TU‐D‐AUD C‐09: In‐Vivo Dosimetry Using Aluminum Oxide Detectors

Abstract

Purpose: The purpose of this study was to determine if aluminum oxide detectors could be used for in‐vivo dosimetery. The first specific aim of this project was to characterize the performance of a commercially available aluminum oxide detector system for in‐vivo dosimetry. The second specific aim of this study was to compare the accuracy of the new aluminum oxide detector to a commercially available MOSFET system in side‐by‐side patient measurements. Method and Materials: The dosimeters were evaluated for: 1) Signal decay; 2) Field size dependence; 3) Energy dependence; 4) Angular dependence; and 5) their reusability using the Landauer, InLight MicroStar system. In‐Vivo dosimetry measurements were taken for 53 patients treated on a Varian 21EX using dosimeters and 67 patients using OneDose Mosfets. Results: The variation between dosimeters was evaluated and found to be ±1.6%. The dosimeters appeared to over‐respond in the first 10 minutes, however, after 10 minutes the chips were within 1 percent of the steady‐state reading. Unlike other detectors, the dosimeters showed no field size, energy, or angular dependence. In testing the reusability, it was found that the half life of the OSL material was 5.14 ± 0.01 hours. The agreement between the dosimeters and the calculated doses for the in‐vivo dosimetry patients was −1.9±5.9%. The OneDose agreement between mosfet and calculated dose was found to be −1.3±8.5%. Conclusion: dosimeters can be a convenient, inexpensive alternative to TLDs, MOSFETS, and Diodes. The agreement between calculated and measured doses for in‐vivo dosimetry QA is comparable to TLDs, MOSFETS, and Diodes. The dosimeters can be quickly read and analyzed after 10 minutes (to allow time for signal decay). The dosimeters do not appear to have an energy, field size, angular, or sensitivity dependence. In addition, under specific conditions, the detectors can be erased and re‐used.