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mathieuboudreau committed Oct 8, 2024
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Expand Up @@ -27,7 +27,7 @@ Temporal unwrapping uses multiple time points (>=2) to unwrap the image. By acqu
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If we assume a maximum field offset {math}`\Delta f_{0,max}` of 1 ppm at 3T (~127 MHz), we can calculate a maximum field offset ({math}`\Delta f_{0,max}`) of 1 µT or 127 Hz. The [Nyquist criteria](https://en.wikipedia.org/wiki/Nyquist_frequency) can be used to calculate the maximum echo time difference (TE) required to satisfy the no-wrapping requirement in the phase difference image ({math}`\Delta \text{TE} = \left( \Delta f_{0,max} \right)^{-1}). Table 1 shows TE for multiple field strength assuming inhomogeneities of 1 ppm. As shown, the echo spacing is _B_{sub}`0` dependent, as higher field offsets are observed at higher field strengths.
If we assume a maximum field offset {math}`\Delta f_{0,max}` of 1 ppm at 3T (~127 MHz), we can calculate a maximum field offset ({math}`\Delta f_{0,max}`) of 1 µT or 127 Hz. The [Nyquist criteria](https://en.wikipedia.org/wiki/Nyquist_frequency) can be used to calculate the maximum echo time difference (TE) required to satisfy the no-wrapping requirement in the phase difference image ({math}`\Delta \text{TE} = \left( \Delta f_{0,max} \right)^{-1}`). Table 1 shows TE for multiple field strength assuming inhomogeneities of 1 ppm. As shown, the echo spacing is _B_{sub}`0` dependent, as higher field offsets are observed at higher field strengths.

```{list-table} Maximum echo time required to respect the Nyquist criteria for different field strengths for ΔB0 of 1 ppm.
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