Comparing Different Algorithms for the Pseudo-Coloring of Myocardial Perfusion Single-Photon Emission Computed Tomography Images

Abstract

Single-photon emission computed tomography (SPECT) images can significantly help physicians in diagnosing patients with coronary artery or suspected coronary artery diseases. However, these images are grayscale with qualities that are not readily visible. The objective of this study was to evaluate the effectiveness of different pseudo-coloring algorithms of myocardial perfusion SPECT images. Data were collected using a Siemens Symbia T2 dual-head SPECT/computed tomography (CT) scanner. After pseudo-coloring, the images were assessed both qualitatively and quantitatively. The qualities of different pseudo-color images were examined by three experts, while the images were evaluated quantitatively by obtaining indices such as mean squared error (MSE), peak signal-to-noise ratio (PSNR), normalized color difference (NCD), and structure similarity index metric (SSIM). The qualitative evaluation demonstrated that the warm color map (WCM), followed by the jet color map, outperformed the remaining algorithms in terms of revealing the non-visible qualities of the images. Furthermore, the quantitative evaluation results demonstrated that the WCM had the highest PSNR and SSIM but the lowest MSE. Overall, the WCM could outperform the other color maps both qualitatively and quantitatively. The novelty of this study includes comparing different pseudo-coloring methods to improve the quality of myocardial perfusion SPECT images and utilizing our collected datasets.

Relationships between colorization and pseudo-colorization of monochrome images

“…with more examples of color map equations available in [1,15]. It can be observed that the color map equations define parametric curves within the RGB unit cube.…”

“…Figs. 15 and 16 illustratively summarize the results of converting pseudo-colorized versions of two previously discussed exemplary images into their fully-colorized variants, using four different color maps.…”

“…The key challenge lies in selecting or designing this mapping function to achieve specific goals, such as enhancing visual appeal, improving content perception, or facilitating the visual analysis of objects or processes within the image, e.g. [9,12,15,20].…”

“…There are a number of standard color maps, commonly referred to as hot, warm, rainbow, springtime, jet, sine, etc. (see [1,15,17]). Examples are given in Figs.…”