应用计算流体力学方法显示颈动脉分叉血流模式的研究

目的 应用计算流体力学（CFD）方法结合MR血管成像（MRA）显示并分析在体颈动脉分叉的血流模式。方法 选取7例受检者，采用Siemens Trio型3．0TMR仪，行颈动脉MR增强血管成像（CEMRA）检查，扫描所得原始图像经计算机后处理，并采用CFD方法计算并显示该段血管的血流模式。结果 7例受检者该血管段的血流模式随心动周期的不同期相呈现周期性变化，在颈动脉分叉及颈内动脉和颈外动脉的近端外侧部均可见血液涡流与回流，其出现与否及形态随心动周期的不同期相而变化，随着血液流向颈内和颈外动脉远端，该涡流与回流逐渐消失。结论 应用CFD方法结合MRA能显示颈动脉分叉血液的血流模式随心动周期的变化情况。     

颈动脉分叉血液动力状态的计算流体力学初步研究

目的应用计算流体力学（CFD）方法结合血管影像显示在体颈动脉分叉的血流动力状态.方法选取1例志愿者,采用Siemens多层螺旋CT机行左侧颈动脉CT血管成像检查（CTA）,扫描所得原始图像经计算机后处理后,用CFD方法计算并显示血液动力学各项指标.结果（1）该血管血液流率均值范围为0.04～0.36 m/s,颈外和颈内动脉的内侧壁（均以分叉顶点为参照）可见一高血流速区,球部可见较大片低血流速区;颈动脉分叉及颈内、外动脉近端均可见血液涡流与回流.（2）血液绝对压、静态压和动态压的均值范围分别为100 266.70～101 615.90 Pa、-10 58.34～290.88 Pa、6.12～553.25 Pa;（3）管壁切应力均值范围为0.59～5.35 Pa,在颈动脉球部及颈内动脉后壁显示大范围的低切应力区,最低约为0.25 Pa,颈外动脉前外侧壁存在一小范围低切应力区.结论CFD方法结合血管影像能计算并显示在体颈动脉分叉的个体化血液动力学指标.     

布-加综合征血流动力学参数模拟与其病因相关性分析

目的建立特征性下腔静脉狭窄型布-加综合征三维（3D）模型,分析血流动力学参数变化,探讨与布-加综合征病因相关的血流动力学因素。方法选取下腔静脉重度狭窄型布-加综合征病例,通过对其磁共振成像（MRI）数据的3D重建,采用计算机流体力学（CFD）软件进行血流动力学数值模拟,并与正常人的下腔静脉模型参数进行比较,分析其主要血流动力学参数变化。结果建立的下腔静脉3D流体模型揭示了病变区域的血流模式。随狭窄的出现及狭窄程度的加深,血管内血流模式发生明显改变,狭窄区域旁侧出现涡流;狭窄处血流流速急升,最大值可达（1．39±0．257）m／s;狭窄处壁面切应力明显升高,最大值可达（7．77±0．124）Pa,且沿血流流动方向产生较大梯度。结论血流模式的改变会进一步影响血管内血液的局部流速以及血管壁上切应力等参数的分布,这些可能是影响下腔静脉狭窄以致进一步恶化形成栓塞的因素。     

3.0T MR多技术联合应用在头颈部动脉血管狭窄病变中的诊断价值

目的:分析3.0T MR 3D TOF MRA、高分辨CE MRA、双反转恢复颈动脉血管壁黑血成像在头颈部动脉血管狭窄病变检查中的技术特点,探讨其联合应用在头颈部动脉血管狭窄病变中的诊断价值。方法:研究所用技术经医院伦理委员会审查批准,向患者认真介绍后由患者签字同意。选择2009年5月~2009年6月在我院行头颈部TOF MRA检查患者95例,其中43例并行头颈部CE MRA检查,另52例并行颈动脉分叉部双反转恢复T2WI血管壁黑血成像。统计同时行TOF MRA和CE MRA患者组中两种技术完成的图像中脑血管、颈内动脉虹吸段、颈动脉分叉部、椎动脉起始部等多个部位动脉血管狭窄数量,对两种技术诊断结果行Kappa一致性检验。统计同时行TOF MRA和DIR颈动脉分叉部血管壁黑血成像患者组中狭窄血管数量,对两者行χ2检验判断有无统计学差异。结果:行头颈部TOF MRA和CE MRA患者组,各部位诊断结果Kappa值分别为:大脑前动脉A1段0.710,大脑中动脉M1段0.823,大脑后动脉P2段0.672,颈内动脉虹吸段0.729,颈动脉分叉部0.634,椎动脉起始部0.707。行头颈部TOF MRA和颈动脉分叉部DIR T2WI黑血血管壁成像患者组,两者诊断结果χ2=1.11,P0.05,无统计学差异。结论:3D TOF MRA和CE MRA技术均可明确诊断绝大部分头颈部动脉血管狭窄病变,但也有各自的不足,颈动脉血管壁黑血成像可明确诊断有无粥样硬化斑块形成,是对头颈部MRA成像的有效补充,三者的合理应用及结合可以从多方面来诊断头颈部血管狭窄性病变,弥补相互间的不足。     

破裂与非破裂颈动脉粥样硬化斑块周围血流动力学的MRI分析

目的 分析颈内动脉起始部粥样硬化斑块周围血流动力学改变,探讨可能导致纤维帽破裂的流体力学因素.方法 前瞻性纳入19例颈内动脉起始部粥样硬化病变患者,进行颈动脉MRI.观察斑块形态结构,并据此将斑块分为纤维帽完整组和纤维帽破裂组.利用颈动脉MR增强血管成像原始图像进行血流动力学分析,计算颈动脉分叉部血管管壁切应力(WSS)、静态压、血管狭窄率等数据,两组之间比较采用两独立样本的Mann-Whitney U检验和t检验.结果 19例颈内动脉起始部斑块中,纤维帽完整组8例、斑块纤维帽破裂11例.纤维帽完整组最大管壁切应力、平均管壁切应力、最小静态压及平均静态压对应的中位数(上下四分位数范围)分别为42.92(27.13～68.19)、32.04(21.21～55.68)、-1 717.36(-3 433.61～-721.10)、-1 341.64(-2 868.00～-612.86)Pa,纤维帽破裂组对应的数据分别为67.18(60.46～139.51)、55.76(40.41～124.57)、-3884.02(-18767.39～-2886.33)、-3065.92(-16064.18～-1 915.09)Pa,两组间差异有统计学意义(U值分别为18.00、18.00、17.00、18.00,P值均＜0.05).斑块纤维帽完整组和纤维帽破裂组颈内动脉狭窄率分别为(47.13±13.50)％、(62.91±11.96)％,两组之间比较差异有统计学意义(t=2.69,P=0.02).结论 破裂与非破裂颈动脉粥样硬化斑块间的血流动力学存在差异,可能会对斑块破裂造成影响.     

磁共振新技术在颈动脉狭窄诊断中的应用

目的研究增强磁共振血管成像（CE—MRA）技术的成像影响因素,评价MR扫描序列对颈动脉狭窄硬化斑块的应用价值,探讨颈动脉狭窄血流动力学变化与临床症状的联系。方法颈动脉狭窄34例,男22例,女12例。年龄36～78岁,平均56岁。病人首先经多普勒超声（DUS）检查,然后行MRA及CE-MRA。22例同时采用亮血（Bright—blood）、黑血（Black—blood）技术、3例行血流测量分析（Flow measurements）。10例于磁共振检查后1周内接受颈动脉狭窄内膜剥除术。扫描技术：（1）MRA及CE-MRA：MRA：二维时间飞跃法MRA（2D TOF MRA）;CE-MRA：快速梯度回波扫描技术,冠状位采集。最佳扫描延迟时间主要采用造影剂团注试验（test-bolus）法。3例采用时间分辨回波分享血管成像技术（TRATE）。（2）斑块检查序列：亮血与黑血技术及增强前后T1序列。（3）血流测量分析：横断位心电门控2D相位对比序列,Argus系统分析血流方向、流速。结果血管覆盖范围：34例CE-MRA,23例良好显示颈部血管起始段至入颅段。2D TOF法11例。动脉狭窄评估程度：10例手术患者中,CE-MRA正确诊断血管狭窄者9例,低估狭窄程度1例。2D TOF正确诊断血管狭窄程度6例,高估3例,低估1例。22例亮血、黑血技术结合CE—MRA清晰显示血管壁及动脉硬化斑块。颈动脉单独成像24例中,Test—bolus法团注造影剂最佳扫描延迟时间为峰值时间-1s,且监视层面定于主动脉弓者18例。4例眩晕患者,颈动脉狭窄侧后交通动脉（PCOA）显示2例;PCOA粗大1例。狭窄侧未显示PCOA,同侧大脑后动脉主干增粗1例。2例锁骨下动脉窃血综合征血流方向异常,1例无名静脉狭窄,同侧颈静脉血流方向异常。结论（1）CE—MRA能完整、全程显示颈部血管,准确诊断颈动脉、椎动脉狭窄。（2）Test-bolus法确定扫描延迟时间为峰值时间-1s,并将监视层面定于主动脉弓时,可保证造影剂在动脉内达到高峰浓度时采集K空间数据,获得颈动脉单独成像的最佳图像。（3）亮血、黑血技术结合CE-MRA有助于显示颈动脉狭窄硬化斑块。（4）分析、测量颈动脉狭窄的血流动力学变化能全面评价狭窄后血流改变与临床症状的联系。     

颈动脉Gadofosveset增强MR血管成像：稳态MR成像能否提高首次通过成像的准确性？与选择性DSA的比较

目的以DSA为参照标准,评价Gadofosveset增强MR血管成像对评估颈动脉狭窄的准确性,评价阅读首过、稳态及二者联合MR血管成像的价值。方法本研究经地方伦理委员会批准,并且所有参与者均签署知情同意书。84例（男56例,女28例;年龄61～76岁）超声下显示颈动脉狭窄的病人进行了MRA和DSA检查。3名阅片者评价首过、稳态及二者联合的MR血管成像表现,另有1名独立观察者评价DSA影像。主要评价颈动脉狭窄程度、斑块形态、溃疡形成、     

颈动脉粥样斑块3T MR高分辨成像和MRA诊断

目的:应用3.0T MR高分辨管壁成像和MR血管造影在体显示颈动脉粥样斑块,探讨MR对颈动脉斑块的诊断价值。方法:经彩超检查证实的症状性颈动脉狭窄37例,所有病例行管腔MRA和管壁高分辨MR检查,MR检查序列包括3DTOF、DIR T1WI、T2WI、PDWI和MRA。其中,17例检查前1周内行CT血管造影检查,9例患者检查后1周内行颈动脉内膜剥脱术。根据颈动脉内膜剥脱术手术部位,将获得的病理标本与MR图像逐层对照,研究斑块脂质成分、纤维成分和纤维帽、斑块钙化、出血和脂质坏死池等MR表现,探讨斑块变性的MR表现及其病理基础。结果:37个病例共发现52条颈动脉分叉处斑块,其中,管腔轻度狭窄24条(46.1%),中度狭窄19条(36.5%),重度狭窄7条(13.5%),闭塞2条(3.9%)。斑块钙化21条(40.4%)、无钙化斑块31条(59.6%);31条软斑块中纤维成分为主斑块8条(15.6%),有明显脂质核心斑块23条(44.2%);其中,伴斑块出血5条(10%)、脂质坏死核心3条(6%),纤维帽撕裂(溃疡或纤维帽撕裂)3条(6%)。相对于胸锁乳突肌,脂质坏死池在TOF、T1WI、PDWI、T2WI均呈显著高信号,钙化在各序列均呈低信号。斑块内出血的信号与出血的时间有关,新鲜出血各序列表现为点、结节或片状高信号,亚急性出血或者陈旧出血的信号与出血时间长短有关。结论:颈动脉MRA和管壁高分辨成像是评估颈动脉斑块风险性的有效手段,无创性MRA可以显示颈动脉斑块的狭窄程度;管壁高分辨成像可以直接显示斑块纤维帽、斑块内结构和成分,预测斑块脱落的风险性。     

颈动脉粥样硬化磁共振血管成像和彩色多普勒超声对比研究

目的 探讨彩色多普勒和磁共振血管成像(MRA)对颈动脉粥样硬化的诊断价值.方法 用CDFI及MRA 2种方法检查42例缺血性脑梗塞患者和40例对照组的颈动脉.超声检查颈动脉内径、测量颈动脉内膜-中层厚度(IMT)、最狭窄处管径,了解斑块情况,观察颈动脉狭窄程度.MRA检查颈动脉内径,测量病变动脉信号缺失情况,判断颈动脉狭窄程度.结果 超声检查显示缺血性脑梗塞患者颈动脉病变发生率明显高于对照组(P＜0.001).本组病例轻度、重度狭窄的MRA与超声诊断完全符合.1例血管闭塞超声低估为重度狭窄,1例超声判断为中度狭窄MRA高估为重度狭窄.MRA和超声结果具有极好的一致性.结论 超声与MRA在诊断颈动脉狭窄中具有互补作用,两者结合使用能提高评估狭窄程度的准确性.     

MR和CT血管造影在诊断颈动脉狭窄及内膜切除术后随访中的价值

目的 探讨磁共振血管造影（MRA）、CT血管造影（CTA）在诊断颈动脉狭窄及内膜切除术后随访中的价值。方法 11例22支颈动脉行MRA、CTA、CT仿真内窥镜（CTVE）、多普勒超声（DUS）检查。12支结果与DSA对照。3支颈动脉重度狭窄者行内膜切除术,MRA采用二维、三维时间飞越法。CTA经最大强度投影（MIP）及遮盖表现显示法（SSD）三维重建。应用导航功能行CTVE成像。结果 颈动脉轻度狭窄8支,中度狭窄3支,重度狭窄5支,闭塞1支,5支正常。12支颈动脉与DSA对照：CTA评估血管狭窄与DSA相符者11支,MRA与DSA相符者9支,DUS与DSA相符者7支。CTA、CTVE显示斑块、壁血栓6支,3支手术证实。术后MRA示狭窄解除,CTA示斑块消失。结论 MRA、DUS可用于颈动脉狭窄的筛选及术后随访。CTA评估血管狭窄程度与DSA、手术比较有较好的一致性,并能直接显示钙化斑块。     

Stress MR imaging for evaluation of popliteal artery entrapment

The popliteal artery entrapment (PAE) syndrome has been recognized as a cause of arterial occlusion in young people. It is the result of an anomaly of the relationship between the popliteal artery and the gastrocnemius muscle. Eight young healthy volunteers (16 legs) and six patients (10 legs) with suspected PAE underwent magnetic resonance (MR) imaging. Gradient-echo images were obtained in axial planes with the leg at rest and during active plantar flexion against resistance. Imaging at rest allowed identification of PAE signs in only one leg, which had an anomalous medial course of the popliteal artery. In the other cases, only the stress technique was able to show signal loss in the popliteal artery due to muscular compression (two legs) or the presence of accessory muscle slip around the vessel (two legs), as confirmed at surgery. MR imaging is therefore a useful technique for the diagnosis of PAE because of its capability of combining information obtainable with other modalities.     

MR imaging of muscle and tender points in fibromyalgia

Fibromyalgia is a syndrome manifested by chronic, diffuse muscu-loskeletal aching and soreness, palpable muscle tender points, and other symptoms. Standardized clinical diagnostic criteria have recently been developed. Skeletal muscle has been postulated as the end organ in this disease. Biochemical, histologic, electromyographic, and conventional radiographic studies have demonstrated no definitive abnormality. This study sought to establish whether magnetic resonance (MR) imaging could demonstrate any abnormality in these patients. Eighteen patients were entered in the study, 14 of whom were able to complete their examinations. T1 -weighted, T2-weighted, gradient-echo, and STIR (short-tau inversion-recovery) sequences were performed in all patients, with selected patients examined with T1weighted, gadopentetate dimeglu-mine-enhanced sequences. The trapezius and suboccipital regions were imaged in patients who, clinically, had active fibro-myalgia. No abnormalities could be detected. The authors conclude that the conventional MR imaging used in this study was unable to depict any primary skeletal muscle abnormality in fibromyalgia.     

Controversies in cervical spine imaging in trauma patients

No area of emergency radiology has generated as much discussion in recent years as the subject of cervical spine imaging for trauma patients. This review will be in three parts. The first will examine the indications for cervical imaging and will focus on those factors that make patients at high risk or low risk for cervical injury. The second part will discuss the merits of radiography and computed tomography as the main screening diagnostic examination. In addition to the roles of each modality in the evaluation process, such factors as efficacy of diagnosis, time (duration) of study, and cost will be discussed. Finally, the third part will explore the methods currently employed to clear the cervical spine in comatose patients.Presented at the Annual Meeting of the American Society of Emergency Radiology, Las Vegas, Nevada, 22–25 October, 2003     

Uterine contractions: Possible diagnostic pitfall at MR imaging

A total of 206 nongravid patients with various gynecologic problems underwent pelvic magnetic resonance (MR) examinations that included both sagittal T2-weighted and contrast agent–enhanced T1-weighted images. MR images were retrospectively reviewed to identify changes in endometrial configuration on serial images obtained during the same MR examination. In 20 MR examinations (all in women of reproductive age), endometrial distortion due to myometrial bulging was noted on T2-weighted or contrast-enhanced T1-weighted images. It was absent on other MR images obtained at different times. Myometrial bulging exhibited low signal intensity in 18 examinations. The finding resembled adenomyosis or leiomyoma on T2-weighted or contrast-enhanced T1-weighted images. These results evidence the presence of transient myometrial bulging and transient low-intensity myometrium in the nongravid uterus. This phenomenon is thought to represent uterine contraction. Clinicians should be aware of the potential presence of transient low-signal-intensity myometrial bulging that could present diagnostic problems in the normal uterus.     

Brodie Abscess: MR imaging appearance in 10 patients

The magnetic resonance (MR) imaging features of Brodie abscess have not yet been fully evaluated. Ten patients with Brodie abscess, eight of long bone and two of vertebra, were studied with MR imaging. Long bone abscess had a characteristic “target” appearance with four layers: (a) a center with low signal intensity on T1-weighted images and high signal intensity on T2-weighted and STIR (short-inversion-time inversion recovery) images, (b) an inner ring isointense to muscle on T1-weighted images and with high signal intensity on T2-weighted and STIR images, (c) an outer ring hypoin-tense on all images, and (d) a peripheral halo hypointense on T1-weighted images. In six of eight cases, a soft-tissue mass was found. The two vertebral abscesses had a less specific appearance, with low signal intensity on T1-weighted images and high signal intensity on T2-weighted and STIR images. Only the peripheral halo was clearly identified in both cases.     

Dynamic contrast-enhanced MR imaging assessment of vascularized free fibular grafts

Magnetic resonance (MR) imaging may be a noninvasive method for assessing perfusion of vascularized bone grafts placed for treatment of avascular necrosis. One proximal femur of seven beagles was devascularized, with insertion of a vascularized fibular graft. MR imaging at 1 week (seven dogs) and 6 weeks (five dogs) after surgery included pre- and postcontrast spin-echo sequences, unenhanced twodimensional time-of-flight (TOF) vascular imaging, and dynamic gradient-echo imaging during infusion of gadolinium. Relative signal intensity values of selected regions obtained from the dynamic gradientecho images were plotted as percent enhancement versus time. In the operated hip, MR imaging did not show enhancement in six of seven femoral heads and greater trochanters at 1 week after surgery, with similar results after 6 weeks. MR imaging of fibular grafts 6 weeks after surgery showed an initial rapid increase in enhancement and a subsequent slower increase in five of five dogs, although no enhancement was seen in six of seven dogs at 1 week. These findings contrasted with a rapid initial increase in enhancement followed by slow decline in non-operated hips. Two-dimensional TOP imaging did not show the vascular pedicle of the graft in any dog. Findings of radionuclide bone scanning performed 1 week after surgery were consistent with devascularization of the operated femur and fibular graft. However, tetracycline distribution and histologic findings confirmed the viability of five of five grafts within the devascularized femurs 6 weeks after surgery. Thus, dynamic contrast-enhanced MR imaging at 6 weeks after surgery is valuable for assessing vascular bone graft perfusion, while similar imaging at 1 week may suggest otherwise.     

Right-side aortic arch with aneurysm of aberrant left subclavian artery: MR imaging appearance.

Reports of aneurysms of the subclavian artery in both normal and anomalous aortic arches have been rare. The authors describe a patient with a right-side aortic arch and an aneurysm of the aberrant left subclavian artery, which, to the authors' knowledge, is a previously unreported association. At presentation, the aneurysm appeared as a calcified left superior mediastinal mass. Magnetic resonance imaging enabled preoperative diagnosis and guided surgical planning.     

Adrenal tissue characterization with 0.5-T MR imaging: Value of T2*-weighted images

The authors investigated the value of magnetic resonance (MR) imaging at 0.5 T for distinguishing adrenal adenomas from adrenal metastases. The series included 23 adrenal adenomas (18 nonhyperfunctioning, five hyperfunctioning) and 23 adrenal metastases from various organs. Adrenal tumor–liver signal intensity ratios on T1-, T2-, and T2*-weighted images were calculated for adrenal tissue characterization. Adrenal adenomas were more precisely distinguished from adrenal metastases on T2*-weighted images (21 of 23, 91%) than on T2-weighted images (15 of 23, 65%). T1-weighted images were not useful for this distinction. In conclusion, T2*-weighted images were better than routine T2-weighted images for distinguishing adrenal adenomas from adrenal metastases. It can be postulated that the total signal intensity of adrenal adenomas, which contain some fat components, decreased on T2*-weighted images because of an out-of-phase effect.     

MR angiography of congenital heart disease: Value of segmented two-dimensional inflow technique and maximum-intensity-projection display

Magnetic resonance (MR) angiography of the cardiovascular system was evaluated in 41 patients with congenital heart disease by using a two-dimensional (2D) inflow technique based on a magnetization-prepared gradient-echo pulse sequence with segmented k-space data acquisition and electrocardiographic gating at 0.5 T. Inversion and saturation prepulses were used to suppress stationary tissue and enhance intravascular signal. Presaturation slabs were applied where certain vascular structures had to be suppressed. Sequence parameters were optimized by evaluating signal intensity and contrast characteristics for various flip angles and inversion and saturation delay times. The heart and intrathoracic vasculature were encompassed with 40–50 overlapping sections. Both 2D angiograms and maximum-intensity-projection images were evaluated. Combining data sets acquired in the sagittal and transverse orientations provided the most satisfactory information about the pulmonary arteries. The highest signal-to-noise ratios were obtained with a flip angle of 65° and short prepulse delay times. Two-dimensional MR angiography can provide useful diagnostic information but requires a thorough understanding of in-plane and hemodynamically induced signal intensity changes.