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Method of measuring NEQ as a quality control metric for digital mammography
Author(s) -
Bloomquist Aili K.,
Mainprize James G.,
Mawdsley Gordon E.,
Yaffe Martin J.
Publication year - 2014
Publication title -
medical physics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.473
H-Index - 180
eISSN - 2473-4209
pISSN - 0094-2405
DOI - 10.1118/1.4865175
Subject(s) - imaging phantom , mammography , image quality , digital mammography , optical transfer function , noise (video) , reproducibility , quality assurance , computer science , medical physics , optics , computer vision , mathematics , physics , medicine , image (mathematics) , statistics , external quality assessment , pathology , cancer , breast cancer
Purpose: Current quality control protocols for digital mammography rely on subjective assessments of image quality or simple measures that are not comparable between vendor platforms. The noise‐equivalent quanta (NEQ) can be expressed in units of image quanta (fluence) for the spatial frequency range of interest, enabling comparisons between systems and x‐ray spectra. The purpose of this work is to explore use of a simple phantom to measure the components of the noise‐equivalent quanta of digital mammography systems for use in routine quality control.Methods: A simple phantom is imaged on six mammography systems from different vendors. The phantom contains uniform regions for measurement of noise power spectrum (NPS), slanted edges for measurement of modulation transfer function (MTF), and objects of various thicknesses for measurement of contrast. Images were acquired at a range of dose levels on each system to examine how measurements scale with dose, and multiple images were taken at a single dose point to examine measurement reproducibility.Results: The phantom and measurement methods show good reproducibility, with average coefficient of variation values of less than or equal to 15% on all systems evaluated. Measured MTF and NPS values are comparable to other published results when the increase in scattered radiation generated by placing the phantom on the breast support is accounted for.Conclusions: Measurement of the parameters required to calculate NEQ from a single image of a simple phantom is practical, and shows promise as a method of evaluating image quality for routine quality control of digital mammography systems.