echo planar imaging
Ultrafast MRI acquisition technique that fills k-space using multiple gradient echoes after a single RF excitation, enabling rapid image acquisition.
Full Definition
Echo planar imaging (EPI) is a rapid MRI acquisition strategy that dramatically reduces scan time by collecting multiple lines of k-space data following a single radiofrequency excitation pulse. The technique uses rapidly switched readout gradients to generate a train of gradient echoes, each encoding a different phase-encoding step. This allows entire images to be acquired in tens of milliseconds rather than minutes. EPI is essential for diffusion-weighted imaging, functional MRI, and perfusion imaging where temporal resolution is critical. However, the technique is sensitive to magnetic field inhomogeneities and susceptibility artifacts, particularly near air-tissue interfaces and requires careful optimization of imaging parameters.
Usage
Usage note: EPI is acceptable after first mention; distinguish from EPI sequence which is already excluded.
In Context
- "Echo planar imaging enabled whole-brain diffusion tensor acquisition in under three minutes." — Research protocol description
- "The functional MRI study utilized single-shot echo planar imaging with 2-second temporal resolution." — fMRI methodology