Optimized Scan Protocol For Cerebral Perfusion And Recommended Relevant Scan Protocol By Using 3^rd Generation Dual-source CT:A Feasibility Study

Background and Objective: Acute ischemic stroke(AIS)is one of the main causes of death and disability around the world.However,intravenous thrombolysis plays an important role in the effective treatment and prognosis impovement of patients within 3 to 6 hours after the onset of illness.Whole brain computed tomography perfusion(CTP)imaging technology can quickly determine infarct area and ischemic penumbra,and can be used to assess the severity of cerebral ischemic lesions and predict whether the intervention can reduce the damage.However,the skull is scanned repeatedly in the whole brain CTP examination,the radiation dose couldn't be ignored.So how to reduce the scanning dose has become a research hotspot.With the update of CT equipment optimization of scan protocol and the radiation dose has been reduce in varying degrees,thereinto extending the time sampling interval was an important indicator in scanning dose reduction.The purpose of this study is to explore the application of different time sampling modes to reconstruct the collected images under the CTP scanning mode of the third generation dual source CT,to evaluate the influence of different time sampling modes on perfusion parameters and radiation dose of CTP,and to formulate an optimized scan protocol in order to optimize a scan protocol for clinical diagnosis requirements and recommend the scan protocol.Methods:(1)47 consecutive subjects who underwent cerebral CTP in our hospital from November 2016 to June 2017 were collected,who were 19 subjects with AIS and 28 subjects with AIS symptoms but no lesions on CT or CTP.CTP parameters were respectively quantificationally calculated for four groups according to different time sampling modes on time attenuation curve(TAC): 3s scan interval,(Group 1,standard control group),3s scan interval(Group 2),3s interval in pre-ascending and pro-descending while 1.5s interval in the intermediate period(Group 3),between the peak of artery and vein was 1.5s interval and rest was 3s interval(Group 4).Image reconstruction was performed according to different time sampling modes.Then subjective analysis was performed and radiation dose was statistical calculated respectively.(2)The situation of the examiners as before,the time points of four time sampling modes were recorded,including the ascending and descending points of TAC curve and the peak of arterial and venous TAC curve.According to the statistical results of the above four groups of time sampling methods,the group with the best results was selected.According to the group,two recommended protocols were set up and the perfusion parameters and radiation dose were compared with the standard control group.Results:(1)Ten regions of interest(ROIs)were placed in the ischemic area and contralateral brain parenchyma of each patient in AIS group and non-AIS group,and the total number of data points of perfusion parameters were 190 and 280,respectively.There were significant differences in BF,BV and MTT between AIS group and non-AIS group(P all < 0.01).Inter-group analysis showed that Group 3 and Group 1 had non-significant difference in all the perfusion parameters(P all >0.01)in both AIS group and non-AIS group.Bland-Altman analysis showed that Group 3 and Group1 had good consistency in AIS group and non-AIS group.What's more,compared with Group1(standard control group),Group 3 had the best subjective score and the lower radiation dose.(2)Based on the time sampling mode of Group 3,two recommended protocol were established and verified,the perfusion parameters of AIS patients and non-AIS patients had good correlated with standard control group(P all < 0.01),and the radiation dose was all reduced.Conclusion: The scanning protocol which sampling as 3s interval in pre-ascending and pro-descending period while 1.5s interval in the intermedium period,had good agreement with the standard scanning mode and apparently reduced the radiation dose.It might have the potential to be an optimized cerebral CTP scan protocol for the clinical settings.And according to the actual situation of patients to choose the demarcation point of pre-ascending and pro-descending period can achieve individual scanning of patients,better reduce radiation dose.