Towards 3D & 4D Comprehensive CMR

For MRI of the heart, data acquisition needs to be synchronized to the heartbeat and to respiration. Significant aspects of cardiac MRI data collection strategies have remained unchanged over the past two decades, and some major hurdles to overcome at this juncture include operator dependency and time inefficiency. In a deliberate attempt to break away from the decades-old paradigm where data are collected in a prospectively triggered and gated fashion - we propose to sample image data uninterrupted, continuously, without triggering or gating, and irrespective of the heart’s position and its contractile state. By exploiting a free-running 3D golden angle radial imaging sequence, compressed sensing for motion-resolved reconstruction, and center of k-space physiology signal extraction, total self-navigation is enabled and the above paradigm significantly challenged. This leads to 3D imaging of the heart where two temporal dimensions (cardiac cycle and respiration) can be added individually (4D imaging) or in combination (5D imaging). As a result, the acquired data can be queried retrospectively and motion-compensated 3D images can be extracted at any user-desired respiratory position or time point in the cardiac cycle. The technique has been implemented at 1.5T and successfully tested in both healthy adult subjects and preliminarily also in patients. Cardiac MRI without ECG triggering or gating is thus enabled, user interaction is reduced to a minimum as the only remaining interaction is the placement of the imaged volume at the level of the heart, and time efficiency has improved more than 10-fold when compared to conventional approaches. However, larger studies and Gold Standard comparisons are now needed to better characterize the potential of this new method.

Acknowledgements

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References

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