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JP2003070788

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DESCRIPTION JP2003070788
[0001]
BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an
ultrasonic diagnostic apparatus used for medical diagnosis, and in particular to mount an
acoustic coupler at the tip of an ultrasonic probe to obtain a high quality tomographic image An
ultrasonic diagnostic apparatus.
[0002]
2. Description of the Related Art In the medical field, an ultrasonic diagnostic apparatus is used
to observe the inside of a living body. The ultrasonic diagnostic apparatus transmits ultrasonic
waves from the ultrasonic probe to the subject, receives echoes reflected from the subject by the
ultrasonic probe, and creates image data of the subject from the detected signals. To display on
the display device. An ultrasonic probe for transmitting and receiving ultrasonic waves is
configured by arranging a plurality of strip-shaped transducer elements in an array in a onedimensional direction. When an acoustic coupler is attached to the tip of the ultrasonic probe, the
sound velocity of the acoustic coupler may be different from the sound velocity of the living
body. For example, when the acoustic coupler is a water bag or the like, the sound velocity is
approximately 1540 [m / s], which is substantially the same as the sound velocity of the living
body. However, when the material forming the acoustic coupler is rubber or the like, the sound
velocity is approximately 1450 [m / s], which is a value completely different from the sound
velocity of the living body. As described above, when the sound velocity of the material
constituting the acoustic coupler is different from the sound velocity of the living body, the
sound does not go straight but is refracted, the beam is degraded, and the tomographic image is
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degraded accordingly. Therefore, the ultrasonic probe or acoustic coupler is provided with ID
information on ultrasonic characteristics determined by the material and shape thereof (in
particular, ultrasonic propagation characteristics determined by the thickness distribution of the
acoustic coupler in the depth direction and the refractive characteristics of ultrasonic waves).
Japanese Patent Application Laid-Open No. 05-076528 describes that the beam deterioration is
prevented by using the sound velocity information.
[0003]
However, the one disclosed in Japanese Patent Application Laid-Open No. 05-076528 discloses
ID information on ultrasonic characteristics determined in advance by the material and shape of
the coupler as a probe or an acoustic coupler. Since it is configured to be held, the thickness,
shape, or temperature of the coupler itself is changed by pressing the coupler against the subject,
etc., and it has been difficult to cope with various changes in the ultrasonic characteristics. That
is, even if the ID information on the ultrasonic characteristics of the coupler is known in advance,
if the thickness and shape change variously, beam deterioration can not be prevented using it,
and the temperature of the coupler itself changes. The speed of sound also slightly changes, and
there is a problem that it becomes difficult to cope with it.
[0004]
SUMMARY OF THE INVENTION It is an object of the present invention to provide an ultrasonic
diagnostic apparatus capable of preventing beam deterioration and improving image quality in
response to various changes in thickness, shape, etc. of an acoustic coupler.
[0005]
According to a first aspect of the present invention, there is provided an ultrasonic diagnostic
apparatus comprising: probe means for transmitting and receiving ultrasonic waves; acoustic
coupler means mounted on the probe means; An instruction means for variably outputting data
relating to the characteristics of the acoustic coupler means according to the operation of the
operator, and an output of deterioration of the beam due to a difference between the sound
velocity of the object and the sound velocity of the acoustic coupler means from the instruction
means And correction means for correcting by refraction correction based on the data.
This makes it possible to change data relating to the characteristics of the acoustic coupler
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means in order to correct refraction of the beam by the acoustic coupler means, and this data can
be easily manipulated and changed with the manipulator, thereby improving the image quality. It
is intended to By this, for example, when the operator presses the acoustic coupler means against
the object to deform the shape and the thickness changes accordingly, the operator operates the
operating element to refract as much as the thickness change. The correction can be optimized
arbitrarily. In addition, as data, various things, such as thickness of an acoustic coupler means,
sound velocity, a material, a shape, are considered.
[0006]
According to a second aspect of the present invention, in the ultrasonic diagnostic apparatus
according to the first aspect, the data relating to the characteristics of the acoustic coupler means
includes at least thickness data in a beam traveling direction of the acoustic coupler and sound
velocity data of the acoustic coupler. The correction means obtains a delay amount based on the
thickness data and the sound velocity data, and performs the refraction correction based on the
delay amount. This uses the thickness and the speed of sound as data on the characteristics of
the acoustic coupler means. If the thickness and the speed of sound are known, the refraction
correction can be easily performed by setting the delay time of the received signal used in the
digital phasing addition circuit or the like. In addition, the material of an acoustic coupler means,
a shape, etc. can be used as data other than this. Depending on the material, the degree of
deformation due to pressing on the object may differ, or the thickness correction according to
the shape may need to be performed, so these can be applied as data.
[0007]
According to a third aspect of the present invention, an ultrasonic diagnostic apparatus
comprises: probe means for transmitting and receiving ultrasonic waves; acoustic coupler means
mounted on the probe means; and output from the probe means Detection means for detecting
data relating to the characteristics of the acoustic coupler means based on the received wave
signal, and the data detected by the detection means for the deterioration of the beam due to the
difference between the sound velocity of the object and the sound velocity of the acoustic
coupler means. And correction means for correcting by the refraction correction based on The
ultrasonic diagnostic apparatus according to claim 1 optimizes data by operating the
manipulator, which automatically detects data on characteristics of the acoustic coupler means
and uses the detected data. Correction for refraction. Thus, for example, when the operator
presses the acoustic coupler means against the object to deform the shape and accordingly the
thickness changes or the temperature of the acoustic coupler means changes and the speed of
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sound changes, etc. Since changes in thickness and changes in sound velocity are detected by the
detection means, it is possible to automatically optimize refraction correction using the detected
data. In addition to the thickness data and the sound velocity data, the interface with the object,
that is, the shape of the acoustic coupler means may be detected as data, and correction may be
performed based thereon.
[0008]
According to a fourth aspect of the present invention, in the ultrasonic diagnostic apparatus
according to the first aspect, the detection means determines the sound velocity data of the
acoustic coupler means based on a received signal output from the probe means. The boundary
position between the acoustic coupler means and the object is determined based on the sound
velocity measurement means and the received wave signal output from the probe means, and the
distance from the boundary position to the lens surface of the acoustic coupler means is And a
thickness measuring means for obtaining the distance obtained on the basis of the sound velocity
data as the thickness data of the acoustic coupler means, and the correction means for obtaining
a delay amount on the basis of the thickness data and the sound velocity data. The refraction
correction is performed based on the delay amount. The sound velocity data of the acoustic
coupler means is detected by the sound velocity measuring means, the thickness data of the
acoustic coupler means is automatically detected by the thickness measuring means, and the
refraction correction is performed based on these data. is there.
[0009]
According to a fifth aspect of the present invention, in the ultrasonic diagnostic apparatus
according to the third aspect, the detection means calculates a delay time error between adjacent
ones of the received signals output from the probe means. Arithmetic means, storage means for
storing in advance delay time errors of received signals corresponding to a plurality of
propagation sound speeds, delay time errors calculated by the arithmetic means, and delay time
errors stored in the storage means And sound velocity calculating means for determining the
propagation sound velocity by comparing This relates to a specific configuration of the detection
means, and the delay time error between the received signals corresponding to the sound
velocity of the medium used for the acoustic coupler is previously obtained by calculation or the
like, and the acoustic coupler is attached thereto The sound velocity of the acoustic coupler is
measured by comparing the delay time error of adjacent ones of the received signals output from
the calculation means with each other.
04-05-2019
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[0010]
According to a sixth aspect of the present invention, in the fifth aspect, the storage means stores
the delay time errors corresponding to a plurality of channels in a distributed manner, using the
propagation velocity as a parameter. It is. This is a concrete form of the memory contents of the
memory means, and is in the form of distributed data in order to prevent an influence due to an
unexpected noise or the like.
[0011]
DETAILED DESCRIPTION OF THE INVENTION Embodiments of the present invention will be
described below with reference to the attached drawings. FIG. 1 is a block diagram showing a
schematic configuration of an ultrasonic diagnostic apparatus. This ultrasonic diagnostic
apparatus includes an acoustic coupler 10, an ultrasonic probe 11, a transmission circuit 12, a
transmission / reception separation circuit 13, a transducer selection switch 14, a reception
circuit 15, a digital phasing addition circuit 16, and a signal processing circuit 17 The display
unit 18, the acoustic coupler thickness instruction unit 19, the acoustic coupler sound velocity
instruction unit 20, the acoustic coupler correction instruction unit 21, and the CPU 22 are
configured.
[0012]
The acoustic coupler 10 is composed of a water bag, rubber or the like, and is mounted on the
ultrasonic probe 11. The ultrasound probe 11 is configured by arranging a plurality of
ultrasound transducers in an array on an array in a one-dimensional direction. An ultrasonic
transducer group constituting an ultrasonic probe converts a pulse-like electric signal into
mechanical vibration to generate an ultrasonic wave, and mechanical vibration due to reflection
echo from an object is pulse of the electric signal. Convert to The ultrasonic waves generated
from the ultrasonic transducer become an ultrasonic beam focused to a preset focal point
through an acoustic coupler 10 such as a water bag or rubber.
[0013]
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The transmission circuit 12 generates a pulse signal for driving an ultrasonic transducer in order
to generate an ultrasonic wave from the ultrasonic probe 11. At this time, the transmission
circuit 12 gives and outputs a set delay time for each of the ultrasonic transducers to be driven.
The transmission / reception separation circuit 13 passes a pulse signal from the transmission
circuit 12 side to the ultrasonic probe 11 during ultrasonic wave transmission, and receives a
reception signal from the ultrasonic probe 11 side during ultrasonic wave reception. The
transducer selection switch circuit 14 which passes through to the side selects a transducer
group (diameter) contributing to transmission and reception from the ultrasound transducer
group provided on the array in the ultrasound probe 11. The wave receiving circuit 15 amplifies
and digitizes a weak signal which is converted from an ultrasonic wave reflected from the inside
of a subject into an electric signal by an oscillator and output as an echo signal. The digital
phasing / adding circuit 16 forms the ultrasonic receiving beam by aligning and adding the
phases of the digital echo signals output from the wave receiving circuit 15. The signal
processing circuit 17 performs processing for imaging the signal output from the digital phasing
addition circuit 16, and performs detection, logarithmic compression, γ correction, ultrasound
scanning and display on the input signal. It performs scan conversion which performs conversion
with the scan to output an image signal. The display unit 8 displays the image signal output from
the signal processing circuit 17 on the display as a visible image. The acoustic coupler thickness
instruction unit 9 is operated by the operator, and is an operation element for inputting the
thickness of the acoustic coupler. The acoustic coupler sound velocity instruction unit 20 is
operated by the operator, and is an operation element for inputting the sound velocity of the
acoustic coupler. The acoustic coupler correction instruction unit 21 is operated by the operator,
and is an operation element for instructing execution of a beam refraction correction process by
the acoustic coupler. A central processing unit (CPU) 22 centrally controls these components.
[0014]
Next, the operation of the ultrasonic diagnostic apparatus of FIG. 1 will be described. First, the
operator inputs the thickness of the acoustic coupler 10 to the ultrasonic diagnostic apparatus
using the acoustic coupler thickness instruction unit 19 before entering the inspection, and then
the acoustic velocity of the acoustic coupler 10 is transmitted to the acoustic coupler sound
velocity instruction unit 20 After the input using the above, an instruction for correcting the
beam refraction by the acoustic coupler 10 is issued using the acoustic coupler correction
instruction unit 21. Then, the CPU 22 reads the values of the thickness and the speed of sound to
calculate and set the value of the signal delay amount used in the digital phasing addition circuit
16. At this time, the medium model to be calculated is two layers here. That is, the acoustic
coupler is the first layer, and the object is the second layer. The amount of delay in this medium
model is analytically uniquely determined and known.
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[0015]
After performing the above operation, the operator applies the ultrasonic probe 11 mounted with
the acoustic coupler 10 to the body surface of the examination site of the subject, and instructs
the operator to start the ultrasonic scan. Input from (not shown). After this, each circuit which
has received each instruction executes aperture selection of the ultrasound probe 11,
transmission delay data selection, and reception delay data selection, and starts scanning. When
the scan is started, the transmission pulse circuit 1 individually provides the delay time
corresponding to each of the ultrasonic transducers forming the aperture of the probe, and the
transmission / reception separation circuit 13 Then, it is input to the transducer selection switch
circuit (multiplexer circuit) 14. The transducer selection switch circuit 14 sequentially switches
the connection so as to output the input drive pulse to each ultrasonic transducer corresponding
to the aperture. The ultrasonic transducer, that is, the ultrasonic probe 11 is driven by the drive
pulse selectively output from the transducer selection switch circuit 14.
[0016]
The ultrasonic transducers in the ultrasonic probe 11 are respectively selected and driven in the
order of small delay time to transmit ultrasonic waves. The ultrasonic waves transmitted from the
driven ultrasonic transducers into the living body propagate in the living body so that their wave
fronts simultaneously arrive with the same phase to the transmission focus point previously set.
go. Then, when tissues having different acoustic impedance exist in the living body in the process
of propagation, a part of the tissue is reflected at the interface, and returns to the direction of the
ultrasound probe 11 as a reflected wave (echo). The echoes sequentially return in the direction of
the ultrasound probe 11 as the transmitted ultrasound propagates from a shallow site to a deep
site in the living body. These echoes are received by an ultrasonic transducer driven at the time
of transmission or a transducer group which is switched and selected with time from an
ultrasonic transducer group having a smaller diameter to a larger diameter than them and
converted into an electric signal (echo signal) Be done.
[0017]
An echo signal converted into an electric signal by the ultrasonic transducer is transmitted
through the transducer selection switch circuit 14 and the transmission / reception separation
circuit 13 in the receiving circuit 15 for each element line (channel) of the ultrasonic transducer.
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The signals are amplified individually and converted into digital signals for each channel. Then,
the digitized echo signal is taken into the digital phasing / adding circuit 16. The digital phasing /
adding circuit 16 delays the digitized echo signal given each delay time individually
corresponding to each of the ultrasonic transducers for each channel, to a certain point in the
object (on the receiving beam The echoes reflected from each point are summed with the same
phase as appearing at the same time in each channel and added to reduce unnecessary noise in
the receive beam and to perform filtering processing to obtain a necessary band signal. It is
formed as an acoustic beam signal.
[0018]
The results of these delaying, summing and filtering processes form an echo beam received in a
dynamic focusing manner that is conventionally known in the art. The received beam signal is
then output to the signal processing circuit 17. The signal processing circuit 17 subjects the
reception beam signal to image signal processing such as detection, logarithmic compression and
γ correction, and then performs coordinate conversion, and outputs it as an image signal to the
display unit 18. The display unit 18 displays the input image signal on a monitor (not shown).
[0019]
Transmission and reception of ultrasonic waves and signal processing thereof are repeatedly
performed with selective switching of ultrasonic transducers or directional deflection of
ultrasonic beams, and the received signals are sequentially taken into the display section 18, and
each transmission and reception is repeated. The image is formed according to the beam signal
input to the The stored contents in the imaged memory are read out in synchronization with the
scanning cycle of a monitor such as a CRT display. Thereby, the inside of a living body is imaged
and displayed by ultrasonic scanning, imaging is repeatedly performed several times, and these
several images are displayed. Then, if the operator presses the acoustic coupler against the object
or the like and determines that the thickness is different from the initial coupler thickness, the
corrected thickness is input from the acoustic coupler thickness instruction unit 19 and then
corrected in the acoustic coupler correction instruction unit 21 Ask again to do. The subsequent
operation is the same as that described above.
[0020]
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By adopting such an embodiment, it is possible to surely correct the deterioration of the beam
due to the influence of the refraction by the acoustic coupler. According to the configuration of
this embodiment, it is useful because the deterioration of the image quality due to the acoustic
coupler can be corrected, but it is necessary to manually input the thickness and the speed of
sound of the acoustic coupler, and the operation is complicated. Therefore, automatically
measuring and setting the thickness and sound speed of the coupler is useful because the
operation is simplified.
[0021]
FIG. 2 is a block diagram showing a schematic configuration of an ultrasonic diagnostic
apparatus according to a second embodiment of the present invention. In FIG. 2, the same
components as those in FIG. 1 are denoted by the same reference numerals, and the description
thereof will be omitted. 2 differs from that of the embodiment of FIG. 1 in that the acoustic
coupler thickness instruction unit 19 and the acoustic coupler sound velocity instruction unit 20
are changed to the acoustic coupler thickness measurement unit 23 and the acoustic coupler
sound velocity measurement unit 34, It is the point that thickness and the speed of sound were
measured automatically.
[0022]
Next, the operation of the portion modified in the second embodiment will be described with
reference to FIG. The operator first uses the acoustic coupler correction instruction unit 21 to
issue an instruction to perform coupler correction. At this time, since the thickness of the coupler
and the speed of sound are unknown, the ultrasonic scan is performed once as described above.
At this time, a strong ultrasonic signal can be received from the difference in acoustic impedance
at the interface between the water bag as the acoustic coupler and the medium such as the object
or air. Since it is known that the shallowest one of the large-amplitude signals among the
received signals indicates the interface, the position of such a signal is detected by the acoustic
coupler thickness measurement unit 23. At this time, the position of the signal detected from the
reception signal can be recognized only as time T when the ultrasonic signal reciprocates the
acoustic coupler. Therefore, it is necessary to convert this time T into the thickness L of the
coupler. The thickness L can be obtained by the following equation L = T × V / 2 using the
sound velocity V from the acoustic coupler sound velocity measurement unit 34. The position of
the interface found in this way can be used as it is as the thickness of the acoustic coupler and
can be used instead of the output value of the acoustic coupler thickness indication unit 19
which is a component of the embodiment of FIG. The acoustic coupler thickness instruction unit
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19 of 1 can be replaced with the acoustic coupler thickness measurement unit 23 of FIG. Also, if
a reception signal indicating the position of the interface is output to the display unit 18, it is
displayed as an interface on a bright stripe. This means that it is possible to detect the boundary
position between the acoustic coupler and the medium by examining the signal at any of the
stages from the reception signal to the conversion to the image signal. Therefore, the signal
capable of detecting the interface position can be easily output from either the output signal of
the digital phasing addition circuit 16 or the output signal of the signal processing circuit 17.
[0023]
Next, a method of automatically obtaining the sound velocity of the acoustic coupler using the
acoustic coupler sound velocity measuring unit 24 will be described. The details of this method
are described in Japanese Patent Application No. 2000-66764 filed earlier, and therefore will be
briefly described using FIG. 3 and FIG. FIG. 3 is a diagram showing the detailed configuration of
the digital phasing addition circuit 16 and the acoustic coupler thickness measurement unit 23 of
FIG. 2, and FIG. 4 shows the details of the digital delay unit 161 and the delay error calculation
unit 32 of FIG. FIG.
[0024]
The digital phasing / adding circuit 16 comprises a digital delay section 161 and an adding
circuit 162. The digital delay unit 161 delays and controls the digital echo signal output from the
wave receiving circuit 15. The addition circuit 162 adds the echo signals output from the digital
delay unit 161 to form an ultrasonic reception beam signal.
[0025]
The acoustic coupler thickness measurement unit 23 includes a digital delay data generation unit
231, a delay time error storage unit 232 corresponding to sound velocity, a delay error
calculation unit 233, a delay time comparison unit 234, a sound velocity data storage unit 235,
and a medium sound velocity selection unit 236. It consists of The digital delay data generation
unit 231 supplies delay data to the digital delay unit 161. The sound speed corresponding delay
time recording unit 232 is formed of, for example, a ROM, in which a plurality of delay time
groups corresponding to a plurality of medium sound speeds are stored in advance. The delay
error calculation unit 233 calculates and obtains delay errors from the plurality of echo signals
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output under delay control by the digital delay unit 161. The details of the delay error calculation
unit 233 will be described later. The delay time comparison unit 234 collates the delay time
error data obtained by the delay error calculation unit 233 with the stored value of the sound
velocity corresponding delay time recording unit 232, and corresponds to the sound velocity
closest to the sound velocity of the object to be examined. Output delay time data. The sound
velocity data recording unit 235 records what kind of medium sound velocity the respective
delay time groups stored in the sound velocity corresponding delay time recording unit 232
correspond to. The medium sound velocity selecting unit 236 selects the medium sound velocity
from the recording location of the delay time output from the delay time comparing unit 133
with reference to the delay time recording unit.
[0026]
As shown in FIG. 4, among the outputs of the digital delay circuits 40-1 to 40-M, the delay error
calculation unit 233 inputs the outputs of two adjacent channels, and delays the delay time error
thereof. Based on the output data of the (M-1) delay time error detection circuits 41-1 to 41- (M1) and the delay time error detection circuits 41-1 to 41- (M-1). And a delay time error
distribution data forming circuit 42 which forms distribution data. The delay time error detection
circuits 41-1 to 41- (M-1) detect delay errors by the correlation method disclosed in Japanese
Patent Laid-Open No. 4-252576.
[0027]
The sound speed corresponding delay time storage unit 232 is a delay when the sound speed is
changed by a predetermined sound speed difference with respect to the reference sound speed
on the basis of the delay time error in each channel serving as a reference sound speed (for
example, average sound speed). The time error data is calculated in advance and stored in the
form of a table. FIG. 5 is a graph for visualizing the state of the delay time error data at this time.
In FIG. 5, the horizontal axis represents channel numbers 1 to M, the vertical axis represents
delay time errors, and a plurality of lines in the graph represent the relationship between
channels with sound speed as a parameter and delay time errors. In addition, what was shown in
FIG. 5 makes linear scan an example.
[0028]
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In FIG. 5, the delay time error is made to be a straight line with a constant value (zero) in each
channel at the reference sound velocity V0. This is because the present invention adopts a
method of performing a test shot assuming the reference sound velocity V0 and determining how
much the error of the delay time is. Referring to FIG. 5, in the case of the sound velocity faster
than the reference sound velocity V0, the distribution of the delay time error has a convex shape
downward about the ultrasonic transducer (M / 2) near the center, and has a sound velocity
slower than the reference sound velocity V0. In this case, the distribution of delay time errors is
convex upward in line symmetry with the previous case. As described above, making the contents
stored in the sound velocity corresponding delay time storage unit 332 into data corresponding
to the reference sound velocity and the difference thereof also contributes to reducing the
storage capacity of the storage medium.
[0029]
Next, the principle and operation of estimating the sound velocity of the ultrasonic wave
propagation medium will be described. First, assuming that the ultrasonic wave propagation
velocity of the medium is the average sound velocity of the living body in the digital delay unit
161, transmission delay data based on the average sound velocity is set in the transmission
circuit 12, and trial ultrasonic scanning is performed. The digital delay data generation unit 231
supplies the reception delay data (Dr) corresponding to the average sound velocity to the digital
delay unit 161. From the digital delay unit 161, echo signals of respective channels forming one
reception beam are respectively output to the addition circuit 162 and the delay error calculation
unit 233. The delay error calculation unit 233 detects echo signals of adjacent channels, for
example, 1CH and 2CH, 2CH and 3CH... (M-1) CH and MCH adjacent delay channels, from delay
time error detection circuit 41-. The delay time error (ΔDn) between each channel is calculated
using 1 to 41- (M−1), and a delay time error data group consisting of ΔD1, ΔD2. The purpose
of obtaining delay time error data as distributed data in this way is to prevent errors due to data
such as unexpected noise. Note that the calculation of the delay error by the delay error
calculation unit 233 may be performed on the reception beam over the entire scanning region
when scanning the inside of the living body by changing the position or direction of the
ultrasonic beam by the probe. In particular, a region of interest in which an organ to be examined
is present may be defined and performed only for the reception beam of that region.
[0030]
Next, the ultrasonic wave propagation velocity in the living body is determined based on the
distribution data of the delay time error data. In the sound speed corresponding delay time
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recording unit 232, delay time data corresponding to a plurality of possible sound speeds are
stored using the sound speed as a parameter. The stored contents of the sound velocity
corresponding delay time recording unit 232 are also stored in correspondence with the sound
velocity as distribution data of delay times corresponding to the respective channels. Then, the
stored contents of the delay error calculation unit 233 and the sound velocity corresponding
delay time storage unit 232 are compared by the delay time comparison unit 234. Specifically, it
compares and selects which of the stored contents of the sound speed corresponding delay time
storage unit 232 the distribution of the output data of the delay error calculation unit 233
matches well.
[0031]
At this time, since the delay time distribution recorded in the sound speed corresponding delay
time recording unit 232 which is the comparison object is a delay time distribution for discrete
sound speed values, the value of the speed of sound assumed is not so large and coarse. In some
cases, the delay time distribution, which is often recorded in the sound velocity corresponding
delay time storage unit 232, and the distribution of output data of the delay error calculation unit
233 may become an intermediate value without matching. Assuming such a case, a value close to
the output of the delay error calculation unit 233 among the delay time error data recorded in
the sound speed corresponding delay time storage unit 232 at the subsequent stage of the
comparison unit inside the delay time comparison unit 234 Are selected, and an arithmetic
circuit capable of performing a interpolation operation by interpolation or extrapolation using
them is added, and the operation result is used to determine the velocity of sound. If the sound
velocity of the medium is assumed to be sufficiently fine and stored in the sound velocity
corresponding delay time storage unit 232, such interpolation processing is not necessary. In
order to simplify the comparison work in the delay time comparison unit 234, the delay time
distributions for the input of a plurality of ultrasonic signals can be approximated by a secondorder concave surface, so that the amount of information to be handled can be reduced by using
it. It is useful. Furthermore, it is useful to obtain the step difference of the delay time distribution
and to apply a first-order straight line to the difference delay time sequence, since the amount of
information to be handled is further reduced.
[0032]
Next, the medium sound velocity selection unit 236 receives delay time error data that matches
the output of the delay error calculation unit 233 output from the delay time comparison unit
234, and the sound velocity value corresponding to the delay time distribution is It is determined
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by referring to the data storage unit 235. In order to improve the accuracy of the determined
sound velocity, it is necessary for the received ultrasonic signal to have a sufficient strength, but
the harmonics generated by the fundamental and the ultrasonic medium which are the same
frequency as the transmission frequency In an apparatus configuration that deals with signals,
the harmonics are generally weaker than the intensity of the fundamental wave. Therefore, in
order to accurately estimate the sound velocity even for the harmonics, it is useful to compensate
the signal attenuation by setting the amplification factor to be larger for the harmonic than the
signal amplification factor for the fundamental wave. Similarly, it is effective to amplify the signal
by a known compensation value if it is known that the ultrasonic medium has different degrees
of attenuation depending on the transmission frequency and the pass path length. The sound
velocity data selected by the medium sound velocity selecting unit 236 is fed back to the CPU 22
and is used to generate delay data of the digital delay unit 161 in an ultrasonic scan for an
inspection to be performed next time, and the display unit via the CPU 22 , And is displayed
numerically as V = 1,500 on the display screen of the display unit 18.
[0033]
The sound velocity value thus obtained can be used in place of the value output from the acoustic
coupler sound velocity instruction unit 20 described with reference to FIG. 1, so the acoustic
coupler sound velocity instruction unit 20 can be used as an acoustic coupler The sound velocity
measurement unit 24 can be replaced. Further, the sound velocity value of the determined
coupler may be notified to the acoustic coupler thickness measurement unit 23 via the CPU 22
or may be notified directly from the medium sound velocity selection unit 236. Since the
thickness and the velocity of sound of the coupler are automatically determined by this
operation, the same operation as described above is performed. With the above-described
configuration, it is possible to correct the ultrasonic beam from being refracted and deteriorated
due to the difference in the sound velocity between the acoustic coupler and the living body, and
to maintain the image quality of the tomogram with high quality.
[0034]
Although the embodiments described above all show examples of the electronic linear scanning
type ultrasonic probe, the present invention is not limited to this, and an electronic convex
scanning type ultrasonic probe, an electronic sector scanning, etc. The present invention can be
applied to all scanning type ultrasonic probes such as type ultrasonic probes. In the above
embodiment, beam degradation due to the acoustic coupler can be corrected by inputting the
thickness and sound velocity of the coupler, and by automatically measuring the thickness of the
04-05-2019
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coupler, the operation can be simplified and the sound velocity of the coupler can be
automatically measured. Therefore, the image quality can be improved by a simpler operation.
Although the case of thickness data and sound velocity data has been described as data relating
to the characteristics of the acoustic coupler in the above-described embodiment, various
materials such as the material and shape of the acoustic coupler can be used besides this. For
example, the present invention can be applied to taking into consideration the degree of
deformation due to pressing on a subject depending on the material, or performing thickness
correction according to the shape.
[0035]
According to the present invention, even when the thickness, shape, temperature or the like of
the acoustic coupler changes variously, the beam deterioration can be prevented and the image
quality can be improved accordingly.
[0036]
Brief description of the drawings
[0037]
Fig. 1 is a block diagram showing a configuration in which the thickness of the coupler and the
speed of sound are instructed by the instruction in the correction of the influence of refraction by
the acoustic coupler of the ultrasonic diagnostic apparatus of the present invention.
[0038]
Fig. 2 is a block diagram showing a configuration for automatically determining and using the
thickness of the coupler and the value of the velocity of sound in the correction of the influence
of refraction by the acoustic coupler of the ultrasonic diagnostic apparatus of the present
invention.
[0039]
FIG. 3 is a diagram showing a detailed configuration of the digital phasing / adding circuit and
the acoustic coupler thickness measurement unit of FIG. 2
[0040]
FIG. 4 is a view showing details of the digital delay unit and the delay error calculation unit of
FIG. 3;
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[0041]
Diagram for visualizing the memory contents of the sound speed corresponding delay time error
storage unit of FIG.
[0042]
Explanation of sign
[0043]
DESCRIPTION OF SYMBOLS 10 ... Acoustic coupler, 11 ... Ultrasonic probe, 12 ... Transmission
circuit, 13 ... Transmission / reception isolation circuit, 14 ... Transducer selection switch, 15 ...
Reception circuit, 16 ... Digital phasing addition circuit, 17 ... Signal processing Circuit 18 Display
portion 19 Acoustic coupler thickness instruction portion 20 Acoustic coupler sound velocity
instruction portion 21 Acoustic coupler correction instruction portion 22 CPU 23 Acoustic
coupler thickness measurement portion 24 Acoustic coupler sound velocity measurement
portion , 161: digital operation unit, 162: addition circuit, 231: digital delay data generation unit,
232: sound velocity corresponding delay time error storage unit, 233: delay error operation unit,
234: delay time comparison unit, 235: sound velocity data storage unit 236: Medium sound
velocity selection unit 40-1 to 40-M Digital delay circuit 41-1 to 41- (M-1) Delay time error
detection circuit 42: Delay time error distribution data formation circuit
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