Intravoxel incoherent motion imaging of tumor microenvironment in locally advanced breast cancer

Diffusion-weighted imaging plays important roles in cancer diagnosis, monitoring, and treatment. Although most applications measure restricted diffusion by tumor cellularity, diffusion-weighted imaging is also sensitive to vascularity through the intravoxel incoherent motion effect. Hypervascularity can confound apparent diffusion coefficient measurements in breast cancer. We acquired multiple b-value diffusion-weighted imaging at 3 T in a cohort of breast cancer patients and performed biexponential intravoxel incoherent motion analysis to extract tissue diffusivity (D_t), perfusion fraction (f_p), and pseudodiffusivity (D_p). Results indicated significant differences between normal fibroglandular tissue and malignant lesions in apparent diffusion coefficient mean (±standard deviation) values (2.44 ± 0.30 vs. 1.34 ± 0.39 μ²/msec, P < 0.01) and D_t (2.36 ± 0.38 vs. 1.15 ± 0.35 μ²/msec, P < 0.01). Lesion diffusion-weighted imaging signals demonstrated biexponential character in comparison to monoexponential normal tissue. There is some differentiation of lesion subtypes (invasive ductal carcinoma vs. other malignant lesions) with f_p (10.5 ± 5.0% vs. 6.9 ± 2.9%, P = 0.06), but less so with D_t (1.14 ± 0.32 μ²/msec vs. 1.18 ± 0.52 μ²/msec, P = 0.88) and D_p (14.9 ± 11.4 μ²/msec vs. 16.1 ± 5.7 μ²/msec, P = 0.75). Comparison of intravoxel incoherent motion biomarkers with contrast enhancement suggests moderate correlations. These results suggest the potential of intravoxel incoherent motion vascular and cellular biomarkers for initial grading, progression monitoring, or treatment assessment of breast tumors. Magn Reson Med, 2011.