正常中脑导水管脑脊液MR流速流量研究

目的探讨中脑导水管脑脊液(CSF)流速、流量测量正常值。方法应用Philips Intera Achieva 1.5TMR机对30例健康志愿者行导水管MR相位对比法CSF-QF序列扫描,用流动分析软件测量中脑导水管脑脊液速、流量。结果中脑导水管截面像素为13.73±3.59,导水管CSF的上峰速度为(6.40±1.85)cm/s,下峰速度为(7.88±3.04)cm/s,上峰流量为(0.12±0.05)ml/s,下峰流量为(0.15±0.07)ml/s,返流系数为(90.86±6.79)%,绝对流量为(0.07±0.05)ml/s,平均流速值为(0.01±0.18)cm/s。中脑导水管CSF搏动性流动与心动周期的关系为正弦波形。结论建立了Philips Intera Achieva 1.5T中脑导水管脑脊液流速、流量正常值。     

横窦血液流量MR测量初步研究

目的 探讨用横窦血液流量MR测量方法判断静脉引流优势的临床应用价值。资料与方法 47例健康志愿者和排除颅内占位性病变、中风和静脉窦血栓者接受了MRI检查。每位受检者均进行了窦汇区MR血流成像和VIGRE邢序列横窦血流量测量。结果 MR血流成像显示右侧占优势者32例,左侧占优势者10例,等优势者5例。横窦血流量测量值反映的优势侧情况与之相符合。结论 MR是一种有效的横窦血液流量测定方法,可以从“量”的角度反映引流优势。MRA和流量测定相结合能为临床提供更多的信息。     

关节软骨损伤MR成像序列的实验研究

目的 评价关节软骨缺损检查的各种MRI扫描序列。材料与方法 选用猪膝关节10只，制成宽度不等，深度为软骨全层的小槽状软骨缺损，MRI序列包括T1加权自旋回波序列（SE-T1），质子和T2加权快速自旋双回波序列（FSE-PD/T2），附加脂肪抑制的质子和T2加权快速自旋双回波序列（FS-FSE-PD/T2），附加脂肪抑制的三维快速扰相梯度回波序列（FS-3D-SPGR），液体衰减反转恢复序列（FLAIR），短TI翻转回波序列（STIR）和T1加权反转恢复序列（IR-TI700）。结果 与常规膝关节检查的FSE-PD/T2序列比较，FS-FSE-PD/T2能够分辨软骨与软骨下骨的界限，可测量软骨缺损厚度和深度；FS-3D-SPGR的软骨信噪比（SNR）和其对软骨下骨，关节液等关节软骨周围组织的对比噪声比（CNR）最高；IR-TI700测量的软骨缺损宽度和深度，与实际测量值的一致性最好，FLAIR和STIR不能清楚分辨软骨和软骨下骨的界限。结论 FS-FSE-PD/T2应作为膝关节检查的常规序列；三维抑脂梯度回波序列仍为关节软骨检查的最佳扫描序列。翻转回波扫描序列在关节软骨检查方面具有潜在的临床价值。     

液体流率MR测量实验研究

目的:探讨稳定流动状态下磁共振信号强度与液体流速关系,为横窦血流量测定提供适当方法.材料和方法:在实验水模上放置内径3.4mm塑胶管,用高压注射器以不同的流量向管道内注入水,流量的变化范围从0.1～1.6ml/s.用1.5T超导磁共振仪单个无门控2D PC序列进行扫描,对液体磁共振信号强度和管道内实际流速采用相关回归分析方法进行统计分析.结果:磁共振信号强度(y)和液体速度(x)呈明显线性关系,y=68.914x 357.206,R2=0.998.结论:相位对比法是一种有效的流量测量方法.     

兔肝MR灌注表现的实验研究

目的 探讨兔正常肝脏的MR灌注特征.方法 新西兰大白兔10只,体重2.5～3.0 kg,分别进行MR灌注成像.采用TFE序列.灌注成像参数:矩阵89×256,TR 4.3 ms,TE 1.4 ms,激励次数1,视野355 mm×75 mm,层厚5 mm,间距1 mm,NSA为1次.扫描层面数4层,每层反复激励65次,总扫描时间为1 min 20 s.将原始图像输入到PHILIPS后处理工作站(VIEWFORUM),自动生成MR灌注图.分析MR灌注图像及不同组织MR灌注成像特点.结果 肝血容量(HBV)图、肝血流量(HBF)图清楚勾画出肝脏轮廓.腹主动脉强化曲线,表现为速升速降,MR信号强度峰值496±131,肝静脉表现为逐渐升高,MR信号强度峰值323±92,强化时间比腹主动脉晚.正常肝组织强化曲线,呈缓慢升降,MR信号强度峰值194±58.腹主动脉、肝静脉及正常肝组织MR信号强度峰值的比较有统计学差异(F=10.27,P=0.012).结论采用TFE序列可成功进行兔MR灌注成像,HBV图、HBF图清楚勾画出肝脏轮廓,强化曲线可初步反映兔肝脏不同组织的血流情况.     

脂肪肝MR氢质子波谱成像定量分析的初步研究

目的探讨MR氢质子波谱（^1H-MRS）技术定量检测脂肪肝的可行性。方法对20例脂肪肝患者及11例健康志愿者行CT平扫、常规MR扫描及^1H-MRS检查，所有脂肪肝患者MR检查当天均行血清肝功能检查。^1H-MRS测量水和脂质波峰峰值和波峰下面积，计算脂质相对含量，并比较其与CT检查结果及肝功能各指标的一致性。结果正常组及脂肪肝组CT值分别为：（59±9）、（24±11）HU，正常组MRS可见明显高耸的水峰及低平的脂质峰，脂肪肝组可见明显高耸的水峰及低于水峰的脂质峰。正常组及脂肪肝组脂质峰峰值分别为：（0．05±0．01）×10^5、（0．70±0．24）×10^5（t=4．32，P〈0．05），水峰峰值分别为（1．80±0．52）×10^5、（1．85±0．47）×10^5（t=1．26，P〉0．05）；脂肪峰值下面积分别为：（1．36±O．73）×10^9、（2．35±1．15）×10^9（t=5．21，P〈0．05），水峰峰值下面积分别为（4．33±1．28）×10^11、（3．55±0．94）×10^11（t=2．04，P〉0．05）。结论^1H-MRS技术定量检测脂肪肝是可行的，而且是一种非创伤性早期定量检测脂肪肝的方法。     

CD40突变体靶向MR分子成像探针制备及体外卵巢癌成像的实验研究

目的 探讨超微超顺磁氧化铁(USPIO)粒子负载的,CD40突变体抗体分子探针的构建方法和其生物、理化性状,以及在体外对卵巢癌的靶向作用.方法 采用化学交联法将单克隆抗体交联于二巯基丁二酸(DMSA)修饰的USPIO,形成具有免疫活性的分子探针,进行磁学性能鉴定.USPIO标记的抗人CD40突变体单克隆抗体5H6(5H6-USPIO)作为实验组,USPIO标记的抗人CD40单克隆抗体5C11(5C11-USPIO)及USPIO为对照组.通过流式细胞术、共聚焦显微镜及普鲁士蓝染色分析其体外生物学特性,采用3.0T MR对探针与高表达CD40突变体卵巢癌(HO8910)进行体外细胞成像.信号变化数据组间比较采用单因素方差分析和LSD检验.采用Cell Counting Kit-8试剂盒检测探针对HO8910细胞的增殖影响.结果 携带USPIO的抗CD40突变体分子探针被成功构建并分离纯化.合成的探针同USPIO相比具有相似的磁学特性和良好的稳定性.流式细胞术、共聚焦显微镜及普鲁士蓝染色证实抗体分子探针能够特异性识别HO8910细胞表面的CD40突变体,对细胞HO8910的增殖无影响.体外MRI显示探针同HO8910细胞结合后T2、T2*值明显缩短,T2图像较对照组明显变暗.5H6-USPIO组的T2、T2*弛豫时间分别为(40.05±1.62)、(3.08±0.11)ms,短于5C11-USPIO[分别为(85.38±4.74)和(11.82±1.00)ms]和USPIO组[分别为(91.62±3.35)和(13.60±1.92)ms],差异均有统计学意义(F值分别为196.29、60.73,P值均＜0.01),而5C11-USPIO、USPIO两组T2、T2*弛豫时间差异无统计学意义(P值均＞0.05).结论 化学交联法可制备出CD40突变体单克隆抗体超顺磁氧化铁粒子探针,该探针具有良好磁学特性及较高生物活性,能够特异性识别卵巢癌细胞HO8910.     

MR弹性成像与T2WI评价组织质地的初步对照实验研究

目的 初步比较MR弹性成像(MRE)和T2WI评价组织质地的准确性.方法 分别制作浓度为0.8％～3.0％的琼脂凝胶体模(共23个).所有体模均行矢状面正中层面MRE扫描和T2map扫描,将所得MRE原始图像经局部频率估算法(LEF)计算后,测得扫描层面的剪切模量,将所得T2map原始图像经GE公司ADW4.3工作站后处理后,测得扫描层面的T2值.应用Pearson相关性分析判断剪切模量与琼脂凝胶体模浓度、T2值与琼脂凝胶体模浓度是否存在相关性,采用秩和检验判断相关性的大小.结果 成功获取所有琼脂凝胶体模矢状面正中层面的剪切模量、T2值,二者均呈正态分布,剪切模量值为(49.1 ±23.5)kPa、T2值为(57.8 ±21.8)ms.剪切模量与琼脂凝胶体模浓度呈正相关(r1=0.985,r12=0.970,P＜0.01).T2值与琼脂凝胶体模浓度呈负相关(r2=-0.901,r22 =0.812,P＜0.01)).剪切模量与T2值相比,与琼脂凝胶体模浓度的相关性更好(Z =5.459,P＜ 0.01).结论 与T2WI相比,MRE能更准确地反映组织的质地,有良好的临床应用前景.     

MR灌注加权成像在兔VX2软组织肿瘤中应用的实验研究

目的：初步评价MR灌注加权成像方法在软组织肿瘤中的应用价值。方法：10只新西兰大白兔，在其一侧大腿近段注射VX2肿瘤组织悬液0．1ml，分别于肿瘤组织接种后第14天、21天行MR平扫和灌注扫描，扫描图像经AW4．0工作站处理，计算灌注参数(包括相对血流量rBF、相对血容量rBF和平均通过时间MTT)并分析灌注曲线图。随后将荷瘤兔处死并取出肿瘤，用10％福尔马林固定，于光学显微镜下观察肿瘤组织的结构特点。结果：所有兔大腿VX2肿瘤组织的rBF、rBV值明显高于正常肌肉组织，而MTT值则低于正常肌肉组织。结论：MR灌注加权成像是一种安全、简便且较准确的半定量评估软组织肿瘤性病变血流灌注状态的功能成像方法，它可以为肿瘤治疗方案的制定、治疗后的疗效监测以及预后判断提供重要的参考依据。     

顺磁性对比剂Gd-DTPA-DG 的制备及其在肺癌裸鼠模型活体MR实验研究

目的 合成一种顺磁性脱氧葡萄糖类MR对比剂二乙三胺五乙酸-脱氧葡萄糖钆盐(Gd-DTPA-DG)并探讨其在荷瘤裸鼠体内肿瘤信号改变的规律.方法 首先合成DTPA-DG ,再与Gd2O3螯合,制得Gd-DTPA-DG.采用荷瘤裸鼠体内实验模型,将裸鼠随机分成实验组与对照组(n=10),前者尾静脉注射Gd-DTPA-DG,后者尾静脉注射含相同Gd3+浓度(0.1 mmol/kg)的Gd-DTPA, 测量SE T1WI平扫及引入对比剂30 s、2 min、5 min、 10 min、20 min、30 min、45 min、1 h、2 h后瘤体信号强度,并计算对比度噪声比(CNR).将右侧前肢肌肉组织信号变化作为参照物,并进行统计分析.结果 Gd-DTPA-DG比Gd-DTPA在肿瘤组织内表现为更强且更持久的强化.注射对比剂30 s后,实验组裸鼠瘤体信号增加与扫描前差异没有统计意义(P=0.171),在30 min左右差异性最大(P<0.001).对照组5 min时前后差异最大(P<0.001),但2 h时即与注射前没有显著差异性(P=0.057).结论 Gd-DTPA-DG 可在肺癌模型活体内起到肿瘤强化作用,是一种新型顺磁性Gd(III)类糖代谢MR对比剂.     

脑血液流动磁共振定量技术的流体力学实验研究

目的：通过建立适当的流体模型,评价磁共振相位对比电影法对流体定量测量的可行性及准确性。方法：用磁共振相位对比电影法测定模拟脑血液流动的管状模型稳态流动下流体信号强度。并与相应的速率进行相关性分析后分别得出相应的转换函数关系。运用该转换函数选择性测量稳态及脉冲流动下管腔内各点的流体速率,并与相应激光多普勒测速对比分析以验证其测量准确性。结果：流体信号强度与对应速率呈线性相关,相关系数为0.985;相应信号强度（Y）和流率（X）的转换函数为Y=-0．0908X^2＋24.176X-15.304。不同流量状况下重复测量后,比较两次测量信号强度结果差异无显著性意义（P〉0．05）。两次测量值与实际值比较,测量误差均≤10％。磁共振相位对比电影法与激光多普勒测速仪测量的流率比较．两组数据相关性良好（P〈0.01,r=0.933）。结论：磁共振相位对比电影法是一种有效的脑血流定量技术,选择适当的扫描参数、准确的图像后处理及转换函数是确保该方法测量准确性的基础。     

Turbine flow sensor for volume-flow rate verification in MR

A turbine flow sensor for MR flow experiments has been evalusted using reference volume-flow rate measurements obtained using an electromagnetic (EM) flow meter measurements and simultaneous phase contrast (PC) MR acquisitions. After calibration, the device was found to have accuracy (compared with the EM flow meter), linearity, and precision of better than ±1%, ±3.5%, 3.5%, respectively, in constant flow mode (0 to 30 ml s^?1). The frequency response of the flow sensor was flat (within ±10%) up to 13.9 Hz. Volume-flow rate measurements on constant and simulated physiologic flow waveforms were in close agreement with both the electromagnetic (EM) flow meter and the gated MR PC estimates.     

Analysis of systematic and random error in MR volumetric flow measurements

The spatial aspects of error in 2D MR cine phase-velocity mapping are considered in order to define acquisition strategies which will minimize error in measuring volumetric flow. Error was separated into two categories: systematic and random. Potential sources of systematic error examined were intravoxel phase dispersion (IVPD), partial volume effects, misalignment of flow axis and flow-encoding gradients, and improper choice of vessel voxels for flux calculations. Random error was addressed using analysis of propagation of variance. Analytical expressions for sources of error were derived; and computer models were used to test the analytical models. Flow phantom studies examining error in MR volumetric flow measurements were performed and compared with error predicted by the analytical models. Expected error in several clinical situations of interest was then derived to find appropriate acquisition strategies. Spatial resolution, signal to noise ratio, velocity sensitivity and the ratio of the modulus of moving isochromats to that of static isochromats were found to be the most important parameters in controlling error and were found to cause competing effects with respect to systematic and random error.     

Dual dynamic contrast-enhanced MR imaging

A method was devised for obtaining dynamic contrast-enhanced T1-weighted and relaxation rate (ΔR2*) images simultaneously to evaluate regional hemodyn-amics of the brain tumors. On a 1.5-T MR system, dual dynamic contrast-enhanced images were obtained using a gradient echo (dual echo fast field echo) pulse sequence with the keyhole technique to improve temporal and spatial resolution during a rapid bolus injection of gadopentetate dimeglumine. The dynamic T1 contrast images were obtained from the first echo; moreover. ∫ ΔR2*dt values were calculated from the first and the second echo images. The dynamic T1 contrast images provided information about characteristic enhancement pattern (vascularization and disruption of bloodbrain barrier), and the f ΔR2*dt values provided a map of regional blood pool in tumor site, peritumoral edema, and other surrounding regions of the brain. The ability to obtain dynamic contrast-enhanced T1 contrast and ΔR2* imaging at the same time allows optimization of the advantages of each and thereby more information about the microvascular circulation of the brain lesions.     

Development and evaluation of tracking algorithms for cardiac wall motion analysis using phase velocity MR imaging

Phase velocity magnetic resonance imaging (MRI) has shown considerable potential for tracking distinct regions of the myocardium throughout the cardiac cycle. Phase contrast MR imaging produces multiple images, each phase encoded for velocity in a different direction, in which individual pixels depict the local motion of the tissue. In this work we present in detail three algorithms for tracking motion based on these images. Both simulated and phantom data are used to examine some of the problems encountered in practice in tracking points based on velocity maps. Solutions to these problems are offered when possible. The impact of noise and low order phase errors in the data on each of the three tracking approaches is examined. In addition, problems due to tissue expansion and contraction, to 2D versus 3D tracking, and to round off errors from motion which is small relative to pixel size or slice thickness, are considered. An example using data obtained in vivo is included to demonstrate the efficacy of the best of the three tracking algorithms in measuring left ventricular circumferential shortening preinfarct and postinfarct in a canine model.     

Utility of phase contrast MR imaging for assessment of pulmonary flow and pressure estimation in patients with pulmonary hypertension: Comparison with right heart catheterization and echocardiography

Purpose:

To compare the utility of phase contrast MR imaging (PC‐MRI) for assessment of pulmonary flow and pressure estimation with that of right heart catheterization and echocardiography (cardiac US) in patients with pulmonary arterial hypertension (PAH).

Materials and Methods:

Twenty consecutive patients with suspected PAH underwent PC‐MRI, cardiac US, and right heart catheterization. In each patient, PC‐MRI was acquired by cine 2D‐PC method on a 1.5 Tesla scanner, and stroke volume (SV) and pulmonary arterial systolic pressure (PASP) were assessed by using the modified Bernoulli's equation. To evaluate the agreements of SV and PASP among the three methods, correlations and limits of agreement among the three methods were statistically assessed by using the Bland‐Altman's analyses.

Results:

The correlations and limits of agreement for SV and PASP between PC‐MRI and catheterization (r = 0.96, r² = 0.94, 1.1 ± 6.9 mL and r = 0.94, r² = 0.88, ?3.2 ± 14.5 mmHg, respectively) were better than between cardiac US and catheterization (r = 0.01, r² < 0.01, 8.9 ± 42.1 mL and r = 0.86, r² = 0.72, ?5.9 ± 27.7 mmHg, respectively).

Conclusion:

PC‐MRI is more compatible with right heart catheterization than cardiac US in pulmonary flow and pressure estimation. J. Magn. Reson. Imaging 2009;30:973–980. © 2009 Wiley‐Liss, Inc.

     

Quantification of blood flow in the middle cerebral artery with phase-contrast MR imaging

The aim of this study was to assess blood flow in the middle cerebral artery (MCA) according to age, gender, and side. Eighty-eight subjects without carotid obstruction were measured for mean velocity, vessel area, and volume flow rates of both MCA with phase-contrast MR. A high-resolution sequence with a matrix of 300 × 512 and a double oblique localizing strategy was used for measurement. A mean velocity of 33 ± 6.8 cm/s, a mean vessel area of 6.2 ± 1.2 mm² and a mean flow rate of 121 ± 28 ml/min were measured in the MCA. Lower volume flow rates were seen in subjects aged over 50 years (p < 0.01). When comparing women with men, a lower vessel area (p < 0.05) of the MCA was counterbalanced by a higher velocity, resulting in no significant difference of the volume flow rate. No difference occurred between the right and the left side. Flow reduction occurs in the elderly. A lower vessel area of the MCA in women is compensated by a higher velocity. Received: 3 September 1999; Revised: 17 January 2000; Accepted: 23 February 2000     

CSF Flow Quantification of the Cerebral Aqueduct in Normal Volunteers Using Phase Contrast Cine MR Imaging

Objective

To evaluate whether the results of cerebrospinal fluid (CSF) flow quantification differ according to the anatomical location of the cerebral aqueduct that is used and the background baseline region that is selected.

Materials and Methods

The CSF hydrodynamics of eleven healthy volunteers (mean age = 29.6 years) were investigated on a 1.5T MRI system. Velocity maps were acquired perpendicular to the cerebral aqueduct at three different anatomical levels: the inlet, ampulla and pars posterior. The pulse sequence was a prospectively triggered cardiac-gated flow compensated gradient-echo technique. Region-of-interest (ROI) analysis was performed for the CSF hydrodynamics, including the peak systolic velocity and mean flow on the phase images. The selection of the background baseline regions was done based on measurements made in two different areas, namely the anterior midbrain and temporal lobe, for 10 subjects.

Results

The mean peak systolic velocities showed a tendency to increase from the superior to the inferior aqueduct, irrespective of the background baseline region, with the range being from 3.30 cm/sec to 4.08 cm/sec. However, these differences were not statistically significant. In the case of the mean flow, the highest mean value was observed at the mid-portion of the ampulla (0.03 cm³/sec) in conjunction with the baseline ROI at the anterior midbrain. However, no other differences were observed among the mean flows according to the location of the cerebral aqueduct or the baseline ROI.

Conclusion

We obtained a set of reference data of the CSF peak velocity and mean flow through the cerebral aqueduct in young healthy volunteers. Although the peak systolic velocity and mean flow of the CSF differed somewhat according to the level of the cerebral aqueduct at which the measurement was made, this difference was not statistically significant.