± 1.37) mm, Vertical (2.72 ± 1.49) mm, Yaw (0.56 ± 0.43)°, Roll (0.31 ± 0.32)°, and Pitch (0.32 ± 0.39)°. During radiotherapy, OSMS monitoring shows that the average error of real-time position motion is: Lateral (0.52 ± 0.53) mm, Longitudinal (0.76 ± 0.49) mm, Vertical (1.02 ± 0.71) mm, Yaw (0.27 ± 0.24)°, Roll (0.31 ± 0.32)°, and Pitch (0.58 ± 0.43)°. Post-radiotherapy, VCBCT average errors were: Lateral (0.56 ± 0.57) mm, Longitudinal (0.82 ± 0.54) mm, Vertical (1.01 ± 0.58) mm, Yaw (0.27 ± 0.19)°, Roll (0.32 ± 0.36)°, and Pitch (0.60 ± 0.45)°. The real-time position motion average errors did not significantly differ from the verification average errors (P > 0.05). Conclusions The implementation of OSMS offers a simple and effective method for real-time motion management during radiotherapy for prostate cancer patients without body immobilization.