Application of Optical Surface Monitoring System in Stereotactic Body Radiation Therapy for Liver Metastases Patient.

Stereotactic body radiotherapy (SBRT) in liver tumors has been a challenging treatment due to the diaphragm-induced motion. Optical surface monitoring system (OSMS) provides the functions of positioning and motion management, which has been widely used in recent years because it is non-ionizing, non-invasive and contactless. The purpose of this study was to explore the application of OSMS in liver metastasis patients. 33 liver metastasis SBRT patients, who were treated between August 2019 to September 2021, were divided into two groups. 14 patients in Group A were aligned using skin marking (1 anterior and 2 laterals). 19 patients in Group B were aligned near to the skin marking at the initial step. Next, the 'move couch' function on OSMS was applied if the patient's body rotations were less than 1 degrees according to the OSMS deltas value. The setup errors and setup time were recorded in both groups. Total of 88 and 106 CBCT images in group A and B were analyzed. The absolute setup errors for Groups A and B were (0.21 ± 0.15) cm, (0.37 ± 0.38) cm, (0.35 ± 0.33) cm, (0.8 ± 0.3), (1.2±0.5), (1.8 ± 0.7), and (0.04 ± 0.02) cm, (0.28 ± 0.13) cm, (0.03 ± 0.02) cm, (0.1 ± 0.2), (0.1 ± 0.2), and (0.3 ± 0.4) in vertical, longitudinal, lateral, rotation, pitch and roll directions respectively. Positioning accuracy in Group B is far superior to Group A especially in rotational directions. The difference was statistically significant (p<0.05). The average setup time was 2.8 minutes and 3.0 minutes for Group A and B. There was no significant difference in mean setup time. Setup time using OSMS was gradually improved as more experiences gained by the therapist. The study has proven that OSMS is an effective and efficient tool for liver metastasis patients. It can increase the setup accuracy and reduce repeated setup. Continuous real time monitoring is of high clinical value for liver tumor motion management. [ABSTRACT FROM AUTHOR]