磁共振血管MIP图像伪影形成机制、表现及解决办法探讨

目的:了解最大密度投影重建(MIP)图像伪影的形成机制,熟悉磁共振血管成像中MIP伪影的各种表现,探讨其解决办法。材料与方法:回顾性分析2003年12月~2004年6月磁共振血管检查患者共90例,其中头部3D TOF-MRA检查47例,颈部2D TOF-MRA检查20例,均同时进行了颈部3D CE-MRA检查;腹部3D CE-MRA检查25例。对各部位出现的MIP伪影进行分类、分析,探讨对不同表现形式的MIP伪影的解决办法。结果:①头部TOF-MRA的整体MIP图像上细小血管分支未显示共40处(后交通动脉32处,前交通动脉8处),通过对原始图像的观察或局部薄层重建使上述两处血管均得到显示。②20例颈部TOF-MRA检查中夸大血管狭窄程度共14处,均出现在血管狭窄程度在50%以上的血管,占病变总数的93.3%(14/15),CE-MRA对TOF-MRA夸大狭窄均做出了准确的矫正。颈部20例TOF-MRA中,颈外动脉锯齿状伪影36处,出现的几率为90%(36/40)。CE-MRA对此种伪影均做出了矫正。④MIP图像上在特定投影方向上血管分支不显示,通过改变投影方向或去掉高信号的背景组织此种伪影均得到解决。结论:磁共振血管检查MIP图像上出现伪影是常见现象,表现具有多样性;MIP图像伪影可造成错误的诊断。MIP图像的伪影可以通过不同的后处理方法或改变成像方法解决。在临床实际工作中不可单凭MIP图像做出最终诊断,需密切结合原始图像和不同处理方法的血管重建图像。     

TOF-MRA与3D CE-MRA对头部血管病变诊断价值的比较

目的探讨3D TOF-MRA(三维时间飞跃磁共振血管成像)、3D CE-MRA(三维增强磁共振血管成像)技术用于诊断头部血管病变的各自优势。方法对25例疑似头部血管病变患者,进行TOF-MRA和3D CE-MRA检查,分析其影像学特点。结果 25例中,有2例患者未能配合作TOF-MRA检查,而只做了3D CE-MRA检查,其余病例TOF-MRA检出率略高于3D CE-MRA。结论 TOF-MRA对头部血管病变的显示优于3D CE-MRA,是一种有效的诊断头颅血管病变的方法;而3D CE-MRA检查耗时短,对一些配合不好的患者有着独特优势。     

Care-bolus与Test-bolus在头颈部血管三维增强磁共振血管成像中的应用比较

目的 探讨Care-bolus与Test-bolus两种方法在头颈部血管三维增强磁共振血管成像(3D CE- MRA)的应用比较.方法 对60例怀疑头颈部血管病变患者,随机分两组分别采用Test-bolus与care- bolus两种方法行头部3D CEMRA检查,后处理技术包括最大强度投影(MIP)重建、多层面重建(MPR),评估其可靠性.结果 30例care-bolus法3D CE-MRA有2例因时间把握欠佳未能很好显示头颈部血管病变情况,而30例Test-bolus法3D CE-MRA均能很好显示头颈部血管病变情况.结论 三维增强磁共振血管成像中Test-bolus法优越于Care-bolus法.     

头颈部血管狭窄性疾病的128层螺旋CT数字减影血管成像结果分析

目的:评价128层螺旋CT数字减影血管成像在头颈部血管狭窄性疾病诊断中的应用价值。材料与方法:筛选2014年5月-2015年12月期间在本院接受128层螺旋CT数字减影血管成像检查(DSCTA)的106例临床怀疑为头颈部血管狭窄性疾病患者,对其影像学资料进行回顾性分析,由头颈部血管诊断经验丰富的3名主治以上医师共同评估血管减影图像质量、血管狭窄程度及斑块性质。结果:106例经128层螺旋CT数字减影血管成像检查患者中,有1例患者检查时制动不良,图像减影质量差,无法诊断;有3例患者未发现血管狭窄;余102例共计发现狭窄118处,有13例患者存在2处或以上血管狭窄:颈动脉(38支),椎-基底动脉(32支),大脑前动脉(15支),大脑中动脉(21支),大脑后动脉(12支)。结论:对106例疑似头颈部血管狭窄性疾病患者进行128层螺旋CT数字减影血管成像检查(DSCTA)分析结果表明,128层螺旋CTA成像清晰(可与常规DSA相媲美),操作简便,能够有效的去除骨质,在评价患者的头颈部血管狭窄方面具有重要价值。     

主动脉弓上磁共振血管成像在缺血性脑卒中临床应用的意义

目的:应用主动脉弓上对比剂增强磁共振血管成像(CE-MRA)评价缺血性脑卒中患者的血管病变分布和狭窄程度,并探讨其在脑卒中高危患者诊断、治疗及预防中的意义。方法:回顾性分析2012年1月至12月收治的454例缺血性脑卒中患者的头颅MRI、头颅MRA及主动脉弓上CE-MRA影像及病史资料。结果:454例患者中,除85例(18.72%)未见颅外血管异常,其余369例患者发现513处颅外血管狭窄或闭塞,大部分患者存在多处或多支血管病变,平均1.43处/例(482/338)。多发病变中颈动脉系统病变占52.28%(252/482),椎基底动脉系统病变占47.72%(230/482),其中重度狭窄18处,闭塞患者17处,轻度狭窄占绝大多数93.18%(478/513)。颅内MRA检查阴性的患者中有62.67%存在颅外血管病变,且与颅内、颅外皆无血管病变组在梗死面积及程度方面存在显著统计学差异(P<0.01)。结论:主动脉弓上CE-MRA在缺血性脑卒中患者中的狭窄和闭塞检出率较高,且即使患者颅内MRA显示为阴性,但在有症状及明确颅内缺血病灶的情,况下仍应行主动脉弓上CE-MRA筛查,以发现潜在的颅外段血管病变,并及时进行相关治疗或者预防干预措施。     

升主动脉夹层样搏动伪影的多层螺旋CT表现

目的探讨多层螺旋CT上升主动脉夹层样搏动伪影的发生率及其表现。方法93例患者作了胸部CT检查,男54例,女39例;年龄15~94岁,平均年龄(49.6±15.7)岁。观察CT图像,判断有无主动脉搏动伪影、发生部位、宽度、长度、边界是否清楚及伪影的连续性。结果93例患者中,72例出现升主动脉搏动伪影,检出率为77.4%,都累及升主动脉,搏动伪影最常发生在左前壁(70.8%)和右后壁(34.7%)。伪影的宽度为2.3~8.6mm,平均为(5.4±1.9)mm,长度为1~7层,平均为(2.8±1.3)层。64例(88.9%)伪影形成的“假腔”或“内膜片”在平扫CT上清晰可见其边界。伪影在上下层面出现间断16例(22.2%),伪影发生部位有变化共28例(38.9%),在增强CT图像上伪影消失5例(14.7%),增强CT发生部位改变15例(44.1%)。结论主动脉夹层样搏动伪影在多层螺旋CT上发生率较高,多发生于主动脉弓的左前方和右后方,长度及宽度范围局限、边界清楚及缺乏连续性,根据上述CT表现可对伪影做出鉴别诊断。     

颈部DIXON序列扫描出现的Swap伪影及解决方法

目的探讨颈部基于化学位移技术的水脂分离法(opposed-phase imaging,DIXON)序列扫描中出现Swap伪影的原因及解决方法。材料与方法回顾性分析947例DIXON序列扫描颈部的患者,对137例(冠状面4例,轴面133例)有Swap伪影的样本进行区域分类、信噪比测量,并将133例轴面样本分成45、45、43三组,分别使用增加average为2、关闭并行采集及改变相位编码的方法重新扫描,结果进行χ~2检验,P0.05有统计学意义。结果 (1)鼻窦、下颌骨、甲状软骨、皮表周围易出现伪影。(2)信噪比高的序列出现伪影的几率低于信噪比低的序列。(3)三个实验组去除Swap伪影的几率分别为93.3%(42/45)、91.1%(41/45)、53.5%(23/43)。第1、2组,P=0.693,差异无统计学意义;1、3组和2、3组,P0.01,差异有显著统计学意义。结论 Swap伪影的出现概率与磁场均匀性和图像的信噪比相关,磁场均匀性高,出现伪影的几率低;图像的信噪比高,出现伪影的几率低。实际工作中,增加信噪比的方法优于提高磁场均匀性的方法。     

三维增强MR血管造影在颅内动脉瘤诊断中的价值探讨

目的：评价三维增强MR血管造影（3D CE-MRA）在颅内动脉瘤诊断中的价值及准确性。方法：选择51例动脉瘤患者中同时行3D CE-MRA、三维时间飞越法MR血管造影（3D TOF-MRA）检查的27例动脉瘤患者，所有患者经DSA检查确诊。比较3D CE-MRA和3D TOF-MRA在显示动脉瘤及动脉瘤形态、瘤颈、载瘤动脉及瘤腔血栓能力上的优劣。结果：27例患者检出29个动脉瘤，3D CE-MRA和3D TOF-MRA的敏感性分别是100%（29/29），86%（25/29）。在动脉瘤形态，瘤颈形状及载瘤血管的显示上3D CE-MRA优于3D TOF-MRA（P<0.01），瘤腔血栓的显示上二者无差异（P>0.05）。结论：3D CE-MRA是一种快速有效、无创的诊断颅内动脉瘤的方法。     

同机CT图像伪影对骨断层显像衰减校正结果的影响

目的 评估同机CT图像中的伪影对SPECT/CT骨断层显像衰减校正(AC)图像结果产生的影响.方法 回顾分析78例患者骨断层显像资料,观察CT图像(及CT衰减图)中有无伪影,并对比非衰减校正(NC)图像,计算伪影区累及的局部骨骼放射性计数的变异系数(CV)及差值百分比(PD),进行统计学分析,以判断CT图像中伪影是否对骨断层AC图像结果造成影响.结果 38例同机CT图像产生伪影的病例,相应CT衰减图中均产生了同样形态的伪影信息,包括视野截断伪影、胸腹气体伪影、光子不足伪影等.受到伪影影响的骨断层AC图像中,除了局部骨骼的均匀性(CVAC 17.62%±4.13%,CVNC 11.19%±3.81%;t=2.13,P<0.05)和放射性计数分布(PDAC 16.98%±3.31%,PDNC 9.84%±1.62%;t=2.46,P<0.05)均受到影响.结论 同机CT图像中出现的伪影也会在CT衰减图中生成错误的校正信息,必要时应采用NC图像进行对比分析.     

MRI血管成像与增强血管成像对后循环缺血的诊断价值

目的 探讨MRI血管成像(magnetic resonance angiography,MRA)与增强MRI血管成像(contrast-enhanced MRA,CE-MRA)诊断后循环缺血疾病的价值。方法 回顾性分析50例后循环缺血患者MRA及CE-MRA检查结果,比较2种方法图像质量、狭窄及闭塞血管数目差异。结果 CE-MRA的图像质量良好率(76%)高于MRA检查(46%)(P<0.05);CE-MRA检查椎-基底动脉多发性血管病变的阳性率48%(24/50)高于MRA检查28%(14/50)(P<0.05);CE-MRA显示椎动脉、基底动脉和大脑动脉后狭窄率分别为78%、30%、28%,MRA则显示狭窄率分别为62%、20%、18%,二者比较差异均有统计学意义(P<0.05)。结论 MRA及CE-MRA均可为后循环缺血提供诊断依据,但CEMRA诊断效能优于常规MRA检查。     

Effectiveness of MRA on embolized intracranial aneurysms: a comparison of DSA,CE-MRA,and TOF-MRA

Purpose: The endovascular treatment of intracranial aneurysms was proven safe and effective compared to the alternative method of surgical clipping, despite the high recurrence rate. Follow-up of embolized intracranial aneurysms is mandatory for the early detection of recurrence and improved outcomes. DSA is used as the reference standard for this assessment. To determine the effectiveness of MRA in follow-up evaluations of intracranial aneurysms after embolization by comparing DSA, CE-MRA, and TOF-MRA.Materials and Methods: Sixty-eight consecutive patients undergoing DSA, TOF-MRA, and CE-MRA during an interval of <1 week were enrolled in this 6-month study. Images were evaluated for occlusion status, patency of the parent vessels, and artifacts. The modified Raymond-Roy occlusion classification and Aneurysm Embolization Grades were used to assess the occlusion status and initial DSA images for detection of recurrence in two filtered study phases with optimized selection criteria. Seventeen observers (phase I: 9, phase II: 8) independently interpreted the double-blinded images. Agreement was expressed with a Fleiss kappa value; p < 0.05 was considered significant.Results: This study included 68 patients with 77 aneurysms; 38 (49.35%) were treated with coil alone and 39 (50.65%) with stent-assisted coiling. In both phases, DSA was superior to TOF-MRA and CE-MRA using MRRC (Phase I: k = 0.567, p ≤ 0.001; k = 0.287, p ≤ 0.001; k = 0.117, p ≤ 0.001, respectively; Phase II: k = 0.503, p ≤ 0.001; k = 0.303, p ≤ 0.001; k = 0.115, p = 0.038, respectively). TOF-MRA was as effective as DSA (TOF: k = 0.335, p ≤ 0.001; DSA: k = 0.323, p ≤ 0.001) for recurrence detection.Conclusion: We suggest TOF-MRA as a first-line follow-up tool to detect aneurysm recurrence, and DSA to quantify the filling space to make a definite decision on re-embolization.     

Artifacts and pitfalls of high-resolution CT scans

Artifacts on CT images have been observed since the introduction of CT scanners. Some artifacts have been corrected with the improvement of technology and better understanding of the image formation and reconstruction algorithms. Some artifacts, however, are still observable in state-of-the-art high-resolution scans. Many investigations on CT artifacts have been reported. Some artifacts are obvious and some are similar to patterns commonly associated with pathological conditions. The present report summarizes some of the causes of artifacts and presents some artifacts that mimic pathology on clinical scans of the head and spine. It is the intention of this report to bring these artifacts and potential pitfalls to the attention of the radiologists so that misinterpretation can be avoided.     

Parallel imaging in MR angiography

The recently developed techniques of parallel imaging with phased array coils are rapidly becoming accepted for magnetic resonance angiography (MRA) applications. This article reviews the various current parallel imaging techniques and their application to MRA. The increased scan efficiency provided by parallel imaging allows increased temporal or spatial resolution, and reduction of artifacts in contrast-enhanced MRA (CE-MRA). Increased temporal resolution in CE-MRA can be used to reduce the need for bolus timing and to provide hemodynamic information helpful for diagnosis. In addition, increased spatial resolution (or volume coverage) can be acquired in a breathhold (eg, in renal CE-MRA), or in otherwise limited clinically acceptable scan durations. The increased scan efficiency provided by parallel imaging has been successfully applied to CE-MRA as well as other MRA techniques such as inflow and phase contrast imaging. The large signal-to-noise ratio available in many MRA techniques lends these acquisitions to increased scan efficiency through parallel imaging.     

磁共振血管成像评估颈动脉狭窄的研究进展

颈动脉狭窄是导致缺血性脑卒中的重要原因,早发现和早治疗可显著降低其致死率和致残率。磁共振血管成像以无创、无辐射、软组织分辨率高等特点而在颈动脉狭窄评估方面具有重要意义。作者就时间飞跃法磁共振血管成像(time of flight magnetic resonance angiography,TOF-MRA)、对比增强磁共振血管成像(contrast enhanced MRA,CE-MRA)、四维相位对比磁共振血管成像(four dimensional flow magnetic resonance angiography,4D-Flow-MRA)、零回波时间动脉自旋标记血管成像(zero echo time arterial spin labeling magnetic resonance angiography,zTE-ASL-MRA)、黑血成像技术(black blood,BB)和磁共振同时非增强血管成像和斑块内出血成像(simultaneous noncontrast angiography and intraplaque hemorrhage imaging,SNAP)等磁共振血管成像技术以及磁共振快速成像技术在评估颈动脉狭窄的应用及研究进展予以综述。     

有益于诊断的磁共振伪影探讨

目的:探讨有益于诊断的磁共振伪影。方法:以临床结果为标准,回顾性分析对诊断有益的磁共振伪影形成的原因及其对诊断的帮助作用。结果:13例具有化学位移伪影的病灶均证实含有脂肪成分;8例具有动脉搏动伪影的病变,7例为动脉瘤,1例为动静脉畸形;2例头部微量出血所导致的多处磁敏感伪影最终被证实为播散性脑炎所致的微量出血。结论:由于病变本身组成成分或病变性质所造成的伪影能够提供病变的重要信息,应重视它们对诊断的帮助作用。     

ZTE-MRA与TOF-MRA对脑动脉狭窄诊断价值对比研究

目的探讨零回波时间磁共振血管成像(zero echo time MR angiography,ZTE-MRA)及时间飞跃法磁共振血管成像(time of fight MR angiography,TOF-MRA)的图像质量以及对脑动脉狭窄诊断的价值。材料与方法纳入19例拟诊断为脑动脉狭窄的患者,同时进行ZTE-MRA及TOF-MRA检查,以数字减影血管造影(digital subtraction angiography,DSA)作为金标准,评估两种MRA成像技术诊断脑动脉狭窄的准确度、敏感度、特异度。结果ZTE-MRA和TOF-MRA的优良图像占比和信噪比(signal-to-noise ratio,SNR)平均值分别为84%、74%和14.2、19.4,差异均无统计学意义(P=0.583、0.175);诊断脑动脉狭窄ZTE-MRA的敏感度和特异度为100%和98%,TOF-MRA相应为85%和96%,ZTE-MRA的Kappa值为0.898优于TOF-MRA;ZTE-MRA诊断1~2级动脉狭窄和3~4级动脉狭窄准确度分别为57%和81%。TOF-MRA相应为46%和31%。诊断1~2级动脉狭窄差异无统计学意义(P=0.427),3~4级狭窄差异具有统计学意义(P=0.017)。结论ZTE-MRA和TOF-MRA的图像质量无明显差异,两者对于1~2级脑动脉狭窄诊断价值无差别,对于3~4级脑动脉狭窄ZTE-MRA较TOF-MRA更为准确。     

Angiographic artifacts that simulate arterial pathology in acute trauma

Films from 246 angiograms performed for acute trauma were reviewed for artifacts that mimic arterial pathology. The population studied was young (mean age 31.8 years), and preexisting arterial disease was uncommon. Thirty patients (12%) exhibited 35 artifactual abnormalities. Artifacts included stationary wave formation (15 patients), admixture in the leading edge of the contrast column (7 patients) or streaming from the inside aspect of an arterial curve (13 patients), Mach bands (8 patients), and abnormal densities caused by the mishandling of film (1 patient) or discharge of static electricity (1 patient). These artifacts have typical morphologic appearances and locations that allow differentiation from pathological processes that manifest as intraluminal filling defects or arterial wall irregularity.     

三维对比增强磁共振血管成像动脉期及双期检查诊断头颈动脉狭窄

目的 评价三维对比增强磁共振血管成像(3D CE-MRA)动脉期及3D CE-MRA双期检查对头颈部动脉狭窄的诊断价值。方法 对51例患者行3D CE-MRA双期检查,分析3D CE-MRA动脉期检查及3D CE-MRA双期检查表现,并与DSA相对照,分析两者对头颈部动脉狭窄的诊断效能。结果 以DSA为金标准,3D CE-MRA动脉期及3D CE-MRA双期诊断头颈部动脉狭窄敏感度、特异度、阳性预测值、阴性预测值、总符合率、阳性似然比、阴性似然比分别为90.81%(168/185)、92.96%(871/937)、71.79%(168/234)、98.09%(871/888)、92.60%(1039/1122)、12.90、0.10和90.81%(168/185)、95.62%(896/937)、80.38%(168/209)、98.14%(896/913)、94.83%(1064/1122)、20.73、0.10。3D CE-MRA动脉期、3D CE-MRA双期检查与DSA诊断结果均具有较高的一致性(Kappa=0.730、0.798)。3D CE-MRA动脉期与3D CE-MRA双期检查的特异度、阳性预测值、总符合率差异有统计学意义(P均<0.05)。结论 3D CE-MRA动脉期及3D CE-MRA双期检查与DSA诊断头颈部动脉狭窄具有较高的一致性;且3D CE-MRA双期较3D CE-MRA动脉期检查诊断准确率更高,尤其对诊断重度以上狭窄更具优势。     

Acoustic dispersing lenses cause artifactual discontinuities in B-mode ultrasonograms.

Artifacts as disruptions and duplications of the diaphragm, gallbladder wall, posterior wall of the left ventricle, etc., are often seen in B-mode ultrasound examinations. To identify their cause, in vitro experiments were carried out. These investigations showed that these artifacts are caused by acoustic dispersing lenses. In vivo they are due to rib cartilage and in vitro they can be reproduced by introducing an acryl lens into the sound field.