JPS618040A - Diagnostic nuclear magnetic resonance apparatus - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] [Technical Field of the Invention] The present invention relates to a nuclear magnetic resonance apparatus for diagnosis that obtains tomographic images of a human body using nuclear magnetic resonance phenomena, and in particular to measurement of temperature distribution within a tomographic image. This invention relates to a diagnostic nuclear magnetic resonance apparatus that enables

(Technical background of the invention and its problems) In recent years, various nuclear magnetic resonance systems for diagnosis (NMR-CT) that project tomographic images of the human body using nuclear magnetic resonance phenomena have been developed. In this study, we used irradiation with electromagnetic waves at the resonant frequency when the hydrogen nuclei of water molecules that make up the human body respond to an externally applied magnetic field, and measured the scattering (relaxation time τ, etc.) of the hydrogen atoms in the human body. It is possible to know the distribution of water molecules in the body, to image the distribution of water molecules through computer processing, and to project a tomographic image of the human body on a CRT monitor, etc. This makes it possible to An extremely effective tomographic image projection means has been provided for cancer cells, etc., for which tomographic image projection was difficult even with X-ray CT.

However, in today's modern medicine, it is extremely important to know the humidity distribution of the internal organs of the human body in order to analyze in detail their physiological functions, as well as the tomographic projection images of the internal organs of the human body. It becomes.

Conventional tomographic image projection devices such as NMR, -CT and X-ray CT are devices that simply obtain tomographic images of the inside of the human body; is powerless. For this reason, an infrared thermography device was devised based on the measurement of the distribution density of radiant infrared rays. Although this device can measure the temperature distribution on the surface of the human body, it cannot measure the temperature distribution in internal organs of the human body. This problem cannot be easily avoided with methods that measure thermal radiation infrared rays, and therefore there is a need to devise a measurement method with a completely different operating principle from conventional devices. There is.

[Purpose of the invention]

An object of the present invention is to provide a diagnostic nuclear magnetic resonance apparatus that is capable of projecting a tomographic image of humidity distribution inside a human body through computer processing.

[Summary of the invention]

The gist of the present invention is to measure not only the response resonance frequency of hydrogen atoms in nuclear magnetic resonance phenomena, but also the band width of the absorption frequency band around it, and to determine the temperature distribution in a tomographic image from the measured band width. It is in.

That is, the present invention has a basic structure similar to conventional NMR-CT, but in the conventional apparatus, only a specific electromagnetic wave at a response resonance frequency of the hydrogen nuclear spin degree of freedom to an applied external magnetic field is measured through the irradiation and absorption process. , we revised the point that projected the distribution of water molecules in the body, and installed a frequency filter etc. that can measure not only the specific response resonance frequency but also the bandwidth of the absorption frequency band around it. A computer is used to calculate the thermal equilibrium temperature around water molecules measured from the band width, and a processing function is added to project the internal temperature distribution.

The basic operating principle of the device of the present invention having the above-mentioned basic structure is the same as that of conventional NMR-CT for human body tomographic images.
For internal temperature distribution tomograms, a method is used to calculate the local thermal equilibrium temperature of water molecules within the body measured by the fluctuation dissipation theorem from the absorption band width around the measured specific response resonance frequency described above. That is, if the peak frequency of the resonance frequency band obtained from the scattering distribution of the electromagnetic waves irradiated for measurement is ω0, and the bandwidth of the resonance frequency band is γ, then the spin of the hydrogen nucleus of the water molecule irradiated with the electromagnetic waves is The degree of freedom is approximated by precession vibration around the external magnetic field B with a frequency ω0. The movement is based on Einstein Langevin (E 1nstein-1-an (JeVin)).
According to the theory of Here, β is the proportionality constant of the damping term, ξ is the mean zero, and the sudden correlation ξ(1Δt)ξ(
It is a Gaussian stochastic process expressed as t)=2Dδ(tΔ). At this time, Einstein's formula provides a relational expression % that holds between the magnitude D of the rocking force, the damping term β, and the equilibrium temperature T of the thermal environment that is the cause of the rocking force. According to the above equation, the damping term β corresponds to the bandwidth γ of the resonant frequency band. Note that since kB is the Boltzmann constant and D is also a diffusion constant, the magnitude of the resonance width γ is ultimately proportional to the temperature.

γOCT Since the proportionality constant can be determined experimentally and is a universal value, it is possible to calculate the internal body temperature from the resonance width γ.

In view of these points, the present invention causes a nuclear magnetic resonance phenomenon to occur in a subject, detects the induced nuclear magnetic resonance signal,
A diagnosis in which tomographic image information reflecting at least one of the spin or relaxation time constant of hydrogen nuclei in the subject is obtained by obtaining projection information of a planned tomographic plane of the subject and performing image reproduction processing. In a nuclear magnetic resonance apparatus for use in a nuclear magnetic resonance apparatus, a means for measuring a band width within an absorption frequency band around the response resonance frequency of the hydrogen nucleus, and calculating a local thermal equilibrium temperature of a hydrogen atom within a subject from the measured band width. and a means for two-dimensionally analyzing the calculated local thermal equilibrium temperature to determine the temperature distribution within the tomographic image.

〔Effect of the invention〕

According to the present invention, it is possible to measure not only a human body tomographic image based on water distribution information but also the temperature distribution within this tomographic image. Therefore, its usefulness in modern medicine is enormous. Further, there are effects such as safe measurement being possible without imparting thermal disturbance to any part of the human body.

[Embodiments of the invention]

FIG. 1 is a schematic configuration diagram showing a diagnostic nuclear magnetic resonance apparatus according to an embodiment of the present invention. In the figure, reference numeral 1 denotes a table on which a subject 2 is placed, and around this table 1 four static magnetic field generating coils 3 are arranged. A current is supplied to the coil 3 from a power supply circuit 5 activated by a control command from a central processing unit (CPU) 4, thereby applying a static magnetic field to the subject 2. Although not shown in the figure, in addition to the coil 3 described above, a coil for generating a gradient magnetic field for tomographic plane slicing is also arranged.

On the other hand, around the table 1, a probe head 6 made of a coil is arranged. This probe head 6
is supplied with a high frequency current from a transmitting circuit 7 activated by a control command from the CPU 4, and applies a high frequency magnetic field to the subject 2 in a direction perpendicular to the static magnetic field. Further, a receiving circuit 8 is connected to the probe head 6 . Then, from the high frequency electromagnetic waves from the subject 2 detected by the probe head 6, the receiving circuit 8 measures the magnitude, relaxation time τ, etc. of the electromagnetic waves. In addition, the above electromagnetic wave is transmitted to the receiving circuit 8.
The signal is supplied to the bandwidth measurement circuit 9 via the . The bandwidth measuring circuit 9 is composed of a bandpass filter or the like capable of measuring the bandwidth of the absorption band, and this circuit 9 measures the bandwidth γ of the absorption frequency band around the response resonance frequency of the hydrogen nucleus. Information such as this bandwidth γ and the relaxation time τ measured by the receiving circuit 8 is then transferred to the CP.
It is to be sent to U'4.

CPLI4 calculates the distribution of water in a predetermined tomographic plane of the subject 2 based on the input relaxation time τ, etc.,
This provides fault information. Furthermore, the temperature distribution within the tomographic plane of the subject 2 is measured based on the band width γ. The tomographic information and temperature distribution information of the submerged subject 2 are displayed on a display 10 such as a C'RT display.

Next, the operation of the apparatus configured as described above will be explained.

First, a static magnetic field is applied in advance to the subject 2 by the coil 3,
If the nuclear magnetization vectors are oriented in the same direction and a high frequency magnetic field is applied perpendicularly thereto by the probe head 6, precession of the hydrogen nuclei will occur. Then, when this high-frequency magnetic field is removed, the state returns to its original state after a certain relaxation time τ. This relaxation time τ provides important information representing the chemical state of the element (H) during life. The relaxation time τ is measured from the electromagnetic waves emitted during this return process, and is displayed as a tomographic image through computer processing. Up to this point, conventional NMR-CT
It is similar to

On the other hand, in the static magnetic field applied by the coil 3, the spin degree of freedom of hydrogen nuclei in water molecules in the body absorbs electromagnetic waves (microwaves) with a frequency equal to the natural frequency of vibrational precession. known to radiate.

The local thermal equilibrium temperature around the hydrogen nucleus applies a thermal oscillation force to the vibrational precession, which in turn produces the energy dissipation effect of the spin degree of freedom. This energy dissipation creates a resonant absorption band around the natural frequency, the width of which is proportional to the dissipation constant. In detail, in the Langevin equation that approximately describes the motion of the above spin degree of freedom, Einstein's formula β-ksT
/D shows that the absorption band width γ (=β) is proportional to the absolute temperature T. Therefore, by measuring the absorption band width γ of the microwaves irradiated and scattered on the human body and performing calculation processing based on the above proportional formula, it is possible to know the local thermal equilibrium temperature of a desired part inside the human body, and the conventional NM
A human body internal temperature distribution tomographic image can be projected in accordance with the R-CT human body tomographic image.

That is, in this apparatus, in order to obtain temperature distribution information as shown in the flowchart of FIG. 2, the bandwidth measurement circuit 9 first measures the bandwidth γ of the absorption frequency band around the resonance frequency. Next, the CPU 4 calculates the local thermal equilibrium temperature of the measured water molecules in the body from the band width γ. Furthermore, the local thermal equilibrium temperature is two-dimensionally analyzed to determine the temperature distribution within the tomographic image. This temperature distribution is then displayed on the display 10. Note that this display 3 may be the temperature distribution information alone, or may be displayed in conjunction with a tomographic image based on the water molecule distribution.

In this manner, the present device makes it possible to project a tomographic image of the human body and a tomographic image of the temperature distribution within the human body, and is extremely useful in modern medicine.

Note that the present invention is not limited to the embodiments described above. For example, the number of static magnetic field generating coils and gradient magnetic field generating coils can be changed as appropriate depending on specifications. Moreover, each circuit shown in FIG. 1 is not limited in any way,
The key points are a means to measure the band width within the absorption frequency band around the resonance frequency, a means to calculate the local thermal equilibrium temperature of hydrogen atoms within the subject from the band width, and a tomographic image by two-dimensionally analyzing the equilibrium concentration. Any device may be used as long as it has a means for determining the temperature distribution within. 'In addition, various modifications can be made without departing from the gist of the present invention.

[Brief explanation of the drawing]

FIG. 1 is a schematic configuration diagram showing a diagnostic nuclear magnetic resonance apparatus according to an embodiment of the present invention, and FIG. 2 is a flowchart for explaining the operation of the apparatus. DESCRIPTION OF SYMBOLS 1... Table, 2... Subject, 3... Static magnetic field generation coil, 4... Central processing unit (CPU), 5...
・Power supply circuit, 6... Probe head, 7... Transmission circuit, 8... Receiving circuit, 9... Bandwidth measurement circuit, 1
0...Indicator.

Claims (1)

[Claims] (1) By causing a nuclear magnetic resonance phenomenon in a subject, detecting the induced nuclear magnetic resonance signal, and performing image reproduction processing by obtaining projection information of a planned tomographic plane of the subject, In a diagnostic nuclear magnetic resonance apparatus that obtains tomographic image information reflecting at least one of the spin or relaxation time constant of a hydrogen nucleus and provides it for diagnosis, the bandwidth within an absorption frequency band around the response resonance frequency of the hydrogen nucleus is A means for measuring, a means for calculating the local thermal equilibrium temperature of hydrogen atoms within the subject from the measured band width, and a two-dimensional analysis of the calculated local thermal equilibrium temperature to determine the temperature distribution within the tomographic image. What is claimed is: 1. A nuclear magnetic resonance apparatus for diagnosis, comprising: means for determining.