Ernst angle

Last revised by Jeremy Jones on 19 Sep 2021

The Ernst angle is the flip angle that maximizes signal in T1-weighted sequences that have a short repetition time (TR).

When the TR is very short, the best flip angle to maximize signal can be quite small. Choosing the Ernst angle in this setting can increase signal by several fold. However, it should be remembered that depending on the situation, we may choose a non optimal flip angle to sacrifice maximal signal for better T1 contrast.

In T2-weighted sequences, a non optimal flip angle may be deliberately chosen to decrease T1 signal.

Adjusting the TR and flip angle toward or away from the Ernst angle is often a concern in MR angiography.

History and etymology

Richard Robert Ernst (fl. 2020) is a Swiss physical chemist who won the Nobel Prize for Chemistry in 1991 for his work on nuclear magnetic resonance (NMR) 4,5.

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