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 5 0.90 6 0.05 bellows, R 5 0.98 6 0.01 NAV, P < 0.001) and the heart (R 5 0.89 6 0.06 bellows, R 5 0.96 6 0.02 NAV, P 5 0.004); thoracic bellows correlated less strongly. The image quality of bellows-gated coronary MRI was similar to NAVgated 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. Magn Reson Med 65:1098-1103,

BackgroundComputer simulations are important for validating novel image acquisition and reconstruction strategies. In cardiovascular magnetic resonance (CMR), numerical simulations need to combine anatomical information and the effects of cardiac and/or respiratory motion. To this end, a framework for realistic CMR simulations is proposed and its use for image reconstruction from undersampled data is demonstrated.MethodsThe extended Cardiac-Torso (XCAT) anatomical phantom framework with various motion options was used as a basis for the numerical phantoms. Different tissue, dynamic contrast and signal models, multiple receiver coils and noise are simulated. Arbitrary trajectories and undersampled acquisition can be selected. The utility of the framework is demonstrated for accelerated cine and first-pass myocardial perfusion imaging using k-t PCA and k-t SPARSE.ResultsMRXCAT phantoms allow for realistic simulation of CMR including optional cardiac and respiratory motion. Example reconstructions from simulated undersampled k-t parallel imaging demonstrate the feasibility of simulated acquisition and reconstruction using the presented framework. Myocardial blood flow assessment from simulated myocardial perfusion images highlights the suitability of MRXCAT for quantitative post-processing simulation.ConclusionThe proposed MRXCAT phantom framework enables versatile and realistic simulations of CMR including breathhold and free-breathing acquisitions.