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TECHNIQUE FOR DYNAMIC ADJUSTMENT OF SLEW RATE IN A MAGNETIC RESONANCE IMAGING (MRI) SYSTEM

IP.com Disclosure Number: IPCOM000245650D
Publication Date: 2016-Mar-24
Document File: 3 page(s) / 86K

Publishing Venue

The IP.com Prior Art Database

Abstract

A technique for achieving faster slew rate (SR) for low amplitude gradient segments in an MRI system is disclosed. The technique includes dynamically adjusting slew rate of individual gradient segments beyond the full amplitude slew rate limit by tapping into gradient amplifier capabilities available at lower currents. If the current demand of a gradient segment is significantly lower than peak current, resistive voltage losses are significantly less. Such excess voltage is available and is used for faster ramping or slewing.

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TECHNIQUE FOR DYNAMIC ADJUSTMENT OF SLEW RATE IN A MAGNETIC RESONANCE IMAGING (MRI) SYSTEM

BACKGROUND

 

The present disclosure relates generally to magnetic resonance imaging (MRI) and more particularly to a technique for dynamic adjustment of slew rate in the MRI system.

Gradient performance in an MRI system is characterized by the amplitude and slew rate that can be achieved. Further, since the slew rate that can be achieved is dependent on gradient amplitude, the slew rate is typically specified at maximum gradient amplitude i.e. at peak current. Conventionally, pulse sequences are designed using a single maximum slew rate, the slew rate at the maximum gradient amplitude, regardless of amplitude of individual gradient segments.

In instances where, peripheral nerve stimulation is not a constraint, the conventional design is sub-optimal for low amplitude gradient segments such as, slice selection gradients and readout amplitude of diffusion application for low resolution.

Different gradient performance for different types of pulses may be achieved by using two distinct hardware having two different configuration modes, for example, 8 G/cm and 100 T/m/s for mode 1 and 4 G/cm & 200 T/m/s for mode 2. Alternatively, a software application to provide different gradient performance limits overall performance of the MRI system, since the software selects the configurations on a sequence by sequence basis instead of optimizing for each pulse individually.

It would be desirable to have a technique for achieving faster slew rate for low amplitude gradient segments in an MRI system.

BRIEF DESCRIPTION OF DRAWINGS

Figure 1 depicts an opportunity area where current demand of a gradient segment is significantly lower than peak current and resistive voltage losses are significantly less.

Figure 2 is a graphical representation of gradient corner point for abdomen diffusion weighted imaging (DWI) with amplitude of 7.0 G/cm and slew rate of 150.

DETAILED DESCRIPTION

A technique for achieving faster slew rate (SR) for low amplitude gradient segments in an MRI system is disclosed. The technique includes dynamically adjusting slew rate of individual gradient segments beyond the full amplitude slew rate limit by tapping into gradient amplifier capabilities available at lower currents.

Slew rate capability of hardware is driven by voltage output of the gradient driver. The gradient driver provides voltage required to overcome gradient coil inductance as well as resistive losses in the gradient coil and other components. If the current demand of a gradient segment is significantly lower than peak current, resistiv...