| PART ONE IMAGING ANATOMY OF CAROTID ARTERY BASED ON CT ANGIOGRAPHYObjective: To explore the imaging anatomical characteristics of carotid artery based on CT angiography,and to provide the imaging anatomical basis for head and neck endovascular interventional therapy and neck surgery.Methods: The clinical and imaging data of 200 patients who received CTA examination of head and neck and met the inclusion criteria were retrospectively analyzed,including 100 males and 100 females.(1)The common carotid artery(CCA)and extracranial internal carotid artery(EICA)were quantitatively measured.The measurement indicators were as follows:(1)The length of the CCA,the diameter at the beginning of CCA,the diameter at the midpoint of CCA and the common carotid tortuosity index(CCTI).The right CCA proximal measurement point was placed at the beginning of the truncus brachiocephalicus.(2)The length of the EICA,the diameter at the beginning of EICA,the diameter at the midpoint of EICA,the diameter at skull base of EICA and the internal carotid tortuosity index(ICTI).The CCA and EICA measurement parameters of the left side and right side,the male and female groups and the group of age<60 years old and the group of age ≥60 years old were compared respectively.The correlation between age and the measurement parameters of CCA and EICA were analyzed.(2)Morphological evaluation of EICA was performed.The evaluation indicators were as follows:(1)The EICA was categorized as straight,tortuosity,coiling,or kinking.(2)To assess posterior deviation of the EICA.A line from the transverse foramen of C1 to it of C5 on the VR lateral image was drawn.When the posterior deviation of EICA ran beyond this line,it was assessed as(+).(3)To assess medial deviation of the EICA.If deviation to pharyngeal posterior wall was observed,it was assessed as(+).The morphology of EICA of male and female groups,the group of age<60years old and the group of age ≥60 years old were compared respectively.(3)The level of carotid artery bifurcation was assessed as follows:(1)The level of carotid artery bifurcation in relation with the cervical vertebral levels.(2)The distance between the carotid artery bifurcation and the ipsilateral mastoid process and mandibular Angle was measured.The distance between the carotid artery bifurcation and the ipsilateral mastoid process and mandibular Angle were compared between male and female groups.Results:(1)The measurement parameters of CCA and EICA were as following:(1)The left CCA length was(12.53±1.10)cm,the diameter at the beginning of left CCA was(10.97±2.25)mm,and the diameter at the midpoint of left CCA was(6.70±0.86)mm.The right CCA length was(13.51±1.21)cm,the diameter at the beginning of right CCA was(14.35±2.70)mm,and the diameter at the midpoint of right CCA was(6.85±0.95)mm.The right CCTI was greater than left CCTI(P < 0.001).The left EICA length was(8.22±1.14)cm,the diameter at the beginning of left EICA was(8.40±1.30)mm,the diameter at the midpoint of left EICA was(4.43±0.50)mm,and the diameter at skull base of left EICA was(5.38±0.70)mm.The right EICA length was(8.20±1.15)cm,the diameter at the beginning of right EICA was(8.18±1.23)mm,the diameter at the midpoint of right EICA was(4.43±0.57)mm,and the diameter at skull base of right EICA was(5.38±0.60)mm.The left ICTI was greater than right ICTI(P=0.008).(2)The length of the left and right CCA and the diameter at the beginning and midpoint of left and right CCA in the male group were all greater than those in the female group.The length of the left and right EICA and the diameter at the beginning,midpoint and skull base of left and right EICA in the male group were also all greater than those in the female group(P<0.05).There was no significant difference in CCTI between the two groups(P>0.05).The ICTI in female group was higher than that in male group (left side:P=0.039;right side: P = 0.024).(3)The length of the left and right CCA,the diameter at the beginning and midpoint of left and right CCA in the group of age ≥60 years old were all greater than those in the group of age<60 years old.The length of the left and right EICA and the diameter at the skull base of left EICA in the group of age ≥60 years old were also all greater than those in the group of age<60 years old(P<0.05).There were no significant differences between the two groups in the diameter at beginning and midpoint of the left and right EICA and in the diameter at the skull base of the right EICA(P>0.05).The CCTI(left side: P<0.001;right side: P<0.001)and ICTI(left side: P<0.001;right side: P<0.001)in the group of age ≥60 years old were significantly greater than in the group of age<60 years old.(2)The morphological evaluation of EICA:(1)There was no statistical difference between the male group and the female group in staight,tortuosity,coiling and kinking type of EICA(P>0.05).The positive rate of EICA posterior deviation in female group was higher than that in male group(P=0.002).There was no significant difference in the positive rate of EICA deviation to pharyngeal posterior wall between the male group and the female group(P=0.215).(2)The tortuosity type(P<0.001)and kinking type(P<0.001)of EICA in the group of age ≥60 years old were both more than that in the group of age < 60 years old.There was no significant difference in the coiling type of the EICA between the two groups(P=0.056).The positive rate of EICA posterior deviation and EICA deviation to pharyngeal posterior wall in the group of age ≥60 years old were both higher than that in the group of age<60 years old(P<0.05).(3)Carotid bifurcation level assessment:(1)The carotid bifurcation level was most frequently seen at the lower level of the C3(41/200,20.5%)on the left side,and at the level of C3-4 intervertebral space on the right side(45/200,22.5%).The distance between left and right carotid bifurcation and ipsilateral mastoid process and mandibular Angle in male group was greater than that in female group(P<0.05).(4)Correlation between age and CCA and EICA measurement parameters: age was significantly positively correlated with CCTI(left side:r=0.640,P < 0.001;right side:r=0.504,P < 0.001)and ICTI(left side:r=0.514,P<0.001;right side:r=0.580,P<0.001).Age was positively correlated with the left and right CCA length,the diameter at the beginning of left and right CCA,and the diameter at the midpoint of left and right CCA.Age was also positively correlated with the left and right EICA length,the diameter at the midpoint of left and right EICA,and the diameter at the skull base of left and right ICA(P<0.05).There was no significant correlation between age and the diameter at the beginning of left and right EICA(P>0.05).Conclusion: The left extracranial segment of internal carotid artery is more tortuous than the right.Both the length and diameter of the carotid artery are larger in males than in females.The tortuosity of extracranial internal carotid artery is higher in females than that in males.The length,diameter and tortuosity of carotid artery are increased with age,but there is no correlation of the diameter at the beginning of left and right EICA with age.Carotid bifurcation is usually located at the level of C3-4.Anatomical measurement and morphological assessment of extracranial carotid artery can provide imaging anatomic basis for the endovascular intervention of the anterior circulation and the planning of cervical surgery.PART TWO THE CORRELATION OF CERVICAL ARTERY TORTUOSITY WITH INTRACRANIALAND CERVICALARTERIAL DISEASES—A STUDY BASED ON CT ANGIOGRAPHYObjective: To explore the correlation of cervical artery tortuosity with spontaneous cervicocerebral artery dissection(s CCD)and intracranial aneurysm(IA).Methods:(1)The clinical and imaging data of 66 patients with unilateral or bilateral s CCD who underwent CTA examination of head and neck were retrospectively analyzed.Sixty-six patients without s CCD who underwent head and neck CTA examination during the same period and matched s CCD group in age and sex were included as control group.The common carotid tortuosity index(CCTI),the internal carotid tortuosity index(ICTI)and the vertebral tortuosity index(VTI)were measured from CTA images.Morphological evaluation of the carotid siphon and the extracranial internal carotid artery(EICA)was performed,and the evaluation indicators were as follows:(1)The carotid siphons were classified into five types,which were type Ia,type Ib,type II,type III and type IV.(2)EICA was categorized as tortuosity,coiling or kinking.Clinical data,tortuosity index of cervical artery and the morphology of internal carotid artery(ICA)were compared between s CCD group and control group.According to the arterial dissection location,the dissection group was divided into the ICA dissection subgroup and the vertebral artery(VA)dissection subgroup.The tortuosity index of cervical artery were compared between ICA and VA dissection subgroups and the corresponding control group.The receiver operating characteristic(ROC)curve was analyzed to explore the optimal cutoff value of the tortuosity index of the cervical artery for the prediction of arterial dissection.Independent risk factors for s CCD were analyzed using multivariate logistic regression.(2)Clinical and imaging data of 100 patients with single or multiple IA who underwent head and neck CTA were retrospectively analyzed.A total of 100 patients without IA who underwent head and neck CTA examination during the same period and matched with IA group in age and sex were included as control group.CCTI,ICTI and VTI were measured from CTA images.Morphological measurement of IA was performed,and the IA measurement indicators were as follows:(1)aneurysm diameter.(2)aneurysm neck size.(3)aneurysm aspect ratio(AR).Morphological evaluation of the carotid siphon and EICA was performed,and the evaluation indicators were as follows:(1)The carotid siphons were classified into five types,which were type Ia,type Ib,type II,type III and type IV.(2)EICA was categorized as tortuosity,coiling or kinking.Clinical data,tortuosity index of cervical artery and the morphology of ICA were compared between IA group and control group.The IA group was divided into the IA ruptured group and the unruptured group,the single and multiple IA group,and the group of IA diameter <5mm and the group of IA diameter ≥5mm.The tortuosity index of cervical artery and the morphology of ICA were compared in subgroups.The correlation between tortuosity index of cervical artery and IA morphological parameters was analyzed.Results:(1)Of the 66 patients in the s CCD group,45 patients had ICA dissection and 21 patients had VA dissection.There was no statistically significant difference in vascular risk factors between s CCD group and control group(P >0.05).The ICTI(P <0.001)and VTI(P=0.008)were higher in the patients with s CCD than in the controls.The CCTI showed no statistically significant differences between patients with s CCD and controls(P=0.962).Type III(P=0.001)and Type IV(P <0.001)carotid siphons were more common in the patients with s CCD.Type Ib carotid siphon was less common in patients with s CCD(P=0.003).The presence of carotid siphons of Type Ia and Type II had no differences between the two groups(P > 0.05).The prevalence of any vessel tortuosity(P < 0.001),coiling(P=0.018)and kinking(P=0.006)of EICA was higher in the patients with s CCD.There were no statistically significant differences in the prevalence of tortuosity(P=0.460)between the two groups.The ICTI(P < 0.001)and VTI(P=0.010)of ICA dissection subgroup were higher than those of control group.The CCTI showed no statistically significant differences between the two groups(P=0.790).The ICTI of VA dissection subgroup was higher than that of control group(P=0.002).CCTI and VTI had no statistical difference between the two groups(P>0.05).There was no significant difference in the tortuosity index of the dissected side artery and the contralateral artery in patients with s CCD(P > 0.05).At the optimal cutoff ICTI values of 19.18(AUC=0.731,P<0.001),where the value of sensitivity and specificity were considered maximal,the sensitivity and specificity were 67% and 73%.When the VTI values were at the optimal cutoff of 15.78(AUC=0.633,P=0.008),the sensitivity and specificity were 35% and 92%.ICTI(odds ratio [OR]=2.964;P=0.026),VTI(OR=5.141;P=0.009),and Type III carotid siphons(OR=4.654;P=0.003)were independently associated with the risk of s CCD.(2)A total of 129 IAs were detected in 100 patients with IA,including41 cases of ruptured IA,59 cases of unruptured IA,74 cases of single IA,and 26 cases of multiple IA,65 cases with IA diameter less than 5mm and35 cases with IA diameter greater than or equal to 5mm.Patients with hypertension in IA group were more than those in control group(P=0.002).The ICTI was higher in the patients with IA than in the controls(P<0.001).CCTI and VTI had no statistical difference between the two groups(P>0.05).Type IV carotid siphons was more common in the patients with IA(P=0.016).The presence of carotid siphons of Type Ia,Type Ib,Type II and Type III had no differences between the two groups(P > 0.05).The prevalence of any vessel tortuosity(P=0.001),coiling(P=0.006)and kinking(P=0.007)of EICA was higher in the patients with IA.There were no significant differences in CCTI,ICTI and VTI between the IA ruptured group and the IA unruptured group,the single IA group and multiple IA group,and the group of IA diameter < 5mm and the group of IA diameter≥5mm(P>0.05).There were no significant differences in carotid siphons(including five types)between the IA ruptured group and unruptured group,the single IA group and multiple IA group,and the group of IA diameter<5mm and the group of IA diameter≥5mm(P>0.05).There were no significant differences in any vessel tortuosity,tortuosity,coiling and kinking of EICA between the IA ruptured group and unruptured group,and the single IA group and multiple IA group(P > 0.05).The prevalence of coiling of EICA in the group of IA diameter≥5mm was lower than that in the group of IA diameter < 5mm(P=0.048).ICTI(r=0.226,P=0.023)and VTI(r=0.197,P=0.049)were positively correlated aneurysm neck size,while CCTI(r=-0.223,P=0.026)was negatively correlated with AR.ICTI(odds ratio [OR]=1.708;P=0.002),hypertension(OR=3.847;P< 0.001),and smoking(OR=3.003;P=0.032)were independently associated with the risk of IA.Conclusion: The ICA and VA tortuosity is associated with s CCD,and the higher the degree of tortuosity of the cervical artery,the higher the risk of arterial dissection.ICA tortuosity is associated with intracranial aneurysm,but cervical artery tortuosity seems to reduce the risk of growth of intracranial aneurysm.There is no association of cervical artery tortuosity with the number and the rupture status of intracranial aneurysm.Our findings suggest that the redundant carotid siphon may be a potential imaging biomarker for evaluating and predicting the risk of s CCD and IA.PART THREE STUDY ON THE CORRELATION OF INTERNAL CAROTID ARTERY TORTUOSITY WITH IMAGING MARKERS OF CEREBRAL SMALL VESSEL DISEASE,CHANGES OF BRAIN STRUCTURE AND PERFUSIONObjective: To investigate the correlation of internal carotid tortuosity with imaging markers of cerebral small vessel disease(CSVD)and changes in cognitive function,as well as the changes of brain structure and 3D-ASL cerebral perfusion.Methods: A prospective analysis was made of 58 patients in the ICA tortuosity group who underwent head and neck magnetic resonance angiography(MRA)and found internal carotid artery tortuosity index(ICTI)≥20.Fifty-nine patients with ICTI<20 and matched age,sex and educational years during the same period were included as control group.All the subjects underwent clinical history acquisition,cognitive function assessment and brain MRI scanning.The cognitive function scales included the Minimental State Examination(MMSE)and the Montreal Cognitive Assessment(Mo CA).Brain MRI scan sequences included T2-FLAIR,T2 WI,3D-T1 WI,3D-ASL(PLD=1525ms,PLD=2525ms).MRI image evaluation and post-processing analysis are as follows:(1)Visual evaluation was performed on the imaging markers of CSVD,including white matter hyperintensity(WMH),enlarged perivascular space(EPVS)and lacunes.The volume of WMH was also quantitatively calculated.The WMH score,WMH volume,EPVS score,lacunes and cognitive function score were compared between the ICA tortuosity group and the control group.The correlation between ICTI and WMH volume,WMH score,EPVS score and MOCA scale score was analyzed.According to the severity of WMH and EPVS,WMH and EPVS were respectively divided into grade I and grade II.Multivariate logistic regression was used to analyze the independent risk factors of grade II WMH and grade II EPVS.(2)Accubrain software was used to calculate the relative volume of 64 brain regions including hippocampus,amygdala,caudate nucleus,putamen,globus pallidus,thalamus,cingulate gyrus,insula,white matter,gray matter and others.The atrophy rate of 13 brain regions including bilateral frontal lobe,occipital lobe,temporal lobe,parietal lobe,cingulate gyrus,insula and cerebellum was also calculated.The relative CBF values of 27 brain regions including left and right temporal cortex,left and right medial temporal cortex,left and right lateral temporal cortex,left and parietal cortex,left and right occipital cortex,and left and right orbital frontal and deep white matter were calculated by Accubrain software.Results:(1)The volume of periventricular WMH(P=0.011)and the total volume of WMH(P=0.011)in the ICA tortuosity group were higher than those in the control group.There was no significant difference in deep white matter WMH volume between the two groups(P=0.055).The total WMH score in ICA tortuosity group was higher than that in control group(P=0.005).The EPVS score of basal ganglia(P=0.005)and the total EPVS score(P=0.008)in ICA tortuosity group were higher than those in control group.There was no significant difference between the two groups in the EPVS score of white matter(P=0.409).Mo CA score in ICA tortuosity group was lower than that in control group(P<0.001),while MMSE score showed no statistically significant difference between the two groups(P=0.144).ICTI was positively correlated with WMH volume(r=0.2699,P=0.0035),WMH score(r=0.4392,P<0.0001)and EPVS score(r=0.2766,P=0.0025),while ICTI was negatively correlated with MOCA score(r=-0.4093,P<0.0001).ICTI(OR=2.068,P<0.001;OR=2.139,P<0.001)was independently associated with the risk of grade II WMH(The dependent variables included WMH volume and WMH score).ICTI(OR=1.806,P=0.002)was independently associated with the risk of grade II EPVS.(2)The relative volumes of parenchyma(P=0.013),gray matter(P=0.003),right temporal lobe(P=0.030),left occipital lobe(P=0.019),right occipital lobe(P=0.005),and cerebellum(P=0.045)in ICA tortuosity group were lower than those in control group.There was no statistically significant difference in the relative volume of other brain regions between the two groups(P>0.05).The brain atrophy rates of left cingulate gyrus(P=0.013),right cingulate gyrus(P=0.007),left insula(P=0.031)and right insula(P=0.003)in ICA tortuosity group were higher than those in control group.There was no statistically significant difference in the atrophy rate of other brain regions between the two groups(P>0.05).The relative CBF of left thalamus(P=0.024),right thalamus(P=0.048)and deep white matter(P=0.020)in ICA tortuosity group were higher than those in control group when PLD was 1525 ms.There was no statistically significant difference in the relative CBF of other brain regions between the two groups(P>0.05).The relative CBF of left thalamus(P=0.002)in ICA tortuosity group was higher than that in control group when PLD was 2525 ms.There was no statistically significant difference in the relative CBF of other brain regions between the two groups(P>0.05).ICTI was negatively correlated with the relative volume of brain parenchyma(r=-0.214,P=0.021),gray matter(r=-0.245,P=0.008),left occipital lobe(r=-0.198,P=0.032),right occipital lobe(r=-0.281,P=0.002),and right temporal lobe(r=-0.317,P<0.001).ICTI was positively correlated with the rate of brain atrophy in the left insula(r=0.299,P=0.001),right insula(r=0.346,P<0.001),left cingulate gyrus(r=0.277,P=0.002),right cingulate gyrus(r=0.275,P=0.003)and right temporal lobe(r=0.239,P=0.009).Conclusion: The increase of the degree of internal carotid tortuosity is associated with the increase of white matter hyperintensity and enlarged perivascular space and the decrease of cognitive function,as well as associated with the reduction of gray matter volume in some brain regions and the increase of atrophy rate in bilateral cingulate gyrus and insula.The perfusion in each brain region of patients with internal carotid artery tortuosity is not significantly decreased. 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