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UNIVERSITY OF BUCHAREST
FACULTY OF PHYSICS Guest
2026-06-11 23:58 |
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Conference: Bucharest University Faculty of Physics 2026 Meeting
Section: Biophysics; Medical Physics
Title:
Comprehensive Annual Quality Assurance and Water Phantom Dosimetry for the Varian TrueBeam Linear Accelerator
Authors:
Anca-Ștefania ORIAN (1) (2),
Tia POPESCU – BÂRHALĂ (1), (2)
*
Affiliation:
1) Neolife Medical Centre-Enayati, 8A Gheorghe Ionescu Sisești Street, Bucharest 013823
2) University of Bucharest, Faculty of Physics, 405 Atomistilor Street, P.O. Box MG-11, 077125 Magurele, Romania
E-mail
orian.anca@yahoo.com
Keywords:
Water phantom, Percent Depth Dose, TRS 398, annual quality assurance
Abstract:
Modern radiotherapy requires absolute dosimetric precision across all clinical techniques, ranging from conventional 3D treatments to complex intensity-modulated deliveries (IMRT/VMAT). To ensure patient safety and consistent treatment efficacy, the Varian TrueBeam platform—equipped with both standard flattened (WFF) and Flattening-Filter-Free (FFF) photon beams—demands rigorous annual quality assurance (QA). This presentation outlines a practical, step-by-step workflow for the annual dosimetric evaluation of a TrueBeam linear accelerator, focusing primarily on 3D water phantom measurements. The methodology covers the standard acquisition of Percent Depth Dose (PDD) curves, transverse dose profiles, and output factors across various energies and field sizes. Additionally, this presentation addresses the critical role of absolute reference dosimetry using the IAEA TRS-398 protocol for standard beam calibration. It also discusses proper detector selection for relative dosimetry. By systematically comparing these annual water tank measurements against the initial baseline commissioning data and the Treatment Planning System (TPS) model, medical physicists can detect any subtle beam variations. Finally, this work provides a clear, protocol-driven framework for executing annual water phantom dosimetry, ensuring the linac consistently meets the highest accuracy standards for all daily clinical treatments.
References:
IAEA (2000). Absorbed Dose Determination in External Beam Radiotherapy: An International Code of Practice for Dosimetry based on Standards of Absorbed Dose to Water (Technical Reports Series No. 398). Vienna: International Atomic Energy Agency.
IAEA & AAPM (2017). Dosimetry of Small Static Fields Used in External Beam Radiotherapy (Technical Reports Series No. 483). Vienna: International Atomic Energy Agency.
Das, I. J., et al. (2008). Accelerator beam data commissioning equipment and procedures: Report of the TG-106 of the Therapy Physics Committee of the AAPM. Medical Physics, 35(9), 4186-4215.
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