Clinical Application Of Dual-source CT Angiography On Carotid Artery

[Objective]1,To investigate the clinical applications of dual energy subtract angiography with automatic bone-removal technique on carotid artery using dual- source CT.2,To investigate the the evaluation of dual-source CT angiography(DSCTA) on the location, the nature of carotid atheromatous plaque and the stenosis of involved carotid artery.3,To compare and evaluate the concordance between dual-source CT angiography with ultrasongraphy(US) in detecting carotid atherosclerotic plaques and assessment of stenosis.[Material and Methods]1,Clinical data65 patients suspected of cervical vascular diseases from Feb.2010 to Dec.2010 were performed cervical DECT angiography with dual- source CT(DSCT). Among them,38 were male,27 were female, age range 16-80 years old with mean age 55 years.Among above patients,42 patients with high risk of atherosclerotic carotid artery(25 male,17 female; mean age 62.83 years; age range 45-80 years) were selected for the evaluation of carotid atheromatous plaque. The inclusion criteria as following:①age≥45 years;②hypertension or hyperlipemia;①cerbral infarction; ④TIA or cataplexy;⑤DM. The first one item and one of the latter 4 items were selected into this study.15 patients with high risk of atherosclerotic carotid artery(9 male,6 female; mean age 64 years; age range 54-79 years) who underwent DSCT angiography and ultrasongraphy examinations within a week were selected from the above cases.6 of them underwent digital subtraction angiography(DSA) examinations simultaneously.2,DSCT scan protocolAll the patients were performed with DSCT scanner(SOMATOM Definition, Siemens Medical Solutions, Forchheim, Germany). A dual-energy protocol was used with both tube A (140kV,56mAs) and tubeB (80kV,234mAs), with 2×64×0.6-mm collimation, pitch 0.6-1, rotation time of 0.33 s, FOV 19cm.All the patients were fixed with a head supporter. After plain scan the DECT angiography scan was started by continuously injecting a bolus of 50-65ml ultravist(concentration:370mgI/ml), followed by 40ml saline solution into an antecubital vein via a 18-gauge catheter(injection rate 4.0-5.5ml/s) with high-pressure double-barrel syringe(MEDRAD, America). Contrast scan was controlled by bolus tracking. Region of interest(ROI) was placed into the aortic arch, and image acquisition was started 2s after the attenuation of ROI reached the predefined threshold of 100HU. The scan was performed in caudo-cranial direction from the aortic arch to the base of skull, and the images were reconstructed with 0.75mm slice thickness and 0.5mm increment by a smooth D30f Siemens kernel. The average scan time was 6s.3,DSCTA image post-processing and analysisAfter examination, two individual stacks of images for each detector (80kV and 140kV images) and DE mixed images were reconstructed(M-0.3); All images were transferred to an offline workstation, which was equipped with a dedicated DE analysis software package (Syngo CT Workplace, Version syngo CT 2008G, SiemensHealthcare) and advanced semi-automatic vessel analysis software(InSpace, Siemens Healthcare). Two datasets of 140kV and 80kV were input simultaneously into the dual-energy software, the automatic bone-removal technique was then used to complete the bone removal. The subtracted images were further processed using maximum intensity projection(MIP) and volume rendering(VR) in order to observe the courser and affection of carotid artery.The reconstruction image data of M-0.3 was load in advanced semi-automatic vessel analysis software (Inspace, Siemens Healthcare. Multiplanar reformation (MPR), maximum intensity projection (MIP), volume rendering (VR) were applied to observe the carotid artery.4,Date measurement and acquisition4.1 Score of image qualityThe carotid artery was divided three sections for the evaluation of image auality: collar section, extracranial section, and basalis section. Image quality was measured on a four-point scale:3 points, only vascular structures were visible without any artifacts, such as residual bone; 2 points, some bone remnants or other artifacts were visible without disturbing the free view of the vascular structures; 1 point, large bone remnants or other artifacts remained, which influenced diagnosis; 0 points, the vascular structures were invisible and its continuity was poor. The 2-3 points were considered diagnostically satisfied.4.2 Section of carotid arteryThe carotid artery was divided into four parts:the origins of common carotid(the origins of brachiocephalic trunk),the common carotid artery,the bifurcation of the carotid artery,the extracranial vessel of the internal carotid artery. The origins of common carotid was regarded as the intersection of 2cm or less between the common carotid and aortic arch, the bifurcation of the carotid artery represented the horizontal distance between the internal carotid artery and the lowest point of the intersection of carotid artery angle.4.3 Classification of plaqueThe three groups consisted of different types of plaque composition, while parts with a density of less than 50 HU were classified as fatty plaques, mixed plaques (50-119 HU) and calcified plaques (>120 HU).4.4 Measurement of stenosis rateAccording to the standard of NASCET, stenoses were additionally quantified using the "Vessel Analysis" of InSpace. The blood vessel diameter of affection, area of residual lumina(area A), blood vessel diameter and area of lumina of further normal vessel (area B)were computed automatically. The stenosis rate was computed automatically according to the formula:stenosis rate%=. (area B-area A)×100/area B. A scoring system was used for grading:no stenosis, mild(0-29%), moderate(29%-69%), severe(70%-99%) and occlusion.5, Statistics analysisAll the data was processed with SPSS 13.0 statistical package.5.1 R×C Chi-square test was used to evaluate primitive score of estimated functional vessels, P<0.05 was considered statistical significant difference.5.2 The number of plaques(both sides), the nature and number of plaques(both sides) and the carotid artery stenosis(both sides) were compared with Chi-square test. The statistically significant difference was set at P<0.05.5.3 Different location and total number of plaques were compared with K Related Samples test, the statistically significant difference was set at P<0.05.5.4 The plaques of cerbral infarction and hypertension and the relation of cerbral infarction and carotid artery stenosis were compared with Chi-square test, the statistically significant difference was set at P<0.05.5.5 Statistical delineation was used for disposition and nature of plaques. The Kappa statistics was used to compare the difference of DSCTA and US in detecting plaques and stenosis (kappa<0.4=poor,0.4-0.7=good,0.7-1=very good). P<0.05 was considered statistical significant difference.[Results]一,The clinical applications of dual energy subtract angiography on carotid artery using dual-source CT1,Vessels and affection displayOf 65 cases,3 cases were normal variation; 33 cases were no obvious affection; 32 cases with atherosclerotic carotid artery, of which 4 were carotid stent implantation.2,Evaluation of image qualityRatio of diagnostically satisfied corotid arteries on DECT angiography for collar section, extracranial section, basalis section were 67.2%,96.2%,66.2%, respectively. Statistically significant difference (χ2=142.293, P=0.000) existed among three sections in Chi-square test, and there is no significant difference between collar section and basalis section of corotid (x2=4.878, P=0.181>0.05).二,Clinical application of carotid artherosclerosis by DSCT angiography1,The location of plaquesOf 42 patients with high risk of atherosclerotic carotid artery, atheromatous plaques were detected in 32 (76.2%,91 places).39 plaques located in the bifurcation of the carotid artery,23 in the extracranial vessel of the internal carotid artery,22 in the common carotid artery, and7 in the initial part of the carotid artery.24 cases had multiple atheromatous plaques.2,The nature of plaques Of 91 plaques,60 places(65.9%) were calcified,12 places(13.2%) were soft, and 19 places(20.9%) exhibited a combined nature of both calcified and soft plaque.1 case who underwent carotid endarterectomy(CEA) was proved as mixed atherosclerotic plaques in carotid artery by pathology.3,The degree of stenosisOf 91 places plaques, no stenosis was showed in 52 places, accounting for 57.1%. The other 39 places lead to stenosis, accounting for 42.9%. Among them,15 places mild(16.5%),8 places moderate(8.8%),8 places severe(8.8%) and 8 places(8.8%) with occlusion. The examination results of CTA in 8 of the 10 cases were in accordance with DSA, the stenosis rate diagnosed by CTA was slightly higher in 2 cases as compared with the results of DSA.三,The comparison between DSCT angiography and US in the evaluation of carotid artherosclerosis1,Location of plaquesAll the 15 patients were detected carotid atherosclerotic plaque, DSCTA and US separately detected 46 and 44 plaques; of which 42 places were common. The total concordance was 87.5%(42/48).2,Nature of plaquesDSCTA detected 32 places as calcified plaques,8 places soft plaques,6 places mixed places. US detected 24 places as calcified plaques,13 places soft plaques,7 places mixed places. Identical nature was 27 places, the total agreement in detecting the nature of plaques was 64.29%(27/42). The agreement between DSCTA and US in detecting atheromatous plaques was common and existed a statistically significance, with the value of Kappa 0.417, P=0.000.3,Stenosis degreeCarotid stenosis was detected by both methods in 21 places, with the overall agreement 67.74%(21/31). The agreement between DSCTA and US in detecting the degree of carotid stenosis was common and existed a statistically significance, with the value of Kappa 0.577, P=0.000. Compared with DSA,3 carotid occlusions were diagnosed correctly by CTA, but 2 diagnosed correctly by US, other 1 underestimated as severe grade stenosis,1 cannot be detected, but blood flow rate(BFR) was slow obviously.[Conclusions]1,Dual-energy CTA with bone-removal was a rapid, convenient and non-invasive method. The overall bone subtraction effect was good, even in the skull base and the transverse process of cervical vertebra. The carotid artery were best displayed in the extracranial section(CCA and the extracranial section of ICA), with the satisfied display rate 96.2%; then the collar section (67.2%), but the basalis section only 66.2%.2,The patient preparation before scanning, stopping moving during the scanning, injection parameters and modality of contrast agent, and correct selection of scan parameters were the premise for obtaining the high quality carotid artery image. With multiple application of post processing techniques, we can diagnose cervical vascular affection precisely.3,Carotid atheromatous plaques were mostly located in the bifurcation of the carotid artery, accounting for 42.9%; the next extracranial vessel of the internal carotid artery(25.3%), then the common carotid artery(24.2%), the origins of common carotid artery was less(7.7%). The nature was mainly calcified plaques, accounting for 65.9%, soft plaques less happened(13.2%).4,In general, carotid atheromatous plaques cannot caused stenosis(57.1%), or only mild(16.5%); Severe stenosis usually happened in the extracranial vessel of the internal carotid artery. 5,Dual-source CT angiography can be used to clearly determine the location, number, nature of carotid atheromatous plaques, and stenosis of the involved carotid artery. It can make an accurate diagnosis and evaluation of carotid atherosclerosis, and provide the basis for individualized treatment of clinical.6,There were fine agreement between DSCTA and US in detecting the location, nature of carotid atherosclerosis plaques and stenosis of the involved carotid artery. The sensitivity of DSCT in detecting calcified plaques was higher, relatively. Both DSCTA and US were feasible in a routine examination of carotid stenosis screening,.