Preliminary Experimental Study On Volume Shuttle Mode Normal Cerebral Perfusion

PartⅠ Consistency of cerebral perfusion measurement experimentalstudy with Volume Helical Shuttle modeObjective:To evaluate consistency of the cerebral hemodynamiccharacteristic in normal rabbits by CT perfusion(CTP) imaging with VolumeHelical Shuttle(VHS) mode.Methods:10healthy rabbits were performed with CTP scans using VHSmode. The images derived from CTP examinations were analyzed by tworadiologists(A and B) with different experiences, who had been trained tooperate the post-processing software.30days latter, one of the radiologistswith less experience analyzed the CTP perfusion images again with the samemethods above. ROIs were placed in the basal ganglia, measuring each sidethree times, calculating the average,both sides of the basal ganglia weremeasured. The CBV, CBF and MTT values were computed. Paired-t test wasused to evalute the difference of perfusion values on both sides of the basalganglia. Differences of observation results were analyzed betweenintraobserver and interobserver using analysis of variance(ANOVA) for eachperfusion parameters, while using intraclass correlation coefficient (ICC) andBland-Altman method for analysis of consistency between intraobserver andinterobserver.Results:Three post-processing observations to the perfusion parameterson both sides of basal ganglia are no significant difference(P>0.05).Themeasurement of CBV values are3.35±0.07ml/100g,3.34±0.07ml/100g,3.39±0.08ml/100g,F=0.162,P>0.05;CBF values are52.32±0.87ml/min/100g,52.74±0.86ml/min/100g,52.59±1.09ml/min/100g,F=0.05,P>0.05; MTT are4.06±0.07s,4.11±0.06s,4.15±0.07s, F=0.488,P>0.05.The intraobserver ICC measurement of CBV,CBF and MTT were0.84,0.81,0.79;while interobserverICC measurement of CBV,CBF and MTT were0.80,0.89,0.84. All of the ICCswere above0.75,it demonstrates a good consistency in the measurement ofCBV,CBF,MTT both intraobserver and interobserver.Conclusion:The consistency of CTP with VHS mode at interobserverand interobserver is good,and it is suitable for the hemodynamics study ofanimal models in brain tumors or vascular disease.It provides a theoreticalbasis for quantitative study of CTP stably. PartⅡ Experimental study: influence of tube voltage on brain CTperfusion values and radiation doseObjective:To investigate the influence of tube voltage on brain CTperfusion values and radiation dose using128layer spiral CT.Methods:10cases of2months healthy New Zealand white rabbits.Wholebrain CTP were performed twice using VHS mode for each rabbit with tubevoltage80kV and120kV respectively.The interval of the two scans is morethan48hours. Cerebral blood volume(CBV), cerebral blood flow (CBF),mean transit time(MTT) on both sides of the basal ganglia weremeasured.Using paired-t test to compare the differences of perfusion valuesbetween both sides of the basal ganglia and between the different tubevoltage.To evaluate the perfusion image quality subjectively and record theradiation doses of each rabbit in different tube voltages.Results:There is no significant statsitical difference between both sidesof the basal ganglia perfusion values (P>0.05).CBV, CBF and MTT valueswith80kV were about3.34±0.32ml/100g,52.84±3.89ml/min/100g,4.13±0.26s; and CBV, CBF and MTT value with120kV were respectively4.06±0.36ml/100g,60.83±3.69ml/min/100g,4.10±0.23s.The MTT values has no difference between different tube voltages,t=0.726,P>0.05,while the CBVand CBF values have significant difference between different tubevoltages,t=0.000,P<0.05.The image qualitity are almost same with differenttube voltages.Average CTDlvol of80kV is146.73mGy and DLP is1304.44mGy mGy·cm while average CTDlvol of120kV is411.81mGy and DLP is3743.24mGy cm. Radiation doses with80kV reduced about64.4%inCTDlvol than120kV,and reduced about65.2%in DLP.Conclusion：Lower tube voltage results in a reduction of CBF and CBVvalue, so we should pay much more attention to the influence of the tubevoltage while analysis the cerebral hemodynamic changes quantitatively.Theradiation doses reduced greatly with the reduce of tube voltage, and the imagequality has no clear differences, therefore,it advocates the CTP with lowertube voltage.