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JPH0515505

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DESCRIPTION JPH0515505
[0001]
BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a
medical diagnostic apparatus for diagnosis by applying a high frequency magnetic field to a
patient's body, and more particularly to a medical diagnostic apparatus having a noise
suppressor for actively eliminating noise in the vicinity of the ear of the patient. It relates to the
device.
[0002]
2. Description of the Related Art A medical diagnostic apparatus having a means for supporting a
patient's body in the center of a chamber and generating a magnetic field by a magnetic
generator provided at the periphery to diagnose the patient and generate noise at that time. For
example, in a conventional apparatus for nuclear magnetic resonance apparatus, as described in
JP-A-61-279238, the static magnetic field in the bore formed inside the cryostat is opposed to
each other in the XY direction of the cross section cut at right angles. The pair of wedge-shaped
gradient magnetic field coils arranged as described above are directly fixed on the outer
periphery of a cylindrical bobbin made of epoxy resin or the like having a very high resistivity. A
periodic pulse-like current is supplied to the gradient magnetic field coil to generate a periodic
gradient magnetic field in the bore to obtain a three-dimensional cross-sectional image signal of
the patient. When this current flows, an electromagnetic force according to Fleming's left-hand
rule acts on a lead through which current flows in a direction transverse to the static magnetic
field in the bore, which acts to deform the gradient magnetic field coil. Shock load was applied to
the bobbin. In order to cause the bobbin to vibrate due to this load and generate enormous noise,
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vibration isolation rubber is trapped between the bobbin and the gradient magnetic field coil, and
furthermore, the gradient magnetic field coil is tied on the vibration isolation rubber with a band.
[0003]
In addition, as described in JP-A-62-261105 and JP-A-62-229906, a pair of wedge-shaped
gradient magnetic field coils are cylindrical with an extremely high resistivity epoxy resin or the
like. Directly on the bobbin which is the first support of The gradient magnetic field coil is
disposed so that the static magnetic field is uniform in the bore, and periodic current is supplied
to the gradient magnetic field coil to perform two-dimensional cross-sectional imaging of the
patient in the bore, and periodical during static magnetic field The gradient magnetic field
distribution was given. Therefore, when the current flows, the static magnetic field generates a
radial electromagnetic force on the circumferential portion of the gradient coil.
[0004]
In addition, there are techniques described in Japanese Patent Application Laid-Open Nos. 63158047 and 62-239503 as devices for supporting the gradient magnetic field coil.
[0005]
Although all of the above-described conventional examples relate to the supporting method of
the gradient magnetic field coil, a headset having a configuration to substantially cover the
earplugs and ears is attached to the patient to try to reduce the noise associated with the
electromagnetic force. There is.
[0006]
In the medical diagnostic apparatus as described above, since the gradient magnetic field coil is
directly fixed on the bobbin, when a pulse current flows, the bobbin vibrates by the
electromagnetic force and the entire bobbin is There was a problem that loud noise was
generated and the patient felt uncomfortable.
Furthermore, due to the pulse-like load by the electromagnetic force, the gradient magnetic field
coil was deformed by the amount of contraction due to the load of the vibration-proof rubber
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entrained with the bobbin, and was precisely generated by the gradient magnetic field coil There
is a problem that the magnetic field distribution in the bore is changed and distortion of the
image different from the actual one is generated in the image.
[0007]
Further, in the method of attaching the earplug or the headset to the patient, at least a part of the
earplug or the headset is in direct contact with the body, causing a problem that the patient feels
pressured.
[0008]
The present invention has been made to solve the above-mentioned problems, and in a medical
diagnostic apparatus in which a great deal of noise is present, without lowering the diagnostic
performance, it is possible to further reduce the psychological and psychological effects on
patients by noise reduction measures. An object of the present invention is to provide a medical
diagnostic apparatus provided with a device capable of muffling this noise without giving a
feeling of physical oppression or discomfort.
[0009]
[Means for Solving the Problems] In order to achieve the above object, the medical diagnostic
apparatus of the first invention of the present invention lays a patient inside an open-ended
cylinder located at the center of the chamber. The support base and a magnetic generator on the
outer periphery of the cylinder, the magnetic generator periodically applies a magnetic field to
the patient's body, and detects an electromagnetic wave generated from the body in response to
the magnetic field; In a medical diagnostic apparatus for processing the detected signal by a
computer to create a cross-sectional image of a body, an error signal detection means disposed
on a support near a patient's ear and detecting noise generated during operation of a magnetic
generator Vibration detection means attached to the inner surface of the cylindrical body for
detecting the vibration of the cylindrical body when the magnetic generator is in operation, and
inverting the phase of the vibration signal from the vibration detection means and detecting the
amplitude of the vibration signal as an error signal Detection means A phase and amplitude
control means in proportion to the magnitude of the noise signal to generate a mute signal of, is
characterized in that a and sound generating means for generating a sound by digestion sound
signal.
[0010]
A capacitor type microphone is preferably used as the error signal detecting means, and a
piezoelectric type pickup is preferably used as the vibration detecting means.
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[0011]
Further, in order to achieve the above object, the medical diagnostic device of the second
invention is attached to the inner surface of the cylindrical body in the medical diagnostic device
of the first invention and detects the vibration of the cylindrical body at the time of operation of
the magnetic generator. Instead of the signal from the vibration detection means, a signal from
the drive signal detection means for detecting a drive signal for driving the magnetic generator is
input to the phase / amplitude control means.
[0012]
Furthermore, in each of the medical diagnostic apparatus of the first and second inventions,
adding a music signal addition function and volume / sound quality control means to the sound
generation means is effective in reducing the patient's feeling.
[0013]
Further, in order to achieve the above object, the medical diagnostic apparatus of the third
invention comprises a support base for laying a patient in the inside of a cylinder open at both
ends located in the center of the chamber and a magnetism generator on the cylinder outer
periphery. The magnetic generator periodically applies a magnetic field to the patient's body,
detects an electromagnetic wave generated from the body in response to the magnetic field, and
processes the detected signal by the computer to generate a cross section of the body. In a
medical diagnostic apparatus for producing an image, error signal detection means disposed
outside the cylinder away from the patient's ear on the support and detecting noise generated
during operation of the magnetic generator and attached to the inner surface of the cylinder
Detection means for detecting the vibration of the cylinder during operation of the magnetic
generator, and inverting the phase of the vibration signal from the vibration detection means and
detecting the amplitude of the vibration signal from the noise signal from the error signal
detection means In size A phase / amplitude control means for generating a muffling signal by
multiplying the transmission characteristic of the sound wave transmission path consisting of the
space from the ear to the error detecting means and providing sound generating means for
generating sound by the muffling signal It is characterized by
[0014]
Furthermore, in order to achieve the above object, in the medical diagnostic apparatus of the
fourth invention, in the medical diagnostic apparatus of the third invention, an error is caused
simply by leaving the space outside the cylinder away from the ear of the patient's ear While the
signal detection means is arranged, a nonmagnetic nonmetal tube drawn out of the patient's ear
03-05-2019
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to the outside of the cylinder is used as a sound wave transmission path and an error signal
detection means is arranged at the tip of the tube. The amplitude control means is characterized
in that it generates a muffling signal by multiplying the transmission characteristic of the sound
wave transmission line consisting of a tube.
[0015]
Further, in order to achieve the above object, the medical diagnostic apparatus of the fifth
invention comprises a support base for laying a patient in the inside of a cylinder open at both
ends located in the center of the chamber and a magnetism generator on the cylinder outer
periphery. The magnetic generator periodically applies a magnetic field to the patient's body,
detects an electromagnetic wave generated from the body in response to the magnetic field, and
processes the detected signal by the computer to generate a cross section of the body. In a
medical diagnostic apparatus for producing an image, an error signal detection means disposed
on a support base away from a patient's ear and out of a cylinder to detect noise generated
during operation of a magnetic generator and driving the magnetic generator Drive signal
detection means for detecting a drive signal; and reversing the phase of the drive detection signal
from the drive signal detection means to make the amplitude of the drive detection signal
proportional to the magnitude of the signal from the error signal detection means; The A phase
and amplitude control means for generating a mute signal by multiplying a transmission
characteristic of the acoustic wave transmission line made of a space of up to over detecting
means is characterized by comprising a sound generating means for generating a sound by
digestion sound signal.
[0016]
Furthermore, in order to achieve the above object, in the medical diagnostic apparatus of the
sixth invention, in the medical diagnostic apparatus of the fifth invention, an error is caused
simply by leaving the space outside the cylinder away from the ear of the patient's ear While the
signal detection means is arranged, a nonmagnetic nonmetal tube drawn out of the patient's ear
to the outside of the cylinder is used as a sound wave transmission path and an error signal
detection means is arranged at the tip of the tube. The amplitude control means is characterized
in that it generates a muffling signal by multiplying the transmission characteristic of the sound
wave transmission line consisting of a tube.
[0017]
Then, it is desirable from the viewpoint of the accuracy of the magnetic field in the cylinder that
the drive signal detection means, the phase / amplitude control means and the sound generation
means be disposed outside the chamber.
03-05-2019
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[0018]
In the medical diagnostic apparatus according to the first aspect of the present invention, when
the magnetic field is periodically applied to the patient's body by the magnetic generator, noise is
generated inside and outside the chamber including the cylinder, The noise in the tube is
extremely loud.
[0019]
When this noise occurs, the error signal detection means detects the noise in the vicinity of the
ear of the patient lying on the support table, and the vibration detection means detects the
vibration of the inner surface of the cylinder, and the phase / amplitude control means is from
the vibration detection means A noise cancellation signal is generated by inverting the phase of
the input vibration signal and making the amplitude of the vibration signal proportional to the
magnitude of the noise signal input from the error signal detection means, and the sound
generation means is propagated to the vicinity of the ear by the input sound cancellation signal.
Noise that is out of phase with the noise, thus counteracting the noise in the vicinity of the ear
and quieting the patient's ear.
[0020]
In the medical diagnostic apparatus of the second invention, the drive detection signal from the
drive signal detection means has a phase instead of the vibration signal from the vibration
detection means for detecting the vibration of the cylinder in the medical diagnostic apparatus of
the first invention. • Input to the amplitude control means.
Others are the same as the medical diagnostic apparatus of the first invention.
Furthermore, in each of the medical diagnostic apparatus of the first and second inventions, the
addition function of the music signal sends music through the sound generation means, and the
volume / sound quality control means is used to adjust the volume and sound quality of the
music.
By letting the music flow in this way, the patient's feeling can be relieved.
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[0021]
In the medical diagnostic device of the third invention, the error signal detection means is
installed at the patient's ear in the medical diagnostic device of the first invention, while the error
signal detection means is separated from the patient's ear It is placed outside the body.
Therefore, in order to convert the noise detected by the error signal detection means into the
noise of the patient's ear, the phase / amplitude control means outputs a sound signal from the
error signal detection means in a space from the ear to the error detection means. The noise is
corrected according to the transfer characteristic of the transmission line to generate a mute
signal.
Others are the same as the medical diagnostic apparatus of the first invention.
That is, the phase / amplitude control means reverses the phase of the vibration signal from the
vibration detection means, and makes the amplitude of the vibration signal proportional to the
magnitude of the noise signal from the error signal detection means to generate a silence signal.
Generates an acoustic wave of opposite phase to the noise transmitted to the vicinity of the ear
by the muffling signal, thus the acoustic wave cancels out the noise near the ear and makes the
patient's ear quiet.
[0022]
According to the medical diagnostic device of the fourth aspect of the invention, in the medical
diagnostic device of the third aspect of the invention, the error signal detection means is
disposed apart from the patient's ear and simply using a space as the sound wave transmission
path outside the cylinder. A tube is installed as a sound wave transmission line between the ear
of the patient and the error signal detection means.
Therefore, the phase / amplitude control means multiplies the transfer characteristic of the
sound wave transmission path consisting of the tube to generate the muffling signal.
Others are the same as the medical diagnostic apparatus of 3rd invention.
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[0023]
In the medical diagnostic apparatus of the fifth invention, instead of the signal from the vibration
detection means used in the medical diagnostic apparatus of the third invention, the signal from
the drive signal detection means for detecting the drive signal of the magnetic generator is used.
The other points are the same as those of the medical diagnostic apparatus of the third aspect of
the present invention, except for the difference.
[0024]
The medical diagnostic apparatus of the sixth invention uses the signal from the drive signal
detection means for detecting the drive signal of the magnetic generator instead of the signal
from the vibration detection means used in the medical diagnostic apparatus of the fourth
invention. The other is the same as the medical diagnostic apparatus of the fourth invention.
[0025]
The details of the structural features and operations of the present invention will be described
using the embodiments described below with reference to the accompanying drawings.
[0026]
Embodiments of the present invention will be described hereinbelow with reference to the
drawings.
FIG. 1 is a schematic view of a medical diagnostic apparatus according to a first embodiment of
the present invention, and FIG. 2 is a cross-sectional view taken along line II-II of FIG.
[0027]
As shown in FIG. 1, the medical diagnostic apparatus of the first embodiment is a cylindrical
bobbin having a chamber 1 and a space at the center of the chamber 1 for accommodating a
patient 2 as a medical related part. 6, a gradient magnetic field coil 5 fixed to the outer periphery
of the bobbin 6, and an electromagnet 4 surrounding the gradient magnetic field coil 5, and in
the cylindrical bobbin 6 a table 7 for the patient 2 to lie is provided It is done.
03-05-2019
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[0028]
Furthermore, capacitive microphones 13R and 13L for detecting noise are provided on the table
7 in the vicinity of both ears of the patient 2 as a sound deadening related part, and the inner
surface of the bobbin 6 is piezoelectric for detecting the vibration of the bobbin 6. A type of
vibration acceleration pickup 16 (pickup 16) is attached.
Outside the chamber 1, an error signal detection circuit 19 connected to the microphones 13R
and 13L via cables 12R and 12L and a vibration detection circuit 18 connected to the pickup 16
via an output cable 17 are provided, and vibration is further generated. A phase / amplitude
control means 11 which inverts the phase of the signal from the detection circuit 18 and makes
the amplitude thereof proportional to the magnitude of the signal from the error signal detection
circuit 19, and a mute signal from the phase / amplitude control means 11 And sound producing
means 14 for generating a noise canceling noise based on
[0029]
An electric signal is transmitted from the medical diagnosis control device 8 through the cable
10 and the electric signal flows to the gradient coil 5 and the electromagnet 4. A gradient electric
field and a high frequency magnetic field are applied to the human body of the patient 2 inside.
The magnetic field causes nuclear nuclei of hydrogen in the human body to undergo nuclear
magnetic resonance, whereby a weak electromagnetic wave is generated from the human body.
An image of the cross section of the human body is obtained by detecting this nuclear magnetic
resonance signal as an electromagnetic wave and processing it with a computer (not shown) to
image information on the distribution of proton density and relaxation time in the human body.
[0030]
The measurement is repeated several hundred times in order to collect one slice data required
for an image of one cross section of the human body.
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Since one measurement time is around 1 second, it takes several minutes to shoot one slice
(cross section), and usually the measurement value is increased to improve the S / N (signal to
noise) ratio. Since averaging is performed, the photographing time becomes longer.
During operation of the device, the bobbin 6 is vibrated by the electromagnetic force, and the
vibration causes a great deal of noise to be generated repeatedly for a long time, resulting in
great pain for the patient 2.
[0031]
In the present embodiment, the pickup 16 detects the vibration acceleration of the bobbin 6 and
the output thereof is transmitted as a vibration signal through the output cable 17 to the
vibration detection circuit 18 where it is amplified, and is further amplified by the phase /
amplitude control means 11. Phase and amplitude are adjusted.
Based on the signal adjusted by the phase / amplitude control means 11, the sound generation
means 14 for noise cancellation generates a sound for muting the noise.
The microphones 13R and 13L provided near the ear of the patient 2 pick up noises in the
vicinity of the ear 20R and 20L of the patient 2 and the synthesized sound of the sound from the
sound generator 14, respectively, and output them as error signals through the output cables
12R and 12L. It is transmitted to the error signal detection circuit 19.
[0032]
The phase / amplitude control means 11 reverses the phase of the vibration signal and increases
or decreases the vibration amplitude in proportion to the magnitude of the error signal caused by
the noise, and the amplitude value of the output signal of the error signal detection circuit 19 (in
other words, For example, since the noise acts to minimize the magnitude of the noise, it is
possible to substantially reduce the sound wave combining the noise caused by the vibration of
the bobbin 6 and the sound generated from the sound generating means 14.
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Here, the error signal indicates the signal of the microphone that detects the sound in the vicinity
of the ear, but the error means a noise portion that can not be erased by the sound generation
means, so the output signal of the microphone is called an error signal. .
[0033]
By the way, in the method of detecting by the microphone the noise itself in the bobbin 6
generated by the vibration to detect the vibration which is the source of generating the noise, the
sound wave generated from the sound generating means 14 is collected by this microphone
Since the output signal is fed back to the sound wave generated from the sound generation
means 14, howling occurs and stable active control can not be realized.
The present invention, as shown in FIG. 1, adopts a method of detecting the vibrational
acceleration of the bobbin 6, so that howling does not occur and a good muffling effect can be
obtained.
[0034]
Here, the sound generation means 14 used to cancel the noise is provided outside the chamber 1
in order to prevent a malfunction under a high magnetic field or a deterioration in the image
quality of the cross section of the human body. Furthermore, as the error signal detection means,
a capacitive microphone 13 capable of collecting sound under a high magnetic field is provided
in the vicinity of both ears of the patient 2 in the bobbin 6. In addition, since an electret
condenser microphone having a very small size of about several mm and high sensitivity as the
capacitive microphone 13 can be obtained recently, even if the microphone 13 is provided near
the ear of the patient 2, the image quality is deteriorated. can avoid. Furthermore, in the
conventional method in which a headset or earplugs are used to close or cover the ears of the
patient 2, the headset or earplugs contact a part of the human body and give the patient 2 a
feeling of compression. In the embodiment, since the open space between the bobbin 6 and the
head of the patient 2 can be muffled in a noncontact manner, the patient 2 does not have a
feeling of pressure. Incidentally, as shown in FIG. 2, when these microphones 13R and 13L are
fixedly supported on the table 7 of the patient 2, the patient 2 and its supporting table 7 move in
order to take a slice cross section of each part of the human body. Also in this case, the
microphone 13 can always be held near the ear of the patient 2.
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[0035]
Next, a second embodiment of the present invention will be described with reference to FIG. 3
and FIG. FIG. 3 is a cross-sectional view of the medical diagnostic apparatus of the second
embodiment, and FIG. 4 is a block diagram showing the flow of error signal processing. In this
embodiment, two sound generating means are provided, a point using a magnetic control signal
for outputting a noise source signal from a medical diagnostic apparatus, and phase / amplitude
control means 11 in which the sound generator controls two. The second embodiment is
basically the same as the first embodiment. Incidentally, in the first embodiment, there is one
sounding means, and the noise source signal is obtained from the pickup 16 attached to the
bobbin 6.
[0036]
In the present embodiment, two sounding devices 23R, 23L for canceling noise are provided
outside the chamber 1 so as to face two open space areas in the vicinity of the ear 20R, 20L of
the patient 2. By providing two sound generators, since the sound waves generated from each
sound generator can be individually controlled, the effect of increasing the amount of muffling
and expanding the muffling area can be obtained. These effects increase as the number of
detection points of the error signal and the number of sound generation means increase, but on
the other hand, the phase and amplitude adjustment time increases and the followability to
temporal changes of noise and sound speed deteriorates. It has the disadvantage of
[0037]
The circuit for processing the error signal shown in FIG. 4 comprises two capacitive microphones
13R and 13L for error signal detection, their output signal cables 12R and 12L, and an error
signal detection circuit 19. Noise generation source signal detection means 25 comprising error
signal detection means 21; noise generation source signal detection circuit 18 for detecting an
output signal of magnetic control by medical diagnostic control device 8 as noise source signal;
error signal detection means 21 and phase-amplitude control means 11 for processing signals
from the noise generation source signal detection means 25; and driving the sound-production
units 23R, 23L by signals of the two sounding units 23R, 23L and the phase-amplitude control
means 11 And sound producing means 14 for noise cancellation, which comprises a drive circuit
22. The output signal of the medical diagnostic controller 8 is a signal synchronized with the
start of one acquisition of slice data. Since the output signal of the medical diagnostic control
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device 8 is input to the phase / amplitude control means 11 through the detection circuit 18 of
the detection means 25 as a noise source signal, instability due to howling as in the first
embodiment described above No silent action can occur.
[0038]
FIG. 5 is a block diagram showing the configuration of the phase / amplitude control means 11 of
the second embodiment. An example of using two error signals 28R and 28L and two sound
generator drive signals (muffling signals) 27R and 27L to mute the open space areas of the two
ears of the patient 2 by adaptive control in a time division manner Show.
[0039]
The signal input / output unit of the phase / amplitude control means 11 has an A / D conversion
circuit for converting an analog signal to a digital signal in the case of input and a D / A
conversion circuit for converting a digital signal to an analog signal in the case of output Signal
conversion means 11a and 11c are provided. By the way, in the case of the present embodiment,
each sound wave emitted from the two sound generators propagates to the two microphones for
error signal detection provided in the two muffling areas, so there are four propagation rules. To
occur. That is, the sound wave from the left sound generator 23L propagates to the left
microphone 13L and also to the right microphone 13R, and the sound wave from the right sound
generator 23R also propagates to the microphones 13R and 13L. Therefore, in order to mute the
two regions, it is necessary to adjust the phase and amplitude for the four routes. In general,
when m regions are to be muffled using m sound generators, control using adaptive digital filters
such as adaptive FIR filters is required for m × n routes respectively. . As a result, when the
number of sound generators and the number of muffling areas is increased, a large amount of
calculation occurs, resulting in an increase in memory size and an increase in adaptation time,
resulting in a problem that the adaptation range of the active muffling method is extremely
limited.
[0040]
In the phase / amplitude control means 11 of the second embodiment, the number of adaptive
FIR filters is two, which is the same as the number of sound generators. The adaptive FIR filter
determines, for the noise generation source signal 26, four transmission characteristics between
03-05-2019
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the above-mentioned sound generator and each error microphone, that is, four FIR filters, for
example, impulse response coefficient vectors C1L and C1R. , C2L and C2R (denoted as C1L to
C2R). For each combination of the signal obtained by this and two error signals, drive input
signals of the respective sounders 23L and 23R are created while performing time-division
switching for each unit sample of the signal. In this case, the filter coefficients of the adaptive FIR
filters L and R are varied so as to minimize the magnitude of the error signal output using an
adaptive algorithm such as LMS (least mean square) algorithm. The impulse response coefficient
vectors C1L to C2R that determine the four FIR filters are obtained by measurement in advance
before diagnosis. When the patient's ear base position is moved to diagnose a plurality of
locations on the human body, the impulse response coefficient vectors C1L to C2R are measured
each time before diagnosis, and this result is used. Alternatively, coefficient vectors C1L to C2R at
a plurality of patient ear positions are measured in advance and made into a database, and in
diagnosis, active noise reduction control is performed using coefficient vectors C1L to C2R
corresponding to each patient ear position in each case. I do. The storage and reading / writing
means of the coefficient vector necessary for this are not described in the figure, but are included
in the present invention.
[0041]
In the block diagram shown in FIG. 5, the phase / amplitude control means 11 can be realized by
hardware high speed digital processor (DSP), A / D converter, D / A converter and software for
controlling them. According to this configuration, even if the number of sounding units and
muffling areas is increased, the amount of calculation does not increase so much, so limitation of
application range or cost increase due to increase of memory amount and increase of adaptation
time, decrease of muffling effect Can be prevented.
[0042]
A third embodiment of the present invention will now be described with reference to FIG. FIG. 6
is a signal block diagram of the sound generation means 14 for canceling the noise. The medical
diagnostic apparatus of this embodiment is the second embodiment added with the function of
playing music, which will be described below. The sound generation means 14 of the present
embodiment generates an addition signal of the noise cancellation signals 27R and 27L and the
output signal of the music signal source 29 by the addition means 30R and 30L, and uses this
signal to generate the speaker driving amplifier 22R. , 22L, and generates sound from the sound
generators 23R, 23L.
03-05-2019
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[0043]
This active noise reduction method is a method of muffling only the sound wave having a high
correlation with the noise generation source signal among the sound waves in the vicinity of the
ear of the patient 2, and the vibration of the bobbin 6 or the diagnostic control device as this
noise generation source signal. Since the output signals of 8 are used, the music is transmitted to
the patient 2 as it is without being muted among the sound waves generated from the sound
generators 23R and 23L. As a result, the noise can be masked by this music, so that its
annoyance can be alleviated, which leads to further comfort. Although not shown in FIG. 6, a
method of adding a sound signal for transmitting information to the patient 2 to the noise
cancellation signal is also included in this embodiment.
[0044]
A fourth embodiment of the present invention will be described with reference to FIG. 7 and FIG.
FIG. 7 is a cross-sectional view of the medical diagnostic apparatus of the fourth embodiment,
and FIG. 8 is a signal block diagram of the phase / amplitude control means 11. In this
embodiment, as shown in FIG. 7, the microphones 13R and 13L for detecting an error signal are
spatially separated from the muffling area in the vicinity of the ear of the patient 2 to muffle the
noise of the patient 2 ear. Only the patient 2 is present in the bobbin 6, and there is no other
active noise reduction means such as a microphone. In this embodiment, the microphones 13R
and 13L for error signal detection, the output cables 12R and 12L of these, and the sounders
23R and 23L for canceling the noise are provided outside the chamber-1. The medical diagnostic
apparatus of this embodiment is the same as the second embodiment except that a microphone
for detecting an error signal is provided outside the chamber 1, and the correction filter of the
phase / amplitude control means 11 described below is provided. The other configuration is the
same as that of the second embodiment.
[0045]
In FIG. 8, filter coefficients D1L, D1R, D2L, and D2R represent impulse response coefficient
vectors between the sounding positions of the sound generators 23R, 23L and the two sound
sources of the patient 2 at both ends. Furthermore, 31R and 31L indicate correction filter
coefficients obtained by Fourier inverse transformation of the ratio of the noise spectrum at each
position of the muffling position and the microphone 13R and 13L installation position.
03-05-2019
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According to the correction filter coefficients 31L and 31R, noise is generated from the
microphones 13R and 13L when a signal is supplied to the gradient magnetic field coil 5.
However, another microphone is generated at the muffling position near the ear only at the
preliminary operation before the start of diagnosis. It is determined by executing the above
calculation after measuring two noise spectra and measuring each noise spectrum. Furthermore,
the correction filter coefficients 31R and 31L represent impulse response coefficient vectors
between two other microphones and the regular microphones 13R and 13L, and as a
measurement method, for example, the reversibility of a capacitive microphone is used. By using
a regular or another microphone as a speaker and emitting an M-sequence modulated signal
sound before operation, it is possible to measure the transfer characteristic between this and
another or regular microphone.
[0046]
Here, the output signal of the medical diagnostic control device 8 is used as the noise generation
source signal, and the microphones 13R and 13L provided outside the area of the ear 2 of the
patient 2 and outside the chamber-1 and the sounders 23R and 23L. In the case where the
medical diagnostic apparatus is constructed using the above-mentioned, muffling in the vicinity
of both ears can be remotely performed by muffling means outside the chamber. As a result, the
cause of the decrease in the diagnostic performance is completely eliminated, and the ones that
restrain the posture, position and size of the patient 2 do not exclude the bobbin 6 and the table
7.
[0047]
Next, a fifth embodiment of the present invention will be described. FIG. 9 is a cross sectional
view and a signal processing block diagram of the medical diagnostic apparatus of the fifth
embodiment. While microphones 13R and 13L and sounders 23R and 23L are provided outside
chamber 1, hollow tubes 33R, 33L, 32R and 32L made of nonmagnetic nonmetals, for example,
plastic materials are provided at their respective tips. It is a method of attaching and using the
inside of these tubes as a transmission path of an acoustic wave. This embodiment is basically the
same as the fourth embodiment except that the above-mentioned tube is used. In this
embodiment, although the output signal 10 of the diagnostic control device 8 is used as the noise
generation source signal, a signal of vibration acceleration of the wall surface of the bobbin 6
may be used. If the other mouth of these tubes is located in the chamber 1 and the tubes are
sound transmission means, noise from the patient's ear can be silenced and no metal or magnetic
material is present in the bobbin 6 Since the disturbance of the magnetic field does not occur and
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as a result, it is not affected by the diagnostic performance, high image quality can be obtained.
The present invention also includes a method in which only the hollow tubes 33R and 33L
connected to the microphones are used and the sound generating means is provided outside the
chamber 1 without using the hollow tubes 32R and 32L connected to the sound generator. Also
in this method, as described above, no particular change is observed in the muffling effect.
[0048]
A sixth embodiment will now be described with reference to FIGS. 10 and 11. FIG. 10 is a block
diagram showing the cross section and the signal processing circuit of the medical diagnostic
apparatus of the sixth embodiment. FIG. 11 is a signal block diagram of the sound generation
means 14 for canceling noise. Based on the signal 24 indicating the condition of the blood flow
in the affected area obtained by the diagnostic operation, for example, the sound volume and
sound quality in the vicinity of the ear of the patient 2 are changed by the sound generating
means 14 The diagnosis of the patient 2 can be performed under various sound environments
inside. The present embodiment is the same as the second embodiment except that the volume
and sound quality of the sound generation means 14 are made variable according to the
symptoms of the patient 2.
[0049]
In FIG. 11, the signals output from the signal source 34 and input to the addition means 30R,
30L are controlled by the sound signal control means 35R, 35L based on the output 24 of the
diagnostic control device 8. This signal and the noise cancellation signals 27R and 27L are added
by the addition means 30R and 30L, and are added to the sounders 23R and 23L via the speaker
driving amplifier 22. By the way, since the output signal 24 of the medical diagnostic control
device 8 is uncorrelated with the noise generation source signal, the output signals of the sound
signal control means 35R, 35 can be controlled independently of the noise. The sound waves
generated from the sound generators 23R and 23L include a sound wave that stimulates or feels
comfortable to the patient 2 in addition to the sound wave that cancels the noise.
[0050]
The method of using a piezoelectric speaker as a sound generator is also included in the present
invention. In this case, even if this speaker is installed in the chamber 1, the influence of
magnetism can be avoided and stable operation can be achieved. It can be done.
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17
[0051]
According to the present invention, in a medical diagnostic apparatus for applying a high
frequency magnetic field to a patient to create a cross-sectional image of a body, a patient lying
in chamber-1 as a means for eliminating noise generated during operation of the apparatus.
Error signal detection means for detecting noise in the vicinity of the ear, noise source signal
detection means for detecting a signal for driving a device generating a magnetic vibration or
high frequency magnetic field as noise source, and a noise source signal Phase / amplitude
control means for inverting the phase of the vibration signal from the detection means and
making the amplitude of the vibration signal proportional to the magnitude of the noise signal
from the error signal detection means to generate a muffling signal; The sound wave from the
sound generation means is transmitted as a sound wave with the same amplitude as the noise
near the ear of the patient and in the opposite phase, so the noise near the ear is effectively
reduced and eliminated. Since the muffling signal is generated based on the noise source signal,
this muffling means can be muffled without causing howling, and since the component is
noncontact with the patient, there is no pressure on the patient and anxiety due to noise You can
eliminate the feeling.
[0052]
Moreover, if the addition function of the music signal and the volume / sound quality control
means of the music are added to the sound generation means in the medical diagnostic
apparatus, the feeling of the patient can be further eased.
[0053]
Further, according to the present invention, another medical diagnostic apparatus is provided
outside the chamber by separating the error signal detection means from the patient's ear as
another means for eliminating noise in the medical diagnostic apparatus. From the above, the
muffling signal is corrected by the transfer coefficient of the sound wave transmission line
between the error signal detection means, and the rest is configured in the same manner as the
medical diagnostic apparatus of the present invention. As the noise generation means, the phase
/ amplitude control means, the drive signal detection means as well as the error signal detection
means are disposed outside the chamber, disturbance of the magnetic field applied to the patient
does not occur. And image quality deterioration can also be prevented.
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