JPH06404U - Gradient power supply for MR device - Google Patents

Abstract

(57) [Summary] [Objective] To provide a gradient power supply for an MR device that achieves both a high SN ratio and high efficiency. [Configuration] PWM circuits 4 and 6 that drive the transistors QP and QN in a switching system, bias circuits 3 and 5 that drive the transistors QP and QN in an analog system, and a gradient that directly acts on the resonance nucleus in the pulse sequence of MRI. The PWM circuits 4 and 6 drive the transistors QP and QN at the timing of generating the magnetic field, and the bias circuits 3 and 5 drive the transistors QP and QN at the timing of generating the gradient magnetic field used for reading the high-frequency signal from the resonance nucleus. And a switching control circuit 2 for switching modes. [Effect] A high SN ratio and high efficiency can both be achieved.

Description

[Detailed description of the device]

[0001]

[Industrial applications]

 The present invention relates to a gradient power supply for MR devices, and more particularly to a gradient power supply for MR devices that achieves both a high SN ratio and high efficiency.

[0002]

[Prior art]

 FIG. 3 is an explanatory diagram of an example of an MRI pulse sequence using multiple echoes. The slice axis, the warp axis, and the lead axis are the gradient magnetic field.

FIG. 4 shows an example of a conventional gradient power supply for an MR device of a switching system. In the gradient power supply 51 for the MR device, the PWM circuits 4 and 6 drive the drive signals D corresponding to the pulse sequence of the MRI from a sequence controller (not shown) of the MR device in the ready state. The transistors QP and QN are switching-driven based on the signal D. As a result, power is supplied to the gradient coil G and a gradient magnetic field is generated. The gradient coil current detection resistor r detects the gradient coil current and sends a feedback signal FB to the PWM circuits 4 and 6.

The AND circuits AP and AN are controlled by blanking signals C1 and C2 from the switching control circuit 52, and perform blanking so that the transistors QP and QN are not turned on at the same time. The switching control circuit 52 sends the activate signals T2 and T4 based on the command signal given from the sequence controller of the MR device to put the PWM circuits 4 and 6 into the ready state or release the ready state.

For example, when the gradient magnetic field of the lead axis shown in FIG. 3 is generated, the sequence controller of the MR device sets the PWM circuits 4 and 6 in a ready state by a command signal, and then a drive signal as shown in FIG. give.

FIG. 6 shows an example of a conventional analog type gradient power supply for an MR device. In the gradient power supply 61 for MR device, when the bias circuits 3 and 5 are in the ready state, when the drive signal D corresponding to the pulse sequence of MRI is given from the sequence controller (not shown) of the MR device, the drive signal Based on D, the transistors QP and QN are driven by DC amplification. As a result, power is supplied to the gradient coil G and a gradient magnetic field is generated. The gradient coil current detection resistor r detects the gradient coil current and sends a feedback signal FB to the bias circuits 4 and 6.

The switching control circuit 62 sends the activate signals T1 and T3 based on a command signal given from the sequence controller of the MR device to put the bias circuits 3 and 5 into a ready state or release the ready state.

For example, when the gradient magnetic field of the lead axis shown in FIG. 3 is generated, the sequence controller of the MR device sets the bias circuits 3 and 5 in the ready state by the command signal, and then the drive signal shown in FIG. give.

[0009]

[Problems to be solved by the device]

 Since the gradient power supply 51 for MR device of the conventional switching system is a switching system, it can supply a large amount of electric power with high efficiency and generate a strong magnetic field. However, since the noise is large, there is a problem that when the gradient magnetic field used for reading the high frequency signal from the resonance nucleus is generated (β in FIG. 3), the SN ratio is lowered. On the other hand, since the conventional gradient power source 61 for an MR apparatus of the analog type is an analog type, it has less noise and can read a high frequency signal from the resonance nucleus with a high SN ratio. However, there is a problem in that efficiency is reduced because the extra power is consumed by heat. Therefore, an object of this invention is to provide a gradient power supply for an MR device that can achieve both a high SN ratio and high efficiency.

[0010]

[Means for Solving the Problems]

 The gradient power supply for MR device of the present invention controls the transistor based on the drive signal supplied corresponding to the pulse sequence of MRI, and supplies the power to the gradient coil in the gradient power supply for MR device. A switching control circuit for driving, an analog control circuit for driving a transistor in an analog system, and a timing for determining the timing of the pulse sequence of MRI and generating a gradient magnetic field that directly acts on the resonance nucleus are used by the switching control circuit. And a drive mode switching means for switching the drive mode of the transistor so as to drive the transistor by the analog control circuit at the timing of generating a gradient magnetic field used to read the high frequency signal from the resonance nucleus. upper It is an butterfly.

[0011]

[Action]

 The gradient power supply for MR device of the present invention includes both a switching control circuit for driving a transistor in a switching system and an analog control circuit for driving a transistor in an analog system. The drive mode switching means drives the transistor by the switching control circuit at the timing of generating the gradient magnetic field that directly acts on the resonance nucleus. At this timing, it is necessary to supply a large amount of power to the gradient coil in order to generate a strong magnetic field, but due to the switching method, a large amount of power can be supplied with high efficiency. Although it has a lot of noise, it does not cause any particular problem because high-frequency signals are not read out. Further, the drive mode switching means drives the transistor by the analog control circuit at the timing of generating the gradient magnetic field used for reading the high frequency signal from the resonance nucleus. At this timing, low noise is required to read a weak high-frequency signal, but since it is an analog method, there is little noise and a high SN ratio can be achieved. Although the efficiency decreases at this timing, the efficiency is high at the above timing, so the efficiency can be improved as a whole. Thus, both high SN ratio and high efficiency can be achieved.

[0012]

【Example】

 Hereinafter, the present invention will be described in more detail with reference to the embodiments shown in the drawings. However, this does not limit the present invention. FIG. 1 is a circuit diagram of a gradient power supply 1 for a dual MR device according to an embodiment of the present invention. In the ready state, the PWM circuits 4 and 6 switch drive the transistors QP and QN based on the drive signal D when the drive signal D corresponding to the MRI pulse sequence is given from the sequence controller of the MR device. The drive pulse to output is output.

When the drive signal D is given from the sequence controller of the MR device in the ready state, the bias circuits 3 and 5 drive the transistors QP and QN by DC amplification based on the drive signal D. Output the bias signal of.

The gradient coil current detection resistor r detects the gradient coil current and sends a feedback signal FB to the PWM circuits 4 and 6 and the bias circuits 3 and 5. The AND circuits AP and AN are controlled by the blanking signals C1 and C2 from the switching control circuit 2 and perform blanking so that the transistors QP and QN are not turned on at the same time.

The switching control circuit 2 sends the activate signals T1, T2, T3, T4 based on the command signal given from the sequence controller of the MR device to turn on the PWM circuits 4, 6 and the bias circuits 3, 5. Enters the ready state or releases the ready state. Further, the switching control circuit 2 compares the drive signal D with the switching level h as shown in FIG. The switching level h is set according to the level of the drive signal D corresponding to the gradient magnetic field used for reading the high frequency signal from the resonance nucleus. When D> h, the activate signals T1, T2, T3 and T4 bring the PWM circuits 4 and 6 into the ready state and release the bias circuits 3 and 5 from the ready state. As a result, the transistors QP and QN are switching-driven in the PWM mode, power is supplied to the gradient coil G, and a gradient magnetic field that directly acts on the resonance nucleus is generated. On the other hand, when D ≦ h, the ready states of the PWM circuits 4 and 6 are released and the bias circuits 3 and 5 are placed into the ready state by the activate signals T1, T2, T3 and T4. As a result, the transistors QP and QN are analog-driven in the analog mode, power is supplied to the gradient coil G, and a gradient magnetic field used for reading the high-frequency signal from the resonance nucleus is generated.

In the above embodiment, the switching control circuit 2 corresponds to the drive mode switching means, but the PWM circuits 4 and 6 and the bias circuits 3 and 5 may have the same function. Further, in the above embodiment, two transistors QP and QN are used, but the invention can be similarly applied to the case where four transistors are used as a bridge.

[0017]

[Effect of device]

 According to the gradient power source for MR device of the present invention, the transistor is driven by the switching method at the timing of generating the gradient magnetic field directly acting on the resonance nucleus, and the gradient magnetic field used for reading the high frequency signal from the resonance nucleus is generated. Since the transistor is driven by the analog method, it is possible to achieve both a high SN ratio and high efficiency.

[Brief description of drawings]

FIG. 1 is a circuit diagram of an embodiment of a gradient power supply for MR device of the present invention.

FIG. 2 is an exemplary diagram of drive signals and switching levels.

FIG. 3 is an exemplary diagram of a pulse sequence of MRI.

FIG. 4 is a circuit diagram of an example of a conventional gradient power supply for an MR device.

FIG. 5 is an exemplary diagram of a drive signal.

FIG. 6 is a circuit diagram of another example of a conventional gradient power supply for an MR device.

[Explanation of symbols]

 1 MR device gradient power supply 2 Switching control circuit 3,5 Bias circuit 4,6 PWM circuit QP, QN transistor AP, AN AND circuit G Gradient coil r Gradient coil current detection resistance

Claims (1)

[Scope of utility model registration request] 1. A gradient power supply for an MR device for controlling a transistor based on a drive signal supplied corresponding to a pulse sequence of MRI to supply electric power to a gradient coil. A switching control circuit for driving a transistor by a switching method. And an analog control circuit for driving a transistor in an analog system, and the timing of determining the pulse sequence of MRI and generating a gradient magnetic field that directly acts on the resonance nucleus. A gradient power supply for an MR device, comprising: a drive mode switching means for switching a drive mode of the transistor by the analog control circuit at a timing of generating a gradient magnetic field used for reading a high frequency signal.