Room: Stars at Night Ballroom 2-3
Purpose: Small field dosimetry presents complications and uncertainties that could be circumvented by using detectors which are smaller than the radiation field. This study evaluated the reproducibility and accuracy of TLD micro-cubes for use in stereotactic radiosurgery (SRS) remote auditing quality assurance (QA) for treatment centers participating in clinical trials.
Methods: The handling process was defined, including: selection of micro-cubes, annealing parameters, and readout techniques. The micro-cubes were characterized based on correction factors for element sensitivity, signal fading, dose response, and energy response. To test the reproducibility and accuracy of the dosimeters, they were first evaluated under a single small field beam in a simple geometric configuration, then in anthropomorphic SRS head phantoms. Agreement between calculated dose and measured dose was evaluated.
Results: 463 micro-cubes were evaluated. Element sensitivity was determined for each individual cube and had an average standard deviation of 0.013 (1.3%). Evaluations of linearity, energy, and fading were conducted and a correction factor for each parameter was determined. These values were compared to the existing TLD-100 powder system currently used in remote audit programs and found to be of comparable accuracy.
Conclusion: The results confirm the viability of TLD-100 micro-cubes as an auditing dosimeter. The guidelines developed have minimized the uncertainty in micro-cube output, giving confidence in reproducibility and accuracy. The TLD micro-cubes will be implemented with the small field output phantoms and anthropomorphic SRS head phantoms for clinical trial audits.
Funding Support, Disclosures, and Conflict of Interest: This work was supported by NCI grant #CA180803