Hyeongmin Jin, Presenter: Nothing to Disclose

Jong Hyo Kim PhD, Abstract Co-Author: Nothing to Disclose

The emphysema index (EI) in CT is a quantitative measure of emphysema, which is known to be affected by reconstruction kernel. This study presents an image-based kernel conversion technique which converts CT image of sharp kernel to that of standard kernel and compares the result with MTF-based kernel conversion method in the measurement of EI.

Sixty cases of CT exams obtained with 120kVp, 40mAs, 1mm thickness, of 2 reconstruction kernels (B30f, B50f) were selected from the low dose lung cancer screening database of our institution. An image-based kernel conversion technique, which converts by applying a conversion function, was performed to the CT data set of B50f to create a converted B30f data set. The conversion function(Fcon) which is the ratio of the spectral components of target and source kernel images, was produced using a training dataset. Fcon in the MTF-based method, was the ratio of MTFs which were measured with small bead object in 2 reconstructed images. The EI (RA950) was measured with a software package (Pulmonalyzer, Seoul, South Korea) and compared for data sets of B50f, B30f, and the converted B30f. The accuracy of kernel conversion was evaluated with the mean and standard deviation of pair-wise differences in EI.

Population mean of EI was 28.89±6.48% for B50f data set, 10.96±6.37% for the B30f data set, and 11.27±6.83% for the converted B30f data set. The pair-wise differences in EI between B30f and the converted B30f is 0.78±1.07% with image-based method, and 4.91±1.73% with MTF-based method.

Our study demonstrates the feasibility of image-based kernel conversion method for normalization of kernel effect in measurement of EI with superior performance to that of MTF based approach. This technique has a potential to be used in evaluating the longitudinal changes of EI even when the CT was reconstructed with different kernels.

http://abstract.rsna.org/uploads/2014/14017586/14017586_pkee.jpg

Jin, H, Kim, J, Normalization of the Reconstruction Kernel Effects with Image-based Kernel Conversion Technique in the Measurement of Emphysema Index in CT.  Radiological Society of North America 2014 Scientific Assembly and Annual Meeting, - ,Chicago IL. http://archive.rsna.org/2014/14017586.html