Quantitative analysis of antral follicle number and size: a comparison of two‐dimensional and automated three‐dimensional ultrasound techniques

Abstract

To compare two-dimensional (2D) ultrasound imaging with automated three-dimensional (3D) ultrasound imaging for the measurement of antral follicle number and size. Twenty-four subjects aged < 40 years underwent transvaginal ultrasound examination (Voluson E8) in the early follicular phase of the menstrual cycle. A 2D ultrasound scan of both ovaries was performed; each antral follicle was identified and then measured by taking the mean of two diameters. A 3D ultrasound dataset of both ovaries was then acquired and analyzed using Sonography-based Automated Volume Count (SonoAVC). The time taken to measure the size of all antral follicles in both ovaries was recorded in seconds for each technique. Antral follicle size was recorded to the nearest millimeter and counts for each 1-mm group were obtained. Antral follicle counts were also grouped according to five predefined size categories: 2.0-5.0 mm, 2.0-6.0 mm, 2.0-8.0 mm, 2.0-9.0 mm and 2.0-10.0 mm. Limits of agreement (LOA) and a paired t-test or Wilcoxon signed ranks test were used to analyze the data depending on their distribution. When antral follicle numbers were compared for each 1-mm follicle size group, 2D ultrasound imaging recorded more follicles measuring 3.0-3.99 mm (mean +/- SD, 4.11 +/- 3.70 vs. 2.63 +/- 2.31; P = 0.019) and 4.0-4.99 mm (mean +/- SD, 4.63 +/- 4.86 vs. 2.68 +/- 2.89; P = 0.013) than did SonoAVC. LOA were widest with follicles measuring 3.0-3.99 mm (LOA, 6.38 and -3.43) and 4.0-4.99 mm (LOA, 7.99 and -4.09). The antral follicle count in each of the five predefined size categories was significantly lower with SonoAVC than with 2D ultrasound imaging (P < 0.05). SonoAVC took significantly less time to measure the size and record the number of antral follicles than did 2D ultrasound imaging (mean +/- SD, 132.05 +/- 56.23 s vs. 324.47 +/- 162.22 s; P < 0.001). Fewer antral follicles are evident overall when SonoAVC is used to analyze 3D ultrasound data. The clinical significance of this remains to be determined but the automated technique is significantly quicker than is making measurements using 2D ultrasound imaging.