ESTRO 2024 - Abstract Book

S3195

Physics - Detectors, dose measurement and phantoms

ESTRO 2024

Table 1. k B,Q correction factors for both OSL dosimeters and all three cardinal orientations considered in this study. Values are also given after rotating the detectors by +90 o and -90 o around their central y-axis parallel to the magnetic field (positive rotational direction is depicted in Figure 1). Reported uncertainties correspond to the combined total uncertainties at the 68% confidence level.

Conclusion:

k B,Q values for two OSL detectors and all cardinal orientations with respect to the magnetic field were determined, contributing to data availability for dosimetry protocols in 1.5T MR-Linacs. For QA checks involving several gantry angles, results of this study suggest that OSL detectors should be placed in the axial orientation. Acknowledgements: Elekta Ltd is acknowledged for providing the Unity phase space source files used in this study. Landauer Inc. and RadPro International GmbH are acknowledged for providing detailed schematics of the corresponding OSL dosimeters. This work was supported by computational time granted from the Greek Research & Technology Network (GRNET) in the National HPC facility—ARIS— under project ID pr015013.

Keywords: OSL, dosimetry, Unity, MR-linac

References:

[1] Kry SF, Alvarez P, Cygler JE, DeWerd LA, Howell RM, Meeks S, et al. AAPM TG 191: Clinical use of luminescent dosimeters: TLDs and OSLDs. Med Phys 2020;47:e19–51.

[2] De Pooter J, Billas I, De Prez L, Duane S, Kapsch RP, Karger CP, et al. Reference dosimetry in MRI-linacs: evaluation of available protocols and data to establish a Code of Practice. Phys Med Biol 2021;66.

[3] Van Asselen B, Woodings SJ, Hackett SL, Van Soest TL, Kok JGM, Raaymakers BW, et al. A formalism for reference dosimetry in photon beams in the presence of a magnetic field. Phys Med Biol 2018;63.

[4] Ito S, Araki F, Hoshida K, Ohno T. Impact of transverse magnetic fields on dose response of a nanoDot OSLD in megavoltage photon beams. Physica Medica 2020;70:153–60.

[5] Margaroni V, Pappas EP, Episkopakis A, Pantelis E, Papagiannis P, Marinos N, et al. Dosimetry in 1.5 T MR-Linacs: Monte Carlo determination of magnetic field correction factors and investigation of the air gap effect. Med Phys 2023;50:1132–48.