Mammographic density measurements are not affected by mammography system

Abstract

Abstract. Mammographic density (MD) is a significant risk factor for breast cancer and has been shown to reduce the sensitivity of mammography screening. Knowledge of a woman's density can be used to predict her risk of developing breast cancer and personalize her imaging pathway. However, measurement of breast density has proven to be troublesome with wide variations in density recorded using radiologists' visual Breast Imaging Reporting and Data System (BIRADS). Several automated methods for assessing breast density have been proposed, each with their own source of measurement error. The use of differing mammographic imaging systems further complicates MD measurement, especially for the same women imaged over time. The purpose of this study was to investigate whether having a mammogram on differing manufacturer's equipment affects a woman's MD measurement. Raw mammographic images were acquired on two mammography imaging systems (General Electric and Hologic) one year apart and processed using VolparaDensity™ to obtain the Volpara Density Grade (VDG) and average volumetric breast density percentage (AvBD%). Visual BIRADS scores were also obtained from 20 expert readers. BIRADS scores for both systems showed strong positive correlation (ρ ¼ 0.904; p < 0.001), while the VDG (ρ ¼ 0.978; p < 0.001) and AvBD% (ρ ¼ 0.973; p < 0.001) showed stronger positive correlations. Substantial agreement was shown between the systems for BIRADS (κ ¼ 0.692; p < 0.001), however, the systems demonstrated an almost perfect agreement for VDG (κ ¼ 0.933; p < 0.001).

Inter‐observer variability in mammographic density assessment using Royal Australian and New Zealand College of Radiologists (RANZCR) synoptic scales

“…The current analysis was conducted using images previously used with radiologists based in America using the BI‐RADS scale . That study by our group found a higher, moderate, inter‐reader agreement (κ = 0.57) for USA based American board of Radiology certified radiologists.…”

Mammographic density assessed on paired raw and processed digital images and on paired screen-film and digital images across three mammography systems

“…Although such methods eliminate between-reader variations in readings, many only work on a single image type (often raw digital images [25]), but others can be applied across multiple types [8, 26]. It is possible that there would be between-system differences in automated measures, particularly volumetric measures due to differences in breast positioning and therefore breast thickness [27], but not all studies have found this [28]. In the future, as further processing algorithms are developed, MD differences between raw and processed images are likely not only to persist but also to change.…”

Consistency of visual assessments of mammographic breast density from vendor-specific “for presentation” images

“…However, the mean and median time between images was 7.1 and 4 weeks, respectively, and it is unlikely that the PD of the women in this study would have perceptibly and significantly changed during this short amount of time. 7,25,26 Furthermore, it is possible that changes in positioning technique could affect the observed density between the Siemens and Hologic images for a given woman; however, such differences are unlikely to be systematic based on screening or diagnostic imaging status.…”

“…6 Differences in vendor-specific image acquisition technology can result in images from some vendors having a wider range of pixel intensities and darker appearance in fatty regions and brighter appearance in dense tissue regions compared to other vendors even when variations in positioning are minimized. 7 The resulting differences in display may affect perception of the amount and distribution of breast tissue and, therefore, the visual assessment of PD. As such, vendor-specific differences in the appearance of the "for presentation" mammography images routinely reviewed in clinical care may contribute to the unreliability of visual assessments of PD, particularly in cases when data are pooled across multiple sites.…”

“…7,11,12 The commercially available algorithms used in these research studies analyze "for processing" images that are not for clinical use and are not routinely stored in picture archiving communication systems. While such algorithms aim to generate density assessments that agree with radiologists' visual assessments of density, the manner in which radiologists visually process "for presentation" images is a complex visual perception task that is fundamentally different from the varied algorithmic approaches implemented in automated software solutions.…”