This MATLAB code simulates dMRI sequences with echo planar imaging (EPI) and spiral trajectories and characterizes the resulting point spread function (PSF).

• The spiral trajectories are generated using Brian Hargreaves’ code, which can be found here: mrsrl.stanford.edu/~brian/vdspiral/

• The 2D PSF analysis and image reconstruction requires a GPU.

• The images are reconstructed using the expanded signal model, which can be found here: github.com/TardifLab/ESM_image_reconstruction

The effective resolution of single-shot readout trajectories is measured using the Full Width at Half Maximum (FWHM) in phase-encode direction (PE). Follow steps in example_FWHM.m to learn how to use the code for FWHM calculation.

The accuracy of spatial encoding is further characterized by measuring the specificity and sharpening factor of the 2D PSF. Follow example_PSF_2D.m for the definitions of specificity and sharpening factor.

A digital brain phantom and coil sensitivity maps are available to simulate the image reconstruction pipeline and evaluate its impact on image quality. See example_phantom_sim.m for an example on how to use the code.

Implementation of the multiple replica method (Robson et al., 2008) to measure SNR of MRI scans using raw k-space data and noise measurements. example_multiple_replice_recon.m includes the steps to reconstruct the multiple replicas.

Reference: Feizollah, S., Tardif, C. L. (2022). High-resolution diffusion-weighted imaging at 7 Tesla: single-shot readout trajectories and their impact on signal-to-noise ratio, spatial resolution and accuracy.

Link to the dataset: https://doi.org/10.5683/SP3/V7ITEH

For any question about the code please contact: [email protected]