Phase vs freq encoding

[AndrewBworth]

Yes it can. I've been thinking about this a bit, but I haven't sat down to do the math, there is probably a good reason for it. But if anyone would like to go ahead here it is:

To assign isotropic voxels a unique frequency in one shot, your gradient strengths would be, in whatever order makes the most sense - Gz:Gy:Gx = FOVz:FOVy:FOVx. Now the resolution of your Fourier transform is going to be 1/N*dt or 1/T one over total sampling time. Strongest gradient I have ever heard of is 300 mT/m, I think that is the record. Lastly your signal strength due to gradient dephasing is going to be I think
sinc(gammaH*Gz*FOVz/2) * t)sinc(gammaH*Gy*FOVy/2 * t)*sinc(gammaH*Gx*FOVx/2 * t).
Keep in mind T2 and T2* and see what is feasible.

(11-04-2015 07:32 AM)univox_high_flyer Wrote:  Hi,

I was wondering why phase encoding requires many gradient strengths while frequency encoding only one. Why not the other way round?
Can't a single phase encoding gradient provide a unique phase for all the spins in the sample?
Not sure if I'm missing something obvious here.

Thanks!