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On the Use Factor Analysis and Adequacy Evaluation of CyberKnife Shielding Design Using Clinical Data
Prog. Med. Phys. 2018;29(4):115-122
Published online December 31, 2018
© 2018 Korean Society of Medical Physics.

Yu Ra Cho*, Haijo Jung, Dong Han Lee*

*Department of CyberKnife Center, Korea Institute of Radiological & Medical Sciences, Radiation Safety Office, Korea Institute of Radiological & Medical Sciences, Seoul, Korea
Correspondence to: Dong Han Lee ( 
Tel: 82-2-970-1812  Fax: 82-2-970-2406
Received October 26, 2018; Revised December 18, 2018; Accepted December 18, 2018.
This is an Open-Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License ( which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.
Although the current internationally recommended standard for the use factor (U) applied to CyberKnife is 0.05 (5%), the CyberKnife shielding standard is applied more stringently. This study, based on clinical data, was aimed at examining the appropriateness of existing shielding guidelines. Sixty patients treated with G4 CyberKnife were selected. The patients were divided into two groups, according to whether they underwent skull or spine tracking. Based on the results, the use factors for each wall ranged from 0.028 (2.8%) to 0.031 (3.1%) for the intracranial treatment and 0.020 (2.0%) to 0.022 (2.2%) for the body treatment. Excessive barrier thickness resulted in inefficient use of space and higher cost to the institutions. Furthermore, because the use factor is influenced by the position of the robot, the use factor determined based on the clinical data of this study would facilitate more reasonable treatment room design.
Keywords : Radiation protection, Radiation shielding design, G4 CyberKnife, Use factor

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