1、The Institute of Electrical and Electronics Engineers, Inc.3 Park Avenue, New York, NY 10016-5997, USACopyright 1999 by the Institute of Electrical and Electronics Engineers, Inc.All rights reserved. Published 28 May 1999. Printed in the United States of America.IEEE is a registered trademark in the
2、 U.S. Patent (978) 750-8400. Permission to photocopyportions of any individual standard for educational classroom use can also be obtained through the Copy-right Clearance Center.Copyright 1999 IEEE. All rights reserved.iiiIntroduction(This introduction is not part of ANSI N42.27-1999, American Nati
3、onal Standard for Determination of Uniformity ofSolid Gamma-Emitting Flood Sources.)This standard is the responsibility of the Accredited Standards Committee N42 on Radiation Instrumenta-tion. Committee N42 delegated the development of this standard to its subcommittee N42.RM. Drafts werereviewed by
4、 Committee N42, Subcommittee N42.RM, and other interested parties, and the commentsreceived were utilized in producing the standard as finally approved. At the time it approved this standard, the Accredited Standards Committee on Radiation Instrumentation,N42, had the following members:Louis Costrel
5、l,ChairSue Vogel,Administrative SecretaryOrganization Represented Name of RepresentativeAmerican Conference of Governmental Industrial Hygienists Jesse LiebermanApplied Safety Technology Edward J. Vallario*Battelle Pacific Northwest Laboratories Joseph C. McDonaldBicron. Joseph G. BellianChew, M. H.
6、 . Jack M. SelbyEberline Instrument Company . James K. HeschEG&G ORTEC Sanford WagnerGamma-Metrics . Ernesto A. CorteHealth Physics Society. George CampbellJoseph R. Stencel (Alt.)Institute of Electrical and Electronics Engineers. Louis CostrellJulian Forster (Alt.)Anthony J. Spurgin (Alt.)Lawrence
7、Berkeley Laboratory Edward J. LampoLawrence Livermore National Laboratory. Gary JohnsonLovelace RR Institute. Morgan CoxMassachusetts Institute of Technology, Bates Linear Accelerator Center . Frank X. MasseNASA/GSFC, U.S Donald E. Stilwell*Nuclear Standards Unlimited. Al N. TschaecheOak Ridge Natio
8、nal Laboratory. Charles L. BrittonSwinth Associates Kenneth L. SwinthU.S. Army Center for EW/RSDA Edward GroeberU.S. Department of Commerce, National Institute of Standards and Technology Louis CostrellMichael Unterweger (Alt.)U.S. Department of Energy/PCSRD Natesh VarmaU.S. Federal Emergency Manage
9、ment Agency . Carl R. SiebentrittMembers-at-Large Paul L. PhelpsLee J. Wagner* DeceasedAt the time this standard was approved, Subcommittee N42.RM had the following members:Frank X. Masse,ChairJ. M. R. Hutchinson,SecretaryRobert AyresJoseph G. BellianJohn D. BuchananR. F. ColeyBert M. CourseyMichael
10、 DevineRoger FerrisRobert J. GehrkeY. KobayshiMarkku KoskeloJoel L. LazewatskyDavid E. McCurdyD. M. MontgomeryCarl W. SeidelJohn SonewaldMichael UnterwegerivCopyright 1999 IEEE. All rights reserved.The working group for this standard had the following members:Joel L. Lazewatsky,Chair and project lea
11、der The following persons were on the balloting committee that approved this document for submission to theAmerican National Standards Institute:*DeceasedCatherine K.N. BergerIEEE Standards Project EditorLou EdmondFrederic FaheyMarvin FriedmanL. Stephen GrahamThomas KumpurisCarl W. SeidelDavid Weber
12、Joseph G. BellianCharles L. BrittonGeorge CampbellErnesto A. CorteLouis CostrellMorgan CoxJulian ForsterJohn M. GallagherGerald GoldsteinEdward GroeberJames K. HeschGary JohnsonEdward J. LampoJesse LiebermanFrank X. MasseJoseph C. McDonaldPaul L. PhelpsJack M. SelbyCarl R. SiebentrittDonald E. Stilw
13、ell*Anthony J. SpurginJoseph R. StencelKenneth L. SwinthAl N. TschaecheMichael UnterwegerEdward J. Vallario*Natesh VarmaLee J. WagnerSanford WagnerCopyright 1999 IEEE. All rights reserved.vContents1. Introduction 11.1 Scope 11.2 Special word usage 12. References 23. Definitions 24. Procedure require
14、ments . 34.1 Test and Measurement Report . 34.2 Required reportable parameters . 34.3 Methodological requirements 44.4 Constancy of system response . 54.5 Detailed method of measurement 65. Precautions and sources of error 65.1 Dependence upon measurement orientation 65.2 Backscatter and surrounding
15、 geometry 65.3 Interference from nearby sources. 65.4 Calculation error 6Annex A (informative) Methodological example . 7Copyright 1999 IEEE. All rights reserved.1American National Standard for Determination of Uniformity of Solid Gamma-Emitting Flood Sources1. IntroductionNuclear medicine practitio
16、ners use solid, uniformly radioactive sources that are several millimeters thickwith areas up to 0.25 m2(called “flood” sources) to characterize and correct the extrinsic flood field unifor-mity of scintillation cameras for purposes of both quality assurance and on-line operational corrections.These
17、 radioactive sources are intended to produce a uniform radiation field across the cameras usable fieldof view. Methods to evaluate camera uniformity are described in NEMA NU 1-1994.1A broad range of flood sources is available in many sizes and configurations from a number of manufactur-ers. Such div
18、ersity suggests the need for a uniform means of reporting calibration data and a common under-standing of the parameters reported. This information can permit intercomparison of sources and givepractitioners a means to determine whether a particular source is appropriate for a given task.1.1 ScopeTh
19、e scope of this standard is limited to commercially-produced, solid radioactive flood sources intended toaid in the determination of the system field uniformity of scintillation cameras used in nuclear medicine.This standard is intended to provide a set of minimum informational requirements for a Te
20、st and Measure-ment Report for flood sources used with scintillation cameras. It is not intended to specify the means bywhich such information is obtained, although it does place requirements and limitations on the methodology.In addition, it is not intended to cover the use of the source in the det
21、ermination of the operating characteris-tics or correction factors for a scintillation camera.1.2 Special word usageThe words shallor mustindicate a procedure that is necessary to meet the requirements of this standard. Thewords shouldor mayindicate an advisory recommendation that is to be applied w
22、hen practicable.1Information on references can be found in Clause 2.ANSIN42.27-1999 AMERICAN NATIONAL STANDARD FOR DETERMINATION OF2Copyright 1999 IEEE. All rights reserved.2. ReferencesThis standard shall be used in conjunction with the following publications. If the following publications aresuper
23、seded by an approved revision, the revision shall apply.ASTM E456-96, Standard Terminology for Relating to Quality and Statistics.2NEMA NU 1-1994, Performance Measurements of Scintillation Cameras.33. DefinitionsFor the purposes of this standard, the following terms and definitions apply:3.1 accurac
24、y: The closeness of agreement between a test result and an accepted reference value.(The word“accuracy” is to be understood as it is defined in ASTM E456-96.) 3.2 penumbra: The area over which the sensitivity of the measurement system falls from 90% of its maxi-mum value within the unit cell to 10%
25、of that value.3.3 statistical terminology:See:accuracyand uncertainty. 3.4 uncertainty: An indication of the variability associated with a measured value that takes into accounttwo major components of error: 1) bias, and 2) the random error attributed to the imprecision of the measure-ment process.(
26、The word “uncertainty” is to be understood as it is defined in ASTM E456-96.)3.5 uniformity:A quantitative description of the two-dimensional distribution of the photon flux emitted bya radioactive flood source, describing variations in that flux for specified areas.3.6 unit cell (UC):An area on the
27、 source to which a single localized measurement value applies. The UC isthe two-dimensional region (in the plane of the measured surface of a source) defined by the response of themeasurement system to a point source located in the plane of the source and of the same radioactive compo-sition as the
28、flood source.The UC encloses all points at which the sensitivity of the system is equal to or greater than half that of themaximum value measured.NOTES:1. For this standard, the area of the UC should be 1 cm2or less, but in no case shall it be greater than 6.5 cm2.2. This standard may not be constru
29、ed as to imply any ability to determine the presence of defects smaller than one UC.3.7 useful region (UR):The region of the source within which all measurements are made and for which allare certified to be correct. All measurements shall be performed and reported for the UR, recognizing thatmeasur
30、ement asymmetries are likely to be present at the edge of the source. The source may extend outsidethe UR, but no claim is made as to uniformity outside of the UR.2ASTM publications are available from the American Society for Testing and Materials, 100 Barr Harbor Drive, West Conshohocken,PA 19428-2
31、959, USA (http:/www.astm.org/).3NEMA publications are available from Global Engineering Documents, 15 Inverness Way East, Englewood, Colorado 80112, USA(http:/ OF SOLID GAMMA-EMITTING FLOOD SOURCES N42.27-1999Copyright 1999 IEEE. All rights reserved.34. Procedure requirements4.1 Test and Measurement
32、 ReportEach flood source shall be accompanied by a Test and Measurement Report that shall contain the followinginformation: The primary radionuclide and all measurable radioactive impurities (as defined in 4.2) and theamount of radioactivity of each. The spatial uniformity of the emitted photon flux
33、 in terms of all required parameters described in thisstandard. The method by which these quantities have been measured. A summary of the statistical analysis of the data sufficient to determine the bias and imprecision ofmeasurement throughout the analysis of a given source. A description of the sy
34、stem constancy procedure as discussed in 4.4. A statement that the measurement system is maintained, calibrated, and validated using a validatedStandard Operating Procedure (SOP). A statement that the source was evaluated using a validated SOP that conforms to the requirementsof current good manufac
35、turing practice (cGMP) or equivalent.4.2 Required reportable parametersThe following parameters shall be reported in the Test and Measurement Report: The primary and impurity radionuclide content at the time of calibration shall be reported to an accu-racy of 10% at the 95% confidence level. All rad
36、ionuclide species present in the source at concen-trations greater than 0.05% of the activity of the primary radionuclide shall be listed individually.Total radionuclide impurity concentration shall be reported with an accuracy of 10% (at the 95%confidence level). A calculated estimate of the primar
37、y and impurity radionuclide content at a time equal to two half-lives (from the date of manufacture) of the primary radionuclide shall be reported. This shall be inthe same form as used in the impurity report described in the previous paragraph. This will report theconcentrations of all radionuclide
38、s reported in the initial impurity report as well as any other knownimpurities that are estimated to be present in concentrations greater than 0.05% of the primary radi-onuclide at the later time. The shape and dimensions of the unit cell (UC) in the normal counting geometry, including the widthof t
39、he penumbra (the area over which the sensitivity of the measurement system falls from 90% ofits maximum value within the UC to 10% of that value) shall be reported. A complete description of the cluster in terms of size, shape, and distribution within the useful region(UR).For the entire UR, the fol
40、lowing shallbe reported: The number of UC measurements, the mean, and the measured sample standard deviation of the UCcount for the entire UR. The Maximum Absolute Deviation from the Mean (MADM), defined by the largest sample differ-ence from the mean UC value, expressed as a percentage of the mean
41、UC value. The Coefficient of Variation (CV), defined by the standard deviation of the distribution of UC valuesdivided by the mean UC value and expressed as a percentage.ANSIN42.27-1999 AMERICAN NATIONAL STANDARD FOR DETERMINATION OF4Copyright 1999 IEEE. All rights reserved. The Integral Uniformity
42、(IU), in percent, defined as 100 (UCmax UCmin)/(UCmax + UCmin), whereUCmax represents the largest and UCmin the smallest UC measurement acquired over the UR, respec-tively.For the entire UR, the following shouldbe reported: The Differential Uniformity (DU), in percent, defined as 100 DUCmax/DUCsum.
43、This parameter isdetermined by the following method:1) For each measurement protocol, a cluster of UCs is defined. This cluster consists of a cluster ofbetween 7 and 12 UCs, where the boundary of the cluster is as convex as possible and all UCswithin the cluster boundary are included in all calculat
44、ions. All possible clusters that are com-pletely within the UR are used in the following calculation.2) Within each cluster, the pair of UCs exhibiting the largest difference in measured count rate isidentified (this difference is designated DUCi). When all clusters have been examined, the larg-est
45、DUCiis selected. This is DUCmax. DUCsumis simplythe sum of the measured values of thetwo pixels from which DUCmaxwas obtained.4.3 Methodological requirements4.3.1 GeneralUniformity shall be evaluated using a collimated detector or detectors positioned above or below the surfaceof the flood source so
46、 as to derive information from an array of measurements of UCs. The UC shall be com-pletely characterized by its description in the Test and Measurement Report.4.3.1.1 ConfigurationAll measurements shall be made with the source in the configuration as it would normally be used. 4.3.1.2 Useful region
47、The UR of the source shall be defined by the manufacturer by a dimensioned figure. This figure shall definethe orientation and position of the UR within the physical area of the source.4.3.1.3 Unit cellIndividual measurements comprising the evaluation shall be referenced to the UC.4.3.1.4 SamplingMe
48、asurements shall be taken at a sufficient number of positions of the UC within the UR so that no less than100% of the UR is measured. Sampling shall be uniform over the UR of the source, with appropriate over-sampling to ensure that sensitivity to defects is uniform throughout the UR. For continuous
49、, rotational scan-ning, the rotational speed of the source must be adjusted with detector radius so that the detector alwaysscans the same total area per unit time.4.3.2 Uniformity measurementThe measurement system shall have the ability to determine a parameter that is proportional to the localgamma-ray flux (as defined by the UC) from the flood source in the prescribed configuration.ANSIUNIFORMITY OF SOLID GAMMA-EMITTING FLOOD SOURCES N42.27-1999Copyright 1999 IEEE. All rights reserved.54.3.3 Required measurement pr
