Purpose: CEST MRI for breast lesion characterization is promising. However, artifacts are prone to develop in breast CEST imaging due to strong lipid signals. The aims of the study are: 1) to develop and validate the CEST-Dixon imaging sequence for simultaneous water-fat separation and B0 mapping; 2) use the CEST-Dixon method to characterize suspicious lesions in patients undergoing percutaneous biopsy.
Methods: The gradient-echo multi-echo Dixon acquisition is used to create fat-free CEST and B0 maps. The sequence has been validated in phantoms and in vivo. Five healthy volunteers and ten patients were scanned to compare the CEST contrast in three frequency ranges centered at 1, 2 and 3.5 ppm. The correlation between the CEST contrast and pathology markers (tumor type, ER status, Ki-67) was also investigated by stratifying the patients into ER-negative invasive ductal carcinoma (IDC) (more aggressive), ER-positive IDC (less aggressive) and benign groups.
Results: The CEST-Dixon sequence shows homogenous fat removal in the water-only images. The ER-negative IDC tissues display a trend to higher CEST contrast in all three frequencies ranges, while the ER-positive IDC, benign and normal tissues have lower CEST contrast. No significant differences were observed between the ER-positive IDC, benign and normal tissues. Of the three frequencies ranges, the CEST contrasts at 1 ppm are high in the ER-negative IDC group, have the largest difference between the ER-negative IDC and the other groups and have the highest correlation with Ki-67.
Conclusions: Breast CEST-Dixon imaging shows potential to differentiate more aggressive from less aggressive cancers.
Keywords: CEST; Dixon; Ki-67; breast MRI; breast cancer; estrogen receptor.