Purpose
Motion is 1 extrinsic source for imaging artifacts in MRI that can strongly deteriorate image quality and, thus, impair diagnostic accuracy. In addition to involuntary physiological motion such as respiration and cardiac motion, intended and accidental patient movements can occur. Any impairment by motion artifacts can reduce the reliability and precision of the diagnosis and a motionâfree reacquisition can become timeâ and costâintensive. Numerous motion correction strategies have been proposed to reduce or prevent motion artifacts. These methods have in common that they need to be applied during the actual measurement procedure with aâpriori knowledge about the expected motion type and appearance. For retrospective motion correction and without the existence of any aâpriori knowledge, this problem is still challenging.
Methods
We propose the use of deep learning frameworks to perform retrospective motion correction in a referenceâfree setting by learning from pairs of motionâfree and motionâaffected images. For this imageâtoâimage translation problem, we propose and compare a variational auto encoder and generative adversarial network. Feasibility and influences of motion type and optimal architecture are investigated by blinded subjective image quality assessment and by quantitative image similarity metrics.
Results
We observed that generative adversarial networkâbased motion correction is feasible producing nearârealistic motionâfree images as confirmed by blinded subjective image quality assessment. Generative adversarial networkâbased motion correction accordingly resulted in images with high evaluation metrics (normalized root mean squared error <0.08, structural similarity index >0.8, normalized mutual information >0.9).
Conclusion
Deep learningâbased retrospective restoration of motion artifacts is feasible resulting in nearârealistic motionâfree images. However, the image translation task can alter or hide anatomical features and, therefore, the clinical applicability of this technique has to be evaluated in future studies.