Echoplanar Sequences
The Common Vein Copyright 2010
Introduction
Echo planar sequences are also based on the gradient echo technique. Multiple echoes are obtained, each having different phase encodings. After the RF pulse is applied, a dephasing gradient is applied while the image from the first RF is obtained. The dephasing process is reversed by applying a readout gradient with an opposite polarity. This results in a gradient echo. Repeating this process generates a train of echoes. Eventually, the signal intensity will fall to zero because of T2 and T2* effects.
Thus being, this sequence is characterized by high time efficient resolution, since a single excitation acquires a complete image.
It is mainly used for functional magnetic resonance imaging and cardiac imaging. It is prone to severe artifacts however.