Ultrasound images of the ovaries taken using an ultrasound device. (A) Shows an ovary with a dominant follicle, and (B) shows an ovary with a corpus luteum. In (A), the white dotted line indicates the ovary, and the white solid line indicates the dominant follicle. In (B), the white dotted line indicates the ovary, and the white solid line indicates the corpus luteum. The cross-sectional area was calculated using the horizontal and vertical diameters of the dominant follicle and corpus luteum within the ovary.