连续动脉自旋标记灌注成像在急性脑梗死中的应用

目的 探讨连续动脉自旋标记灌注加权成像(CASL-PWI)在急性脑梗死中的应用价值.资料与方法 对15例临床高度怀疑急性脑梗死的患者行常规MRI及扩散加权成像(DWI)、CASL-PWI检查.分别在DWI、CASL-PWI上确定病变的范围,比较两者之间的关系.结果 CASL-PWI低灌注区面积大于DWI异常信号区面积的患者8例,相等1例,小于DWI异常信号区者6例.结论 CASL-PWI无需注射对比剂,操作简单,与DWI相结合,可诊断超急性期脑梗死,对临床治疗方案的制定和评估预后具有重要意义.     

软组织肿瘤的功能MR影像学研究近况

MR功能成像(包括MR扩散加权成像、MR灌注加权成像及MR波谱等)可提供生理、生化及代谢过程的信息并获得动态的定量资料,弥补了常规MR检查在软组织肿瘤定性、判断肿瘤的恶性程度及判定术后疗效等方面的不足。就不同成像技术的优缺点、成像的病理生理学基础以及在临床诊断中的作用和限度进行综述。     

软组织肿瘤的功能MR影像学研究近况

MR功能成像(包括MR扩散加权成像、MR灌注加权成像及MR波谱等)可提供生理、生化及代谢过程的信息并获得动态的定量资料,弥补了常规MR检查在软组织肿瘤定性、判断肿瘤的恶性程度及判定术后疗效等方面的不足.就不同成像技术的优缺点、成像的病理生理学基础以及在临床诊断中的作用和限度进行综述.     

非中风类脑疾病的扩散加权成像

扩散加权成像提供了一种不同于传统MRI技术的影像对比。这种技术对检出急性缺血性中风和鉴别急性中风与其他表现为突发神经功能障碍的病变特别敏感。扩散加权成像同时也可提供其它脑部病变如肿瘤、颅内感染、颅脑外伤及脱髓鞘病变的必要信息。在大多数脑部MR成像时，扩散加权MR成像应作为一种必要的序列。     

扩散加权成像对良恶性淋巴结鉴别的研究进展

淋巴结转移与否对于癌症病人的预后、分期及治疗方案的选择极为重要。目前常规MRI依靠淋巴结大小鉴别其良恶性的准确性不高，利用MR功能成像方法鉴别淋巴结良恶性是目前影像学研究的热点。其中扩散加权成像相较其他方法具有诸多优点。近年来非高斯模型包括双指数模型、拉伸指数模型、扩散峰度模型等逐渐应用于临床。现就传统及非高斯模型扩散加权成像在淋巴结良恶性鉴别上的研究现状及价值予以综述。     

顺磁性对比剂动态增强MR脑灌注成像

随着MR快速成像技术的发展,顺磁性对比剂的应用,基本平面回波技术的顺磁性对比剂动态增强MR脑灌注成像已应用于颅脑检查的许多方面,并且在急性脑卒中、脑肿瘤等部分疾病检查中已成为常规,并逐渐延伸至脑变性疾病、烟雾病及吸毒者及功能评估等更为广泛的领域。对疾病除早期显示病变外,还可指导疾病的治疗及判断预后。就其成像原理、计算参数、检查方法入临床应用进行介绍。     

MR磁敏感加权成像在脑梗死治疗前后随访中的应用价值

目的探讨MR磁敏感加权成像(SWI)在脑梗死治疗前后随访中的应用价值。资料与方法搜集经临床及影像学检查证实的脑梗死患者资料30例,急性13例,亚急性17例。所有患者治疗前后均行常规MR平扫、扩散加权成像(DWI)及SWI扫描。对比分析治疗前后MRI图像变化特点。结果治疗前常规MRI检出脑梗死灶内出血4例,SWI检出9例,治疗后SWI显示5例发生出血性转化。治疗前30例脑梗死灶SWI图像相对信号强度为0.97±0.09,治疗后相对信号强度为1.06±0.12,治疗前后相对信号强度差异有统计学意义(t=-3.579,P<0.05)。治疗前后脑梗死灶内血管的显示差异有统计学意义(P<0.05)。结论SWI对于显示脑梗死伴发出血、治疗后出血性转化、侧支血管构建等方面优于常规MRI序列,在脑梗死治疗后随访中具有重要的临床应用价值。     

颅内非缺血性病变的MR扩散加极成像

MR扩散加权成像作为一种新的MR成像序列，能提供水分子微观运动的信息，对急性缺血性中风的诊断价值已得到肯定，对颅内非抉血性病变的应用价值在进一步研究之中。就MR扩散加权成像的技术原理、颅内非缺血性病变的扩散加权成像的表现予以综述，以提高该成像序列的临床应用价值。     

酰胺质子转移加权成像在缺血性脑梗死中的研究进展

酰胺质子转移加权（APTw）成像是基于化学交换饱和转移效应的MR分子成像技术,能够反映体内蛋白质浓度和酸碱度的变化。APTw成像通过反映脑梗死时细胞环境的p H变化,为脑梗死的诊断、治疗以及预后预测提供重要的影像学信息。总结APTw成像的影响因素,并综述其在缺血性脑梗死中评估酸中毒、缺血半暗带、梗死程度、疗效和预后中的研究进展。     

乳腺癌MR弥散加权成像研究进展

MR在乳腺癌诊断方面的应用价值已经得到广泛认同,为增加检出乳腺癌的敏感性,需应用多种MR扫描技术。然而,常规MR在检测及描述乳腺病变特征时具有一定的局限性,弥散加权成像作为一种重要的功能成像技术,能够反映组织的生物物理学特征,有较大的发展前景。弥散加权成像是唯一能够检测活体组织内水分子弥散运动的非侵入性方法,可以检测出组织结构在分子水平上的改变。其成像时间短,敏感性高,无需使用对比剂,并且能比常规MR检查更早的发现病变,因此,它已经广泛应用于脑部疾病中,也越来越多地应用于乳腺疾病方面。本文就弥散加权成像在乳腺癌的应用方面予以综述。     

后循环缺血的功能MRI研究

后循环缺血(PCI)也称椎基底动脉系统缺血,虽然其发病率远低于前循环缺血(ACI),但其致死率显著高于ACI,严重威胁人类健康,故越来越受到国内外研究者的关注。早期诊断和治疗是改善PCI预后的关键。各种功能MRI技术不仅能够获得后循环结构的形态学和解剖学信息,而且能够无创性观察活体脑组织血流、代谢及功能情况,对PCI的早期诊断和疗效评估等具有重要价值。对各种功能MRI技术在PCI中的研究应用进行综述。     

MRI常规序列、SWI序列及DWI在脑外伤微出血患者诊断中的应用研究

目的 探究MRI常规序列、SWI序列以及DWI序列在脑外伤微出血患者诊断中的应用价值。方法 选取2019年8月～2020年4月我院收治的71例脑外伤微出血患者作为观察对象,所有患者在入院3天后行头部MRI常规序列(T₁WI、T₂WI、T₂FLAIR)、扩散加权成像(DWI)序列及磁敏感加权成像(SWI)序列检查。观察脑外伤微出血病灶在不同扫描序列中的影像学表现,对比不同扫描序列对脑外伤微出血病灶的检出率。结果 微出血病灶在T₁WI序列中多表现为大小不等的斑片状、条状等、低信号影,T₂WI、T₂FLAIR序列中多为稍高信号或等信号,DWI序列中多表现为低信号或等信号。微出血病灶在SWI序列中多为点状、斑片状、类圆形或环形低信号影,与T₁WI、T₂WI、T₂FLAIR等MRI常规序列以及DWI序列相比,SWI对微出血病灶的显示更加明显,所显示的微出血病灶更多,病灶边缘更加清晰,病灶范围更大。71...     

高b值扩散加权成像对胶质瘤分级的应用价值

目的评价高b值MR扩散加权成像(diffusion weighted imaging,DWI)对胶质瘤分级的应用价值。资料与方法经手术病理证实的36例胶质瘤(高级23例,低级13例)患者行常规MRI和DWI检查,分析其DWI表现。测量低、中、高b值(b=600 s/mm2、1000 s/mm2、3000 s/mm2)DWI图像中不同级别胶质瘤的肿瘤实性区域与对侧相应部位正常脑白质区的信号强度(SI)和表观扩散系数(ADC)值,计算肿瘤与正常区SI的比值即相对信号强度(rSI)和ADC的比值即相对ADC值(rADC)。结果 (1)在高b值时,21例(91.3%)高级胶质瘤呈高信号,而12例(92.3%)低级胶质瘤呈低信号。(2)在b值相同时,高级胶质瘤的平均rSI明显高于低级胶质瘤,平均ADC值、平均rADC值明显低于低级胶质瘤,两组之间的差异均有统计学意义(P<0.0001),其中rSI以及rADC的差异在高b值时更大。(3)对于高级胶质瘤,在高b值与中b值、高b值与低b值比较时平均rSI值以及平均rADC值的差异均有统计学意义(P<0.0001);对于低级胶质瘤,在高b值与中b值、高b值与低b值比较时平均r...     

T2-weighted and diffusion-weighted MRI for discriminating benign from malignant focal liver lesions: diagnostic abilities of single versus combined interpretations

Purpose:

To compare the diagnostic accuracies of diffusion‐weighted imaging (DWI), T2‐weighted imaging (T2WI), and the combination of both sequences in discriminating benign from malignant focal liver lesions (FLLs).

Materials and Methods:

In all, 166 patients with 269 FLLs (153 benign and 116 malignant) were retrospectively evaluated. Two abdominal readers visually assessed the DWI, T2WI, and the combined (DWI+T2WI) image sets in an independent and blinded manner. The diagnostic abilities of each image set in discriminating the benign from the malignant FLLs set were compared using a binary logistic regression model. Pathologic results, consensus reading, and follow‐up imaging were used as the reference standard.

Results:

The overall characterization accuracy in all lesions of the combined set (80.3%) was significantly higher than those of the T2WI set (68.8%) and DWI set (73.2%) (combined vs. T2WI, P < 0.001; combined vs. DWI, P = 0.001), while there was no significant difference between the T2WI and DWI sets (P = 0.058). All image sets were more accurate in the characterization of malignant FLLs than of benign FLLs (P < 0.001).

Conclusion:

T2WI and DWI are complementary in discriminating benign from malignant FLLs; their combination improves diagnostic confidence. J. Magn. Reson. Imaging 2012;35:1388–1396. © 2012 Wiley Periodicals Inc.     

Quantitative analysis of diffusion-weighted magnetic resonance imaging of the pancreas: usefulness in characterizing solid pancreatic masses

PURPOSE: To evaluate whether measurement of apparent diffusion coefficient (ADC) and pure diffusion coefficient (D) can help to characterize solid pancreatic masses. MATERIALS AND METHODS: Diffusion-weighted MR imaging was performed in both a patient group (n = 71; pancreatic cancer [n = 47], mass-forming pancreatitis [n = 13], solid pseudopapillary neoplasm [n = 6], and neuroendocrine tumor [n = 5]) and a normal control group (n = 11) by applying three b-factors of 0, 500, and 1000 sec/mm(2). ADC(500), ADC(1000), D (ADC using b = 500 and 1000 sec/mm(2)), and perfusion fraction (f, 1- exp [-500 sec/mm(2) x (ADC(500) - D)]) of normal pancreas, pancreatic cancer, and mass-forming pancreatitis were compared using the Kruskal-Wallis test. Receiver operating characteristic (ROC) analysis was performed to evaluate the diagnostic performance and optimal cutoff value of these parameters in differentiating pancreatic cancer from mass-forming pancreatitis. RESULTS: Normal pancreas had significantly higher mean ADC(500), ADC(1000), and f than either pancreatic cancer (P < 0.001, < 0.001, and 0.004, respectively) or mass-forming pancreatitis (P < 0.001, < 0.001, and 0.002, respectively). ADC(500), ADC(1000), and D of mass-forming pancreatitis were significantly lower than those of pancreatic cancer (P = 0.002, 0.004, and 0.014, respectively). Sensitivities and specificities in the diagnosis of pancreatic cancer were 72.3% and 76.9% for ADC(500), 87.2% and 69.2% for ADC(1000), 87.2% and 61.5% for D, and 42.6% and 92.3% for f, respectively. CONCLUSION: Measurement of ADC and D may be helpful in differentiating pancreatic cancers from mass-forming pancreatitis.     

功能MRI评价肝癌微创治疗疗效的研究进展

原发性肝细胞癌是最常见的恶性肿瘤之一。目前经导管肝动脉化学栓塞(TACE)、射频消融术(RFA)及高能聚焦超声(HIFU)等非手术微创治疗已成为外科手术之外治疗肝癌的首选方法。但由于治疗方法的局限性,术后常出现肿瘤病灶的残存或复发,因此准确评价术后疗效非常重要。近年扩散加权成像(DWI)、灌注成像(PWI)、磁共振波谱(MRS)在对肝癌的早期诊断及术后评价中发挥了重要作用。     

MRI联合DWI在强直性脊柱炎诊断中的价值

目的探讨MRI联合DWI对强直性脊柱炎(AS)的诊断价值。资料与方法搜集经修订纽约标准确诊的31例AS病例和25例正常对照组,两组均行两侧骶髂关节常规MRI横断位和冠状位抑脂T2WI、T1WI联合SE/EPI扩散加权成像(DWI)横断位扫描(b值0,600 s/mm2),观察两组骶髂关节的信号改变,测量表观扩散系数(ADC)值并作统计学检验。结果 31例病例组中的24例双侧或单侧骶髂关节面下骨质抑脂T2WI呈高信号,29例DWI呈高信号,25例对照组骶髂关节面下骨质T2WI、DWI均呈等信号,测量ADC值,病变组为(0.993±0.169)×10-3mm2/s,对照组为(0.649±0.395)×10-3mm2/s,病变组ADC值明显高于对照组(t=4.14,P<0.001),两者间差异有统计学意义。结论 MRI联合DWI对AS早期诊断有重要的临床价值。     

Tumor extension in high-grade gliomas assessed with diffusion magnetic resonance imaging: values and lesion-to-brain ratios of apparent diffusion coefficient and fractional anisotropy

Purpose: To determine whether the apparent diffusion coefficient (ADC) and fractional anisotropy (FA) can distinguish tumor-infiltrated edema in gliomas from pure edema in meningiomas and metastases.

Material and Methods: Thirty patients were studied: 18 WHO grade III or IV gliomas, 7 meningiomas, and 5 metastatic lesions. ADC and FA were determined from ROIs placed in peritumoral areas with T2-signal changes, adjacent normal appearing white matter (NAWM), and corresponding areas in the contralateral healthy brain. Values and lesion-to-brain ratios from gliomas were compared to those from meningiomas and metastases.

Results: Values and lesion-to-brain ratios of ADC and FA in peritumoral areas with T2-signal changes did not differ between gliomas, meningiomas, and metastases (P = 0.40, P = 0.40, P = 0.61, P = 0.34). Values of ADC and FA and the lesion-to-brain ratio of FA in the adjacent NAWM did not differ between tumor types (P = 0.74, P = 0.25, and P = 0.31). The lesion-to-brain ratio of ADC in the adjacent NAWM was higher in gliomas than in meningiomas and metastases (P = 0.004), but overlapped between tumor types.

Conclusion: Values and lesion-to-brain ratios of ADC and FA in areas with T2-signal changes surrounding intracranial tumors and adjacent NAWM were not helpful for distinguishing pure edema from tumor-infiltrated edema when data from gliomas, meningiomas, and metastases were compared.     

不同b值对脑扩散加权图像质量的影响

目的:分析不同b值对扩散加权成像(DWI)质量的影响。方法:15例健康志愿者,分别采用b值为500、1000、1500、2000、2500及3000 s/mm2,进行MR DWI检查,选取内囊后肢、大脑皮层、胼胝体膝部及背景等部位进行信号强度和表观扩散系数(ADC)值的测定,并进行统计学分析。同时对所有患者进行常规T1WI和T2WI检查。结果:不同b值条件下,内囊后肢、大脑皮层、胼胝体膝部的信号强度差异有显著性意义(P<0.05),背景噪声间差异无显著性意义(P>0.05);随着b值升高,组织的信号强度降低。不同b值条件下,内囊后肢、大脑皮层、胼胝体膝部的ADC值差异有显著性意义(P<0.05);随着b值升高,组织ADC值降低。结论:在1.5 T场强条件下,b值为1000和1500 s/mm2时扩散加权图像上组织对比较好,清晰度较高。     

Radial GRASE: implementation and applications.

RAD-GRASE is an MRI sequence that combines radial (RAD) k-space scanning with the gradient and spin-echo (GRASE) technique. RAD-GRASE has the advantages of all radial data acquisition methods in that it can reduce motion sensitivity and correct motion-induced data errors, which can be exploited to achieve high-resolution diffusion-weighted imaging (DWI). One can obtain different types of image contrast, including DWI, T(1), T(2), and T(2)*, in RAD-GRASE by controlling the magnetization preparation and sequence timing. Moreover, because there is oversampling of the low spatial frequencies inherent to radial sequences, partial data reconstruction can be used to achieve multiple forms of image contrast from a single acquired data set, and to generate parametric image maps of equilibrium magnetization, T(2), and T(2) (dagger). The RAD-GRASE technique can also be used to achieve fat-suppressed and/or separated fat and water images by choosing the appropriate timing parameters.