Application of High-pitch CT Pulmonary Angiography at 70 kV Tube Voltage with 15 ml Contrast Medium Using Third-generation Dual-source CT.

Objective To assess the application of high-pitch CT pulmonary angiography (CTPA) at 70 kV tube voltage with 15 ml contrast medium using third-generation dual-source CT. Methods A total of 70 patients with clinically suspected pulmonary embolism were randomly divided into two groups: group A (n=35) underwent CTPA on conventional scanning mode (120 kV,80 ml contrast medium);and group B (n=35) underwent CTPA on high-pitch scanning mode at 70 kV tube voltage with 15 ml contrast medium. The CT values and standard deviations of the main pulmonary artery,apical segment of right upper pulmonary lobe (S1),and posterior basal segment of the right lower pulmonary lobe (S10),anterior thoracic air,and back muscles were measured. The signal to noise ratio (SNR),contrast to noise ratio (CNR),and effective dose (ED) were calculated. The overall image quality was evaluated by two blinded radiologists. The quality image was compared using non-parametric test on two independent samples. The potential differences in CT value,SNR,CNR,and ED were analyzed using the independent sample t-test. Results The CT values of main pulmonary artery [(300.62±77.54)HU vs.(332.80±102.80)HU;t=-1.53,P=0.13],S1 [(361.72±84.92)HU vs. (325.37±87.86)HU;t=1.81,P=0.08],and S10 [(359.54±89.61)HU vs. (318.26±87.19)HU;t=2.00,P=0.05] of right lung were not significantly different between group A and group B. The CNR of S1 (22.81±6.05 vs. 19.80±6.60;t=2.05,P=0.04) and S10 (22.65±6.37 vs. 19.28±6.63;t=2.23,P=0.03) of right lung in group A was significantly higher than in group B. The SNR of main pulmonary artery,S1,and S10 of right lung were not significantly different between group A and B. The subjective diagnostic quality values of group A and B were 1 (1,1) and 1 (1,1),respectively (Z=-0.08,P=0.93). The subjective diagnostic quality values evaluated by two radiologists showed excellent consistency(κ=0.87,P=0.01). The mean ED was 79% lower in group B [(0.92±0.23)mSv] than in group A [(4.33±1.80) mSv] (t=11.72,P=0.00).Conclusion Application of high-pitch mode in CTPA at 70 kV with 15 ml contrast medium using third-generation dual-source CT can remarkably reduce radiation dose without affecting image quality.