Monitoring Physiological Signals With NMR-on-a-Chip Sensors for Motion Correction in Abdominal MRI

The aim of this study was to evaluate the feasibility of an NMR-on-a-chip (NoC) sensor as local field probe for contactless monitoring of respiratory and cardiac motion-induced field changes and to investigate their applicability for motion synchronization in magnetic resonance imaging (MRI). Cardiac and respiratory motion-induced field changes were recorded at seven positions around the torso of six volunteers. The data were analyzed regarding cardiac and respiratory components and the most promising location for assessment of respiratory motion identified. Further, the sensor-derived signal was correlated with the vendor-provided respiratory belt. The cranial parasternal positions were identified as excellent candidates for mapping cardiac motion, whereas the anterior locations at height of the diaphragm appear most promising for mapping of the respiration. Realtime analysis of the recorded signals was successfully applied for respiratory synchronization of the MR system and showed very good correlation with the respiratory belt with less fluctuation and shorter transient phase during breath-holding. NoC sensors are sensitive enough for monitoring physiological motion and can be applied for respiratory motion synchronization. Depending on the positioning of the sensor, cardiac as well as respiratory-induced field changes can be contactless mapped and used for synchronization of the MRI.