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MRsources / MRzero-Core

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no visible diffusion in playground pulseq DWI sequence #56

Closed J-Endres closed 5 months ago

J-Endres commented 5 months ago

https://mrzero-core.readthedocs.io/en/latest/playground_mr0/mr0_DWI_GRE_2D_seq.html

the b-value of the diffsuion weighted GRE is too low to make the artificial tumor in the data visible. Calculate the b-value correctly in order to print it out and to set gradient amplitudes accordingly

J-Endres commented 5 months ago

Fixed by 8891f5d46a1c1f812250feffe194a7f1b2b2f2cc

The 2 pi removed in an earlier update from the diffusion equation was indeed neccessary and is now added back: In mrzero, gradients are typically specified in rotations / meter or rotations / FOV, but for diffusion we integrate over gauss * exp(-ikr), where kr is assumed to be a phase, so we must convert into rad / meter first. This is also visible in the signal equation, where the two pi was always written out for gradient and B0 dephasing.