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Photon and photon–neutron experimental dosimetry in Grid therapy with 18 MV photon beams

Published online by Cambridge University Press:  15 September 2020

Sareh Tajiki ,
Somayeh Gholami Open the ORCID record for Somayeh Gholami [Opens in a new window] ,
Mahbod Esfahani ,
Ali Rastjoo ,
Amir Hakimi ,
Amir K. Beheshti  and
Ali Meigooni
Sareh Tajiki
Affiliation:
Radiation Oncology Department, Cancer Institute, Tehran University of Medical Sciences, Tehran, Iran
Somayeh Gholami*
Affiliation:
Radiation Oncology Department, Cancer Institute, Tehran University of Medical Sciences, Tehran, Iran
Mahbod Esfahani
Affiliation:
Radiation Oncology Department, Cancer Institute, Tehran University of Medical Sciences, Tehran, Iran
Ali Rastjoo
Affiliation:
Radiation Oncology Department, Cancer Institute, Tehran University of Medical Sciences, Tehran, Iran
Amir Hakimi
Affiliation:
Health Physics and Dosimetry Research Laboratory, Department of Energy Engineering and Physics, Amirkabir University of Technology, Tehran, Iran
Amir K. Beheshti
Affiliation:
Department of Nuclear Engineering, University of Isfahan, Isfahan, Iran
Ali Meigooni
Affiliation:
Comprehensive Cancer Centers of Nevada, Las Vegas, NV, USA
*
Author for correspondence: Somayeh Gholami, Tehran University of Medical Sciences, Keshavarz St., Tehran, Tehran, Iran. E-mail: s-gholami@sina.tums.ac.ir
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Abstract

Propose:

Spatially fractionated Grid radiation therapy (SFGRT) in an effective technique for bulky and radio-sensitive tumours. SFGRT using a constructed block has been used to evaluate the photon and photo-neutron (PN) dose measurement in 18-MV photon beam energy.

Methods and materials:

A mounted Grid block on to a Varian Clinac 2100c linear accelerator was used to perform photon dosimetry. The percentage depth dose, in-plane and cross-plane beam profile and output factor was measured by ionization chamber in water. The PN contamination was measured after photon dosimetry using the combination of thermoluminescence dosimetry types 600 and 700, and Polycarbonate Film dosimeters on the surface and in the maximum depth dose (dmax) of solid water™ slabs.

Results:

The valley-to-peak ration for 6 and 18 MV photon beams obtained from the beam profiles was ~35 and 72%, respectively. Fast and thermal PN equivalent dose decreased in the Grid field compared to an open field (without Grid).

Conclusion:

The Grid therapy dosimetry compared to the conventional radiotherapy (without the grid) the production of fast and thermal neutrons were reduced. Using of a Grid block in high-energy photon beams for a long period of the treatment continuously might be a new source of contamination due to the interaction of photon beam resulting the activation of the Grid block

Keywords

grid therapyneutron contaminationPolycarbonate FilmSpatially fractionated radiation therapyTLD
Type
Original Article
Information
Journal of Radiotherapy in Practice , Volume 20 , Issue 4 , December 2021 , pp. 466 - 472
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Copyright
© The Author(s), 2020. Published by Cambridge University Press

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