Volumetric Quantification of Breast Tissue Composition Using Transmission Ultrasound: A Validation Study Against MRI

Accurate quantification of fibroglandular tissue volume (FGV) and the fibroglandular ratio which is the ratio of FGV to the total breast volume (TBV) (FGR = FGV/TBV) is critical for assessment of a patient's lifetime breast cancer risk and personalized screening strategies. Magnetic resonance imaging (MRI) is considered the research standard for volumetric breast composition analysis but is limited by cost, availability, and contraindications. This study evaluates the capability of quantitative transmission (QT) imaging technology to measure FGV and FGR and compares these results with MRI-derived metrics, establishing quantitative equivalence between the two modalities.

A retrospective analysis included 53 breasts from 29 women imaged using QT scan and MRI within 30 days as part of the ACCRUE Study (ClinicalTrials.gov NCT03052166). QT data were acquired with the QT Scanner 2000 Model A and reconstructed into 3D speed-of-sound maps and respective reflection maps via a full-wave inverse scattering algorithm. FGV and FGR were computed using a fuzzy c-means segmentation as applied to the quantitative tissue maps. MRI datasets were segmented using a validated template-based method. Statistical comparisons included Pearson correlation (r), intraclass correlation coefficient (ICC), and Bland-Altman analysis.

QT and MRI measurements demonstrated strong correlations for both FGV (r = 0.893) and FGR (r = 0.915, p < 0.0001). Mean biases were -13.2 cm³ for FGV and +12.7% for FGR. Regression slopes were 0.63 and 1.35, respectively, with significant proportional bias for both (p < 0.0001). Systematic differences were consistent with modality-specific contrast mechanisms and field-of-view definitions; the strong correlation and stable, predictable bias support quantitative concordance between the modalities.

QT technology provides accurate, reproducible, and volumetric quantification of breast fibroglandular tissue, demonstrating strong concordance with MRI. These results supported FDA clearance of the QT FGR feature, establishing it as a validated quantitative imaging biomarker for clinical breast density assessment.