Evaluation of Stretcher Alignment in Radiotherapy using Computed Tomography

Currently, a wider and more frequent use of Computed Tomography (CT) volumes are used for planning the radiotherapy treatment of oncological patients. These image volumes are instrumental in positioning the patient and the precise incidence of radiation fields. Any error in such a process will adversely affect the result of the treatment and, consequently, the health of the patient. Therefore, quality control is mandatory throughout this process. As regards image acquisition, the controls are typically executed manually, implying a tedious repetitive task. This problem spurred the need to develop an algorithm that allows eliminating this issue while it evaluates and corrects the main concern as well. Particularly, an algorithm for automatic control of the entire positioning process is proposed here which prevents errors from deviation on both the longitudinal and transversal axes of the arrangement. The alignment will vary according to the anatomical part to be treated and the type of stretcher support, among other aspects. The application was developed by resorting to free software tools (GLP) and the libraries for processing, segmenting and recording of medical images (ITK). The algorithm detects these deviations on both axes by applying threshold methods, morphologic operations and Hough´s Transform. This algorithm is currently operative in the Medical Image Processing Server of the Nuclear Medicine School Foundation (FUESMEN) of Mendoza, Argentina.