Multiparametric MRI With Dynamic Contrast Enhancement, Diffusion-Weighted Imaging, and 31-Phosphorus Spectroscopy at 7 T for Characterization of Breast Cancer.

OBJECTIVES: To describe and to correlate tumor characteristics on multiparametric 7 tesla (T) breast magnetic resonance imaging (MRI) with prognostic characteristics from postoperative histopathology in patients with breast cancer.

MATERIALS AND METHODS: Institutional review board approval and written informed consent of 15 women (46-70 years) with 17 malignant lesions were obtained. In this prospective study (March 2013 to March 2014), women were preoperatively scanned using dynamic contrast-enhanced MRI, diffusion-weighted imaging, and 31-phosphorus spectroscopy (¹³P-MRS). The value of the protocol was assessed to quantify tumor differentiation and proliferation. Dynamic contrast-enhanced MRI was assessed according to the American College of Radiology Breast Imaging Reporting and Data System-MRI lexicon. Apparent diffusion coefficients (ADCs) were calculated from diffusion-weighted imaging. On ¹³P-MRS, at the location of the tumor, the amount of phosphorus components was obtained in a localized spectrum. In this spectrum, the height of phosphodiester (PDE) and phosphomonoester (PME) peaks was assessed to serve as a measure for metabolic activity, stratifying tumors into a PDE > PME, PDE = PME, or PDE < PME group. Tumor grade and mitotic count from resection specimen were compared with the MRI characteristics using explorative analyses.

RESULTS: On dynamic contrast-enhanced MRI, the mean tumor size was 24 mm (range, 6-55 mm). An inverse trend was seen between ADC and tumor grade (P = 0.083), with mean ADC of 867 × 10⁻⁶ mm²/s for grade 1 (N = 4), 751 × 10⁻⁶ mm²/s for grade 2 (N = 6), and 659 × 10⁻⁶ mm²/s for grade 3 (N = 2) tumors. Between P-MR spectra and mitotic count, a relative increase of PME over PDE showed significant association with increasing mitotic counts (P = 0.02); a mean mitotic count of 6 was found in the PDE greater than PME group (N = 7), 8 in the PDE = PME group (N = 1), and 17 in the PDE < PME group (N = 3).

CONCLUSIONS: Multiparametric 7 T breast MRI is feasible in clinical setting and shows association between ADC and tumor grade, and between ¹³P-MRS and mitotic count.