JPS624974B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an ultrasonic diagnostic apparatus capable of observing blood flow conditions such as blood flow velocity using the pulse Doppler method.

2. Description of the Related Art Ultrasonic diagnostic apparatuses that transmit ultrasonic pulses into a living body and process signals obtained from reflected waves to obtain tomographic images are conventionally known. On the other hand, an ultrasonic blood flow meter that detects the state of blood movement (blood flow) in a living body using the pulse Doppler method has also been known. With this device, it is possible to know the blood flow velocity, etc.
It is not possible to know in detail which part of the body it comes from. Therefore, ultrasonic diagnostic devices that can also view tomographic images in this ultrasonic blood flow meter are being developed recently.

By the way, in such an ultrasound diagnostic device, it is considered that tomographic image scanning for obtaining signals for displaying tomographic images and Doppler scanning for obtaining Doppler signals for detecting blood flow velocity are repeated alternately. . The transmitted ultrasonic pulses attenuate as they go deeper into the body, so when displaying tomographic images, reflected wave signals of about 20 cm, for example, are used. However, 20cm
Residual reflected waves return, albeit weak, from deeper places. Since the Doppler signal is about 40 dB smaller than the tomogram reflected wave signal, it is affected by this residual reflected wave. Therefore, if this residual reflected wave is mixed into the reflected wave signal from which the Doppler signal is obtained, there is a problem that accurate blood flow information cannot be obtained.

The present invention has been made in view of such conventional problems, and an object of the present invention is to provide an ultrasonic diagnostic apparatus capable of observing blood flow and capable of accurately detecting blood flow information such as blood flow velocity.

Examples of the present invention will be described below.

First, the pulse voltage applied to the ultrasonic transducer is
An embodiment of the present invention will be described in which the transmitted sound pressure when obtaining a tomographic image is suppressed by making it smaller during tomographic image scanning to obtain a tomographic image than during Doppler scanning to obtain a Doppler signal. FIG. 1 shows the configuration of the apparatus of this embodiment. A reference pulse (rate pulse) of a predetermined period generated in the reference pulse generator 11 is passed through switches S1 to Sn to variable delay circuits D1 to Dn.
, each given a predetermined delay. The delay times provided by these variable delay circuits D1 to Dn are determined by the ultrasonic wave transmission and reception direction, as described later.
These are controlled by the scan control circuit 12.

The reference pulse given a predetermined delay in each variable delay circuit D1 to Dn, that is, each delayed pulse, is
It passes through switches SW1 to SWn and is converted into a high voltage drive pulse in corresponding drive pulse generators (pulsars) P1 to Pn, and is converted into a high voltage drive pulse for each ultrasonic transducer T1.
~ applied to Tn. At this time, the scan control circuit 1
2, the high voltage in each of the drive pulse generators P1 to Pn is changed depending on whether the drive pulse is for obtaining a reflection signal for a tomographic image or a drive pulse for obtaining a Doppler signal. That is, the drive pulse voltage of the former is suppressed lower than that of the latter. Details of this drive pulse generator will be described later.

The ultrasonic pulses transmitted from the ultrasonic transducers T1 to Tn in this way are in phase in a certain specific direction corresponding to the delay time, and the ultrasonic pulses are transmitted in this direction. Become. The reflected ultrasonic waves are received again by these ultrasonic transducers T1 to Tn. At this time, the switches S1 to Sn and the switches SW1 to SWn have been switched from the solid line positions to the dotted line positions. Therefore, the signals received by the ultrasonic transducers T1 to Tn are again given a predetermined delay by the same variable delay circuits D1 to Dn, and then synthesized by the synthesizing circuit 13. Since the variable delay circuits D1 to Dn are in a state of giving the same delay time when receiving waves as when transmitting waves, it means that reflected ultrasonic waves from the direction in which the ultrasonic pulses were transmitted have been received.

The reflected signal synthesized in the synthesis circuit 13 is
In the case of tomographic image display, the amplitude is detected by the amplitude detection circuit 14 and supplied to the display device 15 as a brightness modulation signal.

On the other hand, when obtaining a Doppler signal, the phase detection circuit 16 detects the phase difference with the transmitted ultrasonic pulse signal, and the blood flow velocity is displayed on the display device 15.

FIG. 2 shows a circuit configuration of the drive pulse generator P1 in FIG. 1. This drive pulse generator P1 is a circuit that generates a high voltage to drive the ultrasonic transducer T1 at the timing of a delayed pulse that comes in through the switch SW1, and is a circuit that generates a high voltage that drives the ultrasonic transducer _T1 .
Capacitor C ₁ and resistor R ₁ connected in parallel, transistor Q ₁ , resistor R ₂ , coil L, capacitor
It consists of C ₂ and resistor R ₃ . This driving pulse generator P1 inverts the delayed pulse with an inverter _I1 , and an NPN type transistor _Q1 having a switching action.
Put it in. Capacitor _C1 is a speed-up capacitor.

Since the resistor R ₂ is connected to the power supply voltage V, the capacitor C ₂ is normally charged to the polarity shown, and a positive pulse (delayed pulse) is applied to the transistor Q ₁ .
When , this transistor turns on, a current flows in the direction of the arrow through the resistor _R3 , and this high voltage negative pulse is applied to the ultrasonic transducer T1. When transmitting pulses for tomographic images, the power supply voltage V generates a voltage _V2 lower than the voltage _V1 used when obtaining Doppler signals.

In this way, the power supply voltage V of each drive pulse generator P1 to Pn changes to _V1 or _V2 . This voltage control is performed in the scan control circuit 12. An example of this circuit configuration is shown in FIG. Diode D ₁ ,
D ₂ is connected in series between the ground and output terminals, a DC voltage V ₂ is applied to the diode D ₂ , a resistor R ₁₁ is connected in parallel to the diode D ₁ , and the NPN type transistor Q ₁₁ connected to the collector.

A DC voltage of V ₁ -V ₂ is applied between the emitter and output terminal of this transistor Q ₁₁ , and a capacitor C ₁₁ and a resistor R ₁₂ are connected in parallel to its base. The other end is an NPN type transistor _Q12
This collector end is connected to the collector of the resistor.
Connected to the DC power supply E ₁ via R ₁₃ . The base of transistor _Q12 is connected to the emitter via resistor _R14 . This base also has resistances R ₁₅ and R ₁₆
connected to the DC power supply E ₂ via. resistance
The connection point of R ₁₅ and R ₁₆ is connected to the photo coupler gate PH, which is connected to the DC power supply E ₃ via the resistor R ₁₇ .
It is also connected to the output terminal of the inverter _I11 .

When a negative pulse is applied to the inverter I ₁₁ , this pulse is inverted and applied to the transistor Q ₁₂ via the photo couple gate PH, and when this positive pulse is applied, the transistor Q ₁₂ is on, and therefore the transistor Q ₁₁ is off. , V ₂ is output to the output terminal V. On the other hand, when the input to the inverter _I11 is zero, the transistor _Q11 is turned on, and _V1 is output to the output terminal V.

Next, the operation of this embodiment of the present invention will be explained with reference to FIGS. 4 and 5.

The reference pulse generator 11 generates a pulse train having a rate frequency of 4 KHz, for example, as shown in FIG. 5a. During wave transmission, the switches before and after the variable delay circuits D1 to Dn are at the positions indicated by solid lines. First of all, the fourth
The variable delay circuits D1 to Dn are controlled by the scan control circuit 12 so that the ultrasonic waves are transmitted and received in the direction of the ultrasonic beam l1 in the diagram showing the directions of ultrasonic wave transmission and reception.
A delay time is set. Therefore, the reference pulse (rate pulse) t1 outputted from the reference pulse generator 11 is given a predetermined delay in each variable delay circuit D1 to Dn, and is applied to each drive pulse generator P.
1 to Pn, and becomes a high voltage drive pulse.

By the way, at this time, the third
The inverter _I11 of the control section shown in Figure 5b
It contains a pulse train as shown in . Therefore, during this wave transmission, the input of inverter _I11 receives a negative pulse, and the voltage at the V terminal is lower than _V1 .
A voltage of V ₂ is output (FIG. 5c) and supplied to each drive pulse generator P1 to Pn. After all, at this time
A driving pulse of _V2 is applied to the ultrasonic transducers T1 to Tn, and an ultrasonic pulse for scanning a tomographic image to obtain a tomographic image is transmitted in the direction of the ultrasonic beam l1 in FIG.

When receiving waves, the switches before and after the variable delay circuits D1 to Dn are turned to the dotted line side (not shown, but controlled by the scan control circuit 12), and the waves are received by the ultrasonic transducers T1 to Tn. The reflected ultrasonic waves pass through variable delay circuits D1 to Dn that provide the same delay time as during transmission, and are synthesized in a synthesis circuit 13. Thereafter, the amplitude of this composite signal is detected (detected) by the amplitude detection circuit 14 and displayed on the display device 15.

Next, the switches before and after the variable delay circuits D1 to Dn are turned to the solid line side again, and the variable delay circuit D
Each delay time from 1 to Dn is set so that the direction of transmission and reception of the ultrasonic wave is the direction of the ultrasonic beam L in FIG. 4. Therefore, the next reference pulse _t2 output from the reference pulse generator 11 is given a predetermined delay by the variable delay circuits D1 to Dn, and becomes each delayed pulse,
It is supplied to drive pulse generators P1 to Pn. At this time, the input of the inverter _I11 in FIG. 3 becomes 0, and the V terminal output becomes _V1 . Therefore, a drive pulse of _V1 is output from the drive pulse generators P1 to Pn and applied to the ultrasonic transducers T1 to Tn.
In this way, ultrasonic pulses for Doppler scanning for obtaining Doppler signals are transmitted in the direction of the ultrasonic beam L in FIG. 4. At the time of wave reception, the switches before and after the variable delay circuits D1 to Dn are turned to the dotted line side, so the reflected ultrasonic waves of the above ultrasonic pulses are received by the ultrasonic transducers T1 to Tn again and give the same delay. and is synthesized by a synthesis circuit 13. The phase of this composite signal is detected by the phase detection circuit 16, and the blood flow velocity and the like are displayed on the display device 15.

Similarly, ultrasonic waves are transmitted and received sequentially in the directions l ₂ , L, l ₃ , L, . . . and the blood flow velocity and tomographic image are displayed.

In the above embodiment, the transmitted sound pressure was changed by changing the voltage of the drive pulse generator (pulsar), that is, by lowering the voltage of the drive pulse when obtaining a tomographic image, the transmitted sound pressure at this time was suppressed. .

However, the present invention is not limited to this, and the transmitted sound pressure when obtaining a tomographic image may be suppressed by other methods. For example, as shown in Figure 5d, when obtaining a Doppler signal, a 3-cycle burst wave is used as the driving pulse applied to the ultrasonic transducer, and when obtaining a tomographic image, a 2-cycle burst wave is used to obtain a tomographic image. It is possible to suppress the transmitted sound pressure when obtaining.

As described above, according to the present invention, since the transmitted sound pressure of the ultrasonic pulse is suppressed when obtaining a tomographic image, the residual reflected waves are also sufficiently small. Therefore, the reflected waves at this time are unlikely to mix with the reflected ultrasound when obtaining Doppler signals, and even if they do mix, the level is very low, so accurate blood flow information can always be obtained.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of an embodiment of the present invention, FIG. 2 is a diagram showing an example of the circuit structure of the drive pulse generator in FIG. 1, and FIG. 3 is a partial circuit of the scan control circuit in FIG. 1. A diagram showing an example of the configuration, Figure 4 is the first
FIG. 5 is a diagram showing the ultrasonic beam direction of the apparatus in the figure, and is an explanatory diagram of the circuit operation of the embodiment of the present invention. 11...Reference pulse generator, 12...Scanning control circuit, 13...Synthesizing circuit, 14...Amplitude detection circuit, 15...Display device, 16...Phase detection circuit,
S1~Sn, SW1~SWn...Switch, D1~
Dn...variable delay circuit, P1-Pn...drive pulse generator, T1-Tn...ultrasonic transducer.

Claims (1)

[Claims] 1. An ultrasonic transducer that transmits ultrasonic pulses into a living body along an ultrasonic beam and receives reflected waves of the ultrasonic pulses; A scan control unit that alternately repeats Doppler scanning in which an ultrasound beam is scanned and tomographic image scanning in which scanning is performed while sequentially changing the direction of this ultrasound beam; a transmission sound pressure suppression unit that suppresses the transmitted sound pressure; a phase detection unit that detects the phase of the reflected wave signal obtained by Doppler scanning to determine the blood flow velocity; and a phase detection unit that detects the phase of the reflected wave signal obtained by the tomographic image scanning; The apparatus is characterized by comprising: an amplitude detection unit that detects amplitude and obtains a signal for displaying a tomographic image; and a display unit that is connected to the phase detection unit and the amplitude detection unit and displays the velocity of the blood flow and the tomographic image. Ultrasound diagnostic equipment. 2. The ultrasonic diagnostic apparatus according to claim 1, wherein the transmission sound pressure suppressing unit applies a drive pulse of a lower voltage to the ultrasonic transducer in the tomographic image scanning unit than in Doppler scanning. 3. The ultrasonic diagnostic apparatus according to claim 1, wherein the transmission sound pressure suppressing section applies a burst wave having a smaller number of cycles than Doppler scanning to the ultrasonic transducer during tomographic image scanning.