Bulk permittivity variations in the human breast over the menstrual cycle

A female volunteer is scanned daily using a system to measure bulk permittivity of the breast. The measured data are then compared to the volunteer's menstrual cycle. A permittivity increase of about 10% is found during the luteal phase compared to the follicular phase of the cycle. This correlates with breast density increase reported with X-ray mammography during the luteal phase.