CT灌注成像

反映组织的血管化程度及血流灌注情况，获得血液动力学方面的信息。方法：快速造影剂团注后(5ml/s以上)，在首次经过受检组织的过程中对某一选定的层面进行快速动态扫描，获得一系列动态图像，分析造影剂通过每个像素所对应的体素密度的差异，从而得到反映血流灌注情况的参数。CT灌注成像(Perfusion)脑梗塞肝、肾血流灌注及肿瘤的诊断肾移植的血流灌注的评价，了解移植血管的情况电子束CT的灌注可了解心脏灌注，有助于缺血性心肌病的早期诊断CTPerfusion应用由脑局部缺血而阻碍血液扩散是导致中风，占脑中风70%。用血纤维蛋白可溶解闭塞的血管。发生中风后，有效治疗的时间为3小时左右。要尽快了解病情类型、发病时间和局部缺血的程度。在这段时间内常规CT检查较难发现，而灌注CT可应用于急性中风检查。CT灌注前动脉供血区中动脉供血区后动脉供血区外则内侧底面脑动脉系统脑动脉系统在快速注射造影剂后，计算和脑的扩散有关的参数，从不同侧面提供中风的灌注分布情况：脑血液流量CerebralBloodFlow,CBF脑血液容量CerebralBloodVolume,CBV造影剂达到各点最大值的时间TimePeak，TP平均通过时间Meantransittime，MTT通过CBV与MTT可获得CBFCTPerfusion常规CT通过组织对X线不同衰减来显示图像CTA通过造影剂在血管内流动来显示血管结构灌注CT利用血液流动有关的参数CBF信号强示流速大；造影剂到达高峰的时间分布图TP，愈大意味着造影到达晚。CBF直接把它和向脑组织提供氧的总量联系起来，同时也与血液动力学方面有关。CTPerfusion紫色区域为血流量少,大脑急性中风区域红色区域血流量大CBF71岁妇女在症状开始90分钟后进行检查。CT平扫示无反常情况，但CBF示脑左侧(中脑和左半动脉供血)大部分，(前脑动脉)提供地区严重局部缺血，示头颅内颈动脉的双枝闭塞。CTPerfusion左半脑症状出现60分钟后，CT平扫无脑异常血液流动，(b)示左侧半脑广泛性和右前部的局部缺血。原因：左颈内动脉闭塞。CBFCBVTime-to-peakimage男44岁右脑中风约2小时，CBF在脑岛的脑皮层和豆状核后部，示严重扩散障碍(接近零)。与左边半球比较，中脑动脉血液供应相当少。CBV显示同样情况，但在右侧MCA其他地方血液容量接近正常。与左边区域比较，达到顶点时间图在延长(造影剂延迟到达)。MCAMI段栓塞和小脑膜血液供应良好，CBFTime-to-peakimage3天后CT上述病例进行动脉血纤维蛋白溶解处理，治疗后一天，用扩散CT成像显示了治疗效果，3天以后CT平扫，示梗塞形成，核心区域与CBF和CBV图像相似。在梗塞核心区域范围确定方面，CT灌注能提供重要信息，可绘局部缺血轮廓，用高密度来显示。用于辨认梗塞灶核心和周围梗塞局部缺血(阴影)，为外科提供治疗方法。通常CBV的梗塞灶小于CBF和TP，MRI也如此，一般认为CBV提供的信息较正确。早期CBV减少与随后梗塞形成程度较接近。CTPerfusion应用与CBV(b)相比CBF(a)、TP(c)在MCA中局部缺血间不匹配。在脑岛脑皮层背部(箭)有一梗塞灶。再通治疗法后24小时(d)在MCA同样位置示受限梗塞区。71-year-oldfemalepatientwithright-sidedhemiplegia(偏瘫)andglobalaphasia(失语).PlainCT(90minuteslater)revealsnoearlysignsofanischemia(局部缺血).Theparameterimagesdisplaytheentireextentoftheischemiawithahigh-gradereductionofCBFandCBV,alackingdetectionofthecontrastbolusinthetime-to-peakimage.Theinfarction(梗塞)includestheregionoftheanteriorcerebralarteryandlargeportionsoftheregionsuppliedbythemiddlecerebralartery,bothfeaturesindicativeofanocclusionoftheintracranialcarotidbifurcation.Case1Patient(male44)witharight-sidedischemiaintheregionofthemiddlecerebralartery(MCA)whichbegan160minutesago.Typicalfindingsofahigh-gradedisturbanceinperfusionintheinsularcortexandtheposteriorportionofthelentiformnucleuswithareductioninCBFandCBVasaresultofanembolicocclusioninthedistalM1segment.TheotherregionssuppliedbytheMCAdemonstratedgoodleptomeningealcollateralbloodsupplywhichonlyshowedmoderatelyreducedCBFandCBVvalues,aswellasaprolongationofthetime-to-peak.Case2InthecalculationofrelativeperfusionindicesfromCBFvaluesinischemicareasandinmirrorredROIswithintheunaffectedhemisphereprovedtobeavaluablemethodfortheprognosticevaluationofaregionwithreducedperfusion.ThecoreoftheinfarctandtheischemicmarginalzonesdemonstrateclearlydifferentCBFperfusionindices(green-markedROI=0.17versusred-markedROI=0.69).ThefindingsofperfusionCTcouldbeverifiedbyDSAwithregardtothetypeofocclusionandtheconditionofthecollateralbloodsupply.Thefollow-upCTafterasuccessfulintra-arterialfibrinolysisshowstheinfarctindimensionscomparabletotheinfarctcoreseenwithperfusionCT.70minutesaftertheoccurrenceoftheinfarction,theCBFimagerevealedahighgradeischemiainthefrontalregionofthesupplyareaoftheMCAandinthelentiformnucleus(Fig.3a)withaperfusionindexinthegreenmarkedROIof0.07(Fig.3b).Asaresultofthegoodcollateralflow,thedisturbanceinperfusionintheremainingregionoftheMCA,withaperfusionindexof0.82,isnotseentobeveryextensive(red-markedROIinFig.3b).36-year-oldmalepatientwithanembolicocclusionintheM1segmentoftheleftMCAandasimultaneousocclusionoftheleftinternalcarotidarteryasaresultofdissection.Case3Becauseofthepartiallyhigh-gradeischemiaontheonehandandtheexcellentcollateralbloodsupplyofthemarginalregionontheother,fibrinolysiswasnotperformedinspiteoftheshorttimeinterval.Asexpected,thefollow-upCTrevealedthedevelopmentofaninfarctionintheareawhichhadprimarilydemonstratedahigh-gradeischemia.灌注CT与颅脑CT扫描和颅脑CT血管造影术结合为脑梗塞早期检查提供了一种有用工具。常规CT可检查梗塞区域的形成灌注CT可决定局部缺血的区域，提供了局部缺血组织的位置和潜在病变区域CT血管造影术为诊断提供了相应病灶区域的形态。为临床工作人员决定进一步治疗的方案提供了重要信息。CTPerfusion前景目前认为中风处理的最佳时间在60分钟。通过对造影剂注入位置与方式的研究，灌注CT在不到15分钟中完成中风评价过程。Inthecourseofaninvestigationperformedon33patients,anattemptwasmadetocarryoutaquantitativeevaluationoftheseverityoftheischemiawiththeaidofanROI-evaluationoftheCBFimages.thecalculationofrelativeperfusionindicesfromCBFvaluesinischemicareasandinmirrorredROIswithintheunaffectedhemisphereprovedtobeavaluablemethodfortheprognosticevaluationofaregionwithreducedperfusion.Ischemiaswithamildtomoderatedegreeofseverity(CBFperfusionindex:0.35-0.9)progressedwellunderfibrinolytictherapy.EveninischemicregionswithaCBFindexof0.35,intra-arterialfibrinolysiscouldpreventthedevelopmentofaninfarctinmorethanhalfofthecases,aslongastheindexdidnotfallbelowacriticalvalueof0.2.Otherwise,ascouldbeverifiedwithfollow-upinvestigationscarriedoutwithcomputedtomographyandmagneticresonancetomography,ischemicnecroseswereseentodevelopwithoutexception.Inthisway,itwaspossibletomakeadifferentiationbetweentheinfarctcorewhichcannolongerbeinfluencedtherapeuticallyandthoseischemicmarginswheretherapeuticeffortswithperfusion-improvingmeasuresmaybeattemptedinordertotreatthepatientsuccessfully.