JPS59168845A - Ultrasonic transmitting and receiving system in ultrasonic imaging apparatus - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an ultrasound transmission/reception method in an ultrasound imaging device.

Conventionally, so-called electronic focusing has been widely used, which focuses an ultrasonic beam transmitted and received from a linear array transducer to improve the resolution in the azimuth direction with respect to a target area. Furthermore, there is also a variable focus type electronic focusing system in which the beam focal point is changed depending on the exploration depth.

On the other hand, when broadband transmission is performed, it is known that the center frequency of the reflected wave from the target area decreases depending on the depth. A so-called variable filter method that attempts to receive only the target reflected wave through a bandpass filter whose passband width is changed is also often used.

Such a variable focus and variable filter method may be employed simultaneously. However, in variable focus, even if the focal point (focal point) is swept, it only changes the distribution state of the delay map that determines the timing of oscillator activation, and the frequency characteristics of the delay map itself still remain broadband. Therefore, the variable focus and variable filter were each implemented in separate circuits.

In view of these points, the purpose of the present invention is to organically perform variable focus and variable filtering, and also to adopt a variable filter method during wave transmission, so as to transmit and receive ultrasonic waves with different frequencies depending on the depth. The object of the present invention is to provide a variable focus/variable filter type transmitting/receiving system that makes it possible to

The present invention will be described in detail below using the drawings. First, the principle of transmitting waves will be described. As shown in Fig. 1, the small coefficient pulse from the pulser PL is band-divided into high, middle, and low frequencies by bandpass filters BPF1 to BPF3, and then delay maps DM1 to DM3 (low and The sound waves in the area are transmitted through a delay distribution that focuses them far away. In this case, the depth of focus and the division band can be determined to be different λ. The outputs from the delay map are added by corresponding adders DD1 to ADD5, and then linear amplifiers 1 to
A5 amplifies each signal and applies it to the play oscillators TD-TD5.

As a result, the play vibrator is energized three times, and the low frequency (f3) sound wave generated by driving with a low frequency signal is focused far away, and the sound wave generated by driving with a medium frequency signal is focused far away. A sound wave with a frequency (f2) of about 100 m is focused at an intermediate depth, and a sound wave with a high frequency (f, ) generated by driving with a high frequency signal is focused at a short distance.

FIG. 2 is a configuration diagram showing an embodiment based on the above principle.
The output from the pulser PL is passed through a chirp filter,
It is configured to be applied to a linear amplifier that energizes the array transducer. A chirp filter CF-CF is configured so that the frequency of the input signal becomes low and the delay time of the delayed output becomes long. A combination of a delay line and a summing amplifier that combines the outputs of each point is used.

In each chirp filter, the rate of change in delay amount with respect to frequency is the strongest in chirp filter CF1,
CF2. It becomes weaker in the order of CF3. Note that the degree of CF may be set to zero. However, it only has a delay function so that electronic focus is not impaired.

With this configuration, when a broadband small signal pulse enters from the freezer PL, the chirp filter allows the lower frequency signal to reach the outer transducers more slowly.P, the transducer array The ultrasonic beams projected are those with a high frequency (fl) at a shallow area, those with an intermediate frequency (f2) at a medium depth, and those at a low frequency (f3).
Each one focuses on a deep part.

In this case, the output of the pulser PL may be a signal with a waveform as shown in FIG. 5 whose frequency is divided into high (fH), medium (fM), and low (fL).

The chap filter is a tapped chirp filter as shown in Fig. 4, and the signal is extracted from an appropriate tap (for example, one in which the relationship between the tap distance and the frequency versus delay is proportional) and the signal is extracted from the amplifier "A3" and "A2". It may also be possible to lead to

Next, the case of wave reception will be described. In the embodiment shown in FIG. 5, the reflected wave signals received by the transducers TD1 to TD5 and converted into electrical signals are sent to the adder ADD41 for the signals from the outer and intermediate transducers. A
DDl. After addition by chirp filter CF, 1.
The signal from the center vibrator is guided directly to chirp filter CF13. The rate of change in delay amount with respect to the frequency of these chirp filters is set so that CFll is the largest and CF13 is the smallest, and the higher the frequency of the reflected wave signal passing through the filter, the greater the curvature of the delay map. The system is structured like this. The output of each chirp filter is sent to an adder ADD.

The signals are synthesized by a variable bandpass filter BPF11, frequency-selected by a variable bandpass filter BPF11, and sent to a processing circuit (not shown).

Variable band pass filter BPF1. is a time-frequency control signal (TFC), which is a voltage signal that changes over time.
), and here the passband is configured to be able to change from a high range to a low range with elapsed time, based on the time relationship at the time of wave transmission. be.

As a result, after receiving a reflected wave signal of a high frequency from a shallow area, the reflected wave signal of a lower frequency from a deeper area is successively received.

Note that the number of transducer elements and the number of chirp filters are not limited to those in the embodiment.

In addition, the transducer array is a switched linear scan type,
Other types of arrays are also possible.

Furthermore, it is also possible to adopt a transmission/reception method in which the frequency is selected according to the depth only when receiving waves, and not when transmitting waves.

As described above, according to the present invention, it is possible to organically perform variable focus and variable filtering in a simple manner, and at the same time explore a target area with ultrasonic waves with different frequencies depending on the depth. A sound wave transmission/reception method can be realized.

Further, in the present invention, since the frequency of the ultrasonic wave is varied depending on the depth not only in reception but also in transmission, there is an effect that the S/N of the echo signal is significantly improved.

[Brief explanation of the drawing]

FIG. 1 is a detailed explanation diagram of the present invention, FIG. 2 is a configuration diagram of an embodiment of the present invention during wave transmission, FIG. 3 is a waveform showing an example of an energizing signal, and FIG. 4 is a diagram of the present invention. FIG. 5 is a block diagram of another embodiment of the present invention relating to wave transmission, and FIG. 5 is a block diagram of one embodiment of the present invention relating to wave reception. TD1 to TD5... Vibration element, PL-... Pulsar,
CF, CFl. CF2. CF3. CFll, CF12. C
F13-=chirp filter, BPFll... variable breadth pass filter.

Claims (4)

[Claims] (1) In an ultrasound imaging device that uses play transducers to transmit and receive ultrasound, multiple transducers are to be energized at the same time, so that the outer ones have a larger delay with respect to lower frequencies. After passing through a filter means configured to, the reflected wave signal is received via a variable bandpass filter whose pass band changes with elapsed time, and the reflected wave signal is received with a different frequency depending on the depth. An ultrasonic transmission/reception method in an ultrasonic imaging device, characterized in that: (2) The ultrasonic imaging apparatus according to claim 1, wherein the filter means is constituted by a chirp filter. Ultrasonic transmission and reception method. (3) In an ultrasound imaging device that uses play transducers to transmit and receive ultrasound, when transmitting multiple transducers that must be energized at the same time, the outer ones have a greater delay with respect to lower frequencies. An energizing signal is applied through a transmitting filter means configured so that, at the time of reception, a receiving filter means configured such that the outer side has a larger delay with respect to the lower frequency used wave number. The reflected wave signal is received via a variable bandpass filter whose pass band changes with the elapsed time after passing through the vessel, and the reflected wave signal is received at a different frequency depending on the depth. Ultrasonic transmission and reception method in ultrasound imaging equipment. (4) The ultrasonic transmitting and receiving system in an ultrasonic imaging apparatus according to claim 6, wherein the transmitting filter means and the receiving filter means are constituted by chirp filters.