| Part 1 Dual source CT angiography with low kVp and low volume of isotonic contrast material for head and neck arteries:preliminary studyObjective:To evaluate the image quality and radiation dose of craniocervical CT angiography(CTA)using low tube voltage and low volune of isotonic contrast material.Methods:A total of sixty patients who underwent craniocervical CTA were assigned into 2 groups:gorup A(double low-dose group,30 cases)wth 80/Snl40 kVp,sinogram-affirmed iterative reconstruction(SAFIRE)and 32ml of 270 mgI/ml contrast material,and group B(conventional group,30 cases)with 100/Snl40 kVp,filtered back-projection reconstruction(FBP)and 40ml of 370 mgl/ml contrast material.Attenuation values were measured from the center of specific arterial segments using regions of interest.The CT attenuation effective dose(ED),image noise,signal-to-noise ratio(SNR)and contrast-to-noise ratio(CNR)of each arterial segment were compared between the two protocols using the Student t test.Qualitative analysis between the protocols was also performed,Results:Both groups of CTA achieved comparable CT attenuation,image noise,SNR and CNR in each arterial segment(each P<0.01),except for the image noise of ascending aorta.Using the double low-dose mode,the ED was reduced by about 23.8%(t=-9.316,P<0.001),and iodine intake of patients in double low dose group A was reduced by 41.6%(8.6g versus 14.8g).There was no significant difference in image quality between the two groups(z=-0.129,P=0.898).The consistency between the two observers was good(kappa value=0.663,P<0.001).Conclusion:In craniocervical dual source CTA,using low tube voltage and and low volume of isotonic contrast material not only provided images of diagnostic quality but also reduced both radiation dose and iodine intake during scanning.Part 2 Personalized double-low dose cervico-cerebral CTA based on test bonus scanning:a self-controlled Case-series evaluationObjective:To compare the image quality,radiation dose and iodine load of cervico-cerebral CTA in the same group of patients.Methods:a total of 23 patients were enrolled in this study.All patients first underwent conventional cervico-cerebral CTA examination(protocol B),with tube voltage of 100/140Sn kVp,as well as low-osmolar contrast media(CM)370mgl/ml,with volume of 40ml and injection rate of 5ml/s.After a period of time,the same patients accepted a second cervico-cerebral CTA(protocol A),for which a personalized protocol was selected,with tube voltage of 80/140Sn kVp,as well as isotonic-osmolar CM 270mgl/ml,with different volume of 20-42 ml and injection rate of 4.0-6 ml/s,according to the dynamic curve of test bolus injection.The image quality,effective radiation dose and iodine intake were compared between the two groups.Results:the subjective score of image quality were 3.86±0.39 and 3.90±0.35 for protocol A and B,respectively(z?-1.729,P=0.084).The scores determined by two radiologists were found to be consistent(kappa=0.642).Compared with protocol B,the dose-length product(DLP)and effective dose(ED)of protocol A decreased by 26.2%and 23.8%,respectively(P<0.001),with iodine intake decreased 43.8%.The mean intraluminal attenuation and contrast enhancement in protocol A were also less than protocol B(P>0.05).There was no significant difference of SNR and CNR between the two protocols(all P>0.05).Conelusion:Use of dual-source CT with a "double low",scanning protocol and a personalized injection program for cervico-cerebral CTA not only provided images of diagnostic quality but also reduced both radiation dose and iodine intake during scanning.Part 3 Dual source double-low dose CTA using a test bolus of diluted iso-osmolar iodinated contrast material for craniocervical arteries:a preliminary studyObjectives:To evaluate a personalized protocol with a test bolus of diluted contrast material(CM)for craniocervical double-low dose computed tomography angiography(CTA).Methods:Eighty nine patients with suspected craniocervical artery disease underwent dual source CTA.In group A(diluted CM protocol,n=59),the optimal scan timing and the volume and injection rate of CM were determined by the timing bolus scan of diluted CM.A personalized protocol of iso-osmolar CM(270mgl/ml)was use for real CTA,with CM volume of 20-36ml,and injection rate of 4-6ml/s for different sub-groups.The injection rate and volume in the timing bolus scan and real scan were or nearly were identical.In group B(conventional CM protocol,n=30),only the optimal scan timing was determined by the timing bolus scan.Patients received intravenous administration of CM(370 mgl/ml)at a dose of 40ml and injection rate of 5 mL/s.Both protocols used a dual source CT,the former with 80/Snl40 kVp and the latter with 100/140SnkVp.Attenuation values were measured from the center of specific arterial segments using regions of interest.Attenuation values above 250 HU were accepted as significant.The CT attenuation,dose-length product,effective dose(ED),image noise,signal-to-noise ratio(SNR)and contrast-to-noise ratio(CNR)of each arterial segments were compared among the two and sub-groups using the analysis of t test or variance.Two experienced radiologists independently evaluated the image quality with 4-point scores,and interrater reliability was calculated using iK analysis.Results:The dose-length product and ED of group A were lower than those of group B(each P<0.01),with decreases of 28.3%and 28.6%respectively.The iodine intake in group A(average 9.7g)was decreased by approximately 47.6%than group B(each 18.5g),while one sub-group(7g)decreased by 62.2%at most.Group A had a significant decrease of CT values for the distal part of common carotid artery,the proximal part of internal carotid artery and segment M1 of the medial cerebral artery(all P<0.01),while there was no significant difference for segment ascending aorta and vertebral artery division(V4)(P>0.05).For the distal part of common carotid artery and the proximal part of internal carotid artery,group B had higher SNR and CNR than group A(each P<0.05),while no significant difference for other segments(P>0.05).No significant differences were found for the mean image quality score between groups A and B(3.62±0.55 vs.3.65±0.51)(z=-0.003,P=0.998).The inter-observer agreement for image quality grading of the craniocervical artery segments was excellent(kappa=0.845).Conclusion:Craniocervical double-low dose CTA using dual source CT with a test bolus of diluted CM can be successfully obtained.The optimal scan timing,the volume and injection rate of CM were determined by the timing bolus scan of diluted CM.For this personized double-low dose protocol,it can not only provide images of diagnostic quality but also reduce both radiation dose and iodine intake during scanning. |
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