Apparent diffusion coefficient and intravoxel incoherent motion-diffusion kurtosis model parameters in invasive breast cancer: Correlation with the histological parameters of whole-slide imaging

Objectives: To evaluate the correlation of ADC and IVIM-diffusion kurtosis (DK) model parameters with quantitative histological parameters of whole-slide imaging (WSI). Methods: This retrospective study (September 2015–July 2016) included 37 consecutive patients (all females; median age: 64 years, range, 41–82 years), each with a single invasive breast ductal carcinoma lesion with a mass appearance on preoperative MRI. DWI with b-values of 0, 50, 100, 300, 550, 850, and 1000 s/mm² was performed. ADC maps were generated with b-values of 50 and 850 s/mm². The IVIM-DK model was analysed using the following formula: Sb=S0fe^−bD∗+1−fe^{−bD+1/6kbD2} where S is the signal intensity, b is the b-value, f is the perfusion fraction, D* is the pseudo-diffusion coefficient of the vascular component, D is the diffusion coefficient of the non-vascular component, and k is the diffusion kurtosis. Whole tumour segmentation was performed to obtain the mean ADC, f, D*, D, and k. Quantitative histological parameters were obtained using cytokeratin immunostaining and WSI. The correlation of ADC and IVIM-DK model parameters with quantitative histological parameters was examined by Pearson's correlation. Results: The ADC was significantly correlated with the area ratio of interstitium (r = 0.53, p = 0.00082) and entropy (r = −0.58, p = 0.00019). k was significantly correlated with the area ratio of cancer cell nuclei (r = 0.53, p = 0.00079). Conclusions: Since the ADC reflected the area ratio of interstitium and entropy, and diffusion kurtosis reflected the area ratio of cancer cell nuclei, these parameters may be effective in distinguishing between benign and malignant breast tumours and in grading breast cancer.