Abstract： Objective To detect the image quality of dual-energy CT angiography(CTA) of head and neck arteries with low tube voltage,high pitch and iterative reconstruction(IR) using photon detectors,compared with conventional detectors.Methods CTA of the head and neck arteries was performed on 50 consecutive patients with suspected or previously diagnosed arterial diseases of head and neck.Patients were randomized to one of two groups using stellar photon detectors(Group A,n=24) or conventional detectors (Group B,n=26).CTA was performed with two 128-slice dual source CT systems with photon detectors and conventional detectors,respectively.Dual-enery low tube voltage settings were 140 kVp/80 kVp in tube A/B,and a high pitch of 1.2.All acquisitions were reconstructed with IR,1.0 mm thickness,DE composition=0.6.CTDIvol(CT dose index volume) and DLP(dose-length product) were recorded.Effective dose(ED) was calculated.Quantitative measurements were performed on each IR sequence(140kVp,80kVp and mixed energy) of 1.00 mm enhanced MPR(multi planar reformations) images as follows:(1) on the level of aortic artery(AA),the largest anteroposterior diameter of chest(R 1AP),CT attenuation values and standard deviation (SD) of AA; (2) on the level of common carotid artery(CCA) bifurcation,the largest auteroposterior and leftright diameter(R2AP,R2LR),CT attenuation values and SD of CCA,sternocleidomastoid muscle(SCM),ventral air of the neck on the contralateral side of contrast injection; (3) on the level of the clinoid segment of internal carotid artery(C5),the largest anteroposterior and left-right diameter(R3AP,R3LR),CT attenuation values and SD of C5 and brain stem.CNR of AA,CCA and C5 calculated as CNR.Qualitative assessments for each IR images were based on:noise of brain parenchyma,sharpness of subarachnoid space margins,grey matter-white matter differentiation and the visualization of middle cerebral arteries.t test,Wilcoxon nonparametric test and Mann-Whitney U test were used to compare the difference between the two groups.Results There was no significant difference in ED between group A and B(t=0.93,P=0.35),CTDIvol was higher in Group A(3.85 ±0.17) mGy,compared with Group B(3.74±0.18) mGy(t=2.17,P=0.03).The SD of AA and CCA of 140 kVp IR images of Group A[(25.8±4.3),(17.7±7.4) HU] were higher than that of Group B [(22.8 ± 3.6),(13.6 ± 5.7) HU].The difference indicated statistical significance(t=2.73,P=0.01 ; t=2.24,P=0.03).The SD of brain stem of 140 kVp IR,80 kVp IR and mixed-energy IR image of Group A were(17.1± 2.6),21.0(19.4,22.7) and 14.8(13.4,16.4) HU,and were lower than that of Group B(18.7±2.3),24.8(21.6,26.8),16.6(14.9,18.5) HU.The difference indicated statistical significance(t=-2.30,P=0.03;Z=-3.18,P=0.01 ;Z=-2.34,P=0.02).There was no significant difference in qualitative assessments of each IR images between the two groups(P＞0.05).Conclusions Stellar photon detectors results in lower noise of brain stem and dose not increase effective dose in low-tube-voltage and high-pitch DE CTA of head and neck,with IR reconstraction method,compared with conventional detectors.