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Structural shielding design and evaluation for megavoltage x- and gamma-ray radiotherapy facilities : recommendations of the National Council on Radiation Protection and Measurements PDF

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Preview Structural shielding design and evaluation for megavoltage x- and gamma-ray radiotherapy facilities : recommendations of the National Council on Radiation Protection and Measurements

NCRP REPORT No. 151 Structural Shielding Design and Evaluation for Megavoltage X- and Gamma-Ray Radiotherapy Facilities Recommendations of the NATIONAL COUNCIL ON RADIATION PROTECTION AND MEASUREMENTS December 31, 2005 NationalCouncilonRadiationProtectionandMeasurements 7910WoodmontAvenue, Suite 400/Bethesda,MD20814-3095 ©NCRP 2006 - All rights reserved. Licensed to Stacey Maynard Downloaded 04/06/06 Single user license only, copying and networking prohibited. LEGAL NOTICE This Report was prepared by the National Council on Radiation Protection and Measurements (NCRP). The Council strives to provide accurate, complete and use- ful information in its documents. However, neither NCRP, the members of NCRP, other persons contributing to or assisting in the preparation of this Report, nor any person acting on the behalf of any of these parties: (a) makes any warranty or rep- resentation, express or implied, with respect to the accuracy, completeness or use- fulness of the information contained in this Report, or that the use of any information, method or process disclosed in this Report may not infringe on pri- vately owned rights; or (b) assumes any liability with respect to the use of, or for damages resulting from the use of any information, method or process disclosed in this Report, under the Civil Rights Act of 1964, Section 701 et seq. as amended 42 U.S.C. Section 2000e et seq. (Title VII) or any other statutory or common law theory governing liability. Disclaimer Any mention of commercial products within NCRP publications is for informa- tion only; it does not imply recommendation or endorsement by NCRP. Library of Congress Cataloging-in-Publication Data National Council on Radiation Protection and Measurements. Structural shielding design and evaluation for megavoltage x- and gamma-ray radiotherapy facilities:recommendations of the National Council on Radiation Protection and Measurements. p.cm.— (NCRP report;no. 151) “Issued December 2005.” Includes bibliographical references and index. ISBN-13: 978-0-929600-87-1 ISBN-10: 0-929600-87-8 1. Radiology, Medical—Equipment and supplies—Safety measures. 2. Shielding (Radiation) 3. Radiotherapy—Safety measures. 4. Gamma rays—Physiological effect. 5. Radiology, Medical—Safety measures. I. Title. II. Series. RA975.5.R3S77 2005 616.07’572--dc22 2006002275 Copyright © NationalCouncilonRadiation ProtectionandMeasurements2005 All rights reserved. This publication is protected by copyright. No part of this publica- tion may be reproduced in any form or by any means, including photocopying, or utilized by any information storage and retrieval system without written permission from the copyright owner, except for brief quotation in critical articles or reviews. [For detailed information on the availability of NCRP publications see page227.] ©NCRP 2006 - All rights reserved. Licensed to Stacey Maynard Downloaded 04/06/06 Single user license only, copying and networking prohibited. Preface This Report was developed under the auspices of Program Area Committee 2 of the National Council on Radiation Protection and Measurements (NCRP), the Committee that is concerned with operational radiation safety. The Report addresses the structural shielding design and evaluation for medical use of megavoltage xand gamma rays for radiotherapy and supersedes related mate- rial in NCRP Report No. 49, Structural Shielding Design and Eval- uation for Medical Use of X Rays and Gamma Rays of Energies Up to 10 MeV, which was issued in September 1976. The descriptive information in NCRP Report No. 49 unique to x-ray therapy instal- lations of less than 500 kV (Section 6.2) and brachytherapy (Sec- tion 7) is not included in this Report and that information in NCRP Report No.49 for those categories is still applicable. This Report was prepared through a joint effort of NCRP Scien- tific Committee 46-13 on Design of Facilities for Medical Radiation Therapy and the American Association of Physicists in Medicine (AAPM). NCRP gratefully acknowledges the support of AAPM for several of its members to serve on Scientific Committee 46-13 and the many opportunities that were made available for Scientific Committee 46-13 to meet at AAPM annual meetings. Serving on Scientific Committee 46-13 were: James A. Deye, Chairman National Cancer Institute Rockville, Maryland Vice-Chairmen James E. Rodgers Raymond K. Wu Maryland Regional Cancer Care OhioHealth Hospitals Silver Spring, Maryland Columbus, Ohio Members Peter J. Biggs Patton H. McGinley Massachusetts General Hospital Stone Mountain, Georgia Boston, Massachusetts Richard C. McCall Woodside, California iii ©NCRP 2006 - All rights reserved. Licensed to Stacey Maynard Downloaded 04/06/06 Single user license only, copying and networking prohibited. iv / PREFACE Liaisons Kenneth R. Kase Marc Edwards Lyncean Technologies, Inc. Radiation Oncology Associates of Palo Alto, California Kansas City Overland Park, Kansas Consultants Robert O. Gorson Jeffrey H. Kleck Columbia, South Carolina Attania Corporation San Jose, California Nisy E. Ipe San Carlos, California NCRP Secretariat Marvin Rosenstein, Consultant, 2001–2005 Eric E. Kearsley, Staff Scientist/Consultant, 1998–2001 James A. Spahn, Jr., Senior Staff Scientist, 1995–1998 Cindy L. O’Brien, Managing Editor David A. Schauer, Executive Director The contents are the sole responsibility of NCRP and do not nec- essarily represent the official views of the National Cancer Insti- tute or the National Institutes of Health. The Council wishes to express its appreciation to the Committee members, liaisons and consultants for the time and effort devoted to the preparation of this Report. Thomas S. Tenforde President ©NCRP 2006 - All rights reserved. Licensed to Stacey Maynard Downloaded 04/06/06 Single user license only, copying and networking prohibited. Contents Preface . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . iii 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 1.1 Purpose and Scope . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 1.2 Quantities and Units . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 1.3 Controlled and Uncontrolled Areas. . . . . . . . . . . . . . . . . 4 1.4 Shielding Design Goals and Effective Dose . . . . . . . . . . 5 1.4.1 Controlled Areas . . . . . . . . . . . . . . . . . . . . . . . . . 5 1.4.2 Uncontrolled Areas . . . . . . . . . . . . . . . . . . . . . . . 6 1.4.3 Shielding Design Assumptions. . . . . . . . . . . . . . 7 1.4.4 Measurements to Assess Compliance with the ShieldingDesign Goals. . . . . . . . . . . . . . . . . 8 1.5 Workload. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 1.6 Use Factor. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 1.7 Occupancy Factor. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10 1.8 Protective Barriers. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11 1.9 Basic Principles . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12 1.10 General Concepts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12 1.11 Types of Radiotherapy Installations. . . . . . . . . . . . . . . 14 1.12 Strategic Shielding Planning. . . . . . . . . . . . . . . . . . . . . 15 1.12.1 Planning and Budgeting. . . . . . . . . . . . . . . . . . 16 1.12.2 Programming. . . . . . . . . . . . . . . . . . . . . . . . . . . 16 1.12.3 Schematic (Preliminary) Design. . . . . . . . . . . . 17 1.12.4 Design Development . . . . . . . . . . . . . . . . . . . . . 17 1.12.5 Construction Document Preparation . . . . . . . . 17 1.12.6 Construction Inspection . . . . . . . . . . . . . . . . . . 18 1.13 Documentation Requirements. . . . . . . . . . . . . . . . . . . . 18 2. Calculational Methods . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20 2.1 Basic Concepts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20 2.2 Primary Barriers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22 2.2.1 Standard Approach . . . . . . . . . . . . . . . . . . . . . . 22 2.2.2 Barrier Widths. . . . . . . . . . . . . . . . . . . . . . . . . . 26 2.2.3 Laminated Barriers. . . . . . . . . . . . . . . . . . . . . . 27 2.3 Secondary Barriers. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32 v ©NCRP 2006 - All rights reserved. Licensed to Stacey Maynard Downloaded 04/06/06 Single user license only, copying and networking prohibited. vi / CONTENTS 2.4 Doors and Mazes. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .34 2.4.1 Low-Energy Accelerators. . . . . . . . . . . . . . . . . .34 2.4.2 High-Energy Accelerators. . . . . . . . . . . . . . . . .40 2.4.2.1 Photon Dose-Equivalent Calculation at the Maze Door . . . . . . . . . . . . . . . .40 2.4.2.2 Neutron Dose Equivalent at the Maze Door. . . . . . . . . . . . . . . . . . . . . .43 2.4.2.2.1 Kersey’s Method. . . . . . . .43 2.4.2.2.2 Modified Kersey’s Method . . . . . . . . . . . . . . .44 2.4.2.3 Total Dose Equivalent at the Maze Door. . . . . . . . . . . . . . . . . . . . . .45 2.4.3 Door Shielding . . . . . . . . . . . . . . . . . . . . . . . . . .46 2.4.4 Alternate Maze and Door Designs . . . . . . . . . .46 2.4.5 Direct-Shielded Door . . . . . . . . . . . . . . . . . . . . .47 2.4.5.1 Design Problems with Direct- Shielded Doors . . . . . . . . . . . . . . . . . .48 2.4.5.2 Neutron Capture Gamma Rays with Direct-Shielded Doors . . . . . . . . . . . .51 2.4.5.3 Alternative Room Design for Direct-Shielded Doors . . . . . . . . . . . .51 3. Workload, Use Factor, and Absorbed-Dose Rate Considerations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .52 3.1 Conventional Procedures . . . . . . . . . . . . . . . . . . . . . . . .53 3.1.1 Conventional Workloads . . . . . . . . . . . . . . . . . .53 3.1.2 Conventional Use Factors . . . . . . . . . . . . . . . . .54 3.2 Special Procedures . . . . . . . . . . . . . . . . . . . . . . . . . . . . .55 3.2.1 Total-Body Irradiation Considerations. . . . . . .55 3.2.2 Intensity Modulated Radiation Therapy Considerations . . . . . . . . . . . . . . . . . . . . . . . . . .57 3.2.3 Quality Assurance . . . . . . . . . . . . . . . . . . . . . . .58 3.2.4 Dedicated Purpose Machines . . . . . . . . . . . . . .58 3.2.5 Effect of Special Procedures on Shielding Calculations . . . . . . . . . . . . . . . . . . . . . . . . . . . .58 3.2.5.1 Primary-Barrier Calculations . . . . . .59 3.2.5.2 Patient- or Phantom-Scattered- Radiation Calculations. . . . . . . . . . . .59 3.2.5.3 Leakage-Radiation Shielding Considerations . . . . . . . . . . . . . . . . . .60 3.2.5.4 Maze Entrance Calculations . . . . . . .60 ©NCRP 2006 - All rights reserved. Licensed to Stacey Maynard Downloaded 04/06/06 Single user license only, copying and networking prohibited. CONTENTS / vii 3.3 Time Averaged Dose-Equivalent Rates. . . . . . . . . . . . . 61 3.3.1 Weekly Time Averaged Dose-Equivalent Rate . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 62 3.3.2 In-Any-One-Hour Time Averaged Dose-Equivalent Rate . . . . . . . . . . . . . . . . . . . . 63 4. Structural Details. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 65 4.1 General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 65 4.1.1 Location . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 65 4.1.2 Provision for Future Needs. . . . . . . . . . . . . . . . 66 4.1.3 Size of Treatment Room . . . . . . . . . . . . . . . . . . 66 4.1.4 Interlocks and Warning Lights. . . . . . . . . . . . . 67 4.1.5 Control Console . . . . . . . . . . . . . . . . . . . . . . . . . 67 4.2 Barriers. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 67 4.3 Shielding Materials . . . . . . . . . . . . . . . . . . . . . . . . . . . . 69 4.3.1 Ordinary Concrete. . . . . . . . . . . . . . . . . . . . . . . 69 4.3.2 Heavy Concrete . . . . . . . . . . . . . . . . . . . . . . . . . 69 4.3.3 Lead . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 71 4.3.4 Steel . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 71 4.3.5 Polyethylene and Paraffin. . . . . . . . . . . . . . . . . 71 4.3.6 Earth . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 72 4.3.7 Wood. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 72 4.3.8 Rebar and Form Ties. . . . . . . . . . . . . . . . . . . . . 72 4.3.8.1 Rebar. . . . . . . . . . . . . . . . . . . . . . . . . . 72 4.3.8.2 Form Ties . . . . . . . . . . . . . . . . . . . . . . 73 4.4 Joints, Concrete Slab Junctions . . . . . . . . . . . . . . . . . . 74 4.5 Access to Radiation Vault . . . . . . . . . . . . . . . . . . . . . . . 76 4.6 Ducts. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 77 4.6.1 Heating, Ventilation and Air-Conditioning, andHigh-Voltage Ducts . . . . . . . . . . . . . . . . . . 78 4.6.1.1 Rooms with Mazes. . . . . . . . . . . . . . . 78 4.6.1.2 Rooms without Mazes . . . . . . . . . . . . 79 4.6.1.3 Ducts Passing Through the Ceiling . 80 4.6.2 Machine Cables . . . . . . . . . . . . . . . . . . . . . . . . . 81 4.6.3 Water and Electrical Conduits. . . . . . . . . . . . . 81 4.7 Lead-Only Rooms. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 81 4.8 Beamstoppers. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 82 5. Special Considerations. . . . . . . . . . . . . . . . . . . . . . . . . . . . 84 5.1 Skyshine Radiations. . . . . . . . . . . . . . . . . . . . . . . . . . . . 84 5.2 Side-Scattered Photon Radiation. . . . . . . . . . . . . . . . . . 88 ©NCRP 2006 - All rights reserved. Licensed to Stacey Maynard Downloaded 04/06/06 Single user license only, copying and networking prohibited. viii / CONTENTS 5.3 Groundshine Radiation. . . . . . . . . . . . . . . . . . . . . . . . . .89 5.4 Activation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .90 5.5 Ozone Production . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .91 5.6 Tomotherapy. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .93 5.7 Robotic Arm. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .94 5.8 Dedicated Intraoperative-Radiotherapy Units . . . . . . .95 5.9 Cobalt-60 Units. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .95 6. Shielding Evaluation (Surveys) . . . . . . . . . . . . . . . . . . . .97 6.1 Construction Inspection . . . . . . . . . . . . . . . . . . . . . . . . .97 6.2 Interlocks, Restrictive Devices, and Radiation WarningLights and Signs . . . . . . . . . . . . . . . . . . . . . . .98 6.3 Radiation Survey . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .99 6.4 Shielding Evaluation Report . . . . . . . . . . . . . . . . . . . .101 7. Examples . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .105 7.1 Conventional Treatment Unit with Maze. . . . . . . . . .105 7.1.1 Primary Barrier at Location C . . . . . . . . . . . .105 7.1.2 Time Averaged Dose-Equivalent Rate Considerations atLocation C . . . . . . . . . . . . .107 7.1.3 Patient-Scattered Radiation ConsiderationsatLocation C . . . . . . . . . . . . .109 7.1.4 Leakage-Radiation Considerations at Location C. . . . . . . . . . . . . . . . . . . . . . . . . . . . .111 7.1.5 Leakage- and Patient-Scattered-Radiation Considerations for Location A. . . . . . . . . . . . .113 7.1.6 Time Averaged Dose-Equivalent Rate (in-any-one-hour) Considerations for Location A. . . . . . . . . . . . . . . . . . . . . . . . . . . . .117 7.1.7 Primary Barrier at Location D in the TreatmentControl Area . . . . . . . . . . . . . . . . .120 7.1.8 Secondary Barrier at Location B. . . . . . . . . . .121 7.1.9 Secondary Barrier at Location E. . . . . . . . . . .124 7.1.10 Leakage and Scattered Radiation at the MazeDoor. . . . . . . . . . . . . . . . . . . . . . . . . . . . .128 7.1.10.1 Wall-Scattered Radiation Component, H . . . . . . . . . . . . . . . . .129 S 7.1.10.2 Head-Leakage Wall-Scattered Radiation Component, H . . . . . . . .129 LS 7.1.10.3 Patient-Scattered Radiation Component, H . . . . . . . . . . . . . . . . .130 ps ©NCRP 2006 - All rights reserved. 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CONTENTS / ix 7.1.10.4 Head-Leakage Radiation Through Maze Wall, H . . . . . . . . . . . . . . . . . 131 LT 7.1.10.5 Total Dose Equivalent Due to Scattered and Leakage Radiations, H . . . . . . . . . . . . . . . . 132 Tot 7.1.10.6 IMRT Modifications. . . . . . . . . . . . . 132 7.1.10.6.1 Head-Leakage Wall-Scattered-Radiation Component, H . . . . . . . 132 LS 7.1.10.6.2 Head-Leakage Radiation Transmitted Through MazeWall, H . . . . . . . . 132 LT 7.1.11 Neutron Capture Gamma-Ray Dose Equivalentat theMaze Door . . . . . . . . . . . . . 133 7.1.12 Neutron Dose Equivalent at the Maze Door . 135 7.1.13 Shielding Barrier for the Maze Door . . . . . . . 136 7.1.14 Primary Barrier for Roof Location G . . . . . . . 138 7.1.15 Secondary Barrier for Roof Location H . . . . . 142 7.1.16 Time Averaged Dose-Equivalent Rate for theSecondaryBarrier at Location H with Intensity ModulatedRadiation Therapy . . . . 146 7.1.17 Maze Barrier Thickness . . . . . . . . . . . . . . . . . 146 7.2 Robotic Arm Stereotactic-Radiosurgery Room . . . . . . 148 7.2.1 Time Averaged Dose-Equivalent Rate Considerations forLocation A. . . . . . . . . . . . . 151 7.2.2 Barrier for Location B. . . . . . . . . . . . . . . . . . . 153 7.2.3 Shielding for Location C . . . . . . . . . . . . . . . . . 154 7.2.4 Determination of the Maze Barrier Thickness(Location D) . . . . . . . . . . . . . . . . . . 155 7.2.5 Shielding at Location E (Roof) . . . . . . . . . . . . 156 Appendix A. Supporting Data (Figures) . . . . . . . . . . . . . . . 158 Appendix B. Supporting Data (Tables) . . . . . . . . . . . . . . . . 160 Appendix C. Neutron Monitoring for Radiotherapy Facilities. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 175 C.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 175 C.2 Neutron Monitoring Techniques . . . . . . . . . . . . . . . . . 178 ©NCRP 2006 - All rights reserved. Licensed to Stacey Maynard Downloaded 04/06/06 Single user license only, copying and networking prohibited. x / CONTENTS C.2.1 Active Monitoring. . . . . . . . . . . . . . . . . . . . . . .178 C.2.1.1 Rem-Meters. . . . . . . . . . . . . . . . . . . .178 C.2.1.2 Commercial Instruments. . . . . . . . .181 C.2.1.3 Fluence Meters. . . . . . . . . . . . . . . . .184 C.2.1.4 Neutron Spectrometers . . . . . . . . . .185 C.2.2 Passive Monitoring . . . . . . . . . . . . . . . . . . . . .186 C.2.2.1 Activation Detectors. . . . . . . . . . . . .186 C.2.2.2 Solid-State Nuclear Track Detectors. . . . . . . . . . . . . . . . . . . . . .189 C.2.2.3 Bubble Detectors . . . . . . . . . . . . . . .191 C.2.2.4 Comparison of Various Passive Monitors . . . . . . . . . . . . . . . . . . . . . .192 C.3 Conclusions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .195 Glossary. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .198 Symbols and Acronyms . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .205 References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .210 The NCRP. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .219 NCRP Publications. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .227 Index . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .237 ©NCRP 2006 - All rights reserved. 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