| Background:Carotid atheromatous plaque formation,calcification,carotid stenosis is one of the leading causes of cerebral ischemia,cerebral infarction,and at the same time,according to carotid intima stripped,carotid stenting preoperative and postoperative evaluation and follow-up,the carotid artery CTA examination has largely replaced the traditional DSA examination,because of its rapid,economic and noninvasive.But the high-dose human body damage,high concentration of contrast agent and image of venous pollution has attracted attention,at the same time executive voltage will lead to a series of radiation risk;X-ray has three effects when they interact with a nucleus:photoelectric effect,Compton scattering effect,and the electron pair effect,when the tube voltage 80 kv the Compton effect is equal to the proportion of the photoelecrtric effect,this can reduce the radiation dose at the same time,to ensure the quality of imaging and combining with the physical properties of iodine,lower tube voltage can not only reduce the radiation dose,and can make blood vessels containing iodine or other organizations to increase the probability of the photoelectric effect,improve the degree of the strengthening of the target vessels,increase blood vessels enhanced CT value,based on the above X rays,and iodine physical properties become double low technology theoretical basis.Isotonic concentration and low volume contrast agent can reduce the risk of renal toxicity of contrast agent.Therefore,the dosage and concentration of contrast agent should be reduced as much as possible in the carotid CTA examination,and the radiation risk caused by tube voltage should be reduced.Objective:To investigate fesibility research of carotid CTA using low dose technology(30ml ultra-low contrast volume,270mgI/ml isotonic concentration contrast media and 80kv low tube voltage).Methods:A total of 60 patients whose BMI value was controlled in the range of 20-26 were selected to complete the examination on 128-layer dual source CT(Definition FLASH,Siemens Medical Solutions,Germany).The patients were randomly assigned to two groups,30 cases in each group,respectively the conventional control group and the double-low experimental group.Scan range of autonomic aortic arch to the level of the canthus.In the ascending aorta,ROI was set at 10s,the trigger threshold was 100Hu,the delay time was 4s,FOV 20x20cm,the acquisition matrix was 512x512,the bulb speed was 0.28s/coil,the collimator width was 0.6mm,the reconstruction image thickness was 0.75mm,the layer distance was 0.6mm,and B20.The contrast agent was injected with a double-barrelled high-pressure syringe through an 18G indwelling needle in the median elbow vein.Flash scanning mode was adopted in the double-low experimental group:single bulb 1*64 layer,screw pitch 2.1,tube voltage 80kv,tube current automatic regulation technology(CareDose4D),contrast agent 30ml Iodixanol(Iodixanol,270mgI/ml,GE Healthcare),physiological saline 40ml,injection speed 4.5ml/s,self-adaptive statistical iterative reconsltruction(SAFIRE=3)post-processing algorithm.Scanning mode of conventional control group:1*64 layers of single-bulb tube,screw pitch 1.0,tube voltage 120kv,contrast agent 60ml Iopromide(370mgI/ml,Bayer Schering),physiological saline 40ml,injection speed 4.5ml/s,image conventional BMP(anti-filtering reconstruction technology)reconstruction.The scanning data were sent to the Siemens post-processing station(syngo-via)for vascular MIP image(maximum density projection)multi-plane reconstruction(MPR),curved surface reconstruction(CPR)and volume reconstruction(VR)images.The entire experimental process was reconstructed according to the standard operating procedures and parameters to ensure the consistency of data collection and post-processing images.The image quality between the two groups was compared,including subjective and objective evaluation.The objective image quality included the measurement of the CT value of vessels in each segment of the carotid artery,the observation of the enhancement degree of the arterial segment,the calculation of the image contrast noise ratio CNR value,and the comparison of the radiation dose of DLP,CTDIvol and effective dose of ED in both groups.Finally,the iodine intake of the two groups was calculated.The values of gender,age,height,weight and BMI between the two groups were analyzed by t test.The sex ratio was tested by Chi-Square test.The CT values of blood vessels in each segment were expressed as mean ±SD(Hu).The differences between the groups were compared by t test,the contrast noise ratio(CNR)values of the two groups were analyzed by t test,and the subjective scores were analyzed by Wilcoxon rank sum test.The radiation doses were analyzed by t test.Results:Clinic conditions of patients in the two groups:there was no significant difference in age,height and bmi,with p value(p=0.19,p=0.94,p=0.50,p=0.66),and no significant difference in gender ratio(p=0.8).The CT values of all vascular segments of the two groups were all above 300Hu,meeting the diagnostic requirements.The CT values of the dual-low experimental group were higher than the control group.Dosage of the conventional control and dual-low experimental groups:DLP(cm)of the two groups were 396.2156.4mGycm,69.2±3.1mGycm respectively;CTDIvol was 13.2±2.2 mGy and 1.9±O.1mGy;ED was 11.8± 1.4mSv and 2.1±0.3mSv respectively.Compared with control group,DLP,CTDIvol,ED values of the dual-low experimental group were reduced by 85.6%.,82.5%,82.2%The total iodine intake amount was reduced by 63.5%.For the image quality,the contrast noise rate(CNR)value of control group was higher than the dual-low group(91.8±8.1vs69.6±6.3,p=0.045),but the subjective scores showed no obvious differences(3.5±0.2vs3.7±0.1,p=0.59)which doesn't settle for clinical diagnosis.Conclusion:The dual-low dosage technology(ultra-low volume low concentration contrast,and low tube voltage)can provide satisfactory images,meanwhile the radiation dosage can be significantly reduced,moreover the iodine intake amount is decreased greatly.This technique is an ideal safer option for carotid CTA,especially for patients with renal dysfunction. |
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