JPH049058B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an ultrasonic Doppler device used to obtain blood flow velocity information in a living body. The purpose is to provide a Doppler device.

Conventionally, the ultrasonic pulsed Doppler method has been used as a means of simultaneously obtaining blood flow velocity information at many depths within a living body, and a circuit has been used that extracts Doppler signals as many times as the number of depths to be measured from the ultrasonic echo signal. The principle of the ultrasonic pulse Doppler method is explained, for example, by Hiroshi Furuhata, “Ultrasonic Pulse Doppler Blood Flow Meter,” Electronic Medicine,
23, published December 1976, is well known. The conventional example described below is also explained in "Multi-channel pulse Doppler blood flow meter using a minicomputer" by Masaaki Hirayama et al., IEICE MBE 79-63, published in 1978.

The conventional method disclosed in the above-mentioned document for extracting an ultrasound pulse beam and Doppler signals at nine points in a living body will be described below. FIG. 1 is a tomographic diagram of a living body illustrating the relationship between blood vessels in the living body, ultrasonic pulse beams, and extraction positions. An ultrasonic pulse beam 3 is emitted from an ultrasonic probe 1, and an echo signal is received by the ultrasonic probe 1. The positions 4-1 to 4-9 from which Doppler signals are extracted are inside the blood vessel of the living body and between the blood vessel walls 2. Therefore, position 4-
By frequency-analyzing the Doppler signals in 1 to 4-9, the state of distribution of blood flow velocity in blood vessels can be obtained.

Next, a conventional ultrasonic Doppler device will be explained. FIG. 2 is a block diagram of a conventional ultrasound Doppler device. Reference oscillator 5 generates a 3MHz reference signal. Based on this signal, the transmitter 6 supplies transmission pulses to the ultrasound probe 1 at a frequency of 4 MHz, and emits the ultrasound pulses into the living body. Furthermore, the ultrasound probe 1 receives ultrasound echo signals returned from the living body. After this received echo signal is amplified by an amplifier 7, a quadrature detection signal υ _a and υ _b is generated by a quadrature detector 8.
The quadrature detector 8 uses the 3MHz reference signal of the reference oscillator 5 with a phase shift of 0° and 90° as a comparison signal, and calculates υ _a and υ _b , which are the products of this comparison signal and the input echo signal. Output. Furthermore, this υ _a
and υ _b are extracted from the Doppler signal extraction positions 4-1 to 4-1 shown in FIG. 1 by nine gate circuits 9-1 to 9-9.
4-9, and integrator 11
-1 to 11-9, the signal corresponding to one transmission is time-integrated as a unit to obtain Doppler signals (V _a1 to V _b1 to (V _a9 to V _b9 ) at each extraction position. This signal is Furthermore, sample hold circuits 12-1 to 1
2-9, the signal is sequentially selected by the selection switch 13, converted into a digital signal by the A/D converter 14, and supplied to the frequency analyzer 15. A frequency analyzer 15 corresponds to each extraction position.
The signals of V _a and V _b are analyzed and processed independently and output as nine independent pieces of blood velocity information, and the recorder 16
Record by. Frequency analysis has a transmission period of 4M
Obtained over time in Hz. This is done for the time changes of V _a and V _b . Note that the gate signal generator 10 is
Controls each gate time of gate circuits 9-1 to 9-9.

3A to 3E are diagrams for explaining the timing of gate signals, and FIG. 3A shows a transmission pulse transmitted at a cycle of 4 MHz. In the figure, b, c, d, and e are gate signals that control the gate circuits 9-1, 9-2, 9-3, and 9-9, respectively, and are generated from the transmission pulse at each Doppler signal extraction position 4-1, There is a delay by the time required for the ultrasonic waves to travel back and forth between 4-2, 4-3, and 4-9 and the probe 1. Further, the pulse width of the gate signal determines the resolution in the depth direction at the Doppler signal extraction position.

The means for extracting the Doppler signal explained above is
Blood velocity information can be obtained for many depths at the same time, but gate circuits 9-1 to 9-
9. Integrating circuits 11-1 to 11-9 and sample-and-hold circuits 12-1 to 12-9 are required, and the same number of gate signals must be generated. Therefore, when the number of depths to be extracted increases, the apparatus becomes very large-scale.

The present invention aims to eliminate such drawbacks and provide an ultrasonic Doppler device that can obtain blood flow velocity information at many depths with a simple device. explain.

The extraction positions of the Doppler signal in the living body are nine points shown as positions 4-1 to 4-9 in FIG. 1, as in the conventional example.

An ultrasonic Doppler apparatus according to an embodiment of the present invention will be explained with reference to the block diagram of FIG. Reference oscillator 5 generates a 3MHz reference signal. Based on this signal, the transmitter 6 supplies transmission pulses to the ultrasound probe 1 at a cycle of 4KHz, and emits the ultrasound pulses into the living body. Furthermore, the ultrasound probe 1 receives ultrasound echo signals returned from the living body. After amplifying this received echo signal with an amplifier 7, a quadrature detector 8
orthogonal detection signals υ _a and υ _b are obtained. The comparison signal of the quadrature detector 8 is the output signal of the reference oscillator 5
The signal is phase-shifted by 0° and 90° from the 3MHz reference signal, and the products υ _a and υ _b of this comparison signal and the input signal are output. This output signal is time-integrated by an integrator 11 to obtain V _a (t) and V _b (t). Here, t is a delay time from the integration start time of the integrator 11. The signal V _a (t) is supplied via a switch 13', while the signal V _b (t) is supplied via a delay line 17 and a switch 13' to an A/D converter 14 for conversion into a digital signal. The A/D converter 14 performs 20 A/D conversions and outputs V _a (t _o ) and V _b (t _o ). However, n
is 0 to 9. The frequency analyzer 15' was obtained
From V _a (t _o ) and V _b (t _o ), nine Doppler signals (V _a1 ,
V _b1 ) to (V _b9 , V _b9 ) are determined and frequency analyzed as independent signals. Each Doppler signal is a signal obtained in time series with a transmission period of 4 MHz. This analysis result is outputted from the frequency analyzer 15' as blood velocity information at each extraction position shown in FIG.
Record according to 6.

Next, the timing of A/D conversion will be explained. 5A to 5E are diagrams for explaining the timing of A/D conversion, and FIG. 5A shows the timing of emitting ultrasonic pulses. The timing for performing A/D conversion is set to the time shown in b in the same figure, which is delayed from t ₀ to t ₉ from the integration start time, and A/D conversion is performed 10 times. moreover,
Doppler signal extraction positions 4-1 to 4-9 shown in Figure 1
are equally spaced, and the round trip time of the ultrasonic wave during this period is ΔT
The delay time from the transmission pulse at each extraction point is _T1 to _T9 , respectively. Therefore, the relationship is ΔT=T _o+1 −T _o ……(1). Furthermore, for t ₀ to _{t 9} , T _o =t _o-1 +t _o /2 (2) ΔT=T _o −T _o-1 (3). Further, the digital signal V _a (t _o ) is V _a (t _o )=∫ ^t ₀ nυ _a (t) dt (4). Let ΔT be the time width corresponding to the conventional example and the pulse width of the gate signal, which determines the resolution in the depth direction of each extraction point. Next, the digital signal V _a (t _o ) is supplied to the frequency analyzer 15', and V _ao is determined according to equation (5).

V _ao = V _a (t _o ) − V _a (t _o-1 ) ...(5) where n = 1 to 9 This subtraction process is performed in order to obtain correct Doppler information at each extraction point (observation point). This is done to remove the (n-1)th integral value superimposed on the nth extraction point.

On the other hand, V _b (t) is delayed by ΔT via the delay line 17, and is supplied to the A/D converter 14 via the switch 13', and is delayed by Δt from the timing shown in FIG. Convert to digital signal at the timing shown in . The digital signal converted to the time t _o +Δt is V _b (t _o ) as shown by the following equation:
It is.

V _b (t _o )=∫ ^tn+ 〓 ^t 〓 _t υ _b (t−Δt)dt……(6) Here, Δt is set to 1/2 of ΔT, and the A/D converter 14
The conversion process is performed 20 times per transmission cycle from time t ₀ to time t ₉ +Δt at intervals of Δt. Also,
The switch 13' is activated by the signal shown in FIG. 5d.
The input of the A/D converter 14 is alternately switched to V _a (t) and V _b (t) signals. V _b (t _o ) obtained in this way is processed by the frequency analyzer 15' in the same way as V _a (t _o ).
and calculate V _bo according to equation (7).

V _bo =V _b (t _o )-V _b (t _o-1 ) (7) where n=1 to 9 Note that e in the figure is a timing signal that determines the integration interval of the integrator 11.

As described above, according to this embodiment, regardless of the number of depth settings for obtaining blood flow velocity information, the simple configuration consisting of one integrator 11, delay line 17, and simple switch 13' can be used. Doppler signals can be extracted and a large number of points can be observed simultaneously.

FIG. 6 is a block diagram of an ultrasound Doppler apparatus according to another embodiment of the present invention. Compared to the embodiment shown in FIG. 4, the delay line 17 and switch 13' are removed, and the switch is further divided into A/D converters 14-1 and 14-2.
The difference is that V _a (t _o ) and V _b (t _o ) are processed separately. Further, the timing for performing the A/D conversion is shown in FIGS. 7a to 7c. Figure 7a shows the transmission timing, Figure 7b shows the A/D conversion timing, Figure 7c shows the integration period, and the A/D conversion timing.
From _t0 to _t9 , parallel processing is performed in A/D converters 14-1 and 14-2. Further, A/D conversion is performed 10 times per one transmission cycle from t ₀ to t ₉ at intervals of ΔT.

Therefore, there is no complicated timing such as switch switching or time delay, resulting in a simpler configuration.

In the above embodiments, the A/D conversion intervals were equal intervals of Δt and ΔT, but the invention is not limited to this. Assume that the Doppler signal is extracted at the timing of T _o and T _{o +1} shown in Figure 8a, and the integral interval is t _o
Let t′ _o from t′ o and t′ _o+1 from t _o+1 , then at each timing of t _o , t′ _o , t _o+1 , t′ _o+1 in the device shown in the block diagram of A/D conversion is performed and a Doppler signal is extracted according to the following equations (8) and (9).

V _ao = V _a (t′ _o )−V _a (t _o ) …(8) V _bo = V _b (t′ _o )−V _b (t _o ) …(9) Set a wider integration interval However, as shown in figure c, the order of t′ _o and t _o+1 can be reversed, and V _ao
and V _bo can be determined using equations (8) and (9).
Note that t _o and t′ _o comply with the following formula.

T _o =t _o +t' _o /2 (10) As yet another embodiment, the timing of A/D conversion is set to an integer fraction of the reference signal. Further, the width of the integration interval is set to be an integral multiple of the period in which this A/D conversion is performed. At the timings shown in FIGS. 9a to 9d, a is the reference signal, b is the same A/D conversion timing, and c is the Doppler extraction position T _N and t. It can be set freely as long as it is at the center of the timing of _o or the timing interval of t _o . If the integral interval width is n times the period of A/D conversion and t _o to t _o+n shown in d of the same figure, V _aN , V _bN and T _N can be obtained from the following equations.

V _aN = V _a (t _o+n ) − V _a (t _o ) … (11) V _bN = V _b (t _o+n ) − V _b (t _o ) … (12) T _N = t _o +t _o+n /2 ... (13) Therefore, if the A/D conversion is set at a fast cycle and at an integral multiple of the phase detection signal, the position and integration interval can be set freely just by selecting and subtracting the digital signal. Doppler signals can be extracted depending on the width of the area. Furthermore, this position and integral interval can be easily changed by changing the software that defines the calculation method.

As explained above, according to the present invention, an ultrasonic echo signal is phase-detected, this signal is subjected to interval integration, and this integrated value is sampled in a time shorter than the emission timing period of an ultrasonic pulse. Since Doppler signal components are extracted by finding the difference between data at two matching points, Doppler signal components at many depths can be extracted simultaneously with a simple device.

[Brief explanation of drawings]

Fig. 1 is a tomographic diagram of a living body explaining the extraction position of the Doppler signal, Fig. 2 is a block diagram showing a conventional ultrasonic Doppler device, and Figs. 3 a to e are diagrams explaining the gate timing of the device. , FIG. 4 is a block diagram showing an embodiment of the ultrasonic Doppler apparatus of the present invention, FIGS. 5 a to 5 e are diagrams showing the timing of A/D conversion in the same embodiment, and FIG. Block diagram showing another embodiment of the ultrasonic Doppler device, No. 7
Figures a to c are diagrams showing the timing of A/D conversion in the same embodiment, and Figures 8 a to c and Figures 9 a to d are diagrams explaining the timing of A/D conversion in different embodiments. It is. 1... Probe, 2... Blood vessel wall, 4-1 to 4-2
...Doppler signal extraction position, 5...Reference oscillator, 6
...Transmitter, 8...Quadrature detector, 11...Integrator, 14, 14-1, 14-2, ...A/D converter, 15 and 15'...Frequency analyzer, 16...
Recorder.

Claims (1)

[Claims] 1. In an ultrasound Doppler device that obtains blood flow information at multiple points along the ultrasound propagation path, the phase of an echo signal obtained by emitting ultrasound pulses into a subject is detected. means for integrating the detected signal obtained by the detecting means in an integral interval synchronized with the emission timing of the ultrasonic pulse; An ultrasonic Doppler apparatus comprising: means for extracting a plurality of points in a time shorter than a period; and means for frequency-analyzing a signal of a difference between integral values at two adjacent points obtained by the extracting means. 2. The ultrasonic Doppler apparatus according to claim 1, wherein the means for extracting the integral value at a plurality of points performs the extraction using a signal synchronized with a comparison signal of the means for detecting the phase.