The effects of low contrast agent concentration combined with optimal monochromatic energy image on myocardial dual energy image quality / 中华放射学杂志

ABSTRACT

Objective To investigate the effects of low contrast agent concentration and optimal monoenergetic image on myocardial image quality in dual source, dual energy coronary CT angiography (CCTA).Methods Sixty patients,who were clinically suspected of coronary heart disease and referred to perform dual energy CCTA examination,were prospectively collected between January and June 2016 in the first affiliated hospital of Xinjiang Medical University and then randomly divided into two groups with thirty cases in each group.Dual-energy CCTA was performed in both groups with the same parameters expect the iodine contrast agent concentration.The iopamidol concentrations were 370 and 320 mg/ml for groups A and B, respectively. The raw images of the two groups were reconstructed to get conventional mixed energy images and 60,65,70,75,80,85,90 keV single energy images,respectively labeled as group A1 to A8 and group B1 to B8.The CT attenuation,noise,signal-to-noise ratio(SNR)and contrast to noise ratio(CNR)were measured in images from groups A1 to A8 and B1 to B8. And the optimal monoenergetic image set was selected.Rank sum test was used to compare the CT value,noise,SNR and CNR between groups A1 to A8 and B1 to B8.The differences of above-mentioned parameters between A1 and B5 group,A5 group and B5 group were compared by independent sample t test.Results The differences of CT value,noise,SNR and CNR between groups A1 and A8, B1 and B8 were statistically significant (P<0.05). The CNR and SNR of group A5 were significantly higher than that of group A1,and the image noise of group A5 was lower than that of group A1(all P<0.05),and the images of A5 group(75 keV)were the optimal monoenergetic image. The SNR and CNR of the left ventricular lateral wall in group B5 were significantly higher than those in group B1,and the noise was lower than that in group B1(all P<0.05),and the image of B5 group(75 keV) was the optimal monoenergetic image. The difference of image noise between groups A1 and B5 was statistically significant(P<0.05),while the differences of SNR and CNR between these two groups were not significant(all P>0.05).The differences of image noise,SNR and CNR between groups A5 and B5 were not significant(all P>0.05).Conclusions The myocardial CCTA image quality by using iodine contrast agent (320 mg/ml) and optimal monoenergetic imaging (75 keV) is equivalent to that of conventional iodine contrast agent(370 mg/ml)mixed energy image.The strategy can effectively reduce the amount of contrast agent when meeting the needs of the clinical diagnosis.