脑膜瘤动态增强磁化率MR灌注成像

脑MR灌注主要是描述脑微血管网中的血流情况。本文从MR灌注的基本原理及概念、成像方法，图像资料的后处理等几个方面阐明动态增强磁化率MR灌注成像方法的基本技术方法。通过对动态增强磁化率MR灌注成像正常人和脑膜瘤血供特点等方面的研究介绍，阐明其在术前脑膜瘤分型及良、恶性鉴别等方面的临床应用价值。     

Perfusion MR imaging for differentiation of benign and malignant meningiomas

INTRODUCTION: Our purpose was to determine whether perfusion MR imaging can be used to differentiate benign and malignant meningiomas on the basis of the differences in perfusion of tumor parenchyma and/or peritumoral edema. METHODS: A total of 33 patients with preoperative meningiomas (25 benign and 8 malignant) underwent conventional and dynamic susceptibility contrast perfusion MR imaging. Maximal relative cerebral blood volume (rCBV) and the corresponding relative mean time to enhance (rMTE) (relative to the contralateral normal white matter) in both tumor parenchyma and peritumoral edema were measured. The independent samples t-test was used to determine whether there was a statistically significant difference in the mean rCBV and rMTE ratios between benign and malignant meningiomas. RESULTS: The mean maximal rCBV values of benign and malignant meningiomas were 7.16+/-4.08 (mean+/-SD) and 5.89+/-3.86, respectively, in the parenchyma, and 1.05+/-0.96 and 3.82+/-1.39, respectively, in the peritumoral edema. The mean rMTE values were 1.16+/-0.24 and 1.30+/-0.32, respectively, in the parenchyma, and 0.91+/-0.25 and 1.24+/-0.35, respectively, in the peritumoral edema. The differences in rCBV and rMTE values between benign and malignant meningiomas were not statistically significant (P>0.05) in the parenchyma, but both were statistically significant (P<0.05) in the peritumoral edema. CONCLUSION: Perfusion MR imaging can provide useful information on meningioma vascularity which is not available from conventional MRI. Measurement of maximal rCBV and corresponding rMTE values in the peritumoral edema is useful in the preoperative differentiation between benign and malignant meningiomas.     

纤维母细胞型脑膜瘤在弥散张量磁共振成像上的表现

目的探讨纤维母细胞型脑膜瘤在弥散张量磁共振成像(DTMRI)上的表现。方法对手术病理证实的2例纤维母细胞型脑膜瘤与20例其他亚型脑膜瘤患者的DTMRI表现进行对照分析。结果 2例纤维母细胞型脑膜瘤中,DTI纤维示踪图像1例表现为"花簇样",1例表现为"线团样"。20例其他亚型脑膜瘤DTI张量纤维示踪图像未见上述征象。结论脑膜瘤DTI纤维示踪图像显示的"花簇样""、线团样"表现,提示纤维母细胞型脑膜瘤的诊断。     

高CO2分压下大鼠神经胶质瘤肿瘤血管的MR灌注成像特点

目的 了解MR灌注成像显示肿瘤血管成熟度和变异度的可行性.方法 20只雄性SD大鼠,采用数字表法随机平分为肿瘤组和正常对照组.肿瘤组大鼠于右侧尾状核区种植C6胶质瘤细胞,复制大鼠脑胶质瘤模型.种植肿瘤细胞后4周,两组大鼠吸入高浓度CO2混合气体,吸入气体前后,分别行全脑灌注成像扫描,检测局部相对脑血容量(rCBV)、局部相对脑血流量(rCBF).扫描前测定大鼠血CO2分压、pH值等血气指标.检查后处死肿瘤组大鼠并取脑固定,全脑切片,分别行苏木精-伊红及鼠特异性平滑肌抗体反应素(SMA)抗体免疫组织化学染色.光学显微镜下观察肿瘤组织特征并进行SMA阳性血管计数.采用配对t检验比较两组大鼠脑组织MR灌注值、肿瘤组织微血管计数及血气指标的差异,并将免疫组织化学检查结果与MR检查结果进行Pearson相关性分析.结果胶质瘤的rCBV和rCBF呈明显的高灌注.所有大鼠在吸入含高浓度CO2的混合气体15 min后,血液CO2分压肿瘤组从(4.69±0.62)kPa升高至(7.62±0.81)kPa,对照组从(4.67±0.51)kPa升高至(7.63±0.78)kPa,差异具有统计学意义(t值分别为6.09,7.012,P值均＜0.05);pH值肿瘤组从(7.42±0.03)降至(7.10±0.05),对照组从(7.40±0.04)降至(7.08±0.02),差异具有统计学意义(t值分别为2.745,2.693,P值均＜0.05).肿瘤实质部分的rCBV和rCBF的增加率分别为(26±17)%和(26±18)%,低于肿瘤组健侧正常脑组织[分别为(90±32)%和(45±14)%],二者差异具有统计学意义(t值分别为5.05,2.355,P值均＜0.05).SMA染色部位在血管的平滑肌细胞,形态规则,肿瘤内SMA阳性血管较正常脑组织的阳性血管管壁薄,管腔直径宽;肿瘤内SMA阳性血管[(6.7±2.8)个/高倍视野]明显少于肿瘤组健侧脑组织[(12.7±2.8)个/高倍视野](t=1.86,P＜0.05).吸入高浓度CO2混合气体后,肿瘤实质区的rCBV和rCBF的变化率与免疫组织化学的SMA阳性血管计数之间均无显著的相关性(r值分别为0.504和0.607,P值均＞0.05).但正常脑组织的rCBV和rCBF变化率与其SMA阳性血管计数之间呈正相关(r值分别为0.721和0.525,P值均＜0.05).结论 MR灌注技术在改变血液CO2分压的条件下可以反映正常脑组织和肿瘤组织血流变化,进而间接判断肿瘤血管的成熟度.     

MR灌注成像在鉴别单发脑转移瘤与高级别胶质瘤中的价值

目的探讨MR灌注成像在鉴别单发脑转移瘤与高级别胶质瘤中的作用及价值。方法对10例单发脑转移瘤和15例高级别胶质瘤患者行手术前MR灌注成像扫描。分析其MR灌注曲线及伪彩图像,测量肿瘤实质部分及瘤周水肿区最大相对脑血容积(rCBV)值及相应部位相对平均通过时间(rMTT)数值并将所测值进行t检验。结果单发脑转移瘤的MR灌注曲线形态和伪彩图像中的色彩特点与高级别胶质瘤有明显区别。单发脑转移瘤与高级别胶质瘤肿瘤实质部分的最大rCBV值分别为3.70±2.34、6.01±2.17,瘤周水肿区则分别为0.80±0.28、1.77±1.19。单发脑转移瘤与高级别胶质瘤肿瘤实质相应部位的rMTT值分别为1.17±0.39、1.11±0.18,瘤周水肿区则分别为1.17±0.38、1.02±0.20。两者肿瘤实质部分和瘤周水肿区的rCBV值均数之间差异有统计学意义(P<0.05),而相应的rMTT值均数之间差异没有统计学意义(P>0.05)。结论MR灌注成像对术前鉴别单发脑转移瘤与高级别胶质瘤有临床实用价值。     

MR perfusion imaging in a case of cerebral proliferative angiopathy

Proliferative angiopathy is an uncommon type of cerebral arteriovenous shunt characterized by an extensive capillary network with normal brain intermingled and few clinical symptoms (mostly seizures and headaches). This case report depicts an extensive proliferative angiopathy located in the right hemisphere. Its hemodynamic disturbances were studied with MR perfusion imaging (local or remote areas of increased time to peak, decrease ratio of signal, and relative regional cerebral blood volume values). Electronic Publication     

High-grade and low-grade gliomas: differentiation by using perfusion MR imaging

AIM: Relative cerebral blood volume (rCBV) is a commonly used perfusion magnetic resonance imaging (MRI) technique for the evaluation of tumour grade. Relative cerebral blood flow (rCBF) has been less studied. The goal of our study was to determine the usefulness of these parameters in evaluating the histopathological grade of the cerebral gliomas. METHODS: This study involved 33 patients (22 high-grade and 11 low-grade glioma cases). MRI was performed for all tumours by using a first-passage gadopentetate dimeglumine T2*-weighted gradient-echo single-shot echo-planar sequence followed by conventional MRI. The rCBV and rCBF were calculated by deconvolution of an arterial input function. The rCBV and rCBF ratios of the lesions were obtained by dividing the values obtained from the normal white matter of the contralateral hemisphere. For statistical analysis Mann-Whitney testing was carried out. A p value of less than 0.05 indicated a statistically significant difference. Receiver operating characteristic curve (ROC) analysis was performed to assess the relationship between the rCBV and rCBF ratios and grade of gliomas. Their cut-off value permitting discrimination was calculated. The correlation between rCBV and CBF ratios and glioma grade was assessed using Pearson correlation analysis. RESULTS: In high-grade gliomas, rCBV and rCBF ratios were measured as 6.50+/-4.29 and 3.32+/-1.87 (mean+/-SD), respectively. In low-grade gliomas, rCBV and rCBF ratios were 1.69+/-0.51 and 1.16+/-0.38, respectively. The rCBV and rCBF ratios for high-grade gliomas were statistically different from those of low-grade gliomas (p < 0.001). The rCBV and CBF ratios were significantly matched with respect to grade, but difference between the two areas was not significant (ROC analysis, p > 0.05). The cut-off value was taken as 1.98 in the rCBV ratio and 1.25 in the rCBF ratio. There was a strong correlation between the rCBV and CBF ratios (Pearson correlation = 0.830, p < 0.05). CONCLUSION: Perfusion MRI is useful in the preoperative assessment of the histopathologicalal grade of gliomas; the rCBF ratio in addition to the rCBV ratio can be incorporated in MR perfusion analysis for the evaluation.     

1.5T场强MR动脉自旋标记灌注成像在脑梗死中的初步应用

目的：探讨采用1.5T场强MR动脉自旋标记灌注成像（ASL-PWI）评价脑梗死的可行性。方法：对34例临床和MRI发现脑梗死的患者行常规MRI、扩散加权成像（DWI）及ASL-PWI扫描,根据Adamas分类将急性脑梗死分为大面积和小面积2组,比较DWI和ASL-PWI上病变的范围,比较病变区CBF值（CBF病变）与对侧正常区CBF值（CBF正常）。结果：20例大面积脑梗死中5例ASL-PWI显示病灶范围较DWI大,9例两者显示范围相当,5例前者小于后者,1例未见异常灌注区;14例小面积脑梗死中6例显示低灌注区,7例未能明确显示低灌注区,1例灌注增强;除1例灌注增强病例CBF病变大于CBF正常外,其它均小于后者。结论：在1.5T磁场强度上应用ASL-PWI技术能基本反映脑梗死区血流灌注的改变,其严格的相关性及临床意义有待于进一步探索。     

Theoretical and experimental evaluation of phase-dispersion effects caused by brain motion in diffusion and perfusion MR imaging

We investigated intravoxel phase dispersion caused by pulsatile brain motion in diffusion spin-echo pulse sequences. Mathematical models were used to describe the spatial and temporal velocity distributions of human brain motion. The spatial distribution of brain-tissue velocity introduces a phase spread over one voxel, leading to signal loss. This signal loss was estimated theoretically, and effects on observed diffusion coefficient and perfused capillary fraction were assessed. When parameters from a diffusion pulse sequence without motion compensation were used, and ECG triggering with inappropriate delay times was assumed, the maximal signal loss caused by brain-motion-induced phase dispersion was predicted to be 21%. This corresponds to a 95% overestimation of the diffusion coefficient, and the perfusion-fraction error was small. Corresponding calculations for motion-compensated pulse sequences predicted a 1% to 1.5% signal loss due to undesired phase dispersion, whereas experimental results indicated a signal loss related to brain motion of 4%.     

Noninvasive perfusion imaging of human brain tumors with EPISTAR

A total of 17 patients with histologically proven diagnoses of low-grade astrocytoma (n = 4), high-grade astrocytoma (n = 8), lymphoma (n = 3), and meningioma (n = 2) were examined by using EPISTAR MR imaging. Meningiomas had the highest EPISTAR tumor/white matter contrast and low-grade astrocytomas and lymphomas the lowest. High-grade astrocytomas demonstrated elevated EPISTAR signal with marked regional heterogeneity. There was agreement between tumor vascularity by SPECT and EPISTAR in the five cases where both were done. Our results show that tumor vascularity can be assessed qualitatively by using EPISTAR without the need for contrast medium injection. Correspondence to: J. Gaa     

乳腺肿瘤MR灌注加权成像的研究进展

MR在乳腺肿瘤诊断方面的应用价值逐渐提高,磁共振灌注加权成像是反映组织或病灶的微血管分布和血流灌注情况的成像技术,可以无创的评价肿瘤组织的血管生成情况,对肿瘤血供分析,进而评估肿瘤的良恶性.随着影像技术的发展,形成了多种乳腺MRI灌注成像技术.目前主要有两方面的内容:一是通过注射对比剂来研究器官、组织或病灶的微血管循环情况;二是使用对水分子微量运动特别敏感的成像序列来观察微循环灌注的情况.本文就乳腺MR灌注成像的常用方法予以综述.     

肺栓塞MR增强肺灌注成像与核素肺灌注显像对比实验研究

目的:比较MR及SPECT核素肺灌注显像诊断肺栓塞的价值。方法:24只大白兔建立肺栓塞模型,栓塞后6h采用3D-FLASH序列,从耳缘静脉注入Gd-DTPA行肺灌注扫描,应用Evaluation自动生成肺灌注曲线,在冠状位原始图像上两侧对称性选取正常与病变区肺实质的ROI测量时间-信号强度曲线。从耳缘静脉注入99Tcm-MAA111-148MBq0·3ml8体位显像。病理学检查:分别于栓塞后分批处死实验动物,光学显微镜下观察栓塞肺组织及正常肺组织的表现。统计学采用t检验和χ2检验。结果:成功建立20只兔肺栓塞模型,栓塞后6hMR增强肺灌注成像正常和栓塞区肺实质增强率分别为317·5%和45·1%;正常肺组织灌注曲线峰值明显,栓塞区灌注曲线低平或峰值延迟(t=11·52,P<0·01)。MR增强肺灌注成像对肺栓塞模型检测的敏感性为95%,特异性为85%;SPECT肺灌注显像敏感性100%,特异性65%,统计学分析二者检查结果差异不具有统计学意义(χ2=2·06,P>0·05)。病理显示:梗死区可见大量的纤维素渗出,肺间质增厚,动脉腔内可见红细胞和血栓形成,其周围白细胞浸润伴肺淤血,部分可见点状出血及肺淤血。结论:Gd-DTPAMR增强肺灌注成像诊断肺栓塞是可行的;MR诊断肺栓塞与SPECT具有较好的一致性。     

骨肿瘤的MR灌注和扩散加权成像研究

目的对临床常见的骨肿瘤进行MR灌注成像(PWI)和扩散加权成像(DWI)研究,探讨其在骨肿瘤定性诊断中的价值。方法收集恶性骨肿瘤18例,良性骨肿瘤21例,行MR PWI和MR DWI,应用Functool2软件分析,于灌注像上得到病灶时间-信号曲线(TIC)、首过期(FP)信号递减幅度、TIC最大线性斜率、两次稳态信号差值;于DWI上获得病灶表观扩散系数(ADC)值;采用SPSS13.0统计分析软件,将从良、恶性骨肿瘤两组样本中获得的各种参数用成组设计的两样本均数进行t检验,采用受试者操作特征(ROC)曲线选择良恶性肿瘤鉴别诊断的阈值,计算MR PWI和MR DWI诊断恶性骨肿瘤的敏感度、特异度、和准确度。结果MR PWI显示,17/21的良性骨肿瘤TIC表现为I型(平稳型)及II型(缓降缓升型),恶性骨肿瘤TIC表现为III型和IV型(速降型);良、恶性骨肿瘤之间的FP信号递减幅度、TIC最大线性斜率及两次稳态信号差值在良、恶性骨肿瘤之间的差异均具有显著性统计学意义,其据此诊断恶性骨肿瘤的准确度分别为82.1%、79.5%和87.2%;有4例良性骨肿瘤可根据其MR-PWI作定性判断,结果误诊为恶性肿瘤。MR DWI显示:b=300s/mm2时,良、恶性骨肿瘤的ADC值的差异具有统计学意义;若以ADC1.63×10-3mm2/s为恶性阈值,其诊断恶性骨肿瘤的准确度为79.5%。MR PWI和MR DWI诊断恶性骨肿瘤的准确度分别为89.7%和79.5%。结论MR PWI比MR DWI更有助于鉴别良、恶性骨肿瘤及肿瘤样病变,但恶性骨肿瘤与富血供良性骨肿瘤及肿瘤样病变的灌注参数存在重叠,此时结合MR DWI可以提高诊断准确度。     

MR灌注成像在脑星形细胞瘤术前分级中的应用价值

目的　评价MR灌注成像在脑星形细胞瘤术前分级中的应用价值。资料与方法　对 34例脑星形细胞瘤患者行常规MRI及MR灌注成像 ,所有病例分为 3组 :低级别星形细胞瘤 (LGA) 12例 ,间变性星形细胞瘤 (AA) 13例 ,胶质母细胞瘤 (GBM) 9例。灌注成像先得到信号强度 时间曲线 ,并合成局部脑血容量 (rCBV)图 ,计算相对局部脑血容量 (rrCBV)。计算出感兴趣区对比剂首过期末的信号下降百分率 ,作出对比剂平均通过时间 (MTT)图 ,得出MTT值 ,计算出微血管相对渗透值 (rP)。结果　LGA、AA及GBM最大rrCBV分别为 3.2 3± 0 .92 ,5 .0 5± 0 .6 6 ,5 .18± 0 .34;3组的微血管rP分别为 1.34± 0 .4 6 ,2 .17± 0 .2 8,2 .5 9± 0 .6 0。 3组间的rrCBV及rP值均有显著性差异 ,rP与rCBV有明显正相关 (r=0 .85 3,P <0 .0 1)。结论　MR灌注成像参数rrCBV、rP能在术前可靠地评价星形细胞瘤的病理级别。     

X-刀治疗大鼠胶质瘤的磁共振灌注成像

目的 :观察X 刀对大鼠脑胶质瘤的治疗作用 ,探讨MR灌注成像 (PWI)对X 刀治疗疗效的早期评价。方法 :2 0只SD雄性大鼠右尾状核接种C6胶质瘤细胞复制大鼠脑胶质瘤模型。治疗组 10只接种胶质瘤细胞后第 15天行X 刀治疗 ,10只对照组未行治疗 ,分别第 15天 (治疗组X 刀治疗前 )和第 17天行PWI ,计算肿瘤的相对局部脑血容量(rrCBV) ,观察治疗后肿瘤rrCBV的变化率 ,并与荷瘤鼠存活期进行回归分析。结果 :肿瘤接种成功率为 10 0 %。治疗组治疗后 48h肿瘤的rrCBV明显减小 ,其下降百分比平均为 3 5 .8%。对照组和治疗组大鼠生存期分别为 2 2 .8和 3 0 .5d ,两组间差异有显著意义。X 刀治疗后肿瘤rrCBV的下降百分比与大鼠生存期密切相关 (r =0 .82 ,P <0 .0 5 )。结论 :X 刀治疗能延长荷胶质瘤大鼠生存期 ,PWI能在治疗后早期判断愈后     

Improved visualization of delayed perfusion in lung MRI

Introduction

The investigation of pulmonary perfusion by three-dimensional (3D) dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI) was proposed recently. Subtraction images are generated for clinical evaluation, but temporal information is lost and perfusion defects might therefore be masked in this process. The aim of this study is to demonstrate a simple analysis strategy and classification for 3D-DCE-MRI perfusion datasets in the lung without omitting the temporal information.

Materials and methods

Pulmonary perfusion measurements were performed in patients with different lung diseases using a 1.5 T MR-scanner with a time-resolved 3D-GRE pulse sequence. 25 3D-volumes were acquired after iv-injection of 0.1 mmol/kg KG Gadolinium-DTPA. Three parameters were determined for each pixel: (1) peak enhancement S_n,max normalized to the arterial input function to detect regions of reduced perfusion; (2) time between arterial peak enhancement in the large pulmonary artery and tissue peak enhancement τ to visualize regions with delayed bolus onset; and (3) ratio R = S_n,max/τ was calculated to visualize impaired perfusion, irrespectively of whether related to reduced or delayed perfusion.

Results

A manual selection of peak perfusion images is not required. Five different types of perfusion can be found: (1) normal perfusion; (2) delayed non-reduced perfusion; (3) reduced non-delayed perfusion; (4) reduced and delayed perfusion; and (5) no perfusion. Types II and IV could not be seen in subtraction images since the temporal information is necessary for this purpose.

Conclusions

The analysis strategy in this study allows for a simple and observer-independent visualization and classification of impaired perfusion in dynamic contrast-enhanced pulmonary perfusion MRI by using the temporal information of the datasets.     

Role of diffusion- and perfusion-weighted MR imaging for brain tumour characterisation

Purpose  This study was undertaken to correlate apparent diffusion coefficient (ADC) and relative regional cerebral blood volume (rrCBV) to histological findings in a large series of patients with primary or secondary brain tumours to evaluate diffusion-weighted (DWI) and perfusionweighted (PWI) imaging in the characterisation of cerebral tumors. Materials and methods  Ninety-eight patients with cerebral tumours, 46 of which were primary (seven grade 0-I, nine low-grade gliomas, two gliomatosis cerebri, nine lymphomas and 19 high-grade gliomas) and 52 secondary, underwent conventional magnetic resonance (MR) imaging completed with DWI and dynamic contrast susceptibility PWI. Both ADC and rrCBV were calculated on a workstation by using Functool 2 software. Student’s t test was used to determine any statistically significant differences in the ADC and rrCBV values. Results  Seventeen of 98 tumours were cystic or necrotic (12/17 hypointense and 5/17 hyperintense on DWI); the ADC value of hyperintense cystic areas was 0.97±0.23×10⁻³ mm²/s. The ADC value of solid tumours varied between 0.64 and 3.5×10⁻³ mm²/s. The rrCBV value was 1.4 (σ 0.66) in low-grade gliomas; 1.22 (σ 0.25) in lymphomas; 4.5 (σ 0.85) in grade III gliomas; 3.18 (σ 1.26) in grade IV gliomas and 2.53 (σ 1.6) in metastases. Conclusions  DWI has an important role in the differential diagnosis of cystic cerebral masses but not in tumour characterisation. PWI is helpful in differentiating high-from low-grade gliomas and lymphomas from high-grade gliomas.      

慢性胰腺炎MR灌注加权成像实验研究

目的 探讨猪慢性胰腺炎(CP)MR灌注加权成像(PWI)表现.方法 从28头猪中,以数字表法随机抽取22头经剖腹行胰管结扎制作CP动物模型,另外6头不进行处理.麻醉后行MR PWI,检查后随即处死动物,根据胰腺组织病理检查结果,将实验猪分为胰腺正常组、CP Ⅰ期组、CP Ⅱ期组和CP Ⅲ期组.采用方差分析法比较各组问胰腺最大灌注斜率、达峰时间和最大强化率,并采用相关性分析法判定各灌注参数与CP严重程度的关系.结果21头猪进行了MR PWI检查,其中胰腺正常组7头、CP Ⅰ期组7头、CP Ⅱ期组3头和CP Ⅲ期组4头.胰腺正常组、CP Ⅰ期组、CP Ⅱ期组和CP Ⅲ期组最大灌汴斜率分别为(10.88±1.20)%、(10.59±1.02)%、(6.67±1.31)%和(5.48±1.97)%,差异有统计学意义(F=20.51,P＜0.05);达峰时间分别为(13.82±3.09)s、(12.31±5.52)s、(20.55±3.79)s和(37.26±14.56)s,差异有统计学意义(F=10.68,P＜0.05);最大强化率分别为(62.95±20.20)%、(60.44±20.00)%、(46.33±22.70)%和(67.65±32.66)%,差异无统计学意义(F=0.53,P＞0.05).最大灌注斜率(r=0.72,P＜0.05)和达峰时间(r=0.54,P＜0.05)与CP严重程度间具有相关性;CP严重程度与最大强化率间无明显线性关系.结论MR PWI可以检测猪CP改变,并可对其进行分期.     

脑膜瘤相对血流量MR定量检测:梯度回波与平面回波序列法的比较

目的通过对梯度回波序列法与平面回波(echoplanerimaging,EPI)序列法重建脑膜瘤相对血流量图的比较,对脑膜瘤相对血流量的定量检测进行评价。方法应用西门子1.5TMR仪对18例脑膜瘤病人进行检查,获取常规的T1WI、T2WI和增强T1WI,以及动态的磁顺应敏感图像(T2WI梯度回波序列或SEEPI序列)。在采集动态的磁顺应敏感图像期间(梯度回波法12例,EPI法6例),应用程控注射器以每秒5ml的流率注入钆喷替酸葡甲胺(GdDTPA)(0.2mmol/kg)。应用优视系统(advancedvisualsystem,AVS)软件逐点处理动态的磁顺应敏感资料,对重建的全部相对血流量图作感兴趣区分析,通过借鉴文献中脑灰质血流量数值,定量计算脑膜瘤的相对血流量。结果肿瘤相对血流量与脑灰质相对血流量的比率是3.01±1.18(梯度回波序列法为3.07±1.39;EPI序列法为2.84±0.94)。脑膜瘤的平均相对血流量为(14.47±5.96)ml/100g:梯度回波序列法为(14.85±6.72)ml/100g,EPI序列法为(13.72±4.54)ml/100g;梯度回波序列法与EPI序列法的结果比较差异无统计学意义(t=0.42,P=0.68)。结论应用脑灰质血流量数值法可便捷地定量检测脑膜瘤的相对血流量,脑膜瘤的相对血流量明显增高而且非均匀性;血脑屏障破坏情况下,仍可估算相对血流量值;尽管EPI序列法更具有效应,梯度回波序列法和EPI序列法均能有效地应用于相对血流量的测定。     

Cerebral perfusion impairment correlates with the decrease of CT density in acute ischaemic stroke

Within the first 6 h of ischaemic stroke, changes on computed tomography (CT) scans are known as early ischaemic signs. We tested the hypothesis that the severity of perfusion impairment correlates with the degree of CT density decrease. Water uptake in ischaemic brain tissue results in a subtle decrease of CT density, and was quantified by delineation of the corresponding decrease of the apparent diffusion coefficient (ADC). Regions of decreased ADC and CT density in 29 acute-stroke patients were superimposed on the corresponding magnetic resonance perfusion images. Mean values of ADC and CT density decrease were correlated with the corresponding relative changes of cerebral blood flow (rCBF) and volume (rCBV), mean transit time (rMTT) and time-to-peak (rTTP). The decrease of CT density was 1.2±0.6 Hounsfield units and showed a linear correlation with rCBF (0.42, p<0.01) as well as rCBV (0.62, p<0.01), but not with the prolongation of rMTT (1.43, p=0.78) or rTTP (1.34, p=0.26). Therefore, the reduction of rCBF determines the severity of the early ischaemic oedema (EIOE) on CT, as well as reduction of the ADC. These findings provide a coherent view on the pathophysiology of the EIOE.