The Application of Low Tube Voltage and Low Volume Contrast Agent Protocol in Aorta CTA

Objective: To evaluate the effect and its feasibility in clinical application of double-low technology(the low tube voltage and low volume contrast agent protocol) for aorta CT Angiography(CTA) on the image quality and radiation dose. Method: Totally 90 continuous patients with clinically suspected aortic lesion underwent aorta CT Angiography. They were randomly divided into two groups(control group and double low group) based on different scan protocol, prospectively. Control group included 45 patients using following parameters: tube voltage 120 kVP and contrast agent volume 1.5 mL/kg(consentration: 350 mg I/m L). Double low group included 45 patients using following parameters: tube voltage 100 kVP and contrast agent volume 1.0 mL/kg(consentration: 300 mg I/m L). Other scanning parameters were same and all subjects were used automatic tube current modulation(ATCM) technology and Smart prep technology. CT dose volume index(CTDIvol) and dose length product(DLP) in the CTA dose report were read and the dosage of contrast agent and its iodine contrast agent volume were recorded. Two associate chief radiologists evaluated the image quality and its contents consisted of the average CT values of the targeted vessels and background, image signal-to-noise ratio(SNR), contrast to noise ratio(CNR), the display and sharpness of aortic and its major branches. The clinical information, radiation dose, iodine contrast agent volume, objective and subjective assessment of image quality of these two groups were analyzed by independent t test. Results: The differences of sex, age and body mass index(BMI) of two groups were not statistically significant(P<0.05). The radiation dose and the volume of iodine received in double low group was significantly lower than that of control group, with significant statistic difference(P<0.05). The difference of subjective assessment score of image quality in two groups was not statistically significant(P>0.05). The average CT values of the aortic trunk and its major branches in two groups were higher than 300 HU, with no significant statistic difference(P>0.05). The differences of SNR and CNR in two groups were not statistically significant also(P>0.05). Although image noise in double low group was slightly higher than that of control group, there is no influence on clinical diagnosis. Conclusion: Aorta CT angiography using 100 kVP as tube voltage, contrast agent volume 1.0 mL/kg(consentration: 300 mg I/m L) and automatic tube current modulation(ATCM) technology was feasible, which can effectively reduce the radiation dose and the volume of iodine contrast agent and meet the needs of clinical diagnosis at the same time.