Gradient amplifier system and control method thereof

Abstract

A gradient amplifier system comprises a power level, a gradient coil and a controller level, wherein the power level comprises a plurality of bridge amplifiers which are operated at first switching frequency, the gradient coil is coupled to the power level and configured to generate a magnetic field which is proportional to coil current signals supplied by the power level, and the controller level is coupled to the input end of the power level and configured to generate gating signals of the pulse width modulation on basis of the coil current signals and reference current signals. When the conversion rate which is relative to the reference current signals and occurs in at least a first time period is lower than the preset threshold rate, the gating signals of the pulse width modulation are generated at second switching frequency, and the generated gating signals of the pulse width modulation are applied to the power level to switch the operating frequency of every bridge amplifier from the first switching frequency to the second switching frequency.

Description

technical field [0001] The invention relates to a magnetic resonance imaging (MRI) system, in particular to a gradient amplifier system used in the MRI system and a control method thereof. Background technique [0002] In only a few decades, the use of Magnetic Resonance Imaging (MRI) scanners has grown enormously. MRI scans are increasingly being used to aid in the diagnosis of multiple sclerosis, brain tumors, torn ligaments, tendinitis, cancer, stroke, and more. MRI is a non-invasive medical testing technique that assists physicians in the diagnosis and treatment of various medical conditions. The enhanced contrast provided by MRI scans between the different soft tissues of the body allows doctors to better evaluate parts of the body and determine the presence of certain diseases that may not be available using methods such as x-rays, ultrasound, or computed tomography (CT) to adequately assess other single imaging methods. [0003] Typically, conventional MRI systems ...

AI Technical Summary

Problems solved by technology

However, in conventional gradient amplifier systems, each of the bridges has a different direct current (DC) link voltage and a different voltage command, which causes each bridge to apply a different switching frequency

Since each bridge operates at a different switching frequency with a different DC link voltage, there is considerable power loss in the gradient amplifier system

Also, when low voltages are desired across the gradient coils, power losses increase

In addition, the power loss is unevenly distributed across the bridges and the loading on each bridge is different, which results in a large thermal stress on the gradient amplifier

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