Line Contrast Figure of Merit for Dual Energy X-ray Image Quality Assessment: Initial Results
Various Figures of Merits (FoMs) are used in order to evaluate the quality of x-ray images. A new Figure of Merit (FoM) is presented, which is based on analysis of data extracted from line profiles within the image. This FoM is referred as Line Contrast (
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Department of Medical Physics, School of Medicine, University of Patras, 26500, Rio, Greece
Abstract— Various Figures of Merits (FoMs) are used in order to evaluate the quality of x-ray images. A new Figure of Merit (FoM) is presented, which is based on analysis of data extracted from line profiles within the image. This FoM is referred as Line Contrast (LC). In order to evaluate its performance, the proposed FoM along with Contrast to Noise Ratio (CNR) and Contrast Michelson are applied in simulated Brain CT images and the resulting FoM values are compared. Brain CT images are created using the XRAYImagingSimulator, an in-house developed software platform for x-ray imaging simulation. A 3D brain phantom especially modified for x-ray imaging that contains volumes of gray, white, skull and cerebrospinal fluid was used. Presented Dual Energy CT images were produced with the low/high energy combination of 100/110 keV monochromatic beams. All images were evaluated using CNR, Contrast Michelson and LC FoM, both with and without the simulated presence of noise. Initial results from the application of FoMs show that LC comes into full accordance with visual assessment and that it overpasses the traditionally used CNR and Contrast Michelson. Initial results are presented here, while further studies on the evaluation of the proposed FoM are in progress. Keywords— Figures of Merit, Dual Energy, Image Evaluation, X-Ray imaging, Simulation
I. INTRODUCTION
Figures of Merit (FoMs) are used in order to evaluate the quality of a produced image. There are broadly used in imaging research and imaging techniques optimization due to the fact that they provide means to quantitatively evaluate the quality of the produced results and compare them using an objective measurement unit. Throughout the years many different FoMs have been proposed with the most broadly used being the Contrast to Noise Ratio (CNR), Signal to Noise Ratio (SNR), Contrast Michelson. In the case of CT and Dual Energy (DE) CT imaging, as in all x-ray imaging modalities, it is generally acknowledged that the image quality is better assessed using CNR and SNR, as in the case of digital mammography [1]. Although these FoMs can provide a good mean to evaluate the images, the value they provide when they are applied to an image does not always come in accordance with the visual investigation and may also fail to detect and evaluate the contrast between differ© Springer Nature Singapore Pte Ltd. 2018 H. Eskola et al. (eds.), EMBEC & NBC 2017, IFMBE Proceedings 65, DOI: 10.1007/978-981-10-5122-7_148
ent tissues that are present in the imaged area. Especially in the case of investigation of novel imaging techniques where a great number of images are produced, a FoM that consistently provides a quantitative measurement unit that comes in accordance with visual observation is of great importance. Such was the case of investigation of discrimination between gray and white matter using DE CT imaging [2,3] presented in this study, where more and 260K images were produced. Si
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