Binbin Sui

Blood Flow Pattern and Wall Shear Stress in the Internal Carotid Arteries of Healthy Subjects

Background: The carotid bifurcation is one of the most susceptible locations for atherosclerotic plaques. It is important to assess wall shear stress (WSS) and blood flow patterns in this area. Purpose: To assess local WSS and blood flow patterns at the origin of the internal carotid artery (ICA). Material and Methods: Twenty-eight ICAs of 16 healthy volunteers were studied. A cine phase-contrast magnetic resonance (MR) sequence combined with a three-dimensional paraboloid model was applied to calculate WSS values and to obtain flow parameters. WSS spatial distribution features and local flow patterns were analyzed. Results: Mean WSS was 0.560±0.180 (range −0.745 to 3.563) N/m2 at the origin of 28 ICAs. Error points were found in six vessels. Four WSS spatial distribution patterns were classified according to the location of low WSS values. Reverse WSS was found in 20 vessels. The mean oscillatory shear index (OSI) for these vessels was 0.089±0.094 (range 1.00×10−6 to 0.490). Complex flow status including reverse velocity, flow stagnancy, and high oscillating WSS was displayed in the end systole of this area. Conclusion: Flow patterns were variant and complicated at the origin of the ICAs. Different types of local WSS spatial distributions were found around the vessel circumference.

Noninvasive determination of spatial distribution and temporal gradient of wall shear stress at common carotid artery

Wall shear stress (WSS) has been proved to play a critical role in formation and development of atherosclerotic plaques. Our objective was to quantify local WSS in vivo in normal subjects, and to analyze spatial distribution patterns and determine the temporal gradient of WSS. Seventy-eight CCAs of 42 healthy volunteers at common carotid arteries (CCAs) were studied. Cine phase-contrast MR sequence was used to acquire the flow velocity information. Three-dimensional paraboloid modeling was applied to fit the velocity profiles and WSS values were calculated. Mean WSS value for CCAs was 0.783+/-0.209, with the range of WSS value from -0.541 to 3.464 N/m(2). The 95% confidence interval for mean WSS value in CCA was (0.736-0.830) N/m(2). Different WSS spatial distribution patterns were classified into three types according to the location of low WSS values during a cardiac cycle. Mean value of maximum temporal gradient of WSS was 14.12+/-5.46, with the range from 5.87 to 33.23 N/m(2)s(-1). Skewed velocity profiles were displayed in most CCAs, indicating the flow patterns in CCA were more complicated than commonly assumed. Obvious inter-subject variation were found in magnitude, spatial distribution and the temporal gradient of WSS in CCAs, and the blood flow patterns as well.

Assessment of Wall Shear Stress in the Common Carotid Artery of Healthy Subjects Using 3.0-Tesla Magnetic Resonance

Background: Wall shear stress (WSS) has been proven to play a critical role in the formation and development of atherosclerotic plaques. Measurement of WSS in vivo is significant for the clinical assessment of atherosclerosis. Purpose: To assess the magnitude and distribution of local WSS in the common carotid artery (CCA) in vivo using 3.0T magnetic resonance (MR). Material and Methods: The common carotid artery of eight healthy volunteers was studied using a cine phase-contrast MR sequence. A three-dimensional paraboloid model was applied to fit the velocity profiles, and the WSS values were calculated. The cross-sectional area, average flow velocity, maximum velocity, and flow rate were also obtained. Results: Mean WSS was 0.850±0.195 (range 0.132–3.464) N/m2 for the common carotid arteries; the spatial and temporal distribution and change of WSS were displayed. During a cardiac cycle, the mean velocity was 22.8±3.5 (16.9–28.3) cm/s, blood flow rate 8.03±1.45 (5.73–10.72) ml/s, and luminal vessel area 34.94±7.06 (24.25–49.01) mm2. Conclusion: Local WSS values in CCAs can be measured using 3.0T MR imaging combined with image-processing techniques. Intersubject variations were found in the distribution and magnitude of wall shear stress as well as in the flow profile pattern in CCAs, which may be caused by different vessel morphologies.

Association between cerebral microbleeds and the first onset of intracerebral hemorrhage - a 3.0 T MR study.

Background Cerebral microbleeds (CMBs) detected by gradient-echo MRI have been proven to be a potential risk factor for further bleeding, while the association between CMBs and the first onset of intracerebral hemorrhage has not been well investigated. Purpose To analyze the association between CMBs and the first onset of primary intracerebral hemorrhage (pICH). Material and Methods Two hundred and two consecutive inpatients with ICH and 234 consecutive outpatients without ICH as control group were enrolled in this study. MR imaging including T2*-GRE, T1W, T2W and fluid attenuated inversion recovery (FLAIR) sequences were performed to detect CMBs and other abnormalities. Prevalence, distribution, and grades of CMBs, as well as the location and size of the intracerebral hematoma were analyzed, respectively. Comparison was made between pICH and control group. Logistic analysis was performed to evaluate the association between CMBs and ICH. The correlation between hematoma size and CMBs grade/numbers was analyzed. Results CMBs were detected in 140 patients in pICH (69.3%) group and 62 patients in control group (26.5%). The incidence of CMBs in pICH group was significantly higher than that in control group (P < 0.0001). As the logistic regression analysis results, CMBs was the risk factor associated with ICH, with modulation OR value of 8.363 (95% CI 5.210–13.421). The volume of ICH with CMBs was 12.57 ± 17.23 mL, and the volume of ICH without CMBs was 17.77 ± 26.97 mL. Negative correlation was demonstrated between CMBs number and ICH volume (rs = −0.1769, P = 0.0118), as well as between CMBs grade and hematoma volume (rs = −0.1185, P = 0.1557). Conclusion CMBs may be an independent risk factor for the first onset of intracerebral hemorrhage.

Brain Magnetic Resonance Elastography on Healthy Volunteers: A Safety Study

Background: Magnetic resonance elastography (MRE) is a recently developed imaging technique that can directly visualize and quantitatively measure tissue elasticity. Purpose: To evaluate the safety of brain MRE on human subjects. Material and Methods: The study included 20 healthy volunteers. MRE sequence scan (drive signal not applied to external force actuator) and MRE study were separately performed on each volunteer at an interval of more than 24 hours. The heart rate and blood pressure of each volunteer were measured immediately before and after MRE sequence scan and MRE study. Electroencephalography (EEG) was also performed within 2 hours after each scan. The volunteers were asked about their experience of the two scans. Randomized-block analysis of variance (ANOVA) was used to analyze the data of blood pressure and heart rate. Paired t test was used to analyze the data of the two EEG examinations. The volunteers were followed up 1 week after the examination. Results: All procedures were performed on each volunteer, and no one complained of obvious discomfort. No related adverse events were reported during follow-up. There was no statistically significant difference in heart rate or blood pressure. There was a statistically significant difference (P<0.05) in EEG results in the right temporoparietal region. Increased power was found in the theta, delta, alpha, and beta2 bands. No brain injury was detected by the EEG examinations. Conclusion: Based on the study results, brain MRE examinations are safe to perform on human subjects.

Hemodynamic parameters distribution of upstream, stenosis center, and downstream sides of plaques in carotid artery with different stenosis: a MRI and CFD study

Background Histopathological studies have shown significant differences in plaque components and surface conditions between upstream and downstream of the stenosis. It can be deduced that the flow status near the plaques is different from the flow status at the upstream side, stenosis center, or downstream side of the plaque. Purpose To study the hemodynamic parameter distribution in different locations near atherosclerotic plaques in the carotid arteries with different stenosis degrees. Material and Methods Eleven patients were recruited in this study. CE-MRA was performed to obtain the carotid three-dimensional surface data and the stenosis degrees were calculated. The hemodynamic parameters including wall shear stress (WSS), pressure, and velocity near the plaques were obtained by computational fluid dynamic (CFD) method. Local hemodynamics parameters were analyzed and compared between different stenosis degree groups, and between upstream, stenosis center, and downstream sides of plaques. Relative ratio of velocity, WSS, and pressure values in different locations was calculated and compared. Results Fourteen carotid arteries (with 4 mild, 6 moderate, and 4 severe stenosis) were analyzed. Significant differences were found in Pressure max (P = 0.025), Pressure mean (P = 0.020), and Pressure min (P = 0.026) between three stenosis groups. It showed significant differences in Vmin (P < 0.001) and WSSmin (P < 0.001) between three different locations. It showed upstream to downstream ratio of WSSmax (P = 0.034) and WSSmean value (P = 0.042) was significantly different between mild and moderate/severe groups. Significant differences were found in upstream to stenosis center ratio of Pressure max value (P = 0.018), Pressure mean value (P = 0.029), and Pressure min value (P = 0.026), as well as in stenosis center to downstream ratio of Pressure min value (P = 0.042). Conclusion Velocity, WSS, pressure, and relative ratio of these parameters have certain trends in distribution around the plaques in the carotid arteries.

Distribution and features of middle cerebral artery atherosclerotic plaques in symptomatic patients: a 3.0 T high-resolution MRI study.

Abstract Objectives: To investigate the distribution and features of middle cerebral artery (MCA) atherosclerotic plaques in patients with acute ischaemic strokes using high-resolution magnetic resonance (MR) imaging. Methods: Forty-six plaques from 44 MCAs (18 right and 26 left) in patients with acute symptomatic ischaemic strokes were studied. High-resolution MR imaging including tb1 weighted imaging (T1WI), tb2 weighted imaging (T2WI), PD weighted imaging (PDWI) and three-dimensional magnetization-prepared rapid acquisition gradient-echo (MPRAGE) sequences were used to visualise the plaques. The locations of plaques were classified into ventral, distal, superior and inferior wall of the MCA on oblique sagittal images. The thickness, area and signal intensities of plaques were recorded. The stenosis degree of MCA was calculated. Results: Among all 46 plaques, 26 plaques were located at the ventral wall (56.5%), 6 at the dorsal wall (13.0%), 9 at the superior wall (19.6%), and five at the inferior wall (10.9%). The average thickness and area of plaques were 1.37 ± 0.53 mm (range: 0.61–3.20 mm) and 3.80 ± 2.13 mm2 (range: 1.01–12.2 mm2), respectively. No significant differences in plaque thickness (P = 0.464), plaque area (P = 0.107) or stenosis degree (P = 0.563) were noted between different locations. Most of the plaques (44/46) showed iso-intensity on tbl1WI. On tbl2WI and PDWI, 24 plaques showed iso-intensity, 12 plaques showed a slightly high signal intensity (SI), and eight plaques showed a slightly low SI. Intraplaque haemorrhage was found in two plaques, with high SI on tbl1WI and MP-RAGE and high or mixed SI on tbl2WI and PDWI. Discussion: Middle cerebral artery plaques in patients with acute infarction have certain tendency to locate at ventral and superior walls. Distribution and features of plaques revealed some plaque formation characteristics and would help to understand underlying mechanisms of ischaemic events.

Prediction of radiosensitivity in primary central nervous system germ cell tumors using dynamic contrast-enhanced magnetic resonance imaging

OBJECTIVE To evaluate the feasibility of dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI) for predicting tumor response to radiotherapy in patients with suspected primary central nervous system (CNS) germ cell tumors (GCTs). METHODS DCE-MRI parameters of 35 patients with suspected primary CNS GCTs were obtained prior to diagnostic radiation, using the Tofts and Kermode model. Radiosensitivity was determined in tumors diagnosed 2 weeks after radiation by observing changes in tumor size and markers as a response to MRI. Taking radiosensitivity as the gold standard, the cut-off value of DCE-MRI parameters was measured by receiver operating characteristic (ROC) curve. Diagnostic accuracy of DCE-MRI parameters for predicting radiosensitivity was evaluated by ROC curve. RESULTS A significant elevation in transfer constant (K(trans)) and extravascular extracellular space (Ve) (P=0.000), as well as a significant reduction in rate constant (Kep) (P=0.000) was observed in tumors. K(trans), relative K(trans), and relative Kep of the responsive group were significantly higher than non-responsive groups. No significant difference was found in Kep, Ve, and relative Ve between the two groups. Relative K(trans) showed the best diagnostic value in predicting radiosensitivity with a sensitivity of 100%, specificity of 91.7%, positive predictive value (PPV) of 95.8%, and negative predictive value (NPV) of 100%. CONCLUSIONS Relative K(trans) appeared promising in predicting tumor response to radiation therapy (RT). It is implied that DCE-MRI pre-treatment is a requisite step in diagnostic procedures and a novel and reliable approach to guide clinical choice of RT.

Association of plaque compositions and stenosis patterns in carotid bifurcation using MR imaging

Abstract Objectives: To investigate the relationship between plaque compositions and stenosis patterns in patients with atherosclerotic plaques at the carotid bifurcation using magnetic resonance (MR) imaging. Methods: One hundred and four carotid arteries with stenosis over 50% from 75 symptomatic stroke patients (64 male and 11 female; mean age 58·2±13·3 years) were studied. Plaque compositions were analyzed by high-resolution MR imaging using a 3·0T MR with a surface coil. Stenosis patterns were classified into three types according to contrast-enhanced MR angiography images. Correlations of different components of plaques and stenosis patterns were analyzed. Results: One hundred and four carotid arteries were analyzed. Three stenosis patterns were identified. The prevalences of the three patterns are as follows: type I (total occlusion) at 27·9% (29/104), type II (local plaque with normal distant flow) at 56·7% (59/104), and type III (local plaque with impaired distant flow) at 15·4% (16/104). The contingency coefficients between stenosis pattern and stability, intraplaque hemorrhage (IPH), lipid necrotic core (LNC), and ulcer were 0·383 (P = 0·000), 0·290 (P = 0·008), 0·439 (P = 0·000), and 0·388 (P = 0·000), respectively. Multinomial analysis showed that compared with type III vessels, type I vessels were more likely to contain IPH (P = 0·019) and less likely to contain large LNC (P = 0·001); type II vessels had a greater possibility for containing IPH than type III vessels (P = 0·009); LNC was more likely to be found in type II than in type I vessels (P = 0·000). No significant difference was found in ulceration prevalence between type II and type III vessels (P = 0·058). Conclusions: The current study demonstrated positive associations between stenosis patterns and plaque compositions.

Computed tomography perfusion source images assessment of infarct core and penumbra in acute stroke.

Abstract Objective: The purpose of this study was to develop a methodology on computed tomography (CT) perfusion source images for an acute ischemic stroke in predicting infarct core and penumbra. Methods: Computed tomography examinations, including non-contrast enhanced CT, CT perfusion and CT angiography, were performed on 24 patients with symptoms of stroke in less than 9 hours. The Alberta Stroke Program Early CT Score (ASPECTS) was analysed on arterial and venous phase CT perfusion source images and then compared with the ASPECTS on follow-up imaging for an efficacy assessment. Results: The ASPECTS on arterial phase CT perfusion source images was significantly different from venous phase CT perfusion source images (z=−2.812, p=0.005); linear regression analysis revealed that there was a statistically significant relationship between venous phase CT perfusion source images and the follow-up imaging (beta=0.715, p=0.003). Conclusion: The limited data suggested that CT perfusion source images of both arterial and venous phases may have the potential of being used as an assessment for infarct core and penumbra in acute ischemic stroke.