Motion detection and Correction
Human tissue is constantly in motion. Apart from voluntary actions, physiologic motion, such as heartbeat, circulation, breathing or peristaltic activity, may be present within the sensitive volume during an MR experiment. MR imaging scans or spectroscopic acquisitions typically require one to several minutes to complete. Motion during MR signal acquisition may severely impair data quality. Even minuscule involuntarily head motions due to swallowing or muscle tone changes may result in substantial motion artifacts. Motion during MRI acquisitions is a significant problem in the clinical routine, affecting the diagnostic accuracy and scanner througput.
Several physical mechanisms are responsible for the appearance of the motion artifacts. Therefore there is no one-fits-all remedial solution available. Various approaches have been developed for improving data quality, which are effective in different clinical and research applications.
Motion detection using external sensors
For rigid objects and non-deformable organs the deteriorative effects of motion on MRI data may be entirely undone if the accurate position and orientation information is available in real time. Optical motion tracking systems are capable of delivering such information with a sufficient accuracy and a low temporal latency. Several systems have been developed to track the position of specialized markers, while being exposed to strong magnetic and radio frequency fields. One or several cameras located in the magnet bore have proven effective for accurately tracking head motion during long acquisitions and thereby improving the image quality in long MRI acquisitions.
Motion compensation using MRI navigators
Breathing motion is a big issue in cardiac magnetic resonance imaging and spectroscopy. External trackers, such as respiratory belts or even optical cameras can only deliver indirect indication concerning the actual motion of the organs in abdomen. Specialized rapid MRI scans, so-called MR navigators, offer a unique opportunity to gain sufficient information on the motion of internal organs. We have developed 3D heart detection and tracking approaches for both 3T and 7T scanners, which allow to void uncomfortable and unreliable prolonged breath hold for detailed cardiac MR acquisitions.
Research Groups
Zaitsev group | Schmid group