JPH02164346A - Ultrasonic pulse doppler blood stream diagnostic device - Google Patents

Abstract

PURPOSE:To provide any desired sample volume position and max. blood stream observing speed by controlling the pulsation period and the transport/ demodulation frequency, and removing pseudo sample volume position from unfavorable position without varying the max. blood stream observing speed. CONSTITUTION:Echo signal received by a probe 1 is amplified by a received signal amplification focusing circuit 3 and sent to a DC/AC detector circuit 5. From a wave sending spacing, transport/demodulation frequency determining circuit 10, a demodulation control signal (d) for controlling the demodulation frequency to fo1 is sent to this DC/AC detector circuit 5. Another DC/AC detector circuit 6 decides the demodulation frequency to fo1 on the basis of control signal for demodulation signal (d), and the echo signal is DC/AC detected and sent to range gate circuit 6. This range gate circuit 6 is a circuit to sample a signal DC/AC detected, which performs sampling in conformity to a range gate signal (e) from a wave sending spacing, transport/demodulation frequency determining circuit 10 and forwards the output signal therefrom to a frequency analyzing circuit 7. This frequency analyzing circuit 7 makes spectral analysis of signals in the integral division sampled and passes to an image information processing/converting part.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to an ultrasonic pulsed Doppler blood flow diagnostic device for observing blood flow velocity, for example, and particularly to measurement of blood flow velocity in a high pulse repetition frequency mode.

[Prior art] Figure 6 shows the conventional high pulse repetition frequency mode (hereinafter referred to as H).
FIG. 2 is an explanatory diagram showing the relationship between positional resolution in blood flow observation in ighPRF mode).

In the figure, the High PRF mode is a case where the pulse repetition frequency (PRF) is doubled compared to the normal pulsed Doppler method. In this case, if the sample point is set at A2, the echo signal EI obtained at that position also contains the echo signal El-1 from Al at the previous rate Tl-1. Therefore, as a Doppler output signal, Al
The Doppler signals of A2 and A2 are combined. When the PRF is increased by 3 times or 4 times, the output signal also becomes a combination of Doppler signals from 3 and 4 points.

By using the HighPRF mode, even fast blood flow deep in the body can be observed without loopback, but a pseudo sample volume exists between the sample volume where the blood flow is observed and the body surface. If blood flow also exists at this pseudo sample volume position, then the view n1
The display overlaps with the blood flow in the area, leading to misdiagnosis.

Furthermore, a wave transmission point also exists between the sample volume and the body surface. Even if a pseudo sample volume is brought to the transmission point, it will be affected by constraints such as the dynamic range of the device.

To avoid this, the PRF is slightly changed and controlled to a position where the pseudo sample volume does not match the transmitting point. However, when the PRF is changed, the maximum blood flow observation speed changes.

[Problems to be Solved by the Invention] The present invention has been made to solve such problems, and even if the pseudo sample volume is set at a position that does not adversely affect the observation, the maximum blood flow observation speed cannot be adjusted to the desired speed. The purpose is to obtain an ultrasonic pulsed Doppler blood flow diagnostic device that can maintain the value of .

[Means for Solving the Problems] The ultrasonic pulsed Doppler blood flow diagnostic device according to the present invention uses a high pulse repetition frequency mode to observe blood flow velocity. A sample volume input mechanism for setting the position, a maximum blood flow observation speed input mechanism for setting the maximum blood flow observation speed, and a sample volume position set by the sample volume input mechanism and the maximum blood flow observation speed input mechanism for setting the maximum blood flow observation speed. a determining means for determining the transmission interval and carrier/demodulation frequency of the transmitted ultrasound based on the maximum blood flow observation speed determined by the determination means; and a transmitter for transmitting the ultrasound according to the transmission interval and carrier frequency determined by the determining means and a quadrature detection circuit that performs quadrature detection of the echo reception signal using a demodulated signal having a frequency matching the demodulation frequency determined by the determining means.

[Function] The transmission interval and carrier/demodulation frequency determining means maintains the maximum blood flow observation speed as the set value based on the input signals from the sample volume input mechanism and the maximum blood flow observation speed input mechanism. The transmission interval and carrier/demodulation frequency are determined to control the transmission circuit and quadrature detection circuit, respectively.

[Embodiment] FIG. 1 is a block diagram of an ultrasonic pulsed Doppler blood flow diagnostic apparatus showing an embodiment of the present invention, (1) is a HighP
(2) is a probe that transmits an ultrasonic beam of a predetermined carrier frequency in RF mode and receives an echo signal; This is a transmitter circuit that provides signals to the child.

(3) is a receiving amplification focusing circuit that amplifies the transmitted echo signal from the probe (1) to form a receiving signal of a predetermined sound ray; (4) is a receiving amplifying focusing circuit that amplifies the received echo signal from the probe (1); The received signal strength detector detects the received signal strength of the received signal C, and sends the received signal strength signal C at the set range gate position to the transmission interval and carrier/demodulation frequency determining circuit (■0). .

(5) is a quadrature detection circuit that orthogonally detects the received and amplified signal, and its demodulation frequency is controlled by the transmission interval and demodulation frequency control signal d from the carrier/demodulation frequency determining circuit (10).

(6) is a range gate circuit that samples the orthogonally detected signal in a predetermined integration interval, and is the transmission interval.

It is controlled by the range gate signal e from the carrier/demodulation frequency determining circuit (10).

(7) is a frequency analysis circuit that spectrally analyzes the sampled signal in the integral interval, and (8) is a sample volume input mechanism through which the user sets the sample volume position.

(9) is a maximum blood flow observation speed input mechanism through which the user sets the maximum blood flow observation speed.

(10) is a transmission interval and carrier/demodulation frequency determination circuit, which includes an arithmetic unit that determines the transmission interval and carrier/demodulation frequency;
It consists of a timing generator that controls the transmission interval of the transmission carrier frequency to a predetermined period and sets timing pulses, and a carrier/demodulation frequency control circuit that sends a demodulation frequency control signal to the quadrature detection circuit. Specifically, it is composed of a microprocessor and memory, and is controlled by a program.

In the High PRF mode of the ultrasonic pulsed Doppler blood flow diagnosis apparatus configured as described above, the user inputs and sets the sample volume position at an arbitrary depth using the sample volume input mechanism (8), and sets the maximum blood flow observation speed. An arbitrary maximum blood flow observation speed is input and set using the input mechanism (9).

Based on the input information from these input mechanisms, the transmission interval and carrier/demodulation frequency determining circuit (10) determines the transmission interval, carrier frequency, and demodulation corresponding to the set maximum blood flow observation speed, as will be described in detail later. Determine the frequency.

Then, a transmission signal a and a demodulation control signal S corresponding to such transmission interval, carrier frequency, and demodulation frequency are output. The transmission interval, carrier/demodulation, and modulation frequency determination circuit (lO) is
It also outputs a range gate signal e.

The transmitting circuit (2) which receives the transmitting control signal a from the transmitting interval and carrier/demodulation frequency determining circuit (lO) sets the transmitting interval to the probe (1) at PRT and the frequency at fO. Send drive pulse.

An echo signal from the subject is received by a probe (1) and sent to a receiving amplification focusing circuit (3). The delivery amplification focus circuit (3) amplifies the echo signal and sends the received signal to the received signal strength detector (4).

The delivery signal strength detector (4) detects the received wave strength signal C at the sampled range gate position based on the range gate signal e of the transmission interval and carrier/demodulation frequency determining circuit (10).
is sent to the transmission interval and carrier/demodulation frequency determining circuit (10).

The transmission interval and carrier/demodulation frequency determination circuit (lO) performs A/D conversion on the received wave intensity signal C, performs calculations, and writes the results into memory.

When the received wave intensity signal C shows a large value, the transmission interval and carrier/demodulation frequency determination circuit (10) adjusts the transmission interval PR of the transmission carrier frequency while maintaining the maximum blood flow observation speed as the set value.
By changing T and the transmission carrier frequency fO, the received wave strength signal C
so that the value of is small.

The new PRTI and foL control signals determined in this way are sent to the wave transmitting circuit (2). The wave transmitting circuit (2) sends a driving pulse having a frequency of fol to the probe (1) with a wave sending interval of PRTl based on the signal.

The echo signal received by the probe (1) is amplified by the reception amplification focusing circuit (3) and sent to the quadrature detection circuit (5). A demodulation control signal d for controlling the demodulation frequency to foL is sent from the transmission interval and carrier/demodulation frequency determining circuit (10) to the quadrature detection circuit (5).

The orthogonal detection circuit (6) sets the demodulation frequency to fol based on the control signal of the demodulation signal d, orthogonally detects the echo signal and sends it to the range gate circuit (6).

The range gate circuit (6) is a circuit that samples the orthogonally detected signal, and samples it according to the range gate signal e from the transmission interval and carrier/demodulation frequency determination circuit (10), and sends the output signal to the frequency analysis circuit ( 7).

The frequency analysis circuit (7) spectrally analyzes the sampled signal in the integral interval and sends it to an image information processing conversion section (not shown).

Based on the setting of the sample volume position selected by the user as described above, the setting of the maximum blood flow observation speed, and the received wave intensity signal from the sample volume position, the transmission interval and carrier/demodulation frequency determining circuit (10): The wave transmission interval and carrier/demodulation frequency that do not change the maximum blood flow observation speed are calculated, and the pseudo sample volume position is removed from an inconvenient position.

Figure 2 is an image of a normal Doppler system.

A sample position at an arbitrary depth Ds shown in FIG. 2(a) and an arbitrary maximum blood flow observation velocity range -Vmax-Vmax shown in FIG. 2(b) are set by the user.

Further, FIG. 3 is a wave transmission/reception timing chart of the carrier wave fo, the received wave (received echo signal), and the range fist gate pulse to be sampled in the pulse repetition period time (PRT), that is, the wave transmission interval T, Ds and Vmax are expressed as in the following equation.

D s m C* T s / 2 vmax-IIC/4・folIT... ■C: Speed of sound Figure 4 is a wave transmission/reception timing chart in HLghPRF mode, where Vmax is changed from a small value to a large value. Conventionally, this was done by reducing the value of T, but as shown in Figure 4(a), a situation occurs where the range gate pulse collides with the next transmission pulse, so As shown in Figure 4 (b), only Td + TI had to be reduced at once, and it was not possible to achieve a Vmax value in the range corresponding to area (a) in the PRT setting area diagram in Figure 5.

To eliminate such areas where Vmax cannot be set, ■
Looking at the formula, Vmax is a function of fO-T, so
By changing the value of foc (foc carrier frequency) where the value of T cannot be taken continuously, it is possible to eliminate the region where the Vmax value cannot be set. The transmission interval and carrier/demodulation frequency determining circuit (lO) determines the transmission interval and carrier/demodulation frequency according to equation (2).

For example, if we take Figure 5 as an example, the actual PRT is (Ts+T
d/2), and the carrier wave is f o ・T / (T
s + Td/2) However, Ts-Td/2-
By varying TI≦T T s + T d /2≦T, it is possible to eliminate the unsettable area shown in FIG. 5(A).

[Effects of the Invention] As described above, according to the present invention, by controlling the pulse repetition period time and the transport/demodulation frequency, the pseudo sample volume position can be removed from an inconvenient position without changing the maximum blood flow observation speed. Therefore, any sample volume position and maximum blood flow observation speed desired by the user can be obtained.

[Brief explanation of the drawing]

Fig. 1 is a block diagram of an ultrasonic pulsed Doppler blood flow diagnostic device showing an embodiment of the present invention, Fig. 2 is an example of an image using a Doppler system, Fig. 3 is a wave transmission/reception timing chart, and Fig. 4 is a diagram of High PRF mode. A wave transmission/reception timing chart, FIG. 5 is a maximum blood flow observation speed or PRT setting area diagram, and FIG. 6 is an explanatory diagram of HighPRF. In the figure, (1) is the probe, (2) is the transmitter circuit, and (3) is the probe.
) reception amplification focusing circuit, (4) reception signal strength detector, (
5) is a quadrature detection circuit, (6) is a range gate circuit, (7
) is a frequency analysis circuit, (8) is a sample volume input mechanism, (9) is a large blood flow observation speed input mechanism, and (10) is a transmission interval and carrier/demodulation frequency determination circuit. Figure 5 Agent Patent Attorney Muneharu Sasaki

Claims (1)

[Claims] An ultrasonic pulsed Doppler blood flow diagnostic device that observes blood flow velocity using a high pulse repetition frequency mode, comprising a sample volume input mechanism that sets a sample volume position, and a maximum blood flow observation velocity. The transmission of the transmitted ultrasound is based on the maximum blood flow observation speed input mechanism to be set, the sample volume position set by the sample volume input mechanism, and the maximum blood flow observation speed set by the maximum blood flow observation speed input mechanism. a determining means for determining a wave interval and a carrier/demodulation frequency; a transmitting circuit for transmitting ultrasonic waves according to the transmitting interval and carrier frequency determined by the determining means; An ultrasonic pulse Doppler blood flow diagnostic device characterized by comprising a quadrature detection circuit that performs quadrature detection of a received echo signal using a demodulated signal having a matching frequency.