Motion Correction

Patient motion has long been recognised as a problem in MR imaging. A 1997 study of 297 first-time adult MRI patients showed 6.4% of scans were of impaired diagnostic quality due to motion [1]. These numbers are described by the authors as being inline with an earlier German study of 21,000 cases (8-17% scans of impaired diagnostic quality) [2]. Despite modern hardware and reconstruction, motion remains a significant problem within images. Furthermore, the expectation of motion results in the use of rapid sequences that may compromise resolution, contrast or signal to noise. This article describes the physics of motion artefacts and their correction in image reconstruction, strategies for avoiding motion and methods to infer motion prior to correction. The article and the accompanying lecture are intended as an overview for the interested reader and not a comprehensive review. The remainder of the article will be technology focused, but in practice, good patient preparation is also effective in reducing motion artefacts, see for example [3].