Background:The Pilot Tone (PT) technology allows contactless monitoring of
physiological motion during the MRI scan. Several studies have shown that both
respiratory and cardiac motion can be extracted from the PT signal
successfully. However, most of these studies were performed in healthy
volunteers. In this study, we seek to evaluate the accuracy and reliability of
the cardiac and respiratory signals extracted from PT in patients clinically
referred for cardiovascular MRI (CMR). Methods: Twenty-three patients were
included in this study, each scanned under free-breathing conditions using a
balanced steady-state free-precession real-time (RT) cine sequence on a 1.5T
scanner. The PT signal was generated by a built-in PT transmitter integrated
within the body array coil. For comparison, ECG and BioMatrix (BM) respiratory
sensor signals were also synchronously recorded. To assess the performances of
PT, ECG, and BM, cardiac and respiratory signals extracted from the RT cine
images were used as the ground truth. Results: The respiratory motion extracted
from PT correlated positively with the image-derived respiratory signal in all
cases and showed a stronger correlation (absolute coefficient: 0.95-0.09) than
BM (0.72-0.24). For the cardiac signal, the precision of PT-based triggers
(standard deviation of PT trigger locations relative to ECG triggers) ranged
from 6.6 to 81.2 ms (median 19.5 ms). Overall, the performance of PT-based
trigger extraction was comparable to that of ECG. Conclusions: This study
demonstrates the potential of PT to monitor both respiratory and cardiac motion
in patients clinically referred for CMR