Sensitive MRI detection of internalized T1 contrast agents using magnetization transfer contrast

This work addresses the possibility of using Magnetization Transfer Contrast (MTC) for an improved MRI detection of T₁ relaxation agents. The need to improve the detection threshold of MRI agents is particularly stringent when the contrast agents failed to accumulate to the proper extent in targeting procedures. The herein reported approach is based on the T₁ dependence of MT contrast. It has been assessed that MT contrast can allow the detection of a Gd‐containing agent at a lower detection threshold than the one accessible by acquiring T_1W images. Measurements have been carried out either in TS/A cells or in vivo in a syngeneic murine breast cancer model. The reported data showed that in cellular experiments the MTC method displays a better sensitivity with respect to the common T_1W experiments. In particular, the reached detection threshold allowed the visualization of samples containing only 2% of Gd‐labeled cells diluted in unlabeled cells. In vivo experiments displayed a more diversified scheme. In particular, the tumor region showed two distinct behaviors accordingly with the localization of the imaging probe. The probe located in the tumor core could be detected to the same extent either by T_1w or MTC contrast. Conversely, the agent located in the tumor rim was detected with a larger sensitivity by the MTC method herein described. Copyright © 2015 John Wiley & Sons, Ltd.