The application value of 70 keV monoenergetic imaging on dual-layer spectral detector CT in improving contrast-enhanced abdominal image quality / 中华放射学杂志

ABSTRACT

Objective:To explore the value of 70 keV virtual monoenergetic images(VMI) on dual-layer spectral detector CT in improving abdominal arterial phase images quality.Methods:The arterial phase images of patients who underwent abdominal enhanced scan on the Philips IQon dual-layer spectral detector CT in Shengjing Hospital of China Medical University from January to May 2019 were retrospectively analyzed. Fifty patients (12 males, 38 females) were included with age of 26-74 （53±12） years. Objective and subjective evaluation was performed in 120 kVp polychromatic conventional images (group CI) which derived from iterative reconstruction algorithm and group 70 keV VMI which derived from spectral reconstruction algorithm. The attenuation, noise, signal to noise ratio and contrast to noise ratio of abdominal aorta, celiac trunk, superior mesenteric artery, left kidney artery, right kidney artery, liver, spleen, pancreas, left and right kidney were compared between group 70 keV VMI and CI by using paired t test. Image quality of group 70 keV VMI and CI was evaluated by two radiologists independently with a 5-point scale and compared by Wilcoxon rank test. The inter-agreement of subjective scoring between the two radiologists was evaluated by Kappa test. Results:Except for pancreas, the attenuation of abdominal arteries and solid organs in group 70 keV VMI were higher than that of group CI and the difference was statistically significant ( Pall<0.05). The attenuation of pancreas was lower than that of group CI ( t=-3.097， P=0.003). The noise of abdominal arteries and solid organs in group 70 keV VMI showed lower values compared to group CI and the difference was statistically significant ( Pall<0.001). The signal to noise ratio as well as contrast to noise ratio of abdominal arteries and solid organs in group 70 keV VMI was higher than that of group CI and the difference was statistically significant ( Pall<0.001). Subjective image quality scores in group 70 keV VMI were higher than that of group CI and scores of group 70 keV VMI and CI were 5 (4,5) and 4 (4,5), respectively. The difference was statistically significant ( Z=-4.131, P<0.001). There was a good consistency of subjective image quality scores between two radiologists, which Kappa values of group 70 keV VMI and CI were 0.79 and 0.69, respectively. Conclusions:Compared to CI, 70 keV VMI derived from dual-layer spectral detector CT can optimize abdominal arterial phase image quality by decreasing the noise, improving the signal to noise ratio and contrast to noise ratio.