呼吸导航回波触发冠状动脉磁共振成像

目的:评价呼吸导航回波触发的冠状动脉MRA的效率以及心律和心率对图像质量的影响。材料和方法:17例健康志愿者,用导航回波触发3DSSFP序列进行冠状动脉成像,用自动窗位选择相位排列技术(PAWS)导航回波使膈肌触发采样窗宽为3mm,测量冠状动脉的长度,分析图像质量和心率、心律及呼吸的关系。结果:各冠状动脉主支的长度分别为:右冠状动脉11.6±2.0cm,左主干2.4±0.4cm,左前降支9.0±1.2cm,左回旋支5.0±0.8cm;PAWS的触发效率为37.7%,单次采样耗时6.6±1.0min;图像质量与呼吸方式无关,随着心率增快和心律不规则而降低。结论:PAWS导航回波触发的3DSSFP序列可以很好地控制冠状动脉MRA时的呼吸运动,但是需要提高成像效率以控制心脏运动。     

低场强磁共振胰胆管水成像在胆道梗阻性疾病诊断中的应用

目的：评价低场强磁共振胰胆管水成像技术（MRCP）在胆道梗阻性疾病诊断中的应用价值。方法：对36例患者及10例正常志愿者行MRCP检查，并与B超、CT进行比较，其中胆管结石13例，胆管癌12例，胰头癌5例，十二指肠乳头壶腹癌1例，胆系感染性狭窄5例。结果：MRCP能清晰显示胆管的梗阻部位，定位诊断准确率达100％，梗阻定性诊断率88.9％，优于B超和CT检查。结论：MRCP对胆道梗阻性病变的定位、定性诊断准确率明显提高，是此类病变可首选的检查方法。     

磁共振水成像在临床中的应用

磁共振水成像是近年来发展迅速的磁共振成像技术之一。其基本方法就是使用重T2加权技术使实质器官及流动血液呈低信号，而长T2静态液体呈高信号，独立成像。它包括磁共振胰胆管成像(MRCP)，磁共振泌尿系成像(MRU)，磁共振椎管成像(MRM)，磁共振内耳成像，磁共振涎腺管成像，磁共振泪道造影，磁共振脑室系统造影     

磁共振胆道成像对胆道梗阻的诊断价值

磁共振胆道成像对胆道梗阻的诊断价值张联合陆之安宋建荣钱铭辉为了探讨磁共振胆道成像（ＭＲＣ）对胆道梗阻的诊断价值，我们对４４例胆道梗阻患者进行ＭＲＣ检查，现报告如下。一、材料与方法４４例胆道梗阻中男１９例，女２５例，年龄２７～８２岁，平均６２．６岁。胆...     

超短回波时间序列在肺部磁共振成像中的研究进展

磁共振成像具有无辐射、软组织分辨力高等特点,但不适用于质子密度低、T2信号衰减迅速的组织器官,因此临床上其在肺部中的应用较为局限。随着超短回波时间（UTE）序列在肺部MRI检查中的应用,MRI对肺部疾病的评估得以拓宽。本文就UTE序列成像技术原理、分类以及其在肺部的临床应用进行综述。     

磁共振水成像技术在细粒棘球蚴病诊断中的应用

目的 探讨磁共振水成像(MRH)技术在细粒棘球蚴病诊断中的作用.方法 47例手术病理证实的细粒棘球蚴病例均行常规MRI检查和MRH检查.结果 47例细粒棘球蚴病共151个病灶中,常规磁共振检查检出细粒棘球蚴的灵敏度为61.59%,特异度93.33%, 磁共振水成像技术检出细粒棘球蚴的灵敏度为92.05%, 特异度86.67%.结论 MRH检出的病灶明显多于常规磁共振检出的病灶,二者结合使用在细粒棘球蚴病的诊断方面更具优势.     

零回波时间磁共振成像技术在上颌骨窦管显示中的初步应用

目的 探讨无对比增强的零回波时间磁共振成像（zero echo time magnetic resonance imaging, ZTE-MRI）技术在上颌骨窦管（canalis sinuosus, CS）显示中的可行性及临床应用价值。方法 选取行颌面部ZTE-MRI序列扫描的38例患者影像学资料,由3位医师使用多平面重组（multiplanar reformation, MPR）在GE后处理工作站上独立观察评估上颌骨CS。组内相关系数（intraclass correlation coefficient, ICC）用于评估测量的可重复性。比较不同位置（左、右侧）、性别、年龄组间上颌骨CS的直径差异有无统计学意义。结果 38例患者ZTE图像中双侧18例（47.37%）,左侧12例（31.58%）,右侧8例（21.05%）。不同位置（左、右侧）、性别、年龄组间上颌骨CS的直径均差异无统计学意义（P>0.05）。结论 ZTE-MRI技术是一种三维高分辨率成像方式,无辐射,软组织分辨率高,显示上颌骨CS是可行的,避免临床上颌前区手术对上颌骨CS内的血管神经束造成损伤。     

低场梯度回波成像在脊柱病变中的应用

目的：评价梯度回波成像在国产低场要上对脊柱病变的诊断价值。材料和方法：对120例行MRI检查的脊柱病变患午进行回顾性分析。结果：在国产低场机上,椎体病变梯度回波成像明显优于自旋回波成像;间肋病变略优于自旋回波成像;脊髓病变梯度回波成像则明显不如自旋回波成像。结论：椎体病变,梯度顺波成像时间短、图像清晰,病变显示优良,应做为常规扫描序列。     

Reducing motion artefacts in diffusion-weighted MRI of the brain: efficacy of navigator echo correction and pulse triggering

Diffusion-weighted MRI (DWI) is extremely sensitive to motion of the object being examined. Pulse triggering and navigator echo correction are methods for reducing motion artefacts which can be combined with conventional DWI sequences. Implementation of these methods in imaging sequences with a readout of one, three, or five echoes is presented and imaging results compared in a study of five healthy volunteers. As an objective measure for motion-induced image artefacts, the “artefacticity” of an image is defined. Pulse triggering and navigator echo correction significantly improve image quality and provide a technique for high-quality DWI on standard imagers without improved gradient hardware. Received: 31 January 1999/Accepted: 12 July 1999     

3D motion adapted gating (3D MAG): a new navigator technique for accelerated acquisition of free breathing navigator gated 3D coronary MR-angiography

This study aimed to evaluate the influence of a new navigator technique (3D MAG) on navigator efficiency, total acquisition time, image quality and diagnostic accuracy. Fifty-six patients with suspected coronary artery disease underwent free breathing navigator gated coronary MRA (Intera, Philips Medical Systems, 1.5 T, spatial resolution 0.9×0.9×3 mm³) with and without 3D MAG. Evaluation of both sequences included: 1) navigator scan efficiency, 2) total acquisition time, 3) assessment of image quality and 4) detection of stenoses >50%. Average navigator efficiencies of the LCA and RCA were 43±12% and 42±12% with and 36±16% and 35±16% without 3D MAG (P<0.01). Scan time was reduced from 12 min 7 s without to 8 min 55 s with 3D MAG for the LCA and from 12 min 19 s to 9 min 7 s with 3D MAG for the RCA (P<0.01). The average scores of image quality of the coronary MRAs with and without 3D MAG were 3.5±0.79 and 3.46±0.84 (P>0.05). There was no significant difference in the sensitivity and specificity in the detection of coronary artery stenoses between coronary MRAs with and without 3D MAG (P>0.05). 3D MAG provides accelerated acquisition of navigator gated coronary MRA by about 19% while maintaining image quality and diagnostic accuracy.     

磁共振成像在胰胆管疾病中的应用

目的：介绍用磁共振检查胰胆管疾病的四种扫描序列,并评价它们的作用和局限性。材料和方法：对５２例疑有胰胆管疾病的患者行两种Ｔ２加权和两种ＭＲＣＰ序列检查;横断位ＨＡＳＴＥ序列、冠状位ＴｒｕｅＦＩＳＰ序列、ＴｒｕｅＳＥ ＭＲＣＰ序列和ＨＡＳＴＥ ＭＲＣＰ序列。４２例经ＥＲＣＰ或手术病理证实,其检查结果与ＥＲＣＰ或手术对照。结果：所有图像的质量均达到了能够诊断的要求。四种扫描序列均显示了所有扩张的胰胆管,胆管结石定性的准确性分别为８７．５％、９１．７％、８７．５％和９５．８％,对肿瘤的定性准确性分别为８２．４％、７６．５％、６４．７％和７０．６％,结合所有序列对结石定性的准确性为１００％,对肿瘤的定性准确性为８８．２％。结论：上述四种扫描序列对显示胆胰管疾病各有其优点,结合应用可提高胰胆管疾病检出率和作出更准确的定性     

呼吸导航回波触发心脏MRI黑血对比序列的应用

目的 评价呼吸导航同波触发心脏黑血对比快速sE(FSE)序列的应用优势.方法 将呼吸导航回波触发技术与黑血对比FSE序列(NAV-FSE)结合,11名志愿者和5例患者在自由呼吸状态下完成扫描,同时使用相同参数的屏气黑血对比序列(BH-FSE)作为对比,使用t检验比较两者在采样效率、图像锐利度的差别.结果 NAV-FSE能对所有受检者完成全部检查,1名志愿者和3例患者不能屏气配合完成BH-FSE检查;当回波链长度(ETL)分别为24、16、8时,NAV-FSE的成像效率分别为(42.95±11.50)%、(56.14±11.40)%、(55.25±14.70)%.图像锐利度在ETL=16和24时,NAV-FSE(分别为0.43±0.02、0.36±0.02)和BH.FSE(分别为0.36±0.03、0.35±0.02)的差异有统计学意义(t值分别为4.26、5.53,P值均<0.05).NAV.FSE还可以设置更短的ETL而尤需考虑屏气的限制.结论 NAV-FSE可以回避心脏MR检查的屏气限制,并可以通过改变参数达到提高图像质量的目的 .     

Applicator visualization using ultrashort echo time MRI for high-dose-rate endorectal brachytherapy

PurposeThe individual channels in an endorectal applicator for high-dose-rate endorectal brachytherapy are not visible on standard MRI sequences. The aim of this study was to test whether an ultrashort echo time (UTE) MRI sequence could be used to visualize the individual channels to enable MR-only treatment planning for rectal cancer.Methods and MaterialsWe used a radial three-dimensional (3D) UTE pulse sequence and acquired images of phantoms and two patients with rectal cancer. We rigidly registered a UTE image and CT scan of an applicator phantom, based on the outline of the applicator. One observer compared channel positions on the UTE image and CT scan in five slices spaced 25 mm apart. To quantify geometric distortions, we scanned a commercial 3D geometric quality assurance phantom and calculated the difference between detected marker positions on the UTE image and corresponding marker positions on two 3D T₁-weighted images with opposing readout directions.ResultsOn the UTE images, there is sufficient contrast to discern the individual channels. The difference in channel positions on the UTE image compared with the CT was on average −0.1 ± 0.1 mm (left-right) and 0.1 ± 0.3 mm (anteroposterior). After rigid registration to the 3D T₁-weighted sequences, the residual 95th percentile of the geometric distortion inside a 550-mm-diameter sphere was 1.0 mm (left-right), 0.9 mm (anteroposterior), and 0.9 mm (craniocaudal).ConclusionsWith a UTE sequence, the endorectal applicator and individual channels can be adequately visualized in both phantom and patients. The geometrical fidelity is within an acceptable range.