Program Information
Characterization and Validation of Optically Stimulated Luminescent Dosimeters for In-Vivo Dosimetry of HDR Gynecological Brachytherapy Treatments
J Hanna1*, R Yaparpalvi1 , H Kuo1,2 , K Mehta1,2 , W Tome1,2 ,(1) Montefiore Medical Center, Bronx, NY, (2) Albert Einstein College of Medicine, Bronx, NY,
Presentations
SU-I-GPD-T-15 (Sunday, July 30, 2017) 3:00 PM - 6:00 PM Room: Exhibit Hall
Purpose: To demonstrate the feasibility of clinical implementation of OSLDs for HDR in-vivo dosimetry for gynecological patients.
Methods: The OSLD sensitivity to Ir-192 gammas was measured and compared to the sensitivity to 6 MV x-rays, and a sensitivity factor was established. These measurements were taken at a depth of 1.5-cm under full scatter conditions. Phantom measurements were made where OSLDs were secured 0.5-cm from the surface of a 3-cm diameter cylinder along the length vaginal cuff and at the tip of the applicator. A treatment plan prescribed for 500 cGy at 0.5-cm from the cylinder surface was delivered to the phantom. The same plan was then redelivered to 2.5-cm and 3.5-cm vaginal cylinders. In-vivo measurements were also made for two cervical cancer patients. The measurements were made at the surface of the vaginal cylinder along the length of the vaginal cuff and compared to calculated doses.
Results: The OSLD response to Ir-192 gamma rays was found, on average, to be 5% higher than to 6 MV x-rays, therefore a 1.05 sensitivity factor was used for this study. Phantom measurements were found to be within ±4% of the calculated doses under full scatter conditions. The measurements made with the incorrect cylinder sizes showed gross error in dose, as expected. In-vivo measurements taken from cervical cancer patients were found to be within ±3% of the calculated dose.
Conclusion: OSLDs are small in size and can be unobtrusively placed along the surface of a vaginal cylinder. Since HDR gynecological treatments are not planned per fraction, the use of the wrong cylinder is possible. Using OSLDs for in-vivo measurements is feasible and has the potential to detect and prevent gross errors. Future work will be performed to collect additional in-vivo measurements with the goal to implement OSLD measurements for QA purposes for HDR treatments.
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