Magnetic barcode imaging for contrast agents.

Purpose: To demonstrate a new MR imaging approach that unambiguously identifies and quantitates contrast agents based on intrinsic agent properties such as r(1), r(2), r(2)(+), and magnetic susceptibility. The approach is referred to as magnetic barcode imaging (MBI). Methods: Targeted and bioresponsive contrast agents were imaged in agarose phantoms to generate T-1, T-2, T-2(_)+, and quantitative susceptibility maps. The parameter maps were processed by a machine learning algorithm that is trained to recognize the contrast agents based on these parameters. The output is a quantitative map of contrast agent concentration, identity, and functional state. Results: MBI allowed the quantitative interpretation of intensities, removed confounding backgrounds, enabled contrast agent multiplexing, and unambiguously detected the activation and binding states of bioresponsive and targeted contrast agents. Conclusion: MBI has the potential to overcome significant limitations in the interpretation, quantitation, and multiplexing of contrast enhancement by MR imaging probes. (C) 2016 International Society for Magnetic Resonance in Medicine.