Diffusion-weighted MRI: Association between patient characteristics and apparent diffusion coefficients of normal breast fibroglandular tissue at 3 T

OBJECTIVE. The purpose of this study is to assess associations between patient characteristics and apparent diffusion coefficient (ADC) values of normal breast fibroglandular tissue on diffusion-weighted imaging (DWI) at 3 T. MATERIALS AND METHODS. The retrospective study included 103 women with negative bilateral findings on 3-T breast MRI examinations (BI-RADS category 1). DWI was acquired during clinical breast MRI scans using b = 0 and b = 800 s/mm ². Mean ADC of normal breast fibroglandular tissue was calculated for each breast using a semiautomated software tool in which parenchyma pixels were selected by interactive thresholding of the b = 0 s/mm² image to exclude fat. Intrasubject right- and left-breast ADC values were compared and averaged together to evaluate the association of mean breast ADC with age, mammographic breast density, and background parenchymal enhancement. RESULTS. Overall mean ± SD breast ADC was 1.62 ± 0.30 x 10^-3 mm²/s. Intrasubject right- and left-breast ADC measurements were highly correlated (R² = 0.89; p < 0.0001). Increased breast density was strongly associated with increased ADC (p ≤ 0.0001). Age and background parenchymal enhancement were not associated with ADC. CONCLUSION. Normal breast parenchymal ADC values increase with mammographic density but are independent of age and background parenchymal enhancement. Because breast malignancies have been shown to have low ADC values, DWI may be particularly valuable in women with dense breasts owing to greater contrast between lesion and normal tissue.