Application of modified tracking components in CyberKnife treatment of thoracic and abdominal tumors

Objective To improve synchrony tracking components of CyberKnife (tracking vest and tracking markers) and to analyze the clinical application value of the improved tracking components in CyberKnife treatment of thoracic and abdominal tumors. Methods The tracking apron was made of knitted four-side elastic spandex cloth and suture design of Velcro, which was used to stick the tracking markers on the chest and abdomen of patients. The tracking markers added a 2 cm thick light foam block to the bottom of the original markers, and then the hook face of the Velcro was fixed to the bottom of the light foam. The improved trace component (the improved component) and the original component (the vendor component) were applied to the lung tracking treatment model, and the manufacturer components were included in the reference group. Adoption of improved components into the observation group; 20 different types of respiratory waveforms were simulated and applied to the same mold plan. After treatment, the coverage rate, mean standard deviation, maximum standard deviation and the slope of XYZ-axis vs. R correlation graph were recorded. The relevant parameters of Synchrony model and wearable time of two components were compared, and the application significances of the improved tracking component in the breathing tracking process of the CyberKnife were evaluated. Results The maximum slope [median(interquartile range)] of XYZ-axis vs. R related graph in the reference group was 0.73 (3.89), 0.27 (0.49) and 0.34 (1.02), respectively. The maximum slope of XYZ-axis vs. R related graph in the observation group was 0.70 (2.78), 0.31 (0.30) and 0.36 (0.75), respectively. There was no statistically significant difference in the slope of XYZ-axis vs. R between the reference group and the observation group (all P > 0.05). There was no significant difference in the average standard error and maximum standard error between the reference group and the observation group [(1.7±0.4) mm vs. (1.7±0.5) mm, t=-0.382, P= 0.710; (2.0±0.6) mm vs. (1.7±0.5) mm, t=-0.877, P= 0.401], and the difference of the model coverage rate between the two groups was statistically significant [(48±18)% vs. (60±22)%, t= 2.762, P= 0.042]. The setup time of tracking components in the observation group was less than that in the reference group, and the difference was statistically significant [(44±24) s vs. (81±15) s, t=-4.310, P= 0.001]. Conclusions The improved tracking components are comparable to the manufacturer tracking components in the standard error of the Synchrony model. The improved components shorten the wear time and appropriately improve the coverage of the Synchrony model. Key words: Thoracic neoplasms; Abdominal neoplasms; CyberKnife; Stereotactic body radiation therapy; Standard error; Synchrony model