Next steps to simulate cardiac MRI

[cncastillo]

This can be divided into two problems:

Phantom

• [ ] Currently, there is no ECG signal or RR intervals in the Phantom object. Adding a parameter for this in the Phantom object is necessary.
• [ ] We need to creat a cardiac phantom, probably based on the XCAT phantom (talk with Claudia Prieto). The main problem, in this case, is how to obtain the displacement fields $\boldsymbol{u}(\boldsymbol{x},t)$, as XCAT just provides multiple images for every cardiac phase without a way to "follow the spins".
• [ ] A more challenging problem is how to incorporate the RR intervals to accelerate or slow down the movement of the Phantom. My suggestion is that the phantom displacement field is defined for a normal heart rate of 1s, and then for each heartbeat, the displacement field is changed based on the RR [s], or $\boldsymbol{u}\left(\boldsymbol{x},\frac{1}{\mathrm{RR}_i}t\right)$.

  Pulseq

• [ ] The Pulseq reader is lacking the implementation of the Extensions "EXT". This is where the cardiac triggering is done.
• [ ] We also need to add in the PulseDesigner module the ability to create triggers like in the MATLAB implementation of Pulseq: trig=mr.makeTrigger('physio1','duration', 2000e-6);.

  Simulation

  • [ ] The simulator must use the RR intervals (if present) of the Phantom object to time the Sequence. This means the delays of some parts of the Sequence should be replaced based on the RR intervals.

[cncastillo]

Attached the demo for cardiac sequences in: writeCineGradientEcho.zip

[pvillacorta]

No ECG-like signal has yet been implemented for triggering, but, from #184, I have been able to simulate a bSSFP sequence (as I say, without triggering, but always considering the same RR interval, of duration 1s) on a moving Phantom:

[cncastillo]

This looking fantastic Pablo! thanks for sharing :smile:, what is the function that generates this phantom?

[pvillacorta]

In #184, see function read_phantom. It is used to read file KomaMRI.jl/examples/2.phantoms/ring_motion.phantom