How should we estimate carotid stenosis using magnetic resonance angiography?

Our purpose was to assess the reproducibility of and differences between the most commonly used methods for assessing carotid artery stenosis using magnetic resonance angiography (MRA). We studied 55 patients who underwent axial three-dimensional time-of-flight MRA (1.5 T). Quantitative caliper measurements were performed from maximum intensity projection (MIP) and multiple planar reconstruction (MPR) images, according to the criteria of the North American Symptomatic Carotid Endarterectomy Trial (NASCET) and European Carotid Surgery Trial (ECST). The measurements were compared to each other and to visual interpretation, using conventional angiography as the reference. The measured percentage stenoses were higher on MRA than on digital subtraction angiography (DSA) using both NASCET (mean difference 1.9–3.0%) and ECST (6.3–6.7%) criteria. The kappa coefficients for the agreement between DSA and MRA were higher using the NAS-CET (0.61–0.76) than the ECST criteria (0.52–0.65). No statistically significant differences were found between measurements from MIP and MPR images. The ECST measurement criteria gave significantly higher percentage stenoses than the NASCET criteria (P<0.001), this difference being more prominent on MRA (mean difference in diameter stenosis percentage 14.3–16.4%) than on DSA (7.6–11.2%) and most important with mild stenoses. The difference between visual interpretation and quantitative measurements on MRA was significant (P=0.01–0.001). There were no statistically significant interobserver differences in the MRA film readings, either in visually estimated degrees of stenosis or stenosis measurements. Thus, the different criteria of the two multicentre trials led to significantly different results, especially in the assessment of mild stenosis, and these differences are more important with MRA than with aging modalities or the reconstruction programs seem less important.     

Correlation of cine MR velocity measurements in the internal carotid artery with collateral flow in the circle of willis: Preliminary study

The velocity-phase relationship intrinsic to phase-contrast magnetic resonance (MR) angiography permits the quantitative and qualitative assessment of blood flow. The ability to measure velocity and vessel cross-sectional area allows noninvasive assessment of volume flow rate (VFR) in the internal carotid artery (ICA). Phase-contrast techniques also demonstrate flow direction. Using two-dimensional cine phase-contrast angiography, the authors evaluated VFR in the ICA and collateral flow about the circle of Willis in 15 patients with ischemic neurologic symptoms. The VFR in each carotid artery was correlated with the degree of stenosis and presence or absence of abnormal circle of Willis collateral flow. There was a correlation between a decrease in VFR and abnormal circle of Willis collateral flow. In addition, a correlation between severe stenosis and a decrease in VFR was found. In patients with ischemic neurologic symptoms without severe stenosis (<70% diameter stenosis), no decrease in VFR was seen. It is hoped that flow quantification and directional flow imaging with phase-contrast angiography will help further characterize carotid artery occlusive disease by enabling assessment of VFR changes associated with ischemic neurologic symptoms. This study also supports the hypothesis that two mechanisms-hemodynamic and embolic-play a role in ischemic neurologic symptoms.     

Selection of patients for carotid endarterectomy: the role of ultrasound

Stroke is the third leading cause of death in the western world and the major cause of disability among the middle aged and elderly populations. Carotid artery stenosis is the single most important risk factor for stroke. The North American Symptomatic Carotid Endarterectomy Trial and the European Carotid Surgery Trial have demonstrated that the risk of stroke is reduced by surgery in patients with high grade stenosis. Carotid plaque morphology also plays an important role; plaques which are ulcerated and echolucent are associated with a higher risk of stroke. Arteriography has long been regarded as the gold standard diagnostic tool for evaluation of carotid artery disease, but it is an invasive and costly technique which carries the risk of potentially serious complications. Doppler ultrasound can provide functional and anatomical information on vessel stenosis and plaque morphology at sub-millimetric resolutions and is an inexpensive and noninvasive tool. Color and spectral Doppler ultrasound are now recognized as the best screening tests for carotid artery stenosis. The evidence for its use as the sole diagnostic imaging modality prior to carotid endarterectomy is examined. The recent availability of ultrasound contrast agents helps to distinguish between pseudo- and true occlusions, improves ultrasound images and should help to reduce operator variability.     

高频超声评价颈动脉管壁形态对冠心病的预测价值

目的应用高频超声观察临床疑诊为冠心病患者的颈动脉管壁形态,探讨其对冠状动脉病变的预测价值.资料与方法191例疑诊为冠心病的住院患者行冠状动脉造影及颈动脉超声检查,根据颈动脉管壁形态分为颈动脉正常组、内-中膜增厚(IMT ≥1.0mm)组、稳定性斑块组及不稳定斑块组,比较4组冠心病患病率,并评估颈动脉管壁形态对冠心病的预测价值及在冠心病危险因素中的作用.结果4组冠心病患病率依次递增,组间比较,差异有统计学意义(P <0.01).颈动脉管壁形态与冠心病呈正相关(r =0.404, P <0.01).IMT ≥1.0mm、稳定性斑块及不稳定斑块是冠心病患病的独立危险因子(P <0.01),三者对冠心病的阳性预测值分别为42.86%、61.76%、73.68%.结论应用高频超声观察颈动脉管壁形态对冠心病有一定的预测价值.     

Striatocapsular infarction: MRI and MR angiography

We present a case of left striatocapsular infarction manifest clinically as a transient right hemiparesis. MRI showed a left striatocapsular infarct. Striatocapsular infarction, unlike lacunar infarction, is often associated with occlusive disease of the carotid artery. In order to screen the carotid vessels, cervical MR angiography (MRA) was performed during the same examination, demonstrating a left internal carotid artery occlusion, confirmed by contrast arteriography. MRA, a noninvasive modality, can be a useful adjunct to MRI, when diagnostic information concerning the cervical carotid artery is needed.     

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。     

Preoperative evaluation of carotid artery stenosis: comparison of contrast-enhanced MR angiography and duplex sonography with digital subtraction angiography

BACKGROUND AND PURPOSE: Contrast-enhanced MR angiography and extracranial color-coded duplex sonography are noninvasive, preoperative imaging modalities for evaluation of carotid artery stenosis. Innovative techniques and improvements in image quality require frequent reassessment of accuracy, reliability, and diagnostic value compared with those of digital subtraction angiography (DSA). We evaluated contrast-enhanced MR angiography and duplex sonography compared with DSA for detection of high-grade carotid artery stenoses. METHODS: Four readers, blinded to clinical symptoms and the outcome of other studies, independently evaluated stenoses on contrast-enhanced MR angiograms in 71 vessels of 39 symptomatic patients. Duplex sonography was also performed in all vessels. The severity of stenosis was defined according to North American Symptomatic Carotid Endarterectomy Trial criteria (0-29%, 30-69%, 70-99%, 100%). Results of both modalities were compared with the corresponding DSA findings. RESULTS: Contrast-enhanced MR angiography had a sensitivity and specificity of 94.9% and 79.1%, respectively, for the identification of carotid artery stenoses of 70% or greater. Sensitivity and specificity of duplex sonography were 92.9% and 81.9%, respectively. Combining data from both tests revealed a sensitivity and specificity of 100% and 81.4%, respectively, for concordant results (80% of vessels). CONCLUSION: Concordant results of contrast-enhanced MR angiography and duplex sonography increase the diagnostic sensitivity to 100%. The reliability of MR angiography is comparable to that of DSA. The combination of contrast-enhanced MR angiography and duplex sonography might be preferable over DSA for preoperative evaluation in most patients, thus reducing the risk of perioperative morbidity and improving the overall outcome.     

Pulsatile flow artifacts in two-dimensional time-of-flight MR angiography: Initial studies in elastic models of human carotid arteries

Initial experimental and numerical analysis of artifacts due to pulsatile flow in two-dimensional time-of-flight (2D-TOF) magnetic resonance (MR) angiography are presented. The experimental studies used elastic models of the carotid artery bifurcation cast from fresh cadavers and accurately reproducing the twisting and tapering of the human blood vessels, allowing direct comparison of images with and without flow. Prominent image artifacts, including periodic ghosts and signal loss, were produced by pulsatile flow even though flow-compensated gradient waveforms were used. The dependence of artifacts due to partial saturation on pulse sequence parameters (TR and flip angle) was investigated theoretically for a simple pulsatile velocity profile and compared with experimental results from a model of a normal carotid artery. Signal reduction was observed proximal and distal to the stenosis in a model with a 70% internal carotid artery (ICA) stenosis and a model with 90% stenoses in both the ICA and the external carotid artery. Although this study deals exclusively with 2D-TOF imaging, the methods can also be applied to evaluate other MR angiography techniques.     

Contrast-enhanced 3D MR angiography of the carotid artery: comparison with conventional digital subtraction angiography

BACKGROUND AND PURPOSE: Since 1996, several preliminary studies have shown the usefulness of contrast material-enhanced MR angiography for imaging supraaortic vessels. The aim of this study was to compare the accuracy of contrast-enhanced 3D MR angiography with that of digital subtraction angiography (DSA) in the evaluation of carotid artery stenosis. METHODS: A blinded comparison of first-pass contrast-enhanced MR angiography with conventional DSA was performed in 120 patients (240 arteries). MR angiography was performed with a 1.5-T magnet with gradient overdrive equipment, by using a coronal radiofrequency-spoiled 3D fast low-angle-shot sequence after the intravenous injection of gadodiamide. The guidelines of the North American Symptomatic Carotid Endarterectomy Trial for measuring stenosis of the internal carotid artery were applied on maximum intensity projection (MIP) images and conventional catheter angiograms. RESULTS: Grading of stenoses on MR angiograms agreed with grading of stenoses on DSA images in 89% of arteries. In the severe stenosis group (70-99%), agreement was 93%. All internal carotid occlusions (n = 28) and seven of nine pseudo-occlusions were accurately detected with contrast-enhanced MR angiography. The correlation between MR angiography and DSA for determination of minimal, moderate, and severe stenoses and occlusion was statistically significant (r = 0.91, P<.001). CONCLUSIONS: This investigation with a large number of patients confirms that contrast-enhanced MR angiography could become a diagnostic alternative to DSA in the treatment of patients with carotid artery disease.     

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。     

Spiral CT angiography and selective digital subtraction angiography of internal carotid artery stenosis.

PURPOSETo determine whether spiral CT angiography allows accurate, quantitative evaluation of anatomic abnormalities, including detection of additional lesions, delineation of plaque morphology, and estimation of degree of internal carotid artery stenosis.METHODSSpiral CT angiography with a maximum intensity projection technique was compared with selective digital subtraction angiography (DSA) in 92 carotid arteries. The category of stenosis was determined according to the North American Symptomatic Carotid Endarterectomy Trial: mild (0% to 29%), moderate (30% to 69%), severe (70% to 99%), and occlusion (100%).RESULTSIn 78 (85%) of the 92 cases, spiral CT angiography and selective DSA demonstrated the same degree of stenosis. All occlusions (n = 19) were diagnosed correctly with spiral CT angiography. Spiral CT angiography agreed with selective DSA in the classification of stenosis in 59% of the group with mild stenosis, in 82% of the group with moderate stenosis, and in 90% of the group with severe stenosis. In the groups with mild (n = 13), moderate (n = 9), and severe (n = 27) stenosis, correlation of spiral CT angiography with selective DSA was significant. Calcified plaques were readily diagnosed with the use of spiral CT angiography but delineation of ulcers was poor. Tandem lesions were not visible owing to the limited coverage.CONCLUSIONSpiral CT angiography is useful for the detection of proximal internal carotid stenoses that are greater than 30%. Depiction of mild stenoses appears to be limited. CT is superior for the detection of calcified plaques but it is not useful for the detection of ulcers.     

MRI与DSA对颈动脉狭窄和粥样硬化斑块评估能力的比较

目的 探讨MRI与DSA对颈动脉粥样硬化患者血管狭窄及粥样硬化斑块病变特点评估能力的差异.方法 46例缺血性脑血管疾病患者,超声发现颈动脉粥样硬化斑块后分别行颈动脉MRI及DSA检查.颈动脉MR检查序列包括三维时间飞跃法(3D TOF)、T1WI、T2WI、质子密度加权成像( PDWI)及增强T1WI;颈动脉DSA检查分别摄取颈动脉的正位像和侧位像.观察颈动脉分叉处管腔的狭窄程度和斑块的病变特征,包括纤维帽的状况、斑块内出血和钙化.计算Kappa值分析MRI和DSA对血管狭窄程度判断结果的一致性;应用配对卡方检验检测两种方法对溃疡斑块的检出差异.结果 89支血管的MR图像质量均满足诊断要求.MRI显示血管狭窄程度的M(范围)为50％(16％～78％),DSA显示为47％(7％～73％),二者具有很好的一致性(Kappa值为0.882,P＜0.01).MRI发现34支血管具有斑块纤维帽破溃,DSA发现10支血管具有溃疡斑块(x2=20.346,P＜0.01).此外,MRI发现37支血管有斑块内出血,71支血管有斑块内钙化,而DSA均不能显示.结论 MRI可以准确判断颈动脉的狭窄程度,在显示溃疡斑块、斑块内出血以及钙化方面较DSA更具优势.     

颈动脉超声、核素心肌显像与冠状动脉造影诊断冠心病的对比研究

 目的 探讨颈动脉超声、核素心肌灌注显像对冠心病的诊断价值.方法 对88例疑有冠心病者,以冠状动脉造影结果 作为诊断标准, 进行颈动脉超声检查和核素心肌灌注断层显像两种检查,并将结果 进行对比分析.结果 颈动脉超声诊断冠心病的敏感性为65.5%,特异性为73.3%.核素心肌灌注显像诊断冠心病的敏感性为86.2%,特异性为66.7%.结论 颈动脉超声结合核素心肌灌注显像诊断冠心病,敏感性与特异性较高,对冠心病的无创性诊断具有重要价值.     

Accuracy of contrast-enhanced MR angiography in predicting angiographic stenosis of the internal carotid artery: linear regression analysis

BACKGROUND AND PURPOSE: We sought to assess whether contrast-enhanced MR angiography is able to predict the degree of angiographic stenosis of the internal carotid artery within a clinically acceptable margin of error, thereby decreasing the need for angiography. In addition, we sought to assess whether adding ultrasound peak systolic velocity (PSV) as an additional regressor improves the accuracy of prediction. METHODS: A retrospective review of our institution's records for a 4-year period was conducted to identify all patients who had undergone evaluation of their carotid arteries using digital subtraction angiography, contrast-enhanced MR angiography, and ultrasonography. All internal carotid artery stenoses ranging from 10% to 90% at carotid angiography were selected (n = 22). Measurements were then obtained based on the North American Symptomatic Carotid Endarterectomy Trial style by using the digital subtraction angiograms and contrast-enhanced MR angiograms in a blinded fashion. The correlation between digital subtraction angiography data and contrast-enhanced MR angiography data was assessed by conducting linear regression analysis. Multiple regression analysis was then conducted to determine whether the inclusion of ultrasound PSV as an additional regressor increased the accuracy of prediction. RESULTS: The correlation between the degree of stenosis measured by digital subtraction angiography and that measured by contrast-enhanced MR angiography was r = 0.967. The 95% confidence interval for the line of means showed low errors bounds, ranging as low as +/-2.8%. The 95% confidence interval for individual prediction of angiographic stenosis based on a given contrast-enhanced MR angiographic measurement, however, was significantly larger, being no less than +/-13.6%. With the inclusion of PSV, the adjusted correlation was r = 0.965. CONCLUSION: A clear linear relationship exists between digital subtraction angiographic and contrast-enhanced MR angiographic measurements of carotid stenosis. Increasing severity of stenosis as measured by contrast-enhanced MR angiography corresponds to increasing severity at angiography. Although the predictive value of contrast-enhanced MR angiography is excellent in the mean, it is less reliable for predicting the degree of angiographic stenosis in the individual patient, showing rather wide confidence intervals. Furthermore, the inclusion of PSV as an additional regressor does not improve the predictive accuracy beyond that of contrast-enhanced MR angiography alone.     

彩色多普勒超声在颈动脉病变诊治中的应用

目的彩色多普勒超声在颈动脉病变诊治中的应用。方法应用彩色多普勒超声筛选出颈动脉粥样硬化斑块狭窄甚至闭塞的患者。超声检查内容包括斑块的大小、回声以及稳定性,斑块造成狭窄时,计算狭窄率,同时记录血管内径及血流动力学指标。重度狭窄及闭塞患者要评估颅内侧支循环的建立情况,并与磁共振血管成像(MRA)和血管造影(DSA)对比分析。最后经过临床筛选54例患者共56条颈动脉接受内膜剥脱术(CEA)或颈动脉扩张成形加支架植入(CAS)手术治疗(包括1例无症状颈动脉狭窄患者)。结果超声对斑块回声及其稳定性评价优于其它影像学,狭窄程度判断与其它影像基本相符合;对颅内侧支循环的评估与DSA相同但优于MRA;术后颈内动脉内径及血流速度较术前有明显改善,内径〔(4.1±0.5)mm VS(1.4±0.5)mm,P<0.01〕;流速〔(74.2±13.1)cm/s VS(205±132.4)cm/s,P<0.01〕。结论彩色多普勒超声对颈动脉病变的部位、范围、动脉硬化斑块的稳定性以及狭窄的程度诊断率高,能够客观反映血流动力学改变,评估颅内侧支循环的建立情况,为是否需要手术治疗提供科学依据。同时为评价治疗效果以及术后随访和临床无症状的健康筛查提供有效便捷的手段。     

Carotid artery stenosis: clinical efficacy of two-dimensional time-of-flight MR angiography.

To assess the clinical efficacy of two-dimensional time-of-flight magnetic resonance (MR) angiography in the evaluation of carotid artery stenosis, a group of patients was evaluated in which 73 vessels were studied with both MR and conventional angiography. Four experienced neuroradiologists each scored both the MR and conventional angiograms in a blinded manner by using a standardized scoring scheme. Comparison of the scores revealed a high degree of correlation. In particular, MR angiography served to discriminate reliably between mildly narrowed and severely narrowed or occluded vessels. Furthermore, severe stenoses were accurately discriminated from occlusions in all cases. MR angiography is a robust and accurate modality for the characterization of carotid artery stenosis. It is useful in conjunction with routine MR imaging of the brain in the evaluation of the patient with suspected carotid arterial disease.     

Atherosclerosis of the carotid artery: Evaluation by magnetic resonance angiography

Carotid artery atherosclerotic plaques (APs) can lead to brain ischemia, an event shown to correlate with both the degree of stenosis and the composition of the AP. Currently, accurate estimates of stenosis can be obtained by either x-ray angiography or three-dimensional time of-flight (TOF) magnetic resonance angiography (MRA). Our purpose was to determine whether three-dimensional TOF MRA images could also provide information on plaque location, morphology, and composition. Seven pre-endarterectomy patients underwent three-dimensional TOF MRA. After endarterectomy, plaque histology was evaluated. Three-dimensional TOF MRA images contained sufficient soft tissue contrast to differentiate the plaques from the surrounding tissues in all cases. Estimation of plaque morphology had 80% correlation with histology. Finally, intraplaque hemorrhage and calcification were depicted as regions of moderately high and very low intensity, respectively. These preliminary results suggest that three-dimensional TOF MRA may be useful in studying the development and progression of carotid atherosclerosis.     

数字减影CT血管成像与彩色多普勒超声对颈动脉粥样硬化斑块检出率及斑块性质、狭窄程度判定的效果比较

目的比较数字减影CT血管成像（DSCTA）与彩色多普勒超声（CDUS）对颈动脉粥样硬化斑块的检出、斑块性质及狭窄程度判定的价值以及一致性。方法回顾性分析2015年1月至2017年10月就诊的可疑颈动脉狭窄患者90例,分别进行DSCTA与CDUS检查。采用卡方检验对比斑块分布、大小、斑块性质和狭窄程度。结果90例患者双侧颈部DSCTA检查发现52例颈动脉狭窄,3例为双侧狭窄,其中轻度狭窄29例、中度狭窄9例、重度狭窄12例,完全闭塞2例;检出斑块175处,其中钙化斑块133处、混合斑块30处、脂质斑块12处。90例患者双侧颈部CDUS检查发现54处颈动脉狭窄,3例为双侧狭窄,其中轻度狭窄26例、中度狭窄10例、重度狭窄16例,完全闭塞2例;检出斑块218处,其中钙化斑块138处、混合斑块39处、脂质斑块41处。DSCTA与CDUS诊断颈动脉狭窄的差异无统计学意义（χ2=0.75,P=0.861）;CDUS检查发现了更多的可见斑块及脂质斑块, < 5 mm的小斑块（60处）检出率明显高于DSCTA（25处）,差异有统计学意义（χ2=10.035,P=0.002）。结论DSCTA与CDUS对颈动脉狭窄的诊断效能均较高,具有较好的临床应用价值。CDUS对 < 5 mm斑块的检出优于DSCTA。     

Techniques for high-resolution MR imaging of atherosclerotic plaque

Atherosclerotic cardiovascular disease is the most common cause of death in the United States. Investigation of atherosclerotic plaque morphology and composition is important because the findings may be useful in predicting prognosis or response to therapy. This study presents high-resolution magnetic resonance (MR) imaging techniques developed on a 1.5-T whole-body imager with a custom-built surface coil, for characterizing the composition and morphology of plaque removed at carotid endarterectomy. The initial comparison of MR imaging and histologic results showed good correlation. In conjunction with MR angiography, these techniques could be used in in vivo imaging to define the size, location, and contents of atherosclerotic plaque at the carotid bifurcation.     

Physiologic and anatomic assessment of a canine carotid artery stenosis model utilizing phase contrast with vastly undersampled isotropic projection imaging

BACKGROUND AND PURPOSE: Noninvasive assessment of the hemodynamic significance of carotid stenosis is often performed with MR angiography and supplemented with carotid Doppler sonography. Phase contrast with vastly undersampled isotropic projection reconstruction (PC-VIPR), a novel MR imaging technique, accelerates phase-contrast MR flow imaging and provides both images of the vessels and measurements of blood-flow velocities. For this study, we determined the accuracy of PC-VIPR blood-flow velocity measurements to determine pressure gradients across an experimental carotid stenosis. MATERIALS AND METHODS: A focal stenosis was surgically created in each common carotid artery of 6 canines. Digital subtraction angiography (DSA) was performed, and the degree of stenosis was determined using the North American Symptomatic Carotid Endarterectomy Trial methodology. A microcatheter was positioned in the carotid artery proximal and distal to the stenosis, and pressures were measured in the vessel through the catheter. PC-VIPR was then performed on a 1.5T MR imaging scanner with parameters producing 0.8-mm isotropic voxel resolution. From the velocity measurements, pressure gradients were calculated from the Navier-Stokes relationship to compare with the pressures measured by a catheter. RESULTS: Carotid stenoses in the 50%-85% range were produced in the 12 arteries. Pressure gradients across the stenoses ranged from 6 to 26 mm Hg. The pressure gradient calculated from the PC-VIPR data correlated (r = 0.91, P < .0001) with the actual pressure measurements. CONCLUSION: With PC-VIPR, a novel MR imaging technique, the hemodynamic effect of a stenosis on flow and pressure can be evaluated.