Three-dimensional ultrasound improves the interobserver reliability of antral follicle counts and facilitates increased clinical work flow

Objectives: To compare the interobserver reliability of antral follicle counts made using real-time two-dimensional (2D) ultrasound with offline counts made from stored three-dimensional (3D) data and to assess the time required for such counts.

Methods: Two observers conducted transvaginal ultrasound examinations in 45 subfertile women in the early follicular phase of the menstrual cycle. Antral follicles were counted using real-time 2D ultrasound and the time taken was recorded. A 3D volume was then acquired from each ovary and stored for subsequent offline analysis using the multiplanar view. The time taken for each step was recorded and the total time was calculated. Intraclass correlation coefficients (ICC) and limits of agreement were used to assess reliability.

Results: There was no difference in the mean antral follicle counts using real-time 2D (16.51 +/- 11.51) and 3D (16.33 +/- 12.13) ultrasound. According to ICCs, there was a significantly higher interobserver reliability for counts made using 3D (mean, 0.992; 95% CI, 0.986-0.996) compared with real-time 2D (mean, 0.961; 95% CI, 0.940-0.977) (P < 0.01) ultrasound. 3D ultrasound was also associated with narrower limits of agreement (-2.7 to + 3.1) than was 2D ultrasound (-6.9 to + 6.4). Whilst the total time taken was significantly longer for the 3D technique (239.3 +/- 71.4 s vs. 103.1 +/- 28.6 s, P < 0.001), the time required for the actual ultrasound examination was significantly less (46.4 +/- 7.4 s vs. 103.1 +/- 28.6 s, P < 0.001).

Conclusions: 3D ultrasound significantly improves the interobserver reliability of antral follicle counts. While this is at the expense of time overall, the duration of the actual ultrasound examination and patient exposure is significantly reduced using 3D compared with real-time 2D ultrasound.