JPH01151445A - Ultrasonic diagnostic apparatus - Google Patents

Abstract

PURPOSE:To accurately detect a Doppler signal at every cycle of low frequency vibration and to obtain effective diagnostic data, by generating low frequency vibration in synchronous relation to the generating time of an ultrasonic wave. CONSTITUTION:In such a state that the low frequency mechanical vibration generated from a low frequency probe 2 in synchronous relation to a rate pulse Sr is applied to the desired tissue P of an examinee 1, the ultrasonic beam controlled by the rate pulse Sr is transmitted to the tissue P from an ultrasonic probe 3. The ultrasonic beam receiving Doppler deviation fd by the tissue P is received by the probe 3 to be inputted to the receiving circuit on and after a preamplifier 8 as a signal containing a Doppler signal. The signal outputted from an adder 27 is inputted on and after mixers 9, 10 only for a predetermined time tauw through the switch SW subjected to ON-control by an enable signal Se to detect the Doppler signal. By setting times taud, tauw, the phase of low frequency mechanical vibration wherein the Doppler signal is detected is specified. By this method, the Doppler signal determined uniquely on the basis of a vibration speed can be detected.

Description

[Detailed Description of the Invention] [Objective of the Invention] (Industrial Application Field) The present invention detects specific loss related to the hardness of living tissue by the interaction of ultrasonic waves and low-frequency vibrations and uses it as diagnostic information. Regarding the ultrasonic diagnostic equipment to be used.

(Prior art) As shown in FIG. 4, a low-frequency probe 2 is brought into contact with the surface of a subject 1 such as a human body, and the low-frequency probe 2 mechanically performs low-frequency imaging on the tissue P within the subject 1. (fL: 100Hz
degree) to generate mechanical vibrations in this tissue P,
In this state, ultrasonic waves (f+: 3.75
It is known to detect the vibration velocity of the tissue and use it as diagnostic information by transmitting and receiving waves (on the order of MHz) and detecting Doppler signals.Such technology is described in the following literature. There is.

”5ono-Elasticity: Hedical
Elasticity ImagesDerived
From Ultrasound Signals i
n)lechani-cally Vibrated
Robert H.Lerner
etat, Proc, of the 16th
Acoustical ImagingSymposi
um, June 1987゜In Fig. 4, if the angle between the low frequency probe 2 and the ultrasonic probe 3 as seen from the tissue P is θ°1, and the speed of the vibration generated by the tissue light is ■, then
The ultrasonic wave fH transmitted from the ultrasonic probe 3 toward the set IMF undergoes a Doppler shift fd proportional to y cos θ by imaging, and is then received by the probe 3 to detect a so-called Doppler signal. be able to. In this case, the Doppler shift fd is obtained by the following equation, as is well known.

fd = (2V cos θ) fH/C However, C: Sound velocity The vibration velocity V of the tissue P can be detected based on the Doppler shift fd obtained in this way, and this vibration velocity V is the It reflects mechanical strength, that is, hardness, and by understanding this hardness, it is possible to identify whether a tissue is normal or abnormal. In other words, tissue hardness can be used as an identification parameter.

Fig. 5(a) shows the amplitude waveform of the vibration applied by the low frequency probe 2, and sm indicates the maximum amplitude. Fig. 5(b) shows the velocity waveform of the vibration. The VM shows the maximum speed in Figure 5 (a>, (
As is clear from b), the amplitude and velocity have a phase shift of 90°.

FIG. 3 is a block diagram showing the configuration of a conventional ultrasonic diagnostic apparatus, in which the low frequency fL generated by the sine wave oscillator 24 is amplified by the power amplifier 23 and then transmitted to the desired tissue of the subject via the low frequency probe 2. applied to P. The rate pulse generated by the rate pulse generator 5 controlled by the clock pulse generated by the clock pulse generator 6 is applied to the ultrasonic probe 3 via the pulser 4, and the ultrasonic probe 3 is synchronized with the rate pulse. Ultrasonic waves are transmitted to a desired phase IP of the subject 1, and reflected echo signals are received.

The echo signal is received by the ultrasound probe 3 as a Doppler signal subjected to a Doppler shift by the tissue P, converted into an electrical signal, and then applied to the preamplifier 8. preamp 8
The output signal is branched and added to a pair of mixers 9 and 10 to detect a Doppler signal (deviation).

One signal applied to mixer 9 is generated from reference signal generator 7 in synchronization with the rate pulse, multiplied by a reference signal, and then applied to LPF (low pass filter) 12. The other signal applied to the mixer 10 is 90"
The signal is multiplied by a reference signal having a phase different from the reference signal by 90' via the phase shifter 11 and then applied to the LPF 13 . By such multiplication, a frequency component containing the Doppler shift fd is obtained, and by passing it through a pair of LPFs 12.13, high frequency components are removed, and a phase detection signal having a frequency component only with the Doppler shift fd is obtained. can get. A range gate pulse for setting a tissue corresponding to an arbitrary depth of the subject 1 is outputted from the range gate circuit 14 in synchronization with the rate pulse, and a pair of sample and hold circuits 15 are outputted from the range gate circuit 14 along with the outputs of the pair of LPFs 12 and 13. .16 added.

The Doppler shift of only the desired tissue is detected by such a sample hold, and each output is passed through a BPF (bandwidth filter > 17.18 and extracted as an audio output), and is also sent to a high-speed converter via an A/D converter (19, 20). It is added to the Fourier transformer 21.

The fast Fourier transformer 21 performs frequency analysis on the digital signal and displays the result two-dimensionally on the monitor 22. As a result, the vibration velocity of the desired tissue P of the subject 1 is displayed two-dimensionally, which can be observed and used as diagnostic information.

6(a) to (C) show the speed waveform (a) of the mechanical vibration applied by the low-frequency probe 2 in order to calculate and output the Doppler signal (required data collection time This figure shows a comparison of the step width (b) of the time width τ required for the time interval (time) and the Doppler shift frequency fd. The time width τ in FIG. 6(b) can be expressed as τ=N・(1/fr), where fr is the repetition frequency of the ultrasonic wave, and if the period of the low frequency fL is '@TL, normally TL> The relationship is set to τ. Therefore, the Doppler shift frequency fd becomes a value proportional to the average value of the vibration velocity V within the time width τ, and (
The waveform shown in C) vibrates at the same frequency as the waveform in (a).

(Problem to be solved by the invention) In conventional ultrasonic diagnostic equipment, the timing of generating low-frequency vibrations and the timing of generating ultrasonic waves are set asynchronously. There is a problem in that effective diagnostic information cannot be obtained because it cannot be determined whether a Doppler signal is detected based on the phase. In other words, when displaying vibration velocity two-dimensionally based on Doppler information, if the input signal (mechanical vibration) and the output signal (Doppler signal) change at the same frequency, for example, the imaging speed may be changed to luminance. If an attempt is made to display the two-dimensional velocity distribution as a two-dimensional luminance distribution in association with each other, the output luminance will change temporally to black and white as the input changes, making it inappropriate as diagnostic information.

The present invention was made in response to the above circumstances.
It is an object of the present invention to provide an ultrasonic diagnostic apparatus configured to obtain effective diagnostic information.

[Structure of the Invention] (Means for Solving the Problems) In order to achieve the above object, the present invention is characterized in that low frequency vibrations are generated in synchronization with the generation timing of ultrasonic waves.

(Function) A low frequency j disturbance is generated from the low frequency probe in synchronization with the rate pulse that determines the repetition timing of ultrasonic wave transmission and reception. As a result, the Doppler signal can be accurately detected for each cycle of low-frequency vibration, so that effective diagnostic information can be obtained.

(Embodiment) Fig. 1 is a block diagram showing an embodiment of the ultrasonic diagnostic apparatus of the present invention, in which 1 is a subject, 2 is a low frequency probe, 3 is an ultrasonic probe, 4 is a pulser, and 5 is a rate pulse generator. 6 is a clock pulse generator.

7 is a reference signal generator, 8 is a preamplifier, 9 and 10 are mixers, 11 is a 90" transfer device, 12.13 is an LPF, 19.
20 is an A/D converter, and 22 is a monitor.

23 is a power amplifier, and 24 is a sine wave oscillator.

The rate pulse 3r, which is controlled by the clock pulse generated by the clock pulse generator 6 and generated by the rate pulse generator 5, is delayed as desired by the delay line 25 with the period Tr as the basic period, as shown in FIG. 2(a). Ultrasonic probe 3 via pulser 4 after being controlled to have the characteristics
added to.

- For example, if an electronic sector probe is used as the ultrasound probe 3, the ultrasound beam transmitted from the ultrasound probe 5 is configured to scan sectors as shown in the figure and collect two-dimensional Doppler information. ing.

The fL setter 34, which is synchronized by the rate pulse Sr and has a value m set in advance, sets the fL setting device 34 as shown in FIG. 2(b).
A low frequency pulse STL synchronized with r is generated and applied to the sine wave oscillator 24. - For example, in the figure, one period TL of STL
is shown in an example in which TL = m·l'-r (m is an integer).

The sine wave oscillator 24 to which the STL is applied generates a low frequency sine wave So having one cycle of TL as shown in FIG. 2(C) (here, So is the same as shown in FIG. 5(b)). (This is the velocity waveform of the commotion and has a phase difference of 90” from the vibration waveform)
It is applied to the low frequency probe (plunger) 2 via the power amplifier 23.

Thereby, the low frequency probe 2 generates a low frequency (for example, 100H2) by performing mechanical vibration and applies it to the desired tissue P of the subject 1.

The Doppler signal received by the ultrasound probe 3 after receiving the Doppler shift fd in the tissue P is sent to the delay line 26 via the preamplifier 8.
Here, the signal is controlled to have the desired characteristics corresponding to the delay line 26, and then added to the adder 27. After aligning the time axes of all the data, the adder 27 outputs the data to the mixers 9 and 10 via the switch SW to detect the Doppler shift.

In order to obtain information on one rask of the ultrasonic beam that is sector-scanned by the ultrasonic probe 3, the low frequency S shown in FIG.
If we use data within a time period of a width τW delayed by a time τd from Oo among 360° from the phase Oo of o,
The switch SW is turned on for this time τW. The on/off state of this switch SW is controlled by an enable signal @Se generated from an enable signal generator 33.

The output of the adder 27 is that the enable signal @Se is “H” (H
By turning on the switch SW for the time τW to reach the iClh) level, the Doppler signal is added to the mixers 9 and 10 and thereafter, and a Doppler signal is calculated.

Each output from the pair of mixers 9 and 10 is LPFl 2,1
3. MHI ()l via A/D converter 19.20
oving Target Indicator) filters 28 and 29. This MTI filter 28
29 is for removing unnecessary reflected signals (referred to as clutter) from slow-moving objects such as the wall of the heart, which are included in the signal in addition to the imaging speed. The outputs of the MTI filters 28 and 29 are applied to an autocorrelator 30 where a two-dimensional frequency analysis is performed, and an average velocity calculating section 31 roughly calculates the average vibration velocity based on the Doppler shift fd. This average speed is input to a DSC (digital scan converter) and then displayed on the monitor 22. This can be done by, for example, displaying the fdk: based image capturing speed ■ in association with the brightness.

τd and τW can be set arbitrarily, but τW should be set in the range that includes the maximum value of the low frequency So in Figure 2 (C) from the viewpoint of S/N characteristics, that is, the range that includes the time point when the speed is maximum. It is desirable to set this. By specifying the phase of the low frequency So and always detecting the Doppler signal only from this part, a Doppler signal that is uniquely determined by the imaging speed is detected, making it possible to increase the amount of effective diagnostic information. can.

In this embodiment, the enable signal Se in FIG.
An example is shown in which data for six rates is obtained during the time τW that is on. Such data collection requires low frequency S
It is repeated at the same rate every period TL of o. For example, if it is performed for all rasters (M) of sector scanning, one frame of data will be obtained for each M.TL.

Next, the operation of this embodiment will be explained.

In a state in which low-frequency mechanical vibrations generated from the low-frequency probe 2 in synchronization with the rate pulse 3r are applied to the desired tissue P of the subject 1, the ultrasound beam controlled by the rate pulse Sr is transmitted from the ultrasound probe 3. The wave is transmitted to tissue P.

The ultrasound beam that has undergone a Doppler shift of 1"d in the tissue P is received by the probe 3 and input as a signal containing a Doppler signal to the receiving circuit after the preamplifier 8. Calculator 27
The Doppler signal is detected by inputting the signal outputted from the mixers 9 and 10 only for a predetermined time τW to the mixers 9 and 10 through the switch SW turned on by the enable signal Se. By setting the times τd and τW, the phase of the low-frequency mechanical vibration at which the Doppler signal is detected is specified. This makes it possible to detect a Doppler signal uniquely determined by the imaging speed.

The imaging speed in set IIP calculated based on the Doppler shift fd can be displayed on the monitor 22 as a two-dimensional velocity distribution as a two-dimensional brightness distribution in association with, for example, brightness. In this case, the timing at which the Doppler signal is detected is set to a specific phase of mechanical vibration, so that the Doppler signal does not fluctuate with fluctuations in mechanical imaging unlike in the prior art.

Therefore, accurate and effective diagnostic information can be obtained.

Since the turbulent velocity V of the tissue P obtained in this example reflects the hardness of the tissue P, the state of the tissue can be identified by understanding this hardness. For example, if the tissue is If it is uniform, the entire tissue displayed on the monitor will vibrate at the same speed, so the imaging speed will be uniform at I2.
be noticed. However, if there is an acoustically non-uniform portion, the imaging speed will not be observed uniformly, so it can be determined that abnormal tissue exists.

In this embodiment, the data collection period τ is determined by the enable signal.
Although W is controlled, it is also possible to perform a control method in which the transmission and reception of ultrasonic waves is stopped only for this τW. In addition, low frequency (one period TL of the commotion is one period T of the rate pulse)
In the example shown, one period Tr of the rate pulse is used as a reference to set it as an integer multiple of r (TL = m・Tr), but conversely, one period TL of the low frequency vibration is taken as a reference and 1/integer of this is used as the reference. One period of the rate pulse Tr can be set to .

[Effects of the Invention] As described above, according to the present invention, low frequency vibrations are generated in synchronization with the generation timing of ultrasonic waves, so Doppler signals can be accurately detected and effective diagnostic information can be obtained. Can be done.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing an embodiment of the ultrasonic diagnostic device of the present invention, FIGS. 2(a) to (d) are timing charts explaining the operation of the device of this embodiment, and FIG. 3 shows a conventional device. A block diagram, FIG. 4 is a schematic diagram illustrating detailed explanation of the present invention,
5 (a> and (b) are timing charts explaining the present invention in detail, and FIGS. 6 (a) to (C) are timing charts explaining the conventional apparatus. 1... Subject, 2 ...Low frequency probe, 3...Ultrasonic probe, 5...Rate pulse generator, 24...
- Sine wave generator, 33... Enable signal generator, 34... fL setting device, P... Desired tissue of subject, SW... Switch, Sr
...Rate pulse, 3e...Enable signal.

Claims (2)

[Claims] (1) In an ultrasonic diagnostic device that applies low-frequency vibrations to a subject to vibrate the desired tissue, transmits and receives ultrasound to and receives ultrasound from this tissue, and detects the vibration speed by detecting a Doppler signal, low-frequency An ultrasonic diagnostic apparatus characterized by comprising means for periodically generating vibrations at the timing of ultrasonic wave generation. (2) Doppler information based on the detected Doppler signal
The ultrasonic diagnostic apparatus according to claim 1, which displays the image dimensionally.