A nonparametric measure of contrast in x-ray images
Autor(in); Institution
Anton, Mathias; 6.2, Dosimetrie für Strahlentherapie und Röntgendiagnostik, PTB-Braunschweig
Reginatto, Marcel; 6.2, Dosimetrie für Strahlentherapie und Röntgendiagnostik, PTB-Braunschweig
Schopphoven, S.; Reference Centre for Mammography Screening Southwest Germany, Giessen, GERMANY
Abou-Jaoude, C.; Reference Centre for Mammography Screening Southwest Germany, Giessen, GERMANY
Mäder, U.; Institute of Medical Physics and Radiation Protection, University of Applied Sciences, Giessen, GERMANY
Fiebich, M.; Institute of Medical Physics and Radiation Protection, University of Applied Sciences, Giessen, GERMANY
Mauter, Franziska; 6.2, Dosimetrie für Strahlentherapie und Röntgendiagnostik, PTB-Braunschweig; Radboud University Medical Center, Nijmegen, THE NETHERLANDS
Sechopoulos, I.; Radboud University Medical Center, Nijmegen, THE NETHERLANDS; LRCB Dutch Expert Centre for Screening, Nijmegen, THE NETHERLANDS
van Engen, R.; LRCB Dutch Expert Centre for Screening, Nijmegen, THE NETHERLANDS
Quelle/Jahr
Physics in Medicine and Biology: 69
(2024), 15, 1
- 19
Objective: We propose a nonparametric figure of merit, the contrast equivalent
distance CED, to measure contrast directly from clinical images.
Approach: A relative brightness distance δ is calculated by making use of the order statistic of the pixel values. By multiplying δ with the grey value range R, the mean brightness distance MBD is obtained. From the MBD, the CED and the distance-to-noise ratio DNR can be derived. The latter is the ratio of the MBD and a previously suggested nonparametric measure τ for the noise.
Since the order statistic is independent of the spatial arrangement of the pixel
values, the measures can be obtained directly from clinical images. We apply the new measures to mammography images of an anthropomorphic phantom and of a phantom with a step wedge as well as to CT images of a head phantom.
Main results: For low-noise images of a step wedge, the MBD is equivalent to the
conventional grey value distance. While this measure permits the evaluation of clinical images, it is sensitive to noise. Therefore, noise has to be quantified at the same time. When the ratio σ/τ of the noise standard deviation σ to τ is available, validity limits for the CED as a measure of contrast can be established. The new figures of merit can be calculated for entire images as well as on regions of interest (ROI) with an edge length not smaller than 32 px.
Significance: The new figures of merit are suited to quantify the quality of clinical
images without relying on the assumption of a linear, shift-invariant system. They can be used for any kind of greyscale image, provided the ratio σ/τ can be estimated. This will hopefully help to achieve the optimisation of image quality vs dose required by radioprotection laws.
Kostenfreier Zugang
Open Access Hybrid
Rechteinformation
CC BY 4.0 ; Creative Commons Attribution 4.0 License
Zitierung
Anton, M., Reginatto, M., Schopphoven, S., Abou-Jaoude, C., Mäder, U., Fiebich, M., Mauter, F., Sechopoulos, I., & van Engen, R. (2024). A nonparametric measure of contrast in x-ray images. Physics in Medicine and Biology, 69(15), 1–19. https://doi.org/10.1088/1361-6560/ad6119
