Quantitative mammography contrast threshold test tool

Abstract

Mammographic contrast is commonly evaluated by visualizing small objects of varying size or mass divided by projected area. These qualitative contrast determinations are commonly performed by imaging a phantom like the American College of Radiology accreditation phantom at clinical mammographic settings. However, this contrast assessment does not take into account the kVp of the machine. This work describes a quantitative mammography contrast threshold test tool which examines light object contrast on a uniform background for a contrast range of 0.32% to 1.38% at 25 kVp. For this mammography contrast threshold test tool, contrast is defined by delta I/I = loge (psi O/ psi b), where psi O is the target energy flux, and psi b is the background energy flux. Contrast threshold is defined as the lowest contrast value for which the objects are visible. Unlike traditional assessments of mammographic contrast, this measurement of contrast threshold is kVp corrected. The mammography contrast threshold test tool is constructed out of common plastics and provides a quantitative means of assessing contrast threshold for individual mammographic units and total mammographic systems.

The Design and Fabrication of a Full Field Quantitative Mammographic Phantom

“…The aim of using mass artefacts is to provide a measurement of the low-contrast sensitivity of the mammography systems, which is relevant to the detection of tumour masses (round blobs) within the breast. Scoring small objects of varying size is a commonly used method to evaluate contrast in mammography units [23] . The use of dark targets (air gaps of varying depths) on a uniform background (plastic) to measure image contrast has previously been used [18] .…”

“…In order to produce a light target on a uniform background, the target can be thicker than that of the background or the attenuation coefficient of the target can be greater than that of the background [23] . Tissue equivalent materials have been used to obtain information on image quality, dose and overall system performance.…”

Estudo semianalítico da qualidade de imagem e dose em mamografia

“…A análise dos limites de detecção de nódulos tem sido limitada, até o presente momento, pela ausência de dados experimentais de coeficientes de atenuação linear de tecidos mamários neoplásicos na faixa de energia da mamografia. Assim, as estimativas destes limites são escassas na literatura, sendo que os estudos experimentais realizados até o momento utilizam materiais equivalentes, simulando apenas objetos presentes em uma mama de composição média (Wagner e Frey 1995, Del Guerra et al 2002. De forma geral, os limites de detecção para nódulos obtidos teoricamente neste trabalho concordam com os estimativas experimentais apresentadas por Wagner e Frey (1995) e por Del Guerra et al (2002).…”

Evaluation of digital X-ray detectors for medical imaging applications

“…According to the European Guidelines for quality control in digital mammography, mammographic image quality is expressed in terms of threshold contrast visibility using clinical exposure settings (van Engen et al, 2006, Young et al, 2006a, Young et al, 2006b. The threshold contrast is defined as the lowest contrast value for which the objects are visible (Wagner and Frey, 1995). The contrast-detail mammography (CDMAM) phantom is commonly used for the contrast-detail analysis (Thomas et al, 2005).…”

“…The relationship between contrast and thickness is given by C(t)=100•(1-e -µt ) (%), where µ is the linear attenuation coefficient of gold (µ=0.145 µm -1 in this study). This relationship is extracted from the contrast equation ΔI/I=log e (ψ o /ψ b ) where ψ o is the target energy flux and ψ b is the background energy flux (Wagner and Frey, 1995). To determine the threshold gold thickness for a given disk diameter a psychometric curve is fitted to the data Thijssen, 1996 andVeldkamp et al, 2003):…”