JPH024331A - Magnetic resonance device - Google Patents

Abstract

PURPOSE:To process a magnetic resonance signal from a body to be checked with high accuracy by providing a reference oscillator generating a reference clock, a frequency divider for sampling, a computer sampling control data generator and a clock supplying device. CONSTITUTION:When a reference oscillator 32 generates a reference clock C to determine the impression timing of a high frequency magnetic field pulse and a tilted magnetic field, a frequency divider 36 for sampling generates a clock signal CS for sampling based on this reference clock. A computer sampling control data generator 46 generates sampling control data DS based on this clock signal CS. A clock supplying device 26 controls the sampling timing of a computer 16 based on the sampling control data DS, which are generated by the generator 26. Thus, since sampling timing is exactly determined based on one reference clock to be used for each timing control, the peak of the magnetic resonance signal can be fetched with the high accuracy.

Description

Detailed Description of the Invention [Field of Industrial Application] The present invention relates to a magnetic resonance apparatus that acquires spectra and tomographic images using NMR (nuclear magnetic resonance), ESR (electron spin resonance), etc. The present invention relates to a magnetic resonance apparatus that can process magnetic resonance signals from a specimen with high precision.

[Prior Art] Fig. 3 is a block diagram showing a general magnetic resonance apparatus. A static magnetic field generator (3) that applies a static magnetic field in the Z-axis direction is an examination table that introduces the subject (1) into the static magnetic field generator (2).

(4) is a high-frequency coil for applying high-frequency energy such as a high-frequency magnetic field pulse to the subject (1) and receiving magnetic resonance signals from the subject (1), and (5) is the impedance of the high-frequency coil (4). a converting matching device, (6)
is a transmission/reception switching device connected to the matching device (5); (7) is a transmitter for applying high frequency energy to the subject (1) via the transmission/reception switching device (6) and the high frequency coil (4);
(8) is a receiver that receives magnetic resonance signals from the subject (1) via a high frequency coil (4) and a transmission/reception switching device (6).

(9) is an X-axis gradient magnetic field coil that applies a magnetic field pulse tilted in the X-axis direction to the subject (1); (10) is an X-axis gradient magnetic field power supply that drives the X-axis gradient magnetic field coil (9); )
(12) is a Y-axis gradient magnetic field power source that drives the Y-axis gradient magnetic field coil (11), and (13) is a Y-axis gradient magnetic field coil that applies a magnetic field pulse tilted in the Y-axis direction to the subject (1). The Z-axis gradient magnetic field coil (14) applies a magnetic field pulse tilted in the Z-axis direction to the specimen (1), and the Z-axis gradient magnetic field coil (14)
13> is a Z-axis gradient magnetic field power supply.

(15) is a sequence control device that controls the transmitter (7), the receiver (8), each gradient magnetic field power source (10), (12), and (14) in a predetermined sequence, and also controls the entire device. (te) is a computer connected to the sequence control device (15), which generates control data for image composition, processes magnetic resonance signals obtained from the receiver (8), and performs image composition processing. It has become. (1)
) is an operation console that serves as an input/output terminal device for inputting parameters, etc. necessary for image composition to the computer (16), (1st)
is an image display device connected to the console (1)).

FIG. 4 is a block diagram showing the configuration of the control timing and waveform output section in the sequence control device (15).
20) is a control unit including a CPU, (21) is a DA converter for controlling the X-axis gradient magnetic field power supply (10), and (22) is a DA converter for controlling the Y-axis gradient magnetic field power supply (12). , (23) is a DA converter for controlling the Z-axis gradient magnetic field power supply (14), (24) is a DA converter for controlling the transmitter (7), and (25) is a DA converter for controlling the receiver (8). This is a gate circuit for controlling opening and closing of the gate.

The control unit (20) also controls each DA converter (21) to (24).
) and control data DX, D via the gate circuit (25)
Each gradient magnetic field power supply (1
0) to (14), the transmitter (7) and the receiver (8), and also controls the magnetic resonance signal sampling timing of the computer (16).

Next, the operation of the conventional magnetic resonance apparatus shown in FIGS. 3 and 4 will be explained. Here, the gradient magnetic field in the X-axis direction is used as a signal readout magnetic field for frequency encoding, the gradient magnetic field in the Y-axis direction is used as a phase encoding magnetic field, and the gradient magnetic field in the Z-axis direction is used as a slice magnetic field, and two-dimensional Fourier transform (2DFT) is performed.
) method using the spin echo method or the gradient field (gradient magnetic field) echo method.

First, the subject (
1), the sequence controller (15) simultaneously drives the high frequency coil (4) and the Z-axis gradient magnetic field coil (13), and generates a high frequency magnetic field pulse (
A slicing magnetic field for specifying a tomographic plane is applied to the subject (1) along with a 90° pulse (usually a 90° pulse). This results in
Energy is supplied to nuclear spins within a desired cross-sectional plane within the subject (1).

Next, the Y-axis gradient magnetic field coil (11) and the X-axis gradient magnetic field coil (10) are driven to apply a phase encode magnetic field and a signal readout magnetic field.

Then, while applying a signal readout magnetic field with reversed polarity, magnetic resonance signals (echo signals) are generated by gradient magnetic field echoes.
is taken into the computer (16) via the high frequency coil (4), but the timing at which the magnetic resonance signal reaches its peak value is
It depends on the application timing of the signal readout magnetic field and the high-frequency magnetic field pulse.

This magnetic resonance signal is collected only at predetermined sampling points during the application time of the signal readout magnetic field, and is repeatedly received a number of times corresponding to a predetermined pixel while changing the amount of phase encoding by the phase encoding magnetic field at a predetermined pitch. and is acquired by the computer (16) as a pulse train. This makes it possible to decompose magnetic resonance signals in the Y-axis direction.For example, when the number of pixels in a tomographic image is 256x256,
In this case, the number of sampling points received at one time is 256 or more, and the number of repetitions (number of signal collections) is 256.

Finally, the computer (16) performs two-dimensional Fourier transform on the pulse train of the magnetic resonance signal to obtain a desired matrix size NX.
The image of the N tomographic plane is reconstructed and displayed on the image display device (18).

In the above sequence, the magnitude and output timing of each gradient magnetic field on the X-axis, Y-axis, and Z-axis, the magnitude, waveform, and output timing of the high-frequency magnetic field pulse, and the receiver (8
) is controlled by the sequence control device (15), and the control data is received from the DA converters (21) to (24) and the gate circuit (25) at accurate timing. It is being output. In addition, the timing of importing the magnetic resonance signal into the computer (16) is as follows.
The peak of the magnetic resonance signal is controlled to be captured at a predetermined sampling point, and the control section (20) sends a sampling start trigger to the computer (16).

[Problems to be Solved by the Invention] As described above, in the conventional magnetic resonance apparatus, timing control of each gradient magnetic field and high-frequency magnetic field pulse is performed accurately, but Calculation 1 (1B) is performed when the magnetic field is 0. As for the timing of capturing the signal data, since the sampling clock is not precisely synchronized with the control clock of the gradient magnetic field or high-frequency magnetic field pulse, sampling actually starts after the sampling trigger is input to the computer (16), for example. If there is any jitter, there is a problem that it becomes impossible to capture data when the magnetic resonance signal reaches its peak.

The present invention has been made to solve the above-mentioned problems, and an object of the present invention is to obtain a magnetic resonance apparatus that can sample magnetic resonance signals at predetermined timing and sample peaks with high precision.

[Means for Solving the Problems] A magnetic resonance apparatus according to the present invention includes a reference oscillator that generates a reference clock for determining the application timing of high-frequency magnetic field pulses and gradient magnetic fields, and a reference oscillator that generates a reference clock for determining the application timing of high-frequency magnetic field pulses and gradient magnetic fields, and a sampling oscillator that generates a reference clock based on the reference clock. A sampling frequency divider that generates a clock signal, a computer sampling control data generator that generates sampling control data based on the clock signal, and a clock supply device that controls the sampling timing of the computer based on the sampling control data. It was established.

[Function] In this invention, 1 used for each timing control
To accurately determine sampling timing based on two reference clocks.

[Example] Hereinafter, an example of the present invention will be described with reference to the drawings. still,
The overall configuration of the magnetic resonance apparatus according to the present invention is as shown in FIG.

FIG. 1 is a block diagram showing the main parts of an embodiment of the present invention. In the figure, (7), (8), (10), (12)
), (14), (16) and (21) to (25) are the same as described above. Also, (15Δ) and (20^) are the sequence control device (15) and the control unit 20, respectively.
) is supported.

(26) is a clock supplier that supplies a clock signal for magnetic resonance signal sampling to the AD converter in the computer (16) based on the sampling control data DS from the control unit (20A).

FIG. 2 is a block diagram showing the configuration of the control unit (20A) in FIG.
31> is a memory belonging to the control device (30), (32) is a 6 reference oscillator that belongs to the control device (30) and does not generate the reference clock C, and (33) is a clock for controlling each gradient magnetic field based on the reference clock C. (34) is a frequency divider for a power supply that generates signals c (35) receives tf! based on the reference clock C! (8) A receiver frequency divider that generates a clock signal cQ for controlling the computer, and (36) a sampling frequency divider that generates a clock signal Cs for controlling the computer <16) based on the reference clock C. It is a vessel.

(41) to (43) control the power supply control data D, DY and Dz based on the control signal B from the control device 30), BY and BZ and each clock signal cX, cY and Cz.
An X-axis power control data generator, a Y-axis power control data generator, and a Z-axis power control data generator generate
(23) respectively.

(44) is a transmitter output control data generator that generates output control data DR of high-frequency magnetic field pulses based on the control signal BZ and clock signal CR from the control device (30), and the output control data DR is DA. A converter (24) is supplied. (45) is a receiver control data generator that generates gate control data DQ based on the control signal BQ and clock signal CC from the control device (30), and the gate control data DQ is supplied to the gate circuit (25). has been done.

(46) is the sampling control data DS based on the control signal BS and clock signal Cs from the control device (30).
The sampling control data DS is a computer sampling control data generator that generates a clock supply device (26
).

The control signals BX to BZ, BR, BQ, and BS determine the magnitude, waveform, application time, etc. of each signal based on each control data D to DZ, DR, DQ, and DS.

Next, the operation of the embodiment of the present invention shown in FIGS. 1 and 2 will be described. Note that since the pulse sequence for acquiring the magnetic resonance signals is the same as described above, only the timing control for importing the magnetic resonance signals into the computer (16) will be described here.

In order to accurately capture the peak of the magnetic resonance signal into the computer (16), it is necessary to sample at the time when the peak appears, but as mentioned above, the time at which the magnetic resonance signal is acquired is determined by It can be accurately determined based on the pulse application interval, the waveform of the signal readout magnetic field, the application time, etc. Furthermore, since the number of sampling words and the sampling clock are determined by the resolution of the image and the band of the magnetic resonance signal, in order to capture the peak of the magnetic resonance signal at the position of the predetermined number of sampling words,
It is only necessary to start sampling exactly a period of time determined by the number of sampling words and the sampling clock.

In this case, ~cz, CR, cc, and Cs for each clock signal C are set to be an integer multiple or an integer fraction of each other, so it is difficult to accurately calculate the sampling start point of the magnetic resonance signal from each clock signal. I can do it.

In the above embodiment, the case where the magnetic signal 1 is an NMR echo signal is explained, but the FID signal or the ESR
Even if it is a signal, the same effect can be achieved.

Further, although the reference clock C is obtained from the reference oscillator (32) of the CPU in the sequence control device (15A), the reference clock may also be obtained from the reference oscillator in the computer (16).

Further, the frequency division ratio of each frequency divider (33) to (36) may be changed depending on the band of the magnetic resonance signal or the gradient magnetic field waveform.

Furthermore, for each clock signal C ~Cz, cR, cQ and Cs
are set to be an integer multiple or an integer fraction of each other, but it goes without saying that accurate control can be achieved by setting other frequency division ratios depending on the sampling timing.

[Effects of the Invention] As described above, according to the present invention, there is provided a reference oscillator that generates a reference clock for determining application timing of high-frequency magnetic field pulses and gradient magnetic fields, and a clock signal for sampling based on the reference clock. a computer sampling control data generator that generates sampling control data based on this clock signal, and a clock supply device that controls the sampling timing of the computer based on the sampling control data. Since the sampling timing is accurately determined based on one reference clock used for control, it is possible to obtain a magnetic resonance apparatus that can capture the peak of a magnetic resonance signal with high precision.

[BRIEF DESCRIPTION OF THE DRAWINGS] FIG. 1 is a block diagram showing the main parts of an embodiment of the present invention.
FIG. 2 is a block diagram showing the configuration of the control section in FIG. 1, FIG. 3 is a block diagram showing a general magnetic resonance apparatus, and FIG. 4 is a block diagram showing a conventional sequence control device. (1)...Object (15^)...Sequence control device (16)...Computer (26>...Clock supplier <32)...Reference oscillator (36)...For sampling Frequency divider (46)...computer sampling control data generator C
...Reference clock CS...Clock signal DS
...Sampling control data In the figures, the same reference numerals indicate the same or equivalent parts. Figure 2, 2OA 1, Indication of the case Patent Application No. 150150 of 1988 2, Name of the invention Magnetic Resonance Apparatus 3° Relationship to the Amendment Case Patent Applicant Address 2-2 Marunouchi, Chiyoda-ku, Tokyo 3 Name (601) Mitsubishi Electric Corporation Representative Moriya Shiki 4゜

Claims (1)

[Scope of Claims] A sequence control device for applying high-frequency magnetic field pulses and gradient magnetic fields to a subject in a predetermined sequence, and a computer for capturing and processing magnetic resonance signals from the subject. A magnetic resonance apparatus comprising: a reference oscillator that generates a reference clock for determining application timing of the high-frequency magnetic field pulse and the gradient magnetic field; and a sampling frequency divider that generates a sampling clock signal based on the reference clock. A computer sampling control data generator that generates sampling control data based on the clock signal; and a clock supply device that controls sampling timing of the computer based on the sampling control data. Magnetic resonance device.