Parse sequence block
Read gammaSTAR sequence blocks and extract events and timing.
Research work
Interpreting Scanner-Runnable MRI Sequences for Simulation
gammaSTAR sequence programs are parsed into simulator-ready spans, preserving timing, RF events, gradients, and ADC placement.
1-to-1 mapping from executable sequence to simulation
Scanner-runnable sequence block
RF, ADC, gradients and timing are interpreted from the same program used for execution.
◎Why this matters
Sequence descriptions in papers and textbooks are often simplified or idealized. Real scans run on complex, scanner-executable sequence programs that include timing nuances, RF shapes, gradient details, and ADC placement that strongly influence the outcome.
By interpreting the actual scanner-runnable program, the simulator gets a more faithful input for understanding, debugging, and method development.
The gap
- × Simplified diagrams omit timing details
- × RF and gradient shapes are approximated
- × ADC placement may be ambiguous
- × Hard to reproduce scanner issues
Our approach
- ✓ Parse executable gammaSTAR program
- ✓ Detect RF events and ADC windows
- ✓ Collect overlapping gradients
- ✓ Preserve timing and event structure
- ✓ Provide spans for simulation backends
Interpretation pipeline
Detect RF intervals
Identify RF pulses and return start and end times for each RF-active span.
Collect gradients & ADC
Gather overlapping Gx, Gy, Gz and ADC events for the interval.
Split into spans
Separate RF-active Bloch spans from EPG or gradient-moment spans.
Feed simulator
Export spans to the simulation backend with exact timing and event parameters.
Two simulation definitions
Hybrid Bloch + 3D EPG
Slice-profile-aware RF, efficient non-RF propagation
- Bloch simulation for RF-active spans, including finite slice profile and off-resonance.
- 3D EPG-style propagation for gradient-moment spans.
- Captures RF effects while keeping long sequence evolution tractable.
- Useful for contrast studies and sequence behavior analysis.
Gradient-moment definition
Fast trajectory view for validation and debugging
- Represents non-RF spans by their gradient moments.
- Fast path for trajectory and k-space checks.
- Helps validate geometry, timing, and ADC placement.
- Well suited for conventional reconstruction pipelines.
What it enables
Sequence debugging
Localize unexpected behavior seen on the scanner.
k-space validation
Verify trajectories, coverage, and sampling density.
Contrast investigation
Study parameter effects on contrast and signal evolution.
Artifact reproduction
Recreate distortions to understand their origin.
Simulation-guided optimization
Evaluate design choices before scanner execution.
Documentation
Generate reproducible records of what was actually run.