JPH01139047A - Probe apparatus of magnetic resonance diagnostic apparatus - Google Patents

Abstract

PURPOSE:To obtain a non-coil type probe apparatus, by generating a magnetic resonance phenomenon to the specific atomic nucleus inside the examinee disposed in a static magnetic field before detecting the induced magnetic resonance signal by a magnetic field sensor group. CONSTITUTION:A probe apparatus 13 is constituted by parallelly arranging magnetic field sensors 15 to the periphery of a cylindrical body 14 composed of a non-conductive and non-magnetic material and, since the magnetic field sensors 15 show extremely stable resistance characteristics by the magnetic field applied from the outside, the resistance value between lead wires 15d changes when there is variation in the external magnetic field. A power supply V is connected to the probe apparatus 13 so as to convert the change in the resistance value of each magnetic field sensor 15 to a current change and the output passing through a change-over device 15 is converted to a voltage signal through an I/V converter 17 and, since the resistance value of each magnetic field sensor 15 is varied by the induced magnetic resonance signal, a waveform wherein a high frequency magnetic field is converted to an electric signal is obtained to be guided to a signal processing system such as a receiver. Therefore, a signal can be detected without using a coil.

Description

[Detailed Description of the Invention] [Object of the Invention] (Industrial Application Field) The present invention relates to a magnetic resonance system that utilizes magnetic resonance phenomena to obtain diagnostic information such as slice images of specific parts of a subject. The present invention relates to a probe device for detecting magnetic resonance signals used in a diagnostic device, and particularly to a non-coil type probe device.

(Prior art) Magnetic resonance is a phenomenon in which an atomic nucleus with non-zero spin and magnetic moment placed in a static magnetic field resonantly absorbs and emits only electromagnetic waves of a specific frequency. The angular frequency ω0 (ωo　2πshi0.shi0
; Larmor frequency).

ω0−γH.

Here, γ is the magnetic quadratic ratio specific to the type of atomic nucleus, and Ho is the static magnetic field strength.

An apparatus that performs biological diagnosis using the above-mentioned principle processes the electromagnetic waves of the same frequency as the above induced after the above-mentioned resonance absorption, and calculates the nuclear density, longitudinal relaxation time TI, transverse relaxation time T2. Diagnostic information that reflects information such as flow and chemical shift, such as slice images of a subject, can be obtained non-invasively.

Collecting diagnostic information by magnetic resonance can excite all parts of a subject placed in a static magnetic field and collect signals, but there are limitations in the equipment configuration and clinical requirements for imaging images. Therefore, the actual device is designed to excite a specific region and collect its signals.

FIG. 5 shows the general configuration of this type of magnetic resonance diagnostic apparatus, and as shown in FIG. is equipped with a static magnetic field magnet (a static magnetic field correction shim coil may be added) 1 using a normal conduction or superconductivity method.

Furthermore, inside the magnet assembly MA, there is a gradient magnetic field generating coil 2 that generates a gradient magnetic field for imparting positional information of the induced site of the magnetic resonance signal, and a magnetic resonance signal (high frequency The probe device 3 includes a coil as a transmitting/receiving system for detecting a magnetic field as a voltage signal. Here, probe device 3
Although the transmitting coil and the receiving coil are arranged side by side or used in combination, the following description assumes that the element for signal detection is a probe device.

Furthermore, it controls the static magnetic field control system 4, the X-axis, Y-axis, and Z-axis gradient magnetic field power supplies 5, 6, and 7, the transmitter 8, the receiver 9, and the sequencer 10 that executes the imaging sequence (instruction to start imaging). , a console (not shown) for inputting imaging conditions such as slice site settings, etc.), a computer system 11 that performs signal processing of detection signals, and a display system 12.

According to the above configuration, the sequencer 10 is activated by operating the console to execute a sequence. As a result, the transceivers 8 and 9 are driven, and a rotating magnetic field is applied from the transmitting coil of the probe 3, and the gradient magnetic field power supplies 5, 6.7
A gradient magnetic field is applied from the gradient magnetic field generating coil 2, a slice region to be selectively excited is set, and signals from that region are collected from the receiving coil of the probe 3, and are imported into the computer system 11 to reconstruct the image. After processing,
A slice image of the region is obtained and displayed on the display system 12, making it possible to perform biological diagnosis.

In the above, a coil is used as the probe device, and the magnetic resonance signal is extracted as a voltage signal induced in the coil, but there are problems as described below.

(2) The coil has self-inductance and stray capacity with respect to the subject, and the impedance differs depending on the detection frequency ω0. For this reason, when it is necessary to change the nuclide to be detected or the strength of the static magnetic field, in other words, when imaging multiple nuclides such as 31p in addition to IH,
In a configuration using a rumble magnet, it is necessary to perform impedance matching with the signal transmission path and receiving circuit depending on the nuclide to be detected and the strength of the static magnetic field. Therefore, a matching circuit is provided in the receiving system, which not only complicates the circuit but also requires complicated matching adjustment, which is a problem.

■ Coupling occurs between the gradient magnetic field coil and the transmitting coil in the magnet assembly, so when the gradient magnetic field coil or the transmitting coil is operating, it is necessary to oven the receiving coil to protect the receiving circuit. There is. Therefore, a switching circuit is required, but this not only complicates the circuit, but also requires complex switching control when executing high-speed sequences, which is a problem.

(2) Since the receiving coil extracts the magnetic resonance signal as a voltage signal induced in the coil, there is sensitivity unevenness depending on the coil shape. In order to solve this problem, the current situation is to prepare coils such as head coils and surface coils that correspond to the shape of the signal detection site, but this is cumbersome to operate.

(Problems to be Solved by the Invention) In this way, in the conventional technology, since magnetic resonance signals are detected using coils, there are problems of impedance matching, coupling, and sensitivity unevenness. etc., which was a problem.

Therefore, an object of the present invention is to provide a non-coil type probe device.

[Structure of the Invention] (Means for Solving the Problems) The present invention has a structure in which the following measures are taken to solve the above problems and achieve the object. That is, the present invention is configured by arranging a plurality of magnetic field sensors whose resistance value changes in response to a magnetic field, and causes a magnetic resonance phenomenon to occur in a specific atomic nucleus within a subject placed in a static magnetic field. A magnetic resonance signal induced later is detected by the magnetic field sensor group.

(Function) According to such a configuration, the magnetic resonance signal (high frequency magnetic field) generated from the subject can be detected by the resistance value of each magnetic field sensor, and by converting this into an electric signal, the coil can be activated. It is now possible to obtain the same signal as the one used, and in this case, since no coil is used, there are no impedance matching problems, coupling problems, sensitivity unevenness problems, etc.

(Embodiment) An embodiment of the probe device of the magnetic resonance diagnostic apparatus according to the present invention will be described below with reference to the drawings.

FIG. 1 is a perspective view showing the configuration of the probe device of this embodiment;
Fig. 2 is a diagram showing the cross-sectional configuration of one channel of the magnetic field sensor used in the same example, Fig. 3 is a characteristic diagram of the same magnetic field sensor, and Fig. 4 is a diagram of the receiving system when using the probe device of the same example. FIG. 2 is a circuit diagram showing the configuration.

As shown in FIG. 1, the probe device 13 of this embodiment includes:
The magnetic field sensor 15 is preferably arranged in a matrix around a cylindrical body 14 made of a non-conductive and non-magnetic material.

As shown in FIG. 2, this magnetic field sensor 15 is equipped with a vacuum-tight insulated material such as liquid nitrogen or the like at a relatively high temperature (compared to liquid helium, etc.) in a heat insulating layer 15a that provides heat shielding between the outside air and the inside. A cooling layer 15b using a refrigerant that can cool a high-temperature superconducting material (described later) to near its critical temperature without requiring a A superconducting material 15c is arranged, and a heat insulating layer 15 is provided from both ends of this high temperature superconducting material 15c.
The structure is such that a lead wire 15d is led out outside a.

According to the magnetic field sensor 15 having the configuration shown in FIG. 2, as shown in FIG. 3, it exhibits an extremely stable resistance characteristic due to the magnetic field B applied from the outside, and when there is a fluctuation in the external magnetic field B, the resistance characteristics between the lead wires 15d The resistance value changes according to the characteristics shown in FIG.

Further, as shown in FIG. 4, a power supply V is connected to the probe device 13, and the change in resistance value of each magnetic field sensor 15 is converted into a change in current.

Further, a switch 16 is connected to the probe device 13, and each switch of this switch 16 is connected to each magnetic field sensor 15. The output (current signal) that has passed through the switch 16 is converted to a voltage signal through an I/V converter 17. Since the resistance value of each magnetic field sensor 15 fluctuates due to the induced magnetic resonance signal (high-frequency magnetic field), this converted output has a waveform obtained by converting the high-frequency magnetic field into an electric signal.

The converted output is then guided to a signal processing system such as the receiver 9 in FIG. 5. Note that the switch 16 is
In order to select the magnetic field sensor 15 to be operated according to the shape of the signal detection part, the switching operation is performed by a switching signal from a controller (not shown).

As described above, according to the probe device 13 of this embodiment, signal detection can be performed because no coil is used. In this case, the influence of the frequency of the detected magnetic resonance signal (high-frequency magnetic field) is small, and there is no need for a matching circuit or the like to compensate for the static magnetic field strength or the stray capacity between the nuclide and the subject.

In addition, since signal detection is performed without using a coil, there is no possibility of coupling even when the gradient magnetic field coil or transmitting coil is operating, so there is no need for a circuit to protect the receiving circuit. do not have. Furthermore, it does not affect the gradient magnetic field coil or shim coil.

Furthermore, since the magnetic field sensor 15 to be operated can be selected by the switch 16 and the detection area can be selected according to the shape of the subject (the shape of the signal detection site), there is no need to prepare probe devices of various shapes as in the past. There is no.

In the above example, the magnetic field sensor 15 is arranged in parallel to the cylindrical body 14, but even if the cylindrical body 14 is large enough to envelop the whole body of the subject, it is large enough to envelop only the head. It may be any size, and the size and shape are not critical. Further, various configurations regarding the arrangement of the magnetic field sensors in parallel can be adopted.

In addition, various modifications can be made without departing from the gist of the present invention.

[Effects of the Invention] As described above, the present invention is configured by arranging a plurality of magnetic field sensors whose resistance value changes in response to a magnetic field, and detects a specific atomic nucleus within a subject placed in a static magnetic field. Since the magnetic resonance signal induced after the magnetic resonance phenomenon is caused is detected by the magnetic field sensor group, the magnetic resonance signal (high frequency magnetic field) generated from the subject is converted into a resistance value by each magnetic field sensor. By converting this into an electrical signal, it is possible to obtain the same signal as using a coil.In this case, since a coil is not used, there are no problems with impedance matching or coupling. There are no problems such as uneven sensitivity or the like.

Therefore, according to the present invention, it is possible to provide a probe device for a non-coil type magnetic resonance diagnostic apparatus.

[Brief explanation of the drawing]

FIG. 1 is a perspective view showing the configuration of an embodiment of a probe device of a magnetic resonance diagnostic apparatus according to the present invention, FIG.
The figure is a characteristic diagram of the magnetic field sensor, Figure 4 is a circuit diagram showing the configuration of the receiving system when using the probe device of the same embodiment, and Figure f
The figure is a diagram showing an example of the configuration of a magnetic resonance diagnostic apparatus using a conventional probe device. 13... Probe device, 14... Cylindrical body, 15...
- Magnetic field sensor using high temperature superconducting material, 16... Switch, 17... I/V converter. Applicant's agent Patent attorney Takehiko Suzue Figure 2 Figure 3 Figure 4

Claims (4)

[Claims] (1) A magnetic field sensor is constructed by arranging multiple magnetic field sensors whose resistance value fluctuates in response to a magnetic field, and a magnetic resonance phenomenon is generated and then induced in a specific atomic nucleus within a subject placed in a static magnetic field. A probe device for a magnetic resonance diagnostic apparatus, characterized in that a magnetic resonance signal is detected by the magnetic field sensor group. (2) The probe device for a magnetic resonance diagnostic apparatus according to claim 1, wherein the magnetic field sensor utilizes the resistance characteristic of the high-temperature superconducting material exhibited by an external magnetic field near a critical condition. (3) A probe device for a magnetic resonance diagnostic apparatus according to claim 1, characterized in that only a desired one of a group of magnetic field sensors arranged in parallel is operated. (4) Any one of claims 1 to 3, characterized in that the magnetic field sensors are arranged in parallel around a cylindrical body, and the magnetic resonance detection site is arranged inside the cylindrical body. A probe device for a magnetic resonance diagnostic device according to.