A new image-quality evaluation method for low-contrast resolution in computed tomography

Tsunemichi Akita; Naoyuki Yagi

doi:10.1117/12.710515

8 March 2007 A new image-quality evaluation method for low-contrast resolution in computed tomography

Tsunemichi Akita, Naoyuki Yagi

Author Affiliations +

Proceedings Volume 6515, Medical Imaging 2007: Image Perception, Observer Performance, and Technology Assessment; 65151O (2007) https://doi.org/10.1117/12.710515
Event: Medical Imaging, 2007, San Diego, CA, United States

Abstract

The contrast-to-noise ratio (CNR) is often used as a physical evaluation parameter for low-contrast resolution in computed tomography (CT). However, CNR is not affected by the window conditions. This study proposes a new physical evaluation method for low-contrast resolution that takes into account changes in window conditions. This new parameter is called the gray-scale contrast-to-noise ratio (GSCNR) was assessed and was compared with CNR. For each reconstruction image, the window width (WW) was varied from 100 to 400 in steps of 100 while keeping the window level (WL) fixed, and CNR and GSCNR were calculated. WL was then varied from 0 to 100 in steps of 20 while keeping WW fixed, and CNR and GSCNR were calculated again. CNR did not vary with WW, but it varied inversely with the standard deviation (SD) of the CT number (from 2.2 for an SD of 7 to 1.4 for an SD of 16). In contrast, GSCNR decreased with the increase in WW for each SD. In addition, GSCNR did not vary with WL, but it varied inversely with SD. GSCNR was found to be a useful physical evaluation parameter and was also thought to be useful for optimizing the window conditions.

Citation Download Citation

Tsunemichi Akita and Naoyuki Yagi "A new image-quality evaluation method for low-contrast resolution in computed tomography", Proc. SPIE 6515, Medical Imaging 2007: Image Perception, Observer Performance, and Technology Assessment, 65151O (8 March 2007); https://doi.org/10.1117/12.710515

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