Abstract:Objective To investigate the effects of Karl iterative reconstruction algorithm on intrapulmonary vascular volume
(IPVV) quantification and chest CT image quality under low-dose and ultra-low dose scanning. Methods A total of 58 patients who
underwent chest CT examination were prospectively collected and scanned with low-dose CT (120 kV, 40 mAs) and ultra-low dose
CT (120 kV, 3-4 mAs) respectively. Low-dose CT was reconstructed by filtered back projection (FBP), and ultra-low dose CT was
reconstructed by FBP and Karl-3D iteration, with reconstruction levels of 1, 5, and 9 (Karl1, Karl5, Karl9), respectively, the radiation
dose was recorded. The region of interest (ROI) of the pulmonary artery was placed at the level of bronchial bifurcation in the chest
CT image, and the image noise was measured. IPVV of the whole lung was obtained by automatic extraction of intrapulmonary
blood vessels using pulmonary vascular measurement tools. The differences of quantitative indicators, radiation dose and image
noise among the groups were compared, and the correlation between IPVV measurements in the ultra-low dose group and the low
dose group was explored. Results The volume CT dose index (CTDIvol) of low-dose CT was (3.18±0.16) mGy, the dose length
product (DLP) was (121.53±9.37) mGy·cm, the effective dose (ED) was (1.70±0.13) mSv, the CTDIvol of ultra-low dose
CT was (0.25±0.16) mGy, the DLP was (9.51±0.68) mGy·cm, and the ED was (0.13±0.01) mSv. The results of quantitative
measurement of ultra-low dose CT images were positively correlated with those of low-dose CT images, which were FBP (r=0.947,
P<0.001), Karl1 (r=0.947, P<0.001), Karl5 (r=0.944, P<0.001) and Karl9 (r=0.939, P<0.001). The absolute underestimation of
the ultra-low dose CT image reconstructed by FBP to IPVV was 0.098%. The absolute underestimation of Karl1, Karl5 and Karl9
was 0.10%, 0.13% and 0.17%, respectively. With the increase of IR level, the image noise decreased obviously and the quantitative
measurement of IPVV decreased gradually (P<0.001). Conclusion When the effective radiation dose is reduced by about 92%, the
Karl-3D iterative reconstruction algorithm can significantly reduce the image noise and improve the image quality. However, ultralow
dose chest CT will underestimate the quantitative detection of IPVV, so the iterative reconstruction algorithm of Karl-3D can not
improve the accuracy of pulmonary vascular detection.
袁若涵,黄晓旗,阴玮灵,李延静. 超低剂量条件下Karl迭代算法对肺血管定量评估及胸部CT图像质量的影响[J]. 中国医疗设备, 2022, 37(10): 65-68.
YUAN Ruohan, HUANG Xiaoqi, YIN Weiling, LI Yanjing. Influence of Karl Iterative Algorithm on Quantitative Assessment of Pulmonary Vessels and
Image Quality of Chest CT Under Ultra-Low Dose Conditions. China Medical Devices, 2022, 37(10): 65-68.