【英文标准名称】:StandardTestMethodforCalibratingandMeausringCTDensity
【原文标准名称】:校准和测量计算机断层摄影密度的标准试验方法
【标准号】:ASTME1935-1997(2008)
【标准状态】:现行
【国别】:美国
【发布日期】:1997
【实施或试行日期】:
【发布单位】:美国材料与试验协会(US-ASTM)
【起草单位】:E07.01
【标准类型】:(TestMethod)
【标准水平】:()
【中文主题词】:
【英文主题词】:computedtomography;contrastsensitivity;CTdensityresolution;densitycalibration;linearattenuationcoefficient;massattenuationcoefficient;Computedtomography(CT);Contrastmanipulation/sensitivity;CTdensityresolution;Linearattenuatio
【摘要】:ThistestmethodallowsspecificationofthedensitycalibrationprocedurestobeusedtocalibrateandperformmaterialdensitymeasurementsusingCTimagedata.Suchmeasurementscanbeusedtoevaluateparts,characterizeaparticularsystem,orcomparedifferentsystems,providedthatobservedvariationsaredominatedbytruechangesinobjectdensityratherthanbyimageartifacts.ThespecifiedproceduremayalsobeusedtodeterminetheeffectiveX-rayenergyofaCTsystem.TherecommendedtestmethodismoreaccurateandlesssusceptibletoerrorsthanalternativeCT-basedapproaches,becauseittakesintoaccounttheeffectiveenergyoftheCTsystemandtheenergy-dependenteffectsoftheX-rayattenuationprocess.This(orany)testmethodformeasuringdensityisvalidonlytotheextentthatobservedCT-numbervariationsarereflectiveoftruechangesinobjectdensityratherthanimageartifacts.Artifactsarealwayspresentatsomelevelandcanmasqueradeasdensityvariations.Beamhardeningartifactsareparticularlydetrimental.Itistheresponsibilityoftheusertodetermineorestablish,orboth,thevalidityofthedensitymeasurements;thatis,theyareperformedinregionsoftheimagewhicharenotoverlyinfluencedbyartifacts.Linearattenuationandmassattenuationmaybemeasuredinvariousways.Foradiscussionofattenuationandattenuationmeasurement,seeGuideE1441andPracticeE1570.FIG.1DensityCalibrationPhantom1.1ThistestmethodcoversinstructionfordeterminingthedensitycalibrationofX-andx03B3;-raycomputedtomography(CT)systemsandforusingthisinformationtomeasurematerialdensitiesfromCTimages.ThecalibrationisbasedonanexaminationoftheCTimageofadiskofmaterialwithembeddedspecimensofknowncompositionanddensity.ThemeasuredmeanCTvaluesoftheknownstandardsaredeterminedfromananalysisoftheimage,andtheirlinearattenuationcoefficientsaredeterminedbymultiplyingtheirmeasuredphysicaldensitybytheirpublishedmassattenuationcoefficient.Thedensitycalibrationisperformedbyapplyingalinearregressiontothedata.Oncecalibrated,thelinearattenuationcoefficientofanunknownfeatureinanimagecanbemeasuredfromadeterminationofitsmeanCTvalue.Itsdensitycanthenbeextractedfromaknowledgeofitsmassattenuationcoefficient,oronerepresentativeofthefeature.1.2CTprovidesanexcellentmethodofnondestructivelymeasuringdensityvariations,whichwouldbeverydifficulttoquantifyotherwise.Densityisinherentlyavolumetricpropertyofmatter.Asthemeasurementvolumeshrinks,localmaterialinhomogeneitiesbecomemoreimportant;andmeasuredvalueswillbegintovaryaboutthebulkdensityvalueofthematerial.1.3AllvaluesarestatedinSIunits.1.4Thisstandarddoesnotpurporttoaddressthesafetyconcerns,ifany,associatedwithitsuse.Itistheresponsibilityoftheuserofthisstandardtoestablishappropriatesafetyandhealthpracticesanddeterminetheapplicabilityofregulatorylimitationspriortouse.
【中国标准分类号】:C43
【国际标准分类号】:35_240_80
【页数】:5P.;A4
【正文语种】:英语


【英文标准名称】:ElectromagneticcompatibilityandRadiospectrumMatters(ERM)-RadioFrequencyIdentificationEquipmentoperatingintheband865MHzto868MHzwithpowerlevelsupto2W-Part1:Technicalrequirementsandmethodsofmeasurement(Endorsementofthe
【原文标准名称】:电磁兼容性和无线电频谱情况(ERM).功率等级≤2W的在频带865MHz～868MHz上工作的的射频识别设备.第1部分:技术要求和测量方法
【标准号】:EN302208-1-2006
【标准状态】:现行
【国别】:
【发布日期】:2006-12
【实施或试行日期】:
【发布单位】:欧洲标准学会(EN)
【起草单位】:
【标准类型】:()
【标准水平】:()
【中文主题词】:频带;电磁兼容性;频率;识别;测量仪器;测量技术;功率等级;无线电工程;射频识别;规范(验收);电信;无线通信业务
【英文主题词】:
【摘要】:电磁兼容性和无线电频谱情况(ERM).功率等级≤2W的在频带865MHz～868MHz上工作的的射频识别设备.第1部分:技术要求和测量方法
【中国标准分类号】:L06
【国际标准分类号】:33_060_99;33_100_01
【页数】:2P.;A4
【正文语种】:英语