PURPOSE: To study the diffusion tensor imaging (DTI) derived characteristics of the lactating breast in normal parenchyma and cancer
METHOD AND MATERIALS: This prospective study was IRB-approved and all participants have signed an informed-consent. Since January 2017, 20 lactating patients (median age and lactation duration: 36y and 6m, respectively) were scanned by diffusion-tensor-imaging (DTI) together with conventional breast-MRI protocol, recorded at 1.5T (GE). Indications included: newly diagnosed breast cancer (n=9) and follow-up on high-risk patients (n=11). DTI was acquired using 32 directional diffusion-gradients and 0,700s/mm2 b-values. DTI parametric maps of the principal diffusion coefficients (λ1,λ2,λ3), mean diffusivity (MD), fractional anisotropy (FA) and maximal anisotropy index (λ1-λ3) were generated and analyzed at pixel resolution using a proprietary software. Based on the dynamic-contrast-enhanced (DCE) subtraction images, DTI`s normal and malignant regions-of-interest (ROIs) were delineated and were statistically compared using Student`s t-tests.
RESULTS: The normal parenchymal breast tissue exhibited bi-modal distribution, characterized with sub-areolar central area with increased diffusivity and reduced anisotropy as opposed to the peripheral areas with relatively lower diffusivity and increased anisotropy, possibly reflecting the respective changes in lactation-ducts` diameter. All nine tumors were detected by DTI maps of λ1, λ2, λ3, MD and λ1-λ3 in agreement with DCEs, exhibiting substantial contrast compared with the ROIs of the apparently-normal tissue of contra-lateral breast and fibroglandular tissue of healthy high-risk patients (p<0.001, for all). The tumors were easily visible on λ1 thresholded maps, whereas on DCE subtraction images the relative enhancement of the tumor was less conspicuous on top of the marked lactation-induced benign background-parenchymal-enhancement (BPE).
CONCLUSION: DTI maps enabled the characterization of physiological lactation-induced parenchymal changes as well as malignant transformations, with substantial parametric contrast, improving the tumor`s conspicuity as revealed by DCE alone.
