The influence of pulmonary artery diameter on the image quality of dual-layer spectral detector CT pulmonary angiography with low contrast agent dosage / 中华放射医学与防护杂志

ABSTRACT

Objective:Evaluate the image quality of dual-layer spectral detector CT pulmonary angiography with low-dose contrast agents, and explore the influence of pulmonary artery diameter on the image quality.Methods:A total of 91 spectral CT pulmonary angiography from March 2022 to August 2022 were retrospectively analyzed. The cases were divided into Group 1 ( n=34, main pulmonary artery diameter ≥ 30 mm) and Group 2 ( n=57, main pulmonary artery diameter<30 mm). The dosage of contrast agent was 30 ml. The CT attenuation values(CT values), standard deviation(SD), signal-to-noise ratio(SNR), and contrast-to-noise ratio(CNR) values of pulmonary artery from the main trunk to the subsegmental pulmonary artery between two groups were compared. The CT dose index volume(CTDI vol) and dose-length production (DLP) were recorded. Two readers evaluated the image quality using three-point method. The inter-reader agreement was performed by Kappa test. Results:The CT values of the pulmonary trunk and left pulmonary artery between two groups was not significantly different ( P>0.05). The CT values of the left upper lobe artery, segmental artery, and subsegmental artery in Group 1 were lower than those in Group 2 ( t=-2.13, -2.17, Z=-2.33, P<0.05). The SD values of pulmonary trunk and segmental artery in Group 1 were higher than those in Group 2 ( t=2.27, Z=-2.23, P<0.05). The SD values of left pulmonary artery, left upper lobe artery, and subsegmental artery between two groups were not significantly different ( P>0.05). The SNR and CNR values of main pulmonary trunk, left pulmonary artery, left superior lobar artery, and segmental artery in Group 2 were higher than those in Group 1 ( Z=-2.45, -2.57, -2.09, -3.58, P<0.05; Z =-2.33, -2.42, -2.07, -3.45, P<0.05), while these values of the subsegmental artery between two groups were not significantly different ( P>0.05). The two readers had good consistency in evaluating image quality (Kappa value>0.75, P<0.05). Conclusions:Spectral CT pulmonary angiography with 30 ml contrast agent would generate good quality images. However, the distal pulmonary artery would be poorly revealed when the diameter of main pulmonary artery more than 30 mm, especially in patients with suspected pulmonary hypertension.