CT灌注成像评价颅骨缺损修复前后 脑血流量变化的临床研究

目的 通过CT灌注成像（CTP）观察颅骨成形术患者脑血流量的变化。方法 对20例颅骨缺损修复的患者进行脑CT灌注成像,在颅骨修复术前和术后2周进行CTP。记录大脑皮层、基底节区脑血流容量（CBV）、脑血流流量（CBF）、造影剂平均通过时间（MMT）和对比剂达到峰值的时间（TTP）等所有参数,分析脑皮层和基底节区血流灌注数据的变化。结果 颅骨修复术前患侧脑皮层区的CBV和CBF值均低于健侧,TTP和MTT值均高于健侧,差异均具有统计学意义（P＜0.05）。修复术后患侧脑皮层的CBF、CBV值均有提高,患侧脑皮层的MTT、TTP值较术前降低,差异均具有统计学意义（P＜0.05）。患侧术后脑皮层的CBV、CBF、MTT、TTP值与健侧比较无统计学意义（P＞0.05）。结论 CT灌注成像能及时发现脑血流变化情况,颅骨修复可以增加脑皮层区脑血流量,促进神经功能恢复。     

注射流率对脑磁共振灌注成像血流动力学的影响

研究不同注射速率对磁共振脑灌注测量值的影响,并探讨最佳的注射速率。60名无明确脑血管疾病志愿者按对比剂注射流率(3、4、5 m L/s)分为3组,采取MR常规扫描及灌注扫描,将原始灌注扫描数据传送到ADW4.3工作站,应用GE专用灌注软件处理得到相对脑血流量(r CBF)、相对脑血容量(r CBV)、对比剂平均通过时间(MTT)和达峰时间(TTP)函数图,测量受试者各感兴趣区(额叶白质、丘脑及小脑)的r CBV、r CBF、MTT、TTP参数值。结果表明,60名无明确脑血管疾病志愿者均符合选入标准,纳入统计。不同流率组内两侧额叶白质、丘脑及小脑的r CBF、r CBV、MTT和TTP值左右对比,无明显统计学差异(P>0.05);不同流率组间两侧额叶白质、丘脑及小脑各灌注参数比较显示:组各感兴趣区r CBF值,3 m L/s明显低于4、5 m L/s组;各感兴趣区r CBV值,3 m L/s组明显低于4、5 m L/s组;各感兴趣区MTT值,3 m L/s组较4、5 m L/s组明显延迟;以上差异均具有显著统计学差异(P<0.05)。3、4、5 m L/s三组各感兴趣区TTP值比较差异无统计学意义(P>0.05);4 m L/s组与5 m L/s组,各感兴趣区各参数值比较差异无统计学意义(P>0.05)。使用4 m L/s的注射流率时,磁共振脑灌注成像能产生较好的团注效果,可以满足诊断要求,并可降低对比剂局部外渗甚至血管壁破裂的风险;TTP值对注射流率影响脑灌注量的反应程度不及r CBV、r CBF、MTT敏感。     

表面通透性值对脑内、外肿瘤的鉴别

目的初步探讨多层螺旋CT(MSCT)灌注成像在脑内、外肿瘤鉴别诊断中的临床应用价值。方法 35例已知有脑部肿瘤患者,其中男性21例,女性14例;年龄24～83岁,平均年龄50.1岁。行16层CT灌注成像扫描,先行脑部CT平扫以确定肿瘤中心层面,然后采用CT电影扫描技术对肿瘤中心层面进行灌注扫描,扫描图像应用Perfusion2软件进行灌注成像分析。结果脑血流量(CBF)值、血容量(CBV)值脑内、外肿瘤间有交叉;脑外肿瘤的表面通透性(PS)值均大于脑内肿瘤的PS值。结论 MSCT灌注成像中PS值有助于脑内、外肿瘤的鉴别诊断。     

64排螺旋CT灌注成像联合CTA对急性缺血性脑卒中的诊断价值分析

目的探讨64排螺旋CT灌注成像(CTP)联合CT血管成像(CTA)对急性缺血性脑卒中(AIS)的诊断价值。方法选取2017年3月～2019年3月期间我院拟诊为急性缺血性脑卒中(AIS)的135例患者作为研究对象,依次进行CTP、CTA检查。记录灌注异常区及健侧相应区域(对照区)脑血容量(CBV)、脑血流量(CBF)、平均通过时间(MTT)、达峰时间(TTP)等参数,评价血管狭窄程度;以临床综合诊断和随访结果为金标准,评估CTP联合CTA诊断AIS符合率。结果梗死区和半暗带CBV、CBF均明显低于对照区,且梗死区CBV、CBF显著低于半暗带(P0.05);梗死区和半暗带MTT、TTP均明显高于对照区,且梗死区MTT、TTP显著高于对照区(P0.05);CTP联合CTA诊断AIS的灵敏度、特异度、准确率分别为86.54%、90.32%、87.41%。结论 CTP可定量检测脑部血液灌流情况,区分梗死区和半暗带,CTA可准确检测血管狭窄部位和程度,CTP联合CTA检测诊断AIS的准确性较高。     

CT灌注成像在急性缺血性卒中患者诊断及预后评估中的应用

目的 探讨CT灌注成像在急性缺血性卒中（AIS）患者诊断及预后评估中的应用价值。方法 回顾性研究。纳入2020年2月—2021年7月河南省直第三人民医院收治的AIS患者104例,其中,男61例、女43例,年龄46~81（62.7±12.3）岁。患者均接受急诊脑CT灌注成像检查,获取核心梗死面积,以及脑血流量（CBF）、脑血容量（CBV）、对比剂平均通过时间（MTT）和峰值时间（TTP）等CT灌注成像血流动力学参数,对比分析患者脑梗死区和缺血半暗带脑组织间CBF、CBV、MTT、TTP值的差异。以《中国急性缺血性脑卒中诊疗指南2018》为金标准,分析CT灌注成像AIS患者的检出率。入院时进行美国国立卫生研究院卒中量表（NIHSS）评分评估患者神经功能状态。治疗后3个月采用改良Rankin量表（mRS）评分评估患者预后,并按照预后评估结果进行分组观察。采用logistic回归分析AIS预后的预测因素。结果 本组104例AIS患者中,经CT灌注成像检查显示梗死区及半暗带血流异常者共96例（检出率为92.31%）。CT灌注成像检出的96例中,mRS评分评估预后良好者69例、预后不良者27例。脑梗死区和缺血半暗带分别与健侧对应部位的正常脑组织相比,CBF、CBV值降低,MTT、TTP延长,差异均有统计学意义（P值均<0.05）。预后不良组核心梗死面积、发病至溶栓时间及高脂血症比例、NIHSS评分及缺血半暗带CT灌注参数MTT、TTP均高于预后良好组,CT灌注参数CBF、CBV均低于预后良好组,差异均有统计学意义（P值均<0.05）。logistic回归分析结果显示,核心梗死面积、发病至溶栓时间、高脂血症,NIHSS评分,以及缺血半暗带CT灌注成像血流动力学参数CBF、CBV、MTT、TTP等均是AIS患者预后的预测因素（P值均<0.05）。结论 CT灌注成像检查可快速反映脑部组织灌注损伤情况,对AIS患者的及时诊断具有重要意义;且CT灌注成像血流动力学参数可有效反映AIS患者溶栓治疗后受累血管再通情况,为其预后评估提供一定依据。     

多层螺旋CT灌注成像对脑肿瘤瘤周水肿的临床应用

目的 探讨瘤周水肿的多层螺旋CT灌注成像(CTPI)在脑肿瘤诊断方面的应用价值.方法 采用Sensation 16层螺旋CT机对本院29例脑肿瘤患者(胶质瘤14例,转移瘤7例,脑膜瘤8例)行CTPI,分别测量不同瘤周水肿区以及对侧正常脑组织的脑血流量(CBF)、脑血容量(CBV)、肿瘤表面渗透性(PS)、对比剂峰值时间(time to peak,TTP),并进行比较.结果 转移瘤和脑膜瘤瘤周水肿的CBV、CBF显著低于对侧正常脑组织(P＜0.05),PS差异则无统计学意义(P＞0.05).与对侧正常脑组织比较,胶质瘤瘤周水肿的CBV差异无统计学意义(P＞0.05),而PS明显升高(P＜0.05),CBF降低(P＜0.05).胶质瘤、转移瘤及脑膜瘤3者瘤周水肿的TTP甲值均较对侧正常脑组织显著延长(P＜0.05).结论 脑肿瘤的CTPI检查能定量反映瘤周水肿区的血流动力学状况,对脑肿瘤的鉴别和预测预后有重要临床意义.     

颈动脉内膜切除术对颈动脉狭窄患者认知功能的影响

目的探讨颈动脉狭窄患者行颈动脉内膜切除术(CEA)后认知功能的变化情况。方法回顾性分析我院神经外科自2016年9月至2018年5月收治41例行CEA手术治疗的颈动脉狭窄患者的临床资料。分别于术前1周和术后3个月行CT脑灌注检查评估脑血流动力学情况,并使用简易精神状态量表(MMSE)及蒙特利尔认知量表(MoCA)分别对患者手术前后的认知功能进行评分,最后分别比较患者手术前后脑灌注及认知功能的情况。结果 CT脑灌注显示术前病变侧脑灌注情况明显差于对侧,各项脑灌注参数(CBF、CBV、MTT、TTP)差异均具有统计学意义(P 0. 05);术后病变侧脑灌注情况较术前改善,其中脑血流量(CBF)、平均通过时间(MTT)、达峰时间(TTP)差异具有统计学意义(P 0. 05)。术后两侧脑灌注参数比较,仅脑血容量(CBV)差异具有统计学意义(P 0. 05)。对比手术前后MMSE总分差异虽无统计学意义,但单项中延迟回忆评分差异具有统计学意义(P=0. 031)。术后MoCA总分及其单项中视空间/执行能力、抽象能力及延迟回忆评分均显著高于术前,差异具有统计学意义(P 0. 05)。结论颈动脉内膜切除术可以提高颈动脉狭窄患者的脑灌注情况,同时患者的认知功能也出现不同程度的改善。     

CT脑肿瘤灌注特征参数定量分析与研究

目的：在研究CT脑肿瘤灌注成像过程中,肿瘤相关特征参数的定量分析为临床诊断提供重要依据。方法：介绍了CT脑灌注的相关参数,包括脑血流量（CBF）、脑血容量（CBV）、平均通过时间（MTT）和表面通透性等（PS）,根据CT扫描所获得的一系列时间影像序列,利用VisualC＋＋编程实现了脑肿瘤区域的时间密度曲线的显示,在基于去卷积方法基础之上,提出改进的算法,结合CT灌注图像上肿瘤区域的长度,角度,面积等参数的测量方法,计算出更精确地血流动力学参数。结论：脑肿瘤CT灌注图像相关特征参数的定量分析可用于脑瘤的及时诊断和治疗。     

多层螺旋CT灌注成像对脑肿瘤瘤周水肿的临床应用

目的探讨瘤周水肿的多层螺旋cT灌注成像（CTPI）在脑肿瘤诊断方面的应用价值。方法采用Sensation16层螺旋CT机对本院29例脑肿瘤患者（胶质瘤14例，转移瘤7例，脑膜瘤8例）行CTPI，分别测量不同瘤周水肿区以及对侧正常脑组织的脑血流量（CBF）、脑血容量（CBV）、肿瘤表面渗透性（PS）、对比剂峰值时间（timetopeak，TIP，并进行比较。结果转移瘤和脑膜瘤瘤周水肿的CBV、CBF显著低于对侧正常脑组织（P〈0．05），PS差异则无统计学意义（P〉0．05）。与对侧正常脑组织比较，胶质瘤瘤周水肿的CBV差异无统计学意义（P〉0．05），而PS明显升高（P〈0．05），CBF降低（P〈0．05）。胶质瘤、转移瘤及脑膜瘤3者瘤周水肿的TTP值均较对侧正常脑组织显著延长（P〈0．05）。结论脑肿瘤的CTPI检查能定量反映瘤周水肿区的血流动力学状况，对脑肿瘤的鉴别和预测预后有重要临床意义。     

踝臂指数与CT灌注成像在脑缺血早期的诊断价值

目的:研究踝臂指数(Ankle-Brachial Index,ABI)和多排CT灌注成像在缺血性脑血管病中的诊断参考价值,从而为脑缺血患者提供更为简便而又快速的筛选和检查方法。方法:入选2010至2013年期间高度怀疑急性缺血性脑卒中病例210例,其中踝臂异常组66例,踝臂正常组144例。入选的所有病例接受多排CT动态容积全脑灌注成像、颅脑CT血管造影及CT灌注成像。对所灌注参数图即脑血流量(CBF)、脑血容量(CBV)、平均通过时间(MTT)、达峰时间(TTP)及延迟(Delay)均由本院高年资医师进行评估,并且通过ABI初步估计颅脑CT灌注异常的阳性预测值、阴性预测值、灵敏度和特异度。结果:入选的全部患者中有136例出现脑灌注异常,表现为MTT、TTP延长,CBV升高、正常或减低,CBF正常或减低。所测得的ABI异常组中,其中有25例脑灌注异常,ABI正常组有86例脑灌注异常,ABI异常组脑灌注阳性率(75.8%,25/33)高于ABI正常组(59.7%,86/144),差异有统计学意义(P=0.039),且ABI异常组的相对MTT、相对TTP大于ABI正常组,差异有统计学意义(P<0.05)。ABI预测颅脑CT灌注异常的阳性预测值、阴性预测值、灵敏度和特异度分别为76.1%、39.3%、35.6%、77.9%。结论:采用多排CT进行动态容积全脑灌注扫描可以早期、全面、准确评价早期脑血管血流动力学的变化,便于检测的ABI对分析评估和判断脑灌注异常有一定的预测价值,联合ABI和多排CT灌注成像扫描可以对脑血管病做到早发现、早诊断、早治疗。     

Functional Cluster Analysis of CT Perfusion Maps: A New Tool for Diagnosis of Acute Stroke?

CT perfusion imaging constitutes an important contribution to the early diagnosis of acute stroke. Cerebral blood flow (CBF), cerebral blood volume (CBV) and time-to-peak (TTP) maps are used to estimate the severity of cerebral damage after acute ischemia. We introduce functional cluster analysis as a new tool to evaluate CT perfusion in order to identify normal brain, ischemic tissue and large vessels. CBF, CBV and TTP maps represent the basis for cluster analysis applying a partitioning (k-means) and density-based (density-based spatial clustering of applications with noise, DBSCAN) paradigm. In patients with transient ischemic attack and stroke, cluster analysis identified brain areas with distinct hemodynamic properties (gray and white matter) and segmented territorial ischemia. CBF, CBV and TTP values of each detected cluster were displayed. Our preliminary results indicate that functional cluster analysis of CT perfusion maps may become a helpful tool for the interpretation of perfusion maps and provide a rapid means for the segmentation of ischemic tissue.     

CT perfusion as a useful tool in the evaluation of leuko-araiosis

Background

Leuko-araiosis (LA) and dementia are common geriatric conditions but their pathogenesis and clinical significance are not completely understood. An evaluation of CT perfusion (CTP) in both these conditions can further enhance the understanding of these diseases.

Methods

Twenty-one patients with LA and 21 age-matched controls were studied with CTP and assessed for their cognitive function. The subjects were classified into four groups: Group 1, with LA (n = 21); Group 2, without LA (n = 21); Group 3, with dementia (n = 7); Group 4, without dementia (n = 11). The mean cerebral blood flow (CBF), cerebral blood volume (CBV) and mean transit time (MTT) values were compared between groups 1 and 2, while mean CBF values were compared between groups 3 and 4.

Results

Mean white matter CBF was considerably reduced in patients with LA in the frontal region by 42% (p = 0.000), basal ganglia by 37% (p = 0.000) and occipital region by 18% (p = 0.019). The mean white matter CBV was reduced in patients with LA in the frontal region by 36% (p = 0.000) and basal ganglia by 28% (p = 0.017). The mean white matter CBF was dramatically reduced in patients with dementia in the frontal region by 44% (p = 0.000), basal ganglia by 32% (p = 0.038) and occipital regions by 24% (p = 0.001).

Conclusion

The CTP showed reduced white matter CBF and CBV in patients with LA. This is consistent with chronic ischemia as the pathogenesis of LA. The CTP is also a potentially important technique in the diagnosis and management of dementia, because of its ability to reveal cerebral hypoperfusion.     

Effect of x-ray tube current on the accuracy of cerebral perfusion parameters obtained by CT perfusion studies

The purpose of this study was to investigate the effect of x-ray tube current on the accuracy of cerebral perfusion parameters obtained by CT perfusion studies using multi-detector row CT (MDCT). Following the standard CT perfusion study protocol, continuous (cine) scans (1 s/rotation x 60 s) consisting of four 5 mm thick contiguous slices were performed using an MDCT scanner with a tube voltage of 80 kVp and a tube current of 200 mA. We generated the simulated images with tube currents of 50 mA, 100 mA and 150 mA by adding the corresponding noise to the raw scan data of the original image acquired above using a noise simulation tool. From the original and simulated images, we generated the functional images of cerebral blood flow (CBF), cerebral blood volume (CBV) and mean transit time (MTT) in seven patients with cerebrovascular disease, and compared the correlation coefficients (CCs) between the perfusion parameter values obtained from the original and simulated images. The coefficients of variation (CVs) in the white matter were also compared. The CC values deteriorated with decreasing tube current. There was a significant difference between 50 mA and 100 mA for all perfusion parameters. The CV values increased with decreasing tube current. There were significant differences between 50 mA and 100 mA and between 100 mA and 150 mA for CBF. For CBV and MTT, there was also a significant difference between 150 mA and 200 mA. This study will be useful for understanding the effect of x-ray tube current on the accuracy of cerebral perfusion parameters obtained by CT perfusion studies using MDCT, and for selecting the tube current.     

An account of the discrepancy between MRI and PET cerebral blood flow measures. A high-field MRI investigation

There is controversy concerning the discrepancy between absolute cerebral blood flow (CBF) values measured using positron emission tomography (PET) and magnetic resonance imaging (MRI). To gain insight into this problem, the increased signal-to-noise ratio (SNR) and extended T(1) relaxation times of blood and tissue at 3.0 T were exploited to perform pulsed arterial spin labeling (PASL) MRI measurements as a function of spatial resolution and post-labeling delay. The results indicate that, when using post-labeling delays shorter than 1500 ms, MRI gray matter flow values may become as high as several times the correct CBF values owing to tissue signal contamination by remaining arterial blood water label. For delays above 1500 ms, regional PASL-based CBF values (n = 5; frontal gray matter: 48.8 +/- 3.3(SD) ml/100 g/min; occipital gray matter: 49.3 +/- 4.5 ml/100 g/min) comparable with PET-based measurements can be obtained by using spatial resolutions comparable with PET (5-7.5 mm in-plane). At very high resolution (2.5 x 2.5 x 3 mm(3)), gray matter CBF values were found to increase by 10-20%, a consequence attributed to reduction in partial volume effects with cerebrospinal fluid and white matter. The recent availability of MRI field strengths of 3.0 T and higher will facilitate the use of MRI-based CBF measurements in the clinic.     

Quantitative measurements of cerebral metabolic rate of oxygen utilization using MRI: a volunteer study.

Quantitative estimates of cerebral metabolic rate of oxygen utilization using magnetic resonance imaging can have profound implications for the understanding of brain metabolic activity as well as the investigation of cerebrovascular disease. In this study, five normal volunteers were studied. All images were acquired on a Siemens 1.5 T scanner (Siemens Medical Systems Inc, Erlangen, Germany). Cerebral blood flow (CBF) was obtained in vivo with a dynamic imaging approach and the acquired images were post-processed with the singular value decomposition method (SVD). In addition, a multi-echo gradient echo/spin echo sequence was employed to provide MR estimates of oxygen extraction fraction (MR_OEF) in vivo. Subsequently, an absolute measure of MR cerebral metabolic rate of oxygen utilization (MR_CMRO(2)) was obtained in all subjects by taking the product of CBF and MR_OEF. A mean MR_CMRO(2) of 28.94 +/- 3.26 ml/min/100 g and 12.57 +/- 3.11 ml/min/100 g was obtained for gray matter and white matter, respectively, suggesting that the gray matter utilizes more oxygen than white matter under normal physiological conditions. These results yield a gray matter to white matter CMRO(2) ratio of 2.37 +/- 0.37, which is comparable to the reported values in the literature. More studies are needed to further improve on the accuracy as well as shortening the required data acquisition time so that the proposed approaches can be utilized in a routine clinical setting.     

Reassessing the clinical efficacy of two MR quantitative DSC PWI CBF algorithms following cross-calibration with PET images

Clinical cerebral blood flow (CBF) maps generated through dynamic- susceptibility contrast (DSC) magnetic resonance (MR) perfusion imaging are currently cross-calibrated with PET studies. The cross-calibration is achieved by rescaling the MR CBF values so that normal white matter CBF corresponds to 22 ml/100 g/min. Examples are provided in this paper to show how this rescaling procedure changes both the clinical interpretation of CBF maps and the manner by which the performance of a given deconvolution algorithm should be assessed. (i) Singular-value decomposition-based (SVD) algorithms produce absolute CBF estimates that are inherently under-estimated for all tissue mean transit times (MTT) but, after rescaling, will generate CBF maps that are over-estimated for MTT >4.8 s. (ii) In principle, frequency-domain modelling techniques are expected to be inherently less sensitive to contrast recirculation biases than the time-domain SVD algorithms. However, it is shown that both CBF algorithms become greatly less sensitive to distortions from recirculation after clinical cross-calibration through rescaling has been performed. It is concluded that, when rescaling procedures are employed, it is relatively more important to develop deconvolution algorithms that produce CBF estimates with accuracies that vary little with MTT than to produce algorithms that provide inherently more accurate CBF estimates, but whose relative accuracy varies significantly with MTT.     

Time‐efficient measurement of multi‐phase arterial spin labeling MR signal in white matter

White matter (WM) perfusion has great potential as a physiological biomarker in many neurological diseases. Although it has been demonstrated previously that arterial spin labeling magnetic resonance imaging (ASL‐MRI) enables the detection of the perfusion‐weighted signal in most voxels in WM, studies of cerebral blood flow (CBF) in WM by ASL‐MRI are relatively scarce because of its particular challenges, such as significantly lower perfusion and longer arterial transit times relative to gray matter (GM). Recently, ASL with a spectroscopic readout has been proposed to enhance the sensitivity for the measurement of WM perfusion. However, this approach suffers from long acquisition times, especially when acquiring multi‐phase ASL datasets to improve CBF quantification. Furthermore, the potential increase in the signal‐to‐noise ratio (SNR) by spectroscopic readout compared with echo planar imaging (EPI) readout has not been proven experimentally. In this study, we propose the use of time‐encoded pseudo‐continuous ASL (te‐pCASL) with single‐voxel point‐resolved spectroscopy (PRESS) readout to quantify WM cerebral perfusion in a more time‐efficient manner. Results are compared with te‐pCASL with a conventional EPI readout for both WM and GM perfusion measurements. Perfusion measurements by te‐pCASL PRESS and conventional EPI showed no significant difference for quantitative WM CBF values (Student's t‐test, p = 0.19) or temporal SNR (p = 0.33 and p = 0.81 for GM and WM, respectively), whereas GM CBF values (p = 0.016) were higher using PRESS than EPI readout. WM CBF values were found to be 18.2 ± 7.6 mL/100 g/min (PRESS) and 12.5 ± 5.5 mL/100 g/min (EPI), whereas GM CBF values were found to be 77.1 ± 11.2 mL/100 g/min (PRESS) and 53.6 ± 9.6 mL/100 g/min (EPI). This study demonstrates the feasibility of te‐pCASL PRESS for the quantification of WM perfusion changes in a highly time‐efficient manner, but it does not result in improved temporal SNR, as does traditional te‐pCASL EPI, which remains the preferred option because of its flexibility in use.