JPH09294734A - Magnetic resonance tomography equipment - Google Patents

Abstract

PROBLEM TO BE SOLVED: To speedily execute plural kinds of signal processing at the preceding step of data processing such as Fourier transformation in magnetic resonance tomography with simple configuration. SOLUTION: This magnetic resonance tomographic apparatus is provided with a signal processing part 13 consisting of plural signal processing units a1-aN for parallelly inputting NMR signals from an A/D converter 11. Concerning the NMR signals, plural kinds of signal processing different for each unit are parallelly executed at the respective signal processing units a1-aN and during one time of pulse sequence, these signals are sent to a host computer 14 for image reconstitution.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to nuclear magnetic resonance (Nu
BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for performing tomography of a subject using a clear magnetic resonance (abbreviated as NMR) phenomenon, and in particular, a signal of an NMR signal detected from the subject with irradiation of an RF (Radio Frequency) pulse Related to the technology for processing.

[0002]

2. Description of the Related Art In recent years, a magnetic resonance tomography apparatus for performing imaging by utilizing the NMR phenomenon has been widely used in the field of medical morphological diagnosis. As is well known, a magnetic resonance tomography apparatus generates a uniform static magnetic field in an imaging region space, and three gradient magnetic fields whose magnetic field strength changes in a three-dimensional direction orthogonal to the static magnetic field space at predetermined timings. The subject is irradiated with an RF pulse for nuclear spin excitation in a superimposed manner, whereby one or a plurality of NMR signals returning from the subject are detected. A sequence in which a gradient magnetic field or RF pulse is added at a predetermined timing to obtain a predetermined number of NMR signals is called a pulse sequence. In order to perform one tomography, the above pulse sequence is cyclically repeated to continuously detect a large number of NMR signals. The detected NMR signals are sequentially digitized and subjected to data processing such as Fourier transform to reconstruct a tomographic image of the subject.

In a magnetic resonance tomography apparatus, noise removal filter processing (for example, FIR filter processing = finite length impulse response type filter processing) is applied to an NMR signal before data processing such as Fourier transform, and the like. In addition, signal processing such as emphasis processing for an additional specific signal component may be performed. By this signal processing, for example, the tone of the finally obtained image can be made to match the condition of the affected area and the purpose of diagnosis.

[0004]

However, in the conventional magnetic resonance tomography apparatus, a plurality of different signal processes (for example, a filtering process of the frequency characteristic A and an NMR signal obtained by one pulse sequence are performed). , Frequency characteristic B), it takes a long time to process the signal. Therefore, the NM obtained by the next pulse sequence is used.
There is a problem that the signal processing cannot be completed by the time when the R signal should be processed. That is,
The magnetic resonance tomography apparatus continuously detects a large number of NMR signals required for one tomography by repeating the pulse sequence at an extremely short time interval and performs signal processing in real time. This is because it is necessary to complete the signal processing for the NMR signal obtained in step 1 within a limited short time.

Therefore, if a plurality of signal processings are to be performed, the tomographic image of the same portion must be read again, and the image taking time becomes very long, which is not practical.

In view of the above problems, the present invention can perform different types of signal processing with a quick and simple structure in the former stage of data processing for image reconstruction, and a plurality of NMR signals subjected to different signal processing can be implemented. An object of the present invention is to provide a magnetic resonance tomography apparatus capable of sending a signal to a data processing means during one pulse sequence.

[0007]

The present invention adopts the following constitution in order to achieve the above-mentioned object. That is, according to the present invention, a static magnetic field generating means for generating a uniform static magnetic field in the imaging region space and three gradient magnetic fields (slice site selection gradients) in which the magnetic field strength changes in three-dimensional directions orthogonal to each other in the static magnetic field space. A gradient magnetic field generating means for generating a magnetic field, a reading gradient magnetic field, a phase encoding gradient magnetic field), and an excitation / detection means for irradiating a subject with an RF pulse for nuclear spin excitation and detecting an NMR signal from the subject. And N
In the magnetic resonance tomography apparatus including AD conversion means for digitizing MR signals and data processing means for reconstructing a tomographic image of a subject by performing arithmetic processing on the digitized NMR signals. A signal processing means including a plurality of signal processing units for inputting the digital NMR signal output from the converting means and performing signal processing is interposed between the AD converting means and the data processing means,
Further, each of the signal processing units is characterized in that the operation of performing different signal processing on each unit to the digital NMR signal and transmitting the digital NMR signal to the data processing means proceeds in parallel.

[0008]

The operation of the present invention is as follows. First, the static magnetic field generating means creates a static magnetic field in the imaging region space. Then, the gradient magnetic field generation means superimposes the gradient magnetic field on the static magnetic field space at a predetermined timing, and the excitation / detection means irradiates the object arranged in the imaging region space with an RF pulse for nuclear spin excitation. To be done. Based on this, the NMR signal returned from the subject is detected by the excitation / detection means. This NMR signal is digitized by the AD conversion means and then given to the signal processing means.
Then, after each signal processing unit of this signal processing unit performs different signal processing in parallel on the digital NMR signal, the signal-processed NMR signal is sent from each signal processing unit to the data processing unit. The data processing means of the magnetic resonance tomography apparatus receives the sent NM.
Perform data processing such as Fourier transform based on the R signal,
Each image corresponding to the signal processing is reconstructed.

The multiplexing seen on the hardware of the signal processing system may be performed only between the AD conversion means and the data processing means, and it is not necessary to multiplex the hardware of the entire signal processing system, and it is possible to further increase the hardware. It is not necessary to multiplex the precision element and the hardware of the analog signal processing system from the RF coil for RF pulse irradiation, which requires delicate adjustment, to the AD conversion means.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the magnetic resonance tomography apparatus of the present invention will be described below with reference to the drawings. FIG.
FIG. 1 is a block diagram showing a main part of a magnetic resonance tomography apparatus according to an embodiment.

The apparatus of the embodiment comprises a main magnet 2 for generating a uniform static magnetic field in the internal space of the gantry unit 1, and three gradient magnetic field coils 3 (3x, 3x, for applying a gradient magnetic field so as to be superposed on the static magnetic field). 3y, 3z) are provided.
The gradient field coil (Gradient Field Coil) 3 has three uniform magnetic fields H ₀ generated by the main magnet 2 and three gradient magnetic fields Gx, Gy, Gz whose magnetic field strengths change in three-dimensional directions (X, Y, Z) orthogonal to each other. Sets of gradient magnetic field coils 3x, 3y, which superimpose the pulse (reading gradient magnetic field, phase encoding gradient magnetic field, slice region selecting gradient magnetic field)
It is composed of 3z. An imaging site of the subject is arranged at the center of the image in the internal space (imaging region space) of the gantry unit 1 to which the static magnetic field and the gradient magnetic field are applied, and an RF coil for exciting nuclear spin (near the subject). Radio Frequency Coil 4 is deployed.

A gradient magnetic field power source 5 is connected to the gradient magnetic field coil 3 to supply electric power necessary for generating the gradient magnetic fields Gx, Gy and Gz. A waveform signal from the waveform generator 6 is input to the gradient magnetic field power supply 5, and the gradient magnetic field Gx, G
Each y, Gz gradient magnetic field waveform is controlled. The main magnet 2 corresponds to the static magnetic field generating means in this invention, and the gradient magnetic field coil 3, the gradient magnetic field power source 5 and the waveform generator 6 correspond to the gradient magnetic field generating means in this invention. An RF pulse is supplied to the RF coil 4 via an RF power amplifier 7, and the subject is irradiated with the RF pulse from the RF coil 4. The RF pulse is an AM signal generated by the RF signal generator 8 in the AM (amplitude) modulator 9 according to the waveform sent from the waveform generator 6.
Modulated. The RF power amplifier 7, the RF signal generator 8, the AM (amplitude) modulator 9 and the like correspond to the excitation / detection means in this invention.

The NMR signal generated in the subject is received and detected by the RF coil 4, and then is passed through the preamplifier 10 to A
It is sent to the / D converter (A / D conversion means) 11. This A
A sampling pulse is input from the sampling pulse generator 12 to the D converter 11, and an analog NMR signal is digitized at a timing synchronized with the sampling pulse and sent to the next signal processing unit 13. The digital NMR signal is subjected to predetermined signal processing by the signal processing unit 13, and then further processed by the host computer 14.
Is taken into.

Host computer (data processing means) 1
Reference numeral 4 processes the captured data, reconstructs an image to display a tomographic image on the output display 15, determines the timing of the entire sequence via the sequencer 16, and controls the operation of the signal processing unit 13. To do
The host computer 14 reconstructs a three-dimensional image by data processing such as three-dimensional Fourier transform. The host computer 14, for example, determines the generation timing and the oscillation frequency of the RF band oscillation signal for the RF pulse, controls the waveforms and intensities of the Gx, Gy, and Gz gradient magnetic fields, and also controls the RF pulse. Determine the envelope. Therefore, this host computer 14
In addition to its role as a data processing means, it also partially plays a role as a gradient magnetic field generating means and an excitation / detection means. The operation unit 17 is used by the operator to input various data necessary for operating the apparatus and to set conditions.

Next, the configuration around the signal processing section (signal processing means) 13 which is a feature of the magnetic resonance tomography apparatus of the present invention will be described more specifically with reference to the drawings. 2 is a block diagram showing the overall configuration of the signal processing unit 13, and FIG. 3 is a block diagram showing the configuration of one signal processing unit.

The signal processing unit 13 is provided between the A / D converter 11 and the host computer 14. Therefore, the signal processing unit 13 is provided before entering the host computer 14 (that is, data processing such as Fourier transform). Before the so-called) digitized NMR signal (hereinafter,
Signal processing will be performed on the raw data). As shown in FIG. 2, the signal processing unit 13 receives N digital processing signals from the AD converter 11 and performs signal processing on the N signal processing units a1, a2, ...
The data transfer unit b having aN and transmitting the signal-processed digital NMR signals sent in parallel from the respective signal processing units to the host computer 14 without confusion and delay, and the signal processing units a1 to aN and the data transfer unit b. It has a control CPU (control processor) c for advancing the operation according to a command signal received from the host computer 14.

In the signal processing unit 13, by the monitoring / control function of the control CPU c, the signal processing units a1 to aN perform different signal processing for each unit on the digital NMR signal and send it to the host computer 14 in parallel. It is structured to proceed. Signal processing unit a
Examples of the type of signal processing executed in 1 to aN include common phase detection processing performed in each unit, FIR filtering processing different for each unit, and emphasis processing of a specific signal component.

FIG. 3 shows a concrete configuration example of the signal processing unit. The signal processing unit has an input register RI for receiving a digital NMR signal to be processed from the AD converter 11 on the input side, and transmits a processed digital NMR signal as a filtering processing result to the data transmitting unit b. In addition to having an output register RO for storing, a data memory DM for storing a digital NMR signal, a coefficient memory FM for storing a filter coefficient string, and an arithmetic CPUe for performing arithmetic operations for phase detection processing and filtering processing. Have. The filter coefficient string stored in the coefficient memory FM can be loaded from the host computer 14 via the control CPU c. Designation of signal processing units to be operated in parallel can be performed by an input operation from the operation unit 17.

For example, two signal processing units a1 and a
2 has the configuration shown in FIG. 3, and the coefficient memory FM of the signal processing unit a1 is loaded with a filter coefficient string for performing the filtering process of the frequency characteristic shown by the solid line A in FIG. Figure 4 shows the FM.
It is assumed that the filter coefficient sequence for performing the filtering process of the frequency characteristic indicated by the alternate long and short dash line B is loaded. Then, by inputting the digital NMR signal in parallel to both signal processing units a1 and a2 and operating them in parallel and sending the processing result from the data transmitting section b without confusion or delay, the filtering-processed digital NM of the solid line A is obtained.
Both the R signal and the filtered digital NMR signal of dash-dotted line B will be sent to the host computer 14 during one pulse sequence. From the above, it can be said that the signal processing unit 13 has a signal processing function and a memory function capable of cooperative driving.

The host computer 14 can reconstruct a normal tomographic image by data processing using the filtered digital NMR signal indicated by the solid line A, and the filtered process indicated by the alternate long and short dash line B (high frequency components are removed). 3.) A digital NMR signal can be used to reconstruct a contrast image with suppressed background. Furthermore, it is also possible to obtain the digital NMR signal that has been subjected to the filtering process of the frequency characteristic indicated by the solid line C in FIG. 5 by obtaining the difference between both digital NMR signals, and reconstruct an image by this. I can. As described above, the magnetic resonance tomography apparatus of the present invention is provided with the signal processing unit 13, so that it is possible to give variety to the image reconstruction.

Further, in the present invention, the digital signal processing unit 13 is interposed between the A / D converter 11 and the host computer 14, and the signal processing surface / device hardware provided by this arrangement form is provided. There are the following advantages in terms of wear. That is, since the signal processing unit 13 in the device of the present invention performs signal processing on so-called raw data before Fourier transform, there is no loss of information and an appropriate signal processing result can be obtained. If signal processing is performed in parallel on data that has been subjected to data processing such as Fourier transform, the lack of information during Fourier transform is significant, and an appropriate processing result cannot be obtained.

Moreover, the multiplexing of the hardware of the signal processing system is minimized. That is, the signal processing unit 13 is multiplexed only between the A / D converter 11 and the host computer 14, and does not multiplex the so-called signal processing system hardware as a whole. further,
It is not necessary to multiplex the hardware of the analog signal processing system (the signal processing configuration from the RF coil for RF pulse irradiation to the AD conversion means) that requires high precision elements and delicate adjustment. Therefore, in the device of the present invention, the hardware multiplexing can be minimized, and the increase in cost and adjustment can be minimized.

In the above embodiments, the configurations of the signal processing unit and the signal processing unit are as shown in FIGS. 2 and 3, but the configurations of the signal processing unit and the signal processing unit in the present invention are not shown. Not limited to things. Furthermore, it goes without saying that the overall configuration of the magnetic resonance tomography apparatus may be a configuration other than that illustrated in FIG.

[0024]

According to the magnetic resonance tomography apparatus of the present invention, a plurality of signal processing units capable of cooperative driving are provided with signal processing means capable of parallel signal processing of digital NMR signals before data processing such as Fourier transform. As a result of performing different kinds of signal processing on the NMR signal during one pulse sequence and rapidly sending it to the data processing unit, it is possible to have variety in image reconstruction. Furthermore, since the multiplexing of the signal processing system is minimized,
The increase in hardware load can be minimized, and parallel signal processing can be realized with a simple configuration.

[Brief description of drawings]

FIG. 1 is a block diagram showing a main configuration of a magnetic resonance tomography apparatus according to an embodiment.

FIG. 2 is a block diagram showing a specific configuration of a signal processing unit in the embodiment apparatus.

FIG. 3 is a block diagram showing a specific configuration of a signal processing unit in the embodiment apparatus.

FIG. 4 is a graph showing an example of filtering frequency characteristics of a signal processing unit.

FIG. 5 is a graph showing a frequency characteristic of filtering by subtraction processing.

[Explanation of symbols]

 2 ... Main magnet 3 ... Gradient magnetic field coil 4 ... RF coil 5 ... Gradient magnetic field power supply 8 ... RF signal generator 11 ... A / D converter 13 ... Signal processing unit 14 ... Host computer a1 ... Signal processing unit a2 ... Signal processing unit aN ... Signal processing unit b ... Data transfer section c ... Control CPU

Claims (1)

[Claims] 1. A static magnetic field generating means for generating a uniform static magnetic field in an imaging region space, and three gradient magnetic fields (slice region selecting gradient magnetic field) in which magnetic field strengths change in three-dimensional directions orthogonal to each other in the static magnetic field space. , Gradient magnetic field for reading, gradient magnetic field for phase encoding), and excitation / detection means for irradiating the subject with RF pulses for nuclear spin excitation and detecting NMR signals from the subject. A magnetic resonance tomography apparatus comprising AD conversion means for digitizing an NMR signal and data processing means for reconstructing a tomographic image of a subject by performing arithmetic processing on the digitized NMR signal, The signal processing means provided with a plurality of signal processing units for inputting the digital NMR signal output from the AD converting means and executing the signal processing is the AD converting means. And a step of interposing between the signal processing unit and the data processing means, and each of the signal processing units performs in parallel the operation of performing different signal processing on the digital NMR signal for each unit and transmitting the digital NMR signal to the data processing means. Magnetic resonance tomography apparatus.