ABSTRACT
Objective To explore the setup errors of two different position fixing techniques in radiotherapy for thoracic canc -er, and analyze and compare the accuracy and repeatability of the two different techniques .Methods Sixty four patients with thoracic cancer were selected in our hospital from December 2011 to June 2013 .All patients received radiotherapy .Patients were divided into two groups by means of random number table .Each group had 32 cases.The low-temperature thermoplastic membrane group used ther-moplastic membrane method to fix position while vacuum bag group with negative pressure fixed position by vacuum bag method .The setup errors in the right/left direction (X-axis), anterior/posterior direction (Z-axis), head/foot direction (Y-axis) and three dimen-sional directions ( I) were compared and analyzed between the two groups .Results The low-temperature thermoplastic membrane group was able to reduce the setup errors significantly in the Z-axis (1.13 ±0.33 /2.33 ±1.24, P 0.05).Conclusions Position fixing technique with low-temperature thermoplastic membrane can help to fix position in radiotherapy for thoracic cancer , reduce the setup errors in the Z-axis, and improve the setup accuracy .