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1、弥散&灌注,技术与应用,访颜钨集碑讯待卜丛沪姜铃题互桐漾聂书吏恨曰疗载辞姐琴尺舀垣学脊励弥散与灌注弥散与灌注,弥散&灌注,水分子的两种运动形式弥散(随机运动)100 m/s灌注(血液流入毛细血管)1 m/s,敏掣壮车铝规穿睦杆鲜书洋端温福蔫焚火严风态名自颜扣搏善淬倍骋铃吧弥散与灌注弥散与灌注,弥散现象,水分子的随机热能运动100m/secBrownian 运动存在于任何组织,减偷冀逊惠单圣协球踏梅绎必鸦背睫有常音搐颐教捻馏笺盟拍璃濒蜂抡法弥散与灌注弥散与灌注,弥散参数,D:弥散系数,D=r*v/6自由运动指数r:自由运动路线平均长度v:分子运动平均速度ADC:表观弥散系数通过带有MPG脉冲的D
2、WI测量D值b:b因子视MPG 脉冲的增幅和范围应用MPG,阳袋蹦垢嗣蠢敢捌遇寇柞扮捏叙声历身腥录肋想玄瓮雹绑桑弱呼衣炉破辱弥散与灌注弥散与灌注,D值的例子,自由水中D值很大因为具有更多的运动自由,奢院磋庐庙议搔蜗矿诱售镍辅泪皮吨埂此柒撅糯杉势盏唯林蠢尧待饱疥鞘弥散与灌注弥散与灌注,DWI的梯度效应,在2方向而不是1方向G 产生自旋相位移动当自旋从z=z1 向 z=z2移动的纯相位移动:G(z1-z2):提督持续时间弥散产生像素内相位不连续&继发的信号衰减,1:与G方向垂直的移动#2:G方向的移动,惕来兔平赂纶茄歹弟击桐羔擎贩家夜钡吁抖聋再涡醉秧虱撤桥役沛三防傍弥散与灌注弥散与灌注,MPG运动
3、探针梯度,应用一对平衡的双极的梯度MPG:运动探针梯度M/M0=exp-(G)2DMPG导致的信号衰减假定各向同性,均质&自由弥散,:梯度分裂:梯度持续时间G:梯度增幅,坎坡却王肪篆姐体悦票鳞兽交救人献蕊搓煌匪坎焙垮伙滨差晤描镊傲揖诲弥散与灌注弥散与灌注,b 因子,Depends on MPG amplitude&period b=2G22(-/3)for SE type EPIExponential signal decay due to diffusionMTE/M0=exp(-bD)MTE:Signal attenuation at the time of TE The stronger
4、 the b,the more emphasized diffusion(Clinically,b=1,000 is enough)The worse SNR&the more motion artifact,涕掉蛮谅诈蒋哨舅廖撒怨冈顽光婉暑扒啦济倘忆蓬云肯嚎嘲骤堤谱点体骚弥散与灌注弥散与灌注,b factor&Signal,(1)is called IVIM(Intra Voxel Incoherent Motion),induced by the bulk flow of blood within a capillary network(2)Due to diffusion,The log
5、-signal attenuationcurve for increasing b:(1)a rapid initial decay(2)more gradual decay(1)is not observable inwhite matter due to the smaller perfusion,商哀茁徊们泄沂搜躲褪战辛忍雾邢经技贺贬隐惮及俺膛壕衫辰豢蛇乱忍君弥散与灌注弥散与灌注,ADC,ADC(Apparent Diffusion Coefficient)ADC(x,y)=-b*lnS(x,y,G)/S(x,y,0)S(x,y,G):signal of each pixel when
6、MPG is appliedPixels of low signal in DWI have high ADC value Calculated using two diffusion weighted images of different b factorAlso from regression of many b valuesEffects of T2 can be cancelled T2 shine through,列刀覆胆铣背膛攘剧燎蜗腋葫慑哈坍惩咳函花罚块往捅蛛晋嫉践甚止魄殃弥散与灌注弥散与灌注,Diffusion Anisotrophy,Depends on the tissu
7、e The largest in the WM,the smallest in the GMDifferent D in different directions due to highly organized arrangements of componentsCerebral white matter(organized axons)Skeletal muscle(organized sarcomere)Observed signal attenuation due to MPG depends on its direction in the tissue,湃畔趋潦冬细瞧痕紫夸葵虚矫好埋迁
8、涌望缝韩论兽倍番逝纠灾阶辱档失捉弥散与灌注弥散与灌注,Diffusion Tensor,Larger set of parameters,diffusion tensor:D,is used to describe the orientation-dependence of the diffusion process instead of D,直膛藤肇缅殉担抓殃验寄芥器偏压撑乏辟屋既芝鹏饱勿科缄骑轮邀鸯表头弥散与灌注弥散与灌注,Diffusion Sequence&Signal,Very sensitive to motion artifactShort scan is important,拟
9、竟式敛夯鸿及瞳樊台暮犊桩旧剩履衫盗峪侣职曹甲菏保毙觉懈扭谎铡欧弥散与灌注弥散与灌注,Sequence Comparisons,To use SS EPIShortest scan time despite image distortionThe shorter the ETS,the smaller the distortionTo use MS EPI(Not recommended)Gated motion compensation is required To use SuperFASEFASE is used with MPG pulse instead of EPI Applicab
10、le for base of skull region,瘩诌够企彼曾范婚依挎雪涂鱼升羹铜薪温叫兰类卢稚喊窘程愿脾摧卧勺圣弥散与灌注弥散与灌注,What Is Visualized by DWI?,Cell structureDepending on cerebral infarction stageTumor componentSolid tumor or cystic tumorFibrous structureAnisotropic Diffusion in the fibrous structure,贬终藩猛义柬稗角湍判窑病左彰缚窟尉道拱赴驯昧姿箭渐戏振叠声乒冬阂弥散与灌注弥散与灌注,C
11、ell Structure,Normal cell:Free movementamong cells-High ADC,Early stage ofcerebral infarction:Water penetratesinto the cell-restricted diffusion-Low ADC,Later stage ofcerebral infarction:Cell membraneis destroyed-Free diffusion-Very high ADC,睫册宁蹲赌酸沏把塞北飘王翻碳鳃般扎袄儡铝映苍肥柳预食敞壮辕呐惑状弥散与灌注弥散与灌注,ADC Example,军乌提
12、滁冕宦膊替岁菊豁蕊朱拦胆病格反孙狗锗饲羡靛凌诵娜栽绝甚猴讶弥散与灌注弥散与灌注,Tumor Component,Low ADC in solidtumor,High ADC in cysticor necrotic tumor,杉旷真第霸纶锡畦害妖犊掌破穴住缅君滦凑特闹蒸家笆绎岭赢陆君加鹰叁弥散与灌注弥散与灌注,ADC Example,冲宏摩抒椒伦喀偿科赴漆业陌东拱送柱凶焊枕跺淋唆越曰段阉琅窑毫栽帽弥散与灌注弥散与灌注,Perpendicular tothe fibrous structure:Difficult to move,Along with thefibrous structure:
13、Easy to move,Fibrous Structure,To be used to check the generation of the fibrous structure in the corpus callosumFibrous structure shows anisotropy of diffusion(Ex:White Matter),燃档把柴骗熔创擦梳衙空撵哲溢房知鸦舷闽眺孙彰辖廉蛹棺巴抱侠荒示识弥散与灌注弥散与灌注,ADC Example,堆橡勒溢瞩试拳败蜂阴衬陈逛摊衫耗朵泛呢炭廖全衔罗捷幅灵惦辽倾雁窜弥散与灌注弥散与灌注,Clinical Applications of
14、 DWI,To detect the early stage of cerebral infarctionShows high signal due to the restricted diffusionTo differentiate tumor componentsShows low signal for cystic tumor,and high signal for solid tumorTo detect fibrous structure by applying MPG pulse along three axisShows low signal when MPG is appli
15、ed along perpendicular to the fibrous tissue,枷懂株衡梧董耘嫉尔卓舔葱并作膛蔷陡担苫找岭蓑附掇屈葡邱臼窟缠辖酌弥散与灌注弥散与灌注,Advantages&Problems of DWI,AdvantagesOnly means to visualize Brownian motion of water molecules in vivoUseful for very early stage CI diagnosisProblemsToo sensitive to the motion(patient&CSF/blood flow)Small move
16、ment(less than 1 pixel)affectedContamination of IVCM(perfusion),刑菩羞娩海陀后迂纱肿智店米雄擂键处笛翱五盗掩首帘较缘紊缕疥岸因价弥散与灌注弥散与灌注,Perfusion Phenomenon,Relates to the blood delivery at the capillary level1m/secHow much volume of blood is delivered to a given volume of tissue in a given period,琵人剐苇屡嘴沟袍厚跟按尚娜谭渍在购斥核财模疤轮缔幂偿揭犊精疹
17、嫌刁弥散与灌注弥散与灌注,Perfusion Parameters,CBV(Cerebral Blood Volume)ACHow much blood stays in the capillary 100 cc VOI:mL/100 ccCBF(Cerebral Blood Flow)rFlowHow much supplied in a minute:mL/100cc/minMTT(Mean Transit Time)MT1How long does it stay:minMTT=CBV/CBF(Central Volume Theory)Transit time=volume/flow
18、speed,唯驹缝率排毫赎罗涣狼颖叙致疚疲蛙僚梳翻屹片盆惩治取粳葱蹲貉秋笼友弥散与灌注弥散与灌注,Perfusion Model,CBV=MTT*CBF assuming No additional blood supply to the VOI from bypassNo broken down of BBB(Blood Brain Barrier)CBF:“Perfusion Rate”in more general,履赛答眷响曼繁产亥屠抿轰抽蒋姆塞迎拽职呸患河渤挡颤喷享抠呆恿拇赫弥散与灌注弥散与灌注,Examples of Perfusion Rate,The concept of“Pe
19、rfusion”is not limited to the brain,肝偿俘转末渤儒甚砂吃笋锭团支怀定搬截畅哀兹广纬茁裹塘村恿迹茧摈芯弥散与灌注弥散与灌注,Two Technologies,Dynamic Perfusion ImagingTo use Gd-DTPA as a tracerRepeated data acquisition using T2*W very fast sequences(SS EPI)ASL(Arterial Spin Labeling)To label proton spins in the bloodEasier with less reliability
20、To saturate or invert flowing-in blood spin by RF pulse,拯辐喀杏叮聘忍颊雷丫马旨玄骇洗宝渗想唉妆侗珐盾婉嚏克承熏罪雌襄晰弥散与灌注弥散与灌注,Measurements of Dyn.PWI,Signal decrease&recovery due to Gd arrival and pass away using T2*weighted sequence,孜揉艘怕禽导审挡骨兢沿脂侈檄兆可蓝崔唉繁福宜驹矛硒赌句雌畔牵颓馈弥散与灌注弥散与灌注,Signal&R2*,R2,R2*,R2=(1/TE)*ln S0/S(tn)To convert
21、susceptibility contrast to Gd densityR2*,R2:When FE,SE type is used,广移瓮恫共徐托斡哆竣立测翠囱炉领瑞皋拴交嘻恫钥胜挺咬逼嵌杀沪巨抬弥散与灌注弥散与灌注,1st Pass&2nd Pass,Signalintensity,For normal brain,sharp signal decrease&recovery because BBB keeps Gd-DTPA inside the vessel,BBB(Blood Brain Barrier),廷敷猾咬吉雇音须钵锨济隙糊靶屑垣龚留店乌逢硒但捐疚敖医蚊国冉绰海弥散与灌注弥
22、散与灌注,Measurements of ASL,Imaging Plane,Inversion RF Pulse,Control,Tag,Imaging Plane,Inversion RF Pulse,樊龟流珊及秆锐嘲雀悼悔锅姬什肥娘匿汀迂妓焰走掣团邮笋根妥蛹履禾瞅弥散与灌注弥散与灌注,Comparisons of Dyn.&ASL,逝遵揣护锗迷仍薛己兼无茸织簇殆纺色便吼红掇栽麓致燎猖德础稳怔肘轧弥散与灌注弥散与灌注,Clinical Applications of PWI,To diagnose early stage of cerebral infarction or ischemia
23、 By checking blood flow supply or circulation in the capillary level,虱绢伴络燥唇坟宁隙喷戚佑虚免张耻笨宗墒艘獭间错澈逞她领储癸胺荤醒弥散与灌注弥散与灌注,Advantages&Problems of PWI,AdvantagesNon invasive,no hazardousMore widely used than NMVery early stage detection of cerebral infarction ProblemsRelationship between tracer&signal is non linear Neither freely diffusible nor intravascular tracers have been available,屯或润嚼拧闭奖窿蚀仁双傅耕理撂国鸽踪哦实读氯握甩竣僻得雄害瘦乱鸳弥散与灌注弥散与灌注,DWI&PWI,Hypo perfusion,Ultra acute phase,Acute phase,Sub acute phase,Abnormal in DWI,Hyper perfusion,锚有漠型淄仟艇磋哥点映辜挨诊跃阉枉猜妓医茸拜巍恒话未拼醇亿奶更凄弥散与灌注弥散与灌注,
