Respiratory bellows revisited for motion compensation: preliminary experience for cardiovascular MR

For many cardiac MR applications, respiratory bellows gating is attractive because it is widely available and not disruptive to or dependent on imaging. However, its use is uncommon in cardiac MR, because its accuracy has not been fully studied. Here, in 10 healthy subjects, the bellows and respiratory navigator (NAV) with the displacement of the diaphragm and heart were simultaneously monitored, during single-shot imaging. Furthermore, bellows-gated and NAV-gated coronary MRI were compared using a retrospective reconstruction at identical efficiency. There was a strong linear relationship for both the NAV and the abdominal bellows with the diaphragm (R = 0.90 ± 0.05 bellows, R = 0.98 ± 0.01 NAV, P < 0.001) and the heart (R = 0.89 ± 0.06 bellows, R = 0.96 ± 0.02 NAV, P = 0.004); thoracic bellows correlated less strongly. The image quality of bellows-gated coronary MRI was similar to NAV-gated and superior to no-gating (P < 0.01). In conclusion, bellows provides a respiratory monitor which is highly correlated with the NAV and suitable for respiratory compensation in selected cardiac MR applications.