Normal parenchymal enhancement patterns in women undergoing MR screening of the breast.

Objectives: To characterize the kinetic and morphological presentation of normal breast tissue on DCE-MRI in a large cohort of asymptomatic women, and to relate these characteristics to breast tissue density.

Methods: 335 consecutive breast MR examinations in 229 asymptomatic women undergoing high-risk screening evaluations based on recommendations from the American Cancer Society including strong family history and genetic predisposition were selected for IRB-approved review (average age 49.2 ± 10.5 years). Breast tissue density was assessed on precontrast T₂-weighted images. Parenchymal enhancement pattern (PEP) was qualitatively classified as minimal, homogeneous, heterogeneous or nodular. Quantitative analysis of parenchymal enhancement kinetics (PEK) was performed, including calculation of initial and peak enhancement percentages (E₁, E(peak)), the time to peak enhancement (T ( peak )) and the signal enhancement ratio (SER).

Results: 41.8% of examinations were classified as minimal, 13.7% homogeneous, 23.9% heterogeneous and 21.2% nodular PEP. Women with heterogeneously or extremely dense breasts exhibited a higher proportion of nodular PEP (44.2% (27/61)) and significantly higher E₁, and E(peak) (p < 0.003) compared with those with less dense breasts.

Conclusions: Qualitative and quantitative parenchymal enhancement characteristics vary by breast tissue density. In future work, the association between image-derived MR features of the normal breast and breast cancer risk should be explored.