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Objective:To investigate the feasibility of reducing radiation dose in coronary CT angiography for patients with arrhythmia with absolute phase and narrow window in prospective electrocardiogram-gating.Methods:200 patients with arrhythmia underwent coronary CT angiography procedure with prospective electrocardiogram-gating adaptive sequence in dual source CT were randomly divided into 2 groups according to the scan mode. Group A was scanned with absolute phase and narrow window(250-450 ms) and group B uesd relative phase and wide window (30%-75%). The other parameters and injection protocol of contrast media were the same in 2 groups. Both image quality and radiation dose of the 2 groups were analyzed.Results:No significant difference of image quality was found between the 2 groups. CTDI vol, DLP, E of group A were all lower than those in group B [CTDI vol : (16.71±8.35) vs.(29.35±17.90)mGy , DLP: (231.04±114.86) vs.(398.27±238.40)mGy·cm , E: (3.23±1.60) vs.(5.57±3.33)mSv, t=-6.40, -6.32、-6.32, P<0.05] . The patients with repeat scan cycles in group A and group B were 81 vs. 22 for 0 cycle , 17 vs. 62 for 1 cycle, 2 vs. 10 for 2 cycles, 0 vs. 6 for 3 cycles( χ2=70.76, P<0.05). Conclusions:The prospective electrocardiogram-gating adaptive CCTA sequence with absolute phase and narrow window can reduce radiation dose while the image quality meets the requirementsfor patients with arrhythmia.
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Purpose To investigate the feasibility of 30 ml low-dose contrast medium in reducing the accumulation of contrast medium in venous system while maintaining enough artery enhancement in 256-slice CT angiography (CTA) of intracranial and cervical arteries.Materials and Methods Sixty patients with head and neck CTA were recruited prospectively,and they were randomly divided into group A and group B.The scan parameters of the two groups were identical,but the protocol of contrast medium injection was different.Group A was injected 60 ml contrast medium and 30 ml saline successively with the rate of 4.0 ml/s.Group B was injected 30 ml contrast medium and 50 ml saline successively with the rate of 5.0 ml/s.CT attenuation values of aortic arch,common carotid artery,subclavian artery,cerebral middle artery,superior vena cava,innominate vein,subclavian vein,internal jugular vein were measured,and the image quality was evaluated.Results The average CT values of superior vena cava,right innominate vein,right subclavian vein in two groups had significant differences (P＜0.05).The average CT values of left brachial vein,left subclavian vein,left and right internal jugular vein in two groups had no significant differences (P＞0.05).The average CT values of aortic arch,left and right common carotid artery,left and right subclavian artery,left and right cerebral middle artery in two groups had significant differences (P＜0.05).The scores of image quality in two groups also had significant difference (P＜0.05).Conclusion Head-and-neck CTA with 30 ml low-dose contrast medium is feasible and the images are satisfactory for diagnosis,which can reduce the dose of contrast medium and accumulation of contrast medium in venous system,while maintaining enough artery enhancement.