(EPI) Echo planar imaging is one of the early magnetic resonance imaging sequences (also known as Intascan), used in applications like diffusion, perfusion, and functional magnetic resonance imaging. Other sequences acquire one k-space line at each phase encoding step. When the echo planar imaging acquisition strategy is used, the complete image is formed from a single data sample (all k-space lines are measured in one repetition time) of a gradient echo or spin echo sequence (see single shot technique) with an acquisition time of about 20 to 100 ms. The pulse sequence timing diagram illustrates an echo planar imaging sequence from spin echo type with eight echo train pulses. (See also Pulse Sequence Timing Diagram, for a description of the components.)
In case of a gradient echo based EPI sequence the initial part is very similar to a standard gradient echo sequence. By periodically fast reversing the readout or frequency encoding gradient, a train of echoes is generated.
EPI requires higher performance from the MRI scanner like much larger gradient amplitudes. The scan time is dependent on the spatial resolution required, the strength of the applied gradient fields and the time the machine needs to ramp the gradients.
In EPI, there is water fat shift in the phase encoding direction due to phase accumulations. To minimize water fat shift (WFS) in the phase direction fat suppression and a wide bandwidth (BW) are selected. On a typical EPI sequence, there is virtually no time at all for the flat top of the gradient waveform. The problem is solved by "ramp sampling" through most of the rise and fall time to improve image resolution.
The benefits of the fast imaging time are not without cost. EPI is relatively demanding on the scanner hardware, in particular on gradient strengths, gradient switching times, and receiver bandwidth. In addition, EPI is extremely sensitive to image artifacts and distortions.

From GE Healthcare;
The GE Signa HDx MRI system is a whole body magnetic resonance scanner designed to support high resolution, high signal to noise ratio, and short scan times.
The 1.5T Signa HDx MR Systems is a modification of the currently marketed GE 1.5T machines, with the main difference being the change to the receive chain architecture that includes a thirty two independent receive channels, and allows for future expansion in 16 channel increments. The overall system has been improved with a simplified user interface and a single 23" liquid crystal display, improved multi channel surface coil connectivity, and an improved image reconstruction architecture known as the Volume Recon Engine (VRE).

From GE Healthcare;
the Signa Infinity Magnetic Resonance system is a short bore, high performance, whole-body imaging system operating at 1.0 Tesla. The system can image in any orthogonal or oblique plane (including single and double axis oblique), using a wide variety of pulse sequences.

The company is a leading manufacturer and developer of magnetic resonance imaging (MRI) scanners. The Patient Friendly MRI Company, formed in 1978, is engaged in the business of inventing, manufacturing, selling and servicing magnetic resonance imaging (MRI) scanners. FONAR is the oldest MRI company in the world. After receiving hundreds of millions in a windfall from protecting their MRI patents, they made a MRI scanner that no other MRI manufacturer has. One that the patient stands in and they call Indomitable, the Stand-Up MRI. Patients like it because it is the least claustrophobic, most comfortable MRI on the market. Doctors like it because of its superior image quality and for the first time, the patient can be scanned in the weight-bearing position, or the position of pain or symptom. In October of 2004, the company changed the product name of the Stand-Up MRI to the Upright MRI. Fonar introduced the first "open" MRI scanner in 1980 and is the originator of the iron-core nonsuperconductive and permanent magnet technology.

MRI Scanners:

- 0.6T: