人脑磁共振弹性成像的初步研究

目的探讨MR弹性成像（MRE）在正常人脑的应用。方法研制用于人脑的激发装置，激发装置附加于头线圈上，并固定在志愿者头部，激发装置产生的低频率（f）振荡波经颅骨传至颅内，引起剪切波在脑组织内传播；设计成像脉冲序列，脉冲序列以梯度回波序列为基础，在X、Y或Z轴上施加运动敏感梯度（MSG）。剪切波导致的脑组织内周期性移位可使接收信号产生周期性相位位移，获得相位图像，从而显示脑组织内剪切波的传播。通过调整相位偏置，获得1个周期内剪切波的动态传播图像；相位图像经局部f估算法处理后获得局部剪切波的波长（γ），计算出剪切模量，获得弹性图像；激发f采用100、150和200Hz。结果MRE的相位图清楚显示了剪切波在脑组织内的传播，剪切波从脑表面向中心传播。剪切波γ随激发f而变化，γ与激发f呈反比。脑白质内剪切波γ大于脑灰质；弹性图像显示脑白质的剪切模量大于脑灰质的剪切模量。结论MRE的相位图可显示剪切波在脑组织内的传播，弹性图像显示了脑灰质与白质之间的弹性变化。     

fMRI和DTI在脑肿瘤中的联合应用研究

功能磁共振成像可以显示脑皮质功能区的激活状态,可用于对脑肿瘤术前脑功能区的定位、预测脑肿瘤手术效果及术后评价;扩散张量成像可以观察脑白质纤维结构的特征性改变.功能磁共振成像和扩散张量成像融合技术可用于外科手术计划的制定,有助于最大限度地切除肿瘤及减少术后损害.综述功能磁共振成像和扩散张量成像融合技术在脑肿瘤中的应用.     

前列腺MR弹性成像的研究进展

MR弹性成像(MRE)是一种表征组织机械特性的定量成像方式。MRE通过剪切波测量组织的硬度和黏滞度, 以反映不同病变的生物力学特性, 在疾病检测、鉴别诊断、病理分级等方面具有广泛的应用前景。笔者综述了现阶段MRE在前列腺领域的研究进展。     

fMRI和DTI在脑肿瘤中的联合应用研究

功能磁共振成像可以显示脑皮质功能区的激活状态,可用于对脑肿瘤术前脑功能区的定位、预测脑肿瘤手术效果及术后评价;扩散张量成像可以观察脑白质纤维结构的特征性改变.功能磁共振成像和扩散张量成像融合技术可用于外科手术计划的制定,有助于最大限度地切除肿瘤及减少术后损害.综述功能磁共振成像和扩散张量成像融合技术在脑肿瘤中的应用.     

剪切波弹性成像对甲状腺滤泡性病变的术前危险分级:诊断的准确性和最佳测量层面

正摘要目的评估剪切波弹性成像对甲状腺滤泡性病变恶性度的诊断准确性,并确定最佳的剪切波弹性成像测量平面。材料与方法本研究经伦理委员会批准,符合HIPAA。受试者为术前细针抽吸活检报告诊断为"意义不明的细胞非典型病变"、"可疑滤泡性病变"、"可疑滤泡性肿瘤"或"可疑嗜酸细胞瘤",受试者均签署知情同意书并接受常规超声检查、多普勒评价和剪切波弹性成像。甲状腺恶性肿瘤的预测值参考手术病理结果。结果 35例(男12例,女23例)经细针抽     

多层螺旋CT灌注成像在脑肿瘤诊断中的临床研究

目的: 探讨多层螺旋CT(multislice spiral CT,MSCT)脑肿瘤灌注成像方法及其临床应用价值.材料和方法: 对27例脑肿瘤先用常规CT平扫确定肿瘤中心实质部位,然后进行MSCT灌注扫描.扫描图像经ADW4.0工作站PerfusionⅡ软件进行计算,得出灌注图像及参数,包括脑血流量(CBF)、脑血容量(CBV)、造影剂平均通过时间(MTT)和肿瘤微血管表面通透性(PS).结果: 27例中,脑胶质瘤7例、脑膜瘤8例、脑转移瘤8例、颅咽管瘤2例,淋巴瘤、血管母细胞瘤各1例.27例灌注图像均可以清晰显示肿瘤的大小、轮廓,清晰地区分肿瘤和水肿;不同类型肿瘤的CBF、CBV、MTT及PS值不尽相同,灌注伪彩图表现不同;PS图能清晰显示脑肿瘤的实质部分及微血管通透性.结论: MSCT灌注成像对脑肿瘤血流灌注的定量研究提供了新的方法,对了解脑肿瘤内部血流状态及微血管通透性的改变有一定的价值.     

肝脏实时剪切波弹性成像和超声量化评分评价恩替卡韦治疗慢性乙型肝炎肝纤维化疗效的研究

目的评价恩替卡韦治疗慢性乙型肝炎肝纤维化的疗效,并使用肝脏实时剪切波弹性成像和超声量化评分对疗效进行对比分析。方法选择在2017年10月至2018年3月本院收治的54例慢性乙型肝炎肝纤维化患者,对其进行肝脏实时剪切波弹性成像和超声量化检查,之后对患者实施恩替卡韦治疗,治疗周期为1年,治疗后再次实施肝脏实时剪切波弹性成像和超声量检查,对2次检查的各项指标进行对比,分析检查指标的差异。结果治疗前S1-S3期与S4期超声评分、肝硬度进行对比,差异有统计学意义,治疗后患者超声评分、肝硬度(kPa)指标低于治疗前(P<0.05)。结论恩替卡韦治疗慢性乙型肝炎肝纤维化疗效较为显著,同时在进行病情评估的过程中实施肝脏实时剪切波弹性成像和超声量化评分,可以对肝脏疾病的不同阶段进行分期,检查和治疗的效果均较为理想。     

健康志愿者头部MR弹性成像研究

目的 应用MR弹性成像(MRE)技术评估健康志愿者脑组织的剪切模量,并了解脑组织剪切模量与年龄间是否存在相关性.方法 选取105名健康志愿者,其中男42名、女63名,行头部MRE检查.通过局部频率估算法(LFE)分别测量志愿者脑灰质与脑白质的剪切模量.采用独立样本t检验评估脑灰质与脑白质剪切模量间是否存在差异,以及脑实质剪切模量是否存在性别差异;应用Spearman相关分析评估剪切模量与年龄是否存在相关性,并将志愿者分为≤40岁组(76名)和>40岁组(29名),分别进行脑实质剪切模量与年龄间的相关性分析.结果 105名健康志愿者脑白质的剪切模量[(23.1±5.7)kPa]高于脑灰质[(11.3±2.6)kPa],两者间差异具有统计学意义(t=19.34,P<0.01).男性志愿者脑白质与脑灰质的剪切模量分别为(23.4±5.8)、(11.4±2.8)kPa,女性志愿者分别为(22.8±5.6)、(11.1±2.5)kPa.男、女志愿者脑组织间剪切模量值差异无统计学意义(t值分别为-0.534、-0.606,P值均>0.05).年龄相关性分析显示,灰质的剪切模量与年龄呈正相关(r=0.315,P<0.01),白质的剪切模量与年龄无相关性(r=0.183,P>0.05);≤40岁组志愿者灰、白质剪切模量与年龄呈正相关(r值分别为0.251、0.235,P值均<0.05),而>40岁组志愿者脑灰、白质剪切模量均与年龄无相关性(r值分别为0.181、-0.001,P值均>0.05).结论 健康志愿者脑白质的剪切模量明显高于脑灰质;脑实质剪切模量男女之间无差别;脑灰质剪切模量随年龄增加而增加.     

滑动界面成像预测黏附在前庭神经鞘瘤的肿瘤脑组织

正摘要目的通过测试滑动界面成像(SII)临床可行性和实用性来识别和量化前庭神经鞘瘤病人的肿瘤脑组织黏连程度。方法经机构伦理委员会批准并获得书面知情同意后,9例前庭神经鞘瘤病人行SII检查。SII采集过程中,用一个放置在头部线圈中的枕头状设备给头部施加一种低振幅机械振动,通过使用和振动同步的相位对比脉冲序列与运动编码梯度,对产生的剪切波进行成像。在3 T MRI系统上于7 min内完成成像。用2种不同的算法[剪切线分析和八面体剪切应变(OSS)的计算]处理已获得的剪切运动数据,用以识别脑肿瘤的组织粘连程度。在不知道SII结果的情况下,神经外科     

DTI多参数值及DTT技术在颅内肿瘤中的应用研究

目的 探讨MR扩散张量成像(DTI)多参数值在脑肿瘤中的诊断和鉴别诊断价值;评价扩散张量纤维柬成像(DTT)在显示脑肿瘤与周围脑白质纤维束关系中的应用.资料与方法 搜集经手术病理证实的星形细胞瘤(低级别、高级别)、脑膜瘤、转移瘤患者资料(低级别星形细胞瘤15例,高级别星形细胞瘤18例,脑膜瘤16例,转移瘤10例)共59例.行常规T_1WI、T_2WI、增强T_1WI及DTI.测量病灶肿瘤实质区、瘤周水肿区、囊变坏死区、水肿邻近正常白质区及对侧正常白质区的平均扩散系数(DCavg)值、部分各向异性分数(FA)值、1-容积比(1-VR)值及相对各向异性(RA)值,分析各测量值在肿瘤的诊断及良恶性鉴别诊断中的作用.利用DTI数据进行DTT重组病变周围脑白质纤维束,观察肿瘤与脑白质纤维束的关系.结果 低级别星形细胞瘤、高级别星形细胞瘤、脑膜瘤及转移瘤的肿瘤实体、瘤周水肿区的FA值、1-VR值及RA值差异均具有统计学意义(P<0.05);对侧正常白质区DCavg值、FA值、1-VR值及RA值差异均具有统计学意义(P<0.5).FA图、FA彩色编码图、DTT图均能显示脑白质纤维受累情况,而常规MRI难以显示;脑白质纤维束与脑肿瘤的位置关系可分为四型,即推挤型、水肿型、浸润型和破坏型.低级别星形细胞瘤及脑膜瘤良性肿瘤周围的白质纤维束多呈推挤水肿改变,而高级别星形细胞瘤及转移瘤恶性肿瘤周围的白质纤维束多表现为以浸润破坏为主.结论 DTI较常规MRI能更确切、直观地显示脑内肿瘤与周围脑白质的关系,结合FA值、1-VR值及RA值能为肿瘤的诊断及鉴别诊断提供更多的依据;DTT可以为临床提供更多的肿瘤及其周围白质纤维束的信息,指导术前计划的制定和术后的评估.     

Magnetic resonance elastography of the human brain: a preliminary study

Purpose: To study the application of magnetic resonance elastography (MRE) in the human brain.

Material and Methods: An external force actuator was developed, which produced propagating shear waves in brain tissue. A modified phase-contrast gradient-echo sequence was developed. The propagating shear waves within the brain were directly imaged. The wave images were processed to obtain the elasticity image. Shear waves at 100 Hz, 150 Hz, and 200 Hz were applied.

Results: The propagating shear waves in the brain were visualized on wave images. The elasticity image revealed the difference in tissue elasticity between gray and white matter of the brain.

Conclusion: MRE could be an imaging technique for assessing the elasticity of brain tissue.     

Magnetic resonance elastography of brain tumors: preliminary results

PURPOSE: To investigate the potential value of magnetic resonance elastography (MRE) in evaluating the consistency of brain tumors. MATERIAL AND METHODS: Six patients with known solid brain tumor underwent brain MRE studies. Consistency of brain tumors was evaluated at surgery. Correspondence of MRE evaluation with operative result was studied. RESULTS: The elasticity of tumors in six patients evaluated by MRE agreed with the tumor consistency given by the operative results. CONCLUSION: MRE could be used as an imaging technique for noninvasive assessment of the consistency of brain tumor in vivo.     

侵袭性垂体腺瘤:MRI与术中对照研究(附35例回顾分析)

目的:探讨MRI推断侵袭性垂体瘤质地、侵袭性的价值。方法:35例行MR检查侵袭性垂体瘤病人,测量T1WI及T2WI肿瘤信号与脑白质信号的比值和强化前后肿瘤T1WI信号强度比值,与其术中所见及术后病理对照,术中据肿瘤硬度分为质软、中等、硬;术后瘤体送检,结果进行统计学分析。结果:T2WI瘤体与白质信号比值与瘤体质地有明显相关性(P<0.01);MRI所示垂体瘤海绵窦及鞍周侵袭与术中及术后病理总符合率达85.3%。结论:MRI可以在术前准确预测侵袭性垂体瘤的质地、侵袭性。     

Comparison of quantitative shear wave MR-elastography with mechanical compression tests.

The mechanical properties of in vivo soft tissue are generally determined by palpation, ultrasound measurements (US), and magnetic resonance elastography (MRE). While it has been shown that US and MRE are capable of quantitatively measuring soft tissue elasticity, there is still some uncertainty about the reliability of quantitative MRE measurements. For this reason it was decided to determine in vitro how MRE measurements correspond with other quantitative methods of measuring characteristic elasticity values. This article presents the results of experiments with tissue-like agar-agar gel phantoms in which the wavelength of strain waves was measured by shear wave MR elastography and the resultant shear modulus was compared with results from mechanical compression tests with small gel specimens. The shear moduli of nine homogeneous gels with various agar-agar concentrations were investigated. The elasticity range of the gels covered the elasticity range of typical soft tissues. The systematic comparison between shear wave MRE and compression tests showed good agreement between the two measurement techniques.     

Pituitary macroadenomas: preoperative evaluation of consistency with diffusion-weighted MR imaging--initial experience

PURPOSE: To prospectively evaluate use of diffusion-weighted (DW) magnetic resonance (MR) images and apparent diffusion coefficient (ADC) maps for determination of the consistency of macroadenomas. MATERIALS AND METHODS: The study protocol was approved by the institutional ethics committee, and informed consent was obtained from all patients. Twenty-two patients with pituitary macroadenoma (10 men, 12 women; mean age, 54 years +/- 17.09 [standard deviation]; range, 21-75 years) were examined. All patients underwent MR examination, which included T1-weighted spin-echo and T2-weighted turbo spin-echo DW imaging with ADC mapping and contrast material-enhanced T1-weighted spin-echo imaging. Regions of interest (ROIs) were drawn in the macroadenomas and in normal white matter on DW images, ADC maps, and conventional MR images. Consistency of macroadenomas was evaluated at surgery and was classified as soft, intermediate, or hard. Histologic examination was performed on surgical specimens of macroadenomas. Mean ADC values, signal intensity (SI) ratios of tumor to white matter within ROIs on conventional and DW MR images, and degree of enhancement were compared with tumor consistency and with percentage of collagen content at histologic examination by using analysis of variance for linear trend. RESULTS: The mean value of ADC in the soft group was (0.663 +/- 0.109) x 10(-3) mm(2)/sec; in the intermediate group, (0.842 +/- 0.081) x 10(-3) mm(2)/sec; and in the hard group, (1.363 +/- 0.259) x 10(-3) mm(2)/sec. Statistical analysis revealed a significant correlation between tumor consistency and ADC values, DW image SI ratios, T2-weighted image SI ratios, and percentage of collagen content (P < .001, analysis of variance). No other statistically significant correlations were found. CONCLUSION: Findings in this study suggest that DW MR images with ADC maps can provide information about the consistency of macroadenomas.     

High‐frequency mode conversion technique for stiff lesion detection with magnetic resonance elastography (MRE)

A novel imaging technique is described in which the mode conversion of longitudinal waves is used for the qualitative detection of stiff lesions within soft tissue using magnetic resonance elastography (MRE) methods. Due to the viscoelastic nature of tissue, high‐frequency shear waves attenuate rapidly in soft tissues but much less in stiff tissues. By introducing minimally‐attenuating longitudinal waves at a significantly high frequency into tissue, shear waves produced at interfaces by mode conversion will be detectable in stiff regions, but will be significantly attenuated and thus not detectable in the surrounding soft tissue. This contrast can be used to detect the presence of stiff tissue. The proposed technique is shown to readily depict hard regions (mimicking tumors) present in tissue‐simulating phantoms and ex vivo breast tissue. In vivo feasibility is demonstrated on a patient with liver metastases in whom the tumors are readily distinguished. Preliminary evidence also suggests that quantitative stiffness measurements of stiff regions obtained with this technique are more accurate than those from conventional MRE because of the short shear wavelengths. This rapid, qualitative technique may lend itself to applications in which the localization of stiff, suspicious neoplasms is coupled with more sensitive techniques for thorough characterization. Magn Reson Med, 2009. © 2009 Wiley‐Liss, Inc.     

MR扩散张量成像对脑肿瘤的初步应用研究

目的 :评价MR扩散张量成像在脑肿瘤中的应用价值。方法 :搜集经手术及病理证实的脑膜瘤和星形细胞瘤病例共 3 3例 ,行常规MRI、扩散张量成像 (DTI)检查。构建各向异性分数 (FA)图 ,并测量肿瘤及周围白质的FA值。结果 :正常白质纤维在FA图上表现为高信号。在肿瘤存在时 ,周围白质纤维可表现为受推压移位或浸润破坏 ,破坏后FA值降低 ,表现为低信号。这些表现在常规MRI上均未清楚显示。结论 :DTI可清楚显示肿瘤与周围白质纤维的解剖关系 ,指导临床制订手术方案。     

Mechanical transient-based magnetic resonance elastography.

Magnetic resonance elastography (MRE) is a technique for quantifying material properties by measuring cyclic displacements of propagating shear waves. As an alternative to dynamic harmonic wave MRE or quasi-steady-state methods, the idea of using a transient impulse for mechanical excitation is introduced. Two processing methods to calculate shear stiffness from transient data were developed. The techniques were tested in phantom studies, and the transient results were found to be comparable to the harmonic wave results. Transient wave based analysis was applied to the brains of six healthy volunteers in order to assess the method in areas of complex wave patterns and geometry. The results demonstrated the feasibility of measuring brain stiffness in vivo using a transient mechanical excitation. Transient and harmonic methods both measure white matter (approximately 12 kPa) to be stiffer than gray matter ( approximately 8 kPa). There were some anatomic differences between harmonic and transient MRE, specifically where the transient results better depicted the deeper structures of the brain.     

Electromagnetic actuator for generating variably oriented shear waves in MR elastography.

Magnetic resonance elastography (MRE) is a recently developed technique for determining the mechanical properties of biological tissue. In dynamic MRE, electromagnetic units (actuators) are widely used to generate shear waves in tissue. These actuators exploit the interaction between the static magnetic field B(0) and an annular coil supplied with alternating currents. Therefore, coil movements are restricted to selected orientations to B(0). Conventional actuators transfer this movement collinearly to B(0) into the tissue. In this study, an electromagnetic actuator was introduced that overcomes this limitation. It is demonstrated that different directions of mechanical excitation can be generated and monitored by MRE. Different spatial components of the propagation of the shear waves were determined using agarose phantoms. The technique allows maximum contrast for MRE images of objects with anisotropic strain components such as muscle tissue.