Objective:To explore the movement patterns and factors influencing lung tumors tracked using the M6 cyberknife stereotactic radiotherapy(SRT)system and to provide a reference for the implementation of precise stereotactic radiotherapy for lung tumors.Method:A retrospective analysis was conducted on 29 patients with lung tumors who were treated using x-sight lung tracking technology and the M6 cyberknife SRT system at Tianjin Medical University Cancer Institute&Hospital,from January 2022 to August 2024.The tumor location and volume,irradiation dose,isodose line,and number of divisions were recorded.Lung tumor location and SPSS 26.0 software were used to analyze the movement amplitude of tumors in the left and right(LFT/RGT,LR)directions,the anterior-posterior(ANT/POS,AP)direction,and the superior-inferior(SUP/INF,SI)direction.The results are expressed as the mean±standard deviation((x)±s)mm,and a t-test was used for inter-group comparisons.Multiple linear regression was used to analyze the effects of factors such as age,gender,tumor location(upper and lower lungs),and tumor volume on the amplitudes of the lung tumor movements.Result:The average motion amplitudes in the LR direc-tions,AP direction,and SI direction of the tumor target areas were(3.5±1.8)mm,(5.3±1.7)mm,and(7.3±5.4)mm for the upper lung,based on 19 cases,and(3.1±1.6)mm,(4.5±2.2)mm,and(12.2±4.4)mm for the lower lung,based on 10 cases,respectively.There was a statistic-ally significant difference(P=0.015 3)in the amplitude of movements between the lower and upper lung tumors in the SI direction.The lung tumor movement amplitude in the SI direction was influenced by tumor location(P=0.035),and the movement amplitudes in the LR direc-tions and the AP direction were not related to factors such as gender,age,tumor location,and tumor volume.Conclusions:The lung tumor movement amplitudes for the different locations varied depending on the respiratory movement shown by the patient.In the SI direction,the movement amplitude of the lower lung tumors was greater than that of upper lung tumors,and this was due to tumor location effects.The movement amplitudes of the lower and upper lung tumors were similar in the LR directions and AP directions.Furthermore,movement amplitude was not affected by gender,age,tumor location,and tumor volume.

Objective:To explore the movement patterns and factors influencing lung tumors tracked using the M6 cyberknife stereotactic radiotherapy(SRT)system and to provide a reference for the implementation of precise stereotactic radiotherapy for lung tumors.Method:A retrospective analysis was conducted on 29 patients with lung tumors who were treated using x-sight lung tracking technology and the M6 cyberknife SRT system at Tianjin Medical University Cancer Institute&Hospital,from January 2022 to August 2024.The tumor location and volume,irradiation dose,isodose line,and number of divisions were recorded.Lung tumor location and SPSS 26.0 software were used to analyze the movement amplitude of tumors in the left and right(LFT/RGT,LR)directions,the anterior-posterior(ANT/POS,AP)direction,and the superior-inferior(SUP/INF,SI)direction.The results are expressed as the mean±standard deviation((x)±s)mm,and a t-test was used for inter-group comparisons.Multiple linear regression was used to analyze the effects of factors such as age,gender,tumor location(upper and lower lungs),and tumor volume on the amplitudes of the lung tumor movements.Result:The average motion amplitudes in the LR direc-tions,AP direction,and SI direction of the tumor target areas were(3.5±1.8)mm,(5.3±1.7)mm,and(7.3±5.4)mm for the upper lung,based on 19 cases,and(3.1±1.6)mm,(4.5±2.2)mm,and(12.2±4.4)mm for the lower lung,based on 10 cases,respectively.There was a statistic-ally significant difference(P=0.015 3)in the amplitude of movements between the lower and upper lung tumors in the SI direction.The lung tumor movement amplitude in the SI direction was influenced by tumor location(P=0.035),and the movement amplitudes in the LR direc-tions and the AP direction were not related to factors such as gender,age,tumor location,and tumor volume.Conclusions:The lung tumor movement amplitudes for the different locations varied depending on the respiratory movement shown by the patient.In the SI direction,the movement amplitude of the lower lung tumors was greater than that of upper lung tumors,and this was due to tumor location effects.The movement amplitudes of the lower and upper lung tumors were similar in the LR directions and AP directions.Furthermore,movement amplitude was not affected by gender,age,tumor location,and tumor volume.

Objective:To provide a new morning check method for the output dose stability of the multileaf collimator (MLC) of the CyberKnife M6 (CK-M6) system.Methods:The CT images of a verification phantom with a size of 20 cm × 20 cm × 10 cm were transmitted into the Precision Treatment Plan ning System (ver. 1.1.1.1). The high-precision alignment between the accelerator output front and the fixed position of the phantom surface was achieved using the fiducial tracking method. A 10 cm × 10 cm radiation field was formed by the MLC and a DailyCheck plan with an output of 200 MU was designed. The repeatability, sensitivity, and accuracy of the DailyCheck plan were measured, and the CK-M6 system was continuously tested for one month using the artificial fixed method and the DailyCheck plan designed in this study. Results:The average and the standard deviation of 10 repeated measurements by the DailyCheck plan were 492.28 pC and 0.09, respectively, indicating good stability. There was a linear correlation between the measured values and the output dose, with a correlation coefficient of R2 > 0.999. Moreover, there was a position deviation of 2 mm between the phantom and the accelerator output front, and the result ant effect on the measured values was equivalent to a dose deviation caused by an output of 1.24 MU. The result from the continuous measurement of both the artificial fixed method and the DailyCheck plan fell within permissible limits, showing high consistency. Conclusions:The DailyCheck plan established through the fiducial tracking of a verification phantom can achieve the convenient, quick, and accurate daily detection of the output dose stability of the MLC of CK-M6. Therefore, this method can be widely applied in the clinical quality control of the CK-M6 system.