JPH0115298B2 - - Google Patents

Description

[Detailed description of the invention]

For example, to determine the presence or absence of cerebrovascular disorders such as cerebral arteriosclerosis, it is necessary to clarify the physical properties of cerebral blood vessels, but since the cerebral circulatory system is covered by the cranium, it is necessary to clarify the physical properties of cerebral blood vessels, such as the circulatory state and physical properties of blood vessel walls. It is impossible to directly measure cerebral circulation characteristics non-visually and non-invasively from the outside. Therefore, conventionally, the vascular properties of the carotid artery have been measured, and the data has been used to predict and prevent cerebrovascular disorders. In this way, the physical properties of the blood vessel distal to the measurement point are qualitatively estimated from the measurement data near the measurement point, but the physical properties of the blood vessel on the distal side can also be quantitatively expressed in the same way as the physical properties of the blood vessel near the measurement point. If possible, it would be extremely effective in predicting diseases. Therefore, the present invention proposes a device for measuring physical properties of peripheral blood vessels that can also quantitatively represent the physical properties of peripheral blood vessels. Embodiments of the present invention will be described below with reference to the drawings, but first, portions corresponding to the gist of the present invention will be extracted and explained with respect to FIGS. 1 and 5. This peripheral blood vessel physical property measurement device includes blood flow velocity measurement circuits 10A, 10B, and 20 that obtain a blood flow velocity output Vb based on the Doppler output from the first ultrasound probe 1 that measures the measurement site of the carotid artery. and a blood vessel diameter measuring circuit 50 that obtains a blood vessel diameter output Db based on the echo output from the second ultrasound probe 1 that measures the measurement site, and by multiplying the blood flow velocity output Vb and the blood vessel diameter output Db. , an absolute flow measuring device that obtains the absolute blood flow output g(t) of the measurement site of the carotid artery, a pulse wave measuring device 35, and a first device to which the absolute blood flow output g(t) from the absolute flow measuring device is supplied. Frequency analyzer 101 and pulse wave measuring device 3
The second frequency analyzer 103 is supplied after the blood pressure wave output P(t) from 5 is amplitude-corrected by the brachial artery cuff pressure value, and the output P(ω) of the second frequency analyzer 103 is The output Q of the frequency analyzer 101 of
(ω), the input impedance output Zin (ω) viewed from the measurement site to the distal side (however, Zin
(ω) is the central impedance output Zc (ω),
If the peripheral impedance output is Zp (ω), it is expressed as Zin (ω) = Zc (ω) + Zp (ω) ... (a), where Zc (ω) is the circulation resistance Rc, the circulation inductance Lc, When the circulating capacity is Cc, it is expressed as Zc (ω) = Rc + j (ωLc - 1 / ωCc) ... (b) where Rc, Lc, and Cc are where μ is the blood viscosity and ρ
is the blood flow density, l is the carotid artery blood vessel length, r is the average blood vessel radius at the measurement site, D is the blood vessel inner diameter at the measurement site, ΔP
When is the pulse pressure, ΔD is the deviation of the inner diameter of the blood vessel, and V _E is the volumetric modulus of the blood vessel, Rc=8μl/1333πr ⁴ ...(c) Lc=4ρl/3×1333πr ² ...(d) Cc=1333πr ² l/V _E ……(e) V _E = 1333D・ΔP/2ΔD ……(f) Zp(ω) is expressed as Zp(ω)= where resistance is Z _R and reactance is Z _I Z _R + jZ _I ......(g) Z _R and Z _I are expressed as: Z _R = R _T + _Rp /1 + ω ² Cp ² Rp ² ... (h) Z _I =ωCpRp ² /1+ω ² Cp ² Rp ² ...(i) Cp is expressed as follows, and if Zo is set as Zo=R _T +Rp, then Cp=−Z _I /ωRp(Z _R − Zo+Rp) ...(j) ), the average blood vessel radius r of the measurement site obtained from the blood vessel diameter output Db and diameter deviation output S'd from the blood vessel diameter measurement circuit 50, and the brachial artery cuff pressure. Using the intravascular diameter D and pulse pressure ΔP of the site, blood viscosity μ, blood flow density ρ, and carotid artery blood vessel length l, calculate the circulation resistance Rc by calculating equations (c) to (f).
Calculate the circulating inductance Lc and circulating capacitance Cc, and use these circulating resistance Rc, circulating inductance Lc, and circulating capacitance Cc to calculate the central impedance Zc near the measurement site by calculating the formula (b).
(ω) and the input impedance output from the first input impedance output circuit 105.
From Zin(ω), the central impedance output path 106
The peripheral impedance output circuit 108 obtains the peripheral impedance output Zp (ω) by subtracting the central impedance output Zc (ω) of , circulation resistance R _T ,
A circulation characteristic value determination circuit 109 that determines the values of Rp and circulation capacity Cp, and this circulation characteristic value determination circuit 109
The circulating characteristic value output is supplied from the input impedance output Zmod according to the circulating characteristic value.
(ω) Obtain the impedance output of the difference between the second input impedance output circuit 110 and each input impedance output Zin (ω) and Zmod (ω) of the first and second impedance output circuits 105 and 110. The circulation measurement value determination circuit 109 selects a circulation characteristic value that minimizes the square of the subtraction output of the subtraction circuit 111, and applies the selected circulation characteristic value to the peripheral blood vessel. This is a circulation characteristic value that indicates physical properties. FIG. 1 is a system diagram showing an overview of the measuring device according to the present invention, and shows carotid artery blood pressure, blood flow velocity, blood vessel diameter, and blood pressure at measurement sites necessary for clarifying the vascular properties of carotid arteries and cerebral blood vessels. Various data such as flow rate are measured non-invasively using ultrasound. 1 is an ultrasonic probe used for this measurement. 2 is the body surface, 3 is a blood vessel, and arrow a indicates the direction of blood flow. The ultrasonic probe 1 has a pair of wave receiving transducers 4A and 4B for measuring blood flow velocity, and a wave transmitting and receiving transducer 5 for measuring the diameter deviation of the blood vessel 1. In addition,
Details of the probe will be described later. The reflected waves received by the pair of wave receiving transducers 4A and 4B, that is, the Doppler outputs Sa and Sb, are supplied to the blood flow velocity measurement circuits 10A and 10B, which are configured identically, respectively, and are based on the Doppler outputs Sa and Sb. Then, the speed of blood flowing through the blood vessel 3 (blood flow speed) is determined.
In addition, the reflected waves received by the transducer 5 for transmitting and receiving waves have different reception times with respect to the excitation pulse, corresponding to blood vessel pulsations. Therefore, using this reflected wave,
A pulse output whose pulse width is the diameter deviation output of the blood vessel and the diameter of the blood vessel is formed. 50 is the above-mentioned radial deviation output Sd based on this reflected wave, that is, the echo output Sc.
and a blood vessel diameter measurement circuit for obtaining pulse output. Blood vessel diameter deviation output Sd, pair of blood flow velocity output Sa″,
The waveforms of Sb'' and the electrocardiogram output Se are shown in FIG. After being determined, it is supplied to the averaging circuit 81, and the average value output of the blood flow velocity of 5 heartbeats is determined.
The output regarding Db is supplied to the blood vessel cross-sectional area calculation circuit 40 constituting the second calculation processing circuit 90, and the output is supplied to the multiplier 45 through the averaging circuit 82 to obtain the blood flow rate So. 83 indicates an averaging circuit. Therefore, from the circuit 81, the averaged blood flow velocity
Vb′ is calculated from the multiplier 45 as the averaged blood flow So
However, the averaged blood vessel diameter deviation output Sd' is obtained from the circuit 83 (see FIG. 3). These outputs and the pulse wave output obtained from the pulse wave meter 35
P _B is supplied to the third arithmetic processing circuit 100,
Circulatory resistance R _T , R _P and volume representing cerebral blood vessel physical properties
Each value of _CP is determined. The pulse wave measuring device 35 uses a pressure transducer 36 as is well known.
Therefore, this pulse wave measuring device 35 is provided with a bridge circuit 37 and an amplifier 38. Now, in this embodiment, the input impedance output circuit provided in the third arithmetic processing circuit 100 receives an output So indicating the blood flow rate and a blood pressure wave output.
P _B is supplied, and from this, the impedance output Zin of the carotid artery including the peripheral blood vessels, that is, the cerebral blood vessels.
is formed, and this impedance output Zin
and the impedance output near the measurement unit, that is, the impedance output of the carotid artery that exists from the measurement unit to the cerebral blood vessels (referred to as central impedance output)
Peripheral impedance output indicating cerebral blood vessel physical properties from Zc, i.e. cerebral blood vessel impedance output
Zp is formed. In other words, the electric circuit model of the carotid artery is the transmission model Mc corresponding to the measurement site, as shown in Figure 4.
Since it is considered to be a combination of the transmission model Mp that reflects the peripheral side, the impedance of the entire model, that is, the input impedance output
Impedance of model Mc for Zin and measurement site
If Zc is known, the peripheral impedance Zp regarding the model Mp can be found. In addition, the model
Mp is a modified wind cell model. Figure 5 shows such peripheral impedance Zp.
This is a specific example of the third arithmetic processing circuit 100 for forming the . First, if the output So indicating the blood flow outputted from the second arithmetic processing circuit 90 is assumed to be q(t) for convenience of explanation, this blood flow output q(t) is calculated by the frequency analyzer 101 at each frequency of 0 to 10 Hz. Decomposed by frequency. Frequency analysis is generally performed by Fourier transform. Let the output of the frequency analyzer 101 be Q(ω). Here, ω is the angular frequency. On the other hand, the amplitude of the blood pressure wave output P _B obtained by the pulse wave meter 35 is corrected in the amplitude correction circuit 39 using the brachial artery cuff pressure value supplied to the terminal 102. The corrected blood pressure wave output P(t) is also analyzed for each frequency by the frequency analyzer 103, and this output P(ω) and the above-mentioned output Q(ω) are supplied to the input impedance output circuit 105. . In the electric circuit model, blood pressure is taken as voltage,
Since blood flow can be considered as a current, this impedance output circuit 105 outputs an output P(ω) related to blood pressure waves and an output Q(ω) related to blood flow.
By calculating the ratio between the two, the carotid artery input impedance output Zin(ω) can be obtained. By the way, the central impedance output Zc (ω) at the carotid artery measurement section is the composite impedance of the circulation resistance Rc, circulation inductance Lc, and circulation capacity Cc, as shown in Figure 4, and these are each expressed by the following formulas. It can be expressed as Rc＝8μl／1333πr ⁴ ……(1) Lc＝4ρl／3×1333πr ² ……(2) Cc＝1333πr ² l／V _E ……(3) V _E ＝1333D・ΔP／2ΔD ……(4) However, μ: Blood viscosity ρ: Blood flow density l: Carotid artery blood vessel length r: Average blood vessel radius at the measurement site D: Blood vessel inner diameter at the measurement site △P: Pulse pressure △D: Deviation of blood vessel inner diameter (=Sd) V _E : Volume elastic modulus of blood vessel μ, ρ, l (=10 to 15 cm) are constants, r, D,
ΔP can be determined by using the outputs Db and Sd of the blood vessel diameter measuring circuit 50 and the brachial artery cuff pressure value, so if these constant values and measured values are supplied to the central impedance output circuit 106, the central A side impedance output Zc (ω) is obtained. This central side impedance output Zc (ω) and the above-mentioned input impedance output Zin (ω) are further supplied to the peripheral side impedance output circuit 108, from which both impedance outputs Zin (ω) and
An output of the difference between Zc(ω), that is, a distal impedance output Zp(ω) is formed. This distal impedance output Zp (ω) is the composite impedance of the distal circulation resistance R _T , R _P and the distal circulation capacity Cp as shown in Fig. 4, so each circulation characteristic value of R _T , R _P and C _P To find the angular frequencies ω _i and ω _i+1 (i=0
...Find by least squares approximation so that the composite impedance Z when substituting each circulation characteristic value in step 10) is closest to the distal impedance output Zp (ω) found from the measurement data. Note that the circulation characteristic values R _T , R _P and C _P are as follows. Zp＝Z _R +jZ _I ……(5) Z _R ＝R _T +Rp／1＋ω ² Cp ² Rp ² ……(6) Z _I ＝ωCpRp ² /1＋ω ² Cp ² Rp ² ……(7) Cp＝−Z _I / ωRp (Z _R −Zo+Rp) ...(8) Zo=R _T +Rp ...(9) And the circulating capacity C _P (ω _i ) of ω _i (=2πf _i ) and ω _i+1
From the circulating capacity C _P (ω _i+1 ) to one circulating resistance R _P (ω _i ,
ω _i+1 ) is calculated. R _P = {ω _i・Z _I (ω _i+1 )} (Z _R (ω _i )−Z _O ) − {ω _i+1
・Z _I (ω _i )}(Z _R (ω _i+1 )−Z _O )/ω _i+1・Z _R (ω _i )
−ω _i・Z _R (ω _i+1 )……(10) However, Z _I (ω _i ): Z _I Z _R ( _{ω i} ): Z _R at ω _i Also, R _T = Z _O −R _P ...(11) Therefore, the peripheral impedance output Z _P (ω) is supplied to the circulation characteristic value determining circuit 109, and the circulation characteristic values R _T (ω) and R _P at the desired frequency are determined. (ω) and C _P
(ω) is determined. The circulation characteristic value output is supplied to the input impedance output circuit 110 of the electric circuit model, and the input impedance output Zmod(ω) at the circulation characteristic value at each frequency is output.
And this input impedance output
The difference between Zmod (ω) and the measured input impedance Zin (ω) Z _io (ω) − Zmod (ω) 2
Circulation characteristic values R _T (ω), R _P when the power is minimized
(ω) and C _P (ω) are output as circulation characteristic values indicating peripheral blood vessel physical properties. 111 is a subtraction circuit for obtaining a differential impedance output, and 112 is its output terminal. A data recorder, a waveform observation device, etc. are connected to the output terminal 112. FIG. 6 shows a more practical arithmetic circuit 120 for obtaining circulation characteristic values indicating peripheral blood vessel physical properties. In FIG. 5, the circulation characteristic value is selected so that the square of the difference between the input impedance obtained by substituting the circulation characteristic value and the input impedance obtained by measurement is minimized, and thereby, This is a case where circulation characteristic values indicating peripheral blood vessel physical properties are obtained, but in Fig. 6, blood flow output is used instead of input impedance, and blood flow output to which circulation characteristic values are substituted, and measurement This is a case where the circulation characteristic value is selected so that the comparison output becomes the minimum, and thereby the circulation characteristic value indicating the physical properties of the peripheral blood vessel is obtained.
That is, the circulation characteristic value output inputted to the terminal 113 is mainly supplied to the characteristic value correction circuit 121 as a characteristic value determining circuit for correcting the peripheral circulation capacity _CP . In this case, the cyclic characteristic values R _T , Rp,
It is known that there is no problem in terms of accuracy even if the circulating resistances R _T and Rp are respectively treated as constants obtained by multiplying the resistance of the central impedance Zc by a predetermined coefficient. Only the circulating capacity Cp is changed. The corrected cyclic characteristic value output from the characteristic value correction circuit 121 is supplied to the input impedance synthesis circuit 122 to form the input impedance Zmod(ω) of the electric circuit model, which is the output P(ω) of the frequency analyzer 103. ω)
It is also supplied to a circuit 123 that obtains an analysis output Q'(ω) regarding the blood flow rate. Therefore, this circuit 123
Then, signal processing of P(ω)/Zmod(ω) is performed. The analysis output Q'(ω) is supplied to a resynthesis circuit 124 to form an analog blood flow output q'(t), and this output q'(t) is supplied to a second comparator circuit 125.
Blood flow output q output from the arithmetic processing circuit 90 of
(t), and the characteristic value correction circuit 121 is controlled so that the comparison output becomes the minimum. Therefore, the circulation characteristic values R _T , R _P and C _P obtained at the output terminal 126 of the characteristic value correction circuit 121 become the final measured values indicating the blood vessel physical properties. The outline of the measuring device according to the present invention is as described above. Next, the configuration and operation of each part will be sequentially explained. For convenience of explanation, we will first explain the blood vessel diameter measuring circuit 50.
I will explain from. FIG. 7 is an example of a blood vessel diameter measuring circuit 50,
The oscillator 51 is used to obtain an excitation pulse Pf to be supplied to the vibrator 5 of the probe 1, and in this example, a pulse output of 10 kHz is used. The natural vibration frequency of the vibrator 5 is 6MHz. 52 indicates an output amplifier. The echo output Sc received by the transducer 5 (C and Sf in FIG. 8 indicate the transmitted pulses) is supplied to a wideband amplifier circuit 53, which also includes the transducer 7, although not shown. A circuit is provided for trapping the Doppler outputs Sa and Sb obtained by excitation. As for the echo output Sc, as shown in FIG. 8C, echo pulses Sg and Sh are obtained corresponding to the front wall 3A and the rear wall 3B of the blood vessel 3, respectively. Moreover, since each echo pulse Sg, Sh corresponds to the outer diameter wall 3Aa, 3Ba and the inner diameter wall 3Ab, 3Bb, respectively, the echo pulse Sg ₂ and Sh ₁ related to the inner diameter wall 3Ab, 3Bb of the echo pulse Sc are different from each other. The time width corresponds to the blood vessel diameter Db. Therefore, the gate pulses following the echo pulses Sg ₂ and Sh ₁ associated with the inner diameter walls 3Ab, 3Bb, respectively
Radial deviation output by Pca, Pcb (Fig. 8 D, E)
Can form Sd. In this example, a special circuit called an echo tracking circuit is used to generate gate pulses Pca and
It is formed from Pcb. In FIG. 7, 50A and 50B indicate echo tracking circuits, one circuit 50A is for forming the gate pulse Pca, and the other circuit 50B is for forming the remaining gate pulse Pcb. be. Starting with one echo tracking circuit 50A, 54A is a delayed oscillation circuit, which is composed of a voltage comparator 55A and a monostable multivibrator 56A triggered by its output.
This multiple output is supplied as a gate pulse Pca together with an echo pulse Sc to a phase comparator 57A which operates as a gate circuit. Since the gate pulse Pca is adjusted to be generated at the position of the echo pulse Sg ₂ corresponding to the inner diameter wall 3Ab of the front wall 3A among the echo pulses Sc, the phase relationship between the echo pulse Sg ₂ and the gate pulse Pca is now If the configuration is as shown in FIG. 9A and B, the output Sia of the phase comparator 57A at this time will be as shown in FIG. Becomes zero. This output Ea is superimposed on the offset voltage Va obtained by the offset voltage adjusting variable resistor 59A,
Its output is supplied to voltage comparator 55A. This voltage comparator 55A is supplied with a sawtooth reference output Ec as shown in FIG. 10A. 6
0 is a circuit for forming this reference output Ec,
Driven by excitation pulse Pf. Therefore, since the excitation pulse Pf has a frequency of 10 kHz, this reference output Ec also has a period corresponding to this excitation pulse Pf. Now, since the comparison voltage is Va, the reference output Ec
When they match, the comparison output is output and the multivibrator 56A is triggered, resulting in the gate pulse Pca shown in FIG. 10B. Note that the pulse width of this gate pulse Pca is selected to be 1/2 of the natural vibration period of the vibrator 5. When the echo pulse Sg ₂ changes as shown by the broken line in FIG. 8A with respect to the gate pulse Pca,
The output gated by this gate pulse Pca
Since Sia becomes as shown in figure D, at this time it becomes a negative smoothed output Ea, and the input voltage to the voltage comparator 55A decreases. Therefore, the gate pulse Pca
moves to the position shown in FIG. 10C. In this case, the gate pulse Pca moves to the point where the smoothed output Ea becomes zero. echo pulse
If Sg ₂ moves to the right contrary to the above, the output Sia
becomes as shown in FIG. 9E, and the gate pulse Pca similarly shifts to the right as shown in FIG. 10D. Since the phase variation of the echo pulse _Sg2 is caused by the blood flow flowing through the blood vessel 3, the deviation state of the blood vessel wall appears as a phase variation of this gate pulse Pca. Similarly, the other echo tracking circuit 5
0B, as shown in FIG. 8E, the rear wall 3
Gate pulse corresponding to the deviation of the inner diameter wall 3Bb of B
Pcb is formed, and by setting the flip-flop circuit 61 with the above-mentioned gate pulse Pca and resetting it with this gate pulse Pcb, the blood vessel diameter can be adjusted.
Pulse output Pc (8th
Figure F) can be formed. Therefore, the systolic phase of blood vessel 3 is now A in FIG.
If the diastolic phase is G in the same figure, the pulse output Pc will change from F in the same figure to I in the same figure in accordance with this blood vessel pulsation. Pulse output Pc is terminal 61a
This is output to a DC amplifier circuit 6 via a smoothing circuit 62 with a cutoff frequency of 60Hz.
3. Its output or radial deviation output
Since Sd is as shown in Figure 2C, it can be seen that the blood vessel diameter is contracting and expanding due to blood flow. The pulse output Sc is further supplied to an arithmetic processing circuit 64 for determining the blood vessel diameter Db, and the blood vessel diameter Db (either digital output or analog output is acceptable) is determined. In addition, by adjusting the variable resistors 59A and 59B, the offset voltages Va and Vb change, and thereby the positions of the gate pulses Pca and Pcb can be adjusted, so that the gate pulse Pca with respect to the echo pulses Sg ₂ and Sh ₁ , Pcb can be fine-tuned. Therefore, it is possible to obtain gate pulses Pca and Pcb that completely match the inner wall of the blood vessel. Next, an ultrasonic probe 1 suitable for application to the present invention will be described with reference to FIG. 11 and subsequent figures. The blood flow velocity Vb is measured by using Doppler output, which is a reflected wave of ultrasound, and this Doppler output is determined by the angle of contact of the probe 1 with the body surface 2, that is, with respect to the carotid artery 3, as shown in Fig. 11. It varies greatly depending on the ultrasonic irradiation angle _θT . Since it is impossible to always fix the irradiation angle θ _T constant during blood flow velocity measurement, accurate flow velocity measurement cannot be expected by using probe 1 as shown in Fig. 11. I can't. In order to eliminate this measurement error, a pair of probes may be used to measure blood flow, and reflected waves obtained by each probe may be used (the reason for this will be described later). Therefore, the ultrasonic probe 1 shown in FIG.
At least three ultrasonic transducers are used to measure blood flow velocity (in principle, two transducers for transmitting and receiving waves are required). The example shown in FIG. 12 is a case where three vibrators are used, and 6 is a mounting plate for the vibrators. A wave transmitting transducer 7 used for blood flow velocity measurement is mounted at a predetermined position on the mounting plate 6 at a predetermined angle with respect to the flat surface 6a of the mounting plate 6 so as to have a predetermined irradiation angle.
A pair of wave receiving vibrators 4A and 4B are attached to the front and rear of the wave transmitting vibrator 7. The mounting angle is such that the reflected wave from point P can be received as shown in the figure, and specific examples of these angles θ _a and θ _b will be described later. As shown in FIG. 13, the vibrators 7, 4A, and 4B are arranged in a straight line. Note that these vibrators 7, 4A, and 4B are rectangular as shown in the figure, and the length l is determined based on the diameter of the blood vessel to be measured. Since the pipe diameter Db is approximately 7 to 10 mm at maximum, the length may be selected to be approximately 10 mm. and,
The natural vibration frequency of the vibrators 7, 4A, and 4B is
A 5MHz ceramic resonator is used. A pair of wave receiving vibrators 4 sandwiching the wave transmitting vibrator 7
If A and 4B are arranged, there is no need to use an independent transmitting transducer for each receiving transducer 4A and 4B, and if there is only one transmitting transducer, the irradiation point P does not shift and the wave receiving transducer 4A,
4B can receive only the reflected wave from point P. The transducer 5 for measuring the diameter deviation of blood vessels is the receiving transducer 4
It is placed on the side of B. Specifically, this transducer 5 is located in the same arrangement direction as the other transducers, is in front of the transducer 4B, and is arranged so that the ultrasonic irradiation angle is perpendicular to the blood vessel 3. The mounting position of this vibrator 5 is selected so that the ultrasonic irradiation point of this vibrator 5 is the same irradiation point P as that of other vibrators 7. As shown in the figure, a hollow hole 8a is formed in the mounting plate 6 and the reinforcing member 8 itself in a portion corresponding to the mounting position of the vibrator 5, and a backing material 9 is filled in the hole 8a. It is attached and fixed at the tip. 9A is a screw for fixing the backing material 9. Note that this vibrator 5 is a barium titanate vibrator used for both transmitting and receiving waves, and is intermittently excited by a 10 kHz pulse. When the ultrasonic probe 1 is configured in this way,
Blood flow velocity Vb can be determined as follows. Now, as shown in FIG. 14, the transducer 7 and the blood vessel 3
Let the angle between the transducer 4A and the blood vessel 3 be θ _T , and the angles between the transducer 4A and the blood vessel 3 be θ _a and θ _b , respectively. θ _b −
When measuring blood flow with θ _a = θ always held at a predetermined angle, the ultrasonic probe 1 applied to the body surface 2
Almost constant measurement output can be obtained even if the angle changes slightly. The above reason will be explained with reference to FIG. It is known that the reflected wave of the ultrasound emitted from the transducer 7, that is, the Doppler output, is proportional to the cosine of the flow velocity of blood flowing through the carotid artery 3 and the ultrasound reception angle. That is, the Doppler outputs Sa and Sb received by the vibrators 4A and 4B are expressed by equations (12) and (13). Sa=kVb cos(θ _T +θ _b /2) ...(12) Sb=kVb cos(θ _T +θ _a /2) ...(13) k=2fs/C ...(14) However, fs: Oscillator 7 natural vibration frequency C: Transmission speed Now, Then, according to Fig. 15, when point C and point D are located on the circumference of a circle whose diameter is , the Doppler output Sa' represented by the line segment and the line segment
The Doppler output Sb′ represented by AC is
Since the receiving angle is different between the case of Fig. 14 and the case of Fig. 15, The relationship will be like this. And in this Figure 15, It is. Assuming that the line segment is η−ξ=θ _b −θ _a =θ, Therefore, the blood flow velocity Vb given by equation (17) is becomes. It was confirmed that there was not much difference between the measured value (calculated value) of the blood flow velocity Vb obtained based on this equation (19) and the true blood flow velocity V _B to be measured.

【table】

[Table] The data in Table 1 is the calculated value Vb using equation (19) when θ=15° and the true blood flow velocity V _B to be measured is 60.0 cm/sec and 100.0 cm/sec. shows. In this way, it was found that when two probes are used, the angle dependence does not appear so clearly. Therefore, even if the contact angle of the probe 1 changes each time a measurement is made, it hardly affects the blood flow velocity measurement. The possible range of the angle θ is not particularly limited, but
In this example, θ=20° is selected. As mentioned above, since the measurement error of a single probe is the smallest when θ _T = 60°, the illumination angle θ _T of the transducer 7 is
Selected near 60°. In this example, θ _T =65° and θ _a
= 55°, and θ _b = 75°. FIG. 16 shows a circuit for measuring blood flow. In the figure, 46 is an ultrasonic oscillator, and Doppler outputs Sa and Sb, which are reflected waves, are supplied to the respective measurement circuits 10A and 10B. These measurement circuits 10A and 10B are for obtaining blood flow waveforms,
Since they have substantially the same circuit configuration, the measurement circuit 10A related to the Doppler output Sa will be explained. The Doppler output Sa is supplied to an amplifier 11A, and then supplied to a detection circuit 13A through a filter 12A composed of a crystal for removing output caused by backflow of blood. Here, after envelope detection, the bandpass filter 1
4A. The lower limit of the filter is for removing Doppler signals accompanying contraction and expansion of the blood vessel itself, and the upper limit is determined from the viewpoint of S/N. In this example, it is configured to pass 80Hz to 7kHz. Note that if this filter output is supplied to the speaker 48 through the switch SW and the amplifier 47, the Doppler output Sa, that is, the blood flow can be heard. The filter output is supplied to the zero-cross counter 16A and then to the low-pass filter 17A. After passing through this filter 17A, the phase of the signal shifts by about 45 degrees when the signal frequency is 10Hz, as shown in Figure 18. Put it away. Therefore, a differential circuit 18A for phase correction is provided after the filter 17A.
and a low pass filter 19A for removing noise included in the differential output.
is connected. The output Sa'' of this filter 19A is the final output of the measuring circuit 10A. Also in the other measuring circuit 10B, the oscillator 4B
An output Sb'' related to the Doppler output Sb obtained in is formed, but these outputs Sa'' and Sb'' are processed by the first arithmetic processing circuit as shown in equation (19). 20. This arithmetic processing circuit 20 is configured as shown in FIG. , to explain step by step, the output Sa″,
Sb'' is supplied to a division circuit 21 to process Sb''/Sa'', and then supplied to a multiplication circuit 22. This multiplication circuit 22 is supplied with the output of a 1/sin θ constant circuit 23A. This multiplication output is supplied to the synthesizer 25 at the subsequent stage.
The output of 3B is supplied, the computation process of (cotθ-Sb″/Sa″×1/sinθ) is performed in the combiner 25, and the output is squared in the next squarer 26. Its output is supplied to adder 27. This adder 27 is supplied with the output of a constant circuit 23C of 1 within the root (√) shown in equation (19),
(19) The calculation of the formula in the root of the formula will be performed. After being subsequently supplied to the square root circuit 28,
is supplied to the multiplier 29 together with the above-mentioned output Sa'',
Further, its output is supplied to a multiplier 30 to which the output of the 1/k constant circuit 23D is supplied, and all operations in equation (19) are performed here. Therefore, the blood flow velocity Vb expressed by equation (19) is obtained at the output end. Here, the blood flow rate is the unit cross-sectional area of the carotid artery and the blood flow velocity.
It is obtained from the product of Vb. Therefore, as shown in FIG. 16, a second arithmetic processing circuit 90 is further provided after the first arithmetic processing circuit 20, and the final blood flow rate is processed here. Next, this arithmetic processing circuit 90 will be explained again with reference to FIG.
Since Db is the output of the processing circuit 64 in FIG.
You can easily calculate using this output. That is, the blood flow So (V to capacity) is expressed by equation (20). V=Vb'・π・(Db/2) ² ...(20) However, Vb' is the average value output of Vb.
A is a constant circuit, and 42 is a division circuit. The input 40a is supplied with an output related to the above-mentioned blood vessel diameter Db. Therefore, the calculation of Db/2 is performed in these circuits, and the output thereof is supplied to the squaring circuit 43. The output is then supplied to a multiplier 44 to be multiplied by a constant π. 41B
is a constant circuit for finding the constant π. The multiplication output is further supplied to a multiplier 45 together with the blood flow velocity Vb' obtained by the first arithmetic processing circuit 20. Since the final blood flow V is obtained in this manner, the absolute flow required for the blood vessel properties can be known as mentioned at the beginning. As explained above, according to the present invention, it is possible to quantitatively express not only the physical properties of the blood vessel near the measuring part but also the physical properties of the blood vessel distal to the measuring part, especially when measuring the carotid artery as in the above-mentioned embodiment. To provide a measuring device that is effective in predicting and preventing cerebrovascular disorders, since it is possible to know the circulation characteristic values of cerebrovascular vessels, which cannot be measured noninvasively and noninvasively from the outside. Can be done. In addition, in the embodiment described above, the arithmetic processing circuit 20,
90 and 100 and cyclic characteristic value calibration circuit 120
Although shown as analog circuits, these can also be constructed with digital circuits.

[Brief explanation of drawings]

FIG. 1 is a schematic system diagram showing an example of the present invention, FIGS. 2 and 3 are various waveform diagrams that can be observed by the measuring device according to the present invention, and FIG. 4 shows the peripheral side from the measurement site. The electric circuit model of the carotid artery, Figure 5 is a system diagram of the main parts of the arithmetic processing circuit, and Figure 6 is a diagram of the main parts of the arithmetic processing circuit.
The figure is a system diagram showing an example of a calibration circuit for circulation characteristic values.
FIG. 7 is a system diagram showing an example of a blood vessel diameter measuring circuit, and FIGS. 8 to 10 are waveform diagrams for explaining its operation.
FIG. 11 is an explanatory diagram of an ultrasonic probe, FIG. 12 is a vertical cross-sectional view of an ultrasonic probe suitable for application to the present invention, FIG. 13 is a bottom view thereof, and FIGS. 14 and 1.
Fig. 5 is an explanatory diagram of the ultrasonic probe, Fig. 16 is a system diagram showing an example of a blood flow measurement circuit, Fig. 17 is a system diagram showing an example of an arithmetic processing circuit, and Fig. 18 is an illustration of the output of the low-pass filter 17A. It is a curve diagram showing amplitude and phase. 1 is an ultrasonic probe, 3 is a blood vessel, 4A and 4B are wave receiving transducers, 5 is a wave transmitting and receiving transducer, 10A,
10B is a blood flow velocity measurement circuit, 50 is a blood vessel diameter measurement circuit, 71 and 72 are cathode ray tubes, 100 is an arithmetic processing circuit, 120 is a circulation characteristic value calibration circuit, Sa, Sa'',
Sb, Sb″ is Doppler output, Vb is blood flow velocity, Sd is blood vessel diameter deviation output, Db is blood vessel diameter, So is blood flow rate,
Sc is echo output and Pc is pulse output.

Claims (1)

[Scope of Claims] 1. A blood flow velocity measuring circuit that obtains a blood flow velocity output Vb based on a Doppler output from a first ultrasonic probe that measures a measurement site in the carotid artery; and a blood vessel diameter measurement circuit that obtains a blood vessel diameter output Db based on the echo output from the ultrasound probe No. 2, and by multiplying the blood flow velocity output Vb and the blood vessel diameter output Db, the absolute blood pressure at the measurement site of the carotid artery is calculated. An absolute flow rate measuring device that obtains a flow rate output g(t), a pulse wave measuring device, and an absolute blood flow rate output g from the absolute flow rate measuring device.
(t) to which the blood pressure wave output P(t) is supplied; and a second frequency analyzer to which the blood pressure wave output P(t) from the pulse wave measuring device is supplied after amplitude correction with the brachial artery cuff pressure value. Then, the output P(ω) of the second frequency analyzer is divided by the output Q(ω) of the first frequency analyzer to obtain the input impedance output Zin(ω) when looking at the distal side from the measurement site. ) (However, for Zin (ω), if the central impedance output is Zc (ω) and the peripheral impedance output is Zp (ω), then Zin (ω) = Zc (ω) + Zp (ω) ... (a) Zc(ω) is expressed as Zc(ω)=Rc+j(ωLc−1/ωCc)...(b), where Rc is the circulating resistance, Lc is the circulating inductance, and Cc is the circulating capacity. , Lc, Cc are μ the blood viscosity, ρ
is the blood flow density, l is the carotid artery blood vessel length, r is the average blood vessel radius at the measurement site, D is the blood vessel inner diameter at the measurement site, ΔP
When is the pulse pressure, ΔD is the deviation of the inner diameter of the blood vessel, and V _E is the volumetric modulus of the blood vessel, Rc=8μl/1333πr ⁴ ...(c) Lc=4ρl/3×1333πr ² ...(d) Cc=1333πr ² l/V _E ……(e) V _E = 1333D・ΔP/2ΔD ……(f) Zp(ω) is expressed as Zp(ω)=Z _R +jZ, where resistance is Z _R and reactance is _I ...(g), and Z _R and Z _I are expressed as R _T and Rp for circulation resistance and Cp for circulation capacity, Z _R = R _T + Rp/1 + ω ² Cp ² Rp ² ... (h) Z _I = -ωCcRp ² /1 + ω ² Cp ² Rp ² ...(i) Also, Cp is expressed as Zo = R _T + Rp, then Cp = Z _I /ωRp (Z _R - Zo + Rp) ...It is expressed as (j). ), a first input impedance output circuit that obtains the blood vessel diameter output Db and the diameter deviation output S'd from the blood vessel diameter measurement circuit, and the average blood vessel radius r of the measurement site determined from the brachial artery cuff pressure. Using the intravascular diameter D and pulse pressure ΔP of the site, blood viscosity μ, blood flow density ρ, and carotid artery length l, the above formula (c) is calculated.
~(f) is performed to obtain the above-mentioned circulating resistance Rc, circulating inductance Lc, and circulating capacitance Cc, and
Using these circulating resistance Rc, circulating inductance Lc, and circulating capacity Cc, calculate the above formula (b),
Central impedance Zc (ω) near the above measurement site
A central impedance output circuit calculates A distal impedance output circuit that obtains a side impedance output Zp, and a distal impedance output Zp (ω) from the distal impedance output circuit are supplied to determine the values of the circulating resistances R _T and Rp and the circulating capacitance Cp. a cyclic characteristic value determining circuit; a second input impedance output circuit that is supplied with the cyclic characteristic value output from the cyclic characteristic value determining circuit and obtains an input impedance output Zmod (ω) according to the cyclic characteristic value; Each input impedance output Zin(ω) of the first and second impedance output circuits,
and a subtraction circuit that obtains an impedance output of the difference of Zmod (ω), and in the cyclic measurement value determination circuit, a cyclic characteristic value is selected such that the square of the subtracted output of the subtraction circuit is the minimum, A device for measuring peripheral blood vessel physical properties, characterized in that the circulation characteristic values determined by the blood flow are used as circulation characteristic values indicating blood vessel physical properties on the peripheral side.