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.
ABSTRACT
Objective:To evaluate the image quality of dual-source computed tomography pulmonary angiography (DE-CTPA) with low-dose contrast agent using the advanced modeled iterative reconstruction (ADMIRE) method with 70 kVp and non-linear blending in overweight patients.Methods:Seventy patients (normal BMI, 35; overweight, 35) with suspected pulmonary embolization who underwent DE-CTPA between October 2018 and March 2019 were included in this study. The imaging protocol included assessments at 70 kV/sn150 kV with 30 ml of contrast agent, and images were obtained at 70 kVp and 150 kVp with and without linear blending. The CT value, SD value, signal-to-noise ratio (SNR), and contrast-to-noise ratio (CNR) of pulmonary arteries were compared and analyzed among groups 1 (70 kVp, normal BMI), 2 (non-linear blending, normal BMI), 3 (70 kVp, overweight), and group 4 (non-linear blending, overweight). The radiation dose parameters included CT volume dose index (CTDI vol), dose length product (DLP), and effective dose ( E). Results:The CT values for the pulmonary artery did not show significant differences among the four groups ( P>0.05). The SD value of the segmental artery in group 1 was higher than that in group 4 ( t=2.69, P<0.05). The SNR values of the pulmonary artery trunk and sub-segmental artery in group 2 were higher than those in group 3 ( t=1.44, 5.40, P<0.05), while the corresponding value of the left pulmonary artery trunk in group 2 was higher than those in groups 3 and 4 ( t=1.52, 1.52, P<0.05). The CNR values of the pulmonary artery trunk and sub-segmental artery in group 2 were higher than those in group 3 ( t=1.45, 5.01, P<0.05) and that of the left pulmonary artery trunk in group 2 was higher than those in groups 3 and 4 ( t=1.50, 1.50, P<0.05). The E values for normal BMI and overweight patients were(1.60±0.54)mSv and(1.88±0.45)mSv, respectively. Conclusions:For overweight patients, the CTPA protocol using ADMIRE with a 70 kV/sn150 kV scanning mode could yield diagnostic image quality with significantly lower radiation and contrast material doses.
ABSTRACT
Purpose To quantitatively evaluate the ability of advanced virtual monoenergetic technique (monoplus) in improving the display of pulmonary arteries with dual-source CT dual-energy pulmonary angiography.Materials and Methods Thirty patients whose CT values in pulmonary artery and its branches were lower than 300 HU in mixed images while image quality was poor in distal branches were enrolled in this study.All these patients underwent dual-source dual-energy (100/Sn140 kVp) CT pulmonary angiography (CTPA) with small amount of contrast medium (30 ml) from September 2016 to December 2016.Non-linear blending images were assigned in group A,100 kVp images from one tube were assigned in group B,and optimized monoenergetic images with low keV monoplus (40+,50+,60+ keV) were assigned in group C,D and E,respectively.CT and SD values of segmental,subsegmental and distal branches were measured,and signal noise ratio (SNR) and contrast noise ratio (CNR) were calculated.Results Among all the 5 groups,CT values of pulmonary artery in group C,D and E were significantly higher than in group A and B (P＜0.05).SNR values of segmental artery in group C were significantly higher than those in group A (P＜0.05).SNR values of subsegmental artery in group C and D were significantly higher than those in group A (P＜0.05).SNR values of segmental and subsegmental pulmonary artery in group C,D and E were all significantly higher than those in group B (P＜0.05).The SNR values of distal branches in group C,D and E were not significantly different from those in group A (P＞0.05),but were significantly higher than those in group B (P＜0.05).CNR values in group C,D and E were not significantly different from those in group A (P＞0.05),but were significantly higher than those in group B (P＜0.05).Conclusion Combined with dual-source dual-energy CT pulmonary angiography,low keV monoplus images can effectively increase CT values of pulmonary artery and clearly display the distal branches.Meanwhile,the image quality is comparable with non-linear blending images,better than that of low tube voltage (100 kVp) images.