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Cho, Jung, Min, Bae, Moon, Kim, Cho, and Lee: Survey of Radiation Shielding Design Goals and Workload Based on Radiation Safety Report: Tomotherapy Vault
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Progress in Medical Physics 2018;29(1):42-46.

Published online: 20 March 2018

DOI: https://doi.org/10.14316/pmp.2018.29.1.42

Survey of Radiation Shielding Design Goals and Workload Based on Radiation Safety Report: Tomotherapy Vault

Kwang Hwan Cho∗, Jae Hong Jung∗, Chul Kee Min∗, Sun Hyun Bae∗, Seong Kwon Moon∗, Eun Seog Kim∗, Sam Ju Cho†, Rena Lee†

∗Department of Radiation Oncology, Soonchunhyang University, College of Medicine, Cheonan, Korea

†Department of Biomedical Engineering, Ewha Womans University School of Medicine, Seoul, Korea

Corresponding author Jae Hong Jung (jjh-3450@hanmail.net) Tel: 82-32-621-5783 Fax: 82-32-621-5885

Received 14 March 2018       Revised 28 March 2018       Accepted 30 March 2018

Copyright © 2018 Korean Society of Medical Physics

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

The purpose of this study was to perform a survey of the radiation shielding design goals (P) and workload (W) based on the radiation safety reports concerned with structural shielding design for the IMRT treatment technique in Tomotherapy vaults. The values of the P and W factors as well as of a verified concrete thickness of the ceiling, bottom, sidewalls (sidewall-1 and sidewall-2), and door have been obtained from radiation safety reports for a total of 16 out of 20 vaults. The recommended and most widely used report for P values was the NCRP No. 151 report, which stated that the P factor in controlled and uncontrolled areas was 0.1 and 0.02 mSv/week, respectively. The range of the W factor was 600∼14,720 Gy/week. The absorbed dose delivered per patient was 2∼3 Gy. The maximum number of patients treated per day was 10∼70. The quality assurance (QA) dose was 100∼1,000 Gy/week. Fifteen values of the IMRT factor (F) were mostly used but a maximum of 20 values was also used. The concrete thickness for primary structures including the ceiling, bottom, sidewalls, and door was sufficient for radiation shielding. The P and W factors affect the calculation of the structural shielding design, and several parameters, such as the absorbed dose, patients, QA dose, days and F factor can be varied according to the type of shielding structure. To ensure the safety of the radiation shielding, it is necessary to use the NCRP No. 151 report for the standard recommendation values.

Keywords: Radiation Shielding, Workload, NCRP-151, Tomotherapy

References

1. NCRP Report No. 151. 2005. Structural Shielding Design and Evaluation for Megavoltage X-and Gamma-Ray Radiotherapy Facilities. Medical Physics.
2. Murai T, Shibamoto Y, Manabe Y, et al. Intensity-modulated radiation therapy using static ports of tomotherapy (TomoDirect): Comparison with the TomoHelical mode. Radiat Oncol. 2013; 8:1–7.
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5. Robinson D, Scrimger JW, Field GC, Fallone BG. Shielding considerations for tometherapy. Med Phys. 2000; 27:2380–2384.
6. Zacarias A, Balog J, Mills M. Radiation shielding design of a new tomotherapy facility. Health Phys. 2006; 91:289–295.
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7. NCRP Report No. 49. 1976. Structural Shielding Design and Evaluation for Medical Use of X Rays and Gamma Rays of Energies up to 10 MeV. National Council on Radiation Protection and Measurements (NCRP).
8. NCRP Report No. 51. 1977. Radiation Protection Guidelines for 0.1 –100 MeV Particle Accelerator Facilities: National Council on Radiation Protection and Measurements (NCRP).
9. Martin MC. 2007. Tomotherapy Vault Design. AAPM 2007 Summer School.

Table 1.
Recommendations of the radiation shielding design goals with reference.
No. Radiation shielding design goals (mSv/week) Recommendation
Controlled areas Uncontrolled areas
1 0.4 0.02 ME
2 0.4 0.02 ME
3 0.4 0.1 NCRP No. 49 and 51
4 0.4 0.02 ME
5 0.4 0.1 NCRP No. 49 and 51
6 0.4 0.02 –
7 0.4 0.1 ME
8 0.4 0.02 ME
9 0.3 0.1 –
10 0.4 0.1 NCRP No. 49 and 51
11 0.1 0.02 NCRP No. 151
12 0.1 0.02 NCRP No. 151
13 0.1 0.02 NCRP No. 151
14 0.1 0.02 NCRP No. 151
15 0.4 0.02 ME
16 0.1 0.02 NCRP No. 151

ME: Ministry of Education, NCRP: National Council on Radiation Protection and Measurements.

Table 2.
Workload values with determined parameters for sixteen Tomotherapy vaults.
No. Absorbed dose (Gy) Patient (No.) QA dose (Gy/week) Days Workload (Gy/week)
1 2.5 70 720 5 14,720
2 2.2 50 0 5 880
3 3 60 100 5 1,000
4 2 20 500 5 3,500
5 2 10 200 5 600
6 2.5 20 1,000 5 6,000
7 3 20 500 5 5,000
8 2 30 500 5 3,500
9 2.5 20 250 5 10,000
10 3 20 500 5 5,000
11 3 40 500 5 9,500
12 3 40 500 5 9,500
13 3 40 500 5 9,500
14 3 40 500 5 9,500
15 2.5 20 250 5 10,000
16 3 20 200 5 4,700

Absorbed dose: Absorbed dose delivered per patient (or field), Patients: Maximum number of patients treated per day, Days: Operation days per week (day/week).

Table 3.
Radiation shielding design goals according to recommendation reports in the controlled and uncontrolled areas.
Recommendation Controlled areas (mSv/week) Uncontrolled areas (mSv/week)
ICRP 60 0.4 0.02
AEL 1.0 (20 mSv/year) 0.1 (1 mSv/week)
ME 0.4 0.02
NCRP 49 (<10 MV) 0.4 0.1
NCRP 51 (>10 MV) 0.4 0.1
NCRP 151 0.1 0.02

ICRP: International Committee for Radioactivity Prevention, AEL: Atomic Energy Law (Thirteenth, 2014–34), ME: Ministry of Education, NCRP: National Council on Radiation Protection and Measurements.

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