螺旋CT三期扫描对肝纤维化诊断价值研究

目的探讨螺旋CT三期扫描对肝纤维化的诊断价值。方法对66例经肝穿刺活检病理证实的慢性乙型肝炎肝纤维化患者组和42例正常对照组进行螺旋CT三期增强扫描。根据纤维化程度分期进行影像资料和相关指标的统计分析。结果肝左叶增大,肝表面形态及肝实质密度的改变,脾脏增大,门静脉增宽和侧枝循环的建立等影像学改变,随着肝纤维化严重程度的加重而有统计学差异。本研究显示57例肝纤维化患者螺旋CT三期扫描诊断肝纤维化52例,敏感性91.2%,特异性77.8%。各期肝纤维化分期准确28例,准确率49.1%;准确判断轻度纤维化(S1、S2)或重度纤维化(S3、S4)44例,准确率77.2%,诊断早期肝硬化16例,准确率84.2%。结论螺旋CT三期扫描能判断肝纤维化的程度,而且是动态观察肝纤维化的病程演进和临床随访的有效手段。     

门静脉高压CT征象与肝纤维化、肝硬化病理分期关系的探讨

目的 探讨肝纤维化、肝硬化门静脉高压的CT征象与病理分期的关系.方法 对经肝穿刺病理活检确诊的肝纤维化S1期12例、S2期14例、S3期9例、S4期13例、典型肝硬化16例以及20例对照组行16层螺旋CT上腹部3期增强容积扫描,于门静脉期最大密度投影(MIP)图像上分别测量门静脉左支、门静脉右支、门静脉主干(MPV)、脾静脉(SV)和肠系膜上静脉(SMV)的管径,并观察各组门静脉侧支循环开放情况及有无腹水和脾脏肿大,将上述指标与病理分期作对照研究.门静脉系统各血管管径的比较采用单因素方差分析,组间两两比较用SNK法;多组腹水及侧支循环发生率的比较采用R×C表x2检验,组间行x2分割计算;运用Logistic回归分析探讨门静脉系统中对肝纤维化病理分期影响最大的血管.结果 对照组门静脉左支、门静脉右支、MPV、SV和SMV的管径分别为(0.98 ±0.11)、(1.00±0.12)、(1.33±0.11)、(0.75±0.10)和(1.07±0.12)cm,脾脏体积为(128.55±30.56)cm<'3>,无侧支循环开放和腹水.S1、S2、S3期组、S4期组或早期肝硬化组、典型肝硬化组SV管径逐渐增大,分别为(0.86±0.12)、(0.96±0.11)、(1.07±0.08)、(1.09±0.10)和(1.18±0.19)cm,各组与对照组间比较,差异均有统计学意义(P<0.05),重度肝纤维化(S3期组和S4期组)、典型肝硬化以及轻度肝纤维化(S1期组和S2期组)间差异均有统计学意义(P<0.05).Logistic回归分析显示,在门静脉各血管测量指标中,SV的标准化回归系数最大(2.719),且差异有统计学意义(P<0.01).典型肝硬化的侧支循环开放及腹水发生率明显高于正常肝脏和肝纤维化各期,S4期的侧支循环出现率明显高于对照组、S1期组及S2期组.结论 当慢性肝病发展至重度肝纤维化或早期肝硬化时,CT检查有助于早期诊断.     

声触诊组织量化技术对肝纤维化的诊断价值

目的 评估声触诊组织量化（VTQ）技术对肝纤维化的诊断价值.方法 选取2011年6月~2012年12月来我院就诊的慢性肝炎患者（慢性肝炎组）60例、肝硬化患者（肝硬化组）45例及健康体检者（健康对照组）25例,利用VTQ技术测定右肝感兴趣区肝脏横向剪切波速度（SWV）;慢性肝炎患者同期行肝穿刺活检病理检查,分析SWV与肝纤维化程度的相关性,采用受试者工作特征（ROC）曲线,评价VTQ技术诊断肝纤维化的准确性.结果 健康对照组、慢性肝炎组及肝硬化组肝脏SWV分别为（2.0±0.2）m/s、（2.3±0.4）m/s 和（3.1±0.5）m/s,3者间具有显著性差异（P＜0.05）.随着肝纤维化程度加深,肝脏SWV增高,SWV值与肝纤维化分期呈正相关,相关系数为0.73（P〈0.05）;诊断≥S2及≥S3的ROC曲线下面积为0.94、0.92,诊断的临界值为1.36m/s、1.69m/s,灵敏性、特异性分别为0.88、0.88,0.92、0.76.结论 VTQ技术对肝纤维化具有较高的诊断价值.     

多层螺旋CT肝脏灌注成像评价慢性肝纤维化、肝硬化的价值

目的 探讨MSCT灌注参数评价慢性肝纤维化、肝硬化的价值.方法 对经肝穿刺病理活检确诊的轻度肝纤维化(肝纤维化分期为S1、S2期)31例,重度肝纤维化(肝纤维化分期为S3、S4期)和(或)早期肝硬化34例,具有典型临床症状和影像表现的晚期肝硬化42例以及对照组30例行16层螺旋CT肝脏灌注扫描,取得不同病变阶段肝实质的灌注参数,包括肝动脉灌注量(HAP)、门静脉灌注量(PVP)、全肝总灌注量(TLP)、肝动脉灌注指数(HPI)及达峰时间(TTP)5个指标,并与病理分期作对照研究.各组肝脏不同CT灌注参数值的比较采用方差分析;各灌注参数值与肝纤维化严重程度的相关性采用秩相关分析;采用多因素分析(Logistic回归)探讨肝脏灌注参数值中对肝纤维化病理分期影响最大的指标.结果 对照组、S1、S2期组、S3、S4期组及肝硬化组的HAP值分别为(28.9±8.6)、(24.6±2.4)、(29.2±2.3)和(38.9±7.0)ml·100 ml-1·min-1,表现为先下降后增高,各组间差异有统计学意义(F =40.26,P＜0.01);上述各组PVP分别为(111.3±18.1)、(92.9±5.3)、(73.0±9.0)和(54.1 ±13.8)ml·100 ml-1·min-1,TLP分别为(140.2 ±25.9)、(117.1±4.5)、(102.3±8.7)和(93.0±ll.8)ml.100 ml-1·min-1,差异均有统计学意义(F值分别为136.79、67.40,P值均＜0.01);各组的HPI分别为(20.4±2.6)％、(21.0±2.1)％、(28.5±3.1)％和(42.6±1 1.1)％,TTP分别为(123.7±22.2)、(137.1 ±27.1)、(145.0±28.6)和(166.5 ±25.1)s,差异亦均有统计学意义(F值分别为93.05、17.37,P值均＜0.01).PVP、TLP与肝纤维化严重程度呈显著负相关,r值分别为-0.920和-0.846,P值均＜0.01;HAP、HPI、TTP则与肝纤维化程度呈正相关关系,r值分别为0.611、0.882和0.545,P值均＜0.01.在肝脏CT灌注扫描的参数值中,PVP的标准化回归系数最大(-8.798).ROC曲线判断得到的最佳临界点PVP =84.76 ml· 100 ml-1· min1作为重度肝纤维化S3、S4期和(或)早期肝硬化的诊断阈值,其敏感度和特异度分别为0.890、0.950,准确度达0.931.结论MSCT灌注参数能反映肝纤维化、肝硬化的血流动力学改变;CT灌注成像有助于鉴别重度肝纤维化和(或)早期肝硬化及晚期肝硬化.     

门脉右支前间隙增宽对早期肝硬化诊断价值的多排螺旋CT研究

目的 评价门脉右支前间隙增宽对于早期肝硬化的诊断价值.方法 回顾性分析37例经病理穿刺活检确诊的早期肝硬化患者及42例乙型肝炎患者的肝脏多排螺旋CT片,测量门脉右支前间隙及门脉右支的宽度;同时选择40例无肝脏疾患患者作为正常对照组,并测量门脉右支前间隙及门脉右支的宽度;对各组进行统计学分析.结果 正常组肝脏门脉右支前间隙及门脉右支宽度分别为(5.5±2.4)mm和(11.84±1.91)mm,早期肝硬化组门脉右支前间隙及门脉右支的宽度分别为(13.6±5.8)mm和(12.36±1.97)mm,而乙型肝炎组门脉右支前间隙及门脉右支的宽度分别为(5.7±3.1)mm和(12.13±1.89)mm.经统计学分析早期肝硬化患者门脉右支前间隙宽度同乙型肝炎组及正常组门脉右支前间隙宽度的差别具有统计学意义,而门脉右支宽度的差别没有显著的统计学意义.同时,乙型肝炎组同正常对照组间门脉右支前间隙宽度的差别不具有统计学意义,2组间门脉右支宽度的差别也不具有统计学意义.结论多排螺旋CT测量门脉右支前间隙增宽,对于早期肝硬化的诊断具有较好的临床价值.     

慢肝纤维化、肝硬化CT肝脏容积变化与病理学分期的相关性

目的 探讨慢肝纤维化、肝硬化肝脏体积变化规律及其与病理学分期的相关性.方法 对经肝穿病理活检确诊的肝纤维化S1期8例、S2期11例、S3期7例、S4期/早期肝硬化10例、具有典型临床症状和影像学表现的中晚期肝硬化15例以及16例正常组行16层螺旋CT肝脏容积扫描,采用仪器自身携带的Volume功能软件,分别测量肝脏左外叶、方叶、右叶以及尾状叶的体积,计算全肝的体积以及各个肝叶占全肝的百分比,并与病理学分期作对照研究和统计学分析.结果 正常肝脏的大小为(1097.12±103.53)cm3,左外叶、方叶、右叶、尾状叶的大小及其占全肝的百分比依次分别为(166.53±22.05)cm3、(190.45±18.54)cm3、(714.96±43.22)cm3、(25.18±4.02)cm3;(15.13±1.07)%、(17.34±0.58)%、(65.25±1.48)%、(2.29±0.23)%.从S1期至肝硬化,肝左外叶体积逐渐增大.典型肝硬化左外叶容积及所占百分比明显增大,与其他各组比较均有显著性差异.重度肝纤维化S3、4期/早期肝硬化左外叶容积和/或其百分比与正常组比较有统计学差异(P＜0.05).方叶体积在S1～S3期轻度增大,S4期/早期肝硬化、典型肝硬化则明显变小且组间比较均有统计学差异.除了典型肝硬化组右叶体积(502.67±112.44)cm3及其百分比(55.20±8.72)%明显变小,与其他各组比较具有统计学差异,S2期肝右叶体积显著大于正常组(P＜0.01)外,余各组间右叶体积及所占百分比均无显著差异.肝硬化组尾状叶容积和/或其所占百分比与其他各组之间均存在着显著的统计学差异,余各组间均无差异.总肝体积先增大后缩小,典型肝硬化与其他各组比较均有统计学差异(P＜0.01),肝纤维化S1～4各期之间差异均无显著意义;S4期/早期肝硬化组总肝体积较S2、3期变小,但仍大于S1期和正常对照组.结论 肝脏肝叶容积大小与肝纤维化严重程度密切相关.     

双层探测器光谱CT诊断肝纤维化分期的最佳单能量研究北大核心CSCD

目的:探讨双层探测器光谱CT最佳单能量成像对肝纤维化的诊断价值。方法:采用CCl_(4)腹腔注射法诱导建立兔肝纤维化模型,分为实验组(n=26)和正常对照组(n=4)。在造模后采用双层探测器能谱CT进行双期增强扫描,测量混合能量(CPI)及单能量(VMI_(40~70 keV))肝脏标准化强化值(ΔCT)。根据METAVIR系统进行肝纤维化分期。采用Spearman相关性分析明确动脉期、门脉期的肝脏ΔCT_(CPI)及ΔCT_(VMI(40~70))与纤维化分期相关性;采用ROC曲线评价对纤维化分期的诊断效能。结果:动脉期ΔCT值与纤维化分期均无相关性,静脉期ΔCT_(CPI)及ΔCT_(VMI(40~70))值与纤维化分期呈不同程度正相关。ΔCT_(VMI 40)与纤维化分期的相关性最高(r=0.595,P=0.001),ΔCT_(CPI)与纤维化分期相关性最低(r=0.453,P=0.012)。ΔCT_(VMI 40)对≥F1、≥F2、≥F3和F4期纤维化的ROC曲线下面积分别为0.865、0.790、0.831和0.740。结论:双层探测器光谱CT最佳单能量成像所测定的肝脏强化值与纤维化相关性高于混合能量,提示其可以准确诊断各期肝纤维化。     

磁共振弥散加权成像在乙型肝炎肝纤维化程度评估中的价值

目的：探讨磁共振弥散加权成像（DWI）在乙型肝炎肝纤维化程度评估中的价值。方法62例乙型肝炎肝纤维化患者根据肝脏穿刺及组织病理学检查分为S1期（n=15例）、S2期（n=16例）、S3期（n=16例）、S4期（n=15例）,同期选择23例未发生肝纤维化的乙肝患者作为对照组,选择24例门诊健康体检者作为正常组。所有研究对象均接受磁共振平扫及DWI检查,比较各组不同b值时ADC值,分析ADC值与乙型肝炎肝纤维化分期的相关性。结果 b值为100s/mm2、200s/mm2、400s/mm2时各组ADC值比较无显著性差异（P>0.05）,b值为600s/mm2、800s/mm2时,肝纤维化组S3及S4期ADC值明显低于S0、S1及S2期（P<0.05）;b值为100s/mm2、200s/mm2、400s/mm2时,不同分期ADC值间比较无显著性差异（P>0.05）,b值为600s/mm2、800s/mm2时,ADC值与肝纤维化分期有负相关性（P<0.05）,b值为800s/mm2时,相关性最明显。结论 DWI在乙型肝炎肝纤维化程度评估中具有较高的临床价值,尤其当b值为800s/mm2时,各肝纤维化分期的ADC值存在较大的差异性,值得临床推广应用。     

大鼠肝纤维化和肝硬化MR-PWI参数与CD34和a-SMA的相关性

目的：探讨大鼠肝纤维化、肝硬化模型磁共振灌注成像（MR-PWI）参数的意义及其与 CD34、a-SMA 的相关性。方法：清洁级 SD 大鼠随机分为实验组（n＝84）和对照组（n＝16）。实验组采用硫代乙酰胺（TAA）腹腔定点注射,每次200 mg／kg,3次／周,对照组同期腹腔注射同剂量的生理盐水。建模第6～30周后实验租和对照组分批次行肝脏磁共振常规扫描及灌注成像。病理上将鼠肝损伤分为肝纤维化0期、Ⅰ～Ⅱ期和Ⅲ～Ⅳ期、肝硬化结节期,并与灌注参数TTP、WIR、WOR 和免疫组化指标 CD34、a-SMA 表达作对照。结果：共有69只大鼠（实验组57只,对照组14只）成功获取 MR-PWI 参数,成功率69％（69／100）。实验组门静脉和肝实质的 TTP 随着肝纤维化及肝硬化进展而延长,而门静脉WIR、WOR 在肝纤维化Ⅰ～Ⅱ期和Ⅲ～Ⅳ期下降不明显,肝硬化结节期则明显下降;肝实质 WIR、WOR 则随着肝纤维化、肝硬化进展而逐渐下降,各期之间差异有统计学差异（P ＜0．05）;各灌注参数与肝纤维化病理分期之间有较好相关性（P ＜0．05）。CD34和 a-SMA 表达在肝纤维化Ⅰ～Ⅱ期不明显,肝纤维化Ⅲ～Ⅳ期和肝硬化结节期则明显表达,与对照组比较,实验组肝纤维化Ⅲ～Ⅳ期和肝硬化期 CD34、SMA 表达均显著增加（P ＜0．01）。门静脉及肝实质灌注参数 TTP、WIR、WOR 和 CD34、a-SMA 表达有相关性（P ＜0．05）。结论：门静脉和肝实质 TTP、WIR、WOR 与大鼠肝纤维化、肝硬化不同分期之间有相关性,与 CD34、a-SMA 表达有相关性。     

肝纤维化的影像学诊断

肝纤维化是各种慢性肝病发展中由于肝内纤维生成与降解失衡,致使过多的胶原在肝内沉积,常伴有炎症,并可发展为肝硬化。肝纤维化的诊断方法主要包括病理学诊断、血清学诊断和影像学诊断3种。肝活检组织病理学检查是诊断肝纤维化和肝硬化的金标准。目前,国际慢性肝炎新的分级、分期标准建议将肝脏纤维增生作为病情分期的依据,分期方法为,0期（SO）：无纤维化;1期（S1）：汇管区纤维化扩大,     

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.