JP3170359B2 - Sequence controller - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sequence controller for controlling the operation of a controlled device such as a gradient magnetic field generator in a nuclear magnetic resonance imaging apparatus according to a predetermined processing procedure.

[0002]

2. Description of the Related Art A gradient magnetic field generator in a nuclear magnetic resonance imaging apparatus is controlled by a sequence controller. The above-described nuclear magnetic resonance imaging apparatus replaces an X-ray CT apparatus or an ultrasonic imaging apparatus as a device for nondestructively inspecting the internal structure of the human body such as the head and abdomen.
It has been widely used. This nuclear magnetic resonance imaging apparatus uses a nuclear magnetic resonance phenomenon, and an X-ray CT
And various types of information that could not be obtained with an ultrasonic imaging apparatus.

First, the basic principle of the nuclear magnetic resonance phenomenon will be briefly described below. The nucleus is composed of protons and neutrons, and is considered to rotate as a whole with angular momentum I, that is, to perform nuclear spin. Here, let us consider hydrogen nucleus. The hydrogen nucleus is composed of one proton, and rotates by a spin quantum number 1/2. Since protons have a positive charge, a magnetic moment μ is generated as the nuclei rotate, and each nucleus can be considered as a very small magnet. For example, in a ferromagnetic material such as iron, since the directions of the magnets described above are aligned,
Magnetization occurs as a whole. On the other hand, in the case of hydrogen or the like, the directions of the above-mentioned magnets are different, and no magnetization occurs as a whole. ).

In the case of a hydrogen nucleus, the spin quantum number is 1
/ 2, it is divided into two energy levels of -1/2 and +1/2. The difference ΔE between the energy levels is
Generally, it is represented by the following equation (1). ΔE = γhH0 / 2π (1) where γ is the gyromagnetic ratio, h is Planck's constant, and H0 is the static magnetic field strength. By the way, in general, a static magnetic field H
Since a force of μ × H0 is applied by 0, the nucleus precesses around the axis of the static magnetic field at an angular velocity ω (Larmor angular velocity) represented by the following equation (2). ω = γH0 (2) An electromagnetic wave (RF wave) having an angular frequency ω is added to the system in such a state.
When a magnetic field is applied, a nuclear magnetic resonance phenomenon occurs. Generally, the nucleus absorbs energy corresponding to the energy difference ΔE represented by the formula (1), and transitions to a higher energy level.
At this time, even if a large number of various nuclei are present, not all nuclei cause a nuclear magnetic resonance phenomenon. This is because the gyromagnetic ratio γ is different for each nucleus.
Is different for each nucleus, and only certain nuclei corresponding to the applied frequency resonate.

[0005] Next, the nucleus that has been transitioned to a high level by the RF wave returns to the original level after a time determined by a certain time constant (called a relaxation time). At this time, a nuclear magnetic resonance signal having an angular frequency ω is emitted from the nucleus shifted to a high level by the RF wave. Here, the above-mentioned relaxation time is further divided into a spin-lattice relaxation time (longitudinal relaxation time) T1 and a spin-spin relaxation time (lateral relaxation time) T2. In general, in the case of a solid, the spin-spin relaxation time T2
Becomes shorter. In addition, since the absorbed energy is first transferred to the spin system and then to the lattice system, the spin-lattice relaxation time T1 has a much larger value than the spin-spin relaxation time T2. However, in the case of a liquid, spin-spin and spin-
The likelihood of lattice energy exchange is comparable.

[0006] The above-described phenomenon occurs not only with hydrogen nuclei but also with phosphorus nuclei, carbon nuclei, sodium nuclei, fluorine nuclei, oxygen nuclei, and the like. In the inspection apparatus using the nuclear magnetic resonance phenomenon based on the basic principle described above, it is necessary to separate and identify signals from the inspection object.One of them is to apply a gradient magnetic field to the inspection object and There is a method of obtaining position information by changing the placed magnetic field and then changing the resonance frequency of each part or the amount of phase encoding. The basic principle of this method is described in JP-A-55-20495, Journal of Magnetic Resonance (J. Mag).
n. Reson. ) Vol. 18, pp. 69-83 (1975)
Physics of Medicine and Biology (Phys. Med. & Biol.) Vol. 25, No. 7
Since it is described on pages 51 to 756 (1980), detailed description is omitted.

The nuclear magnetic resonance imaging apparatus is configured to obtain a tomographic image of a subject by using the above-described nuclear magnetic resonance phenomenon. FIG. 5 is a schematic configuration diagram of a sequence control device 60 used in a nuclear magnetic resonance imaging apparatus. In FIG. 5, the operator instructs a console (not shown) to start diagnosis. Then, a signal indicating the start of diagnosis is supplied to the CPU 64 via the interface bus 65. In response to the supplied diagnosis start signal, the CPU 64 instructs the start processing control unit 52 via the interface bus 65 to start diagnosis. Then, the activation processing control unit 52 activates the microprogram sequencer 51 via the internal interface bus 59. The microprogram sequencer 51 retrieves a sequence procedure from the microprogram storage unit 53, and performs operation control according to the retrieved sequence procedure. Then, the microprogram sequencer 51 supplies a command signal to the RF waveform output unit 57 and the gradient magnetic field waveform output unit 58. Then, the RF waveform output unit 57 supplies a command signal to an RF control device (not shown). Further, the gradient magnetic field waveform output unit 58 supplies, for example, a waveform command signal as shown in FIG. 6 to a gradient magnetic field generator (not shown). That is, the waveform command signal shown in FIG. 6 changes from the gradient magnetic field output initial value a to b at time t1, and changes from the gradient magnetic field output value b to c at time t2 after a predetermined time has elapsed. The gradient magnetic field generator generates a gradient magnetic field with a gradient coil according to such a waveform command signal.

Incidentally, examples similar to the above-described nuclear magnetic resonance imaging apparatus are disclosed in JP-A-62-240039, JP-A-3-106339, and JP-A-3-109.
No. 047 is disclosed.

[0009]

In the above-described sequence control apparatus, particularly, in the sequence control apparatus 60 applied to a nuclear magnetic resonance imaging apparatus, the sequence control apparatus is controlled in order to improve the sharpness of an obtained image. As the gradient magnetic field generator performs the optimal operation,
It is desired to be finely controlled.

In order for the gradient magnetic field generator to be finely controlled, it is necessary to finely control the shape of the waveform of the waveform command signal from the gradient magnetic field waveform output unit 58. Then, if the shape of the waveform command signal is finely controlled to improve the gradient magnetic field waveform and the position information of the subject to be fine, the sharpness of the obtained image can be improved. Therefore, in the conventional sequence controller 60, the control operation of the microprogram sequencer 51 is increased and the gradient magnetic field waveform output unit 58
It is conceivable to configure such that a command signal to the device can be finely controlled.

However, the microprogram sequencer 51 controls the operation of the entire sequence controller 60, and there is no margin for finely controlling the command signal to the gradient magnetic field waveform output unit 58. Therefore, in the conventional sequence control device, it has been difficult to improve the fineness of the operation of the control target.

An object of the present invention is to provide a sequence control device that controls the operation of a controlled device in accordance with a predetermined processing procedure, thereby realizing a sequence control device with improved control accuracy and capable of finely controlling the operation of the controlled device. That is.

[0013]

In order to achieve the above object, the present invention is configured as follows. Nuclear magnetic resonance
Startup in which commands are supplied from the central processing unit of the mazing device
Processing control unit and microprogram for performing sequence control
And the above microprogram sequencer
A microprocessor that stores the sequence steps to operate
A nuclear magnetic resonance imaging apparatus.
Operation of the controlled unit based on instructions from the central processing unit
Sequence control device for controlling the control according to a predetermined processing procedure
, The finger from the microprogram sequencer
According to the RF magnetic field of nuclear magnetic resonance imaging equipment
High-frequency signal output for generating high-frequency signals to be supplied to the control unit
Section, a predetermined arithmetic processing procedure and basic data of this processing procedure.
An arithmetic storage unit for storing data,
Was started by the PLC and stored in the operation storage unit.
Based on the processing procedure and basic data,
Performs high-speed signal processing asynchronously with the Gram sequencer,
Calculation to generate gradient magnetic field signal to be supplied to gradient magnetic field generator
And a signal processed at a high speed by the arithmetic unit,
In synchronization with the operation of the microprogram sequencer,
A synchronization control unit that supplies the magnetic field to the magnetic field generation unit.

[0014]

Preferably, in the above sequence control device, the arithmetic section generates and outputs a waveform signal based on the processing procedure and the basic data stored in the arithmetic storage section.
Preferably, in the above sequence control device,
The arithmetic unit is a digital signal processor capable of performing a product-sum operation at a high speed.

[0016]

When the microprogram sequencer is started by the central processing unit, it starts a sequence operation according to the sequence procedure stored in the microprogram storage. The microprogram sequencer instructs the operation unit to start based on the sequence procedure. The arithmetic unit performs high-speed signal processing asynchronously with the microprogram sequencer based on the processing procedure and the basic data stored in the arithmetic storage unit. The signal processed by the operation unit is supplied to the synchronization control unit. The synchronization control unit supplies the supplied signal to the controlled device in synchronization with the operation of the microprogram program sequencer. As a result, the control accuracy is improved without adding a control operation to the microprogram sequencer, and the operation of the controlled device can be finely controlled.

[0017]

FIG. 1 is a schematic block diagram of a sequence control device 50 according to an embodiment of the present invention, which is an example applied to a nuclear magnetic resonance imaging apparatus. FIG. 2 is an overall configuration diagram of the nuclear magnetic resonance imaging apparatus.
FIG. 2 is a diagram showing an imaging sequence of a spin echo method most frequently used in a nuclear magnetic resonance imaging apparatus.

In FIG. 2, reference numeral 64 denotes a central processing unit (CP).
U) and 61 are image processing devices. Also, 31, 32,
Reference numeral 33 denotes an amplifier of a gradient magnetic field power supply.
Are gradient magnetic field coils for generating gradient magnetic fields in the Z, X, and Y directions, respectively. Amplifiers 31, 32, 3
3 drives the gradient magnetic field coils 21, 22, and 23, respectively. The amplifiers 31, 32 and 33 constitute a gradient magnetic field control device 30. The gradient magnetic field generated by the gradient magnetic field coils 21, 22, and 23 causes the magnetic field distribution in the space where the inspection target is placed to have a desired gradient distribution. The sequence control device 50 has a function of outputting various commands and data to each device at a fixed timing.

The RF controller 40 generates a waveform according to the command and data from the sequence controller 50 and, after amplification,
The RF coil 41 is excited. When a nuclear magnetic resonance signal is generated from the subject 70, the nuclear magnetic resonance signal is
The signal is received by the RF coil 41. The signal component received by the RF coil 41 is supplied to the RF control device 40. Then, after signal processing by the RF control device 40, the signal is sent to the image processing device 61 and converted into image data. The converted image data is supplied to the display 62 via the interface bus 65, and displayed on the display 62 as a medical diagnostic image. The operation of each device is performed by the operation unit 63. Note that a static magnetic field is generated by the magnet 10.
In addition, a subject 70 as a subject is arranged on a bed 71, and the bed 71 is configured to be movable on a support base 72.

The subject 70 includes a magnet 10 for generating a static magnetic field H 0, X, Y and Z gradient magnetic field coils 21, 22 and 23 for generating gradient magnetic fields in three directions orthogonal to each other.
And an RF magnetic field coil 41 for generating an RF magnetic field. Here, the transverse section (XY plane) of the subject 70
In order to capture the image, the gradient magnetic field control device 30 and the RF control device 40 are driven in accordance with the spin echo sequence shown in FIG.

In FIG. 3, in a period G from time t0 to time t1, the RF power (((FIG. 3)) amplitude-modulated while a gradient magnetic field Gz (FIG. 3 (B)) is applied to the subject 70 is applied. A)) is applied to the RF coil 41. The magnetic field strength of the cross section is represented by the sum H0 + zGz of the static magnetic field H0 and the gradient magnetic field strength zGz at the position z. On the other hand, since the amplitude-modulated RF power of the angular frequency ω has a specific frequency band ω ± Δω, the angular frequency ω or the gradient magnetic field strength Gz should be selected so as to satisfy the following equation (3). Then, the hydrogen nuclear spin in the cross section is excited. ω ± Δω = γ (H0 + zGz) (3) Here, γ represents the gyromagnetic ratio of the hydrogen nucleus.

Next, in a period H from the time t1 to the time t2,
By applying the gradient magnetic field Gy ((C) in FIG. 3) for Δt, the previously excited nuclear spin generates a frequency shift Δωa represented by the following equation (4) depending on the position y. Δωa = γyGyΔt (4) During a period J from time t3 to t4, a nuclear magnetic resonance signal is collected with the gradient magnetic field Gx ((D) in FIG. 3) applied. At this time, the nuclear spin excited in the period G is at the position x
Has a frequency difference Δωb expressed by the following equation (5). Δωb = γxGx --- (5) In a period I from time t2 to t3, an RF magnetic field of 180 degrees and a gradient magnetic field Gz are applied in order to obtain a spin echo of the excited nuclear spin. Until time t0 and time t
The period K after 4 is a waiting time until the nuclear spin returns to equilibrium. If the amplitude value of the gradient magnetic field Gy in the period H is changed by 256 steps and the nuclear magnetic resonance signal is collected repeatedly, data of 256 × 256 can be obtained. An image can be obtained by performing a two-dimensional Fourier transform on these data.

Next, referring to FIG. 1, the central processing unit (CP
U) 64 is connected to the activation processing control unit 52 and the microprogram storage unit 53 via the interface bus 65, and the operation of the sequence control device 50 is determined by the sequence procedure stored in the microprogram storage unit 53. . The internal interface bus 59 is a main bus that communicates between components in the system control device 50. The bus 59 includes a microprogram sequencer 51 for controlling the operation of each component, a microprogram storage unit 53, an arithmetic unit 54 for generating an output waveform according to a command from the microprogram sequencer 51, and a bus necessary for waveform output. It is connected to an arithmetic storage unit 55 that stores processing procedures and basic data, and an RF waveform output unit 57. Here, in the example of FIG. 1, the arithmetic unit 54 uses a digital signal processor (DSP) that can perform a product-sum operation at a high speed.
The arithmetic storage unit 55 and the synchronization control unit 56 are controlled by a command from the arithmetic unit 54, and the synchronization control unit 56
The waveform data is output to 0, and the RF waveform output unit 57 outputs the waveform to the RF control device 40.

The sequence control device 5 having the above configuration
At 0, a predetermined sequence control procedure is stored in the microprogram storage unit 53 from the central processing unit 64 in advance. In addition, a processing procedure for generating waveform data to be transmitted to the gradient magnetic field generator 30 and base data are stored in the arithmetic storage unit 55. Next, when a sequence start instruction is transmitted from the operation unit 63 to the start processing control unit 52 via the central processing unit 64, the sequence is started.
When the sequence is started, the microprogram sequencer 51 is activated by the activation processing control unit 52, and sequentially reads out and executes the sequence procedure from the microprogram storage unit 53. When the timing to output the waveform data and the command to the RF control device 40 comes, the RF waveform output unit 57
Is R in response to a command from the microprogram sequencer 51.
F waveform data is received, and the waveform data is supplied to the RF control device 40 at a designated timing.

When the timing to output the waveform data to the gradient magnetic field generator 30 comes, the arithmetic unit 54 receives a start command from the microprogram sequencer 51, and
Read the set parameters. Then, the operation unit 54
Selects a process stored in the operation storage unit 55 in accordance with the parameter, and generates waveform data based on the selected process. The generated waveform data is supplied from the calculation unit 54 to the synchronization control unit 56. In the synchronization control unit 56, the waveform data is supplied to the gradient magnetic field generator 30 in synchronization with the operation of the microprogram sequencer 51.

Next, an example of waveform data generated by the arithmetic section 54 is shown in FIG. In FIG. 4, the waveform is changed in a curve from the gradient magnetic field value a to the gradient magnetic field b from the time point t1 to the time point t1a. And, the gradient magnetic field value is b from time t1a to t2.
And is linearly changed so as to become the magnetic field value c at time t3. In this case, the change of the waveform signal G (t) from the gradient magnetic field value a to b can be executed based on the following equation (6). G (t) = (a + GM (t)) (ba) / MaxG --- (6) where GM (t) is a base pattern registered in the arithmetic storage unit 55, and MaxG is the maximum output value. It is.

As described above, in the sequence controller 50, separately from the microprogram sequencer 51,
A calculation unit 54 for controlling the gradient magnetic field waveform, a calculation storage unit 55,
Since the synchronization control unit 56 is provided, the sequence control device 50 with improved control accuracy is realized, and the gradient magnetic field generation device 30
Can be finely controlled. The sharpness of an image can be improved. Further, since the gradient magnetic field waveform can be finely controlled to obtain an image with high efficiency, the imaging time of the subject can be shortened (ultra high-speed imaging is possible).

The waveform shown in FIG. 4 is applicable to each of the X, Y, and Z gradient magnetic fields. Further, the waveforms that can be generated by the arithmetic unit 54 are not limited to those shown in FIG. 4, but other waveforms, for example, SIN waveforms can be generated.

Further, in the example of FIG. 1, a digital signal processor is used as the arithmetic unit 54, but the present invention is not limited to this, and various other types can be applied. Further, the above-described embodiment is an example in which the sequence control apparatus of the present invention is applied to a nuclear magnetic resonance imaging apparatus. However, the present invention is not limited to the nuclear magnetic resonance imaging apparatus and can be applied to other apparatuses. For example, the sequence control device of the present invention can be applied to the operation and analysis control of an automatic analyzer.

[0030]

As described above, according to the present invention, there is provided a microprogram sequencer, a start-up processing control unit, and a microprogram storage unit, and controls the operation of a controlled device according to a predetermined processing procedure. In the sequence control device, an operation storage unit that stores processing procedures and basic data, an operation unit that performs high-speed signal processing asynchronously with the microprogram sequencer, and a signal that is processed by the operation unit is transmitted to the operation of the microprogram sequencer. Synchronously,
And a synchronization control unit for supplying the controlled device. Therefore, the controlled device can be precisely controlled, and a sequence control device with improved control accuracy can be realized. Further, according to the present invention, a start processing control unit to which a command is supplied from the central processing unit of the nuclear magnetic resonance imaging apparatus, a microprogram sequencer, and a microprogram storage unit, and the operation of the controlled unit is performed. In a sequence control device that controls according to a predetermined processing procedure, a high-frequency signal output section that generates a high-frequency signal to be supplied to a high-frequency magnetic field control section, an arithmetic storage section that stores arithmetic processing procedures and basic data, and a microprogram sequencer are asynchronous. And a signal processing unit that generates a gradient magnetic field signal to be supplied to the gradient magnetic field generating unit, and supplies the signal processed by the arithmetic unit to the gradient magnetic field generating unit in synchronization with the operation of the microprogram sequencer. A synchronization control unit. As a result, a sequence control device with improved control accuracy can be realized, and the gradient magnetic field generator of the nuclear magnetic resonance imaging device can be precisely controlled to improve the definition of an image. In addition, since the gradient magnetic field waveform can be finely controlled and an image can be obtained with high efficiency, the imaging time of the subject can be reduced.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of a sequence control device according to an embodiment of the present invention.

FIG. 2 is a schematic configuration diagram of a nuclear magnetic resonance imaging apparatus to which the present invention is applied.

FIG. 3 is a timing chart of an imaging sequence of the nuclear magnetic resonance imaging apparatus.

FIG. 4 is a diagram illustrating an example of an output waveform generated by an arithmetic control unit in the example of FIG. 1;

FIG. 5 is a schematic configuration diagram of a conventional sequence control device.

FIG. 6 is a diagram illustrating an output waveform generated by a gradient magnetic field waveform output unit in the example of FIG. 6;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Magnet 21, 22, 23 Gradient magnetic field generating coil 30 Gradient magnetic field generating device 31, 32, 33 Amplifier 40 RF controller 41 RF coil 50 Sequence controller 51 Microprogram sequencer 52 Start-up processing controller 53 Microprogram storage unit 54 Operation unit 55 operation storage unit 56 synchronization control unit 57 RF waveform output unit 59 internal interface bus 61 image processing unit 62 display 63 operation unit 64 central processing unit 65 interface bus 70 subject 71 bed 72 support base

Continuation of the front page Examiner Kosen Ito (56) References JP-A-55-154607 (JP, A) JP-A-1-119238 (JP, A) JP-A-62-240039 (JP, A) (58) Field surveyed (Int.Cl. ⁷ , DB name) A61B 5/055 JICST file (JOIS)

Claims (3)

(57) [Claims] An activation processing control unit to which a command is supplied from a central processing unit of a nuclear magnetic resonance imaging apparatus, a microprogram sequencer for performing sequence control, and a microcontroller for storing a sequence procedure for operating the microprogram sequencer. A program storage unit;
A sequence control device that controls the operation of the controlled unit according to a predetermined processing procedure based on a command from a central processing unit of the nuclear magnetic resonance imaging apparatus. A high-frequency signal output unit that generates a high-frequency signal to be supplied to the magnetic field control unit; an arithmetic storage unit that stores a predetermined arithmetic processing procedure and basic data of the processing procedure; Based on the stored processing procedure and the basic data, an arithmetic unit that performs high-speed signal processing asynchronously with the microprogram sequencer and generates a gradient magnetic field signal to be supplied to the gradient magnetic field generation unit; Synchronizes the processed signal with the operation of the above microprogram sequencer And a synchronization control unit for supplying to the gradient magnetic field generation unit. 2. The sequence control device according to claim 1, wherein the arithmetic unit generates and outputs a waveform signal based on the processing procedure and basic data stored in the arithmetic storage unit. Sequence controller. 3. The sequence control device according to claim 1 , wherein said operation unit is a digital signal processor capable of performing a product-sum operation at a high speed.