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Objective:To explore the setup errors of vacuum pad combined with breast bracket in linear accelerator intensity-modulated radiotherapy for breast cancer.Methods:The clinical data of 72 patients who received linear accelerator intensity-modulated radiotherapy after breast conserving surgery in Hai'an Hospital of Traditional Chinese Medicine from July 2017 to March 2022 were retrospectively analyzed. According to the radiotherapy fixation schemes, they were divided into vacuum pad group (24 patients), breast bracket group (27 patients) and vacuum pad combined with breast bracket group (21 patients). Cone-beam CT was used to analyze the setup errors of the fixation, and the mean value of the overall errors and the standard deviation of the system errors were calculated. The relative factors affecting the fixed setup errors were analyzed.Results:There were statistical differences among vacuum pad group, breast bracket group and vacuum pad combined with breast bracket group in the level of forward and backward (Z) direction translation error (2.11±0.41, 2.67±0.26 and 1.79±0.21) and Z direction rotation error (1.14±0.24, 1.05±0.21 and 0.91±0.22) ( F values were 45.86 and 6.21, both P < 0.05). The level of Z direction translation error in vacuum pad group was higher than that in vacuum pad combined with breast bracket group, and the difference was statistically significant ( t = 12.37, P = 0.001). The level of Z direction rotation error in breast bracket group was higher than that in vacuum pad combined with breast bracket group, and the difference was statistically significant ( t = 3.41, P = 0.001). In the breast bracket group, the planning target volume (PTV) extension boundary values in the left and right (X), up and down (Y), and Z directions were 2.02, 2.09 and 1.97; the PTV release boundary values in X, Y and Z directions of the vacuum pad group were 1.81, 2.07 and 2.25; the external boundary values of PTV in X, Y and Z directions of the vacuum pad combined with breast bracket group were 1.13, 1.51 and 1.49. The result of multifactor analysis showed that body mass index (BMI) ( OR = 4.208, 95% CI 1.438-12.312) and breast volume ( OR = 4.023, 95% CI 1.375-11.769) were the independent influencing factors of fixed setup errors (both P < 0.05). Conclusions:The application of vacuum pad combined with breast bracket in the fixed setup of linear accelerator intensity-modulated radiotherapy of breast cancer is helpful to reduce the fixed setup errors, but at the same time, the fixed setup errors is affected by the patient's BMI, breast volume and other factors.
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Objective:To retrospectively analyze the setup errors of thermoplastic head and shoulder molds alone or combined with vacuum pad in hypofractionated stereotactic radiotherapy (HFSRT) for non-small cell lung cancer (NSCLC) with brain metastases.Methods:Fifty-four NSCLC patients with brain metastases who received HFSRT from 2017 to 2019 were enrolled in this study. Twenty-four patients were fixed with thermoplastic head and shoulder molds (group A), and 30 patients were fixed with thermoplastic head and shoulder molds plus vacuum pad (group B). The interfraction and intrafraction setup errors were acquired from cone-beam CT online image registration before and after the HFSRT. Optical surface system was applied in monitoring the intrafraction setup errors. The setup errors in each direction between two groups were analyzed by independent samples t-test. Results:For the interfraction setup errors of the whole group, the proportion of the horizontal setup errors of ≥3mm was 7.0% to 15.4% and 7.0% to 12.6% for the rotation setup errors of ≥2°. In group A, the anteroposterior setup error was (1.035±1.180)mm, significantly less than (1.512±0.955)mm in group B ( P=0.009). In group A, the sagittal rotation setup error was 0.665°±0.582°, significantly less than 0.921°±0.682° in group B ( P=0.021). For the intrafraction setup errors of the whole group, the proportion of horizontal setup errors of ≥1mm was 0% to 0.7%, whereas no rotation setup error of ≥1° were observed. In group B, bilateral, anteroposterior and sagittal rotation setup errors were (0.047±0.212)mm, (0.023±0.152)mm and 0.091°±0.090°, significantly less compared with (0.246±0.474)mm, (0.140±0.350)mm and 0.181°±0.210° in group A ( P=0.004, P=0.020, P=0.001), respectively. Optical surface monitoring data were consistent with the obtained results. Conclusions:Thermoplastic head and shoulder molds (with or without vacuum pad) combined with online image registration and six-dimensional robotic couch correction can be applied in HFSRT for brain metastases from NSCLC. The intrafraction setup errors in group B are smaller than those in group A. Optical surface system has certain value in monitoring the intrafractional movement.
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Objective To compare the repeatability of radiotherapy placement between negative pressure vacuum pad (A group) and common soft pillow (B group) combined with a thermoplastic membrane immobilization technology in severe kyphosis patients with head and neck cancer.Methods From September 2013 to December 2014,22 cases of severe kyphosis patients with primary or secondary head and neck cancer who received radiotherapy were randomly divided into group A and group B.Padding waist hips with negative pressure vacuum pad and ordinary soft pillow were used so that the patients could lay in CT-Sim bed,and the head cushion was set on the headrest.After the fixing of thermoplastic head and neck shoulder membrane,CT-Sim was located.Every five times of radiotherapy were accompanied by CT-Sim school position once.In the direction of the last layer of right styloid process center point as the reference point,CT-sim software was used to measure the location change with left and right sides,head,and under direction (x,y,z,respectively) in patients,and the data were analyzed.Results Group A significantly reduced the osseous placement error between tags compared with group B (P ＜ 0.05).The average placement errors were as follows,x:(0.68±0.14) mm vs (1.15±0.77) mm,y:(0.48±0.23) mm vs (1.49±1.24) mm,z:(0.76±0.54) mm vs (2.11±1.02) mm,while the average transfer errors were as follows,x:(0.70±0.21) mm vs (1.15±0.93) mm,y:(0.50±0.31) mm vs (1.50±1.28) mm,z:(0.85±0.26) mm vs (1.77±0.88) mm.Conclusion Vacuum suction pad combined with thermoplastic membrane has good repeatability on radiotherapy positioning for severe kyphosis patients with head and neck cancer.