The Application Of80KV Tube Voltage In Aortic CT Angiography

Purpose:Part one：To prospectively compare image quality and radiation dose inaortic computed tomography angiography (CTA) obtained with a protocol of120kV with automatic tube current modulation (ATCM) and another protocolof80kV with constant tube current.Part two：To prospectively compare image quality and radiation dose inaortic computed tomography angiography (CTA) by Adjusting tube currentwhich is adapted by body mass index,with80kV tube votage.To provide forindividual scanning solutions.Materials and Methods:The study had obtained institutional review board approval.146patientswho underwent aortic CTA were randomly divided into120kV group（120kV,z-axis ATCM, n=31) and80kV B (80kV,490mAs, n=31)partly.Thesignal-to-noise ratio, contrast-to-noise ratio, volume CT dose index andeffective dose were evaluated respectively. Subjective vessel contrast wasassessed by two radiologists in consensus. Results of both protocols werecompared using x2test and Student’s t test.The others divided into group A(80kV,BMI>25kg/m~2,490mAs, n=29) and group B (80kV,25>BMI>20kg/m~2,400mAs, n=37). Group Ｃ (80kV,BMI<20kg/m~2,300mAs,n=18) Results of the three protocols were compared using SPSS16.0toStatistical analysis.Results: The80kV protocol acquired a slightly, but not significantly, higher average signal intensity than the120kV protocol (372.1±74.7HU vs.368.9±78.8HU; P=0.87) and a slightly, but not significantly, lowersignal-to-noise ratio (34.3±9.0vs.36.3±9.1; P=0.39). The mean image CNRwas (30.7±8.3) and (29.0±8.6) for conventional tube kilovoltage and low tubekilovoltage respectively, there was no significant difference (0.44). Meaneffective dose for80kV protocol was significantly lower than that for the120kV protocol (9.7±0.8mSv vs.14.3±5.9mSv;-32.2%; P<0.001).The490mAs Scanning group、400mAs Scanning group and300mAsScanning group, there is no statistical differences of the SNR(P=0.687) and theCNR(P=0.749). Mean effective dose for the three group(490mAs Scanninggroup、400mAs Scanning group and300mAs Scanning group), there isstatistical differences （9.939±0.4280mSv vs7.794±0.5765mSv vs5.836±0.3663mSv; P=0.000）, The comparison between any two groups, P<0.05, all have statistical significance.Conclusion:The80kV protocol allows a significant reduction of radiation dose inaortic CTA, without significant change in signal-to-noise ratio,contrast-to-noise ratio and image quality compared with the120kV protocol.The400mAs protocol allows a significant reduction of radiation dose inaortic CTA, without significant change in signal-to-noise ratio,contrast-to-noise ratio and image quality by25>BMI>20kg/m~2.The300mAsprotocol allows a significant reduction of radiation dose in aortic CTA, withoutsignificant change in signal-to-noise ratio, contrast-to-noise ratio and imagequality by BMI<20kg/m~2.Reduce the tube current, direct reduces the photonenergy, but increased the value of contrast CT. We can reduce the radiationdoses according to the patient’s body mass index, at the same time, reduce the using of contrast agents, which decrease the patient’s radiation hazards and atthe same time,Save the costs.