The Normal Ovary: Changes in the Menstrual Cycle

Abstract

The ovaries can be sonographically visualized by transabdominal, transrectal, and transvaginal approach. The golden standard today is the transvaginal approach. Ultrasound provides insight into the psychological changes during the ovarian cycle. Ovaries are imaged as homogeneous, hypoechogenic ovoid structures with slightly echogenic central part. The dominant follicle can be detected between 8th and 12th day of the cycle. The dominant follicle has a linear daily diameter growth of 2–3 mm per day until ovulation, when the diameter of the dominant follicle is 18–28 mm. After ovulation the follicle is transformed in corpus luteum. Transvaginal color Doppler (TVCD) helps in better understanding of the menstrual cycle physiology. Before ovulation perifollicular flow has moderate RI (resistance index) around 0.54 ± 0.04. RI gradually declines and at ovulation measures 0.44 ± 0.04. The peak systolic velocity rises at the onset of ovulation. Corpus luteum formation is characterized with a dramatic increase of the amount of the blood flow with increased velocity and low impedance to blood flow (0.43 ± 0.04). The regression of corpus luteum is characterized with poor color Doppler signals and higher RI. The three-dimensional ultrasound (3D) can be used in order to obtain more information about the ovaries. Volume of the ovary can be measured and calculated more precisely. Dominant and other follicles can be measured automatically using SonoAVC (sonography-based automated volume count). Surface view of the inner layer of the dominant follicle can detect the cumulus oophorus. Antral follicular count can be measured by 2D or 3D ultrasound. The novel technique (SonoAVC) offers an automatic count of antral follicles. If 3D volume of the ovaries with vascularization is scanned, vascular indexes of the whole ovary can be measured (VI, vascular index; FI, flow index; and VFI, vascular flow index). The ovaries are two small, almond-shaped organs located on either side of the uterus, attached by the ovarian ligament to the uterine fundus by the suspensory ligaments to the pelvic side wall and by the mesovarium to the broad ligament. Traditionally the ovaries can be visualized by transabdominal approach using the full bladder for better ultrasonographic visualization. With the full bladder, the intestines are pulled up, and an acoustic window that allows the distinction of the female genital organs is created. The visualization can be compromised by the quantity of the abdominal fat tissue and/or abdominal scars. Ovaries are imaged as homogeneous, hypoechogenic ovoid structures with slightly echogenic central part. Today the transvaginal approach is a golden standard for the estimation of the ovary. The closeness of the probe and the visualized organ allows the use of higher frequency probes that give better resolution and offer more detailed visualization.