A multi-parametric PET/MRI study of breast cancer: Evaluation of DCE-MRI pharmacokinetic models and correlation with diffusion and functional parameters

The objective of this study is to compare perfusion parameters, as measured by the shutter speed and the Tofts models applied in DCE-MRI, in malignant breast lesions. Also, to investigate the relationship between perfusion, morphological and functional parameters extracted by the simultaneous acquisition of positron emission tomography (PET) and MRI. 46 patients with histologically confirmed breast cancer were imaged with a 3 T hybrid PET/MRI system, at staging. ¹⁸F-fluorodeoxyglucose (FDG) PET images were acquired simultaneously with MRI, which included DW- and DCE-MRI. Standardized uptake value (SUV), apparent diffusion coefficient (ADC) and pharmacokinetic maps (from the Tofts and shutter speed models) were generated for each primary lesion and a reference, healthy tissue area. Wilcoxon and Spearman tests were used for the statistical analysis. MRI-derived parameters (perfusion and diffusion) and PET SUV_mean were significantly different between tumour and reference tissue (p < 0.05). Significant correlations were found between the two pharmacokinetic models (p < 0.01) and between SUV and pharmacokinetic parameters (K^trans, k_ep, v_e and τ_i). No correlation was observed between ADC and SUV, or between ADC and pharmacokinetic parameters. In conclusion, PET/MRI allows for the characterization of primary lesions in breast cancer. Simultaneous analysis of perfusion, morphological and functional markers reveals good agreement between different pharmacokinetic models. Perfusion parameters showed a good correlation with the SUV in breast lesions. In particular, the shutter speed τ_i was found to be significantly correlated to ¹⁸F-FDG uptake (negative correlation), indicating an association with tumour metabolic mechanisms.