Echo Planar Imaging - Video Lesson

Hey, everybody. Welcome to today's lesson on pulse sequence. This lesson focuses on echo planar imaging or EPI and discusses the mechanisms behind EPI, its uses, as well as the advantages and disadvantages of this type of pulse sequence. Understanding the mechanics of echo planar imaging will help in determining when to use this pulse sequence. Let's get started. Echo planar imaging or EPI is a rapid MRI technique that allows the acquisition of an entire slice in as little as twenty milliseconds. This is achieved by generating a train of gradient echoes through the use of the frequency encoding gradient after the RF excitation pulse, so we gather more data in a single TR. In order to perform an EPI, we apply an RF excitation pulse. If we use a ninety degree RF excitation pulse and a one hundred eighty degree rephrasing pulse followed by a train of gradient echoes, we are performing a spin echo EPI.