  Purpose: To develop an accelerated Cartesian MRF implementation using a
multi-shot EPI sequence for rapid simultaneous quantification of T1 and T2
parameters. Methods: The proposed Cartesian MRF method involved the acquisition
of highly subsampled MR images using a 16-shot EPI readout. A linearly varying
flip angle train was used for rapid, simultaneous T1 and T2 quantification. The
accuracy of parametric map estimations were improved by using an iterative
projection algorithm. The results were compared to a conventional spiral MRF
implementation. The acquisition time per slice was 8s and this method was
validated on a phantom and a healthy volunteer brain in vivo. Results: Joint T1
and T2 estimations using the 16-shot EPI readout are in good agreement with the
spiral implementation using the same acquisition parameters (deviation less
than 3% for T1 and less than 4% for T2) for the healthy volunteer brain. The T1
and T2 values also agree with the conventional values previously reported in
the literature. The visual quality of the multi-parametric maps generated by
the multi-shot EPI-MRF and spiral-MRF implementations were comparable.
Conclusion: The multi-shot EPI-MRF method generated accurate quantitative
multi-parametric maps similar to conventional Spiral - MRF. This multi-shot
approach achieved provides an alternative for performing MRF using an
accelerated Cartesian readout, thereby increasing the potential usability of
MRF.
