Imaging Microstructural Parameters of Breast Tumor in Patient Using Time-Dependent Diffusion: A Feasibility Study

<b>Objectives</b>: To explore the feasibility of time-dependent diffusion in clinical applications of breast MRI, as well as the capacity of quantitative microstructural mapping for characterizing the cellular properties in malignant and benign breast tumors. <b>Methods</b>: 38 patients with 45 lesions were enrolled. Diffusion MRI acquisition was conducted with a combination of pulsed gradient spin-echo sequences (PGSE) and oscillating gradient spin-echo (OGSE) on a 3T MRI scanner. The microstructural parameters including cellularity extracellular diffusivity (D_ex), mean cell size, intracellular volume fraction (ν_in), and the apparent diffusion coefficient (ADC) values were calculated. Each parameter was compared using the unpaired <i>t</i>-test between malignant and benign tumors. The area under the receiver operating characteristic curve (AUC) values was used to evaluate the diagnostic performance of different indices. <b>Results</b>: The mean diameter, D_ex, ADC_0Hz, ADC_25Hz, and ADC_50Hz were significantly lower in the malignant group than in the benign group (<i>p</i> < 0.001), while ν_in and cellularity were significantly higher in the malignant group (<i>p</i> < 0.001). All the microstructural parameters and time-dependent ADC values achieved high accuracy in differentiating between malignant and benign tumors of the breast. For microstructural parameters, the AUC of the cellularity was greater than others (AUC = 0.936). In an immunohistochemical subgroup comparison, the PR-positive group had significantly lower ν_in and cellularity, and significantly elevated D_ex and ADC_0Hz compared to the negative groups (<i>p</i> < 0.05). When combining diffusion parameters (cellularity, diameter, and ADC_25Hz), the highest diagnostic performance was obtained with an AUC of 0.969. <b>Conclusions</b>: DWI with a short diffusion time is capable of providing additional microstructural parameters in differentiating between benign and malignant breast tumors. The time-dependent diffusion MRI parameters have the potential to serve as a non-invasive tool to probe the differences in the internal structures of breast lesions.