Standardization of Breast Dynamic Contrast-enhanced MRI Signal with Application to the Assessment of Background Parenchymal Enhancement Rate

Background: There is currently no clinically accepted method for quantifying background parenchymal enhancement (BPE), though a sensitive method might allow individualized risk management based on the response to cancer-preventative hormonal therapy. Objective: The objective of this pilot study is to demonstrate the utility of linear modeling of standardized dynamic contrast-enhanced MRI (DCEMRI) signal for quantifying changes in BPE rates. Methods: On a retrospective database search, 14 women with DCEMRI examinations pre- and post-treatment with tamoxifen were identified. DCEMRI signal was averaged over the parenchymal ROIs to obtain time-dependent signal curves S(t). The gradient echo signal equation was used to standardize scale S(t) to values of FA = 10 degrees and TR = 5.5 ms, and obtain the standardized DCE-MRI signal S-p(t). Relative signal enhancement was calculated from S-p, and the reference tissue method for T1 calculation was used to standardize to gadodiamide as the contrast agent, obtaining . in the first 6 minutes post-contrast administration was fit to a linear model with the slope alpha denoting the standardized rate relative BPE. Results: Changes in alpha were not found to be significantly correlated with the average duration of tamoxifen treatment, age at the initiation of preventative treatment, or pre-treatment BIRADS breast density category. The average change in alpha showed a large effect size of -1.12, significantly higher than -0.86 observed without signal standardization (p < 0.01). Conclusion: Linear modeling of BPE in standardized DCEMRI can provide quantitative measurements of BPE rates, improving sensitivity to changes due to tamoxifen treatment.