Breast Density Assessment in Young Women with Ultrasound based on Speed of Sound: Influence of the Menstrual Cycle

Abstract

To investigate changes in breast density (BD) during the menstrual cycle in young women in comparison to inter-breast and -segment changes as well as reproducibility of a novel Speed-of-Sound (SoS) Ultrasound (US) method.SoS-US uses a conventional US system with a reflector and a software add-on to quantify SoS in the retro-mammillary, inner and outer segments of both breasts. Twenty healthy women (18-40 years) with regular menstrual cycles were scanned twice with two weeks in-between. Three of these were additionally measured twice per week for 25 days. Average SoS (m/s) and ΔSoS (segment-variation SoS; m/s) were measured. Variations between follicular and luteal phases and changes over the four-week period were assessed. Inter-examiner and inter-reader agreements were also evaluated. Variances between cycle phases, examiners and readers were compared.No significant SoS difference was observed between follicular and luteal phases for the twenty women (P = .126), and between all different days for the three more frequently measured women (P = .892). Inter-reader (ICC = 0.999) and inter-examiner (ICC = 0.990) agreements were high. The SoS variance due to menstrual variations was not significantly larger than the inter-examiner uncertainty (P = .461). Inter-reader variations were significantly smaller than menstrual and examiner variations (P < .001).SoS-US showed high inter-examiner and inter-reader reproducibility. The alterations during the menstrual cycles were not significantly larger than the confidence interval of measurements.

Figure 1

Speed-of-Sound (SoS) ultrasound (US) examination setting. (A) View from ventral: breast with positioning frame, reflector, US probe and distance adjustment unit; (B) right breast viewed from above showing the three measured breast segments; (C) Annotation of average SoS value (1562 m/s) and SoS variation range (‘breast heterogeneity’) ΔSoS = 12 m/s in a dense breast segment. The back wall echo of the reflector is used as a timing reference. The automatic reading is displayed as an overlaid red line.

Figure 2

Boxplots of SoS (A) and ΔSoS (B) values of the follicular (n = 20) and luteal phases (n = 20). Average measurements of both breasts are plotted. The P values represent a comparison using paired t test.

Figure 3

Correlation of SoS (A) and ΔSoS (B) measurements of the follicular (n = 20) and luteal phases (n = 20) (average measurements of both breasts).

Figure 4

Frequently measured women. Average values of six segments (three per breast) over a 25-day period.

Figure 5

Correlation of SoS (A) and ΔSoS (B) measurements between examiner 1 and examiner 2 (average measurements of both breasts).

Figure 6

Bland-Altman plot. Automatic annotation – manual annotation (mean of reader 1 and reader 2).

Figure 7

Boxplots of uncertainties between SoS (A) and ΔSoS (B) measurements performed at left: different menstruation phases (luteal/follicular), center: by different examiners, and right: annotated by different readers. Average measurements of both breasts are plotted.