DeepControl: 2DRF pulses facilitating B1+ inhomogeneity and B0 off‐resonance compensation in vivo at 7 T

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DeepControl: 2DRF pulses facilitating urn:x-wiley:07403194:media:mrm28667:mrm28667-math-0002 inhomogeneity and B0 off‐resonance compensation in vivo at 7 T

Mads Sloth Vinding, Christoph Stefan Aigner, Sebastian Schmitter, Torben Ellegaard Lund

Abstract

Purpose

Rapid 2DRF pulse design with subject‐specific urn:x-wiley:07403194:media:mrm28667:mrm28667-math-0006 inhomogeneity and B0 off‐resonance compensation at 7 T predicted from convolutional neural networks is presented.

Methods

The convolution neural network was trained on half a million single‐channel transmit 2DRF pulses optimized with an optimal control method using artificial 2D targets, urn:x-wiley:07403194:media:mrm28667:mrm28667-math-0007 and B0 maps. Predicted pulses were tested in a phantom and in vivo at 7 T with measured urn:x-wiley:07403194:media:mrm28667:mrm28667-math-0008 and B0 maps from a high‐resolution gradient echo sequence.

Results

Pulse prediction by the trained convolutional neural network was done on the fly during the MR session in approximately 9 ms for multiple hand‐drawn regions of interest and the measured urn:x-wiley:07403194:media:mrm28667:mrm28667-math-0009 and B0 maps. Compensation of urn:x-wiley:07403194:media:mrm28667:mrm28667-math-0010 inhomogeneity and B0 off‐resonances has been confirmed in the phantom and in vivo experiments. The reconstructed image data agree well with the simulations using the acquired urn:x-wiley:07403194:media:mrm28667:mrm28667-math-0011 and B0 maps, and the 2DRF pulse predicted by the convolutional neural networks is as good as the conventional RF pulse obtained by optimal control.

Conclusion

The proposed convolutional neural network‐based 2DRF pulse design method predicts 2DRF pulses with an excellent excitation pattern and compensated urn:x-wiley:07403194:media:mrm28667:mrm28667-math-0012 and B0 variations at 7 T. The rapid 2DRF pulse prediction (9 ms) enables subject‐specific high‐quality 2DRF pulses without the need to run lengthy optimizations.