pmp Progress in Medical Physics Progress in Medical Physics 2508-4445 2508-4453 Korean Society of Medical Physics 10.14316/pmp.2017.28.2.45 pmp-28-45 Original Article Assessment of Radiation Dose from Radioactive Wedge Filters during High-Energy X-Ray Therapy BackGeum-mun ParkSung Ho † KimTae-Hyung † Department of Radiation Oncology, Asan Medical Center, Seoul, Korea Department of Neurosurgery, Ulsan University Hospital, Ulsan, Korea Department of Radiological Science, Kangwon National University, Samcheok, Korea Corresponding author Sung Ho Park (michael@uuh.ulsan.kr) Tel: 82-52-250-7137 Fax: 82-52-250-7138 62017 1762017 282 4548 17032017 04062017 01072017 Copyright © 2017 Korean Society of Medical Physics 2017 This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/3.0/) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited. Abstract

This paper evaluated the amount of radiation generated by wedge filters during radiation therapy using a high-energy linear accelerator, and the dose to the worker during wedge replacement. After 10-MV photon beam was irradiated with wedge filter, the wedge was removed from the linear accelerator, and the dose rate and energy spectrum were measured. The initial measurement was approximately 1 uSv/h, and the radiation level was reduced to 0.3 uSv/h after 6 min. The effective half-life derived from the dose rate measurement was approximately 3.5 min, and the influence of AI-28 was about 53%. From the energy spectrum measurements, a peak of 1,799 keV was measured for AI-28, while the peak for Co-58 was not measured in the control room. The peaks for Au-106 and Cd-105 were found only measurement was done without wedge removement from the linear accelerator. The additional doses received by the radiation worker during wedge replacement were estimated to be 0.08−0.4 mSv per year.

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Measurement of dose rate using GM detector and activated wedge filter.

Measurement of energy spectrum using NaI scintillator detector.

Measured dose rate of activated wedge after 5-Gy irradiation at various field sizes.

Measured energy spectrum from activated wedge after 5-Gy irradiation.

Exposure dose to workers owing to removal of activate wedge after X-ray treatment.

Number of patients persons/day Number of wedge remove times/patient Exposure, uSv
20 1 83
  2 167
30 1 125
  2 250
40 1 167
  2 333
50 1 208
  2 417