UNIVERSITY OF BUCHAREST
FACULTY OF PHYSICS

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2024-11-24 11:26
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Conference: Bucharest University Faculty of Physics 2021 Meeting


Section: Biophysics; Medical Physics


Title:
Assurance of the optimal conditions in radiotherapy treatment


Authors:
Melania-Beatrice ISTRATI


Affiliation:
University of Bucharest, Faculty of Physics, 405 Atomistilor Str., P.O.Box MG-11, 077125 Bucharest-Măgurele, Romania


E-mail
melaniabeatrice99@gmail.com


Keywords:
radiotherapy, absorbed dose, water phantom


Abstract:
A certain level of accuracy in the dose supplied to the patient is essential to get a favorable clinical outcome in radiation treatment. Because the absorbed dose determination is complex and dependent on a variety of external and internal factors, the dosimetry communities:International Atomic Energy Agency (IAEA), the Bureau International des Poids et Mesures (BIPM), the International Commission of Radiation Units and Measurements (ICRU)have introduced protocols for physicists. This work focuses on calculating the uncertainty of the dose absorbed in water during a routine calibration for clinical beams of radiations in the range of energies used in external-beam radiotherapy. We performed the calibration of the electrometer, considering different components of uncertainty (temperature, pressure, polarity effect and recombination effect). The beam quality correction factor was theoretically determined using Monte Carlo simulations. Throughout the entire work, we were able to determine dose at the depth of dose maximum from measurements made at the reference depth for photon beams. The calibrations were carried out in a water equivalent phantom utilizing water proof ionization chambers for a 10 cm × 10 cm field size and at SSD = 100 cm (SSD - the distance between the source and the phantom surface). The results match the calibration factors for a cylindrical ionization chamber in Clinac iX medical linear accelerator from the Institute of Oncology Bucharest (IOB), Romania. The calibration procedure follows the IAEA TRS-398 reference Code of Practice.


References:

Absorbed Dose Determination in External Beam Radiotherapy: An International Code of Practice for Dosimetry Based on Standards of Absorbed Dose to Water (TRS 398)

Podgorsak E. (2005). Radiation Oncology Physics: A Handbook for Teachers and Students. IAEA.