Verification of CyberKnife Dose Distributions with Gafchromic EBT2 Film

Abstract

OBJECTIVECyberKnife (CK) system is more sophisticated than the conventional methods; therefore, strict qualityassurance tests are required. To ensure that the treatment is delivered as planned, the verification of thetreatment plan should be performed with specific dosimetry tools. This study aims to verify the CKtreatment plans generated for patients with intracranial tumors using Gafchromic EBT2 film.METHODSThe CK plans of ten patients with intracranial tumors were selected for this study. The plans were transferred to computed tomography images of the anthropomorphic head phantom. The phantom containing the film was irradiated using 6D skull tracking method. The dose distributions calculated by TPSwere compared with those measured by film using gamma analysis method.RESULTSIn the gamma-index method, the average passing rate for the 3%/3 mm criterion was found to be93.9±4.8%. The gamma passing rate for Iris-collimator-based plans yielded slightly lower than that forfixed-collimator-based plans.CONCLUSIONIn conclusion, this study indicates that Gafchromic EBT2 film is a utilizable dosimeter for quality assurance of the CK treatment plans. It is recommended to use the EBT2 film for verification of the CKtreatment plans before delivery to the patient.