Please use this identifier to cite or link to this item: http://hdl.handle.net/10397/15695
Title: Evaluation of optimum room entry times for radiation therapists after high energy whole pelvic photon treatments
Authors: Ho, L
White, P 
Chan, E
Chan, K
Ng, J
Tam, T
Keywords: High energy photons
Radiographers
Room entry times
Issue Date: 2012
Publisher: Japan Society for Occupational Health
Source: Journal of occupational health, 2012, v. 54, no. 2, p. 131-140 How to cite?
Journal: Journal of occupational health 
Abstract: Objectives: Linear accelerators operating at or above 10 MV produce neutrons by photonuclear reactions and induce activation in machine components, which are a source of potential exposure for radiation therapists. This study estimated gamma dose contributions to radiation therapists during high energy, whole pelvic, photon beam treatments and determined the optimum room entry times, in terms of safety of radiation therapists. Methods: Two types of technique (anteriorposterior opposing and 3-field technique) were studied. An Elekta Precise treatment system, operating up to 18 MV, was investigated. Measurements with an area monitoring device (a Mini 900R radiation monitor) were performed, to calculate gamma dose rates around the radiotherapy facility. Measurements inside the treatment room were performed when the linear accelerator was in use. The doses received by radiation therapists were estimated, and optimum room entry times were determined. Results: The highest gamma dose rates were approximately 7 μSv/h inside the treatment room, while the doses in the control room were close to background (~0 μSv/h) for all techniques. The highest personal dose received by radiation therapists was estimated at 5 mSv/yr. To optimize protection, radiation therapists should wait for up to11 min after beam-off prior to room entry. Conclusions: The potential risks to radiation therapists with standard safety procedures were well below internationally recommended values, but risks could be further decreased by delaying room entry times. Dependent on the technique used, optimum entry times ranged between 7 to 11 min. A balance between moderate treatment times versus reduction in measured equivalent doses should be considered.
URI: http://hdl.handle.net/10397/15695
ISSN: 1341-9145
EISSN: 1348-9585
DOI: 10.1539/joh.11-0161-FS
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