Fig. 2.

Adapted from Reference [28]. Image for understanding fat and mammary gland distribution in breast image. a The fibroglandular zone is distributed to the periphery. The mammary lateral and posterior border lines are clear. Some fatty lobules (asterisk) are partially visible between the glandular lobes. PAFS: protective adipofascial system (filled triangle), LAFS: lubricant adipofascial system (open triangle). b There is abundant mammary posterior fat. The mammary lateral and posterior border lines are clear. c Fat is mixed in the fibroglandular zone. The mammary lateral and posterior border lines are clear. d The fibroglandular tissues are distributed between multiple fat lobules, and the lateral and posterior fat boundaries are ambiguous. e The fibroglandular tissues are mainly distributed near the nipple, and the fibroglandular tissues between the fat lobules are barely visible. Sometimes, mammary gland distribution patterns shown in (a–e) are mixed in one breast. Use the technique in Fig. 4 to detect the fatty breast lateral borderline (d and e dotted circles) on US images