MR体素内不一致运动序列预测和评价宫颈癌放化疗效果

目的 探讨磁共振体素内不一致运动序列(IVIM)在预测和评价宫颈癌放化疗效果方面的价值.方法 对62例接受同步放化疗(放疗+同步顺铂化疗)的宫颈癌患者于治疗前、治疗后1个月分别行MRI常规序列和双指数模型的IVIM序列扫描.测量治疗前后肿瘤最大径并根据疗效进行分组,测量并比较治疗前不同疗效组间IVIM参数值差异和各组治疗前后参数值差异.结果 (1)肿瘤稳定(SD)组治疗后ADC、D值高于治疗前(P=0.016,0.001);(2)肿瘤部分缓解(PR)组治疗后ADC、D值高于治疗前(P=0.01,0.01),D*值低于治疗前(P=0.044);(3)肿瘤完全消失(CR)组治疗后ADC、D和f值均高于治疗前(P=0.000,0.000,0.03),D*值低于治疗前(P =0.011);(4)治疗前SD组ADC依次低于PR组和CR组(P =0.000,0.000),但PR组和CR组间差异无统计学意义(P =0.094);SD组D值依次低于PR组和CR组,三组间差异均有统计学意义(P =0.000,0.000,0.003);SD组D*值高于其他两组,但仅SD组和CR组间差异有统计学意义(P =0.003),SD组D*值高于PR组和CR组(P=0.000,0.004),PR组和CR组间差异无统计学意义(P =0.212).结论 宫颈癌治疗前IVIM序列有助于预测治疗效果,治疗前后IVIM参数值改变对评价治疗效果具有重要作用.     

3.0T MR扩散加权成像对宫颈癌放化疗疗效的评估价值

目的：探讨扩散加权成像（DWI）对宫颈癌放化疗疗效的评估价值。方法：46名接受全程放化疗治疗的宫颈癌患者分别在治疗前、治疗2周后、外照射25次后及治疗结束后进行盆腔常规MRI及DWI扫描,每次扫描均测量肿瘤的直径及ADC值。根据治疗结束6个月后的随访结果将患者划分为完全有效组（CR）、部分有效组（PR）及无效组（SD）。计算并两两比较各次 MRI扫描测得的肿瘤ADC值及直径的动态变化值。结果：CR 组在治疗2周及外照射25次的 ADC值提高均高于 RP 组及 SD 组（P＜0．05）,治疗结束后 CR 组的 ADC 值与 PR 组及 SD 组间差异均有统计学意义（P＜0．05）。治疗前、放化疗2周后及外照射25次后各肿瘤组（CR、PR、SD组）的ADC 值、肿瘤最大直径之间差异均无统计学意义（P＞0．05）。结论：DWI可作为预测及监测宫颈癌放化疗疗效的有效方法。     

MR扩散成像对宫颈癌放化疗早期疗效的评价

目的：探讨MR扩散成像评价晚期宫颈癌放化疗早期疗效的价值。方法：对18例经病理证实为晚期宫颈癌并接受放化疗的患者,在治疗前和开始治疗后2周、及治疗结束后行常规MRI及DWI检查。测量治疗前和治疗后不同时间点肿瘤最大径和ADC值,按治疗后肿瘤直径的变化进行分组,分析各组治疗前和治疗后不同时间点ADC值差异。结果：治疗后2周ADC值升高,完全缓解（CR）组ADC值变化高于部分缓解（PR）组,差异具有统计学意义（P〈0.05）。结论：MR扩散成像可以作为晚期宫颈癌放化疗早期评价的指标,并可根据ADC值升高情况预测治疗效果。     

不同b值DWI对宫颈癌放化疗疗效的评估价值

目的 探讨不同b值弥散加权成像（DWI,diffusion-weighted imaging）对宫颈癌放化疗疗效的评估价值.方法 48名接受全程放化疗治疗的宫颈癌患者分别在治疗前、治疗2周后、治疗4周后及治疗结束后进行盆腔常规MRI及DWI扫描,每次扫描均测量肿瘤的ADC值,所有ADC值均由b=0,600s/mm^2和b=0,1000s/mm^2两组ADC图得出.根据治疗结束后的结果将患者划分为完全有效组（CR）、部分有效组（PR）及无效组（SD）,并根据ROC曲线比较两组ADC图评估宫颈癌放化疗疗效的价值.结果 治疗2周及4周后CR组的ADC值提高百分比在两组ADC图中均高于RP及SD组;治疗结束后,CR组的ADC值在两组ADC图中均高于RP及SD组;其中治疗4周后及治疗结束后高b值组（b=0,1000s/mm^2）区分CR组与PR/SD组的能力高于低b值组（b=0,600s/mm^2） （P＜0.05）;低b值组所测数据的标准差均大于高b值组.结论 高b值DWI评估宫颈癌放化疗疗效的整体价值高于低b值DWI,且数值更为稳定.     

磁共振扩散加权成像预测、监测直肠癌放化疗效果的价值

目的探讨MR扩散加权成像(diffusion-weighted imaging,DWI)在预测、监测直肠癌放、化疗效果中的应用价值。资料与方法动态监测15例行放、化疗的直肠癌患者,于放化疗前、放化疗结束和放化疗后4~5周行3次常规MRI及DWI。测量直肠癌的长度、肿瘤侵犯直肠壁厚度和表观扩散系数(apparent diffusion coefficient,ADC)值在放化疗前、后各时间点的变化,并分别进行比较;依据实体瘤疗效评价标准(RECIST)分组,比较各组在放化疗前ADC值之间的差异。结果直肠癌放化疗结束时,肿瘤侵犯肠壁的厚度较放化疗前差异有统计学意义(0.010.05);而对于放化疗结束与放化疗后4~5周,三者的变化差异均无统计学意义。放化疗前部分缓解(PR)与病灶稳定(SD)组之间的ADC值差异无统计学意义(P=0.222>0.05)。结论 DWI可优先、准确评价直肠癌放化疗的疗效相对于肿瘤形态学变化;而放化疗前ADC值对于预测直肠癌放化疗的疗效无明显意义...     

磁共振扩散加权成像预测与评价宫颈癌放化疗疗效的研究

目的 探讨磁共振扩散加权成像(DWI)在预测与评价宫颈癌放化疗疗效中的应用价值.方法 收集282例经病理检查证实为宫颈癌的患者,分别在治疗前、治疗结束后行DWI检查,测量肿瘤最大径和表现扩散系数(ADC)值.治疗结束后,依据实体肿瘤疗效评价标准(RECIST)将患者分为缓解组、无效组.根据治疗结束后2年的随访复查情况将患者分为复发组、无复发组.比较两组间的治疗前和治疗结束后ADC值,并分析疗效及复发情况与治疗前ADC值、治疗结束后的ADC升高值之间的相关性. 结果 缓解组223例,无效组59例.复发组70例,无复发组212例.缓解组治疗前ADC值明显低于无效组(t=3.274,P<0.05),无复发组治疗前ADC值明显低于复发组(t=1.031,P<0.05).治疗前ADC值低的患者复发率明显低于治疗前ADC值高的患者(χ²=5.175,P<0.05).治疗结束后的疗效及治疗结束后2年的复发情况与治疗前ADC值均呈负相关(r=-0.571、-0.675,P<0.05),与治疗结束后的ADC升高值均呈正相关(r=0.641、0.547,P<0.05).缓解组、无复发组治疗结束后ADC值升高明显(t=2.031、4.011,P<0.05),无效组、复发组ADC值升高不明显.结论 治疗前的ADC值有助于预测宫颈癌放化疗疗效,治疗结束后的ADC变化值有助于评价宫颈癌放化疗疗效.     

动态增强MRI定量评估喉及下咽鳞癌同步放化疗近期疗效研究

目的:探讨MRI动态增强扫描(DCE-MRI)对喉及下咽鳞癌同步放化疗近期疗效的预测价值.方法:2014年12月-2015年12月经本院喉镜活检病理证实并行同步放化疗的喉(10例)及下咽(26例)鳞癌患者共36例,于治疗前行DCE-MRI检查,并在放疗剂量累积达50Gy时行治疗中MRI复查.根据治疗结束后肿瘤缓解情况,将患者分为完全缓解组(CR)及部分缓解组(PR).测量DCE-MRI定量参数值,包括容积转移常数(Ktrans)、速率常数(Kep)和血管外细胞外容积分数(Ve),分别比较三者在CR组与PR组间的差异,并绘制ROC曲线评估各定量参数预测喉及下咽鳞癌同步放化疗近期疗效的效能.结果:36例患者在同步放化疗后达CR20例,PR16例.喉癌和下咽癌两组间治疗前DCE-MRI各定量参数比较,差异均无统计学意义(P＞0.05).CR组治疗前Ktrans、Kep和Ve值分别为(0.307±0.055)min-、(0.527±0.114)min-1和0.587±0.045,PR组的相应值分别为(0.234±0.049) min-1/min、(0.390±0.090) min-1和0.602±0.037.两组比较,Ktrans和Kep的差异均有统计学意义(P＜0.05),Ve的差异无统计学意义(P＞0.05).ROC曲线分析,以Ktrans=0.283min-1为阈值,预测同步放化疗后达CR的曲线下面积(AUC)、敏感度及特异度分别为0.839、70.0％和81.2％;以Kep=0.446min-1为阈值,预测同步放化疗后达CR的AUC、敏感度及特异度分别为0.809、75.0％和75.0％.结论:DCE-MRI定量参数有助于预测喉及下咽鳞癌同步放化疗的近期疗效.     

磁共振DWI评估周围型非小细胞肺癌化学药物治疗疗效的价值

目的 探讨磁共振弥DWI评估周围型非小细胞肺癌化学药物治疗疗效的价值。方法 选取28例经病理证实为非小细胞肺癌并接受首次化学药物治疗的患者,分别于化学药物治疗前1周内、化学药物治疗1周期结束后(化学药物治疗第2周期前2～3天)进行胸部MRI常规及DWI检查。根据RECIST标准,分为部分缓解组(PR)及疾病稳定组(SD)。比较两组ADC值增长率和肿瘤最大径,分析化学药物治疗1周期后ADC值变化率的受试者工作特征曲线(ROC)。结果 两组ADC值于化学药物治疗后升高,PR组化学药物治疗第1周期后ADC值变化率高于SD组,差异有统计学意义(P=0. 000);肿瘤最大径变化不明显; PR组化疗第1周期后ADC值变化率ROC曲线显示,以ADC值升高15. 82%作为诊断分界点,敏感性为100%,特异性为60%。结论 化学药物治疗前后ADC值的变化率可以作为早期预测肺癌化学药物治疗疗效的敏感指标,能够早于肿瘤最长径的变化对非小细胞肺癌的化学药物治疗疗效的评估。     

DWI对晚期肝细胞肝癌患者分子靶向药物治疗的疗效评估

目的 :探讨DWI评估晚期肝细胞肝癌患者分子靶向药物治疗疗效的价值。方法 :选择我院2013年1月至2014年12月收治的行分子靶向药物治疗的晚期肝细胞癌患者12例。依据治疗效果分为A组(有治疗反应组)5例和B组(无治疗反应组)7例。对2组治疗前后病灶最大径和ADC值进行观察,并进行统计学分析。结果:治疗后,A组病灶在MRI T1WI和T2WI信号增大,DWI信号无明显变化;B组病灶的T1WI、T2WI、DWI信号均无明显变化。与B组比较,A组治疗前及治疗后病灶的最大径均偏大(均P0.05)。A组治疗前后ADC值明显变化,而B组ADC值变化不明显(P0.05)。治疗前,A组病灶最大径与ADC值(b=500 s/mm2)呈正相关性(r=0.556,P=0.038);B组病灶最大径与ADC值无明显相关性(P0.05)。结论:DWI可及时、准确评估晚期肝细胞肝癌分子靶向药物治疗的预后。     

ADC值变化率早期预测食管鳞状细胞癌放化疗疗效的价值

目的 :探讨ADC值评价中晚期食管鳞状细胞癌放化疗早期疗效的价值。方法 :收集31例经病理证实的食管鳞状细胞癌,在治疗前后不同时间点行常规MRI及DWI扫描。以治疗结束作为疗效评价时间点,应用WHO的《实体肿瘤疗效评价标准(RECIST)修订版(version1.1)》进行疗效评价,将患者分为反应组(完全缓解和部分缓解)与无反应组(病变稳定和病变进展)。2组比较采用独立样本t检验,治疗前后ADC值变化率(△ADC)采用ROC曲线进行分析,用非条件Logistic回归分析筛查出影响患者疗效的独立预测因素。结果:反应组21例(67.7%),无反应组10例(32.3%)。治疗前2组肿瘤最大径差异无统计学意义(P0.05)。放疗11次时的反应组ADC值、△ADC(△ADC_(11))均明显高于无反应组(均P0.05)。△ADC_(11)治疗反应ROC曲线下面积最大为0.838,当△ADC_(11)值为11.593%时,判定治疗是否有效的敏感度及特异度分别为83.3%、76.9%。非线性Logistic回归分析显示,△ADC_(11)是影响食管鳞状细胞癌放化疗敏感程度的独立预后因素,其相对风险度为1.108(P0.05)。结论:DWI对预测食管鳞状细胞癌放化疗早期疗效具有重要临床意义。△ADC_(11)可作为预测食管鳞状细胞癌早期放化疗敏感性的最佳指标和独立预后因素。     

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.     

In vivo diffusion tensor imaging of human calf muscle.

PURPOSE: To investigate a tetrahedral diffusion gradient encoding scheme to measure the diffusion tensor in vivo for human calf muscle. MATERIALS AND METHODS: The theoretical TE which maximizes the signal-to-noise ratio (SNR) of the diffusion images was derived for both the orthogonal and tetrahedral sampling strategies and the SNR advantage verified experimentally. A diffusion echo-planar imaging (EPI) sequence was used to image five volunteers. Gradient cycling and geometric averaging was performed to eliminate cross-terms between the imaging and diffusion gradients. RESULTS: Trace diffusion coefficients in human muscle are spatially invariant and have low intersubject variability (<4%). Images of the off-diagonal terms confirm the anisotropy of muscle, and fiber orientation maps were derived from these off-diagonal images. A noninvariant index of anisotropy, A(ratio) (average value: 1.28), was found to be less susceptible to noise than the invariant index. CONCLUSION: This technique is robust and can be readily implemented on clinical scanners with EPI capabilities.