CN-121995284-A - Magnetic resonance imaging system, high-frequency power distribution unit and gradient amplifier

CN121995284ACN 121995284 ACN121995284 ACN 121995284ACN-121995284-A

Abstract

The invention relates to a magnetic resonance imaging system, a high-frequency power distribution unit and a gradient amplifier. Power systems and circuits for generating gradient magnetic fields in a Magnetic Resonance Imaging (MRI) system are discussed herein. Embodiments provide a magnetic resonance imaging system, a high frequency power distribution unit and a gradient amplifier, which may include the use of multiple gradient amplifiers sharing a high frequency power distribution unit, which may play the role of power distribution as well as a power supply. The high frequency power distribution unit may allow multiple gradient amplifiers to be driven using a single power supply via a shared power bus. Gradient amplifiers may use modern semiconductor materials that provide high frequency, high voltage performance, and may be implemented by using a single semiconductor bridge.

Inventors

V. Kanakasabai
J. Ganash
J.A. Sabat

Assignees

通用电气精准医疗有限责任公司

Dates

Publication Date: 20260508
Application Date: 20190219
Priority Date: 20180221

Claims (14)

1. A magnetic resonance imaging system comprising: A plurality of gradient coils, and A gradient driver configured to drive the plurality of gradient coils, the gradient driver comprising: A plurality of gradient amplifiers, wherein each gradient amplifier of the plurality of gradient amplifiers is electrically coupled to a gradient coil of the plurality of gradient coils, and wherein each gradient amplifier comprises a respective single semiconductor bridge, and A high frequency power distribution unit configured to receive an AC power signal from a main power supply of the magnetic resonance imaging system and to generate a DC power signal to the plurality of gradient amplifiers via a shared DC bus, the shared DC bus comprising a first terminal and a second terminal, wherein the high frequency power distribution unit comprises: A power distribution unit that receives the AC power signal from the main power source and generates an intermediate power signal; A power supply that receives the intermediate power signal from the power distribution unit and provides the DC power signal to the shared DC bus, wherein the power supply comprises a single capacitor bank having two ends connected to a first terminal and a second terminal of the shared DC bus, respectively, and a ground Y-capacitance circuit configured to be coupled to a safety ground of the magnetic resonance imaging system, wherein the safety ground is added to a midpoint of the ground Y-capacitance circuit, the ground Y-capacitance circuit comprising a first capacitance and a second capacitance, the first capacitance being connected between the first terminal of the shared DC bus and the safety ground, and the second capacitance being connected between the second terminal of the shared DC bus and the safety ground.
2. The magnetic resonance imaging system of claim 1, wherein the plurality of gradient coils includes an axial gradient coil, a longitudinal gradient coil, and a transverse gradient coil.
3. The magnetic resonance imaging system of claim 2, wherein the plurality of gradient amplifiers includes a first gradient amplifier electrically coupled to the axial gradient coil, a second gradient amplifier electrically coupled to the longitudinal gradient coil, and a third gradient amplifier electrically coupled to the transverse gradient coil.
4. The magnetic resonance imaging system of claim 1, wherein each respective single semiconductor bridge of each gradient amplifier comprises a respective first leg comprising a first pair of switches and a respective second leg comprising a second pair of switches.
5. The magnetic resonance imaging system of claim 4, wherein each switch of the first and second pairs of switches comprises a high voltage wide bandgap device.
6. The magnetic resonance imaging system of claim 5, wherein the high voltage wide bandgap device comprises a silicon carbide device.
7. The magnetic resonance imaging system of claim 1, wherein the magnetic resonance imaging power supply comprises a transformer configured to isolate the intermediate power signal from the DC power signal.
8. The magnetic resonance imaging system of claim 7, wherein the shield of the transformer is electrically coupled to a ground of the magnetic resonance imaging system.
9. The magnetic resonance imaging system of claim 1, wherein the magnetic resonance imaging system comprises a scan room and a device room, wherein the HFPDU is disposed in the device room, and wherein the plurality of gradient amplifiers are disposed in the scan room.
10. The magnetic resonance imaging system of claim 1, wherein the magnetic resonance imaging system comprises a first package comprising the plurality of gradient amplifiers.
11. The magnetic resonance imaging system of claim 10, wherein the first package includes the HFPDU.
12. The magnetic resonance imaging system of claim 1, wherein the magnetic resonance imaging system comprises a plurality of packages, and wherein each package comprises a respective gradient amplifier.
13. A high frequency power distribution unit comprising: a power distribution unit comprising a line filter and a first rectifier, wherein the power distribution unit is configured to receive a three-phase AC power signal from a main power source and to generate an intermediate DC power signal, and A power supply comprising a semiconductor bridge, a high frequency transformer, a high speed rectifier and a filter, wherein the power supply is configured to receive the intermediate DC power signal, to generate a high frequency second AC power signal using the semiconductor bridge, and to generate an output DC power signal isolated from the second AC power signal using the high frequency transformer, the high speed rectifier and the filter, wherein a shield of the high frequency transformer is electrically coupled to a ground connection point, wherein the power supply comprises a single capacitor bank and a ground Y-capacitor circuit, both ends of the single capacitor bank being connected to a first terminal and a second terminal of the shared DC bus, respectively, the ground Y-capacitor circuit being configured to be coupled to a safety ground, the power supply being configured to provide the output DC power signal to a shared DC bus to a plurality of gradient amplifiers of a magnetic resonance imaging system, wherein the shared DC bus comprises a first terminal and a second terminal, the safety ground being added to the midpoint ground Y-capacitor circuit, the ground Y-capacitor circuit comprising a first terminal and a second terminal, the safety ground, the ground connection between the first and second terminal of the ground capacitor, the safety connection to the first and the DC bus.
14. The high frequency power distribution unit of claim 13, wherein the three AC power signals comprise a nominal voltage comprising 380V, 415V, or 480V and a nominal frequency comprising 50Hz or 60Hz, and wherein the output DC power signal is between 350V and 2 kV.

Description

Magnetic resonance imaging system, high-frequency power distribution unit and gradient amplifier The application is a divisional application with the application date of '2019, 2 months and 19 days', the application number of '201910124415.2', and the title of 'magnetic resonance imaging system, high-frequency power distribution unit and gradient amplifier'. Technical Field The subject matter disclosed herein relates to Magnetic Resonance Imaging (MRI) devices, and more particularly to systems that provide accurate high power currents, for example, to drive gradient coils. Background This section is intended to introduce the reader to various aspects of art that may be related to various aspects of the present disclosure, which are described and/or claimed below. This discussion is believed to be helpful in providing the reader with background information to facilitate a better understanding of the various aspects of the present disclosure. Accordingly, it should be understood that these statements are to be read in this light, and not as admissions of prior art. Magnetic Resonance Imaging (MRI) is an imaging modality that is commonly used to generate images (e.g., spatial maps) based on the distribution of molecules in a subject. In general, an MRI image of an object (e.g., a patient) is generated by measuring properties of gyromagnetic material of the object, such as hydrogen nuclei. These properties are typically obtained by measuring the emission of spin-magnetic material in a subject in response to excitation from an applied electric field. The magnetic field used for excitation generally comprises a strong main magnetic field, magnetic field gradients, and Radio Frequency (RF) magnetic field excitation pulses. Note that the magnetic field gradients may be used by the MRI system to provide spatial encoding of acquired data. To this end, gradient coils may be used to generate spatial gradients of the magnetic field so that spatial coordinates of the object may be correlated with the locally encoded magnetic field values. As a result of this magnetic field based encoding, the emission of spin magnetic material may contain information that may be used to inform the spatial origin of a particular emission during image reconstruction. The magnetic field gradient may be obtained by driving a specific current to the gradient coils. More specifically, these magnetic field gradients can be controlled by modulation of currents in gradient coils that are responsible for generating the magnetic field. Magnetic coils may be associated with each of the spatial, x, y, and z axes, and the current in each axis coil may be independently controlled during the data acquisition process to obtain a variable three-dimensional slice of the image. To generate a current in the magnetic coil, a magnetic coil driver may be used. The magnetic coil driver may include a gradient power supply capable of inducing a current in the magnetic coil and a gradient amplifier (e.g., a current amplifier). The magnetic coil driver may require very accurate currents for accurate, high resolution spatial encoding. In addition, the current and the voltage required to drive the current in the magnetic coil can be very large and vary. Thus, the design of power supplies in these systems can be particularly challenging due to the large current variations and large voltages typically used by amplifiers. Disclosure of Invention Certain embodiments commensurate in scope with the previously claimed invention are summarized as follows. These embodiments are not intended to limit the scope of the claimed invention, but rather these embodiments are intended to provide a brief summary of possible forms of the invention. Indeed, the invention may encompass a variety of forms similar to or different from the embodiments set forth below. In one embodiment, a Magnetic Resonance Imaging (MRI) system is described. An MRI system may include a plurality of gradient coils and a gradient driver that drives the gradient coils. The gradient driver may comprise a plurality of gradient amplifiers, and each gradient amplifier may independently control the gradient coils by electrical coupling. Furthermore, each gradient amplifier employs a single semiconductor bridge to perform control. The gradient driver also includes a Power Distribution Unit (PDU). The PDU may receive an Alternating Current (AC) power signal from a main power supply of the MRI system and provide a direct current power signal to the gradient amplifier via a Direct Current (DC) bus. In another embodiment, a High Frequency Power Distribution Unit (HFPDU) is described. HFPDU may include a power distribution unit and a power supply. The power distribution unit may have a line filter and a first rectifier. The power distribution unit may receive a three-phase AC power signal from a power source and generate an intermediate DC signal. The power supply includes a semiconductor bridge, a high frequency transform