兔大脑中动脉阻塞模型局灶性脑缺血区超早期水分子扩散异常？…

目的 观察兔大脑中动脉阻塞（ＭＣＡＯ）缺血模型的早期ＭＲ表现与演变规律;明确脑缺血区超早期水分子扩散异常的病理基础以及扩散加权像（ＤＷＩ）超早期显示局灶脑缺血范围上的意义。方法 新西兰大白兔４５只经左眶入路大脑中动脉结扎后,行ＭＲ检查,包括ＤＷＩ、常规Ｔ１ＷＩ、Ｔ２ＷＩ,观察异常信号的出现时间,异常信号的范围,并计算扩散异常区的扩散速率变化,取不同的时间点（０．５￣３６小时）进行病理检查与红四氮唑     

急性大脑中动脉阻塞模型的磁共振弥散成像及相关病理基础研究

目的观察兔大脑中动脉阻塞后常规MRI及DWI表现,阐明活体脑缺血后DWI的演变规律及其病理生理机制方法40只成年新西兰大白兔随机分成2组,对照组4只,实验组36只实验组采用Yamamoto法制作急性大脑中动脉阻塞(MCAO)模型,对照组仅曝露大脑中动脉,而不结扎观察MCAO后缺血区在各时段ADC值的变化规律,并进行病理学检查结果对照组:T2WI及DWI均无高信号出现,光镜检查均无异常改变实验组:DWI上,MCAO后0.5h基底节区出现高信号;T2WI最早于2h出现高信号,早期ADC值快速下降的病理基础是缺血后细胞内的水含量的增加;ADC值下降减慢及相对平台期的病理基础是血脑屏障破坏的逐渐加重及血管源性水肿的出现;而ADC值的上升的病理基础是细胞的死亡、溶解,血脑屏障的破坏结论早期的扩散异常区域并不意味着病灶已发生梗死,当持续缺血达6h以上,脑组织将产生不可逆的损伤     

兔脑缺血模型的影像学研究

目的 通过研究兔颈动脉变异情况，探讨建立良好的适应临床影像学研究需要的脑缺血动物模型，方法４６只新寺兔随机分为缺血组（４０只）和对照组（６只）。缺血组采用颈外动脉逆行置管，暂时夹闭颈决动脉，由导管内注入自体血凝块，建立脑缺血模型，对照组栓塞前手术过程与缺血组相同，缺血组在栓塞后不同时限行ＭＲＩＴ２ＷＩ检查及病理检查，结果 ４６只兔动脉变异共分为４型，Ｉ型，单纯颈内动脉型（２６条，占５７％），ＩＩ型     

MRI评价兔局灶性脑缺血再灌注模型的时间特征性研究

目的:利用MRI研究兔局灶性脑缺血再灌注模型,观察脑缺血再灌注不同时间点的动态变化规律.材料和方法:建立兔局灶性脑缺血再灌注模型,72只雄性新西兰白兔,被随机分为3组,其中A组8只,为空白对照组;B组24只,为假手术对照组;C组40只,为缺血再灌注组.采用改良颈内动脉线栓造模方法,用导丝置入颈内动脉,阻闭左侧大脑中动脉,于阻闭2h后抽出导丝,恢复再灌注,于再灌注后0h、1h、3h、6h、12h、24h、3d、7d(均n=5)对实验动物进行行为评分、M RI及形态学评价.结果:空白对照组、假手术组M RI上未见异常信号,缺血再灌注组表现在MCA供血区T2WI、DWI出现高信号,并随缺血再灌注时间有逐渐增大趋势,3d后T2WI、DWI高信号范围有所减小.TTC染色异常的部位与DWI所显示的区域一致.增强T1WI显示缺血6h内缺血半球有对比增强.结论:应用M R影像学方法可对兔局灶性脑缺血再灌注后血脑屏障的开放及脑水肿进行动态时间评价,为脑缺血的诊断和治疗奠定了基础.     

局灶性脑缺血后细胞反应性增生的MR和病理表现

目的:动态追踪局灶性脑缺血MRT2、ADC信号变化,探讨脑缺血后细胞反应性增生的影像特点.方法:线栓法阻塞大鼠左侧大脑中动脉,模型制作后6h、1d、3d、7d行俯卧位冠状面磁共振T2WI、T2 map和DWI扫描,测量ADC、T2值,取脑切片进行病理观察.结果:MR图像6h已经显示缺血灶;1d时病理表现为脑水肿、组织坏死,T2WI为高信号,ADC值降低;3d时病变组织以片状坏死为主,出现细胞增生,T2信号增高的程度较前有所降低,ADC值有所回升;反应性细胞增生于第7天更为明显,T2高信号强度进一步降低,而ADC值增高,并超过对侧.结论:脑缺血后不同MR参数时间空间变化存在一定规律,MR成像能够在一定程度上活体反映脑缺血后细胞反应性增生过程.     

早期脑缺血MR灌注成像的实验研究

目的 应用脑灌注ＭＲＩ技术研究早期脑缺血缺血血流动力学改变并探讨其临床应用价值。     

大鼠大脑中动脉局灶性脑缺血模型的时间梗死体积相关研究

采用鼠须聚乙烯醇栓线栓塞大鼠大脑中动脉,观察缺血１、１．５、２、３、４、６、９、１２及２４ｈ后２％红四氮唑（ＴＴＣ）标记的梗死体积,并与时间进行了相关分析。结果表明缺１ｈ组及９０ｍｉｎ组ＴＴＣ染色未发现梗死灶,缺血２ｈ大鼠基底节区出现梗死灶,边界欠清,４ｈ因动物梗死体积明显增大,和２、３ｈ组比较差异已有显著性意义（Ｐ〈０．０１）。各组动物随缺血时间梗死体积渐趋增大,与时间有显著相关性（ｒ＝０．８６     

急性兔脑缺血模型MR扩散张量成像的实验研究

目的探讨实验性急性兔脑缺血磁共振扩散张量成像(DTI)改变。材料与方法建立兔急性脑缺血模型,常规行T2WI、DWI、DTI检查,测量比较缺血灶和正常对照侧的平均扩散系数(ADC)值、各向异性分数(FA)值,分析彩色FA图和脑白质纤维束示踪图。结果通过比较缺血灶与正常对照侧ADC值和FA值,两者的差别有统计学意义,且病灶侧明显减低。脑白质纤维束示踪图显示病灶白质束表现为缺失、断离、稀疏,邻近白质纤维束受压。结论DTI不仅可以准确评价急性期脑缺血的灰质、白质内水分子扩散各向异性改变的特点,并且脑白质纤维束示踪图可以清楚地显示出病灶远端神经束走向改变及其完整性。本实验通过研究兔急性脑缺血模型的DTI特点,为脑缺血性疾病的研究提供了可靠的动物模型和实验理论依据。     

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。     

Apparent diffusion coefficient mapping of experimental focal cerebral ischemia using diffusion-weighted echo-planar imaging

Diffusion-weighted, echo-planar imaging (EPI) was used to map regional changes In the apparent diffusion coefficient (ADC) during experimental focal ischemia in the rat brain following permanent middle cerebral arterial occlusion (MCAO). Sixteen 64 × 64 diffusion-weighted EPIs were acquired in 32 s with successively increasing amplitudes of the diffusion-sensitive gradient pulses. A linear least-squares regression algorithm was used to fit 15 of the 16 two-dimensional matrices, on a pixel-by-pixel basis, to solve for the slope from which the ADC value was calculated. The correlation coefficient of the fit, R² was used to filter the final ADC maps, and the ADCs were then scaled appropriately to be displayed in a 256 gray level format. Ranges (bins) of 0.05 × 10⁻³ mm²/s were then grouped and color coded to qualify and quantify the evolution of ischemia in the MCA territory. The percentage of area in the ischemic and contralateral hemispheres in seven ADC bins were calculated at 30, 60, and 120 min after MCAO for 10 animals and demonstrated a significant increase in ADC bins below 0.45 × 10⁻³ mm²/s and a decrease in bins above 0.50 × 10⁻³ mm²/s over the. The postmortem infarct area, as measured by TTC staining, was highly correlated with the portion of the ischemic hemisphere falling below ADC values of 0.55 × 10⁻³ mm²/s at 2 h after stroke onset. These studies suggest that focally ischemic brain tissue can be quantitatively subdivided according to ADC values and that ADC values below 0.55 × 10⁻³ mm²/s 2 h following ischemia highly predict infarction in a rat permanent occlusion stroke model.     

Separating changes in the intra- and extracellular water apparent diffusion coefficient following focal cerebral ischemia in the rat brain.

Selective intracellular (IC) and extracellular (EC) brain water apparent diffusion coefficient (ADC) values were measured in normal and ischemic rat brain. Selective T(1)-relaxation enhancement of the EC water, using intracerebroventricular (ICV) infusion of an NMR contrast reagent (CR), was used to separate the IC and EC signal contributions. In the CR-infused, normal brain (n = 4), T(1) = 235 +/- 10 ms and T(2) = 46 +/- 2 ms for IC water (85%) and T(1) = 48 +/- 8 ms and T(2) = 6 +/- 2 ms for EC water (15%). Volume-localized ADC(z) (z-gradient axis) values were 0.90 +/- 0.02 (EC+IC), 0.81 +/- 0.05 (IC), 0.51 +/- 0.02 (EC+IC), and 0.53 +/- 0.07 (IC), for normal, CR-infused, ischemic, and ischemic/CR-infused groups, respectively (ADC values are x10(-3) mm(2)/s; n = 5 for each group). Imaging ADC(z) values were 0.81 +/- 0.03 (EC+IC), 0.75 +/- 0.05 (IC), 0.51 +/- 0.04 (EC+IC), and 0.52 +/- 0.05 (IC), respectively, for the same groups. Imaging ADC(av) (average diffusivity) values for the same groups were 0.70 +/- 0.05 (EC+IC), 0.69 +/- 0.06 (IC), 0.45 +/- 0.06 (EC+IC), and 0.44 +/- 0.06 (IC), respectively. These results suggest that the IC water ADC determines the overall water ADC value in normal and ischemic rat brain.     

急性脑缺血及再灌注磁共振扩散加权成像的特点

目的 用改良的线栓法制作大脑中动脉阻塞（ＭＣＡＯ）动物模型,探讨急性脑缺血及再灌注的磁共振扩散加权成像（ＤＷＩ）的特点。方法 １８只Ｓｐｒａｇｕｅ－Ｄａｗｌｙ大白鼠,随机分为４组：Ａ组（６只）,非再通组;Ｂ、Ｃ、Ｄ组（各４只）,分别是于ＭＣＡＯ３０分钟、１小时、２小时后再通,于不同时间点作ＤＷＩ和Ｔ２ＷＩ,通过后处理得到表观扩散系数（ＡＤＣ）像并计算感兴趣区的ＡＤＣ、相对ＡＤＣ（ｒＡＤＣ）及ＤＷＩ     

MRI of focal cerebral ischemia using (17)O-labeled water.

This work presents a novel approach for quantifying low concentrations of H(2)(17)O in vivo and explores its utility for assessing cerebral ischemia. Oxygen-17 enriched water acts as a T(2) shortening contrast agent whose effect can be suppressed by decoupling at the (17)O frequency during TE interval in a spin-echo MR image. Serial T(2)-weighted echo planar images were acquired in phantoms and rat brain with decoupler power alternated every eight images. The resulting periodic signal change (proportional to H(2)(17)O concentration) was detected by cross-correlating the square-wave decoupler power timecourse with the signal intensity in each voxel. Natural abundance (0.037 atom%) images of H(2)(17)O in rat brain were generated. The transverse relaxivity of H(2)(17)O in brain was estimated, R(2) = 2.4+/-0.5 s(-1)(atom%)(-1). After bolus injection of 1 ml of 10 atom% H(2)(17)O, brain H(2)(17)O concentration was estimated at 0.06+/-0.01 atom%. In the rat focal ischemia model, (17)O cross-correlation maps compared well with diffusion and Gd-DTPA perfusion images to indicate infarct location. Magn Reson Med 43:876-883, 2000.     

水分子扩散加权磁共振成像在肝脏的临床应用

目的　评价磁共振水分子扩散加权成像（ＤＷＩ） 在肝脏病变鉴别诊断中的价值。方法对１３ 例正常志愿者、２８ 例病人的腹部正常脏器以及３９ 例５９ 个病灶（ 肝癌７ 例１１ 个病灶,转移瘤１１例１９ 个病灶,海绵状血管瘤１３ 例１８ 个病灶,肝囊肿８ 例１１ 个病灶） 行ＤＷＩ并测量表观扩散系数（ＡＤＣ值） 。结果　正常肝、脾、肾、胆囊、胰腺及肌肉平均ＡＤＣ 值分别为０－６９ ×１０－３ ｍｍ２／ｓ、０－７１ ×１０－３ ｍｍ２／ｓ、１－６４×１０－ ３ ｍｍ２／ｓ、２－９２×１０－３ ｍｍ２／ｓ、０－８３×１０－３ ｍｍ２／ｓ、０－７３×１０－３ ｍｍ２／ｓ。肝囊肿、海绵状血管瘤、肝癌及转移瘤的平均ＡＤＣ值分别为３－０３×１０－３ ｍｍ２／ｓ、１－９１×１０－３ ｍｍ２／ｓ、０－９５ ×１０－３ ｍｍ２／ｓ、１－１８×１０－３ ｍｍ２／ｓ,囊肿、血管瘤及恶性肿瘤三者间有显著性差异（Ｐ＜０－００１）。结论　ＤＷＩ分析及ＡＤＣ值测量对肝脏局灶性病变鉴别诊断有一定价值,可作为肝脏ＭＲＩ的补充检查序列。     

arcaine 对大鼠局灶性脑缺血损伤的神经保护作用

目的 观察N-甲基-D-天冬氨酸(NMDA)受体/通道复合物多胺位点拮抗剂arcaine对脑缺血损伤的神经保护作用.方法 将45只Wistar大鼠随机分为对照组、缺血模型组、术前24h组、术前1h组及术后1h组.后4组大鼠均采用线栓法阻断大脑中动脉制作急性脑梗死模型.缺血模型组在造模成功后1h给予生理盐水(0.4ml/kg),术前24h组、术前1h组和术后1h组分别在术前24、1h和术后1h给予3mg/kg areaine.检测大鼠神经功能行为、脑梗死体积,并观察光镜及电镜下脑组织损伤情况.结果 神经功能评分显示,术前24h组、术前1h组和术后1h组大鼠神经功能行为评分(1.25±0.46、1.33±0.50、1.40±0.58分)与缺血模型组(2.63±0.52分)相比有显著差异(P<0.05),且术后给药对神经运动功能障碍的改善效果较术前给药效果差(P<0.05).术前24h、术前1h组和术后1h组大鼠脑梗死体积百分比(分别为5.72%±2.91%、26.36%±5.30%、36.35%±6.66%)较缺血模型组(51.10%±3.86%)明显减少(P<0.05);术后1h组大鼠脑梗死体积百分比较术前24、1h组增加(P<0.05).除对照组外,各组光镜下病理分级结果 差异无统计学意义.电镜下观察各组大鼠皮层及海马神经元均有不同程度的变性坏死,其中缺血模型组病理损害最为严重.结论 arcaine能够显著减少脑梗死的体积、减轻梗死所致的神经功能损伤,且预防给药效果更佳,但是arcaine对缺血所致神经元超微结构的损伤无明显逆转作用.     

经导管动脉化疗栓塞联合内皮抑素对兔VX2肝移植瘤新生血管生成的影响

目的 探讨兔VX2肝移植瘤经介入治疗联合应用内皮抑素(endostatin,ES)治疗后,残瘤组织微血管密度(micmvagcular density,MVD)和血管内皮生长因子(vascular endothelial growth factor,VEGF)的表达情况及其相关性.方法 建立兔VX2肝移植瘤模型,随机分为对照组(n=10)、经导管动脉化疗栓塞(TACE)组(碘油+阿霉素,n=10)和TACE联合抗血管生成组(碘油+阿霉素+ES,n=10),术后1周取出病理标本,用免疫组织化学染色分别检测残瘤组织VEGF和MVD的表达,3组间的比较采用方差分析.结果 对照组、TACE组和TACE联合抗血管生成组的VEGF平均吸光度值(A)分别为0.130 ±0.038、0.200±0.049和0.120±0.047(F=9.42,P＜0.01),TACE组表达水平最高,与其余两组比较差异有统计学意义(q值分别为4.93、5.63,P＜0.01),TACE联合抗血管生成组VEGF的表达水平低于对照组,但两组之间差异无统计学意义(q=0.70,P＞0.05);各组MVD值分别为(80 ±17)、(84±16)和(57±13)个/高倍镜(F=8.70,P＜0.01),TACE联合抗血管生成组MVD值最低,与其余两组比较均有统计学意义(q值分别为4.63、5.48,P＜0.01),对照组和TACE组之间差异无统计学意义(q=0.85,P＞0.05).结论 TACE联合应用内皮抑素治疗较单纯化疗栓塞可以明显降低肿瘤VEGF的表达,并可显著减少肿瘤微血管的形成,影响肿瘤的预后.     

兔骨骼肌缺血模型扩散张量成像研究

目的 初步探讨MR DTI在定量评估兔后肢缺血模型骨骼肌缺血中的应用价值.方法 对14只新西兰大白兔进行结扎并切除一侧后肢股动脉,成功建立兔后肢缺血模型共12只,分别于术后3 d(12只)、10 d(10只)、28 d(7只)、56 d(5只)对两侧小腿行DTI检查,并在每个时间点留取病理组织.观察两侧肌组织在DWI、本征向量(λ)_1图、λ_2图、λ_3图、ADC图和部分各向异性(FA)图上的表现,并测量后组肌群的λ_1、λ_2、λ_3、ADC值和FA值,采用配对t检验比较两侧小腿的差异,并与病理组织对照.结果 术后3 d手术侧ADC值升高(ADC_(术侧)=1.72±0.16,ADC_(健侧)=1.53±0.16,t=6.48,P<0.01),其中λ_2和λ_3 2个特征矢量值升高明显(入_(2术侧)=1.70±0.15,入_(2健侧)=1.51±0.06,t=10.87,P<0.01;入_(3术侧)=1.17±0.12,λ_(3健侧)=0.88±0.12,t=6.67,P<0.01),FA值急骤下降(FA_(术侧)=0.24±0.04,FA_(健侧)=0.39±0.03,t=-10.61,P<0.01);术后10 d缺血骨骼肌ADC值及λ_2、λ_3值下降,但两侧仍有差异(ADC_(术侧)=1.65±0.16,ADC_(健侧)=1.50±0.12,t=6.42,P<0.01;λ_(2术侧)=1.62±0.32,λ_(2健侧)=1.48±0.31,t=5.09,P<0.01);λ_(3术侧)=1.11±0.13,λ_(3健侧)=0.85±0.09,t=6.26,P<0.01),λ_1值恢复正常(λ_(1术侧)=2.20±0.21,λ_(1健侧)=2.18±0.20,t=0.87,P=0.40);术后28 d ADC及λ_3值恢复正常(ADC_(术侧)=1.51±0.16,ADC_(健侧)=1.55±0.14,t=-1.35,P=0.23;λ_(3术侧)=0.95±0.10,λ_(3健侧)=0.92±0.06,t=1.70,P=0.14),但λ_2及FA值仍有差异(λ_(2术侧)=1.45±0.23,λ_(2健侧)=1.52±0.95,t=-3.56,P=0.012;FA_(术侧)=0.35±0.02,FA_(健侧)=0.40±0.03,t=-3.83,P<0.01);术后56 d各观测指标均恢复正常(ADC_(术侧)=1.57±0.18,ADC_(健侧)=1.58±0.23,t=-0.71,P=0.52;λ_(1术侧)=2.18±0.18;λ_(1健侧)=2.24±0.14;t=-0.22,P=0.10;λ_(2术侧)=1.64±0.13,λ_(2健侧)=1.59±0.15,t=0.89,P=0.42;λ_(3术侧)=0.89±0.1,λ_(3健侧)=0.91±0.07,t=-1.64,P=0.18;FA_(术侧)=0.39±0.03,FA_(健侧)=0.41±0.02,t=-0.83,P=0.47).组织学观察,在缺血后3、10 d见肌肉损害,28 d后缺血肌肉逐渐恢复,56 d恢复正常形态.结论 DTI可以定量且较准确地评估动物后肢缺血模型随时间推移发生的肌肉组织损伤及修复过程.     

Early changes in water diffusion, perfusion, T1, and T2 during focal cerebral ischemia in the rat studied at 8.5 T.

The time evolution of water diffusion, perfusion, T1, and T2 is investigated at high magnetic field (8.5 T) following permanent middle cerebral artery occlusion in the rat. Cerebral blood flow maps were obtained using arterial spin tagging. Although the quantitative perfusion measurements in ischemic tissue still pose difficulties, the combined perfusion and diffusion data nevertheless distinguish between a "moderately affected area," with reduced perfusion but normal diffusion; and a "severely affected area," in which both perfusion and diffusion are significantly reduced. Two novel magnetic resonance imaging observations are reported, namely, a decrease in T2 and an increase in T1, both within the first few minutes of ischemia. The rapid initial decrease in T2 is believed to be associated with an increase in deoxyhemoglobin levels, while the initial increase in T1 may be related to several factors, such as flow effects, an alteration in tissue oxygenation, and changes in water environment.     

脑缺血再灌注神经细胞血小板活化因子受体蛋白特性研究

目的探讨大鼠局灶性脑缺血再灌注后血小板活化因子(PAF)受体特性的变化。方法建立一侧大脑中动脉线栓闭塞再通模型，超速离心制备缺血脑皮质神经细胞突触膜和微粒体。采用放射配基结合实验，检测脑缺血再灌注后PAF受体的平衡解离常数(Kd)和最大结合数量(Bmax)。结果Scatchard作图分析显示，各组样本均存在3个特异性PAF结合位点，其中2个位于微粒体，另1个在突触膜上。单纯缺血90min时，突触膜位点Kd和Bmax明显减小；再灌注1d后，微粒体上2个位点的Kd、Bmax明显下降，至7d均未恢复到假手术组水平。结论缺血再灌注可诱导脑皮质神经细胞PAF受体下调，胞内受体下调晚发于突触膜受体。