Particularities of cardiac MRI
Various strategies exist to scan an organ in motion:
- Fast acquisition sequences
- Synchronization with the motion
- Containing or stopping the motion
The third strategy can only be applied to respiratory motion if the length of breath-hold is compatible with the patient’s clinical state. If breath-hold is not possible, respiratory or echo-navigator gating can be used to synchronize with respiratory motion - the drawback being an increase in acquisition time.
Optimization of cardiac MRI sequences: general principles
Fast MRI sequences will be the technique of choice in cardiac exploration (ultrafast spin echo, fast gradient echo). As well as the RF pulse and gradient sequence, other options can be associated which also accelerate acquisition:
- Single-shot sequences
- Parallel imaging with phased array coils, in some cases dedicated to cardiac imaging
- Optimized k-space filling: segmented k-space, k-space data sharing, partial k-space…
On the other hand, sequences of the echo planar type fail to yield good results due to magnetic susceptibility (pulmonary air, calcifications…).