In-phase and out-of-phase

In-phase (IP) and out-of-phase (OOP) sequences correspond to paired MRI gradient echo (GRE) sequences obtained with the same repetition time (TR) but with two different echo time (TE) values.

Applications

The main application of the IP-OOP sequences is to identify pathological (microscopic) fat content of tissues in the abdomen by showing signal intensities drop on the OOP images compared to the IP images. Loss of signal intensity between the in-phase and out-of-phase MR images indicates fat. Examples where IP-OOP sequences are useful include :