Multislice Spiral CTA In Carotid Atherosclerosis And Vertebral Artery Hemodynamics

Carotid artery stenosis is one of the important risk factors of cerebral ischemia and cerebral infarction.About 30% of ischemic stroke is caused by carotid stenosis.Although DSA is the current gold standard for the diagnosis of the disease,but there are some risks in the inspection technology,and the price is high,to a certain extent,limiting the clinical application of DSA.With the wide application of head and neck CTA technology,it has largely replaced the traditional gold standard DSA in the diagnosis of carotid vascular disease.Therefore,head and neck CTA technology can be timely and efficient diagnosis of carotid artery stenosis.In order to obtain high quality vascular imaging in the past,it is often necessary to increase the dose of contrast agent or increase the dose of radiation.Thus,the application of CT angiography increases the radiation dose received by the patient and the recipient.How to reduce the radiation dose in patients with CTA examination has been the focus of attention of the radiology medical community.Low voltage combination with iterative techniques and low concentration of contrast agent in head and neck CTA to reduce the radiation dose and contrast agent volume,but reduce the contrast agent concentration will cause intravascular CT value decreased,image quality declined,high iodine flow rate can get higher vascular signal.High iodine flow rate combination with automatic tube current technology and ASIR can ruduce radiation dose under ensuring the image quality.Carotid CTA has the advantages of non-invasive,fast and so on.It can accurately display the range of neck vascular stenosis,and the degree of plaque,while display tiny blood vessels,evaluation of vessel wall changes and adjacent cervical structures and local soft tissue lesions and is better than DSA.Gender,age,hypertension and diabetes were independent risk factors for atherosclerosis.Age was the most significant risk factor for carotid atherosclerosis.However,in both sexes and different ages,whether carotid plaque character and the degree of carotid stenosis of the carotid common artery and carotid internal artery are statistical differences.Few studies at home and abroad.In addition,about 1/4 of ischemic stroke in the vertebrobasilar system,including upstream blood flow confluence and downstream blood flow dispersion.It is necessary to analyze the hemodynamic characteristics of the individual patients in order to understand the cerebral posterior circulation.Based on CTA images,the determined distribution of hemodynamic parameters in the vertebrobasilar system can understand the association between the posterior circulation of the brain and the probability of atherosclerotic plaque formation,Few studies at home and abroad..The present study evaluates the combination of a high iodine delivery rate with high noise index for Radiation dose reduction head and neck angiography(CTA)and optimized scanning mode.At the same time,610 patients with cervical CTA were analyzed by quantitative analysis of carotid artery stenosis and classification of carotid plaques.To investigate the clinical significance of the relationship between carotid artery stenosis and the nature of carotid plaque and the relationship between sex and age.Finally,based on the head and neck CTA images,we determined the distribution of hemodynamic parameters in the vertebral basilar artery system,and enhanced our understanding of the relationship between the posterior circulation and the incidence of atherosclerotic plaque.Part Ⅰ Evaluation of a High Iodine Delivery Rate in Combination With High noise index for Dose Reduction in head and neck Computed Tomography AngiographyObjective: Head and neck CTA examinations are usually performed with high voltage and high volume contrast agents,but with high radiation dose and side effects of contrast agents.The present study evaluates the combination of a high iodine delivery rate With High noise index for Radiation dose reduction head and neck angiography(CTA).Methods: Of 64 cases of routine head and neck CTA examination were randomly divided into two groups.The control group of 32 cases,using the tube voltage 100 KV,noise index: 20,the image was reconstructed using 50%ASIR,contrast agent: 350mg/ml,the total amount of contrast agent 1ml/kg.The test group of 32 cases,using the tube voltage 100 KV,noise index: 25,the image was reconstructed using 50%ASIR,contrast agent 400mg/ml,the total dose of contrast agent 0.80ml/kg.Contrast to noise ratio(CNR),signal to noise ratio(SNR)and subjective image quality score of carotid artery image and the radiation dose of patients were statistically analyzed between two groups.Results: 64 subjects,the control group of 32,with an average age of 71.28 ±11.75 years old,The average BMI was 25.56 ±3.03.The test group was 32,with an average age of 70.66 ±9.22 years old.BMI averaged 25.35±2.68.There was no significant difference in gender composition,age and BMI between the two groups,(P value of gender composition was0.798,t value of age and BMI were 0.010,0.294),P>0.05.Comparison of the test group and the control group radiation dose parameters showed that plain CTDIvol,DLP and ED were statistically different(t value were 8.700,9.551,9.551 respectively),P<0.001 and enhanced CTDIvol,DLP and ED were statistically different(t value were 8.700,9.551,9.551 respectively),P<0.001.The radiation dose in test group were lower than the control group,the test group CTDIvol,DLP and ED,and compared with the control group were reduced by 20.20%,22.71% and 22.48%.The enhancement of CTDIvol,DLP and ED were decreased by 18.12%,19.91% and 19.84%,respectively.Compared with the control group,the average CT value of the experimental group was higher(t=3.517),P=0.001.But SNR,CNR and the score of the two groups had no significant difference(t value were 9.551,0.585,1.217 respectively),P>0.05.Conclusions: A high iodine delivery rate with high noise index permits radiation dose and contrast volume reduction in head and neck CTA without affecting the image quality and can be recommended in routine scanning method.PartII A clinical study in the relationship between carotid atherosclerosis and stenosis and gender and age by carotid artery CTAObjective: Carotid atherosclerosis has been a widely recognized risk factor for stroke.Stroke is caused by cerebral ischemia,of which about 1/3 are caused by carotid atherosclerosis and stenosis.Therefore,the accurate diagnosis of carotid atherosclerosis and the accurate evaluation of the degree of stenosis to choose the appropriate treatment can significantly improve the prognosis,reduce the rate of disability.To quantitatively analyze the relationship between carotid stenosis and carotid plaque character and gender or age and to evaluate the clinical value in carotid artery stenosis and atherosclerotic plaque character by 256-slice and GE(DiscoveryCT750HD)carotid CTA.Method: A retrospective analysis of 610 cases image data carotid angiography,male 355 cases,female 255 cases,with an average age of 57.20±12.89 year old.Maximum density Image(MIP),Multi-planar reconstruction(MPR),Curved planar reconstruction(MPR)volume rendering(VR)technology were used in post-processing work staions,carotid artery,internal carotid artery atherosclerotic plaque character and degree of stenosies were measured.To analyze the relationship between carotid plaque and sex and gender and age group,carotid plaque stenosis and gender and different age groups and whether the different side of the common carotid artery and internal carotid artery plaque nature and stenosis different.Results: Of the 610 patients,there were a total of 1233 carotid artery stenosis,mild stenosis of 1103,moderate stenosis of 60,severe stenosis of 69.Carotid plaques were detected in 1231 cases,soft plaque in 572,hard plaque in 659 the incidence of carotid plaque was higher in male than in female(χ2 value of LCCA,RCCA,LICA 及 RICA were 4.68,5.048,9.673,6.811 respectively),P<0.05.The incidence of non calcified plaque was highest in both sides of the common carotid artery in male(χ2 value of LCCA and RCCA were 9.278,10.322),P<0.05,and calcified or mixed plaque was the highest proportion in both carotid internal artery in female(χ2 value of LICA and RICA in different sex were 9.932,11.969),P<0.05.The incidence rate of carotid artery stenosis was higher in female than in female(χ2 value of LCCA,RCCA,LICA 及 RICA in different sex were 4.688,5.048,9.673,5.048),P<0.05.The incidence of moderate or severe stenosis LCCA in male(9.3%)was higher than that in female,(χ2 value is 4.880)P<0.05.The incidence of moderate or severe stenosis RICA in male(22%)was higher than that in female(χ2=12.726),P<0.001.There was no significant difference in the degree of stenosis between RCCA and LICA in male(χ2 value were 0.386,2.318),P>0.05.With the increase of age,the incidence of plaque was gradually increased(χ2 value of LCCA,RCCA,LICA and RICA in different age groups were 99.204,52.725,106.147,62.725 respectively),P<0.001.and the incidence rate of LCCA,RCCA,LCCA and RCCA was the highest in patients over 60 years old,and the highest incidence rate was RCCA,accounting for 56.6%.With the increase of age,the incidence of carotid stenosis increased gradually(χ2 value of LCCA,RCCA,LICA and RICA in different age groups were 99.204,62.725,106.14,119.351 respectively),P<0.001,group of patients over the age of 60,in RCCA,LICA had moderate or severe stenosis proportion is higher than between the 40 age group and 40-60 years group(χ2 value were 6.267,6.769),P<0.05.There was no significant difference in the incidence rate of carotid artery stenosis,carotid artery plaque and plaque character between the left and right common carotid artery(χ2 value were 0.990,1.761),P>0.05,and no significant difference in the incidence rate of carotid artery stenosis,carotid artery plaque and plaque character between the left and right internal carotid artery(χ2 value were 2.253,0.052),P>0.05.Conclusion: Carotid CTA has the advantages of non-invasive,rapid and economical and can objectively show the degree of carotid stenosis,plaque location and the character of plaque.Gender and age are very important-actors of carotid stenosis.Carotid CTA can be used as a routine method for screening carotid atherosclerotic stenosis.Part III Interplay of Proximal Flow Confluence and Distal Flow Divergence in Patient-Specific Vertebrobasilar systemObjective: The stenosis of the vertebral artery origin is the main cause of posterior circulation ischemia,even leading to death.25%-40% in patients with extracranial arterial stenosis occurred at extracranial vertebral artery.The stenosis of vertebral artery origin is the main cause of elderly patients with posterior circulation ischemia.Approximately one-quarter of ischemic strokes involve the vertebrobasilar arterial system that includes the upstream flow confluence and downstream flow divergence.A patient-specific hemodynamic analysis is needed to understand the posterior circulation.The objective of this study is to determine the distribution of hemodynamic parameters in vertebrobasilar system,based on the computer tomography angiography images.Materials and Methods: CTA scans were performed in all 352 patients using Discovery CT750 HD(HDCT,GE,Milwaukee,WI,USA)from the aortic arch to the apex of the skull.Here,the interplay of upstream flow confluence and downstream flow divergence was hypothesized to be a determinant factor for the hemodynamic distribution in vertebrobasilar system.A computational fluid dynamics model was used to compute the flow fields in patient-specific vertebrobasilar models.The inlet and outlet boundary conditions were the aortic pressure waveform and the flow resistances,respectively.Results: The up stream flow convergence and downstream flow divergence are frequent sites for atherosclerosis and aneurysm,respectively.Low TAWSS and high OSI occurred near the two sites,Subject B had the maximal SAR-TAWSS(P<0.05).While subject D had the minimal SAR-TAWSS.Moreover,SAR-OSI had a low value and SAR-transWSS was zero in the two sites.A 50% reduction of total outlet area was found to induce a ten-fold increase in surface area ratio of low time-averaged wall shear stress(TAWSS ≤ 4 dynes/cm2).Conclusion: This study performed ahemodynamic analysis inpatient vertebrobasilar system.The interplay of upstream flow confluence and downstream flow divergence was found to significantly affect the distribution of hemodynamic parameters(e.g.,streamlines,TAWSS,OSI andtransWSS)in patients of nostenoses andaneurysms.The outlet resistance resulting from the distal microvas culature should be accurately estimated when a CFD simulation is carried out in large arteries of vertebrobasilar system.This study enhances our understanding of the posterior circulation associated with the incidence of atherosclerotic plaques.