JPH0333010B2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] This invention is used for cardiac imaging, which measures minute vibrations on the body surface of the apex of the heart, neck, radius, etc., which occur as the heart and blood vessels expand and contract. Regarding converters.

[Summary of the invention]

This invention relates to a cardiogram transducer for measuring minute vibrations on the body surface, in which a magnetic field generating element fixed on a film that is brought into contact with the body surface and a strip-shaped amorphous ferromagnetic thin strip are separated by a relative distance. A detection coil whose magnetic core is the amorphous ferromagnetic ribbon and which is arranged so as to change according to the displacement of the body surface, and a circuit for detecting its self-inductance are provided. By detecting changes in the magnetic field applied to a coil by converting them into changes in the coil's self-inductance,
This device allows minute vibrations on the body surface to be measured without applying pressure to the measurement site and without requiring special skill.

[Conventional technology]

Conventionally, in clinical diagnosis of heart or vascular diseases, cardiac diagnostics such as an apical pulsatogram, which measures chest wall vibrations based on myocardial activity, and a jugular venous wave, which measures vascular pulsations, are used in addition to electrocardiograms. It is being said. This cardiocardiogram is said to be an effective means for diagnosing valvular heart disease, congenital heart disease, carotid artery stenosis, etc., which are difficult to diagnose with an electrocardiogram.

Conventionally, as a cardiogram transducer for detecting such minute displacements, for example, an acceleration type transducer using an air conduction microphone or a piezoelectric element, and a Perrotte type pressure pulse wave transducer have been used. Among these, air conduction microphones convert body surface vibrations into sound pressure and detect them, and are also used as heartbeat microphones.

[Problem that the invention seeks to solve]

However, in the case of an acceleration type transducer using an air conduction type microphone, such a conventional cardiogram transducer does not connect the microphone attachment port to the body surface to measure vibrations on the body surface. It had to be pressed and brought into close contact with the body part in an optimal manner, and its use required skill and its operability was poor.

In addition, in the case of Perotste type pressure pulse wave transducers that use piezoelectric elements, although they are easier to operate than air conduction types, they are difficult to detect minute vibrations on the body surface because they press the measurement site. The problem was that it was difficult.

This invention aims to solve these problems.

[Means for solving problems]

Therefore, the cardiac converter according to this invention is
A film brought into contact with the body surface, a magnetic field generating element fixed on the film that generates a constant magnetic field, and arranged so that the relative distance between the magnetic field generating element changes depending on the displacement of the body surface. The above-mentioned method comprises a rectangular amorphous ferromagnetic thin strip, a detection coil having the amorphous ferromagnetic thin strip as a magnetic core, and a circuit for passing a constant minute alternating current through the coil to detect its self-inductance. The displacement of the body surface is detected by converting changes in the magnetic field applied to the detection coil due to changes in the relative distance between the magnetic field generating element and the amorphous ferromagnetic ribbon into changes in the coil's self-inductance. It was designed to do so.

[Effect]

According to the cardiogram converter configured in this way,
When the body surface is displaced and the relative distance between the magnetic field generating element and the amorphous ferromagnetic ribbon changes, the magnetic field applied by the magnetic field generating element to the coil whose magnetic core is the amorphous ferromagnetic ribbon changes; The displacement of the body surface is measured by converting the change in self-inductance of the detection coil into a change in the self-inductance of the detection coil. Therefore, it can be detected with a minute current, thereby achieving stable displacement detection without hysteresis loss. It can be easily operated without requiring special skill.

〔Example〕

Embodiments of the present invention will be described below with reference to the accompanying drawings.

FIG. 1 is a schematic diagram showing an embodiment of the present invention.

First, to explain its configuration, this cardiogram transducer is designed to measure minute vibrations on the body surface 5.
a film 10 brought into contact with the film 10;
A small magnet 6, which is a magnetic field generating element that generates a constant magnetic field, is fixed on the upper part of the amorphous amorphous amorphous body, and a rectangular amorphous amorphous material is arranged so that the relative distance between the small magnet 6 and the small magnet 6 changes depending on the displacement of the body surface 5. Ferromagnetic ribbon 2
and a detection coil 3 (hereinafter simply referred to as coil 3), which is an inductance element whose magnetic core is the amorphous ferromagnetic ribbon 2, and a constant minute alternating current is passed through this coil 3 to detect its self-inductance. A detection circuit 4 is provided, and a change in the magnetic field applied to the coil 3 due to a change in the relative distance between the small magnet 6 and the amorphous ferromagnetic ribbon 2 is converted into a change in the self-inductance of the coil 3 and detected. A minute displacement or vibration of the body surface 5 in the direction of arrow A in FIG. 1 is measured.

The film 10 is, for example, a circular polyimide film with a thickness of 25 μm, and a Ba-ferrite plastic magnet (Br=2.3KG) with a diameter of 3 mm and a thickness of 1.5 mm, for example, is attached to the upper surface of the center part. The formed small magnet 6 is fixed.

For example, the amorphous ferromagnetic ribbon 2 has a frequency
It is a high magnetic permeability material with zero magnetostriction and a coercive force Hc of about 0.02 oersted at 1KHz.As shown in Figure 2, its dimensions and shape are 0.5 mm in width, 16.6 μm in thickness,
It is made into a strip shape with a total length lr of 10 mm, and is adhered to a backing film 8 made of, for example, a celluloid board with an adhesive.

Then, the amorphous ferromagnetic ribbon 2 is
For example, it is fitted into the vertical groove 9a of a coil installation base 9 formed of a non-magnetic material such as aluminum and is bonded together, and the horizontal groove 9 formed on the coil installation base 9
In b, as shown in Fig. 3, an amorphous ferromagnetic thin ribbon 2 is inserted into the inside, and a bobbin 7 on which a coil 3 is wound, for example, with a coil length of 4 mm and a number of turns N = 150, is inserted into the outer periphery. It is hardened and fixed with adhesive 11.

This coil installation stand 9 is fixedly installed with a locking groove 9c formed on the lower surface placed on the upper part of an annular pedestal 12, and the front end 2a of the amorphous ferromagnetic thin ribbon 2
The position shown in FIG. 1 is located approximately at the center opening of the pedestal 12, and is arranged to receive the applied magnetic field of the small magnet 6 most easily.

Moreover, both ends 3 of the coil 3 are placed on the pedestal 12.
A lead wire 13 is provided for connecting the wires a and 3b to the detection circuit 4 for detecting self-inductance, and the two conductor portions 13a and 13b are fixed on the pedestal 12, and one end is connected to the coil 3, respectively. Connection terminals 14a, 1 connected to both ends 3a, 3b
4b.

A shield case 1 formed of, for example, permalloy (magnetic material) from above covers the amorphous ferromagnetic thin ribbon 2, the pedestal 12, etc.
A disc-shaped shield plate is formed from the same magnetic material as the shield case 1 from the lower side, a film 10 is attached to the lower surface of the shield plate, and a small magnet 6 is arranged in the center of the opening 15a. 15 is fixed to magnetically shield the amorphous ferromagnetic ribbon 2 and the like inside.

The detection circuit 4 is located outside the shield case 1, and as shown in FIG.
A small alternating current for detection of about i=1mA is connected to the resistor 1.
A constant current AC power supply 17 that flows through the coil 3 via the
and a detection amplifier 1 that detects, amplifies and rectifies the voltage at the connection point between the resistor 16 and the coil 3, that is, the voltage V _L generated between both ends 3a and 3b of the coil 3.
8 and a filter 19 for smoothing the output of the coil 3.
Detect the self-inductance L of .

V _L =jωLi L=V _L /jωi Next, the operation of this embodiment configured as described above will be explained.

The self-inductance L of the coil 3 according to this embodiment is proportional to the magnetic permeability μ of the amorphous ferromagnetic ribbon 2 used as the magnetic core. When there is no external magnetic field, the magnetic permeability μ is given by the initial magnetic permeability μi, but when there is an external magnetic field, the magnetic permeability μ is the point on the magnetization curve that corresponds to the external magnetic field (hereinafter referred to as the operating point).
It is necessary to use the reversible magnetic permeability μrev at .

Since the reversible magnetic permeability μrev monotonically decreases as the external magnetic field increases, as the amorphous ferromagnetic ribbon 2 that is the magnetic core approaches saturation, the reversible magnetic permeability μrev approaches 1 accordingly.

Therefore, when the small magnet 6 is brought close to the coil 3, the self-inductance L of the coil 3 gradually decreases as shown in FIG. 5, and the distance x between the amorphous ferromagnetic ribbon 2 and the small magnet 6 decreases. At the same time, the amorphous ferromagnetic ribbon 2 approaches saturation, and the self-inductance L of the coil 3 approaches the value of the inductance of the air core.

Furthermore, the magnetic field from the small magnet 6 increases rapidly as the distance x becomes smaller, but since the reversible magnetic permeability μrev of the magnetic core decreases as the magnetic core approaches saturation, the nonlinearity of the magnetic field is canceled out, and the distance x The area where the self-inductance L is proportional to (linear detection area)
appears.

Therefore, in the case of this embodiment, as shown by the solid line in FIG. ₅ , a linear detection area of approximately 1 mm width can be obtained centered at can measure minute vibrations.

FIG. 6 shows the film 10 in a free state (body surface 5
When the distance x is approximately 6.5 mm
FIG. 2 is a diagram showing the results of actually measuring the pulsation of the radial artery using the cardiac converter when set to .

At the time of this measurement, the cardiogram converter simply needs to bring the film 10, which has the small magnet 6 fixed to the center of the top surface, into contact with the measurement site on the body surface 5; in this case, the film 10 is As shown in the figure, when it comes into contact with the body surface 5, it moves inward by about 0.2 mm (approximately It vibrates in the direction of arrow A following the vibration.

Therefore, if the transducer for cardiac imaging according to the present invention is used, the weight of the transducer is added to the area around the measurement site on the body surface via the film 10, and only the weight of the small magnet 6 is placed on the measurement area. is applied only through the film 10, the vibration of the body surface can be faithfully detected without the measurement site on the body surface 5 being compressed by the weight of the transducer, and the pulsation as shown in Fig. 6 can be detected. Can be measured accurately.

In this way, there is no need to bring the entire transducer into close contact with the measurement site, and the small magnet 6 is inserted through the film 10.
The operability is also very good because you only have to touch the parts.

In addition, in this embodiment, the film 10 and the small magnet 6
Although it is assumed that the small magnet is circular, the shape is not limited to a circular shape as long as the small magnet can follow minute vibrations on the body surface.

In addition, the linear detection area shown in Fig. 5 of this cardiocardiogram converter and its detection sensitivity can be adjusted.
Total length lr of amorphous ferromagnetic ribbon 2 (Fig. 2)
If the distance x is also made shorter, the distance x can be moved to the smaller side as shown by the broken line. Since a large demagnetizing field in the opposite direction to the external magnetic field from the small magnet 6 is generated inside, the linear detection area similarly moves toward the smaller distance x.

Furthermore, the linear detection area and detection sensitivity cannot be changed by changing the composition of the amorphous ferromagnetic ribbon, its annealing (heat treatment) method, the size of the small magnet, or even by applying a bias magnetic field. can.

As described above, in the cardiogram converter according to the present invention, the self-inductance of the coil is proportional to the magnetic permeability μ of the magnetic core material of the coil, and this permeability μ
Note that in the presence of an external magnetic field, is proportional to the reversible magnetic permeability μrev at the operating point on the AC magnetization curve, and the self-inductance of the detection coil according to this reversible magnetic permeability μrev can be expressed as If detected each time, changes in the external magnetic field, that is, minute displacements of a small magnet brought into contact with the body surface via a film, can be measured.

Therefore, instead of passing a large alternating current through the coil and causing the magnetic flux fluctuations that would cause the magnetic core to swing to the saturation region on the magnetization curve as in the past, by passing a small alternating current, the magnetic core can be displaced in a non-saturated manner. By simply applying a small magnetic flux fluctuation within a linear detection region, the reversible magnetic permeability μrev at the operating point, that is, the self-inductance of the coil, can be detected from the voltage across both terminals of the coil.

Therefore, the alternating current flowing through the inductance detection coil can be as small as 1 mA or less, so there is little hysteresis loss and the operating point is always stable, and the coil does not require a large magnetomotive force. It can be easily manufactured because it can be wound using a bobbin rather than directly around the magnetic core.

〔Effect of the invention〕

As explained above, the cardiogram transducer according to the present invention changes the relative distance between the magnetic field generating element and the amorphous ferromagnetic ribbon in accordance with minute displacements of the body surface. Changes in the magnetic field applied to the detection coil due to changes in distance are converted into changes in the coil's self-inductance and detected to detect minute displacements on the body surface, so it operates with a minute current and has no hysteresis. Displacement can be detected stably at the operating point without loss.

Furthermore, the simple structure makes it easy to manufacture, and since the magnetic field generating element is fixed on the film to form an integrated transducer, it has excellent operability and can be easily operated without requiring special skill. Moreover, there is no pressure on the measurement site.

[Brief explanation of the drawing]

FIG. 1 is a schematic configuration diagram showing an embodiment of the present invention, FIG. 2 is an enlarged perspective view showing the installed part of the amorphous ferromagnetic thin ribbon, and FIG. 3 is a centering diagram of FIG. Fig. 4 is a circuit diagram showing an example of a circuit for detecting self-inductance, and Fig. 5 is an exploded perspective view showing the structure of the main part of a transducer for cardiac monitoring according to the present invention. A diagram showing the relationship between the distance x and the self-inductance L of the detection coil, Figure 6 shows the measurement of the radial artery pulsation using a cardiocardiogram transducer when the distance x is set to approximately 6.5 mm. FIG. 3 is a diagram showing the results. DESCRIPTION OF SYMBOLS 1... Shield case, 2... Amorphous ferromagnetic ribbon, 3... Detection coil, 4... Detection circuit, 5... Body surface, 6... Small magnet (magnetic field generating element), 10... Film .

Claims (1)

[Claims] 1. A film brought into contact with the body surface, a magnetic field generating element fixed on the film that generates a constant magnetic field, and arranged so that the relative distance between the magnetic field generating element changes depending on the displacement of the body surface. comprising a rectangular amorphous ferromagnetic thin strip, a detection coil having the amorphous ferromagnetic thin strip as a magnetic core, and a circuit for flowing a constant minute alternating current through the coil to detect its self-inductance, A change in the magnetic field applied to the detection coil due to a change in the relative distance between the magnetic field generating element and the amorphous ferromagnetic ribbon is converted into a change in the self-inductance of the coil and detected, thereby detecting the displacement of the body surface. A transducer for cardiac diagnostics, characterized in that it detects.