Diffusion- and perfusion-weighted MRI in a patient with a prolonged reversible ischaemic neurological deficit

We report acute and follow-up diffusion- and perfusion-weighted MRI (DWI, PWI) findings in a patient with a prolonged reversible ischaemic neurological deficit. PWI 12 h after the patient was last seen to be without symptoms revealed a large perfusion deficit in the left posterior MCA territory with a relatively inconspicuous and much smaller abnormality on DWI. Follow-up showed resolution of abnormalities on both DWI and PWI, and conventional MRI was normal, apart from a very slight abnormality, visible only on FLAIR images, at the centre of the initially DWI-positive region. These findings demonstrate the utility of PWI when be used in combination with DWI to investigate the pathophysiology of transient ischemic syndromes. Received: 26 July 1999/Accepted: 20 September 1999     

Usefulness of diffusion/perfusion-weighted MRI in rat gliomas: correlation with histopathology

RATIONALE AND OBJECTIVES: Diffusion/perfusion-weighted MRI (DWI/PWI) can provide additional useful information in the diagnosis of patients with brain gliomas in a noninvasive fashion. However, the exact role of these new techniques is still undergoing evaluation. Our hypothesis was that DWI and PWI could be useful for assessment of growth and vascularity of implanted C6 rat gliomas. MATERIALS AND METHODS: Thirty-six rats were implanted with C6 glioma cells intracerebrally. Between 1 and 4 weeks after implantation, 8-10 rats were imaged on a clinical, 1.5-T whole-body magnetic resonance system with T(1)-weighted imaging (T(1)WI), T(2)-weighted imaging, DWI, PWI, and postcontrast T(1)WI at each weekly time point. All tumors were examined histologically; tumor cellularity and microvascular density were counted. RESULTS: On DWIs, statistical differences of apparent diffusion coefficient values for both the tumoral core and peritumoral region were present comparing tumors of 3-4 weeks' growth with tumors of 1-2 weeks' growth. Apparent diffusion coefficient value of tumoral core was negatively correlated with tumor cellularity (r = -0.682, P < .01). Statistical difference of maximal regional cerebral blood volume of tumoral core was present comparing 2-4 weeks with both 1 week after implantation and contralateral white matter (P < .01). Native vessel dilation in regions of normal brain at the periphery of the tumors at 1 week after implantation was observed. Correlation between maximal regional cerebral blood volume of tumor core and microvascular density was present (r = 0.716, P < .01). CONCLUSION: DWI and PWI has potential to characterize C6 gliomas in rats, which is a promising model similar to human gliomas.     

磁共振DWI和PWI在超急性脑梗死诊治中的应用

目的评价磁共振弥散加权成像（DWI）和灌注加权成像（PWI）在超急性脑梗死诊断及指导临床早期溶栓治疗中的应用价值。方法 56例发病在6 h以内且临床提示处于超急性期脑梗死患者均行急诊MRI检查,扫描序列包括T1WI、T2WI、FLAIR、DWI及PWI,部分病例行MRA检查。结果 56例患者T1WI均未见异常信号,35例患者T2WI、FLAIR发现有轻微异常信号影。56例DWI和PWI均发现异常,但在DWI上显示的高信号急性脑梗死区域与在PWI上显示的脑灌注延长区域不匹配,PWI显示的病灶范围更大。图像后处理显示平均通过时间（MTT）、达峰时间（TTP）均有不同程度的延长,脑血流量（CBF）出现不同程度的减少。结论急诊MRI,特别是DWI和PWI序列对超急性脑梗死患者可以作出准确的诊断,可以安全、迅速、有效地指导临床进行早期溶栓治疗。     

脑梗死前期MR脑灌注成像和弥散成像诊断的研究

目的:研究提高对脑梗死前期的诊断水平,减少脑梗死的发生。材料和方法:由于对比增强磁共振脑灌注成像在脑缺血诊断中具有较为敏感的特点,用此技术及弥散加权和常规MRI技术对18例脑缺血患者和20例非脑血管病患者进行脑梗死前期诊断的对比分析研究。结果:在T1WI、T2WI、FLAIR、MRA、DWI和PWI六种MR成像技术中,仅有脑灌注成像可以检出脑梗死前期病例,余均不能检出。结论:脑梗死前期的MR灌注成像可有效地检出脑梗死前期病例,是目前比较理想的功能性磁共振检查方法。     

急性脑缺血再灌注DWI及PWI的实验研究

目的:评价DWI及PWI判定急性脑梗死诊断及缺血半暗带的作用。材料和方法:40只SD大鼠随机均分4组,A组作假手术对照;B、D组分别栓塞2h、6h,均再灌注2h、24h;C组栓塞2h再灌注24h、7d。B、C、D组于各自栓塞及再灌注时间点行DWI、PWI及常规序列扫描;后处理获得表观扩散系数(ADC)、脑血容量(CBV)、脑血流量(CBF)、平均通过时间(MTT)形态图。并将结果与四氮唑红(TTC)染色和病理作比较。结果:A组DWI、PWI、TTC染色及病理观察均无异常;B、C、D组栓塞时均可见右大脑中动脉供血区DWI呈高信号,D组异常信号区面积明显大于B组,病理电镜表现为细胞内水肿。B、D组再灌注24hDWI异常信号区面积与灌注前相比,B组无明显变化,D组较前增大;C组再灌注7d6只大鼠DWI见高信号,但ADC图均正常。B、D组栓塞时右大脑中动脉供血区PWI灌注缺损区面积相似。B组PWI异常信号面积大于DWI异常信号区;D组PWI与DWI异常信号面积无明显差别。结论:DWI能灵敏反映急性期缺血脑组织损伤情况,PWI能灵敏反映组织血流灌注情况。DWI、PWI联合应用有可能判定缺血半暗带。     

MRI in acute subarachnoid haemorrhage; findings with a standardised stroke protocol

There is doubt as to whether acute haemorrhage is visible on MRI. We carried out MRI within 6 h of symptom onset on five patients with minor (low Hunt and Hess grades 1 or 2) subarachnoid haemorrhage (SAH) diagnosed by CT to search for any specific pattern. We used our standard stroke MRI protocol, including multiecho proton density (PD)- and T2-weighted images, echoplanar (EPI) diffusion- (DWI) and perfusion- (PWI) weighted imaging, and MRA. In all cases SAH was clearly visible on PD-weighted images with a short TE. In four patients it caused a low-signal rim on the T2*-weighted source images of PWI, and DWI revealed high signal in SAH. In the fifth patient SAH was perimesencephalic; susceptibility effects from the skull base made it impossible to detect SAH on EPI DWI and T2*-weighted images. Perfusion maps were normal in all cases. MRA and conventional angiography revealed an aneurysm in only one patient. Stroke MRI within 6 h of SAH thus shows a characteristic pattern.     

术后瘢痕组织病理模型的制备及MRI初步研究

目的：制备术后瘢痕组织病理模型,研究术后瘢痕组织病理模型的MRI表现.方法：20只新西兰大白兔用于制备术后瘢痕组织,在无菌环境下,钝性分离其后大腿的肌梭,植入折叠后大小约3 cm×3 cm的无菌纱布.术后两周取出植入的纱布.观察3周后行MRI扫描,扫描序列为SE序列T1WI、FRFSE序列T2WI、SE-EPI序列DWI和3D-FSPGR序列PWI.扫描结束后处死兔子,取瘢痕组织行常规病理学检查.结果：20只兔子术后瘢痕组织模型的制备均成功,制备的瘢痕组织的病理表现与增生性瘢痕的表现相似.MRI平扫T1WI上呈中等及稍高信号,T2WI呈高信号;在DWI上呈混杂高信号,瘢痕组织的ADC值小于正常肌肉组织;灌注成像（PWI）上其时间-信号强度曲线12例呈缓慢上升型,8例曲线升支较陡直、升至峰值后持续在较高水平.瘢痕组织和正常肌肉组织之间的Emax值和Es值存在明显差异.结论：钝性分离肌肉组织植入纱布刺激瘢痕组织增生是一种制备术后瘢痕组织模型的有效造模方法,瘢痕组织的MRI表现在一定程度上可以反映其病理学特点.     

大鼠肝肿瘤模型建立及磁共振新技术表现

目的建立大鼠种植性肝肿瘤模型,并研究磁共振影像学表现。方法(1)选择体重约250~300g SD大鼠50只,将肿瘤细胞混悬液种植到大鼠肝叶中;(2)肝肿瘤形成后进行磁共振各序列(MRI,DWI,MRS,PWI)检查;(3)肿瘤组织送病理学检查及电镜检查;(4)将磁共振与病理学检查对照分析。结果(1)大鼠肝肿瘤种植成功率100%;(2)HE染色肿瘤组织呈岛状,内见小片坏死灶,血管内皮细胞生成因子(VEGF)及增殖细胞核抗原(PCNA)染色表达阳性,CD34染色微血管数增多,电镜清晰显示肿瘤的超微结构;(3)T1WI呈低信号,T2WI及DWI呈高信号,表观弥散系数(apparent diffusion coefficient,ADC)减低;胆碱(Choline,Cho)、肌酸(Creatine,Cr)、谷氨酸(Glutamate,Glx)、乳酸(Lactate,Lac)及脂质(Lipid,Lip)峰均明显增高;PWI示肿瘤血供丰富,最大相对信号强度增减率(MRSI)明显增高,并与VEGF及CD34呈正相关关系。结论肿瘤细胞混悬液种植可成功制备大鼠肝肿瘤模型,磁共振成像检查肿瘤有特异性表现。     

Diffusion- and perfusion-weighted MRI in therapeutic neurointerventional procedures

We describe three patients in whom we used MRI, including diffusion- and perfusion-weighted imaging (DWI, PWI) in conjunction with endovascular therapy. Two had intracranial aneurysms and one an arteriovenous malformation (AVM). The aneurysms were treated by coil embolisation or detachable balloons for proximal artery occlusion; the AVM was obliterated by intranidal glue injection. All patients had transient or permanent neurological deficits after treatment. The MRI techniques and interventional procedures are described and the DWI and PWI patterns found are correlated with the clinical features. We discuss how the information gained from MRI may increase our understanding of procedure-related complications and its potential impact on our therapeutic interventions, in order to prevent or limit the clinical consequences of such events. Received: 7 April 2000 Accepted: 19 December 2000     

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.     

Prognostic value of perfusion- and diffusion-weighted MR imaging in first 3 days of stroke

The aim of this study was to evaluate the differences in cerebral perfusion seen on mean transit time (MTT) and cerebral blood volume (CBV) maps and to assess the subsequent prognostic value of the MTT–DWI (diffusion-weighted MRI) and CBV–DWI mismatch in the first three days of stroke on lesion enlargement and clinical outcome. In 38 patients, imaged 1–46 h after onset of symptoms, lesion volumes on proton-density (PD)-weighted MRI, DWI and PWI (both MTT and CBV maps) were compared with lesion volumes on follow-up PD-weighted scans, and to clinical outcome (National Institutes of Health Stroke Scale, Barthel index, and Rankin scale). The MTT-CBV, MTT–DWI and CBV–DWI mismatches were compared with change in lesion volume between initial and follow-up PD-weighted scans. Lesion volume on both DWI and PWI correlated significantly with clinical outcome parameters (p < 0.001) with strongest correlation for lesion volume on CBV. Perfusion–diffusion mismatches were found for both CBV and MTT and correlated significantly with lesion enlargement on PD-weighted imaging with strongest correlation for the CBV–DWI mismatch. The CBV–DWI mismatch has the highest accuracy in predicting lesion size on follow-up imaging and in predicting clinical outcome. Lesion volume measurements on CBV maps have a higher specificity than on PD-weighted, MTT or DWI images in predicting clinical follow-up imaging and in predicting clinical outcome. Received: 21 January 2000; Revised: 18 April 2000; Accepted: 20 April 2000     

脑缺血再灌注大鼠模型FAIR-PWI研究

目的:探讨流动敏感交替反转恢复序列灌注成像(FAIR- PWI)对大鼠脑缺血后再灌注的评价.方法:使用GE 3.0T MRI成像仪,在完成T1WI、T2WI、弥散加权成像(DWI)和FAIR - PWI序列后,对SD大鼠行暂时性右侧大脑中动脉闭塞(TMCAO)手术,分别在脑缺血3h和再灌注3h及21h行重复上述MRI检查;最后进行病理学TTC染色观察梗死区域及范围.结果:TMCAO后3h时,患侧大脑半球DWI信号升高、FAIR - PWI灌注增加、且皮质相对脑血流量(rCBF)大于基底节区;再灌注3h及21h后,患侧大脑半球DWI信号面积(0.63±0.1.2cm2、0.48±0.23cm2)仍高于FAIR - PWI高灌注面积(0.51±0.26cm2、0.34±0.44cm2,P=0.01),皮质及基底节区rCBF较缺血时增加.TTC染色示梗死面积(0.42±0.78cm2)小于DWI异常信号面积,而大于FAIR - PWI高灌注面积,且梗死区以基底节为主.结论: FAIR- PWI结合DWI能对早期缺血再灌注进行动态观察及半定量测量,可能为临床溶栓治疗方案的预后判断和随访提供重要参考.     

Relationship between sodium intensity and perfusion deficits in acute ischemic stroke

Purpose

To assess the relationship between sodium signal intensity changes and oligemia, measured with perfusion‐weighted imaging (PWI), in ischemic stroke patients.

Materials and Methods

Nine ischemic stroke patients (55 ± 13 years), four with follow‐up scans, underwent sodium and proton imaging 4–32 hours after symptom onset. Relative sodium intensity was calculated as the ratio of signal intensities in core (identified as hypertintense lesions on diffusion‐weighted imaging [DWI]) or putative penumbra (PWI‐DWI mismatch) to contralateral homologous regions.

Results

Sodium intensity increases in the core were not correlated with the severity of hypoperfusion, measured with either cerebral blood flow (rho = 0.157; P = 0.61) or cerebral blood volume (rho = ?0.234; P = 0.44). In contrast, relative sodium intensity was not elevated (4–7 hours 0.96 ± 0.07; 17–32 hours 1.00 ± 0.07) in PWI‐DWI mismatch regions.

Conclusion

Sodium signal intensity cannot be predicted by the degree of hypoperfusion acutely. Sodium intensity also remains unchanged in PWI‐DWI mismatch tissue, indicating preservation of ionic homeostasis. Sodium magnetic resonance imaging (MRI), in conjunction with PWI and DWI, may permit identification of patients with viable tissue, despite an unknown symptom onset time. J. Magn. Reson. Imaging 2011;33:41–47. © 2010 Wiley‐Liss, Inc.

     

3.0T磁共振脑转移瘤IVIM与MR灌注加权成像的相关性研究

目的初步探讨利用体素内不一致运动磁共振成像(introvoxelincoherent motion MR imaging,IVIM-MRI)评价脑转移瘤的灌注,并与灌注加权成像(perfusion weighted Imaging,PWI)的指标进行相关性评价。方法收集在本院2012年6月~2012年12月间26例经手术证实的不同类型癌症发生脑转移的患者行MRI增强检查。扫描序列包括IVIM及PWI。选取颅内转移病灶共60个,应用工作站后处理软件分别测定瘤体及对侧Slow ADC(SADC)、Fast ADC(FADC)、Fraction of FastADC(FFADC)和血流量(cerebral blood flow,CBF)、血容量(cerebral blood volume,CBV),并计算出各个参数的相对值(r),即:r值=(实质病灶值/对侧正常值)×100%。将瘤体与正常侧的IVIM指标进行统计学比较,并将IVIM与PWI的各参数进行Pearson相关性分析。对IVIM和PWI的参数进行转移瘤诊断的ROC分析。结果转移瘤的SADC为(0.437±0.023)×10-3 mm2/s),其对侧脑组织的SADC为(0.223±0.010)×10-3 mm2/s),两者间差异有统计学意义(t=4.83,P0.01);转移瘤的FADC为(3.65±0.11)×10-3 mm2/s),其对侧脑组织的FADC为(2.27±0.12)×10-3 mm2/s),两者间差异有统计学意义(t=8.36,P0.05);转移瘤的FFADC为441.67×10-3±21.19×10-3,其对侧脑组织的FFADC为276.5×10-3±8.07×10-3,两者间差异有统计学意义(t=7.28,P0.01)。转移瘤的rFADC为5.57±31.66,rCBV为2.79±1.27,Person相关性分析显示rFADC与rBV呈弱相关(r=0.274,P0.05),而rFFADC、rSADC与rCBF、rCBV无明显相关性。FADC、FFADC、SADC、CBF、CBV的ROC曲线分析显示,AUCFADC=0.924(P=0.025);AUCFFADC=0.860(P=0.034);AUCSADC=0.896(P=0.030);AUCCBF=0.849(P=0.035);AUCCBV=0.865(P=0.034)。FADC的ROC曲线的AUC最大,诊断准确性更高。结论 IVIM的参数测量能反映转移瘤的灌注特性,但是由于与PWI的技术原理不同,灌注的测量指标之间只具有弱相关性。     

Temporal evolution of MR perfusion in neonatal hypoxic-ischemic encephalopathy

PURPOSE: To illustrate the evolution of brain perfusion-weighted magnetic resonance imaging (PWI-MRI) in severe neonatal hypoxic-ischemic (HI) encephalopathy, and its possible relation to further neurodevelopmental outcome. MATERIALS AND METHODS: Two term neonates with HI encephalopathy underwent an early and a late MRI, including PWI. They were followed until eight months of age. A total of three "normal controls" were also included. Perfusion maps were obtained, and relative cerebral blood flow (rCBF) and cerebral blood volume (rCBV) values were measured. RESULTS: Compared to normal neonates, a hyperperfusion (increased rCBF and rCBV) was present on early scans in the whole brain. On late scans, hyperperfusion persisted in cortical gray matter (normalization of rCBF and rCBV ratios in white matter and basal ganglia, but not in cortical gray matter). Diffusion-weighted imaging (DWI) was normalized, and extensive lesions became visible on T2-weighted images. Both patients displayed very abnormal outcome: Patient 2 with the more abnormal early and late hyperperfusion being the worst. CONCLUSION: PWI in HI encephalopathy did not have the same temporal evolution as DWI, and remained abnormal for more than one week after injury. This could be a marker of an ongoing mechanism underlying severe neonatal HI encephalopathy. Evolution of PWI might help to predict further neurodevelopmental outcome.     

软组织肿瘤MR扩散成像与灌注成像的比较研究

目的 通过分析一组软组织肿瘤同一病例相同ROI的MR DWI及PWI的影像信息,比较这2种MR功能成像技术用于软组织肿瘤的定性诊断价值.方法 对50例软组织肿瘤(良性24例,恶性26例)同时行DWI及PWI.通过扩散及灌注软件分析DWI及PWI参数在良、恶性肿瘤中的表现,进行差异的t检验,对所获两法的诊断符合率进行x2检验.采用受试者操作特征曲线(ROC曲线)分析曲线下面积(AUC),确定诊断阈值并对2种诊断方法进行评价.结果 良、恶性软组织肿瘤的ADC值[(良、恶性分别为(2.03±0.36)和(1.52±0.39)×10-3mm2/s]、首过灌注(FP)期信号强度丢失率[良、恶性分别为(13.54±3.37)%和(47.57±5.21)%]的差异均有统计学意义(t值分别为2.515和2.938,P值均<0.05),时间-信号强度曲线(TIC)最大线性斜率[良、恶性分别为(5.51±2.54)%和(7.94±3.33)%]的差异无统计学意义(t值为1.272,P>0.05);以ADC值1.866×10-3mm2/s为阈值,DWI诊断恶性肿瘤的敏感度为84.6%(22/26),特异度为83.3%(20/24);以FP期最大信号丢失率40.33%为阈值,PWI诊断恶性肿瘤的敏感度为88.5%(23/26),特异度为75.0%(18/24);TIC类型的Ⅰa型在良性肿瘤中占3/24,在恶性肿瘤中占20/26;Ⅰb型在良性肿瘤中占14/24,在恶性肿瘤中占3/26;Ⅰc型在恶性肿瘤中占3/26.Ⅱ型TIC在良性肿瘤中占7/24.在DWI上用ADC值、PWI上用FP期最大信号强度丢失率作诊断,诊断符合率分别为84.0%(42/50)和82.0%(41/50),两者的差异无统计学意义(x2=0.8,P>0.05);AUC测得的准确度分别为81.7%和83.6%,PWI诊断恶性软组织肿瘤的敏感度高.结论 以DWI和PWI的ADC值、FP期信号强度丢失率分别为1.866×10-3mm2/s和40.33%为阈值时,均有利于软组织肿瘤良、恶性的鉴别;TIC最大线性斜率对于软组织肿瘤良、恶性的鉴别意义不大;软组织肿瘤的TIC形态有助于肿瘤良、恶性的鉴别.DWI和PWI用于诊断恶性软组织肿瘤的准确性均为中等,在DWI与PWI用于诊断恶性软组织肿瘤的准确性相近时,应选择诊断敏感度较高的PWI.     

MRI弥散和灌注成像诊断超早期脑梗死的实验研究

目的评价磁共振弥散成像(DWI)和灌注成像(PWI)技术在超早期脑梗死中的诊断价值。方法新西兰白兔42只,随机分为7组,其中6组为实验组,1组为假手术组。采用改良O’Brein法闭塞兔一侧大脑中动脉制作局灶性脑缺血模型,对照组仅暴露同侧大脑中动脉,不予电凝。术后0.5、1、2、3、4、6 h不同时间段进行MRI扫描。结果常规MR序列显示缺血病灶明显晚于DWI和PWI。随着时间延长病灶各参数有特征性变化规律。在DWI和PWI中缺血区体积均随时间的延长不断扩大,两者不匹配区随时间延长逐渐缩小。结论DWI和PWI在诊断超早期脑梗死上优于常规MR序列。     

Perfusion-weighted MRI as a marker of response to treatment in acute and subacute stroke

We carried out baseline and short-term follow-up MRI, including perfusion-weighted imaging (PWI) and tests of neurologic and cognitive function on 15 consecutive patients with large-vessel ischemic stroke who showed a persistent large perfusion-diffusion mismatch at enrollment up to seven days after the onset of symptoms. Of these, ten underwent induced blood pressure elevation with phenylephrine and oral medications (in eight) or intravenous fluids (in two) with the goal of improving perfusion; five had no such treatment. Significant functional improvement was defined by a reduction of 3 or more points on the NIH stroke scale (NIHSS). Significant improvement in perfusion was defined by a reduction in the volume of hypoperfused brain by 30 cc on PWI using time-to-peak (TTP) maps, without enlargement of the infarct. There was a strong, statistically significant association between improved function and improved perfusion: six (75%) of eight patients who improved in function, but none of the seven who did not, showed a reduction in volume of hypoperfused brain. All six patients who met the perfusion goal, and only two (22%) of nine who did not showed significant functional improvement (Fishers exact: P <0.01). There were no differences between patients who improved functionally and those who did not with respect to age, initial volume of abnormality on DWI or PWI, initial NIHSS, or changes on DWI. These findings indicate that reduction in volume of hypoperfused brain on PWI is a marker of response to treatment to improve perfusion even in subacute stroke and that partial reperfusion of regions of salvageable but dysfunctional tissue is a mechanism of improved function associated with induced blood pressure elevation.     

Diffusion-weighted MR imaging in the early diagnosis of periventricular leukomalacia

Diffusion-weighted imaging (DWI) has been shown to be highly sensitive in detecting acute cerebral infarction, but its use in detecting hypoxic–ischemic encephalopathy (HIE) in neonates is still controversial. Moreover, few reports concern pre-term infants with possible periventricular leukomalacia (PVL). We examined the ability of this technique to detect cerebral changes in the acute phase of PVL. Fifteen MR examinations were performed in 11 pre-term infants (mean age 3.4 days, range 2–6 days). Conventional DWI sequences, apparent diffusion coefficient (ADC) maps, and US obtained in the acute phase were compared. All the neonates underwent US follow-up up to 4 months after delivery; those with suspected PVL also underwent MRI follow-up for up to 2 months. Qualitative and quantitative evaluations were performed to assess the presence of DW changes compatible with PVL. Diffusion-weighted MRI showed signal hyperintensity associated with decreased ADC values in 3 subjects (27%). In these patients conventional MRI sequences were interpreted as normal and US (performed at the same time) as doubtful in 2 and compatible with PVL in 1 subject. The MRI and US follow-up confirmed severe damage in all these patients. In 1 neonate hemorrhages involving the germinative matrix were identified. In 8 neonates MRI was considered normal. In these subjects US follow-up (up to 4 months) confirmed no signs of PVL. Diffusion-weighted imaging may have a higher correlation with later evidence of PVL than does conventional MR imaging and US when performed in the acute phase of the disease.     

The role of diffusion-weighted imaging and the apparent diffusion coefficient (ADC) values for breast tumors.

OBJECTIVE: We wanted to evaluate the role of diffusion-weighted imaging (DWI) and the apparent diffusion coefficient (ADC) for detecting breast tumors, as compared with the T1- and T2-weighted images. MATERIALS AND METHODS: Forty-one female patients underwent breast MRI, and this included the T1-, T2-, DWI and dynamic contrast-enhanced images. Sixty-five enhancing lesions were detected on the dynamic contrast-enhanced images and we used this as a reference image for detecting tumor. Fifty-six breast lesions were detected on DWI and the histological diagnoses were as follows: 43 invasive ductal carcinomas, one mucinous carcinoma, one mixed infiltrative and mucinous carcinoma, seven ductal carcinomas in situ (DCIS), and four benign tumors. First, we compared the detectability of breast lesions on DWI with that of the T1- and T2-weighted images. We then compared the ADCs of the malignant and benign breast lesions to the ADCs of the normal fibroglandular tissue. RESULTS: Fifty-six lesions were detected via DWI (detectability of 86.2%). The detectabilities of breast lesions on the T1- and T2-weighted imaging were 61.5% (40/65) and 75.4% (49/65), respectively. The mean ADCs of the invasive ductal carcinoma (0.89+/-0.18 x 10(-3)mm(2)/second) and DCIS (1.17+/-0.18 x 10(-3)mm(2)/ second) are significantly lower than those of the benign lesions (1.41+/-0.56 x 10(-3)mm(2)/second) and the normal fibroglandular tissue (1.51+/-0.29 x 10(-3)mm(2)/ second). CONCLUSION: DWI has a high sensitivity for detecting breast tumors, and especially for detecting malignant breast tumors. DWI was an effective imaging technique for detecting breast lesions, as compared to using the T1- and T2-weighted images.