Abstract:
Objective To compare the differences in interfraction setup accuracy and setup time between lung cancer patients treatedwith stereotactic body radiotherapy using thermoplastic masks and vacuum cushion system.
Methods A retrospective study was performed on 121 patients during January 2015 to November 2016 and included thermoplastic fixation mask for 43 cases and vacuum fixation cushion for 78 cases.Before irradiation, a kilovoltage cone-beam computed tomography(KV-CBCT)scan was performed and image registration was done automatically and manually to obtain setup errors from the X, Y, and Z axes.The differences of setup errorsbetween the two immobilization methods were analyzed and the setup time was recorded.
Results The setup errors for thermoplasticmasks and vacuum cushion in the X, Y, and Z axes were(0.16±0.09 versus 0.25±0.11) cm(P < 0.05), (0.27±0.13 versus 0.25±0.15) cm(P > 0.05), and(0.19±0.13 versus 0.26±0.12) cm(P < 0.05), respectively.The setup time for thermoplastic masks and vacuum cushion were(57.66 versus 58.09) s(P > 0.05).
Conclusion Thermoplastic masks offer better reproducibility and significantly less interfractional setup displacement than vacuum cushions in the X and Z axes.No significant difference was found in the Y axis.Moreover, thesetup time of thermoplastic masks is less than vacuum cushions.The thermoplastic mask is the best choice if the age and cardio-pulmonary function of patients can be ignored.