The time linearly from 0 to its maximum flat top measured in mT/m or G/cm. 10 mT/m=1G/cm. The height of the flat top influences the FOV. The higher the flat top or maximum gradient amplitude the smaller the FOV and the thinner the available slice thickness.

The gradient slew rate is the speed rate of ascent or descent of a gradient from zero to its maximum amplitude, either positive or negative. Which is the amplitude divided by the rise time in msec. Measured in mT/m/msec or T/m/sec. The shorter the rise time, the faster the gradients and therefore echo spacing. Gradients with a shorter echo spacing will have a better resolution and more slices per TR.

Echo spacing is the distance in time between the echoes in multiple echo sequences like, e.g. echo planar imaging, fast spin echo. A short echo space produces compact sequence timing and less image artifacts. The shorter the rise time, the faster the gradients and therefore the echo spacing. Gradients with a shorter echo spacing will have a better resolution and more slices per TR.

See also Fast Spin Echo.

From Siemens Medical Systems;
Received FDA clearance in 2007.
The MAGNETOM Essenza is designed to combine high system performance with simple installation and power requirements to provide optimal operating costs for limited budgets. The standard system has up to 25 integrated coil elements and 8 independent radio frequency channels. Tim allows the combination of up to 4 different coils that reduce patient and coil repositioning.
The 1.5 Tesla system is designated for a complete range of clinical applications, including neurology, orthopedics, body imaging, angiography, cardiology, breast imaging, oncology and pediatric MRI.

(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.