Proton Density Fat Fraction of Breast Adipose Tissue: Comparison of the Effect of Fat Spectra and Initial Evaluation as a Biomarker

The composition of breast adipose tissue has been shown to vary according to disease state. Proton density fat fraction (PDFF) is a quantitative MR biomarker which has not yet been thoroughly examined in the characterisation of breast fat; this work therefore explores the estimation of breast-specific PDFF. An MR spectrum derived from healthy breast fat is shown to perform significantly better in PDFF calculation of breast adipose tissue amongst a healthy cohort than either 6-peak or 9-peak subcutaneous fat spectra. Calculated PDFF values of breast adipose tissue suggest a similar composition between healthy breast fat and gluteal fat and a reference value of 91.6 +/- 3.0% PDFF is found for healthy breast adipose tissue. Early results indicate that localised regions of lowered adipose PDFF are visible in proximity to both invasive and non-invasive breast cancer; this may be indicative of the inflammation and browning of mammary fat around tumour cells.