An Analytical Method to Calculate Phantom Scatter Factor for Photon Beam Accelerators

Mohammad Javad Tahmasebi Birgani; Nahid Chegeni; Mohammad Ali Behrooz; Marziyeh Bagheri; Amir Danyaei; Azin Shamsi

doi:10.19082/3523

An Analytical Method to Calculate Phantom Scatter Factor for Photon Beam Accelerators

Electron Physician. 2017 Jan 25;9(1):3523-3528. doi: 10.19082/3523. eCollection 2017 Jan.

Authors

Mohammad Javad Tahmasebi Birgani¹, Nahid Chegeni², Mohammad Ali Behrooz³, Marziyeh Bagheri⁴, Amir Danyaei², Azin Shamsi⁵

Affiliations

¹ Ph.D. of Medical Physics, Professor, Department of Medical Physics and Radiation Therapy and Medical Physics Department, Golestan Hospital, Jundishapur University of Medical Sciences, Faculty of Medicine, Ahvaz Jundishapur University of Medical Sciences: Ahvaz, Iran.
² Ph.D. of Medical Physics, Assistant Professor, Department of Medical Physics, Faculty of Medicine, Ahvaz Jundishapur University of Medical Sciences: Ahvaz, Iran.
³ Ph.D. of Bio Physics, Professor, Department of Medical Physics, Faculty of Medicine, Ahvaz Jundishapur University of Medical Sciences: Ahvaz, Iran.
⁴ M.Sc. of Medical Physics, Department of Medical Physics, Faculty of Medicine, Ahvaz Jundishapur University of Medical Sciences: Ahvaz, Iran.
⁵ M.Sc. of Medical Physics, Radiation Therapy and Medical Physics Department, Golestan Hospital, Jundishapur University of Medical Sciences.

PMID: 28243402
PMCID: PMC5308490
DOI: 10.19082/3523

Abstract

Introduction: One of the important input factors in the commissioning of the radiotherapy treatment planning systems is the phantom scatter factor (Sp) which requires the same collimator opening for all radiation fields. In this study, we have proposed an analytical method to overcome this issue.

Methods: The measurements were performed using Siemens Primus Plus with photon energy 6 MV for field sizes from 5×5cm² to 40×40cm². Phantom scatter factor was measured through the division of total scatter output factors (Scp), and collimator scatter factor (Sc).

Results: The mean percent difference between the measured and calculated Sp was 1.00% and -3.11% for 5×5, 40×40 cm² field size respectively.

Conclusion: This method is applicable especially for small fields used in IMRT which, measuring collimator scatter factor is not reliable due to the lateral electron disequilibrium.

Keywords: Phantom scatter factor; Radiotherapy; Total scatter factor.