Experiment on the impact of low tube voltage on imaging quality and radiation dose in abdominal multi-detector CT

Objective To investigate the impact of low tube voltage with 80 kV on imaging quality and radiation dose in abdominal CT.Methods A phantom containing low-contrast objects was scanned with a 16-section multi-detector CT scanner at 80 and 120 kV,with tube current-time product settings at 150—650 mA.The image noise(SD,standard deviation of CT number),contrast-to-noise ratio(CNR) and CT doses index volume(CTDIvol) were objectively measured.To assess low-contrast detectability(LCD),subjective assessment of the visibility was performed by 2 independent observers.The relationship between CNR and CTDIvol was analyzed.The differences between image noise,CNR and scores of LCD obtained with 80 kV at 150—650 mA and those obtained with 120 kV at 300 mA were compared.Results There was direct correlation between CNR and CTDIvol.With identical dose,using of 80 kV tube voltage resulted in higher CNR compared with CNR at 120 kV.Although the image noise substantially increased with low tube voltage(80 kV),there was no statistical difference between CNR and scores of LCD obtained with 120 kV at 300 mA and those obtained with 80 kV at 550—650 mA(P0.05).Conclusion With a reduction of the tube voltage from 120 kV to 80 kV,the amount of reduction in the radiation dose can be achieved mostly by 42.23% without degradation of CNR and LCD.