The Practical Value Of Optimal Contrast Noise Ratio In The Post-Processing Of Spectral CT Angiography Images

1. Selection of an Optimal keV single-energy image during the Post-Processing of Lower Extremity Peripheral Arterial CT Angiography using Dual-energy CT scannerObjective:To evaluate the practical value of optimal contrast to noise ratio (CNR) in the post-processing of CTA imagesMethods:96patients diagnosed with peripheral arterial disease (PAD) were selected. The patients were scanned using a dual-energy CT. The images were reconstructed using gemstone spectral imaging (GSI)-viewer, and select an ideal keV single-energy image based on an optimal CNR. The contrast and noise were measured for each segment using the images obtained with the quality check (QC), default keV, and optimal keV settings. The qualities of the MIP image, MPR image, and the QC, default keV, and optimal keV transverse images were scored by two radiologists.Results:The score of the optimal keV image in MIP image(13.58±0.87) was significantly higher than that of the QC image(7.83±1.07) and default keV image(11.67±0.95)(p<0.05). The optimal keV image had significantly higher contrast of each segments compared with the QC image and with the default keV images(p<0.05).Conclusion:By selecting an optimal keV image based on an optimal CNR, the optimal contrast of the lower extremity peripheral artery and the surrounding tissue was obtained, and the arteries was clearly displayed, thus greatly improving the image quality. 2. The selection of monochromatic images in the post process of hepatic arterial CT angiology before TACE.Objective:To investigate the value of using optimal contrast to noise ratio to select one optimal keV monochromatic images to improve image quality of hepatic arterial CT angiology.Methods:96patients with peripheral arterial disease were underwent spectral CT examination from October2011to October2012. There were62males and34females with ages ranging from51to62years (mean age of57.61years). Using GE ADW4.4and GSI view software to post process the images and measure optimal CNR in transverse image to select an optimal keV monochromatic images. Measure contrast and noise of proper hepatic artery and the right hepatic artery in QC images, predefine keV monochromatic images selected by system and monochromatic images select by using optimal contrast to noise ratio. Two radiologists major in abdominal and vascular radiology evaluate those images using score1-5. Statistical analysis was carried out using the Stata version10.0software. P<0.05is defined as statistical significance.Results:The score, contrast and noise of monochromatic images select by using optimal contrast to noise ratio is significantly higher than other two methods, and those of monochromatic images selected by system is significantly higher than QC images (P<0.05).Conclusions:Using optimal contrast to noise ratio to select one keV monochromatic images set will enhance contrast between hepatic arteries and surrounding tissue, make arteries more visible and improve image quality of hepatic arterial CT angiology.