A New Contrast in MR Mammography by Means of Chemical Exchange Saturation Transfer (CEST) Imaging at 3 Tesla: Preliminary Results

Purpose: To evaluate the feasibility to detect and delineate malignant breast lesions in human patients by chemical exchange saturation transfer (CEST) as an MR imaging technique without the need for contrast agent administration. Materials and Methods: Six female patients referred for pre-surgical staging due to histologically confirmed breast cancer were examined with MR at 3 T. The routine breast protocol included T(2w), STIR, T(1w)-DCE and contrast-enhanced T(1w) imaging with SPAIR fat suppression. For CEST imaging, a 3D RF-spoiled gradient echo (GRE) sequence with an optimized saturation pulse train was applied. To assess the diagnostic value of the technique, CEST effects observed between frequency offsets of 1.2 to 1.8 ppm from the bulk water resonance were compared to pharmacokinetic parameter maps (k(ep)) obtained by DCE-MRI. Results: In 3 of 6 patients, regions with high CEST signal intensity correlated well with tumor areas as determined by DCE-MRI. Analysis of signal intensities from ROIs in tumor, fibroglandular, adipose, and muscle tissue revealed significantly higher CEST values in tumor tissue compared to fibroglandular tissue. The detection of lesions was equally well possible with DCE-MRI and CEST-MRI. In the three other patients, the tumor regions could not be delineated based on the CEST image due to artifacts, which were most likely caused by a high content of fat tissue within the ROIs. Conclusion: The results of this initial feasibility study indicate a significant potential of CEST-MRI to discriminate cancer from fibroglandular tissue in the human breast by a CEST contrast generated by endogenous solute molecules.