Room: AAPM ePoster Library
Purpose: The goal of this study is to develop an approach allowing for calibration of multi-point scintillation detector (mPSD) using only the photon beam from a linear accelerator such that it doesn’t depend on the availability of other irradiation modalities (e.g. orthovoltage irradiators). This study also aims at determining an experimental method to validate the spatial position of the different scintillators within the mPSD.
Methods: A 3-point mPSD was built with scintillators of 1 mm spaced by 10 mm from each other. Spectra were acquired using the new commercially available HYPERSCINT scintillation dosimetry research platform. An automated translation module was developed to allow scanning of the detector while running the linear accelerator. A lead collimator of 5-mm diameter was used to better confine the radiation to the scintillating elements. Once the position of the scintillators elements were found, they were irradiated with and without the collimator (i.e. using only the linac jaws) for comparison. Emission spectra of each scintillator were also acquired using a kilovoltage irradiator photon beam and served as gold standard.
Results: Calculated relative positions of the scintillators were 0.5 mm and 0.7 mm from the expected ones. The lead collimator significantly improved the capability of obtaining scintillation spectra similar to the expected ones (RMS error improving by a factor of at least 2). The remaining difference was shown to be due to the presence of Cherenkov light in the signal and further techniques are being investigated.
Conclusion: The proposed approach helped towards the goal of calibrating the mPSD using only a linear accelerator. Furthermore, the method is efficient: it automates a long and tedious process, avoids risks of mis-positioning the mPSD, and allows for extraction of high quality spectra, which is essential for accurate dose measurements with mPSDs.