Phase vs freq encoding

[AndrewBworth]

(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!

Oh geez, sorry. Yes, in THEORY one gradient set can provide unique frequencies to every voxel. But unfortunately, all the different frequencies rapidly add up to zero (Dephasing), so you can't acquire this signal for very long. However - this is a problem worth thinking hard about and looking into - It will teach you a lot about MRI.