FLASHzero Documentation

MRM2024: MR-zero meets FLASH

This repository contains sequence files and animations demonstrating the optimization process described in the article "MR-zero meets FLASH – Controlling the transient signal decay in gradient- and rf-spoiled gradient echo sequences."

Data Files

RF phases for Task 2 are saved in the following files:

• MRM2024/data/task2_rfphase_brain.npy
• MRM2024/data/task2_rfphase_phantom.npy

Task 2: RF Phase Details

Phantom

• RF Phase File: task2_rfphase_phantom.npy
• Sequence Parameters:
  • Flip Angle (α): 10°
  • Repetition Time (TR): 10 ms
  • Echo Time (TE): 5 ms
  • Readout Bandwidth: 217 Hz/pixel
  • Field of View (FOV): 200 mm
  • Slice Thickness: 10 mm
  • Matrix Size: 128 x 128
• Tissue Properties:
  • T1: ≈ 1.0 s
  • T2: ≈ 0.16 s
  • Relative B1 (rB1): ≈ 0.77
  • Diffusion Coefficient (D): ≈ 1.6 ∙ 10^(-3) mm²/s

Brain

• RF Phase File: task2_rfphase_brain.npy
• Sequence Parameters:
  • Flip Angle (α): 19.5°
  • Repetition Time (TR): 6 ms
  • Echo Time (TE): 3.2 ms
  • Readout Bandwidth: 500 Hz/pixel
  • Field of View (FOV): 200 mm
  • Slice Thickness: 10 mm
  • Matrix Size: 128 x 128
• Tissue Properties:
  • T1: ≈ 1.5 s
  • T2: ≈ 0.11 s
  • Relative B1 (rB1): ≈ 0.77
  • Diffusion Coefficient (D): ≈ 0.84 ∙ 10^(-3) mm²/s

Colab MR-zero simulation

• You can run the Colab to simulate different standard rf increments or optimization tasks.
  • https://github.com/MRsources/FLASHzero/blob/main/MRM2024/FLASHzero.ipynb
  • https://colab.research.google.com/github/MRsources/FLASHzero/blob/main/MRM2024/FLASHzero.ipynb
• You can run the Colab to see the influence of the Epstein artifact on different sharp edges (Comparison with Gibbs Ringing)
  • https://github.com/MRsources/FLASHzero/blob/main/MRM2024/Epstein_Artifact_PSF.ipynb
  • https://colab.research.google.com/github/MRsources/FLASHzero/blob/main/MRM2024/Epstein_Artifact_PSF.ipynb