注射钆剂后弥散加权成像对乳腺肿瘤诊断的影响

目的：评估1.5 T MRI中乳腺肿瘤患者使用钆对比剂是否对弥散加权成像（DWI）有显著性影响。方法行乳腺MRI检查的女性患者40例（共计44个病灶）,分别测量增强前后DWI图像信噪比（SNR）和对比噪声比（CNR）、病灶增强前后的表观扩散系数（ADC）及指数表观扩散系数（eADC）。结果给药前后DWI图像的SNR及CNR差异无统计学意义。乳腺癌给药前后的ADC值（t=-4.023, P=0.001）及eADC值（t=4.082, P=0.001）差异有统计学意义,良性肿瘤给药前后的ADC值（t=-1.700, P=0.103）及eADC值（t=1.341, P=0.194）差异无统计学意义。结论增强后行DWI是可行的,并且有助于提高其鉴别乳腺良恶性肿瘤的能力。     

The effect of using Gd-DTPA as contrast medium on diffusion weighted imaging for extrahepatic cholangiocarcinoma

目的:探讨对比剂钆喷替酸葡甲胺(Gd-DTPA)对肝外胆管癌磁共振扩散加权成像(DWI)图像质量及表观扩散系数(ADC)的影响.方法:回顾性分析经病理证实并被DWI检出的57例肝外胆管癌患者的DWI图像资料,比较静脉注射对比剂Gd-DTPA增强前后及不同b值条件下肝外胆管癌病灶信噪比(SNR)、病灶与正常肝脏间对比信噪比(CNR)及ADC值的差异.结果:同一b值条件下,增强前后病灶SNR、CNR、ADC值的差异均无统计学意义(P＞0.05);增强前后肝外胆管癌病灶SNR、CNR及ADC值均随着b值的增大而降低,其差异均有统计学意义(P＜0.05).结论:肝外胆管癌病灶的DWI图像质量及ADC值不受Gd-DTPA影响,所以选择合适b值的增强后DWI序列是可行的.     

对比剂Gd-DTPA对肝外胆管癌磁共振扩散加权成像的影响

目的:探讨对比剂钆喷替酸葡甲胺(Gd-DTPA)对肝外胆管癌磁共振扩散加权成像(DWI)图像质量及表观扩散系数(ADC)的影响。方法:回顾性分析经病理证实并被DWI检出的57例肝外胆管癌患者的DWI图像资料,比较静脉注射对比剂Gd-DTPA增强前后及不同b值条件下肝外胆管癌病灶信噪比(SNR)、病灶与正常肝脏间对比信噪比(CNR)及ADC值的差异。结果:同一b值条件下,增强前后病灶SNR、CNR、ADC值的差异均无统计学意义(P>0.05);增强前后肝外胆管癌病灶SNR、CNR及ADC值均随着b值的增大而降低,其差异均有统计学意义(P<0.05)。结论:肝外胆管癌病灶的DWI图像质量及ADC值不受Gd-DTPA影响,所以选择合适b值的增强后DWI序列是可行的。     

静脉注射钆类对比剂对乳腺正常腺体及肿瘤组织MR扩散加权成像的影响

目的 探讨乳腺MR DWI质量及正常腺体与癌组织的ADC值是否受到钆类对比剂增强扫描的影响.方法 对25例已经针吸穿刺或粗针活检病理证实为乳腺癌的患者在静脉注射Gd-DTPA前、后行DWI扣描,将R01分别置于癌灶及正常腺体,应用配对t检验及非参数检验比较b值=0及1000 s/mm2时增强前后图像中癌灶和正常腺体的信噪比(SNR)、对比噪声比(CNR)及ADC值的变化.结果 增强前、后癌灶的SNR(34.56±11.34和33.60±14.34)与正常腺体的SNR(9.88±3.16和10.42±4.18)以及图像CNR(24.16±9.05和22.26±10.05)的差异无统计学意义(P癌灶SNR=0.70,P正常腺体SNR=0.11;PCNR=0.17);增强前后癌灶的ADC值分别为(0.96±0.13)×10-3和(0.95±0.14)×10-3mm2/s,正常腺体分别为(1.90±0.47)×10-3 和(1.91±0.61)×10-3mm2/s,两者在增强后ADC值与其增强前差异均无统计学意义(P=0.20和0.97).结论 乳腺痛组织和正常腺体DWI的质量及ADC测量值不会受到Gd-DTPA的影响,故在乳腺MR扫描中,DWI可以在增强扫描后进行.     

DWI在女性附件囊性肿块中的诊断价值

目的 :探讨DWI在女性附件囊性肿块中的诊断价值。方法 :回顾性分析经手术病理证实的72例女性附件囊性肿块患者的常规MRI表现,测量其DWI(b=800 s/mm2)的信号强度值及ADC值,并计算相对信号强度值(RSI)和对比噪声比(CNR)。将良性囊性成分分成血液、脂质、脓液、黏液和浆液5组,恶性囊性成分分成浆液、黏液2组,并对各组的ADC值、RSI、CNR进行统计学分析。结果:良性病变5组不同囊性成分的ADC值、RSI及CNR组间差异有统计学意义(P均0.05)。良恶性病变之间浆液的ADC值、RSI、CNR差异均无统计学意义(P均0.05),黏液的ADC值、RSI、CNR差异均无统计学意义(均P0.05)。不同良性囊性肿块在常规MRI和DWI的表现各异。结论:通过对女性附件囊性肿块的ADC值、RSI及CNR进行定量分析,能为其定性诊断提供一定的依据;结合常规MRI,DWI有助于囊性成分的鉴别诊断。     

钆对比剂对腹部实性脏器体素内不相干运动磁共振成像的影响

目的探讨钆对比剂对腹部实性脏器体素内不相干运动(IVIM)MRI图像质量及其参数值的影响,寻找腹部IVIM序列扫描的合适时机。资料与方法 20例患者分别于对比剂注射前后行相同腹部IVIM扫描,测量并计算b=50、300、800 s/mm2扩散加权成像(DWI)图像上肝脏、脾脏、胰腺、肾脏的信噪比(SNR)以及肝细胞癌(HCC)的SNR以及对比噪声比(CNR),并测量肝脏、脾脏、肾脏及HCC的表观扩散系数(ADC)值及IVIM参数(D值、D*值、f值),对各测量值增强扫描前后的差异进行比较。结果增强扫描后b=50 s/mm2肝脏的SNR较增强前明显下降(t=2.397,P<0.05)。b=300 s/mm2 HCC的CNR显著增高(t=-3.380,P<0.01)。肾脏各b值的SNR均较增强扫描前显著下降(Z=-2.675~-2.201,P<0.05);而脾脏、胰腺及HCC各b值的SNR与增强扫描前的差异均无统计学意义(t或Z=-1.324~1.104,P>0.05)。增强扫描后仅肾脏的ADC值、D值下降,差异有统计学意义(tADC=3.569,P<0.01;ZD=-3.053,P<0.01),而肝脏、脾脏及HCC的各参数值增强扫描前后差异均无统计学意义(t=-1.102~1.689,P>0.05)。结论注射钆对比剂可降低肝脏低b值和肾脏各b值DWI的SNR,使中等b值肝脏病变的CNR增高,而不影响脾脏、胰腺和肝脏病变的SNR。钆对比剂亦可降低肾脏的ADC值、D值,而对肝脏及其病变、脾脏的DWI及IVIM参数无影响。     

Gd- DTPA对肝脏、脾脏及肾脏1.5T MR弥散加权成像的影响

目的:探讨钆喷酸葡胺(Gd-DTPA)在1.5T MR机对正常肝脏、脾脏、肾脏弥散加权成像(DWI)的影响.方法:30例健康体检者在1.5T MR机做上腹部MRI.除常规MR平扫和增强外,在增强前和增强后7min采用b值=500 s/mm2单次激发自旋回波平面成像序列(SE- EPI)分别行DWI扫描.测量增强前后肝脏、脾脏、肾脏在DWI上的信噪比(SNR)、脾脏-肝脏对比噪声比(CNR)、信号强度值和ADC值,并进行统计分析.结果:30例健康体检者检查结果均正常.正常肝脏、脾脏DWI的SNR、CNR、信号强度值、ADC值增强后7min与增强前比较差异无统计学意义(P＞0.05),肾脏DWI SNR、信号强度值、ADC值增强后7min较增强前降低,差异有统计学意义(P＜0.05).结论:Gd-DTPA增强后7min对肝脏、脾脏DWI的图像质量和ADC值无明显影响,而肾脏DWI的图像质量和ADC值降低.     

同时多层单次激发和分段读出平面回波扩散加权成像诊断乳腺恶性病灶的效能比较

目的比较乳腺同时多层单次激发平面回波成像(SMS+SS-EPI)和分段读出平面回波(RESOLVE)扩散加权成像(DWI)的图像质量及其诊断乳腺恶性病灶的效能。方法该研究为横断面研究。前瞻性分析2021年3月至2023年2月宁波大学附属第一医院因乳腺病变而接受MRI检查并最终经病理证实的102例患者的临床及影像资料。所有患者均接受乳腺MRI常规扫描以及横断面RESOLVE和SMS+SS-EPI序列DWI, 评估2种序列成像的图像质量。主观评价采用5分法, 评价内容包括乳腺的几何畸变、伪影模糊、脂肪抑制、整体图像质量和病灶显著性;客观评价包括病灶信噪比(SNR)、对比噪声比(CNR)、病灶表观扩散系数(ADC)值。采用Wilcoxon符号秩和检验比较2种序列成像的主、客观评价指标。最后采用受试者操作特征曲线及曲线下面积(AUC)评估2种序列图像上病灶ADC值诊断乳腺恶性病灶的效能。结果 102例患者均为单发病变, 均为女性患者, 年龄25～68岁。乳腺恶性病灶60例, 良性病变42例。SMS+SS-EPI序列成像的采集时间为1 min 50 s, RESOLVE序列成像的采集时间为3 m...     

卵巢良恶性病变的磁共振扩散加权成像分析及应用

目的 探讨卵巢良、恶性病变磁共振扩散加权成像(DWI)的特征.方法 回顾分析117个经手术病理证实的卵巢良、恶性病灶的影像资料,测量b值＝50、400、800 s/mm2 时良、恶性病变软组织成分的信号强度, 比较对比噪声比(CNR)和ADC值,分析不同囊性成分常规图像、DWI特征及ADC值均值.结果 显示病变最佳b值＝800 s/mm2.恶性病变软组织成分b值＝800 s/mm2对比噪声比(CNR)高于良性病变,ADC值低于良性病变.ADC值可以预测但不能确定囊性成分性质.结论 结合常规MRI,DWI有助于卵巢良、恶性小病灶显示及鉴别诊断.     

乳腺良恶性病变的3.0T磁共振扩散加权成像鉴别诊断及b值优化

目的:探讨3.0T扩散加权成像(DWI)在乳腺良恶性病变鉴别诊断中的诊断价值并对b值使用进行优化。方法:34例患者共20个良性和16个恶性乳腺病灶纳入研究,同期20例正常乳腺受检者列为对照组。采用3.0T MR行乳腺DWI成像检查,b值分别取0,750 s/mm2,1000 s/mm2,1250 s/mm2。比较不同b值DWI图像质量,测量病灶的对比噪声比(CNR)以及表观扩散系数(ADC)值,以病理诊断为金标准,计算诊断乳腺癌的敏感度、特异度及准确性,绘制受试者工作特征曲线(ROC)并进行比较。结果:不同b值时DWI图像主观质量评分没有统计学差异(F=3.02,P=0.0516>0.05)。b=750 s/mm2时病灶的CNR明显优于b=1000s/mm2及1250s/mm2时(P值为0.004及0.000),而b=1000s/mm2与1250s/mm2之间没有统计学差异(P=0.800>0.05)。相同b值时,正常乳腺组织的平均ADC值>乳腺良性病变>乳腺恶性病变(P均=0.000)。以各b值恶性病变平均ADC值95%可信区间的上限作为界定乳腺癌ADC的阈值,则b=750 s/mm2、1000 s/mm2、1250s/mm2时,ADC阈值分别为1.33×10-3mm2/s、1.25×10-3mm2/s、1.16×10-3mm2/s。以上述阈值判断乳腺癌的敏感度、特异度及准确性分别为81.25%、87.5%、85.71%,81.25%、77.5%、78.57%及81.25%、82.5%、82.14%。三个b值的ROC曲线下面积无显著性差异(P=0.1925>0.05)。结论:乳腺的3.0T DWI中,以b=750s/mm2时病灶CNR最高,值得推荐应用。应用DWI鉴别乳腺良恶性病变时,需要结合ADC值判断。     

Increased diffusion sensitivity with hyperechos.

It is shown that the introduction of a 180 degrees refocusing pulse into a standard diffusion weighted stimulated echo sequence is equivalent to the simplest hyperecho sequence with identical diffusion weighting but equal or greater signal-to-noise (SNR) and thus equal or greater diffusion contrast. For high b-value imaging, the hyperecho sequence thus possesses the high diffusion contrast in the presence of small T(1)/T(2) ratios characteristic of stimulated echo sequences but with less than the 50% loss in SNR that is associated with the stimulated echo. For low b-value imaging, the hyperecho signal converges to that of the standard spin echo. The advantages of the two-pulse diffusion weighted hyperecho sequence are demonstrated theoretically. Experimental results are shown in the application to high angular resolution diffusion encoding (HARD) in normal human brain.     

Is the “biexponential diffusion” biexponential?

Diffusion-weighted signal from the brain, S, deviates from monoexponential dependence on the b-factor. This property is often referred to as biexponential diffusion, since the corresponding model fits data well. The aim of this study is to examine the necessity of using the biexponential model in homogeneous voxels under isotropic diffusion weighting up to b = 2.5 ms/microm(2). The model is compared to the cumulant expansion of ln S in a power series in b, which takes its origin in fundamental properties of the diffusion-weighted signal, but diverges at large b. The absence of statistically significant evidences for the biexponential diffusion is demonstrated in gray matter. The cumulant expansion terminated after the term b(2) describes data equally well with fewer adjustable parameters. The biexponential model is preferable in voxels with a partial volume of CSF.     

扩散张量成像导出量对扩散时间依赖关系的实验研究

目的研究扩散张量导出量与扩散时间的关系。方法保持扩散敏感梯度磁场强度不变,使用8个不同的扩散时间对11名被试者进行扩散张量成像扫描得到脑部的各向异性与各向同性信息,计算出各个感兴趣区的平均扩散率与各向异性分数后进行比较。结果不同扩散时间对应的平均扩散率有显著性差异（P〈0．05）,而各向异性分数无显著性差异（P〉0．05）。结论扩散时间对扩散张量成像导出量中的各向异性分数无影响,对平均扩散率有影响。原因是细胞内外水分子扩散性质不同。     

The tensor distribution function

Diffusion weighted magnetic resonance imaging is a powerful tool that can be employed to study white matter microstructure by examining the 3D displacement profile of water molecules in brain tissue. By applying diffusion‐sensitized gradients along a minimum of six directions, second‐order tensors (represented by three‐by‐three positive definite matrices) can be computed to model dominant diffusion processes. However, conventional DTI is not sufficient to resolve more complicated white matter configurations, e.g., crossing fiber tracts. Recently, a number of high‐angular resolution schemes with more than six gradient directions have been employed to address this issue. In this article, we introduce the tensor distribution function (TDF), a probability function defined on the space of symmetric positive definite matrices. Using the calculus of variations, we solve the TDF that optimally describes the observed data. Here, fiber crossing is modeled as an ensemble of Gaussian diffusion processes with weights specified by the TDF. Once this optimal TDF is determined, the orientation distribution function (ODF) can easily be computed by analytic integration of the resulting displacement probability function. Moreover, a tensor orientation distribution function (TOD) may also be derived from the TDF, allowing for the estimation of principal fiber directions and their corresponding eigenvalues. Magn Reson Med 61:205–214, 2009. © 2008 Wiley‐Liss, Inc.     

一种新的用于磁共振扩散加权波谱术的扩散敏感梯度磁场施加方案

目的 提出一种基于PRESS的用于磁共振扩散加权波谱的扩散敏感梯度磁场施加方案.方法 在PRESS序列中的2个π射频脉冲两侧各施加一对交错的扩散敏感梯度磁场.结果 本方案有效减小涡流,利用PRESS序列中2个π射频脉冲之间的时间,延长了扩散梯度磁场脉冲的持续时间.即使在扩散权重较大的情况下,Naa,Cr及Cho的峰仍十...     

Anisotropic anomalous diffusion assessed in the human brain by scalar invariant indices

A new method to investigate anomalous diffusion in human brain, inspired by the stretched‐exponential model proposed by Hall and Barrick, is proposed here, together with a discussion about its potential application to cerebral white matter characterization. Aim of the work was to show the ability of anomalous diffusion indices to characterize white matter structures, whose complexity is only partially accounted by diffusion tensor imaging indices. MR signal was expressed as a stretched‐exponential only along the principal axes of diffusion; whereas, in a generic direction, it was modeled as a combination of three stretched‐exponentials. Indices to quantify the tissue anomalous diffusion and its anisotropy, independently of the experiment reference frame, were derived. Experimental results, obtained on 10 healthy subjects at 3T, show that the new parameters are highly correlated to intrinsic local geometry when compared with Hall and Barrick indices. Moreover, they offer a different contrast in white matter regions when compared with diffusion tensor imaging. Specifically, the new indices show a higher capability to discriminate among areas of the corpus callosum associated to different distribution in axonal densities, thus offering a new potential tool to detect more specific patterns of brain abnormalities than diffusion tensor imaging in the presence of neurological and psychiatric disorders. Magn Reson Med, 2010. © 2010 Wiley‐Liss, Inc.