Novel Wash-In Characteristics of Background Parenchymal Enhancement on Ultrafast Dynamic Contrast-Enhanced Breast MRI

<b>BACKGROUND</b>. Ultrafast MRI (UFMRI) can minimize background parenchymal enhancement (BPE), improve cancer visualization, and inform characterization of malignancy. Although BPE is a biomarker for breast cancer risk, wash-in characteristics of BPE are unknown. <b>OBJECTIVE</b>. The purpose of this study was to delineate on UFMRI the wash-in behavior of normal BPE in healthy women and to determine associations with patient characteristics. <b>METHODS</b>. This retrospective study evaluated consecutive normal screening breast MRI examinations (BI-RADS category 1) from January 2020 to May 2022 with 1 year of negative follow-up MRI. Characteristics including patient age, menopausal status, and risk factors for cancer were recorded. Fibroglandular tissue and BPE on conventional postcontrast sequences were documented. Ultrafast MR images were analyzed for level, time to enhancement (TTE), and maximum slope (MS) of BPE as indicators of wash-in characteristics. Ordinal logistic regression analyses were conducted using a significance level of .05 (two-sided alpha value). <b>RESULTS</b>. The final sample included 222 women (median age, 50 years; range, 25-81 years), 110 (49.5%) of whom were premenopausal and 112 (50.5%) of whom were postmenopausal. BPE was lower on UFMRI than on conventional MRI in 98.5% of examinations with moderate or marked BPE and in 85.4% of examinations with mild to marked BPE on conventional postcontrast images (<i>p</i> < .001). BPE on UFMRI was marked in 0% and moderate in 4.1% of examinations. BPE was significantly associated with menopausal status, inversely related to age, and significantly associated with TTE. The odds of high BPE on UFMRI were 7.815 times greater in premenopausal women (95% CI, 4.461-13.689; <i>p</i> < .001), 1.067 times less per 1-year increase in age (95% CI, 1.046-10.890; <i>p</i> < .001), and 1.113 times greater per 1-second decrease in TTE (95% CI, 1.054-1.213; <i>p</i> < .001). MS was higher in premenopausal women but was not statistically significant. BPE was not associated with risk factors for cancer. <b>CONCLUSION</b>. UFMRI mitigates BPE, essentially eliminating marked and moderate BPE. TTE varies by age and menopausal status, suggesting hormonal underpinning. <b>CLINICAL IMPACT</b>. Minimizing BPE on UFMRI could improve diagnostic accuracy. Wash-in kinetic parameters of BPE have the potential to serve as biomarkers in breast cancer risk prediction.