基于人工神经网络的颅内胶质瘤术后正常反应与肿瘤残存的MRI诊断

目的　探讨人工神经网络对颅内胶质瘤术后早期反应性强化与肿瘤残存强化的MRI表现的鉴别诊断价值。资料与方法　构建一个 3层误差反向传播 (backpropagation ,BP)网络来鉴别诊断术后肿瘤残存与正常脑组织的反应性强化。研究对象为 1 0 0例颅内胶质瘤术后患者 ,术后 1个月内至少行 1次MRI检查 ,80例作为训练数据 ,2 0例作为检验数据。对MR图像的 5个指标进行描述 ,作为输入层的输入数据输入网络。用检验数据检验网络性能 ,并用受试者操作特征 (receiveroperatingcharacteristiccurves,ROC)方法评价网络性能。结果　人工神经网络诊断出 1 3例残存肿瘤中的 1 0例 ,敏感性为 76 .9% ,诊断出 7例反应性强化中的 6例 ,特异性为 85 .7% ;放射科医师诊断出 8例残存肿瘤 ,敏感性为 61 .5 % ,诊断出 5例反应性强化 ,特异性为 71 .4%。神经网络ROC曲线下面积Az=0 .81 3± 0 .1 0 5 ,显著高于放射科医师ROC曲线下的面积Az =0 .665± 0 .1 30。结论　人工神经网络能成功鉴别颅内胶质瘤术后的反应性强化与肿瘤残存 ,可以辅助放射科医师鉴别肿瘤残存与正常脑组织的反应性强化     

3.0T MR多模态功能成像在胶质瘤术后复发与放射性坏死鉴别诊断中的价值

目的 探讨联合扩散加权成像(DWI)、灌注加权成像(PWI)和磁共振波谱(MRS)在胶质瘤术后复发与放射性坏死鉴别诊断中的价值.方法 34例胶质瘤术后复发和20例放射性坏死患者采用Siemens Verio 3.0 T磁共振扫描仪行常规MRI、DWI、PWI或MRS检查.分别测量DWI的表观扩散系数(ADC)值和rADC值、PWI的血流动力学参数和MRS的代谢物参数,利用两样本t检验和受试者工作特征曲线(ROC)分析各参数,并联合筛检DWI、PWI和MRS各自的最佳参数.结果 rADC值、rCBV和Cho/NAA分别是DWI、PWI和MRS的最佳诊断参数,对两种疾病鉴别诊断均有统计学意义(P＜0.05).以Youden指数最大值作为诊断临界点,rADC值诊断胶质瘤术后复发的敏感度和特异度分别为86.7％和72.9％.rCBV诊断胶质瘤术后复发的敏感度和特异度分别为76.5％和94.7％.Cho/NAA诊断胶质瘤术后复发的敏感度和特异度分别为77.8％和100％.联合rADC值、rCBV和Cho/NAA诊断胶质瘤术后复发的敏感度和特异度分别为94.7％和100％.结论 DWI、PWI和MRS在胶质瘤术后复发与放射性坏死鉴别诊断中有重要价值,联合最佳参数有助于两者的鉴别诊断.     

MR胰胆管成像加常规扫描在鉴别胆道术后病变良恶性上的意义

目的　探讨MR胰胆管成像 (MRCP)加常规扫描在鉴别胆道术后病变良恶性上的意义。方法　对 61例胆道术后出现不明原因发热、黄疸、右上腹痛等症状患者进行MRCP检查 ,同时行MR平扫及增强扫描 ,2位医师使用 3种不同的序列组合 (MRCP、MRCP +平扫、MRCP +平扫 +增强扫描 )独立对病变的良、恶性作出诊断。诊断结果分别与手术、病理结果对照。结果　对病变良恶性的诊断 ,仅用MRCP ,医师 1诊断的敏感度、特异度、准确度分别为 42 1%、80 9%、68 9% ,医师 2分别为47 4%、85 7%、73 8%。使用MRCP +平扫 ,医师 1诊断的敏感度、特异度、准确度分别为 78 9%、92 9%、88 5 % ,医师 2分别为 78 9%、95 2 %、90 2 %。使用MRCP +平扫 +增强扫描 ,医师 1诊断的敏感度、特异度、准确度分别为 84 2 %、95 2 %、91 8% ,医师 2分别为 84 2 %、97 6%、93 4%。MRCP +平扫的ROC曲线Az值 (医师 1为 0 90 7,医师 2为 0 92 0 ) ,较MRCP的ROC曲线下的面积 (Az值 ) (医师 1为 0 682 ,医师 2为 0 714)显著增大 (P <0 0 5 ) ,MRCP +平扫 +增强扫描的ROC曲线Az值 (医师 1为0 948,医师 2为 0 944 )较MRCP +平扫的ROC曲线Az值增大 ,但无显著性差异 (P >0 0 5 )。结论MRCP加MR常规扫描有助于鉴别病变的良恶性 ,提高术后病变     

神经胶质瘤相对性脑血流容积与血管内皮生长因子蛋白表达及微血管密度的相关性研究

目的　探讨胶质瘤相对性脑血流容积 (rCBV)与血管内皮生长因子 (VEGF)蛋白表达及肿瘤微血管密度 (MVD)间的相关性。方法　对 4 6例术前疑为幕上胶质瘤的患者行MR检查 ,术后经病理组织学证实 ,并采用免疫组织化学染色 ,观察VEGF蛋白表达情况及定量研究肿瘤MVD ,探讨rCBV与VEGF表达及MVD间的相关性。MR扫描顺序为常规MR平扫、灌注成像 (PWI)及常规MR增强扫描。PWI序列为单次激发梯度回波 平面回波 准T2 加权成像 (GRE EPI T 2 WI) ,原始灌注图像数据 ,经工作站软件计算出脑血流容积 (CBV)图 ,在CBV图上获取胶质瘤最大rCBV值。按VEGF表达阳性与阴性分为两组 ,即VEGF阳性组与VEGF阴性组 ,做统计学分析 (Mann WhitneyU检验 ) ,观察两组间最大rCBV值是否有统计学差异。采用非参数相关性分析法 (Spearman检验 )观察胶质瘤最大rCBV值与MVD间的关系。结果　 4 6例中 ,星形细胞瘤 12例 ,少枝胶质瘤 3例 ,混合性胶质瘤 1例 ,间变性星形细胞瘤 14例 ,多形性胶质母细胞瘤 16例。其中VEGF表达阴性 14例 ,VEGF表达阳性 32例。VEGF阴性组胶质瘤最大rCBV值为 0 33～ 6 6 3,中位数为 3 0 8;VEGF阳性组胶质瘤最大rCBV值为 1 0 3～ 10 6 8,中位数为 5 95。统计学分析表明 ,两组间rCBV值差异有非常显著意义 (Mann Whitney     

PET在颅内胶质瘤术后放射治疗后随访中的应用价值

目的：探讨PET在颅内胶质瘤术后,放射治疗后随诊中的作用。方法：对16例颅内胶质瘤术事并放射治疗后的病例采用双盲法将PET与CT／或MRI结果进行比较。结果：16例中14例（占87．5％）CT和／或MRI表现不规则环形或结节状明显强化,不能准确作出手术后改变和／或放射治疗后脑损伤,残存肿瘤或神经复发的诊断;其中9例残存肿瘤或肿瘤复发病灶^18F-FDG PET影像均表现为葡萄糖代谢率明显增高,另5例术后放射治疗后脑损伤病例和2例术后软化灶^18F-FDG PET影像均显示局部病变区为放射性分布缺损或明显低下。结论：与CT和MRI相比,PET在胶质瘤术后放射治疗后的脑损伤和肿瘤复发的定性诊断上具有明显的优势,若结合CT和MRI多种影像结果分析,更能提供病变解剖结构和功能改变的综合信息,尤其是对胶质瘤术后放射治疗后的临床随访非常重要。     

MRI动态增强扫描定量参数对脑胶质瘤分级诊断价值的研究

【摘要】目的：探讨MRI动态增强扫描定量参数对脑胶质瘤病理分级的诊断价值。方法：经手术病理证实的脑胶质瘤患者19例,其中高级别胶质瘤（HGG）12例,低级别胶质瘤（LGG）7例。所有患者均行常规MRI平扫及MRI动态增强（DCE）扫描。利用北京大学前沿交叉学科研究院开发的Ktrans计算系统,分别测量颅内占位性病变实质区及瘤周水肿区的Ktrans值和Ve值。不同级别胶质瘤Ktrans值的比较采用Mann-Whitney U检验。采用受试者工作特征曲线（ROC）对Ktrans和Ve值进行分析。结果： HGG及LGG组的Ktrans值分别为(0.24±0.17)和(0.07±0.04)min-1,差异有统计学意义（t=2.625,P=0.018）;Ve分别为0.92±0.15和0.50±0.25,差异有统计学意义（t=4.613,P<0.001）;Ktrans以0.12min-1为阈值,诊断敏感度为83%,特异度为86%;Ve以0.88为阈值,敏感度为83%,特异度为85%。结论：采用Ktrans值结合常规MRI序列,对于胶质瘤的分级诊断具有一定的临床应用价值。     

DWI在宫颈癌诊断和放疗后疗效评价中的价值

目的：对宫颈癌组织、正常宫颈、放疗后宫颈癌组织的扩散加权成像（DWI）表现及表观扩散系数（ADC）值进行分析。探讨DWI在宫颈癌诊断以及放疗后疗效监测中的价值。方法：对177例宫颈癌患者、105例正常宫颈对照组和117例放疗后宫颈癌患者进行横断面／矢状面DWI扫描（b取0和500s／ram。）,观察正常宫颈、宫颈癌及放疗后宫颈癌的DwI表现,并测量相应的ADC值,比较正常宫颈腺体和纤维间质的ADC值,宫颈癌与正常宫颈的ADC值,宫颈癌放疗后恢复正常或炎症反应、放疗后肿瘤残存分别与初诊宫颈癌及正常宫颈的ADC值,放疗后肿瘤复发与初诊宫颈癌及放疗后恢复正常或炎症反应的ADC值差异。结果：105例正常宫颈于DWI上呈高-低-稍高信号,宫颈腺体和纤维间质的ADC值差异具有统计学意义（P=0．025）。177例宫颈癌于DWI上呈高信号,其ADc值（1．08±0．36）×10-3mm2／s）低于正常宫颈（P=0．001）。b=500s／mm2时,诊断宫颈癌和正常宫颈的ROC曲线下面积（AUC）为0．806,95％可信区间为0．626～0．985。117例放疗后宫颈癌中,54例宫颈恢复正常或呈炎性反应,其ADC值较初诊宫颈癌高（P=0．000）,与正常宫颈无明显统计学差异（P=0．056）;46例宫颈癌组织残存,其ADC值与初诊宫颈癌无明显统计学差异（P=0．190）,但低于正常宫颈（P=0．000）,17例放疗后宫颈癌复发,其ADC值与初诊宫颈癌无明显统计学差异（P=0．060）,但与放疗后恢复正常或呈炎性反应患者相比具有统计学差异（P=0．002）。结论：DWI能够区分宫颈癌组织和正常宫颈．可用于宫颈癌诊断及预后监测。     

磁共振DWI和PWI在胶质瘤术前分级中的应用研究

目的：通过磁共振扩散加权成像（DWI）和灌注加权成像（PWi）研究肿瘤实性区域的组织扩散和微血管生成情况,探讨DWI和PWI在胶质瘤术前分级中的应用价值。方法：回顾性分析手术病理证实的脑胶质瘤患者常规MRI、DWI和PWI检查资料,按照2000年WHO脑肿瘤分级标准,低级别胶质瘤（Ⅰ～Ⅱ级）22例,高级别胶质瘤（Ⅲ～Ⅳ级）17例。所有病例均术前行DWI扫描,而同时行PWI扫描的有30例,其中低级别胶质瘤和高级别胶质瘤各15例。在工作站构建ADC图和rCBV图,分别测量肿瘤实性区域和相应部位正常参照区域的ADC值和rCBV值,尽可能把ADC值ROI与rCBV值ROI一致,观察高级别胶质瘤组和低级别组肿瘤实性区域ADC值和CBV值与正常对照的相互关系,并着重观察两组肿瘤各自与正常参照区域的相对（肿瘤／参照）ADC（rADC）值和相对CBV（rCBV）值之间的关系以及rADC与rCBV之间的相关性。低级别和高级别胶质瘤之间肿瘤实性区域各项比值的比较均采用两样本t检验。P〈0．05为有统计学差异,P〈0．01时有显著性差异。rADC和rCBV之间采用spearman检验以观察两组间有无相关性。结果：高级别胶质瘤组肿瘤实性区域ADC值（1．27±0．20,×10^-3mm^2／s）较正常对照区（1．10±0．15,×10^-3mm^2／s）稍高,两者之间具有统计学差异（P〈0．05）;而低级别胶质瘤组肿瘤实性区域ADC值（1．84±0．29,×10^-3mm^2／s）明显高于正常对照区（1．00±0．08,×10^-3mm^2／s）,具有显著性差异（P〈0．01）。高级别胶质瘤组rADC值（1．18±0．18）明显低于低级别组（1．82±0．30）,而前者rCBV值（4．14±0．85）明显高于后者（2．51±0．59）,两组之间均具有显著性差异（P〈0．01）。同时,rADC值和rCBV值之间表现为强相关性（r=-0．67,P〈0．01）。结论：高级别胶质瘤与低级别胶质瘤瘤体实性区域rADC值和rC     

比较多层螺旋CT和3.0 T MR成像在肝细胞癌射频治疗疗效评价中的作用

目的 比较多层螺旋CT和3.0T MR在肝细胞癌(HCC)射频消融治疗疗效评价中的价值.方法 回顾性分析2009年12月至2011年9月期间,48例RFA治疗后行CT和MR复查的HCC患者资料,共有56个病灶.2名放射科医师盲法分别对图像进行分析,采用5分制评价肿瘤有无残留或复发,并采用Kappa检验比较诊断结果的一致性;进行ROC曲线分析,计算CT或MR评价HCC RFA术后肿瘤残存或复发的敏感度、特异度和准确度.结果 2名阅片者CT和MR评分的Kappa值分别为0.701和0.925,一致性好.阅片者1评价CT和MR图像诊断HCC射频治疗后肿瘤残存或复发的ROC曲线下面积分别为0.674和0.987,阅片者2分别为0.598和0.971,差异均有统计学意义(P值分别为0.024和0.012).MR图像检测HCC射频治疗后有无肿瘤残存或复发的敏感度、特异度和准确度,两名阅片者的平均值分别是100.0％( 22/22)、95.5％( 86/90)和95.5％(107/112),CT图像分别是40.9％( 9/22)、57.8％( 52/90)和60.7％(68/112).结论 MR在HCC射频治疗后肿瘤残存或复发的检出及诊断的准确性方面部优越于CT.     

肾上腺肿瘤MR扩散加权成像表现与细胞密度相关性的初步研究

目的探讨肾上腺肿瘤MR扩散加权成像（DWI）表现,分析良、恶性肿瘤表观扩散系数（ADC）值之间的差异及ADC值与肿瘤细胞密度的相关性。资料与方法采用屏气单次激发自旋回波-回波平面成像．扩散加权成像（SE-EPI-DWI）技术,分别选取3个不同b值检查4｜D例47个肾上腺肿瘤,其中恶性肿瘤18个,良性肿瘤29个;观察DWI表现,比较ADC值差异,并进行受试者工作特征曲线（ROC）分析,以选取肾上腺肿瘤DWI最佳成像b值和ADC值诊断阈值;对其中27个手术切除的肿瘤,在光镜下计数肿瘤细胞密度,并分析其与ADC值相关性。结果b值的大小影响DWI上肿瘤显示及其信号强度;肾上腺良、恶性肿瘤均可表现为均匀的高信号或不均匀高信号,并与肿瘤的类型及囊变、坏死程度有关,其间ADC值差异有统计学意义。经ROC曲线分析,肾上腺肿瘤DWI最佳成像b值为800s／mm^2,以ADC≥1．21×10^-3mm^2／s为阚值,诊断肾上腺良性肿瘤的敏感性为79％、特异性为72％。肾上腺肿瘤ADC值与其细胞密度负相关,以b值取800s／mm^2时相关性最强（r=-0．723,P〈0．01）。结论DWI对肾上腺肿瘤性质鉴别具有价值,是对常规MR检查的有益补充;测量肿瘤ADC值有可能为在体鉴别肾上腺肿瘤性质和病理分级提供新方法。     

脑转移瘤的灌注成像研究

目的　研究脑转移瘤磁共振灌注成像的表现特点。方法　对 2 0例脑转移瘤患者进行磁共振灌注成像和常规增强扫描 ,以FUNCTOOL作后处理生成rCBV伪彩图 ,测量转移灶的直径和中心、周边实质部分和水肿区的rrCBV ,分析它们的灌注特点。结果　常规图像上共显示转移瘤 5 5个 ,19个表现为不均匀灌注强化 ,3 6个表现为与皮层一致的均匀灌注强度。这两类转移灶的直径之间具有显著性差异。结论　不同大小的转移瘤可以表现出不同的灌注特点。     

Clinical relevance of diffusion and perfusion magnetic resonance imaging in assessing intra-axial brain tumors

Advanced magnetic resonance (MR) imaging techniques provide physiologic information that complements the anatomic information available from conventional MR imaging. We evaluated the roles of diffusion and perfusion imaging for the assessment of grade and type of histologically proven intraaxial brain tumors. A total of 28 patients with intraaxial brain tumors underwent conventional MR imaging (T2- and T1-weighted sequences after gadobenate dimeglumine injection), diffusion imaging and T2*-weighted echo-planar perfusion imaging. Examinations were performed on 19 patients during initial diagnosis and on nine patients during follow-up therapy. Determinations of relative cerebral blood volume (rCBV) and apparent diffusion coefficient (ADC) were performed in the solid parts of each tumor, peritumoral region and contralateral white matter. For gliomas, rCBV values were greater in high-grade than in low-grade tumors (3.87±1.94 versus 1.30±0.42) at the time of initial diagnosis. rCBV values were increased in all recurrent tumors, except in one patient who presented with a combination of recurrent glioblastoma and massive radionecrosis on histology. Low-grade gliomas had low rCBV even in the presence of contrast medium enhancement. Differentiation between high- and low-grade gliomas was not possible using diffusion-weighted images and ADC values alone. In the peritumoral areas of untreated high-grade gliomas and metastases, the mean rCBV values were higher for high-grade gliomas (1.7±0.37) than for metastases (0.54±0.18) while the mean ADC values were higher for metastases. The rCBV values of four lymphomas were low and the signal intensity–time curves revealed a significant increase in signal intensity after the first pass of gadobenate dimeglumine. Diffusion and perfusion imaging, even with relatively short imaging and data processing times, provide important information for lesion characterization.     

Multiparametric 3T MR approach to the assessment of cerebral gliomas: tumor extent and malignancy

Introduction Contrast-enhanced MR imaging is the method of choice for routine assessment of brain tumors, but it has limited sensitivity and specificity. We verified if the addition of metabolic, diffusion and hemodynamic information improved the definition of glioma extent and grade.Methods Thirty-one patients with cerebral gliomas (21 high- and 10 low-grade) underwent conventional MR imaging, proton MR spectroscopic imaging (¹H-MRSI), diffusion weighted imaging (DWI) and perfusion weighted imaging (PWI) at 3 Tesla, before undergoing surgery and histological confirmation. Normalized metabolite signals, including choline (Cho), N-acetylaspartate (NAA), creatine and lactate/lipids, were obtained by ¹H-MRSI; apparent diffusion coefficient (ADC) by DWI; and relative cerebral blood volume (rCBV) by PWI.Results Perienhancing areas with abnormal MR signal showed 3 multiparametric patterns: “tumor”, with abnormal Cho/NAA ratio, lower ADC and higher rCBV; “edema”, with normal Cho/NAA ratio, higher ADC and lower rCBV; and “tumor/edema”, with abnormal Cho/NAA ratio and intermediate ADC and rCBV. Perienhancing areas with normal MR signal showed 2 multiparametric patterns: “infiltrated”, with high Cho and/or abnormal Cho/NAA ratio; and “normal”, with normal spectra. Stepwise discriminant analysis showed that the better classification accuracy of perienhancing areas was achieved when regarding all MR variables, while ¹H-MRSI variables and rCBV better differentiated high- from low-grade gliomas.Conclusion Multiparametric MR assessment of gliomas, based on ¹H-MRSI, PWI and DWI, discriminates infiltrating tumor from surrounding vasogenic edema or normal tissues, and high- from low-grade gliomas. This approach may provide useful information for guiding stereotactic biopsies, surgical resection and radiation treatment.     

Multimodal MRI in the characterization of glial neoplasms: the combined role of single-voxel MR spectroscopy,diffusion imaging and echo-planar perfusion imaging

INTRODUCTION: Diffusion-weighted imaging (DWI), perfusion-weighted imaging (PWI) and MR spectroscopy (MRS) provide useful data for tumor evaluation. To assess the contribution of these multimodal techniques in grading glial neoplasms, we compared the value of DWI, PWI and MRS in the evaluation of histologically proven high- and low-grade gliomas in a population of 105 patients. METHODS: Independently for each modality, the following variables were used to compare the tumors: minimum apparent diffusion coefficient (ADC) and maximum relative cerebral blood volume (rCBV) normalized values between tumor and healthy tissue, maximum Cho/Cr ratio and minimum NAA/Cr ratio in tumor, and scored lactate and lipid values in tumor. The Mann-Whitney and Wilcoxon tests were employed to compare DWI, PWI and MRS between tumor types. Logistic regression analysis was used to determine which parameters best increased the diagnostic accuracy in terms of sensitivity, specificity, and positive and negative predictive values. ROC curves were determined for parameters with high sensitivity and specificity to identify threshold values to separate high- from low-grade lesions. RESULTS: Statistically significant differences were found for rCBV tumor/normal tissue ratio, and NAA/Cr ratio in tumor and Cho/Cr ratio in tumor between low- and high-grade tumors. The best performing single parameter for group classification was the normalized rCBV value; including all parameters, statistical significance was reached by rCBV tumor/normal tissue ratio, NAA/Cr tumor ratio and lactate. From the ROC curves, a high probability for a neoplasm to be a high-grade lesion was associated with a rCBV tumor/normal tissue ratio of >1.16 and NAA/Cr tumor ratio of <0.44. CONCLUSION: Combining PWI and MRS with conventional MR imaging increases the accuracy of the attribution of malignancy to glial neoplasms. The best performing parameter was found to be the perfusion level.     

Comparison of relative cerebral blood volume and proton spectroscopy in patients with treated gliomas

BACKGROUND AND PURPOSE: Elevated relative regional cerebral blood volume (rCBV) reflects the increased microvascularity that is associated with brain tumors. The purpose of this study was to investigate the potential role of rCBV in the determination of recurrent/residual disease in patients with treated gliomas. METHODS: Thirty-one rCBV studies were performed in 19 patients with treated gliomas. All patients also had proton MR spectroscopy and conventional MR imaging. Regions of abnormality were identified on conventional MR images by two neuroradiologists and compared with rCBV and MR spectroscopic data. Metabolites and rCBV were quantified and compared in abnormal regions. RESULTS: In high-grade tumors, rCBV values were proportional to choline in regions of tumor and nonviable tissue. Although the presence of residual/recurrent disease was often ambiguous on conventional MR images, the rCBV maps indicated regions of elevated vascularity in all low-grade tumors and in 12 of 17 grade IV lesions. Regions of elevated and low rCBV corresponded well with spectra, indicating tumor and nonviable tissue, respectively. CONCLUSION: This study suggests that rCBV maps and MR spectroscopy are complementary techniques that may improve the detection of residual/recurrent tumor in patients with treated gliomas. Compared with the spectra, the rCBV maps may better reflect the heterogeneity of the tumor regions because of their higher resolution. The multiple markers of MR spectroscopy enable better discrimination between normal and abnormal tissue than do the rCBV maps.     

Dynamic susceptibility contrast-enhanced perfusion and conventional MR imaging findings for adult patients with cerebral primitive neuroectodermal tumors

BACKGROUND AND PURPOSE: Preoperative differentiation of primitive neuroectodermal tumors (PNETs) from other tumors is important for presurgical staging, intraoperative management, and postoperative treatment. Dynamic, susceptibility-weighted, contrast-enhanced MR imaging can provide in vivo assessment of the microvasculature in intracranial mass lesions. The purpose of this study was to determine the perfusion characteristics of adult cerebral PNETs and to compare those values with low and high grade gliomas. METHODS: Conventional MR images of 12 adult patients with pathologically proved cerebral PNETs were analyzed and provided a preoperative diagnosis. Relative cerebral blood volume (rCBV) measurements and estimates of the vascular permeability transfer constant, K(trans), derived by a pharmacokinetic modeling algorithm, were also obtained. These results were compared with rCBV and K(trans) values obtained in a group of low grade gliomas (n = 30) and a group of high grade gliomas (n = 55) by using a Student t test. RESULTS: On conventional MR images, PNETs were generally well-defined contrast-enhancing masses with solid and cystic components, little or no surrounding edema, and occasional regions of susceptibility. The rCBV of cerebral PNETs was 4.76 +/- 1.99 SD, and the K(trans) was 0.0033 +/- 0.0035. A comparative group of patients with low grade gliomas (n = 30) had significantly lower rCBV (P <.0005) and lower K(trans) (P <.05). Comparison with a group of high grade gliomas showed no statistical significance in the rCBV and K(trans) (P =.53 and.19, respectively). CONCLUSION: Dynamic, susceptibility-weighted, contrast-enhanced MR imaging shows areas of increased cerebral blood volume and vascular permeability in PNETs. These results may be helpful in the diagnosis and preoperative differentiation between PNETs and other intracranial mass lesions (such as low grade gliomas), which have decreased perfusion but may sometimes have a similar conventional MR imaging appearance.     

Measurement of cerebral hemodynamics with perfusion-weighted MR imaging: comparison with pre- and post-acetazolamide 133Xe-SPECT in occlusive carotid disease

BACKGROUND AND PURPOSE: We generated regional cerebral blood volume (rCBV) and regional cerebral blood flow (rCBF) studies from dynamic susceptibility contrast-enhanced MR images after an intravenous bolus injection of contrast agent (perfusion-weighted imaging [PWI]) by applying indicator dilution theory. We used a multishot echo-planar imaging (EPI) sequence to obtain adequate arterial input function (AIF). Our purpose was to compare the cerebral hemodynamics measured by PWI with the rCBF values and cerebral perfusion reserve obtained by xenon-133 single-photon emission CT (133Xe-SPECT). METHODS: Eight patients with chronic internal carotid artery occlusion or stenosis were examined. PWI data were acquired using a multishot EPI sequence, and the AIF was determined automatically. Our procedure was based on indicator dilution theory and deconvolution analysis. To eliminate the effect of superficial vessels, the automatic threshold selection method was used. RESULTS: AIF was adequate to generate rCBF and rCBV images. The rCBF and rCBV images by PWI were superior to 133Xe-SPECT scans in spatial resolution, and the rCBF values obtained by PWI correlated well with those obtained by 133Xe-SPECT. The regions with severely decreased perfusion reserve, which were determined by pre- and post-acetazolamide 133Xe-SPECT, showed significantly lower rCBF and higher rCBV by PWI than did regions with normal and moderately decreased perfusion reserve. CONCLUSION: The rCBF and rCBV images generated by our procedure using PWI data appear to provide important clinical information for evaluating the degree of cerebral perfusion reserve impairment in patients with chronic ischemia.     

Perfusion magnetic resonance imaging and magnetic resonance spectroscopy of cerebral gliomas showing imperceptible contrast enhancement on conventional magnetic resonance imaging

The purpose of the present paper was to evaluate the utility of perfusion MRI in cerebral gliomas showing imperceptible contrast enhancement on conventional MRI, and to evaluate the relationships of perfusion MRI and magnetic resonance (MR) spectroscopic results in these tumours. Twenty-two patients with histopathologically proven cerebral gliomas and showing insignificant contrast enhancement on conventional MR were included in the present study. All patients underwent perfusion MRI and MR spectroscopy on a 1.5-T MR system. Significant differences of the relative cerebral blood volume (rCBV) values and the choline : creatine ratios were noted between low-grade and anaplastic gliomas (P < 0.01). Good correlation was found between the rCBV values and the choline : creatine values (y = 0. 532x + 1.5643; r = 0.67). Perfusion MRI can be a useful tool in assessing the histopathological grade of non-contrast-enhancing cerebral gliomas. Along with MR spectroscopic imaging it can serve as an important technique for preoperative characterization of such gliomas, so that accurate targeting by stereotactic biopsies is possible.     

Postoperative fluid-attenuated inversion recovery MR imaging of cerebral gliomas: initial results

Fluid-attenuated inversion-recovery (FLAIR) imaging has shown to be a valuable imaging modality in the assessment of intra-axial brain tumors; however, no data are available about the role of this technique in the clinically important postoperative stage. The purpose of this study was to evaluate the diagnostic potential of FLAIR MR imaging in residual tumor after surgical resection of cerebral gliomas. Fifteen patients with residual cerebral gliomas were examined within the first 18 days after partial surgical resection of cerebral gliomas. The imaging protocol included T1-weighted spin echo, T2- and proton-density-weighted fast spin echo, and FLAIR imaging with identical slice parameters. T1 and FLAIR were repeated after contrast media application. Detection and delineation of residual tumor were the primary parameters of the image analysis. Additionally, the influence of image artifacts on the image interpretation was assessed. On FLAIR images residual signal abnormalities at the border of the resection cavities were observed in all patients, whereas T2- and T1-weighted images present residual abnormalities in 13 of 15 and 10 of 15 patients, respectively. The FLAIR imaging was found to be superior to conventional imaging sequences in the delineation of these changes and comparable to contrast enhanced T1-weighted imaging in the delineation of residual enhancing lesions. Because of protein cell components and blood byproducts within the resection cavity, FLAIR imaging was unable to suppress the cerebrospinal fluid (CSF) in 4 patients. After the decomposition of proteins and blood, CSF could again be completely suppressed and residual or recurrent tumors were clearly identified. Our preliminary study has shown that FLAIR may be a valuable diagnostic modality in the early postoperative MR imaging after resection of cerebral gliomas due to its better delineation of residual pathologic signal at the border of the resection cavity. It should therefore be integrated into the early and/or intraoperative MR imaging protocol.