磁共振成象仪定期图像质量测试

磁共振成像仪安装以后,可靠性能会随着使用和时间而降低。为使MRI设备能够正常运作,提高图像质量,应对设备进行定期的质量保证检测。 材料和方法 一、磁共振成像设备和主要的QA检测参数:1.检测设备,荷兰Philips GYROSCAN ACS-NT15 1.5Tesla超导磁共振成像仪。使用直径200mm标准测试模,头部正交线圈及体阅正交线圈进行扫描。2.主要QA的检测参数:信噪比(SNR);场强的均匀度(Flood field uniformity);空间线性度(Spatial inearity);空间分辨率(Spatial resolution);层面投影(Slice profile)与层厚。     

基于动态增强MRI影像组学参数的观察者一致性研究

目的:基于动态增强磁共振成像(magnetic resonance imaging,MRI),探讨不同观察者人工勾画三维感兴趣区(region of interest,ROI)所获影像组学参数的一致性.方法:选取复旦大学附属肿瘤医院收治的确诊为乳腺癌的患者62例.应用ITK-SNAP图像勾画软件对肿瘤进行三维ROI病灶...     

磁共振成像质量保证与质量控制教学研讨班

对磁共振设备进行科学而合理的质量保证（QA）与质量控制（QC），使磁共振成像系统能够正常高效运行，从而确保其能为医学诊断和科学研究提供可靠的图像、高质量的数据极为重要。近几年，我国许多临床医生和科研人员开始认识到磁共振成像质量保证和质量控制的必要性，然而对于其确切概念尚无系统的了解，对QA和QC的具体实施也缺乏经验。     

采用分水岭分割方法获取功能磁共振激活图感兴趣区

目的 为功能磁共振中的功能连接研究提供一种更为合适的感兴趣区(ROI)获取方法.方法 20名正常被试者完成视觉任务扫描,对视觉任务组水平激活图利用分水岭算法进行功能分割.结果 分水岭方法町得到单峰的、空间上互相独立的激活区.结论 分水岭方法可以将较大的、有多个激活峰值的功能团块分割为空间上相互独立的单峰脑区,克服了单纯采用激活程度阈值来产生ROI的方法之缺点,为下一步的功能连接分析提供了一种选择ROI的方法.     

基于PC Matlab平台的扩散张量参数的计算

本文介绍了在普通计算机上根据磁共振成像系统测量所得到的扩散张量数据计算扩散张量参数的方法,并且基于Matlab编程语言实现了目前应用较广的临床参数,如表观扩散系数、扩散张量的最大特征值、特征向量以及各向异型扩散系数FA等的计算.     

回波时间对脑组织弥散张量成像定量指标的影响

目的 研究回波时间对脑弥散张量成像定量指标有无影响.方法 对7只健康成年恒河猴用3.0T磁共振设备行弥散张量成像(DTI).在固定其他参数的情况下改变回波时间(75～160 ms,共13个采样点).选择双侧内囊后肢和壳核分别作为白质和灰质感兴趣区(region of interest,ROI).并测量该ROI内的平均弥散率(mean diffusivity,MD),分数各向异性(fractional anisotropy,FA),最大本征值(λ1).中间本征值(λ2)和最小本征值(λ3).使用Pearson回归分析这些弥散指标与回波时间(TE)的线性关系.结果 恒河猴脑灰质区MD与TE正相关(P<0.001),白质区MD与TE相关性不显著(P>0.05).两ROI内的FA和λ1均与TE正相关,λ3与TE负相关(P<0.001).灰质区λ2与TE正相关,而白质区λ2与TE负相关(P<0.001).结论 回波时间可影响DTI定量指标的测量.在临床多中心研究中,需要对之进行控制.     

ROI选择方法对高级别胶质瘤增强T1WI直方图参数的影响

目的 观察高级别胶质瘤增强T1WI直方图分析中选择不同ROI的可重复性及对测量直方图特征参数的影响。方法 2名医师分别使用4种方法（小ROI法、轮廓ROI法、阈值ROI法和体积ROI法）选择ROI对45例高级别胶质瘤增强T1WI进行直方图参数测量,评价观察者间一致性及测量直方图参数的差异。结果 2名医师采用体积、轮廓和阈值ROI法测量平均值、标准差和峰度值均一致性好（ICC均≥ 0.80）,偏度值一致性为中等至好（ICC为0.73~0.90）,采用小ROI法测量直方图特征参数的一致性为较低至中等（ICC为0.30~0.69）。体积ROI法测量各直方图特征参数与轮廓ROI法比较差异均无统计学意义（P均>0.05）;阈值ROI法测量平均值、偏度值、峰度值均高于体积和轮廓ROI法,标准差均低于体积和轮廓ROI法（P均<0.05）;小ROI法测量标准差均低于体积和轮廓ROI法（P均<0.05）。结论 采用体积ROI法测量高级别胶质瘤增强T1WI图像直方图特征参数一致性最高;不同方法选择ROI对增强T1WI图像直方图特征参数测量结果存在一定影响。     

脑功能区自动提取法对强迫症99mTc-ECD脑显像分析

目的采用脑功能区自动提取法分析一组强迫症患者的脑SPECT血流灌注显像,并与ROI比较看是否有优势。方法采用以前一组强迫症患者和正常人的SPECT显像资料,将图像经旋转和形变配准到标准Talairach坐标空间中去,按不同脑区名称将不同脑解剖功能区立体区勾画提取,计算其灰度值,并计算与全脑灰度比值,比较左右脑之间、正常组与患病组间的差异。结果该方法成功提取不同脑功能区,正常组与异常组比较,发现了比ROI方法更多血流改变区。正常组与患者组左右比较也显示左右多区域不对称。结论强迫症患者发作期显示以双侧颞叶多个区域血流降低,并见背侧丘脑等局部血流增高为特点,脑功能区自动提取分析具有比ROI更高检出效率。     

利用磁共振相位对比法对非搏动流体模型的定量测量研究

目的探讨流动液体模型的磁共振信号强度与速度矢量的关系,研究不同观察者之间、不同ROI(0.05cm2、0.08cm2)流速软件的客观性。方法采用西门子1.5T超导磁共振机梯度进行实验研究,实验水模包括,一塑胶管(模拟门静脉走行,直径3.3mm),高压注射器一台,生理盐水2000ml。流速设置1.25~12.50cm/s。结果磁共振信号强度Y与流速X呈线性关系,Y=-24.542 123.104X,相关系数为r2=0.948;不同观察者采用流速软件测量的速度矢量三者间比较及与实际速度(真值)比较,均无显著性差异(P>0.05);观察者选择不同ROI范围0.05cm2、0.08cm2测量速度矢量与实际流速(真值)行相关性分析,r分别为0.935和0.998,ROI0.08cm2相关性更佳。结论流动液体模型证明磁共振相位对比技术是一种客观、准确的流体定量测量技术,可用于临床血流定量研究。     

MR流量测定面积的实验研究

目的:实验研究MR流量测定中不同流量、不同流向、不同感兴趣区(ROI)位置与不同ROI面积的关系。材料与方法:使用PHILIPS1.5T双梯磁共振机流量测定程序,测量2mm内径塑胶管不同流量水(0.5、1.0、1.5、2.0、2.5ml/s),不同流向(流入及流出方向)、不同ROI位置(测量图中心区和偏中心区)与不同的ROI面积流量变化关系,统计计算标准的ROI面积。结果:在不同流量、流向和测量位置中,流量与ROI面积大小存在明显的直线相关(r>0.95,P<0.05),ROI面积大小显著的影响测量结果,相位编码图的面积均大于实际面积,当ROI面积取值等于实际面积时,所测结果与实际流量一致。在不同流量下的不同流向及ROI位置对流量测定无影响(P>0.05)。结论:MR流量测定ROI面积必须与实际面积一致。     

Noninvasive ultrasonic measurement of regional and local pulse-wave velocity in mice

Mouse models of human disease are increasingly used to study the nature of cardiovascular diseases such as atherosclerosis. The pulse wave velocity (PWV) provides an indirect measure of arterial stiffness and can be useful for characterizing disease progression. In this study, the PWV was measured noninvasively in the left common carotid artery of seven young mice using two image-guided approaches: a regional transit-time (TT) method and a local flow-area (QA) method. The QA approach measures the cross-sectional area and volume flow through the vessel using high frame-rate retrospective colour flow imaging. The QA method was found to correlate well with the TT method (r2=0.80, p<0.001). The mean difference between methods was 0.05+/-0.21 m/s. This study demonstrates the feasibility of measuring both regional and local PWV in mice using image-based high-frequency ultrasound methodologies.     

Quality Assurance in Medical Imaging: A Review of Challenges in Nigeria

There is reported increased utilization of diagnostic imaging worldwide, owing to technological advancement and increased diagnostic capability of evolving medical imaging modalities. However, there are concerns that the increasing use of radiation for medical imaging is not being properly managed because of substantiated lack of adequate quality assurance (QA) implementation in majority of diagnostic imaging departments and centers in Nigeria. A broad literature search was conducted using the PubMed, Elsevier, ScienceDirect, and Springer Link. The keywords quality assurance, quality control, optimization, and radiation dose were combined with the terms implementation, challenges, medical imaging, and Nigeria as identifiers to recognize articles focusing on the challenges of QA and quality control (QC) in diagnostic imaging in Nigeria. Fifty-nine articles were identified in literature search. Factors and challenges inhibiting effective QA implementation including management and policies, QC equipment, QC culture and familiarity, skilled personnel, radiology benefit management, and regulatory enforcement were identified and discussed. An illustration of typical frequency of QC evaluations in some x-ray imaging systems was provided. This is expected to guide QC personnel and centers on selection and execution of QC evaluations.     

定量动态增强磁共振成像技术在直肠癌的研究进展

直肠癌的血管生成是肿瘤发生、发展、转移的重要因素之一。定量动态增强MRI(dynamic contrast-enhanced MRI,DCE-MRI)技术可通过小分子钆对比剂无创地对组织血管特征进行评价。利用快速T1WI对感兴趣部位进行连续动态扫描,并获得感兴趣区像素点的时间-信号强度曲线,运用药代动力学模型对时间-信号强度曲线进行分析,计算出感兴趣区组织或病变部位的微循环渗透性或组织灌注的血流动力学参数,如对比剂容积转运常数(volume transfer constant,K~(trans))、血管外细胞外间隙体积分数(extracellular volume fraction,Ve)、速率常数(exchange rate constant,K_(ep))值等。作者对定量DCE-MRI的基本原理及其在国内外直肠癌诊断、肿瘤分级分期及疗效评价等方面的研究进展予以综述。     

肾动态显像测定肾小球滤过率的影响因素

肾小球滤过率(GFR)是评价肾脏功能的重要指标,99锝-二乙三胺五乙酸(99Tcm-DTPA)肾动态显像是临床最常用的测定GFR的检查方法.但多种因素可能影响测定结果,如99Tcm-DTPA与血浆蛋白的结合、感兴趣区、本底、肾脏深度、病人的年龄等.本文将就这些影响因素进行综述.     

等宽探测器多层螺旋CT直接薄层扫描与回顾性薄层重建的图像质量对比

目的：探讨最新的等宽探测器多层螺旋CT直接薄层扫描与回顾性薄层重建图像质量。方法：GE Lightspeed Ultra QA模扫描及患者头部、胸部、腹部各50例进行CT扫描，比较直接薄层图像及回顾性薄层重建图像质量。结果：在扫描条件及重建算法相同情况下，直接薄层扫描图像与回顾性薄层重建图像质量基本一致。结论：等宽探测器多层螺旋CT的回顾性薄层重建基本可以取代直接薄层扫描。     

A 3-D Region-Growing Motion-Tracking Method for Ultrasound Elasticity Imaging

A 3-D region-growing motion-tracking (RGMT) method for ultrasound elasticity imaging is described. This 3-D RGMT method first estimates the displacements at a sparse subset of points, called seeds; uses an objective measure to determine, among those seeds, which displacement estimates to trust; and then performs RGMT in three dimensions to estimate displacements for the remaining points in the field. During the growing process in three dimensions, the displacement estimate at one grid point is employed to guide the displacement estimation of its neighboring points using a 3-D small search region. To test this algorithm, volumetric ultrasound radiofrequency echo data were acquired from one phantom and five in vivo human breasts. Displacement estimates obtained with the 3-D RGMT method were compared with a published 2-D RGMT method via motion-compensated cross-correlation (MCCC) of pre- and post-deformation radiofrequency echo signals. For data from experiments with the phantom, the MCCC values in the entire tracking region of interest averaged approximately 0.95, and the contrast-to-noise ratios averaged 4.6 for both tracking methods. For all five patients, the average MCCC values within the region of interest obtained with the 3-D RGMT were consistently higher than those obtained with the 2-D RGMT method. These results indicate that the 3-D RGMT algorithm is able to track displacements with increased accuracy and generate higher-quality 3-D elasticity images than the 2-D RGMT method.     

丘脑在经皮穴位电刺激镇痛效果中的作用

目的探讨丘脑在经皮穴位电刺激镇痛中的作用。方法选择健康受试者14例(男7例,女7例),依次在基础阶段和经皮穴位电刺激30 min后行功能磁共振(fMRI)扫描。选取丘脑为感兴趣脑区,应用SPM软件对所有试验数据进行处理。结果经皮穴位电刺激后,与丘脑功能连接减弱的脑区包括双侧楔前叶、双侧顶上小叶、左侧颞下回、右侧颞中回、右侧额中回;与丘脑功能连接增强的脑区包括双侧小脑、双侧岛叶、基底神经节、双侧额下回、左侧额叶眶回、左侧颞上回(P<0.005,cluster>10mm3)。结论丘脑在经皮穴位电刺激镇痛的中枢镇痛机制中起到了重要作用。小脑、楔前叶、岛叶、基底神经节、顶上小叶、额叶眶回、额中回、额下回、颞叶等脑区与丘脑间功能连接的改变是丘脑镇痛机制的重要组成部分。     

Quality-assurance research: studying processes of care

To conduct a successful research study, several criteria must be satisfied: the research question must be important (not only to the investigators but to clinicians and managers in other institutions); the research question must be answerable with the available resources; the investigators must be motivated and capable; and the research setting must be appropriate for the study (the institution must have a supportive culture and analytical resources, and the local institutional review board must approve the proposed study). Quality-assurance (QA) research poses some special challenges and requirements. First, although QA studies should be hypothesis-driven, they are usually before-and-after studies, rather than randomized controlled trials. Second, in before-and-after studies the investigators must address and minimize several possible sources of bias that could confound the results. For example, the compared groups must be similar in important features that could affect development of the outcome(s) of interest, and clinical practices other than the practice change that is being tested during the study must be shown not to independently affect the outcome(s) of interest. We discuss several examples of QA studies, and we offer a checklist for the process of considering, designing, executing, presenting, and publishing a QA study.     

丘脑在舒芬太尼中枢镇痛中的作用

目的探讨舒芬太尼的中枢镇痛机制。方法选择健康受试者17例(男8例,女9例),依次在基础阶段和靶控输注舒芬太尼(0.2 ng/ml)后行功能磁共振(fMRI)扫描。选取丘脑为感兴趣脑区,应用SPM软件对所有实验数据进行处理。结果靶控输注舒芬太尼后,与丘脑功能连接减弱的脑区包括双侧额叶直回、左侧额叶眶后回;与丘脑功能连接增强的脑区包括双侧小脑、右侧扣带回及左侧颞中回(P<0.001,cluster>13 mm3)。结论丘脑是舒芬太尼中枢镇痛机制中起到重要作用的脑区。额叶直回、左侧额叶眶后回、右侧扣带回、小脑及左侧颞中回与丘脑间功能连接的变化可能是舒芬太尼中枢镇痛机制中的重要组成部分。     

磁共振扩散张量成像在显示正常人脑白质纤维中的应用

目的应用DTI技术显示正常人脑白质纤维,探讨其与解剖学描述的一致性。方法20名健康志愿者行颅脑MRI与颅脑单次激发回波平面扩散张量成像扫描(b值=0,500s/mm2),在SiemensLeonardo工作站应用纤维束跟踪软件(SiemensStandar12dirs)进行后处理重建出白质纤维束。结果对主要白质纤维如皮质脊髓束、皮质核束、胼胝体、扣带、上纵束、下纵束、上枕额束、下枕额束、钩束进行模拟显示,不同纤维需要选择适合的感兴趣区、各向异性阈值、角度阈值、步长和体素内采样数目等参数,显示结果与解剖学描述具有较好的一致性。结论利用扩散张量成像技术可模拟显示正常人脑白质纤维,与解剖学描述具有较好的一致性,是在活体中研究人脑白质纤维的一种较可靠的方法。