Determination of geometric accuracy of radiotherapy fields by port film and DRR using Matlab Graphical User Interface

Abstract

Introduction: Radiation therapy is one of the methods of cancer treatment. In this method, it is necessary to avoid harming the healthy tissues of the patient which is in the vicinity of the target, as much as possible. Treatment verification is one of the most important steps of radiation therapy which has two usual methods, using Port film and EPID. The accuracy and precision of treatment in EPID-less centers are usually of concern. By entering EPID into the treatment verification process, no more studies have been done for increasing the precision of treatment verification by using port film. The purpose of this study is to determine and verify the exact location of radiation therapy fields by using port-film and DRR as low cost equipment.

Method and Materials: Initially, by writing appropriate algorithm for port film in the megavoltage irradiation, detectable contrast was created for the image and then by using appropriate markers and developing program by MATLAB as DRR Port Registration, Semi-automatic and automatic registration between port- film and DRR images were performed for Pelvic and Chest phantoms and the results were compared withEPID consequences in similar conditions.

Results: By using this software, DRR and port film as treatment verification tools, the precision of treatment verification and accuracy of radiation therapy fields were achieved in the extent of the millimeter. The study of validation results with EPID demonstrated that the mean absolute average error in angle is equal to 0.5926 degrees, 1.703 mm in the X direction and 2.42716 mm in the Y direction. Also, the mean absolute average errors in MATLAB validation is equal to 0.2 degrees, 0.75 mm in the X direction and 0.81 in the Y direction and 0.228% in scale.

Conclusion: The results of this study illustrated that using this software and suitable low-cost hardware in the centers with lack of EPID can increase the precision of treatment verification to the millimeter and it can be introduced as a suitable alternative for EPID in centers for increasing treatment accuracy.