suppression vs saturation

[fungfung310@gmail.com]

HI,

I am reading journals about ASL and I always encounter these two terms, "saturation" and "suppression"

For Example, pre-labelling saturation and background suppression

I would like to know the differences between this two terms.
For my understanding, If I would like to "suppress" the fat signals, I could excite those spins by 90 , then using spoiler to "saturate" those spins ( dephasing ). So technically they are the same ?

Agian, thanks for everyone

[aelster]

Signal from a tissue (such as fat) can be suppressed several techniques, of which saturation is only one method.

Saturation typically involves applying a radiofrequency pulse at the resonance frequency of the tissue you wish to suppress ("fat sat pulse").

However, fat can also be suppressed on a STIR sequence, for example, by inverting its magnetization and then imaging at a specific time (TI) to catch the fat when it goes through zero and has no signal. This is fat suppression without saturation. An opposed phase method such as the Dixon technique is another method of fat suppression without saturation.