Head And Neck By Dual Energy Less Shadow Cta Quality Assessment And Clinical Applications

OBJECTIVE.Compare the image quality and radiation dose of traditional 64-slice spiral CTA with DS-CTA of cervical and cranial regions.Evaluate the effect of age, height,weight,body mass index(BMI) on contrast enhancement in head and neck CTA.MATERIALS.AND METHODS.We retrospectively analyzed two groups of patients undergoing 64-slice spiral CTA and DS-CTA examination of cervical and cranial regions:with different scan protocols.The DS-CTA dataset(groupA,N=30, M:F=16:14,mean age=54y) was obtained with 1.0mm axial thickness,0.6mm interval, 140/80 kVp,64/272 mA,0.6 pitch factor,80 mL of contrast medium.The CTA 64-slice spiral dataset(groupB,N=30,M:F=17:13;mean age=55y) was obtained with 0.6mm axial thickness,0.6mm interval,120 kVp,230mA,1.5pitch factor,60 mL of contrast medium.We compared image quality,vascular enhancement,noise and radiation dose.The attenuation values and SD values were measured on transverse images at 4 different vessels(the distal part of common carotid artery and adjacent vein in same axial image;the Mls and sigmoid sinus or confluences of sinus in same image) and two muscles(one in neck region presenting average soft tissue enhancement and one adjacent to shoulder joint presenting regions of great artifact).. RESULTS.DS-CTA was significantly better than 64-slice spiral CTA in noise of soft tissues no matter artifact was absent(P＜0.001) or not(P＜0.001).In cranial region the arterial enhancement and venous contamination were similar.DS-CTA had greater venous contamination in cervical region(P＜0.001),since the mean attenuation value of common carotid artery was still higher than jugular vein by 130 Hu,this was compensative and didn't affect the delineation and analysis of cervical arteries.The total DLP of DS-CTA was 745 mGy.cm,which was 29%greater than 64-slice spiral CTA(579 mGy·cm).Strong inverse correlations were seen between attenuation of common carotid arteries and weight(r=0.64),height(r=0.453),BMI(r=0.453) (P＜0.05 for all).CONCLUSION.DS-CTA had comparable image quality to 64 slice spiral CTA,and its scan dose was greater.Among the age,height,weight and BMI,weight is the main factor that effects on the contrast enhancement of the head and neck DS-CTA. OBJECTIVE.To evaluation the image quality of dual energy subtracted CTA (DESCTA),and assess the correlations beween the calcificaion and image quality. Investigated the stenosis agreement of DESCTA and magnectic resonace angiography (MRA).Compare DESCTA and DSA to detection and measurement of stenosis in head and neck arteries.MATERIALS AND METHODS.Forty nine patients with suspicious of head and neck artery atherosclerosis underwent dual energy CT scan,along with a 3D TOF-MRA(n=32) or DSA(n=20) examination 1 days to three months before or after CTA.CT scan was performed using dual source CT(Definition,Siemens Medical Solution,Forchheim,Germany).80 ml ultravist(370 mgI/ml,Bayer Schering) was used as contrast agent followed by 50ml saline flash at speed of 5ml/s.A maximum intensity(MIP) image was first automatically obtained through dual energy subtraction(Software,Siemens).Ratings were based on a 1-4 scale for the MIP image: 1 no diagnostic,2 partially diagnostic,3 diagnostic,4 excellent.Calcium volume and surrounding percentage were calculated.Stenosis of internal carotid arteries obtained from DESCTA,MRA,DSA was evaluated basing on North American Symptomatic Carotid Endarterectomy Trial(NASCET) criteria by consensus with 2 experienced radiologists.The consistency of DESCTA and MRA,DESCTA and DSA were tested with the Wilcoxon test.RESULTS.(1)The head and neck arteries were divided into 21 segments.Among them,the internal carotid arteries were divided into six anatomical segments according to Fischer(1938):cervical,petrous(C5),caverous(C4),clinoidal(C3), cerebral(C2) and ascending(C1) segment.Totally 846 vessel segments from 49 patients were calculated except total occlusive(n=26),stents(n=5) and aneurysm(n=4). The scorc 3 and 4 segments of DESCTA occupied 99.1%(838/846).(2) There is no significant correlation between the calcium volume(spearman test,P=0.453), surrounding;percentage(Pearson chi-square,P=0.090) and external cranial arteries (Spearman test,P＜0.05).There is a strong correlation between calcium volume and internal cranial arteries(Spearman test,P=0.007 ),while a moderately correlation between calcium surrounding percentage and internal cranial arteries (Pearson chi-square test,P=0.046).(3) The agreement of the calculated degrees of stenoses between DESCTA and MRA is 96.6%(486/503)(Wilcoxon test,P＜0.001). (4) Compared with DSA,the accuracy of DESCTA is 97.6%(361/370).DESCTA was 100%sensitive and 100%specific for the total occlusion.Using a 50%cutoff value for stenosis,DESCTA and DSA were in agreement in 99.2%,DESCTA was 95.5% sensitive and 99.4%specific,and the positive predictive value was 91.3%,the negative predictive value was 99.7%.Using a 70%cutoff value for stenosis,DESCTA and DSA were in agreement in 98.9%,DESCTA was 92.3%sensitive and 99.2% specific,and the positive predictive value was 80%,the negative predictive value was 99.7%.CONCLUSION.DESCTA with MIP image gives good detail assessment for head and neck arteries atherosclerosis.The calcium volume and surrouding percentage effect variously on the image quality.DESCTA has the same ability for diagnosis of stenosis of as DSA.However,there is significant difference between DESCTA and MRA for the severity of stenosis.