compute_effective_echo_spacing
- bidsaid.metadata.compute_effective_echo_spacing(water_fat_shift_pixels, epi_factor)[source]
Compute the effective echo spacing for Philips 3T MRI.
The following formula is used:
effective_echo_spacing (in seconds) = water_fat_shift (in pixels) / (field_strength * gyromagnetic ratio * water_fat_difference_ppm) * (epi_factor + 1)
where: field_strength (assumed to be 3T) * gyromagnetic ratio * water_fat_difference_ppm = 3 * 42.58 * 3.4 is approximately 434.215
Parameters
- water_fat_shift_pixels
float The water and fat chemical shift in pixels.
- epi_factor
int The EPI factor or the number of echoes per excitation.
Note
in plane acceleration already accounted for in this factor
Returns
- float
The effective echo spacing in seconds.
References
sdcflows.utils.epimanip module - sdcflows 0+unknown documentation. (2022). Nipreps.org. https://www.nipreps.org/sdcflows/master/api/sdcflows.utils.epimanip.html#mjx-eqn%3Aeq%3Arotime-ees
- water_fat_shift_pixels