Conversion factors between human and automatic readouts of CDMAM phantom images of CR mammography systems

Abstract

In mammography screening, profound assessment of technical image quality is imperative. The European protocol for the quality control of the physical and technical aspects of mammography screening (EPQCM) suggests using an alternate fixed choice contrast-detail phantom-like CDMAM. For the evaluation of technical image quality, human or automated readouts can be used. For automatic evaluation, a software (cdcom) is provided by EUREF. If the automated readout indicates unacceptable image quality, additional human readout may be performed overriding the automated readout. As the latter systematically results in higher image quality ratings, conversion factors between both methods are regularly applied. Since most image quality issues with mammography systems arise within CR systems, an assessment restricted to CR systems with data from the Austrian Reference Center in the mammography screening program has been conducted. Forty-five CR systems were evaluated. Human readouts were performed with a randomisation software to avoid bias due to learning effects. Additional automatic evaluation allowed for the computation of conversion factors between human and automatic readouts. These factors were substantially lower compared to those suggested by EUREF, namely 1.21 compared to 1.62 (EUREF UK method) and 1.42 (EUREF EU method) for 0.1 mm, and 1.40 compared to 1.83 (EUREF UK) and 1.73 (EUREF EU) for 0.25 mm structure size, respectively. Using either of these factors to adjust patient dose in order to comply with image quality requirements results in differences in the dose increase of up to 90%. This necessitates a consensus on their proper application and limits the validity of the assessment methods. Clear criteria for CR systems based on appropriate studies should be promoted.

Digital radiography image quality evaluation using various phantoms and software

“…However, IQ scores obtained using software may not be the same with the scores obtained from visual observation. As in the case of the CDMAM phantom, which is used for many years for the evaluation of IQ in mammography, conversion factors may be required to convert software scores to visual observer scores 15,16,17 . Due to this reason, a direct comparison between software IQ scores and visual IQ scores was avoided.…”

“…As in the case of the CDMAM phantom, which is used for many years for the evaluation of IQ in mammography, conversion factors may be required to convert software scores to visual observer scores. 15,16,17 Due to this reason, a direct comparison between software IQ scores and visual IQ scores was avoided. Furthermore, it should be also noted that in order to calculate an average score with the CDMAM phantom, it is required to acquire 8-16 images with the phantom slightly moved between acquisitions, because the relative position of the phantom's details (gold disks) and the dexels may affect the results.…”

Analysis of the threshold image contrast obtained with the CDMAM 3.4 and CDMAM 4.0 phantoms

“…Each of the phantoms allows you to determine the threshold contrast of discs with a diameter of 0.10 mm, 0.25 mm, 0.50 mm, 1 mm, 2 mm. Discs of the same diameter allow contrast values to be compared using the CDMAM 3.4 and CDMAM 4.0 phantoms [13][14][15][16]17], as recommended by the European Reference Organization for Quality Assured Breast Screening and Diagnostic Services. 9 phantoms were used to analyze the comparison of CDMAM 4.0 phantom readings.…”

Image Quality Comparison between Digital Breast Tomosynthesis Images and 2D Mammographic Images Using the CDMAM Test Object

“…The fourth (shown in Figure 2 c) is the average psychometric detection probability (data points and fitted curves) for all images in relation to gold disk thickness, for disk diameters from 0.1 to 1 mm. More details about the software, the scoring procedure, and the theoretical background of the IQ evaluation with CDMAM can be found in the referenced literature [ 12 , 13 , 16 , 17 , 18 , 19 , 20 ].…”