Ultrasound image attributes of human ovarian dominant follicles during natural and oral contraceptive cycles

Dominant ovarian follicles of 18 clinically normal women were compared using transvaginal ultrasonography for the 7 days before ovulation during a natural cycle (n = 9) or the 7 days before peak estradiol in women using OC (n = 11). Follicles were analyzed using region and line techniques designed to compare the image attributes numerical pixel value (NPV), pixel heterogeneity (PH) and area under the curve (AUC).NPV was higher in OC cycle follicles with region analysis and tended to be higher with line analysis (p = 0.005 and p = 0.06, respectively). No differences were observed in two other image attributes (AUC and PH), measured with either technique, between natural and OC cycle follicles.The increased NPV value of OC cycle follicles and lack of differences in PH and AUC values between natural cycle and OC cycle follicles did not support the hypothesis that OC cycle follicles would show ultrasonographically detectable signs of atresia. Image attributes observed in OC cycle follicles were not clearly indicative of atresia nor were they large enough to preclude preovulatory physiologic status in OC cycle follicles.Diagnostic gray-scale ultrasonography has revolutionized the study of ovarian biology in animals and humans because it allows researchers and clinicians to assess the development of individual follicles in a direct, non-invasive, and atraumatic manner without interruption or distortion of ovarian function. Prior to the introduction of ultrasonography, histological slices of ovarian tissue were used to elucidate ovarian follicular development; however, histologic investigation only provides information about a single time point and does not permit assessment of follicular function over time. Further, histology cannot be used for time-series studies in humans.Animal models have been developed to elucidate the basic mechanisms of ovarian function in humans and to overcome ethical impossibilities of some aspects of research in humans. To date, however, no app