Burton, AnyaByrnes, GrahamStone, JenniferTamimi, RullaHeine, JohnVachon, CelineOzmen, VahitPereira, AnaGarmendia, Maria LuisaScott, ChristopherHipwell, John H.Dickens, CarolineSchüz, JoachimAribal, Mustafa ErkinBertrand, KimberlyKwong, AvaGiles, Graham G.Hopper, JohnPérez Gómez, BeatrizPollán, MarinaTeo, Soo-HwangMariapun, ShivaaniTaib, Nur Aishah MohdLajous, MartínLopez-Riduara, RuyRice, MeganRomieu, IsabelleFlugelman, Anath ArzeeUrsin, GiskeQureshi, SameraMa, HuiyanLee, EunjungSirous, RezaSirous, MehriLee, Jong WonKim, JisunSalem, DorriaKamal, RashaHartman, MikaelMiao, HuiChia, Kee-SengNagata, ChisatoVinayak, SudhirNdumia, Rosevan Gils, Carla H.Wanders, Johanna O. P.Peplonska, BeataBukowska, AgnieszkaAllen, SteveVinnicombe, SarahMoss, SueChiarelli, Anna M.Linton, LindaMaskarinec, GertraudYaffe, Martin J.Boyd, Norman F.dos-Santos-Silva, IsabelMcCormack, Valerie A.2017-01-032016Burton, A., G. Byrnes, J. Stone, R. M. Tamimi, J. Heine, C. Vachon, V. Ozmen, et al. 2016. “Mammographic density assessed on paired raw and processed digital images and on paired screen-film and digital images across three mammography systems.” Breast Cancer Research : BCR 18 (1): 130. doi:10.1186/s13058-016-0787-0. http://dx.doi.org/10.1186/s13058-016-0787-0.1465-5411http://nrs.harvard.edu/urn-3:HUL.InstRepos:29739194Background: Inter-women and intra-women comparisons of mammographic density (MD) are needed in research, clinical and screening applications; however, MD measurements are influenced by mammography modality (screen film/digital) and digital image format (raw/processed). We aimed to examine differences in MD assessed on these image types. Methods: We obtained 1294 pairs of images saved in both raw and processed formats from Hologic and General Electric (GE) direct digital systems and a Fuji computed radiography (CR) system, and 128 screen-film and processed CR-digital pairs from consecutive screening rounds. Four readers performed Cumulus-based MD measurements (n = 3441), with each image pair read by the same reader. Multi-level models of square-root percent MD were fitted, with a random intercept for woman, to estimate processed–raw MD differences. Results: Breast area did not differ in processed images compared with that in raw images, but the percent MD was higher, due to a larger dense area (median 28.5 and 25.4 cm2 respectively, mean √dense area difference 0.44 cm (95% CI: 0.36, 0.52)). This difference in √dense area was significant for direct digital systems (Hologic 0.50 cm (95% CI: 0.39, 0.61), GE 0.56 cm (95% CI: 0.42, 0.69)) but not for Fuji CR (0.06 cm (95% CI: −0.10, 0.23)). Additionally, within each system, reader-specific differences varied in magnitude and direction (p < 0.001). Conversion equations revealed differences converged to zero with increasing dense area. MD differences between screen-film and processed digital on the subsequent screening round were consistent with expected time-related MD declines. Conclusions: MD was slightly higher when measured on processed than on raw direct digital mammograms. Comparisons of MD on these image formats should ideally control for this non-constant and reader-specific difference. Electronic supplementary material The online version of this article (doi:10.1186/s13058-016-0787-0) contains supplementary material, which is available to authorized users.en-USBreast densityImage processingMammographic density assessmentBreast cancerMethodsJournal Article2017-01-0310.1186/s13058-016-0787-0