Analysis of Position Error in Breast Cancer with Intensity Modulated Radiation Therapy

Abstract

The the position error plays an important role in the therapy of breast cancer with intensity-modulated radiation therapy(IMRT) by image-guided technique. In order to explore the methods of reducing the position error, fifteen breast cancer patients with image-guided radiotherapy were selected in this study. The images of patients were scanned using the Versa HD imaging system. The position errors were obtained and analyzed by comparing the images between the simulating CT images and the Versa HD images in four directions, X (left and right), Y (head and foot), Z (belly back) and RTN (rotation angle). It is found that the frequencies of the absolute values of the X, Y, and Z direction position errors exceed 1mm are 40%, 66.6%, and 60%, respectively, and the frequencies of which exceed 2mm are 26.6%, 26.6%, and 60%. The average values of the errors of X, Y, Z, and RTN are 0.91mm, 1.45mm, 2.57mm, and 0.39deg, respectively. The position error takes place most in the Y direction, and least in the X direction. According to the differences between the simulating CT images and the Versa HD images, the position errors were obtained and analyzed. The relations between the errors and the directions can by applied in the real-time correction of the treatment of breast cancer patients with image guidance technique.