Abstrict An ultrasonic continuous wave doppler blood flow-meter deflects
an ultrasonic continuous wave to an arbitrary angle and transmits
it into an organism, thereby measuring a blood flow speed of the
organism. Two continuous sine wave signals of different phases and
a plurality of sets of pairs of coefficients are generated. One
of each of the pairs of coefficients is multiplied to one of the
two sine wave signals. The other one of each of the pairs of coefficients
is multiplied to the other one of the two sine wave coefficients.
After that, two sine wave signals after the multiplication are added,
so that a plurality of synthesis sine wave signals are generated.
When a plurality of micro vibrators are driven by the plurality
of synthesis sine wave signals, the ultrasonic continuous wave is
deflected to an arbitrary angle and is transmitted into the organism.
Claims What is claimed is:
1. An ultrasonic continuous wave doppler blood flow-meter for deflecting
an ultrasonic continuous wave to an arbitrary angle and transmitting
said wave into an organism, thereby measuring a blood flow speed
of said organism, comprising:
sine wave signal generating means for generating two continuous
sine wave signals of different phases;
coefficient generating means for generating a plurality of sets
of pairs of coefficients;
synthesis sine wave signal generating means for generating a plurality
of synthesis sine wave signals by multiplying one of each of said
pairs of coefficients to one of said two sine wave signals, for
multiplying the other one of each of said pairs of coefficients
to the other one of said two sine wave signals, and for adding said
two sine wave signals after the multiplication; and
a plurality of micro vibrators driven by said plurality of synthesis
sine wave signals, each of said micro vibrators deflecting said
ultrasonic continuous wave to an arbitrary angle and transmitting
said wave into said organism.
2. A meter according to claim 1 wherein said sine wave signal
generating means comprises a first sine wave signal generating unit
for generating said one of said two sine wave signals and a second
sine wave signal generating unit for generating said other one of
said two sine wave signals, said other one of said two sine wave
signals having a phase which is different from a phase of said one
of said two sine wave signals by 90.degree..
3. A meter according to claim 1 wherein one of said pair of coefficients
has a value which is calculated by cos.theta. and the other one
of said pair of coefficients has a value which is calculated by
sin.theta..
4. A meter according to claim 1 further comprising:
a plurality of receiving micro vibrators for respectively receiving
echo signals as reflection waves from the inside of said organism
of the ultrasonic continuous waves transmitted from said plurality
of micro vibrators;
delay adding means for respectively delaying said plurality of
received echo signals in accordance with their deflection angles
and converging states and for adding said plurality of delayed echo
signals;
detecting means for detecting an output signal of said delay adding
means to detect a doppler signal; and
frequency analyzing means for frequency analyzing said doppler
signal.
5. An ultrasonic continuous wave doppler blood flow-meter for deflecting
an ultrasonic continuous wave to an arbitrary angle and transmitting
said wave into an organism, thereby measuring a blood flow speed
in said organism, comprising:
sine wave signal generating means for generating two continuous
sine wave signals of different phases;
synthesis sine wave signal generating means, having a plurality
of sets of pairs of fixed coefficients, for multiplying one of each
of said pairs of fixed coefficients to one of said two sine wave
signals, for multiplying the other one of each of said pairs of
fixed coefficients to the other one of said two sine wave signals,
and for adding said two sine wave signals after the multiplication
to generate a plurality of synthesis sine wave signals;
switching means having a plurality of switches each for selecting
any one of said plurality of synthesis sine wave signals in accordance
with a deflection and a converging state of said ultrasonic continuous
wave to be transmitted; and
a plurality of micro vibrators driven by said plurality of synthesis
sine wave signals selected by said switching means, each of said
micro vibrators deflecting said ultrasonic continuous wave to an
arbitrary angle and transmitting said wave into said organism.
6. A meter according to claim 5 wherein said sine wave signal
generating means comprises a first sine wave signal generating unit
for generating said one of said two sine wave signals and a second
sine wave signal generating unit for generating said other one of
said two sine wave signals, said other one of said two one wave
signals having a phase which is different from a phase of said one
of said two sine wave signals by 90.degree..
7. A meter according to claim 6 wherein said switching means comprises:
delay time calculating means for calculating a delay time according
to the deflection and the converging state of said ultrasonic continuous
wave to be transmitted; and
delay time-phase converting means for converting said calculated
delay time into a phase of said ultrasonic continuous wave to be
transmitted.
8. A meter according to claim 5 further comprising:
a plurality of micro receiving vibrators for respectively receiving
echo signals as reflection waves from the inside of said organism
of the ultrasonic continuous waves transmitted from said plurality
of micro vibrators;
delay adding means for respectively delaying said plurality of
received echo signals in accordance with their deflection angles
and converging states and for adding said plurality of delayed echo
signals;
detecting means for detecting an output signal of said delay adding
means to detect a doppler signal; and
frequency analyzing means for frequency analyzing said doppler
signal.
9. A meter according to claim 4 wherein said detecting means comprises
an orthogonal detector for orthogonally detecting the output signal
of the delay adding means after completion of adding of said plurality
of delayed echo signals.
10. A meter according to claim 4 further comprising a display
unit for displaying an analysis result of said frequency analyzing
means.
11. A meter according to claim 4 wherein said switch means comprises
a matrix switch which includes said plurality of switches.
Description BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to an ultrasonic continuous wave doppler
blood flow-meter for deflecting an ultrasonic continuous wave to
an arbitrary angle and transmitting it into an organism, thereby
measuring a blood flow speed of the organism.
2. Description of the Related Art
An ultrasonic continuous wave doppler blood flow-meter measures
a blood flow speed or the like of an organism by using an ultrasonic
continuous wave. A main stream of a blood flow-meter of a doppler
type using an ultrasonic continuous wave is called a steerable continuous
wave blood flow-meter. By using an array probe comprising a plurality
of micro vibrators, ultrasonic continuous waves are transmitted
from a micro vibrator group for transmission and echo signals are
received by a micro vibrator group for reception. According to such
an ultrasonic continuous wave blood flow-meter, by giving a delay
time to a transmission/reception signal, not only the transmission/reception
signal can be deflected in an arbitrary direction but also it can
be commonly used in both of a B mode and a pulse doppler mode by
the same group. Therefore, an observing portion can be identified
to a certain degree.
Hitherto, as such an ultrasonic continuous wave doppler blood flow-meter,
a flow-meter disclosed in JP-A-63-315037 is known. As shown in FIG.
1 the ultrasonic continuous wave doppler blood flow-meter has:
an ultrasonic probe 21 constructed by a plurality of micro vibrators
21a-21h for transmission for transmitting ultrasonic continuous
waves to an object to be examined (organism) and a plurality of
micro vibrators 21i-21p for reception for receiving ultrasonic continuous
waves (echo signals) reflected from the object to be examined; reference
signal generating means 22 for generating a clock signal of a predetermined
frequency; a frequency divider 24 for frequency dividing the clock
signal from the reference signal generating means 22; a 90.degree.
phase shifter 23 for delaying the clock signal, by 90.degree., which
was frequency divided by the frequency divider 24; delay means 25
for generating a plurality of continuous wave transmission signals
each having a delay time according to a deflection angle and a convergence
distance of the ultrasonic continuous wave to be transmitted by
using the clock signal from the reference signal generating means
22; and driving means 27 for amplifying the plurality of continuous
wave transmission signals from the delay means 25 to drive the micro
vibrators 21a-21h for transmission of the ultrasonic probe 21 respectively.
The ultrasonic continuous wave doppler blood flow-meter further
has: delay adding means 28 for respectively delaying the plurality
of echo signals received by the micro vibrators 21i-21p for reception
of the ultrasonic probe 21 in accordance with their deflection angles
and convergence states and, thereafter, adding the plurality of
delayed echo signals; an orthogonal detector 29 for detecting a
doppler signal from an echo signal after completion of the addition
from the delay adding means 28 by using the clock signal and an
output signal of the 90.degree. phase shifter 23; a frequency analyzer
30 for performing a frequency analysis with respect to an output
signal of the orthogonal detector 29; and display means 31 for displaying
an analysis result of the frequency analyzer 30.
According to the ultrasonic continuous wave doppler blood flow-meter,
the clock signal generated by the reference signal generating means
22 is inputted to the delay means 25. By using the clock signal,
the delay means 25 generates a plurality of continuous wave transmission
signals each having the delay time according to the deflection angle
and convergence distance of the ultrasonic continuous wave to be
transmitted. Namely, in the delay means 25 the continuous waves
are accurately generated by digital circuits such as counter, shift
register, and the like. After the plurality of continuous wave transmission
signals to be generated from the delay means 25 are amplified by
the driving means 27 they are inputted to the micro vibrators 21a-21h
for transmission of the ultrasonic probe 21. Thus, the micro vibrators
21a-21h for transmission are driven and the ultrasonic continuous
waves are transmitted.
The echo signals which are respectively received by the micro vibrators
21i-21p for reception of the ultrasonic probe 21 are respectively
delayed in accordance with their deflection angles and convergence
states and, after that, they are added by the delay adding means
28. The echo signal after completion of the addition that is outputted
from the delay adding means 28 is orthogonal-detected by the orthogonal
detector 29 so that the doppler signal is detected. The detected
doppler signal is frequency analyzed by the frequency analyzer 30
and the analysis result of the frequency analyzer 30 is displayed
by the display means 31.
In such an ultrasonic continuous wave doppler blood flow-meter,
a dynamic range of a reception system is important. As one of factors
which exert an influence on the dynamic range of the reception system,
a factor such that the continuous wave transmission signals to drive
the ultrasonic probe 21 for the purpose of transmission are directly
mixed into the reception system can be mentioned. In the foregoing
ultrasonic continuous wave doppler blood flow-meter, however, since
a rectangular wave signal (continuous wave transmission signal generated
by using the clock signal as it is) is used as a continuous wave
transmission signal, when a harmonic component of the rectangular
wave signal is mixed into the reception system, the dynamic range
of the reception system deteriorates. There is, consequently, a
problem such that when a blood flow around a strong echo is measured,
a doppler signal cannot intermittently be obtained.
SUMMARY OF THE INVENTION
It is an object of the invention to provide an ultrasonic continuous
wave doppler blood flow-meter in which a deflecting precision of
an ultrasonic continuous wave is high and a dynamic range is wide.
According to a first ultrasonic continuous wave doppler blood flow-meter
of the invention, there is provided an ultrasonic continuous wave
doppler blood flow-meter for deflecting an ultrasonic continuous
wave to an arbitrary angle and transmitting it into an organism,
thereby measuring a blood flow speed of the organism, comprising:
sine wave signal generating means for generating two continuous
sine wave signals of different phases;
coefficient generating means for generating a plurality of sets
of pairs of coefficients;
synthesis sine wave signal generating means for multiplying one
of each of the pairs of coefficients to one of the two sine wave
signals, multiplying the other one of each of the pairs of coefficients
to the other one of the two sine wave signals, and for adding the
two sine wave signals after the multiplication, thereby generating
a plurality of synthesis sine wave signals; and
a plurality of micro vibrators driven by the plurality of synthesis
sine wave signals, each of the micro vibrators deflecting the ultrasonic
continuous wave to an arbitrary angle and transmitting the wave
into the organism.
According to a second ultrasonic continuous wave doppler blood
flow-meter of the invention, there is provided an ultrasonic continuous
wave doppler blood flow-meter for deflecting an ultrasonic continuous
wave to an arbitrary angle, transmitting it into an organism, thereby
measuring a blood flow speed of the organism, comprising:
sine wave signal generating means for generating two continuous
sine wave signals of different phases;
synthesis sine wave signal generating means, having a plurality
of sets of pairs of fixed coefficients, for multiplying one of each
of the pairs of fixed coefficients to one of the two sine wave signals,
multiplying the other one of each of the pairs of fixed coefficients
to the other one of the two sine wave signals, and for adding the
two sine wave signals after the multiplication, thereby generating
a plurality of synthesis sine wave signals;
switching means having a plurality of switches each for selecting
any one of the plurality of synthesis sine wave signals in accordance
with a deflection and a converging state of the ultrasonic continuous
wave to be transmitted; and
a plurality of micro vibrators driven by the plurality of synthesis
sine wave signals selected by the switching means, each of the micro
vibrators deflecting the ultrasonic continuous wave to an arbitrary
angle and transmitting the wave into the organism.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a block diagram showing a construction of an example
of a conventional ultrasonic continuous wave doppler blood flow-meter;
FIG. 2 is a block diagram showing a construction of an ultrasonic
continuous wave doppler blood flow-meter according to the first
embodiment of the invention;
FIGS. 3A and 3B are diagrams for explaining a construction of an
adder shown in FIG. 1;
FIG. 4 is a block diagram showing a construction of an ultrasonic
continuous wave doppler blood flow-meter according to the second
embodiment of the invention;
FIGS. 5A and 5B are diagrams for explaining a construction of an
adder shown in FIG. 4; and
FIG. 6 is a block diagram showing a construction of a data generating
circuit shown in FIG. 4.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
As shown in FIG. 2 as a transmission system, an ultrasonic continuous
wave doppler blood flow-meter according to the first embodiment
of the invention has: an ultrasonic probe 1 constructed by a plurality
of transmitting micro vibrators 1a-1h for transmitting ultrasonic
continuous waves to an object to be examined (organism) and a plurality
of micro receiving vibrators 1i-1p for receiving ultrasonic continuous
waves (echo signals) reflected from the object to be examined; a
reference signal generator 2 for generating a clock signal of a
predetermined frequency; a 90.degree. phase shifter 3 for delaying
the clock signal from the reference signal generator 2 by 90.degree.;
a first sine wave converter 4a for converting the clock signal from
the reference signal generator 2 into a first sine wave signal X;
a second sine wave converter 4b for converting the clock signal
which is delayed by the 90.degree. phase shifter 3 by 90.degree.
into a second sine wave signal Y; a weight coefficient generator
6 for generating a plurality of first coefficients k.sub.xo -k.sub.xn
for the first sine wave signal X and a plurality of second coefficients
k.sub.y0 -k.sub.yn for the second sine wave signal Y; and a multiplication
adder group 5 comprising a plurality of multiplication adders.
As shown in FIGS. 3A and 3B, each multiplication adder constructing
the multiplication adder group 5 has: a first multiplier 5bn for
performing a multiplication of the first coefficient k.sub.xn and
the first sine wave signal X; a second multiplier 5cn for performing
a multiplication of the second coefficient k.sub.yn and the second
sine wave signal Y; and an adder 5an for adding an output signal
of the first multiplier 5bn and an output signal of the second multiplier
5cn to output a synthesis sine wave signal T.sub.n. Each of the
first coefficient k.sub.xn and the second coefficient k.sub.yn is
generated by the weight coefficient generator 6 in accordance with
the following equations.
Therefore, since the synthesis sine wave signal T.sub.n which is
outputted from the adder 5an has a phase as shown in FIG. 3B, in
case of changing the phase of the synthesis sine wave signal T.sub.n,
it is sufficient to change at least one of the first coefficient
k.sub.xn and the second coefficient k.sub.yn.
As shown in FIG. 2 as a transmission system, the ultrasonic continuous
wave doppler blood flow-meter according to the embodiment further
has a drive unit 7 comprising a plurality of drive amplifiers for
respectively amplifying a plurality of synthesis sine wave signals
T.sub.0 -T.sub.n from the multiplication adder group 5 and respectively
driving the micro vibrators 1a-1h for transmission.
As a reception system, the ultrasonic continuous wave doppler blood
flow-meter of the embodiment has: a delay adder 8 for respectively
delaying a plurality of echo signals received by the micro vibrators
1i-1p for reception of the ultrasonic probe 1 in accordance with
their deflection angles and converging states and, after that, adding
the plurality of delayed echo signals; an orthogonal detector 9
for orthogonal-detecting the echo signal after completion of the
addition from the delay adder 8 by the clock signal from the reference
signal generator 2 and the clock signal, which is delayed by 90.degree.
and is generated from the 90.degree. phase shifter 3 to detect
a doppler signal; a frequency analyzer 10 for frequency analyzing
the doppler signal from the orthogonal detector 9; and a display
unit 11 for displaying an analysis result of the frequency analyzer
10.
The operation of the ultrasonic continuous wave doppler blood flow-meter
of the embodiment will now be described.
The reference signal generator 2 is constructed by a generator
such as a quartz oscillator or the like for generating a clock signal
of a predetermined frequency of a high precision. Two clock signals
of rectangular waves whose phases are different from each other
by 90.degree. are generated by the reference signal generator 2
and 90.degree. phase shifter 3. In the first and second sine wave
converters 4a, 4b, harmonic components of the clock signal from
the reference signal generator 2 and the clock signal from the 90.degree.
phase shifter 3 are removed by filters, respectively. Thus, the
above two clock signals become the first and second sine wave signals
X, Y whose phases are different from each other by 90.degree..
In the adder group 5 the processes as mentioned above are executed
by using the first and second sine wave signals X, Y and the first
and second coefficients k.sub.x0 -k.sub.xn, k.sub.y0 -k.sub.yn,
so that a plurality of synthesis sine wave signals T.sub.0 -T.sub.n
are generated. The plurality of synthesis sine wave signals T.sub.0
-T.sub.n are generated so as to have different phases, respectively.
After the plurality of synthesis sine wave signals T.sub.0 -T.sub.n
are amplified by the drive unit 7 they are supplied to the micro
vibrators 1a-1h for transmission of the ultrasonic probe 1 respectively.
Thus, the micro vibrators 1a-1h for transmission are driven and
the ultrasonic continuous waves are irradiated toward the object
to be examined.
The echo signals from the object to be examined which are respectively
received by the micro vibrators 1i-1p for reception of the ultrasonic
probe 1 are respectively delayed in accordance with their deflection
angles and converging states and, after that, they are added by
the delay adder 8. The echo signal after completion of the addition
which is outputted from the delay adder 8 is orthogonal-detected
by the orthogonal detector 9 so that a doppler signal is detected.
The detected doppler signal is frequency analyzed by the frequency
analyzer 10 and an analysis result of the frequency analyzer 10
is displayed by the display unit 11.
As mentioned above, in the ultrasonic continuous wave doppler blood
flow-meter of this embodiment, since the ultrasonic continuous wave
is generated by using the sine wave signal from which the harmonic
component of the clock signal generated from the reference signal
generator 2 was removed, the harmonic component is not mixed from
the transmission system into the reception system. A deterioration
in dynamic range of the reception system can be prevented.
As shown in FIG. 4 an ultrasonic continuous wave doppler blood
flow-meter according to the second embodiment of the invention differs
from the ultrasonic continuous wave doppler blood flow-meter according
to the first embodiment of the invention shown in FIG. 2 with respect
to the following points.
(a) Each of (M+1) adders constructing an adder group 55 applies
fixed weights to the first and second sine wave signals X, Y from
the first and second sine wave converters 4a, 4b and, after that,
adds them. Thus, (M+1) synthesis sine wave signals .phi..sub.0 -.phi..sub.M
whose phases are deviated at regular intervals are generated.
(b) A matrix switch 12 for converting the (M+1) synthesis sine
wave signals .phi..sub.0 -.phi..sub.M from the adder group 55 into
a plurality of synthesis sine wave signals T.sub.0 -T.sub.n is provided
between the adder group 55 and the drive unit 7.
(c) A data generating unit 13 for generating connection data to
decide a connecting state of the matrix switch 12 is provided.
Namely, as shown in FIG. 5A, an m-th adder 55m constructing the
adder group 55 has: a first multiplier 55bm for performing a multiplication
of the first sine wave signal X from the first sine wave converter
4a and a first fixed coefficient K.sub.xm ; a second multiplier
55cm for executing a multiplication of the second sine wave signal
Y from the second sine wave converter 4b and a second fixed coefficient
K.sub.ym ; and an adder 55am for adding an output signal of the
first multiplier 55bm and an output signal of the second multiplier
55cm. An m-th synthesis sine wave signal .phi..sub.m is generated
from the adder 55am. The first fixed coefficient K.sub.xm and the
second fixed coefficient K.sub.ym are determined by the following
equations.
where,
As mentioned above, it is sufficient that the first and second
multipliers 55bm, 55cm constructing the adder 55m execute multiplications
of the fixed coefficients and the sine wave signals. There is no
need to have an analogwise multiplying function, and it is sufficient
to use a fixed amplifier whose gain is equal to the fixed coefficient.
The operation of the ultrasonic continuous wave doppler blood flow-meter
of the embodiment will now be described.
The reference signal generator 2 is constructed by a generator
such as a quartz oscillator or the like for generating a clock signal
of a predetermined frequency of a high precision. Two clock signals
of rectangular waves whose phases are different from each other
by 90.degree. are generated from the reference signal generator
2 and the 90.degree. phase shifter 3. In the first and second sine
wave converters 4a, 4b, harmonic components of the clock signal
from the reference signal generator 2 and the clock signal from
the 90.degree. phase shifter 3 are respectively removed by filters.
Thus, the two clock signals become the first and second sine wave
signals X, Y whose phases are different from each other by 90.degree..
In the adder group 55 since the processes as mentioned above are
executed by using the first and second sine wave signals X, y and
the first and second fixed coefficients K.sub.x0 -K.sub.xM, k.sub.y0
-k.sub.yM, (M+1) synthesis sine wave signals .phi..sub.0 -.phi..sub.M
are generated. The (M+1) synthesis sine wave signals .phi..sub.0
-.phi..sub.M are respectively generated so as to have phase differences
at regular intervals. The (M+1) synthesis sine wave signals .phi..sub.0
-.phi..sub.M are converted into a plurality of synthesis sine wave
signals T.sub.0 -T.sub.n by the matrix switch 12 respectively.
Such a conversion is executed by closing contact switches of the
matrix switch 12 in accordance with data that is generated by the
data generating unit 13 (in FIG. 4 closed switches are shown by
black points).
As shown in FIG. 6 the data generating unit 13 has: a delay time
generating unit 13a for calculating a delay time Td in accordance
with a deflection and a converging state of the ultrasonic wave
to be transmitted; and a phase conversion table 13b for converting
the delay time Td generated by the delay time generating unit 13a
into a phase .phi. of the ultrasonic wave to be transmitted on the
basis of the following relational equation.
where, f: frequency of the ultrasonic wave to be transmitted (first
and second sine wave signals X, Y)
As mentioned above, by converting the delay time Td generated by
the delay time generating unit 13a into the phase .phi. on the basis
of the phase conversion table 13 data to be outputted to the matrix
switch 12 can be generated on the basis of the delay time Td calculated
irrespective of the frequency of the ultrasonic wave to be transmitted.
The plurality of synthesis sine wave signals T.sub.0 -T.sub.n are
respectively amplified by the drive unit 7 and, after that, they
are supplied to the micro vibrators 1a-1h for transmission of the
ultrasonic probe 1. Thus, the micro vibrators 1a-1h for transmission
are driven and the ultrasonic continuous waves are irradiated toward
the object to be examined. The echo signals from the object to be
examined which are respectively received by the micro vibrators
1i-1p for reception of the ultrasonic probe 1 are respectively delayed
in accordance with their deflection angles and converging states
and, after that, they are added by the delay adder 8. The echo signal
after completion of the addition which is outputted from the delay
adder 8 is orthogonal-detected by the orthogonal detector 9 so
that the doppler signal is detected. The detected doppler signal
is frequency analyzed by the frequency analyzer 10 and an analysis
result of the frequency analyzer 10 is displayed on the display
unit 11.
As mentioned above, according to the ultrasonic continuous wave
doppler blood flow-meter of the embodiment, since this transmission
signal is generated by using the sine wave signal from which the
harmonic component of the clock signal generated by the reference
signal generator 2 is removed, the harmonic component is not mixed
from the transmission system into the reception system and a deterioration
in dynamic range of the reception system can be prevented. Since
the synthesis sine wave signal is generated by using the fixed coefficient,
a multiphase sine wave signal of a high precision can be generated
by the amplifier of a fixed gain. |