Effects of iodinated contrast media on common carotid and brachial artery blood flow and wall shear stress

The aim of our study was to evaluate the effect of the intravenous contrast media iomeprol on wall shear stress, blood flow and vascular parameters in the common carotid and brachial artery. Thirty outpatients undergoing thoracic or abdominal spiral CT scans were studied. The internal diameter and flow velocity of the common carotid and brachial artery were evaluated by ultrasound, and blood viscosity was measured before and after low osmolality iomeprol (Iomeron 350) injection. The wall shear stress, blood flow and pulsatility index were calculated. To test the differences between groups, the Wilcoxon rank test and Mann Whitney U test were applied. Blood viscosity decreased slightly, but significantly after contrast media (4.6±0.7 vs. 4.5±0.7 mPa.s, P=0.02). Contrarily, blood flow and wall shear stress did not change in the common carotid artery, but significantly decreased in the brachial artery (0.9±0.4 vs. 0.6±0.3 ml/s, P<0.0001, and 41.5±13.9 vs. 35.3±11.0 dynes/cm2, P<0.002, respectively), whereas the pulsatility index significantly increased in the brachial artery (5.0±3.3 vs. 7.5±5.3, P<0.001). Iomeprol injection causes blood flow and wall shear stress reduction of the brachial artery; the rise in the pulsatility index suggests an increase in peripheral vascular resistance. Further investigation is needed to evaluate whether these modifications can be clinically relevant.An erratum to this article can be found at     

MR评估在体血管壁切应力的方法探讨

目的 研究一种临床适用的MR技术在体无创性评估颈总动脉血管壁切应力(WSS)的方法.方法 选取1名健康志愿者,对其右侧颈总动脉行相位对比法MR血流定量扫描,应用三维抛物面(3DP)模型函数拟合方法,结合图像后处理技术,计算局部WSS,获取颈总动脉的血管横截面积、平均血流速度、最大速度及瞬时血流率等血流动力学参数,综合评估颈总动脉的血流动力学状态.结果 颈总动脉局部WSS值范围为(0.75±0.41)N/m2;平均血流速度为(23.4±12.0)cm/s,血管横截面积为(32.2±2.9)mm2;血流率为(7.8±4.6)ml/s.结论 MR血流定量技术结合3DP模型方法可以对颈动脉局部WSS大小、分布和变化进行评估.     

Leukoaraiosis: correlation of MR and CT findings with blood flow, atrophy, and cognition

Hypodense periventricular white-matter lesions detected by CT (leukoaraiosis) and high-intensity T2 signals detected by MR imaging were correlated with measurements of local cerebral blood flow (LCBF), cerebral atrophy, and cognitive performance. Subjects studied included elderly volunteers who were neurologically normal (n = 6), patients with chronic cerebral infarctions and intact cognition (n = 2), patients with multiinfarct dementia (n = 14), and patients with Alzheimer dementia (n = 9). Leukoaraiosis correlated with periventricular high-intensity lesions detected by MR, LCBF reductions, cognitive impairments, and cerebral atrophy. Moderate to severe leukoaraiosis was associated with LCBF reductions in the cortex, basal ganglia, and frontal white matter. Periventricular MR lesions correlated with cerebral atrophy but not with cognitive impairments or reductions in LCBF. The exquisite sensitivity of MR revealed small lesions that did not correlate with LCBF reductions and cognitive impairments. Remote subcortical white-matter lesions detected by MR did not correlate with periventricular MR lesions, leukoaraiosis, LCBF, cerebral atrophy, or cognitive performance, indicating little clinical relevance. We concluded that diffuse cerebral hypoperfusion, particularly in combination with the poor collateral circulation of white matter surrounding the lateral ventricles, is responsible for leukoaraiosis.     

Effect of mental stress on myocardial blood flow and vasomotion in patients with coronary artery disease.

In patients with coronary artery disease (CAD), mental stress may provoke ischemic electrocardiograph changes and abnormalities in regional and global left ventricular function. However, little is known about the underlying myocardial blood flow response (MBF) in these patients. METHODS: We investigated the hemodynamic, neurohumoral, and myocardial blood flow responses to mental stress in 17 patients with CAD and 17 healthy volunteers of similar age. Mental stress was induced by asking individuals to solve mathematic subtractions in a progressively challenging sequence; MBF was quantified at rest and during mental stress using 13N ammonia PET. RESULTS: Mental stress induced significant (P < 0.01) and comparable increases in rate-pressure product, measured in beats per minute x mm Hg, in both patients (from 7826 +/- 2006 to 10586 +/- 2800) and healthy volunteers (from 8227 +/- 1272 to 10618 +/- 2468). Comparable increases also occurred in serum epinephrine (58% in patients versus 52% in healthy volunteers) and norepinephrine (22% in patients versus 27% in healthy volunteers). Although MBF increased in patients (from 0.67 +/- 0.15 to 0.77 +/- 0.18 mL/min/g, P < 0.05) and healthy volunteers (from 0.73 +/- 0.13 to 0.95 +/- 0.22 mL/min/g, P < 0.001), the magnitude of flow increase was smaller in patients (14% +/- 17%) than in healthy volunteers (29% +/- 14%) (P = 0.01). The increase in MBF during mental stress correlated significantly with changes in cardiac work in healthy volunteers (r = 0.77; P < 0.001) but not in patients. CONCLUSION: Despite similar increases in cardiac work and comparable sympathetic stimulation in CAD patients and healthy volunteers, CAD patients exhibit an attenuated blood flow response to mental stress that may contribute to mental stress-induced ischemic episodes in daily life.     

Assessing coronary sinus blood flow in patients with coronary artery disease: a comparison of phase-contrast MR imaging with positron emission tomography

OBJECTIVE: This study was performed to determine whether MR imaging can be used to reliably measure global myocardial blood flow and coronary flow reserve in patients with coronary artery disease as compared with such measurements obtained by positron emission tomography (PET). SUBJECTS AND METHODS: We measured myocardial blood flow first at baseline and then after dipyridamole-induced hyperemia in 20 patients with coronary artery disease. Myocardial blood flow as revealed by MR imaging was calculated by dividing coronary sinus flow by the left ventricular mass. Coronary flow reserve was calculated by dividing the rate of hyperemic flow by the rate of baseline flow. RESULTS: Using MR imaging, myocardial blood flow at baseline was 0.73 +/- 0.23 mL x min(-1) x g(-1), and at hyperemia the blood flow was 1.43 +/- 0.37 mL x min(-1) x g(-1), yielding an average coronary flow reserve of 1.99 +/- 0.47. Using PET, myocardial blood flow was 0.89 +/- 0.21 mL x min(-1) x g(-1) at baseline and 1.56 +/- 0.42 mL x min(-1) x g(-1) at hyperemia, yielding an average coronary flow reserve of 1.77 +/- 0.36. The correlation of myocardial blood flow and coronary flow reserve measurements for these two methods was an r of 0.80 (p < 0.01) and an r of 0.50 (p < 0.05), respectively. CONCLUSION: This study shows that myocardial blood flow measurements obtained using MR imaging have a good correlation with corresponding PET measurements. Coronary flow reserve measurements obtained using MR imaging had only moderate correlation with PET-obtained measurements. Our results suggest that MR imaging flow quantification could potentially be used for measuring global myocardial blood flow in patients in whom interventional treatment for coronary artery disease is being evaluated.     

Diagnostic performance of stress perfusion and delayed-enhancement MR imaging in patients with coronary artery disease

PURPOSE: To prospectively determine the accuracy of a combined magnetic resonance (MR) imaging approach (stress first-pass perfusion imaging followed by delayed-enhancement imaging) for depicting clinically significant coronary artery stenosis (> or = 70% stenosis) in patients suspected of having or known to have coronary artery disease (CAD), with coronary angiography serving as the reference standard. MATERIALS AND METHODS: The committee on human research approved the study protocol, and all participants gave written informed consent. This study was HIPAA compliant. Forty-seven patients (38 men and nine women; mean age, 63 years +/- 5.3 [standard deviation]) scheduled for coronary angiography were prospectively enrolled: 33 were suspected of having CAD (group A) and 14 had experienced a previous myocardial infarction and were suspected of having new lesions (group B). The MR imaging protocol included cine function, gadolinium-enhanced stress and rest first-pass perfusion MR imaging, and delayed-enhancement MR imaging. Myocardial ischemia was defined as a segment with perfusion deficit at stress first-pass perfusion MR imaging and no hyperenhancement at delayed-enhancement imaging. Myocardial infarction was defined as an area with hyperenhancement at delayed-enhancement imaging. RESULTS: One patient was excluded from analysis because of poor-quality MR images. Coronary angiography depicted significant stenosis in 30 of 46 patients (65%). In a per-vessel analysis (n = 138), stress first-pass perfusion MR imaging and delayed-enhancement imaging yielded sensitivity of 0.87, specificity of 0.89, and accuracy of 0.88, when compared with coronary angiography. The diagnostic accuracy of stress first-pass perfusion MR imaging and delayed-enhancement imaging was slightly better than that of stress and rest first-pass perfusion MR imaging in the entire population (0.88 vs 0.85), in group A (0.86 vs 0.82), and in group B (0.93 vs 0.90). CONCLUSION: Stress first-pass perfusion MR imaging followed by delayed-enhancement imaging is an accurate method to depict significant coronary stenosis in patients suspected of having or known to have CAD.     

Relationship between brachial artery flow-mediated dilation and coronary flow reserve in patients with peripheral artery disease.

The aim of this study was to assess the relationship between brachial artery flow-mediated dilation (FMD) and coronary flow reserve (CFR) in patients with peripheral artery disease (PAD). METHODS: Thirty patients who had PAD, who showed no cardiac symptoms, and who had normal stress SPECT cardiac imaging results and 28 control subjects underwent brachial artery FMD assessment by ultrasound and dipyridamole 99mTc-sestamibi imaging. Myocardial blood flow (MBF) was estimated by measuring first-transit counts in the pulmonary artery and myocardial counts from SPECT images. Estimated CFR was expressed as the ratio of MBF at stress to MBF at rest. RESULTS: Patients with PAD were separated into 2 groups according to the median value of overall FMD (6.85%): group 1 (n=15) with FMD above the median (mean+/-SD, 8.78%+/-1.3%) and group 2 (n=15) with FMD below the median (mean+/-SD, 5.14%+/-0.94%). FMD was significantly higher in control subjects (11.4%+/-3.4%) than in both groups of PAD patients (P<0.001 for both). In control subjects, estimated CFR was 2.2+/-0.4-significantly higher than CFR in both groups of PAD patients (P<0.001 for both). In addition, in PAD patients of group 1, estimated CFR was 1.5+/-0.4-higher than CFR in group 2 (1.0+/-0.4) (P<0.01). When all PAD patients were considered, a significant correlation between FMD and estimated CFR was observed (r=0.56, P<0.005). CONCLUSION: Estimated CFR is significantly lower in patients with PAD than in control subjects, and CFR impairment correlates with the degree of peripheral endothelial dysfunction.     

Peyronie's disease: MR findings in 28 patients.

Induratio penis plastica (Peyronie's disease) is a chronic fibrotic process involving the penis. Proper treatment of the disease requires assessment of the degree of inflammation preceding or accompanying the fibrous Peyronie's plaques. Owing to its high tissue contrast and its multiplanar capability, MR imaging offers excellent visualization of penile anatomy. To determine the usefulness of MR imaging in the diagnosis and staging of Peyronie's disease, we used MR imaging with a surface coil to examine 28 consecutive patients with clinical evidence of the disease. Eighteen patients had contrast-enhanced MR imaging with gadopentetate dimeglumine. In seven patients who subsequently had surgery or biopsy, MR findings were correlated with histopathologic findings. On unenhanced images, fibrous plaques were shown in 20 patients. Enhanced MR images showed focal contrast enhancement around or within the plaques in seven patients. Images in three patients with plaques showed no enhancement. Images in five patients showed focal areas of contrast enhancement without evidence of plaques. Histologic studies demonstrated that the degree of contrast enhancement correlated with the extent of inflammatory cell infiltration. In two patients with unenhancing plaques on MR, histology confirmed the absence of inflammation. Our results suggest that MR imaging not only depicts the localization and extent of fibrous plaques in patients with Peyronie's disease but also reveals the presence of inflammation. This makes MR imaging the technique of choice for planning therapy and for evaluating the response to conservative treatment.     

Acute Marchiafava-Bignami disease: MR findings in two patients

Marchiafava-Bignami is a rare toxic disease seen mostly in chronic alcoholics that results in progressive demyelination and necrosis of the corpus callosum. The process may extend laterally into the neighboring white matter and occasionally as far as the subcortical regions. We present the MR imaging findings in two patients who presented acutely and review the features of the disease and of other acute alcohol-related disorders.     

Regional myocardial blood flow,glucose utilization and contractile function before and after revascularization and ultrastructural findings in patients with chronic coronary artery disease

In patients with chronic coronary artery disease, follow-up measurements of myocardial blood flow, metabolism and function were correlated with histology. In 41 patients with chronic coronary artery disease and a severely stenosed left anterior descending coronary artery, a positron emission tomographic (PET) flow/metabolism study and nuclear angiography were performed immediately before and 3 months after bypass surgery. Biopsies were taken from the left ventricular anterior wall at the time of surgery. Control biopsies were taken from donor hearts for cardiac transplantation and from hearts of patients with a defect of the atrial septum. A significant improvement of flow (P<0.01) and regional contractile function (P<0.01) was observed in the mismatch group. Glucose utilization was significantly lower (P<0.001) as compared to preoperative values. The group with preserved flow and the PET match group revealed no significant changes in flow, metabolism or function. Control biopsies revealed significantly less myolytic cells as compared to biopsies taken from both match and mismatch groups (P<0.01) and less fibrosis as compared to biopsies taken from the match group (P<0.01). Postoperatively, linear relationships were found between flow and both % fibrosis (r = 0.71,P<0.001) and regional anterior ejection fraction (r = 0.7,P<0.001). Only mismatch areas revealed significant recovery of both flow and function after revascularization with a disappearance of enhanced glucose uptake. The better linear correlation between flow and % fibrosis after surgery as compared to preoperatively was probably due to improvement of flow values in the mismatch group.This study was presented in part at the 41st annual meeting of the Society of Nuclear Medicine, Orlando, Florida, 1994     

Intraocular lesions in patients with systemic disease: findings on MR imaging

Twenty-one intraocular lesions associated with various systemic diseases in 15 patients were studied by MR imaging. The disorders included diabetes mellitus, cardiovascular disease, Beh?et disease, sarcoidosis, and ankylosing spondylitis. MR was performed on a 0.5-T system using a surface-coil technique. Ophthalmoscopic visualization of the fundus was precluded by the presence of opaque media in all cases. MR was found to be effective in demonstrating intraocular bleeding, vitreous opacity, detached lesions of the posterior pole, and eyeball deformity. Surface-coil MR is a useful adjunct in the evaluation of the eyes affected by systemic diseases, especially in patients with opaque media.     

Intraocular lesions in patients with systemic disease: findings on MR imaging

Twenty-one intraocular lesions associated with various systemic diseases in 15 patients were studied by MR imaging. The disorders included diabetes mellitus, cardiovascular disease, Beh?et disease, sarcoidosis, and ankylosing spondylitis. MR was performed on a 0.5-T system using a surface-coil technique. Ophthalmoscopic visualization of the fundus was precluded by the presence of opaque media in all cases. MR was found to be effective in demonstrating intraocular bleeding, vitreous opacity, detached lesions of the posterior pole, and eyeball deformity. Surface-coil MR is a useful adjunct in the evaluation of the eyes affected by systemic diseases, especially in patients with opaque media.     

Altered vertebrobasilar flow in children: angiographic,MR, and MR angiographic findings.

PURPOSETo characterize the clinical, MR, MR angiographic, and conventional angiographic findings in vertebrobasilar disease in children.METHODSEight children with posterior circulation ischemia and infarction had conventional spin-echo MR and MR angiography of the head and neck. Six patients had conventional angiography.RESULTSSix patients had alteration of vertebral or basilar artery flow void on spin-echo images. MR angiography showed all six cases of angiographically proved vertebrobasilar dissection or occlusion despite overestimating the extent of arterial abnormality in two patients. In two patients the intracranial peripheral branch cutoff shown at angiography was correctly predicted on screening MR angiography.CONCLUSIONPosterior circulation infarction in children is usually secondary to traumatic injury to the vertebrobasilar circulation. MR and MR angiography noninvasively show vertebrobasilar flow disturbances and compare favorably with angiography in documenting dissection or occlusion of the vertebrobasilar circulation. MR angiography may obviate the need for invasive angiography in these children at diagnosis and during follow-up of anticoagulation therapy.     

The influence of flow, vessel diameter, and non-newtonian blood viscosity on the wall shear stress in a carotid bifurcation model for unsteady flow

OBJECTIVES: The atherosclerotic process in arteries is correlated with the local wall shear stress (WSS). Plaque development particularly occurs in regions with recirculation (ie, where the WSS oscillates). We investigated the effects of non-Newtonian blood viscosity, variations in flow rate, and vessel diameter on wall phenomena in a carotid bifurcation model. MATERIALS AND METHODS: The flow through a model of a carotid artery bifurcation was simulated by means of the finite element method. The whole-blood viscosity is a function of shear rate, and was modeled by the Carreau-Yasuda (CY) model. Flow rate and vessel morphology were assessed with magnetic resonance imaging. Flow rate, blood viscosity, and hematocrit levels (Hct) were measured in 49 healthy volunteers. We propose an adaptation of the CY model so that differences in Hct can be incorporated; furthermore, plasma viscosity was varied in the CY model. RESULTS: The data from our model indicate that flow increases have a larger effect on the WSS than predicted with a simple paraboloid model. Hct had more influence on the WSS when the plasma viscosity was low. Low plasma viscosity was associated with a low WSS, which implies a contradiction, because both high WSS and low plasma viscosity are thought to be indicators for a healthy system. Maximum WSS oscillations were found at the edges of the recirculation region. CONCLUSIONS: Flow and diameter changes have significant influence on wall shear stress values; the same is true for the viscosity, but to a lesser extent.     

MR findings in patients with disabling musculocutaneous chronic graft-versus-host disease

OBJECTIVE: To describe musculocutaneous MR-findings responsible for disability in chronic graft-versus-host disease (cGVHD) after allogeneic hematopoietic cell transplantation (HCT). MATERIAL AND METHODS: Between June 2005 and February 2008, we performed whole-body musculoskeletal magnetic resonance imaging (MRI; n = 12) or regional MRI (n = 4) in 16 consecutive patients presenting with disabling sclerodermatous cGVHD (e.g., skin edema, fixed deep dermal sclerosis, joint contractures, painful muscular contractures, or myalgia). RESULTS: In all patients, MRI showed musculocutaneous abnormalities reflecting different degrees of inflammation and collagen tissue involvement of the skin (n = 10), subcutaneous fat tissue (n = 13), muscle fasciae (n = 16), subfascial muscular septae (n = 6), or findings compatible with myositis (n = 3). The most frequently involved muscle fasciae comprised those of the vastus lateralis muscle (n = 12), biceps femoris muscle (n = 11), gastrocnemius medialis muscle (n = 8), serratus anterior muscle, and latissimus dorsi muscle (each, n = 5). Increased signal of involved tissues on STIR-images and fat-saturated postgadolinium T1-weighted images represented the most frequent MR-signal abnormalities. CONCLUSION: MR imaging of musculocutaneous cGVHD allows accurate evaluation including assessment of deep tissue infiltration and assists in the differential diagnosis.