Simultaneous quantification of SPIO and gadolinium contrast agents using MR fingerprinting.

PURPOSE

Develop a magnetic resonance fingerprinting (MRF) methodology with R quantification, intended for use with simultaneous contrast agent concentration mapping, particularly gadolinium (Gd) and iron labelled CD8+ T cells.

METHODS

Variable-density spiral SSFP MRF was used, modified to allow variable TE, and with an exp.(-TE·R) dictionary modulation. In vitro phantoms containing SPIO labelled cells and/or gadolinium were used to validate parameter maps, probe undersampling capacity, and verify dual quantification capabilities. A C57BL/6 mouse was imaged using MRF to demonstrate acceptable in vivo resolution and signal at 8× undersampling necessary for a 25-min scan.

RESULTS

Strong agreement was found between conventional and MRF-derived values for R, R, and R. Expanded MRF allowed quantification of iron-loaded CD8+ T cells. Results were robust to 8× undersampling and enabled recreation of relaxation profiles for both a Gd agent and iron labelled cells simultaneously. In vivo data demonstrated sufficient SNR in undersampled data for parameter mapping to visualise key features.

CONCLUSION

MRF can be expanded to include R, R, and R mapping required for simultaneous quantification of gadolinium and SPIO in vitro, allowing for potential implementation of a variety of future in vivo studies using dual MR contrast agents, including molecular imaging of labelled cells.