Counting ovarian antral follicles by ultrasound: a practical guide
Coelho Neto MA (1), Ludwin A (2), Borrell A (3), Benacerraf B (4), Dewailly D (5), da Silva Costa F (6), Condous G (7), Alcazar JL (8), Jokubkiene L (9), Guerriero S (10), Van den Bosch T (11), Martins WP (1,12).
To summarize the main aspects of several available techniques to perform ovarian antral follicle count (AFC), to propose a standardized report and to draw perspectives for future research on this subject.
This is a consensus paper from a group of clinicians and sonologists. The initial manuscript was written by three authors and then submitted to all the other authors asking for comments/corrections.
After three versions incorporating suggestions, the fourth version of the manuscript was approved by all the authors.
AFC should be performed by transvaginal ultrasound using probes with frequency ≥ 7 MHz. We suggest a minimum training of at least 20-40 supervised exams; the operator should be able to adjust the machine settings in order to achieve the best contrast between follicular fluid and ovarian stroma.
Follicle count might be evaluated by real time two-dimensional ultrasound (2D-US), by stored 2D-US cine-loops, and by stored three-dimensional ultrasound (3D-US) data-sets. Real time 2D-US has the advantage of permitting extra maneuvers to ensure whether an anechoic structure is a follicle, as the patient is present, but may require longer scanning time, particularly when there is a large number of follicles, resulting in more discomfort to the patients.
Cine loop has the advantages of reducing scanning time and also allows other observers to count the ovarian follicles. 3D-US imaging requires special ultrasound machines and extra-training for acquisition/analysis but has the same advantages of the cine-loop and also allows employing different imaging techniques, as volume contrast imaging (VCI), inversion mode and the use of semi-automated techniques as sonography-based automated volume calculation (SonoAVC).
Some recommendations based on the available evidence were performed. However, there is no strong evidence that one method is better than the others and the operator should choose the method for counting ovarian follicles based on the availability and on the preference/skills. More studies evaluating how to improve the reliability of AFC should be encouraged.