老年缺血性心脑血管疾病患者心脑血流与认知功能的相关性

目的:应用单光子发射计算机断层显像(singlephotonemissioncomputertomography,SPECT)方法,了解老年冠心病和脑血管疾病合并发生的比率,分析心脑血流灌注相关性及其对认知功能的影响。方法;对68例老年缺血性心脑血管疾病患者犤男3例,女5例,平均年龄(73.95±6.31)岁犦进行了心、脑血流灌注SPECT检查,同时应用简易精神状态量表(MMSE)、中国成人智力量表(CISA)和临床记忆量表评价认知功能。结果:老年心脑血流灌注降低同时发生的比例较高,冠心病组84%,脑血管疾病组58%。相对定量分析发现心脑血流灌注水平之间未见明显相关。左室射血分数与脑血流灌注最低值正相关(r=0.335,P<0.01),而同时患有心、脑血管疾病组的患者中相关系数则更高(r=0.482,P<0.05)。认知功能尤其是记忆功能与部分脑感兴趣区如扣带回、左丘脑、右顶叶灌注呈正相关关系(r=0.396～0.789,P<0.05)。扣带回血流灌注与多项认知功能成绩呈明显正相关(r=0.400～0.807,P<0.05),在脑血管疾病组中更为明显(r=0.402～0.589,P<0.05)。心肌血流灌注与认知功能并无明显相关,而左室射血分数与认知功能尤其是记忆能力呈正相关(r=0.411～0.759,P<0.05),冠心病组较脑血管疾病更为密切。结论:老年心、脑缺血性疾病同时存在比率大。心功能的下降、脑血流灌注的降     

动脉自旋标记磁共振灌注技术在脑血管病中的应用进展

动脉自旋标记(arterial spin labeling,ASL)技术是利用自身动脉血内可自由弥散的水质子作为内源性示踪剂来完成脑灌注评价的一种功能磁共振成像(magnetic resonance imaging,MRI)技术。在短暂性脑缺血发作中,ASL可以敏感地发现脑灌注的异常;在急性脑梗死中,ASL技术可以用来评估缺血半暗带、识别供血动脉闭塞、发现梗死灶周围的高灌注以及评估侧支循环;在慢性脑血管病中,多期ASL技术可以较准确地评估脑血流量、双期ASL技术可以定量评估侧支循环,另外,ASL还可用来评估脑血流储备;在烟雾病中,ASL技术可以评估烟雾病术前和术后的灌注情况以及侧支循环;在脑小血管病、脑血管畸形及可逆性后部脑病中,ASL也有一定的应用。最后介绍了ASL技术的局限性及未来的发展前景。     

脑血管储备功能的检测方法及意义

<正>脑血管储备(cerebrovascular reserve,CVR)是指在生理或病理刺激作用下,远端脑动脉的代偿性扩张或收缩使脑血流维持正常的能力[1]。评价脑血管储备状态对于早期诊断脑血管病、制定治疗方案、预测疾病预后及评估治疗效果有重要的价值。1脑血管储备的产生机制根据脑血管储备机制的不同,脑缺血后的代偿过程可以分为4期:脑侧支循环储备期、脑血流储备期、脑代谢储备期、脑梗死期[2]。在脑长期低灌注早期,侧支循环     

糖尿病患者及糖尿病大鼠脑血流灌注的临床特点

目的　观察 2型糖尿病 (2DM )病人 ,及 2DM伴高血压病人脑血流的灌注特点。方法　用 99mTc ECD对 71例临床诊断为 2型糖尿病的患者进行脑SPECT显像。同时观察糖尿病大鼠脑血流的变化 ,并用APP17肽加以干涉。结果　 2型糖尿病患者的大脑颞叶、额叶皮层出现不同程度的放射性稀疏区及缺损区 ,糖尿病伴高血压患者更为明显。糖尿病大鼠颞叶、顶叶血流灌注减少 ,而用APP17肽干涉的糖尿病大鼠脑血流灌注有所改善。结论　在老年 2DM病人中 ,尽管尚未出现脑出血及脑血栓等脑血管疾病 ,但已有脑血流灌注减少 ,脑SPECT的检查对糖尿病和高血压的防治起到了敲响警钟的作用。动物实验结果提示APP17肽对糖尿病大鼠脑血流灌注有防护作用。     

老年缺血性心脑血管疾病患者心脑血流与认知功能的相关性

目的：应用单光子发射计算机断层显像(single photon emission computer tomography，SPECT)方法，了解老年冠心病和脑血管疾病合并发生的比率，分析心脑血流灌注相关性及其对认知功能的影响。方法：对68例老年缺血性心脑血管疾病患者[男3例，女5例，平均年龄(73．95&;#177;6．31)岁]进行了心、脑血流灌注SPECT检查，同时应用简易精神状态量表(MMSE)、中国成人智力量表(CISA)和临床记忆量表评价认知功能。结果：老年心脑血流灌注降低同时发生的比例较高，冠心病组84％，脑血管疾病组58%。相对定量分析发现心脑血流灌注水平之间未见明显相关。左室射血分数与脑血流灌注最低值正相关(r=0．335，P&;lt;0．01)，而同时患有心、脑血管疾病组的患者中相关系数则更高(r=0．482，P&;lt;0．05)。认知功能尤其是记忆功能与部分脑感兴趣区如扣带回、左丘脑、右顶叶灌注呈正相关关系(r=0．396～0．789，P&;lt;0．05)。扣带回血流灌注与多项认知功能成绩呈明显正相关(r=0．400～0．807，P&;lt;0．05)，在脑血管疾病组中更为明显(r=0．402～0．589，P&;lt;0．05)。心肌血流灌注与认知功能并无明显相关，而左室射血分数与认知功能尤其是记忆能力呈正相关(r=0．411～0．759，P&;lt;0．05)，冠心病组较脑血管疾病更为密切。结论：老年心、脑缺血性疾病同时存在比率大。心功能的下降、脑血流灌注的降低对老年缺血性心脑血管疾病患者的认知功能影响甚大；SPECT技术可用于老年缺血性心脑血管疾病患者认知功能评估的依据之一。     

缺血性脑血管疾病早期脑血流量和葡萄糖利用之间的关系

目的：通过比较脑血流灌注和脑葡萄糖代谢显像,观察在缺血性脑血管疾病中缺血程度与该部位葡萄糖代谢之间的关系。方法：对46例患有不同程度大脑中动脉狭窄的病人及15例正常对照组进行99Tcm-乙撑双半胱胺酸二乙酯（99Tcm-ECD）灌注显像和氟-18-脱氧葡萄糖（18F-FDG）细胞代谢符合线路显像进行比较分析。结果：病变部位呈现脑血流灌注减低而脑葡萄糖代谢增高的不匹配,差异有显著性（P〈0.05）。结论：缺血性脑血管病早期缺血部位血流灌注减低而葡萄糖摄取增高,并不代表神经元对葡萄糖的利用增高。     

单光子发射型计算机断层显像与脑CT及MRI对持续植物状态患者脑血流灌注的观察

目的观察持续植物状态(persistent vegetative state,PVS)患者脑血流灌注情况,并以此判断高压氧综合治疗的效果分析.方法采用99Tcm-双半胱乙酰(99Tcm-ECD)单光子发射型计算机断层(simple porton emission computertomograph,SPECT)显像方法对26例不同病因所致的PVS患者进行了观察,9例随访60 d至3年,其中17例行脑CT,14例行脑MRI检查.结果26例PVS患者脑血流灌注全部显示异常,9例PVS患者显示部位与脑CT或MRI相符,9例不符.9例随访观察SPECT显示,6例随病情恢复,脑血流灌注亦恢复正常,另3例中,2例患者无明显变化,仍处于PVS,1例患者血流灌注进一步减少,3年后死亡.结论99Tcm-ECD脑SPECT显像检查安全可靠,可明确反映PVS患者脑血流灌注情况,弥补脑CT或MRI之不足,并可作为高压氧综合治疗PVS观察预后的指标.     

101例脑血管疾病患者脑血流灌注显像分析

对101例脑血管疾病患者~(99m)TcECD SPECT脑血流灌注显像结果进行分析并与X—CT显像进行比较。101例中,男83例,女18例。脑梗塞69例,脑出血18例,TIA6例,椎动脉供血不足8例。其中78例有X—CT显像结果。结果:脑血流灌注显像阳性率88％,其中脑梗塞94％,脑出血94％,TIA50％,椎动脉供血不足50％。脑血流灌注显像异常表现呈多样性。有缺血灶病例占37％,灌注减少82％,过度灌注30％,15％的病例出现CCD现象。X—CT显像阳性率78％,同样的病例脑血流灌注显像阳性达94％。结论:SPECT脑血流显像对脑血管疾病脑血流的研究有较大价值,其各种显像异常表现的临床价值有待深入研究。     

单光子发射型计算机断层显像与脑CT及MRI对持续植物状态患者脑血流灌注的观察

目的：观察持续植物状态(persistent vegetative state，PVS)患者脑血流灌注情况，并以此判断高压氧综合治疗的效果分析。方法：采用^99Tc^m-双半胱乙酰(^99Tc^m-ECD)单光子发射型计算机断层(simple porton emission computer tomograph，SPECT)显像方法对26例不同病因所致的PVS患者进行了观察，9例随访60d至3年，其中17例行脑CT。14例行脑MRI检查。结果：26例PVS患者脑血流灌注全部显示异常，9例PVS患者显示部位与脑CT或MRI相符，9例不符。9例随访观察SPECT显示，6例随病情恢复，脑血流灌注亦恢复正常，另3例中，2例患者无明显变化。仍处于PVS，1例患者血流灌注进一步减少，3年后死亡。结论：^99Tc^m-ECD脑SPECT显像检查安全可靠，可明确反映PVS患者脑血流灌注情况，弥补脑CT或MRI之不足，并可作为高压氧综合治疗PVS观察预后的指标。     

孤独症患儿局部脑血流灌注变化研究

目的评估孤独症患儿局部脑血流灌注的变化状况。方法对17例孤独症患儿与26例排除各种神经、精神疾病,头部CT或MRI检查均无异常的其它疾病患儿分别采用双探头单光子发射型计算机断层摄影仪和99mTc—ECD显像剂对两组进行局部脑血流灌注显像,以半定量方法分析脑内局部血流量的变化。结果孤独症患儿颞叶、尾状核、壳核、丘脑下部、海马、枕叶的血流量均存在不同程度的下降,与其它疾病患儿比较存在显著性差异（P〈0．05）。结论99mTc—ECD显像剂脑血流灌注显像对儿童孤独症的诊断和治疗有一定的帮助。     

新型乏氧显像剂99Tcm-HL91在缺血性 脑血管病中的试验研究

目的：探讨新型乏氧显像剂^99Tc^m-HL91在缺血性脑血管病中的临床应用价值。方法：对18例临床确诊为缺血性脑血管病患者进行脑乏氧断层显像，其中临床诊断脑梗死11例，短暂性脑缺血发作（TIA）5例，椎-基底动脉供血不足2例，取标记好的^99Tc^m-HL91 555-1110MBq静脉推注，20-30min内行脑乏氧断层显像，17例患者同时进行了CT或MRI检查，11例患者次日行^99Tc^m-ECD脑灌注断层显像，三种方法进行了对比研究。结果：18例患者中脑乏氧显像阳性者5例，分别为脑梗死4例，椎-基底动脉供血不足1例。11例同时行^99Tc^m-ECD脑血流灌注显像者中6例表现为局部脑血流灌注减低，CT或MRI检查异常者9例。结论：^99Tc^m-HL91脑乏氧显像诊断缺血性脑血管病的影响因素较多，但对脑血流灌注显像出现低灌注区时可以区分组织乏氧或坏死，对指导治疗有一定临床意义。     

核素显像及磁共振灌注成像在诊断缺血性脑血管病中的对比研究

目的比较脑葡萄糖代谢显像、脑血流灌注显像及磁共振灌注成像三种检查方法在诊断缺血性脑血管病中的价值。方法对78例缺血性脑血管病患者和26例单侧脑血管病变患者的脑葡萄糖代谢显像、脑血流灌注显像及磁共振灌注成像进行对比分析。结果所有患者用脑葡萄糖代谢显像、脑血流灌注显像及磁共振灌注成像三种检查方法检出的阳性率分别为97.44%、94.87%和82.05%,脑葡萄糖代谢显像、脑血流灌注显像与灌注加权磁共振成像结果比较均有显著性差异(P值分别为0.012、0.002)。26例单侧血管病变患者用三种检查方法检出的阳性率分别为96.15%、92.31%、92.31%,三者无显著性差异(P=0.552)。结论脑葡萄糖代谢显像、脑血流灌注显像对诊断缺血性脑血管病较敏感,在诊断单侧血管病变中三种检查方法均较敏感。     

Cerebral microcirculation and structural changes in the brain in essential hypertension

The purpose of the study was to examine cerebral microcirculatory and structural changes in 32 patients (20 males and 12 females whose age varied from 37 to 63 years) with moderate arterial hypertension (AH). All the patients underwent single-photon emission computed tomography of the brain, using (99m)Tc-hexamethylpropyleneaminoxylfor the evaluation of perfusion, as well as magnetic resonance imaging for the examination of cerebral structures. Cerebral structural changes and perfusion impairments were detected in patients with AH, even if they had no clinical signs of cerebrovascular insufficiency. Inadequate blood flow most frequently occurred in the parietal and temporal regions of the brain. There was a reduction in the cerebrovascular reserve in the frontal lobes in AH.     

Effects of positive end-expiratory pressure on regional cerebral blood flow, intracranial pressure, and brain tissue oxygenation

OBJECTIVE: Acute respiratory dysfunction frequently occurs following severe aneurysmal subarachnoid hemorrhage requiring positive end-expiratory pressure (PEEP) ventilation to maintain adequate oxygenation. High PEEP levels, however, may negatively affect cerebral perfusion. The goal of this study was, to examine the influence of various PEEP levels on intracranial pressure, brain tissue oxygen tension, regional cerebral blood flow, and systemic hemodynamic variables. DESIGN: Animal research and clinical intervention study. SETTING: Surgical intensive care unit of a university hospital. SUBJECTS AND PATIENTS: Experiments were carried out in five healthy pigs, followed by a clinical investigation of ten patients suffering subarachnoid hemorrhage. INTERVENTIONS: Under continuous monitoring of intracranial pressure, brain tissue oxygen tension, regional cerebral blood flow, mean arterial pressure, and cardiac output, PEEP was applied in increments of 5 cm H2O from 5 to 25 cm H2O in the experimental part and from baseline to 20 cm H2O in the clinical part. MEASUREMENTS AND MAIN RESULTS: In animals, high PEEP levels had no adverse effect on intracranial pressure, brain tissue oxygen tension, or regional cerebral blood flow. In patients with severe subarachnoid hemorrhage, stepwise elevation of PEEP resulted in a significant decrease of mean arterial pressure and regional cerebral blood flow. Analyses of covariance revealed that these changes of regional cerebral blood flow depended on mean arterial pressure changes as a result of a disturbed cerebrovascular autoregulation. Consequently, normalization of mean arterial pressure restored regional cerebral blood flow to baseline values. CONCLUSIONS: Application of high PEEP does not impair intracranial pressure or regional cerebral blood flow per se but may indirectly affect cerebral perfusion via its negative effect on macrohemodynamic variables in case of a disturbed cerebrovascular autoregulation. Therefore, following severe subarachnoid hemorrhage, a PEEP-induced decrease of mean arterial pressure should be reversed to maintain cerebral perfusion.     

Quantitative cerebral perfusion MRI and CO2 reactivity measurements in patients with symptomatic internal carotid artery occlusion

Quantitative perfusion MRI is a promising new technique capable of offering information on cerebral blood flow (CBF), cerebral blood volume (CBV), and mean transit time (MTT). However, it is still unclear how these perfusion parameters relate to the underlying physiological indicators and how they compare to conventional techniques. The purpose of this study was to investigate how quantitative perfusion MRI is related to the cerebrovascular reactivity as measured by transcranial Doppler ultrasonography (TCD) in combination with a CO2 stimulus in patients with a symptomatic occlusion of the internal carotid artery (ICA). Thirty-nine patients with transient or minor disabling retinal or hemispheric ischemic symptoms and an occlusion of the ICA underwent quantitative perfusion MRI and CO2 reactivity measurements by TCD. Perfusion parameters were correlated with cerebrovascular reactivity measurements and compared with measurements of control subjects. The results of this study show a negative correlation between the cerebrovascular reactivity and the time to bolus peak (TBP) both for gray (r = -0.26, P = 0.035) and white matter (r = -0.28, P = 0.026). No correlation between resting CBV, CBF, or MTT and cerebrovascular reactivity was found. Our results indicate that an increase in TBP reflects a poor development of collateral flow, which is supported by a relatively low CO2 reactivity in these patients.     

Association between supine cerebral perfusion and symptomatic orthostatic hypotension

The goal of this study was to investigate whether the supine resting perfusion of brain tissue in symptomatic patients suffering from orthostatic hypotension (OH) is changed compared to control subjects and whether an association exists between the resting perfusion and the severity of OH. Ten symptomatic OH patients and 8 control subjects were included in this study. One patient was retrospectively excluded because he suffered from multiple system atrophy. Systolic and diastolic blood pressure changes were measured during a tilting bed procedure. Cerebral blood flow, cerebral blood volume and mean transit time were determined by bolus-tracking perfusion MRI and correlated with blood pressure changes. Cerebral blood volume was significantly increased in OH patients compared with control subjects for white matter (P = 0.019) and the mean transit time was significantly increased for gray (P = 0.010) and white matter (P = 0.015). The cerebral blood flow of the gray (r = 0.74, P = 0.022) and white matter (r = 0.75, P = 0.020) was significantly, positively correlated with systolic blood pressure changes. The mean transit time in white matter was significantly, negatively correlated with systolic blood pressure changes (r = -0.68, P = 0.045). This study suggests that in symptomatic patients with OH the cerebral perfusion of the brain in the resting, supine position correlates with the severity of OH as measured by postural changes in blood pressure.     

Quantitative measurement of cerebral physiology using respiratory-calibrated MRI

Functional magnetic resonance imaging typically measures signal increases arising from changes in the transverse relaxation rate over small regions of the brain and associates these with local changes in cerebral blood flow, blood volume and oxygen metabolism. Recent developments in pulse sequences and image analysis methods have improved the specificity of the measurements by focussing on changes in blood flow or changes in blood volume alone. However, FMRI is still unable to match the physiological information obtainable from positron emission tomography (PET), which is capable of quantitative measurements of blood flow and volume, and can indirectly measure resting metabolism. The disadvantages of PET are its cost, its availability, its poor spatial resolution and its use of ionising radiation. The MRI techniques introduced here address some of these limitations and provide physiological data comparable with PET measurements. We present an 18-minute MRI protocol that produces multi-slice whole-brain coverage and yields quantitative images of resting cerebral blood flow, cerebral blood volume, oxygen extraction fraction, CMRO(2), arterial arrival time and cerebrovascular reactivity of the human brain in the absence of any specific functional task. The technique uses a combined hyperoxia and hypercapnia paradigm with a modified arterial spin labelling sequence.     

Cerebrovascular regulation and vasoneuronal coupling

Maintenance of cerebral perfusion pressure is a prerequisite for the prevention of cerebral ischemia. Physiological fluctuations in systemic perfusion pressure are compensated by cerebrovascular autoregulation. Cerebral hypoperfusion could result from (1) systemic hemodynamic failure (eg, distal to severe arterial stenosis), overcharging the vasoregulatory capacity; (2) dysfunction and exhaustion of cerebrovascular autoregulation; or (3) both. Ultrasound offers an excellent temporal resolution, is noninvasive, and is easily applicable for follow-up investigations. Despite its poor spatial resolution, transcranial Doppler sonography has been used for determination of cerebral perfusion reserve studies measuring cerebral blood flow velocity (CBFV) during hypercapnia or application of vasoactive agents (eg, acetazolamide). This approach evaluates vasomotor regulation in patients with hemodynamic compromise distal to severe stenosis or occlusion of the brain supplying arteries. Monitoring CBFV during tilt table examinations directly measures cerebral autoregulation. In patients with systemic orthostatic hypotension, maintainance or failure of cerebrovascular compensation and, even more importantly, cerebrovascular dysautoregulation, despite normal systemic blood pressure regulation, may be demonstrated. Vasoneuronal coupling is reflected by CBFV variations during appropriate neuronal stimulation. Neuronal dysfunction is associated with CBFV abnormalities as exemplified by preconditions of focal cerebral dysfunction in the posterior cerebral artery (PCA) in migraineurs with aura, where massive alteration of vasoneuronal coupling and ischemia is threatening during spreading depression. A highly significant asymmetric gain of vasoneuronal coupling in the interictal state may act as a trigger mechanism in these patients. Testing for vasoneuronal coupling within the middle cerebral artery (MCA) territory is more difficult due to the poor spatial resolution with various neuronal stimuli (eg, motorsensory or cognitive paradigms), only eliciting local neuronal areas underrepresented in the MCA CBFV global changes. However, motor stimulation evoked CBFV may be used to indicate dysintegation of vasoneuronal coupling in the course of acute cerebral ischemia with sensorimotor hemiparesis and, moreover, seems to be of prognostic value regarding the motor deficit. © 1995 John Wiley & Sons, Inc.     

Characterization of cerebrovascular responses to hyperoxia and hypercapnia using MRI in rat

Understanding cerebrovascular responses to hyperoxia and hypercapnia is important for investigating exogenous regulation of cerebral hemodynamics. We characterized gas-induced vascular changes in the brains of anesthetized healthy rats using magnetic resonance imaging (MRI) while the rats inhaled 100% O₂ (hyperoxia) and 5% CO₂ (hypercapnia). We used echo planar imaging (EPI), arterial spin labeling (ASL), and intravascular superparamagnetic iron oxide nanoparticles (SPION) to quantify vascular responses as measured by blood oxygenation level dependence (BOLD), cerebral blood flow (CBF), cerebral blood volume (CBV), microvascular volume (MVV), and vessel size index (VSI) in multiple brain regions. Hyperoxia resulted in a statistically significant increase in BOLD-weighted MRI signal and significant decrease in CBF and CBV (P < 0.05). During hypercapnia, we observed significant increases in BOLD signal, CBF, MVV, and CBV (P < 0.05). Despite the regional variability, general trends of vasoconstriction and vasodilation were reflected in VSI changes during O₂ and CO₂ challenges. Interestingly, there was an evident spatial disparity between the O₂ and CO₂ stimuli-induced functional activation maps; that is, cortical and subcortical regions of the brain exhibited notable differences in response to the two gases. Hemodynamic parameters measured in the cortical regions showed greater reactivity to CO₂, whereas these same parameters measured in subcortical regions showed greater responsivity to O₂. Our results demonstrate significant changes of hemodynamic MRI parameters during systemic hypercapnia and hyperoxia in normal cerebral tissue. These gas-dependent changes are spatiotemporally distinctive, suggesting important feasibility for exogenously controlling local cerebral perfusion.