Table 2: Summary of representative studies using clustering based methods for mammographic tissue segmentation. denotes correlation coefficient. Note that () largely identical studies are excluded in the list and () in case of multiple results, only the best reported results are listed.

Study Year Number of density categories Modalities Number of views Number of images Segmentation evaluation Risk/density estimation accuracy

General clustering
Oliver et al. [38] 2005Fatty and dense Digitised SFM MLO 180 (MIAS) N/A 73% (fatty, glandular, and dense)
Strange et al. [39] 2013Dense and fatty FFDM CC 12 Visually assessed N/A
Marias et al. [40] 2005Dense, semidense, and fattyDigitised SFM MLO 146 Visually assessed 65% (BI-RADS I and II)
86% (BI-RADS III and IV)
Oliver et al. [41]2005Dense and fatty Digitised SFM MLO 300 (DDSM) N/A 47% (BI-RADS)
Oliver et al. [42]2005Dense and fatty Digitised SFM MLO 320 (MIAS) and 300 (DDSM) N/A 48% MIAS, 47% DDSM (BI-RADS)
Oliver et al. [43] 2007Dense and fatty Digitised SFM MLO 322 (MIAS) N/A 78% (BI-RADS)
Oliver et al. [44] 2008Dense and fatty Digitised SFM MLO and CC 322 (MIAS) and 831 (DDSM) Visually assessed 77% MIAS, 86% DDSM (BI-RADS)
Oliver et al. [45] 2006Dense and fatty Digitised SFM MLO 322 (MIAS) Visually assessed 82% (BI-RADS)
Torrent et al. [46] 2008Dense and fatty FFDM MLO and CC 300 Visually assessed 82% MLO, 75% CC (BI-RADS)
Tortajada et al. [47] 2012Dense and fatty Digitised SFM and FFDMMLO and CC 322 (MIAS), 831 (DDSM), and 236 (digital DB)Visually assessed 86% MIAS, 77% DDSM, and 92% digital DB (BI-RADS)

Adaptive/modified fuzzy -means
Chen and Zwiggelaar [48] 20104 densities Digitised SFM MLO N/A Visually assessed N/A
Keller et al. [49] 20112–9 densities FFDM (processed)MLO 160 Visually assessed; = 0.75 (automatic-manual)N/A
Keller et al. [50] 20122–13 densities FFDM (processed and raw)MLO 160 Visually assessed; (raw, processed) = 0.82, 0.85 (automatic-manual)N/A

Expectation-maximisation
Aylward et al. [51] 1998Dense, fatty, and uncompressed-fattyDigitised SFM MLO and CC 70 Visually assessed N/A
Zwiggelaar et al. [52] 20024–6 densities Digitised SFM MLO 263 (MIAS) Visually assessed 67% (SCC)
Zwiggelaar et al. [53] 20034–6 densities Digitised SFM MLO 263 (MIAS) Visually assessed 86% (SCC)
Zwiggelaar et al. [54] 20034–6 densities Digitised SFM MLO 263 (MIAS) N/A 86% (BI-RADS)
Zwiggelaar and Denton [55] 20044 densities Digitised SFM MLO 36 (MIAS) Visually assessed 75% (4 densities: 0%–10%, 11%–25%, 26%–50%, and 51%–75%)
Selvan et al. [56] 20065/8 densities Digitised SFM MLO 112 (mini-MIAS) Visually assessed (92% good/excellent)N/A