Purpose: The purpose of this study is to establish and assess a practical delivery quality assurance method for stereotactic radiosurgery with Cyberknife by analyzing the geometric and dosimetric accuracies obtained using a PTW31016 PinPoint ionization chamber and EBT3 films
Methods: 150 cases of delivery quality assurance plans were performed on Cyberknife for assessing point dose and planar dose distribution respectively using a PTW31016 PinPoint ionization chamber and Gafchromic EBT3 films. The measured chamber doses were compared with the planned mean doses in the sensitive volume of the chamber, and the measured planar doses were compared with the calculated dose distribution using gamma index analysis. The gamma passing rates were evaluated using criteria of 3% /1 mm and 2%/2 mm.
Results: For point dose comparison, the averaged dose differences (± standard deviations) were 1.6±0.73% for all the cases. For planar dose distribution, the mean gamma passing rate for 3% /1 mm, and 2% /2 mm evaluation criteria were 94.26% ± 1.89%, and 93.86%±2.16%, respectively. The gamma passing rates were higher than 90% for all the delivery quality assurance plans with the criteria of 3%/1 mm and 2% /2 mm.
Conclusion: PTW31016 PinPoint ionization chamber and EBT3 film can be used for routine Cyberknife delivery quality assurance. The point dose difference should be within 3%. The gamma passing rate should be higher than 90% for the criteria of 3%/1 mm and 2% /2 mm.