2022-07-01 16:54


Conference: Bucharest University Faculty of Physics 2019 Meeting

Section: Biophysics; Medical Physics

Quality assurance in modern radiation therapy

Elena Loredana MILITARU (1,2), Claudia CHILOM (1), Mihai Daniel SUDITU (2)

1. Faculty of Physics, University of Bucharest

2. Medical Center, “Sfantul Nicolae”, Pitesti, Romania


Modulated intensity radiation therapy, quality assurance

Radiation therapy has advanced considerably during the last decades along with the development of complex equipment such as the modern medical linear accelerator (LINAC) and computerized tomograph. New radiation therapy techniques, including modulated intensity radiation therapy (IMRT), volumetric modulated arc therapy (VMAT) and image guided radiation therapy (IGRT), that are now available and allow to better shape the high dose radiation to the target volumes while the dose to the surrounding healthy tissues is minimized. Besides the advantages due to their complexity, the modern radiation techniques have also introduced new challenges especially for the medical physicists, whose role is to ensure the accurate delivery of the radiation dose distribution by having a very well-established quality assurance (QA) program. The aim of this study was to evaluate the variation of different parameters, that can affect the delivered dose, for a twelve months period. For Somatom Siemens computerized tomograph, the most important parameter analyzed was the correspondence between Hounsfield Units and relative electron density. Regarding the Elekta Synergy Linac (LINAC), the stability of a series of parameters including machine output, output linearity with dose rate, percentage depth dose and dose profiles was analyzed in accordance with different international protocols like IAEA TRS 398 Code of Practice. The last part of the study was conducted to review patient specific IMRT QA, delivered at our institution using the LINAC and Octavius 4D dosimetry system. All the investigated parameters showed good stability, with good agreement between the baseline values and the measured values. Also, for patient specific QA, gamma analysis with 3 mm distance to agreement and 3 % dose difference criteria was respected for more than 95 % of all evaluated points for all the cases that we analyzed.