Verification of CyberKnife Dose Distributions with Gafchromic EBT2 Film

OBJECTIVE CyberKnife (CK) system is more sophisticated than the conventional methods; therefore, strict quality assurance tests are required. To ensure that the treatment is delivered as planned, the verification of the treatment plan should be performed with specific dosimetry tools. This study aims to verify the CK treatment plans generated for patients with intracranial tumors using Gafchromic EBT2 film. METHODS The 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 TPS were compared with those measured by film using gamma analysis method. RESULTS In the gamma-index method, the average passing rate for the 3%/3 mm criterion was found to be 93.9 +/- 4.8%. The gamma passing rate for Iris-collimator-based plans yielded slightly lower than that for fixed-collimator-based plans. CONCLUSION In 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 CK treatment plans before delivery to the patient.