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Learning how to Clean Fingerprints -- Deep Learning based Separated Artefact Reduction and Regression for MR Fingerprinting
Yiling Xu1, Elisabeth Hoppe1, Peter Speier2, Thomas Kluge2, Mathias Nittka2, Gregor Körzdörfer2, and Andreas Maier1
1Pattern Recognition Lab, Friedrich-Alexander-Universität Erlangen-Nürnberg, Erlangen, Germany, 2Magnetic Resonance, Siemens Healthcare, Erlangen, Germany
We propose a deep learning two-step approach for MRF reconstruction. 1) Artefacts in the fingerprints are reduced with a U-net model. 2) The cleaned fingerprints are used as inputs for a regression network. Performance of our method is shown superior to a direct regression without the first step.  

Figure 3: Quantitative maps from test scan

Row 1: Ground truth maps Row 2: Reconstructed maps without prior artefact reduction and relative error maps Row 3: Reconstructed maps from cleaned fingerprints and relative error maps A clear improvement in the reconstruction quality can be observed using a prior DL-based artefact reduction approach.

Figure 1: U-net architecture for the artefact reduction

As input for our U-net-based artefact reduction we use the main 50 complex-valued components of SVD-compressed fingerprints for each slice, resulting in 100 input channels for real and imaginary parts. The network outputs are the cleaned fingerprints of the same size as the input. For the training, the Mean-Squared-Error of the compressed signals from the dictionary matches and the network outputs is used.