急性脑缺血CT灌注成像各参数动态变化的实验研究

目的 :采用自体血栓栓塞模型研究CT灌注成像各参数在脑缺血 12h内的动态变化以及计算各参数的半暗带阈值。方法 :5只新西兰大白兔行自体血栓栓塞制成局灶性脑缺血模型。采用GELightspeed 16MSCT ,在基础灌注后于栓塞后 2 0min扫描一次 ,1～ 6h内每隔 1h扫描一次 ,6～ 12h内每隔 2h扫描一次。CT灌注软件可以给出每个时间点的各参数图。在完成缺血后 12hCT灌注扫描后 ,断头取脑 ,进行TTC染色 ,并根据CT灌注各参数图和TTC的染色结果将梗塞侧分为中心梗塞区 ,半暗带区和相对正常区三部分。结果 :所有参数的动态变化可分为三个阶段 :①梗塞后 2h内 :CBV在中心梗塞区明显下降 ,在半暗带区轻度下降或正常 ,在相对正常区轻度上升 ,CBF在三个区域均明显下降 ,MTT和TTP均明显延长 ;②梗塞后 2～ 5h :所有参数均在一定水平上轻度波动 ;③梗塞后 5～ 12h :在中心梗塞区和半暗带区CBV和CBF下降 ,MTT和TTP延长和轻度缩短 ,而在相对正常区CBV和CBF明显上升 ,MTT和TTP明显缩短。在缺血 2 0min时 ,若CBV % <6 6 .5 7% ,CBF % <39.2 2 % ,MTT % >2 .6 3或TTP % >1.97,缺血组织就发生不可逆损伤。结论 :实验证明CT灌注成像能够准确地显示脑缺血的部位和范围 ,也能在一定程度上反映脑缺血的病理生理改变。CT灌注检查能够指导     

脑梗死前期脑局部微循环障碍CT灌注成像的实验研究

目的 从微循环的角度探讨脑梗死前期CT灌注成像表现及其病理基础，以及星形细胞与脑局部微循环的关系。方法 建立大鼠脑局部低灌注模型和脑局部星形细胞水肿模型，在动态CT脑灌注成像检查后处死，分别作灌注CT参数图、红四氮唑(TTC)染色、电子显微镜(简称电镜)和光学显微镜(简称光镜)观察。脑局部低灌注模型作了局部脑血流量(regional cerebral blood flow，rCBF)、局部脑血容量(regional cerebral blood volume，rCBV)、平均通过时间(mean transit time，MTT)和最大峰值时间(time-to-peak，TTP)比值(病侧／健侧)测量。结果 大鼠脑局部低灌注模型实验组的rCBF和MTT参数图显示病变侧低灌注区，rCBV和TTP参数图未见异常。rCBF、rCBV、MTT和TTP的比值范围分别为：0．39～0．55、0．92～1．00、1．20～1．50和1．00～1．00。电镜见星形细胞水肿，肿胀的星形细胞足板挤压毛细血管使管腔狭窄或闭塞；神经元表现正常或有轻度可逆损伤。假手术组各个参数图、TTC染色、电镜以及光镜未见异常。大鼠脑局部星形细胞水肿模型实验组4只大鼠的rCBF和MTT参数图均见星形细胞水肿所造成的局部低灌注带和局部MTT延长区域，其中3只rCBV参数图显示异常低灌注区，2只TTP参数图显示TTP异常延长区域。rCBF、rCBV、MTT和TTP的比值范围分别为：0．25～0．44、0．70～1．01、1．20～2．00和1．02～1．45。电镜观察到星形细胞水肿，足板不同程度的肿胀，极度肿胀的星形细胞足板挤压毛细血管使管腔狭窄或闭塞；神经元基本正常或仅有核膜凹陷。对照组的CT灌注成像、TTC染色、电镜和光镜均未见异常。结论 rCBF下降到电衰竭阈值和膜衰竭阈值之间时，星形细胞可以作出比神经元更为迅速的反应，即星形细胞水肿。星形细胞足板肿胀使得毛细血管的管腔变窄，造成局部微循环障碍，加重脑局部的缺血缺氧。动态CT脑灌注成像可清楚地显示上述状态下异常血液动力学变化，rCBF与rCBV之间的变化关系可提示脑缺血区微循环障碍的程度。     

脑梗死早期局部自发性血流再灌注全脑CT灌注成像表现

目的探讨全脑CT灌注成像(CTPI)对发现缺血性脑卒中早期局部自发性再灌注现象的价值。方法回顾分析110例急性期和亚急性早期(6h～10天)缺血性脑卒中患者临床资料及全脑CTPI参数图〔脑血容量(CBV)、脑血流量(CBF)、平均通过时间(MTT)、达峰时间(TTP)和延迟(Delay)图〕。以患者未接受静脉或动脉溶栓治疗,并且首次CT-PI显示梗死脑区CBV减低、复查CTPI显示梗死脑区CBV为正常或增高定义为自发性再灌注区,分别观察各灌注参数图的特点并测量再灌注区和对侧镜像正常脑区各灌注参数值,采用配对t检验比较再灌注区与对侧正常脑区灌注参数值的差异。结果共有15例存在自发性再灌注现象,距发病平均时间为61.5h,自发性再灌注脑区表现为CBV/CBF增高、TTP延长(P<0.05)。结论全脑CTPI能可靠发现脑梗死早期自发性再灌注现象,为临床治疗提供重要信息。     

CT灌注成像与MR灌注成像诊断急性缺血性脑卒中的对比研究

目的探讨CT灌注成像(CTPI)与磁共振灌注成像(PWI)对急性缺血性脑卒中(AIS)的诊断效果。方法前瞻性的选取2019年1月～2019年12月我院收治的62例AIS患者作为观察对象,均行CTPI、PWI检查,观察CTPI、PWI影像学特征,记录脑损伤程度,并分析CTPI、PWI灌注参数及患者预后。结果 CTPI影像学表现为梗死中心CBF降低、TTP则不同程度的延迟/消失,PWI影像学表现为梗死中心CBV降低、MTT延长。在脑实质损害程度上,CTPI、PWI检查的一致性高(Kappa=0.874)。灌注参数比较,CTPI、PWI梗死区、半暗带区、健侧CBF、CBV、TTP、MTT差异显著(F=119.549、293.514、63.748、99.240、113.362、193.615、61.965、88.068,P0.05);且CTPI、PWI梗死区CBF、CBV、MTT均显著低于半暗带区、健侧(P均0.05),而TTP显著高于半暗带区、健侧(P均0.05);CTPI、PWI在各区域灌注参数比较差异均无统计学意义(P0.05),CTPI的操作时间显著低于PWI(t=12.251,P0.05)。结论 CTPI、PWI在AIS脑损伤程度的诊断效果相当,且梗死区、半暗带区及健侧的灌注参数变化相似,虽然CTPI耗时较少,但临床选择何种方式仍需视实际情况。     

多层螺旋CT灌注成像评价颌面部肿瘤微血管密度的研究

目的评价颌面部肿瘤多层螺旋CT（MSCT）灌注成像（PI）与微血管密度（MVD）的相关性。方法对31例颌面部肿瘤患者术前行MSCT灌注扫描，所得图像数据经计算机软件计算获得肿瘤感兴趣区（ROI）的时间一密度曲线及灌注量（perfusion）、增强峰值（PEI）、达峰值时间（TTP）等灌注参数的数值。采用免疫组织化学方法测定病理标本的Ⅷ因子，检测病灶的MVD，分析MSCT灌注成像参数与MVD的相关性。结果颌面部肿瘤的微血管密度增高，且与肿瘤恶性程度明显相关。MSCT灌注参数中perfusion、TTP与MVD明显相关（P值均〈0．05），而PEI则相关性不明显（P〉0．05）。不同类型灌注曲线的MVD间差异有统计学意义（P〈0．05），其中速升型组的MVD最高。结论MSCT灌注成像灌注参数perfusion、TTP及灌注曲线类型与肿瘤MVD明显相关，能反映肿瘤内微血管密度，有助于对颌面部肿瘤血管生成及其预后进行评价。     

超急性脑梗死再灌注扩散加权-灌注磁共振成像及病理变化

目的应用扩散-灌注(DWI-PI)磁共振成像技术对改良线栓法建立的超急性脑梗死再灌注模型进行实验研究,并与病理结果对照.明确该技术对超急性脑梗死再灌注的评价作用.材料与方法 50只SD大鼠,随机分成5组,A组(10只)行假手术作对照,其余按栓塞时间30 min、1、3、6 h均分成B、C、D、E 4组;行DWI、PI和常规质子密度加权成像(PDWI)、T2WI、T1WI扫描;DWI和PI原始图像重建获得表观扩散系数(ADC)、脑血容量(CBV)、脑血流量(CBF)、平均通过时间(MTT)参数形态图.观察各栓塞时间点和再灌注2、24 h后各项参数变化,并将其结果与四氮唑红(TTC)染色和病理观察对比.结果 A组DWI、PI成像无异常信号,病理观察和TTC染色无变化.B组再灌注2 h DWI高信号消失,ADC值恢复正常化(88.27±1.92)%,24 h继发性ADC值降低和DWI高信号;C组再灌注2 h后ADC值轻度升高,24 h明显降低;D、E组再灌注2、24 h ADC值轻度降低或基本不变;各组再灌注后24 h DWI显示病灶范围无明显扩大.A、B组再灌注后PI各参数指标(CBV、CBF、MTT)恢复和维持正常,而D、E组的信号强度-时间曲线图有3种表现,分别为高灌注、低灌注和正常灌注.超急性脑梗死再灌注后DWI显示的缺血范围与TTC异常染色(白色)范围无显著性差异(方差分析,P＞0.05).结论在超急性脑梗死中大脑中动脉栓塞30 min再灌注后初次DWI异常信号消散是暂时的,以后会发生继发性DWI异常信号,再灌注后初次DWI异常信号消散区24 h后观察到神经元坏死;再灌注可限制病灶进一步扩大,保护缺血半影区.     

慢性阻塞性肺部病变患者肺部CT灌注成像特征

目的探讨慢性阻塞性肺疾病(COPD)患者肺部CT灌注成像的时间密度曲线(TDC)和灌注参数特征。方法共44例,分为COPD组25例及对照组19例。均行肺部多层螺旋CT(MSCT)动态增强扫描。图像经后处理,设定感兴趣区(右腹肺、右背肺和左腹肺、左背肺),得到各处肺组织TDC和灌注参数,包括灌注值(P),强化峰值增量(PEI),达峰值时间(TTP)和血容量(BV)。比较分析COPD组和对照组的TDC特征,以及各灌注参数的差异性。结果COPD组较对照组TDC波峰延后。各灌注参数腹背肺比率在2组无显著性差异(P>0.05)。COPD组TTP较对照组明显延长(P=0.010)。P、PEI和BV在2组无显著性差异(P>0.05)。结论CT灌注成像显示COPD患者肺部血流灌注异常主要表现为TDC波峰延后,TTP延长。     

颌面部肿瘤MSCT灌注成像参数与微血管密度的相关性研究

目的：评价颌面部肿瘤多层螺旋CT(MSCT)灌注成像(PI)与微血管密度(MVD)的关系。方法：对19例颌面部肿瘤行CT灌注扫描。采用免疫组化方法测定病理标本的Ⅷ因子，检测病灶的MVD，分析MSCT灌注成像参数与MVD的相关性。结果：颌面部肿瘤的微血管密度增高，且与肿瘤恶性程度明显相关。CTPI灌注参数中灌注量(Perfusion)、峰值时间(TTP)及灌注曲线类型与MVD明显相关，而增强峰值(PEI)及血流容积(BV)则相关不明显。结论：MSCT灌注成像能反映肿瘤内微血管密度，有助于对颌面部肿瘤血管密度及其预后进行评价。     

CT脑灌注与血管造影在急性脑梗死中的临床应用

目的:探讨64层螺旋CT脑灌注成像和脑血管造影技术在急性期脑梗死中的应用价值。方法:应用PhilipsBrilliance CT 64,对30例发病12h内急性脑缺血患者行CT平扫、CT脑灌注成像(CTP)和CT血管造影(CTA)检查。分析平扫及灌注成像表现,计算出缺血区脑血流参数,包括:脑血容量图(CBV)、血流量图(CBF)、对比剂平均通过时间(MTT)和对比剂峰值时间(TTP),与对侧相应区灌注参数进行比较,并重建颈段和脑内动脉CTA图像。所有病例在发病后3~14天复查CT平扫。结果:30例患者中16例头颅平扫发现早期脑梗死征象,14例常规平扫未发现异常,而CTP均发现灌注异常区。CTP表现为CBF及CBV减低、MTT及TTP延迟;患侧CBF、MTT、TTP与对侧差异有显著性意义(P<0.01),患侧CBV与对侧差异无显著性意义(P>0.01)。重建CTA图像显示16例一侧颈内动脉狭窄,8例一侧大脑中动脉狭窄(其中1例伴大脑后动脉狭窄、左侧后交通动脉闭塞);4例左侧大脑中动脉闭塞,2例左侧颈内动脉闭塞。结论:CTP能够早期、及时、准确地反映缺血部位及程度,预测半暗带;CTA可以显示病变血管的部位和程度;联合应用两者,对早期诊断急性脑缺血和指导治疗有重要价值。     

超早期脑梗死CT灌注表现的实验性研究

目的 :研究兔的脑梗死模型在缺血后 6h内各时间段CT灌注影像表现。方法 :健康成年新西兰白兔 42只 ,采用改良O′Brein法制作局灶性脑缺血模型 ,于术后 0 .5、1、2、3、4、6h不同时间段进行CT灌注扫描 ,图像用PerfusionCT/VA 10B软件处理。测量并计算缺血区的相对面积。在各时间段取兔脑组织切片 ,进行红四氮唑 (TTC)染色比较。结果 :①从缺血 0 .5h开始 ,CT灌注血流功能图上可见“斑状”分布缺血灶 ,缺血中心区在各功能图上的表现比较一致 ,缺血边缘区改变在TP图上最明显 ,侧支循环区改变只表现在TS、TP图。② 0 .5、1h时间段兔脑TTC染色未见明显改变 ,4～6h可见缺血区从基底节向颞叶皮层发展。结论 :CT灌注成像与TTC染色表现一致 ,能够在早期反应缺血灶的变化 ,是超早期脑梗死比较敏感、稳定、快速的诊断技术。     

超顺磁性氧化铁灌注T_2WI诊断超急性脑缺血的实验研究

目的观察国产超顺磁性氧化铁（ＳＰＩＯ）灌注Ｔ２ＷＩ诊断超急性期脑缺血的可行性。方法正常大鼠５只和右侧大脑中动脉闭塞（ＭＣＡＯ）大鼠２６只,行ＳＰＩＯ灌注前后Ｔ２ＷＩ,后者在ＭＣＡＯ后４０～５０分钟行ＭＲ检查。ＭＲ检查后４只行墨汁灌注检查,６只在ＭＣＡＯ后２４小时行ＭＲ复查和病理检查。ＳＰＩＯＩ颗粒直径２０ｎｍ、ＳＰＩＯＩ颗粒直径６～９ｎｍ,剂量为０６ｍｍｏｌ／ｋｇ。采用ＳＰＩＯＩ做了６只、ＳＰＩＯＩ做了２０只灌注检查。结果在ＭＣＡＯ后５０分钟,平扫Ｔ２ＷＩ仅３７％表现右侧大脑中动脉（ＭＣＡ）供血区信号稍高;两种型号的ＳＰＩＯ灌注后１００％或８０％的右侧ＭＣＡ供血区呈相对高信号,与墨汁灌注检查的灌注缺损区及ＭＣＡＯ后２４小时复查Ｔ２ＷＩ的高信号范围一致。病理检查证实右侧ＭＣＡ供血区的缺血、梗死。在剂量相同情况下,ＳＰＩＯＩ灌注Ｔ２ＷＩ显示缺血区与非缺血区的对比度明显高于ＳＰＩＯＩ。结论ＳＰＩＯ相当于一种阴性造影剂,国产ＳＰＩＯ“灌注”常规Ｔ２ＷＩ可以诊断血管闭塞５０分钟的急性脑缺血,ＳＰＩＯＩ灌注的诊断效果优于ＳＰＩＯＩ。     

Outcome of acute ischemic lesions evaluated by diffusion and perfusion MR imaging.

BACKGROUND AND PURPOSE: Diffusion and perfusion MR imaging have been reported to be valuable in the diagnosis of acute ischemia. Our purpose was to ascertain the value of these techniques in the prediction of ischemic injury and estimation of infarction size, as determined on follow-up examinations. METHODS: We studied 18 patients with acute ischemic stroke who underwent echo-planar perfusion and diffusion imaging within 72 hours of symptom onset. Quantitative volume measurements of ischemic lesions were derived from relative mean transit time (rMTT) maps, relative cerebral blood volume (rCBV) maps, and/or apparent diffusion coefficient (ADC) maps. Follow-up examinations were performed to verify clinical suspicion of infarction and to calculate the true infarction size. RESULTS: Twenty-five ischemic lesions were detected during the acute phase, and 14 of these were confirmed as infarcts on follow-up images. Both ADC and rMTT maps had a higher sensitivity (86%) than the rCBV map (79%), and the rCBV map had the highest specificity (91%) for detection of infarction as judged on follow-up images. The rMTT and ADC maps tended to overestimate infarction size (by 282% and 182%, respectively), whereas the rCBV map appeared to be more precise (117%). Significant differences were found between ADC and rMTT maps, and between rCBV and rMTT maps. CONCLUSION: Our data indicate that all three techniques are sensitive in detecting early ischemic injury within 72 hours of symptom onset but tend to overestimate the true infarction size. The best methods for detecting ischemic injury and for estimating infarction size appear to be the ADC map and the rCBV map, respectively, and the diffusion abnormality may indicate early changes of both reversible and irreversible ischemia.     

中华小型猪急性心肌缺血的综合影像学研究

目的 研究MSCT、MRI、SPECT对中华小型试验猪急性心肌缺血模型的显示效果.方法 中华小型猪共6只,所有试验猪接受MSCT扫描1次后结扎前降支中远段,在结扎后2、4、6、8 h内,每2 h MSGT扫描1次.术后24 h内进行MR、SPECT及再次完成MSCT扫描各1次,最后处死动物行病理检查.使用重复测量因素的方差分析,比较左心室前壁首过灌注减低区域与左心室侧壁首过灌注无减低区域的首过灌注CT值从术前至术后2、4、6、8、24 h的变化;使用单因素方差分析检验术前及术后2、4、6、8、24 h的心功能变化;使用配对t检验分析比较氯化三苯基四氮唑(TTC)染色病理、MSCT、MRI相互间测量梗死面积的百分比.结果 术中死亡动物1只,完成检查5只.术后2、4、6、8及24 h的MSCT动脉期减低区域,术后24 h SPECT显示的灌注减低区域,MRI显示的首过灌注减低区,病理显示的心肌梗死大致范围均位于左心室前壁.3只试验猪4～8 h的MSCT延迟扫描出现灌注减低区域边缘强化.动脉期灌注减低区域的术前与术后各时间段的CT值分别为75.9、36.4、35.2、37.8、37.4、33.3 HU,差异均有统计学意义(F=12.341,P＜0.01),术后各时间段间的CT值差异没有统计学意义(F=2.278,P=0.792).术前及术后2、4、6、8、24 h的每搏输出量(SV)平均容积分别为21.7、11.9、10.3、11.4、12.3、12.6 ml(F=22.349,P＜0.01);收缩末期(ESV)平均容积分别为15.2、23.4、25.0、24.4、25.3、22.8ml(F=8.810,P＜0.01);舒张末期(EDV)平均容积分别为37.0、35.4、35.0、35.7、37.6、37.5 ml(F=2.339,P=0.079);射血分数(EF)平均依次为58.9%、33.8%、29.0%、31.9%、32.6%、33.5%(F=27.240,P＜0.01),除EDV外差异均有统计学意义.5只猪测得的梗死面积占所测层面整个心肌比例分别为MSCT(39.4±12.6)%、MRI(37.2±10.0)%,TTC(35.9±9.6)%.TTC与MSCT(t=0.612,P=0.574)、TTC与MRI(t=0.820,P=0.458)、MSCT与MRI(t=0.425,P=0.692)间差异均无统计学意义.结论 MSCT动脉期、MRI首过灌注、SPECT显示梗死区域与TTC染色梗死部位均位于左心室前壁.MSCT动脉期与MRI首过灌注显示的低灌注面积与TTC染色梗死面积有很好的相关性.急性心肌缺血后24 h内缺血心肌密度、心功能没有随时间发生变化.     

Multiphasic perfusion computed tomography in hyperacute ischemic stroke: comparison with diffusion and perfusion magnetic resonance imaging

PURPOSE: The purpose of this study was to compare multiphasic perfusion computed tomography (CT) with diffusion and perfusion magnetic resonance imaging (MRI) in predicting final infarct volume, infarct growth, and clinical severity in patients with hyperacute ischemia untreated by thrombolytic therapy. METHOD: Multiphasic perfusion CT was performed in 19 patients with ischemic stroke within 6 hours of symptom onset. Two CT maps of peak and total perfusion were generated from CT data. Diffusion-weighted imaging (DWI) and perfusion MRI were obtained within 150 minutes after CT. Lesion volumes on CT and MRI were compared with final infarct volume and clinical scores, and mismatch on CT or MRI was compared with infarct growth. RESULTS: The lesion volume on the CT total perfusion map strongly correlated with MRI relative cerebral blood volume (rCBV), and that on the CT peak perfusion map strongly correlated with MRI relative cerebral blood flow (rCBF) and rCBV (P < 0.001). The lesion volume on unenhanced CT or DWI moderately correlated with final infarct volume, but only lesion volume on unenhanced CT weakly correlated with baseline clinical scores (P = 0.024). The lesion volumes on the CT peak perfusion map and MRI rCBF similarly correlated with final infarct volume and clinical scores and more strongly than those on mean transit time (MTT) or time to peak (TTP). DWI-rCBF or CT mismatch was more predictive of infarct growth than DWI-MTT or DWI-TTP mismatch. CONCLUSION: Multiphasic perfusion CT is useful and of comparable utility to diffusion and perfusion MRI for predicting final infarct volume, infarct growth, and clinical severity in acute ischemic stroke.     

放射性肺炎CT灌注成像的临床研究

目的 采用CT灌注成像(CTPI)技术,探求放射性肺炎(RP)形成的CTPI特点,为预测RP提供依据。方法 对37例胸部肿瘤患者照射前后不同时期行64排螺旋CT灌注成像扫描,得到肺组织感兴趣区(ROI)内各灌注参数值,即血流量(BF)、血容量(BV)、峰值时间(TTP)、表面通透性(PS)、平均通过时间(MTT),进而计算出各灌注参数相对值(rBF、rBV、rTTP、rPS、rMTT)。结果 放疗前,肺癌及其他胸部肿瘤患者的非瘤周肺组织灌注值BF、BV、TTP及MTT均无差异,与性别无关(t值分别为0.643、1.541、0.470及1.199,P>0.05),与左右肺也无关(t值分别为0.857、0.346、0.470及1.656,P>0.05);放疗后,rBF、rBV、rPS均上升者(F值分别为5.552、8.495及14.951,P均<0.05)将发生RP,仅rBF上升者(F=9.146,P<0.05)不发生RP。结论 CTPI可用于肺组织灌注的研究,能反映照射后肺组织灌注的变化规律;rBF、rBV、rPS是预测RP的关键参数。     

兔VX2软组织肿瘤MSCT灌注成像与病理对照研究

目的对兔VX2软组织肿瘤进行MSCT灌注成像与病理对照研究,探讨MSCT灌注成像在软组织肿瘤中的应用价值。材料与方法8只新西兰大白兔,双侧大腿近段注射VX2肿瘤组织悬液0．1ml,分别于肿瘤组织接种后第14、21d行CT平扫和灌注扫描,扫描图像经AW4．0工作站处理,计算并分析灌注图像和灌注参数,包括血流量(BF)、血容量(BV)、平均通过时间(MTT)和表面通透性(PS)。随后处死荷瘤兔,取出肿瘤行病理组织学检查,对其微血管密度(micro vascular density,MVD)进行测定,分析MSCT。功能参数图像与肿瘤MVD之间的关系。结果所有兔大腿VX2肿瘤组织BF、BV、PS值明显高于正常肌肉组织,且与肿瘤MVD呈正相关;而MTT值则明显低于正常肌肉组织,与肿瘤MVD无明显相关性。结论MSCT灌注成像是一种准确且相对简单、便捷的定量评估软组织肿瘤性病变血流灌注状态的功能成像方法。     

Dynamic perfusion CT: optimizing the temporal resolution for the calculation of perfusion CT parameters in stroke patients

PURPOSE: To assess the influence of different temporal sampling rates on the accuracy of the results from cerebral perfusion CTs in patients with an acute ischemic stroke. MATERIAL AND METHODS: Thirty consecutive patients with acute stroke symptoms received a dynamic perfusion CT (LightSpeed 16, GE). Forty millilitres of iomeprol (Imeron 400) were administered at an injection rate of 4 ml/s. After a scan delay of 7s, two adjacent 10mm slices at 80 kV and 190 mA were acquired in a cine mode technique with a cine duration of 49 s. Parametric maps for the blood flow (BF), blood volume (BV) and mean transit time (MTT) were calculated for temporal sampling intervals of 0.5, 1, 2, 3 and 4s using GE's Perfusion 3 software package. In addition to the quantitative ROI data analysis, a visual perfusion map analysis was performed. RESULTS: The perfusion analysis proved to be technically feasible with all patients. The calculated perfusion values revealed significant differences with regard to the BF, BV and MTT, depending on the employed temporal resolution. The perfusion contrast between ischemic lesions and healthy brain tissue decreased continuously at the lower temporal resolutions. The visual analysis revealed that ischemic lesions were best depicted with sampling intervals of 0.5 and 1s. CONCLUSION: We recommend a temporal scan resolution of two images per second for the best detection and depiction of ischemic areas.     

Functional CT perfusion imaging in predicting the extent of cerebral infarction from a 3-hour middle cerebral arterial occlusion in a primate stroke model

BACKGROUND AND PURPOSE: Our purpose was to determine whether cerebral perfusion functional CT (fCT), performed after endovascular middle cerebral artery (MCA) occlusion, can be used to predict final cerebral infarction extent in a primate model. METHODS: fCT with bolus tracking was performed before and 30 and 150 minutes after 3-hour digital subtraction angiography (DSA)-guided endovascular MCA occlusion in five baboons. Parametric cerebral blood flow (CBF), cerebral blood volume (CBV) and mean transit time (MTT) maps were constructed by voxel-by-voxel gamma variate fitting and used to determine lesion sizes. Animals were sacrificed 48 hours after the occlusion, and ex vivo MR imaging was performed. Lesion sizes on fCT and MR images were compared. RESULTS: Hypoperfusion was clearly identified on all images obtained after MCA occlusion. Thirty and 150 minutes after occlusion onset, respectively, mean lesion sizes were 737 mm(2) +/- 33 and 737 mm(2) +/- 44 for CBF, 722 mm(2) +/- 32 and 730 mm(2) +/- 43 for CBV, and 819 mm(2) +/- 14 and 847 mm(2) +/- 11 for MTT. Mean outcome infarct size on MR images was 733 mm(2) +/- 30. Measurements based on CBV and CBF (R(2) = 0.97 and 0.96, P <.001), but not MTT (R(2) = 0.40, P >.5), were highly correlated with final lesion size. CONCLUSION: An endovascular approach to MCA occlusion provides a minimally invasive, reproducible animal model for controlled studies of cerebral ischemia and infarction. Derived cerebral perfusion maps closely predict the 48-hour infarct size after 3-hour MCA occlusion.     

Correlation of diffusion tensor and dynamic perfusion MR imaging metrics in normal-appearing corpus callosum: support for primary hypoperfusion in multiple sclerosis

BACKGROUND AND PURPOSE: Hypoperfusion of the normal-appearing white matter in multiple sclerosis (MS) may be related to ischemia or secondary to hypometabolism from wallerian degeneration (WD). This study evaluated whether correlating perfusion and diffusion tensor imaging (DTI) metrics in normal-appearing corpus callosum could provide support for an ischemic mechanism for hypoperfusion. MATERIALS AND METHODS: Fourteen patients with relapsing-remitting MS (RRMS) and 17 control subjects underwent perfusion MR imaging and DTI. Absolute measures of cerebral blood volume (CBV), cerebral blood flow (CBF), and mean transit time (MTT) were calculated. Mean diffusivity (MD) and fractional anisotropy (FA) maps were computed from DTI data. After visual coregistration of perfusion and DTI images, regions of interest were placed in the genu, central body, and splenium of normal-appearing corpus callosum. Pearson product-moment correlation coefficients were calculated using mean DTI and perfusion measures in each region. RESULTS: In the RRMS group, CBF and CBV were significantly correlated with MD in the splenium (r = 0.83 and r = 0.63, respectively; both P < .001) and in the central body (r = 0.86 and r = 0.65, respectively; both P < .001), but not in the genu (r = 0.23 and 0.25, respectively; both P is nonsignificant). No significant correlations were found between MTT and DTI measures or between FA and any perfusion measure in the RRMS group. No significant correlations between diffusion and perfusion metrics were found in control subjects. CONCLUSION: In the normal-appearing corpus callosum of patients with RRMS, decreasing perfusion is correlated with decreasing MD. These findings are more consistent with what would be expected in primary ischemia than in secondary hypoperfusion from WD.     

Significance of the perfusion-diffusion mismatch in chronic cerebral ischemia

PURPOSE: To determine whether the perfusion deficit could predict brain infarction in patients with chronic cerebral ischemia who experienced recurring episodes of neurological symptoms and showed a perfusion-diffusion mismatch on magnetic resonance (MR) images. MATERIALS AND METHODS: In 53 consecutive patients (38 males and 15 females, 62+/-13 years old) with ischemia in the middle cerebral artery (MCA) territory, lesion volumetry was performed on parametric maps of the time-to-peak, the cerebral blood volume, and diffusion-weighted (DW) images. The infarct lesions were assessed on follow-up T2-weighted (T2W) MR images after eight days. Cerebrovascular changes were determined by time-of-flight (TOF) MR angiography (MRA). Inferential and correlation statistics were used. RESULTS: Patients with chronic ischemic brain disease (N=39) who presented with a severe perfusion-diffusion mismatch in the presence of a normal cerebral blood volume had no or small brain infarctions as found on follow-up T2W images. MRA revealed widespread abnormalities of the basal cerebral arteries compatible with brain perfusion abnormalities. In contrast, in acute stroke patients (N=14) the deficit of cerebral perfusion predicted the infarct lesion in the T2W images. CONCLUSION: Our results suggest that in chronic cerebral ischemia the normal blood volume was maintained despite the depression of cerebral perfusion and recurring minor insults.