1、 American National Standard ANSI/HPS N13.44-2014 Thyroid Phantom Used in Occupational Monitoring Approved 28 August 2014 American National Standards Institute, Inc. Published by Health Physics Society 1313 Dolley Madison Blvd. Suite 402 McLean, VA 22101 Copyright 2014 by the Health Physics Society.
2、All rights reserved. No part of this publication may be reproduced in any form, in an electronic retrieval system or otherwise, without prior written permission of the publisher. Printed in the United States of America ANSI/HPS N13.44-2014 The Health Physics Society Standards Committee Working Group
3、 responsible for this standard wishes to acknowledge previous members of this working group without whose efforts this standard would not have been achieved. The current working group had the following members: Michael W. Mallett, Chair Los Alamos National Laboratory Wesley E. Bolch University of Fl
4、orida Philip C. Fulmer Francis Marion University Tracy M. Jue California Department of Public Health David E. McCurdy Technical Consultant Mike Pillay Medical Center The Hague X. George Xu Rensselaer Polytechnic Institute ii This standard was consensus balloted and approved by Accredited Standards C
5、ommittee (ASC) N13 on 26 June 2014. At the time of balloting, the Committee had the following membership: Chairperson Michelle L. Johnson American Association of Physicians in Medicine Robert A. Phillips (AAPM) Lynne Fairobent (alternate) American College of Occupational and Environmental Medicine B
6、ryce Breitenstein American Industrial Hygiene Association (AIHA) Ray Johnson American Iron and Steel Institute Anthony La Mastra American Mining Congress Scott C. Munson American Nuclear Insurers Marcia Anderson Bob Oliveira (alternate) American Nuclear Society (ANS) Ali Simpkins Conference of Radia
7、tion Control Program Directors (CRCPD) Earl Fordham Council on Ionizing Radiation Measurements and Standards (CIRMS) Chris Soares Council on Radionuclides and Radiopharmaceuticals, Inc. (CORAR) Leonard Smith Health Physics Society (HPS) Sandy Perle Wayne Glines (alternate) Institute of Electrical an
8、d Electronic Engineers (IEEE) Mike Unterweger Institute of Nuclear Materials Management (INMM) Skip (Harrison) Kerschner National Council on Radiation Protection and Measurements (NCRP) James Cassata National Registry of Radiation Protection Technologists (NRRPT) Dwaine Brown Nuclear Energy Institut
9、e (NEI) Ralph L. Andersen Ellen Anderson (alternate) U.S. Department of Commerce Thomas J. McGiff Janna P. Shupe (alternate) U.S. Department of Energy Steve Zobel Judy Foulke (alternate) U.S. Department of Defense Tim Mikulski John Cuellar (alternate) U.S. Department of Homeland Security Peter Chiar
10、o U.S. Environmental Protection Agency Mike Boyd U.S. Nuclear Regulatory Commission Donald A. Cool U.S. Navy Jerry N. Sanders Individual member Eric Darois Individual member Tracy Ikenberry Individual member Greg Komp Individual member Joseph P. Ring Individual member L. Max Scott Individual member
11、Toshihide Ushino iii Contents Foreword iv 1.0 Purpose and Scope 1 1.1 Introduction . 1 1.2 Purpose . 1 1.3 Scope 1 2.0 Definitions . 1 3.0 Specifications of the Thyroid Phantom 2 3.1 Radioactive Material Content . 2 4.0 Physical Phantom . 3 4.1 IAEA/ANSI Neck (Thyroid) Physical Phantom Design Specif
12、ication . 3 4.2 Reference Activity 3 5.0 Computational Phantom 5 6.0 Good Practices and Uncertainty Assessment . 5 6.1 Physical Phantom . 5 6.2 Computational Phantom . 6 7.0 References . 7 7.1 Normative References 7 7.2 Informative References 7 Appendix Appendix A Thyroid Anatomy and Physiology 9 Ta
13、bles Table 1 Mass attenuation coefficients for thyroid tissue . 4 Table 2 Effective half-times . 10 Figures Figure 1 The IAEA/ANSI neck (thyroid) physical phantom 4 Figure 2 The thyroid gland 10 iv Foreword (This foreword is not part of American National Standard ANSI/HPS N13.44-2014) During 1990, t
14、he National Institute of Standards and Technology (NIST) and the Bureau of Radiation and Medical Devices (BRMD) convened a three-day workshop of in vivo measurement professionals with the goal of obtaining consensus opinion regarding the development of standard phantoms for radioactivity measurement
15、s (Kramer and Inn 1991). A standard thyroid phantom was determined to be in need of attention by the American National Standards Institute (ANSI) standards writing groups as to the “definition/re-evaluation and quality/traceability.” The current thyroid phantom standard was drafted in 1973 (ANSI N44
16、.3-1973) and was last reviewed in 1984, and a revision of the standard to cover a more modern approach was deemed warranted. For the present effort, the Working Group reviewed the basic anatomical and physiological data available for the thyroid organ. Next, commercially available thyroid phantoms w
17、ere reviewed for quality of manufacture, ease of use, and suitability of anatomical design. Modern calibration techniques were considered including the use of nonphysical computational phantom models. Lastly, proper counting methods, uncertainty analysis, and necessary elements of a quality measurem
18、ent program were addressed. AMERICAN NATIONAL STANDARD ANSI/HPS N13.44-2014 1 Thyroid Phantom Used in Occupational Monitoring 1.0 Purpose and Scope 1.1 Introduction The thyroid gland is an integral component of the human endocrine system. Consequently, the radiobiological effect associated with a ra
19、dionuclide deposited in the thyroid poses a potential health risk to the individual. An in vivo measurement or calculation quantifying such a radionuclide is therefore valuable in the assessment and possible mitigation of that health risk. The validity of an in vivo measurement is dependent upon an
20、accurate calibration of the measuring system. The calibration process typically utilizes an anthropometric phantom containing a known quantity and distribution of radioactive material. Physical characteristics of the phantom, such as mass and density, are important parameters in phantom construction
21、 and use. Likewise, the degree to which these characteristics accurately reflect those of the human body being measured is intrinsic to the value of the subsequent measurement. Therefore, adherence to standard specifications in the construction and use of a suitable thyroid phantom further ensures t
22、he consistency and quality of an in vivo measurement of radionuclides deposited in the thyroid. An additional consideration in developing a standard calibration phantom is the ability to compare results obtained by different measurement systems (e.g., at different facilities). It is understood that
23、an individuals anatomy will likely differ from a phantom regardless of how it is defined. However, there is great value in assuring that a worker with an intake of radioactive material will be reported as having approximately the same uptake to the thyroid regardless of which measurement system (or
24、facility) performs the count. This principle is demonstrated by laboratory accreditation programs. 1.2 Purpose This standard establishes the criteria for acceptable design, fabrication, or modeling of a phantom suitable for calibrating monitoring systems for in vivo measurement of photon-emitting ra
25、dionuclides deposited in the thyroid. 1.3 Scope This standard provides the specifications for the design and fabrication of physical thyroid phantoms to be used in the calibration of in vivo measurement systems. This standard includes criteria for acceptable materials, physical specifications, quali
26、ty assurance, and quality control. This standard does not specify fabrication techniques or component testing techniques. This standard provides guidance for modeling acceptable nonphysical, computational thyroid phantoms. Quality assurance requirements are provided for the use of the model in Monte
27、 Carlo computations. This standard recommends good practices as to the use of thyroid phantoms for radiological dosimetry purposes, including uncertainty assessment from improper calibrations. 2.0 Definitions The following terms are of a restricted nature for the purpose of this standard. Anthropome
28、tric: A description that preserves physical metrics, both in size and proportion, of the human body. Anthropomorphic: A description that resembles human form in shape and composition, ranging from a geometry that is simple/idealized to one that is complex/realistic. Direct radiobioassay: The measure
29、ment of radioactive material in an organism (human body) utilizing instrumentation that detects radiation emitted from that radioactive material. Synonymous with in vivo measurement. Minimum detectable activity (MDA): The smallest amount of activity of an analyte in a sample that will be detected wi
30、th a probability of nondetection (Type II error) AMERICAN NATIONAL STANDARD ANSI/HPS N13.44-2014 2 while accepting a probability of erroneously deciding that the positive (nonzero) quantity of analyte is present in an appropriate blank sample (Type I error). Phantom: A complete or partial representa
31、tion of an organism (e.g., human body) used for calibration of in vivo measurement systems. A physical phantom is constructed of tissue-substitute (or equivalent) materials in a manner to allow placement of radionuclides in a geometry approximating internal depositions. A computational phantom is a
32、nonphysical, conceptual model of the body whereby tissue materials and internal depositions are expressed mathematically. Reference values: The collection of age- and gender-specific anatomical and physiological characteristics of reference individuals defined in ICRP Publication 89 (2002). Referenc
33、e material (RM): Material characterized for the activity of radionuclides and issued with a certificate. Shall, should, may: The word “shall” is used to denote a requirement; the word “should” denotes a recommendation; the word “may” denotes permission, neither a requirement nor a recommendation. To
34、 conform with this standard, all thyroid phantom models shall include the requirements of this standard, but not necessarily its recommendations. Stylized phantom: A phantom design based upon 3-D surface equation definitions of tissues (e.g., internal organs). Tomographic phantom: A phantom design p
35、rincipally based upon segmentation of digital medical images (e.g., computed tomography and magnetic resonance imaging). 3.0 Specifications of the Thyroid Phantom The thyroid organ shall be represented by a phantom having a mass of 20 g and a density of 1.05 0.02 g cm-3. The anteroposterior length o
36、f the phantom shall not exceed 3.1 cm, the transverse length of the phantom shall not exceed 10 cm, and the vertical height of the phantom shall not exceed 8 cm. The phantom shall be symmetrical with respect to the median plane. The composition of the thyroid phantom shall be homogeneous. The thyroi
37、d phantom shall be wholly contained within a neck phantom having a minimum vertical length of 12 cm, a minimum cross-sectional diameter of 12 cm, and a density of 1.16 0.03 g cm-3. The composition of the neck phantom, excluding expressly defined tissues and organs (e.g., skeleton and trachea), shall
38、 be homogeneous. The centroid of the thyroid phantom shall be located on the median plane and at the median height of the neck phantom. The thyroid phantom shall be positioned symmetrically with respect to the median plane of the neck phantom, and the vertical axis of the thyroid phantom shall be pe
39、rpendicular to the transverse plane of the neck phantom. The anteriormost surface of the thyroid phantom shall be located 5 mm posterior to the anterior surface of the neck phantom. Deviation from the above thyroid phantom specifications must be appropriate as determined by the specific measurement
40、application (e.g., based on age, gender, or medical history of the individual) and shall be documented. The documentation shall include a comparison of the effect of the deviation upon the direct radiobioassay measurement relative to the standard thyroid phantom specification. 3.1 Radioactive Materi
41、al Content The radioactive material contained in the thyroid phantom shall be homogeneously distributed. The RM incorporated in the thyroid phantom shall be traceable to the National Institute of Standards and Technology (NIST) or to another national standards body. The quantity of radioactive mater
42、ial incorporated and the associated uncertainties shall be known and documented. The total uncertainty shall include the uncertainties in the RM, dilution AMERICAN NATIONAL STANDARD ANSI/HPS N13.44-2014 3 procedures, gravimetric analysis, counting errors, and other errors as appropriate. 4.0 Physica
43、l Phantom The standard thyroid physical phantom shall be the International Atomic Energy Agency/American National Standards Institute (IAEA/ANSI) neck (thyroid) phantom as shown in Figure 1 (ICRU 1992).1 The thyroid organ is represented by a right circular cylinder polyethylene vessel not to exceed
44、3 cm in diameter with such height that it will accept 30 ml of fluid.2 The neck phantom is a right circular cylinder 12.7 cm in diameter and 12.7 cm in height. It is constructed of polymethylmethacrylate (PMMA). A vertical plane 2.5 cm in width defines the posterior surface of the neck phantom. The
45、median plane of the neck phantom bisects this vertical plane. A vertical cavity in the neck phantom accepts the thyroid phantom. The cavity is a right circular cylinder 3.0 cm in diameter and 9.0 cm in height. The axis of the cavity is located on the median plane and perpendicular to the transverse
46、plane of the neck phantom.3 The axis of the cavity is 2.0 cm posterior to the anterior surface of the neck phantom. 4.1 IAEA/ANSI Neck (Thyroid) Physical Phantom Design Specification Additional design specifications not previously stipulated for the IAEA/ANSI neck (thyroid) physical phantom are defi
47、ned as follows. 1The design was originated by the IAEA in 1962 and was reassessed by ANSI in 1973. 2Volume capacity of vessel exceeds mass requirements specified in Section 3. This specification is an artifact of the original phantom design based upon counting procedure considerations; in particular
48、, choosing a volume comparable to the approximate mass of thyroid organs typically diagnosed for thyroid disease (IAEA 1962). 3The specified cavity positions the center of the thyroid organ RM, when represented by a 3-cm-diameter vessel having 0.16-cm-thick walls and containing 30 ml of fluid, at mi
49、dheight of a neck phantom 12.7 cm in height. Deviation from these dimensions will necessarily alter the height of the cavity or the position of the vessel within the cavity. 1. The polyethylene material used to construct the vessel shall have a density of 0.92 0.02 g cm-3. 2. The walls of the polyethylene vessel shall not exceed 0.16 cm in thickness. 3. The cavity of the neck phantom shall be backfilled with a PMMA insert so as to fully occupy the void space superior to the polyethylene vessel. 4.2 Reference Activity The reference activity shall be wholly contained within the poly
