2009 Max Halvorson

Back to Psych 204 Projects 2009

Differences Between Spin-Echo and Gradient-Echo Imaging

Spin-Echo and Gradient-Echo imaging are two different methods of obtaining fMRI data that vary along various dimensions: the pulse sequence used to generate and obtain the signal, signal-to-noise ratio, and sensitivity to large blood vessels, to name a few.

Background

Gradient Echo

Gradient Echo images are generated by an applied gradient followed by an RF pulse sequence to excite slices one by one and collect data from each. Gradient Echo images have a stronger overall signal than Spin Echo images and the overall signal-to-noise ratio is higher. However, Gradient Echo images are prone to large distortions from large blood vessels, sinuses, and other inhomogeneities.

Spin Echo

Spin Echo images are generated by a 180-degree pulse following the applied gradient. This pulse realigns the dephasing spins and gives another shot at capturing data. Spin Echo images are weaker in signal and signal-to-noise ratio than Gradient Echo images. However, Spin Echo images should be less sensitive to distortions from large blood vessels and sinuses.

Although Gradient Echo images have a stronger overall signal and signal-to-noise ratio and generally show more in most brain regions, Spin Echo images are theorized to avoid distortions due to large blood vessels and inhomogeneities. The hope of this study was to find areas in which Spin Echo images could reveal things in visual cortex that gradient echo could not. For example, areas like hV4...

Methods

MR Analysis

The MR data was analyzed using mrVista software tools.

Pre-processing

All data were slice-time corrected, motion corrected, and repeated scans were averaged together to create a single average scan for each subject. Et cetera.

References - Resources and related work

Software: mrVista

Appendix I - Code and Data

Code

zip file with code

Data

zip file with my data