JPH01151444A - Ultrasonic diagnostic apparatus - Google Patents

Abstract

PURPOSE:To obtain the subject diagnostic apparatus constituted so as to obtain effective diagnostic data, by standardizing the time variation waveform of obtained Doppler deviation frequency on the basis of the time variation waveform of low frequency vibration. 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 only for a predetermined time tauw on and after mixers 9, 10 through a switch SW subjected to ON-control by an enable signal Se to detect the Doppler signal. The detected Doppler deviation frequency fd is standardized on the basis of the speed (v) of low frequency vibration by a conversion table 35 and Doppler data based thereon is displayed on a monitor.

Description

[Detailed Description of the Invention] [Objective of the Invention] (Industrial Application Field) The present invention detects characteristics related to the stiffness of biological tissue through the interaction of ultrasonic waves and low-frequency vibrations, and uses the detected characteristics as diagnostic information. The present invention relates to an ultrasonic diagnostic device.

(Prior Art) As shown in FIG. 8, 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 applies low-frequency vibrations ( fL: 100Hz
degree) to generate mechanical vibrations in this tissue P,
In this state, ultrasonic waves (f@: 3.7
5) It is known that the vibration velocity of the tissue can be detected by transmitting and receiving waves (of the order of fH2) and detecting the Doppler signal, which can be used as diagnostic information. has been done.

“5ono-Elasticity: Medical
EIasticity ImagesDerived
From tlltrasound Signals
in Mechani-cally Vibrated
Robert H.Lerner
etal, Proc, of the 16th
Acoustical ImagingSymposi
um, June 1987゜In Figure 8, if the angle between the low frequency probe 2 and the ultrasonic probe 3 as seen from the tissue P is θ°2 and the speed of vibration generated in the tissue P is V, then
The ultrasonic wave fH transmitted from the ultrasonic probe 3 toward the coarse fabric P undergoes a Doppler shift fd proportional to V cos θ due to its vibration, and is then received by the inter-probe 3.
A so-called Doppler signal can be detected. In this case, the Doppler shift fd is obtained by the following equation, as is well known.

fd= (2V cosθ) 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. 9(a) shows the amplitude waveform of mechanical vibration applied by the low frequency probe 2, and Sm indicates the maximum amplitude. In addition, Fig. 9(b) shows the velocity waveform of the (linear movement, and VM indicates the maximum velocity. Fig. 9(a), (
As is clear from b), the amplitude and velocity have a phase shift of 90''.

FIG. 7 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 tissue P 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 the 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 and 13, the high frequency component is removed, and a phase detection signal having a frequency component containing only 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 phase RAP of the subject 1 is displayed two-dimensionally, and by observing this, it can be used as diagnostic information.

FIGS. 10(a) to (C) are for calculating and outputting the Doppler signal (required data collection time + The increment width (b
) and Doppler shift frequency fd are shown in comparison. The time width τ in FIG. 10(b) can be expressed as =N·(1/fr), where fr is the repetition frequency of the ultrasonic wave, and τ is normally TL >
The relationship is set to τ. Therefore, Doppler shift frequency fd
is a value proportional to the average value of the vibration velocity V within the time width τ, and becomes a waveform that vibrates at the same frequency as the waveform in (a), as shown in (C).

(Problem to be Solved by the Invention) In this way, in conventional ultrasonic diagnostic equipment, the timing for generating low-frequency vibrations and the timing for generating ultrasonic waves are set asynchronously, so it is difficult to determine which phase of mechanical vibrations. There is a problem in that effective diagnostic information cannot be obtained because it cannot be determined whether a Doppler signal is detected. 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, it is difficult to correspond vibration velocity to luminance. If an attempt is made to display the two-dimensional velocity distribution as a two-dimensional brightness distribution, the brightness output 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 normalizes the time-varying waveform of the obtained Doppler shift frequency with the time-varying waveform of low-frequency vibration. It is characterized by:

(Function) By normalizing the time-varying waveform f(f(t)) of the Doppler shift frequency with the time-varying waveform v(t) of low-frequency vibration,
A Doppler signal is detected in the form f d(t)/v ((). This allows the Doppler signal to be detected accurately every half cycle of low-frequency vibrations, making it possible to obtain effective diagnostic information. Also, since almost the entire half cycle can be used during the Doppler signal detection period, a large number of frames can be taken, and diagnostic information can be obtained in real time.

(Example).

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, 5 is a rate pulse generator, and 6 is a Clock pulse generator.

7 is a reference signal generator, 8 is a preamplifier, 9.10 is a mixer, 11 is a 90° phase shifter, 12 and 13 are LPFs, 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 Sr, which is controlled by the clock pulse generated by the clock pulse generator 6 and generated by the rate pulse generator 5, is delayed by a delay line 25 as desired using the period Tr as the basic period as shown in FIG. 5(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 Shl is configured to scan the sector 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 value m as shown in FIG. 5(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·lr (m is an integer).

The sine wave oscillator 24 to which the STL is added generates a low frequency sine wave So with TL as one period as shown in FIG. Add. As a result, the low frequency probe 2 generates a low frequency (for example, 100 tlz) by performing mechanical vibration.
is generated and applied 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, it is controlled by a delay line 26 to have a desired delay characteristic, and then added to an adder 27.

The adder 27 is a shun switch sw that aligns the time axis of all data.
is output to mixers 9 and 1o for detecting Doppler shift.

Now, as shown in FIG. 2, there are three sets nP1. Assuming that P2 and P3 exist, when the ultrasound beam is transmitted from the ultrasound probe 3, three types of Doppler signals corresponding to each tissue PI, P2, and P3, namely Doppler shift frequencies fd1 and fd
2, fd3 is received by probe 3. At this time, the low frequency probe 2 applies the low frequency to each tissue (each Doppler shift frequency fd1, fd2 in contrast to the velocity waveform of the disturbance).
, fd3 are shown in FIG. 3 (a> to (d)).

FIG. 3 (a) shows the waveforms of fdl, (b) shows the waveforms of fd2, (C) shows the waveforms of fd3, and (d) shows the waveform of the low frequency vibration speed. fdIM.

fd2M, fd3M, and VM each indicate the maximum value.

As is clear from FIG. 3, (a
The Doppler shift frequency fd1 of ) becomes a waveform that vibrates at the same frequency as the low frequency vibration of (d).

This is considered to be because the tissue P1 responds linearly to the applied low frequency vibration, that is, the strain has a linear relationship with the stress applied to the set IP1.

(b) obtained from tissues P2 and P3 in the same manner.

(C) each Doppler shift frequency fd2. fd3 also has a waveform that vibrates at the same frequency as the low frequency vibration in (d). However, each Doppler shift frequency fd1.

fd2. The width of the vibration of fd3 is different, but this is because the width of change in vibration speed of each tissue is different.

Here, in the present invention, the waveform of the Doppler shift frequency, which reflects the vibration speed, is used as a parameter of low-frequency vibration, rather than the absolute value of the tissue vibration speed obtained for each tissue as a truly characteristic parameter of the tissue. The feature is that the information normalized by the speed waveform is displayed on the monitor. That is, fdN=fd/
Normalized Doppler information is displayed as indicated by V. Such arithmetic processing for normalization is performed by a conversion table 35 as described later. FIGS. 4(a) to (C) show waveforms obtained by normalizing the waveforms in FIGS. 3(a> to (C)) based on the above formula. As is clear from FIG. 4, V→ Each Doppler shift frequency fd1゜fd2, fd3 is normalized over almost the entire half period every half period of the velocity waveform during the period τW excluding the period O.Moreover, the normalized range is constant regardless of ■. value.

In order to obtain the information of one rask of the ultrasonic wave beam that is sector-scanned by the ultrasonic probe 3, the normalized width τ of the phase Oo of the low frequency So shown in FIG. 5(C) to 360° is used.
Assuming that data within time W is used, switch S
W 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 applied to the mixer 9.10 onwards by turning on the switch SW for the time τW during which the enable signal Se is added, and a Doppler signal is calculated.

Each output from a pair of mixers 9 and 10 is LPF12.13
．． MT I (M
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 vibration velocity. 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 normalized using the waveform So of low frequency vibration in the conversion table 35, such as fdN=fd/v. In the case of V→○, an operation such as fdN=Q is performed.

After being input to a DSG (digital scan converter), it is displayed on the monitor 22.

In this way, the time-varying waveform fd (t
) by the time-varying waveform v(t) of the low-frequency vibration, it is possible to accurately detect the Doppler signal for each half-cycle in which the phase of the low-frequency vibration is specified, so that effective diagnostic information can be obtained. (q) Moreover, almost the entire half period can be used as the period for detecting the Doppler signal.

The normalized waveform shown in FIG. 5(d) is τW (
Since it is a constant value over the period (except around V = Q),
By scanning the Doppler ultrasonic beam during this period, it is possible to collect data on a short scanning line (raster), and data within one frame can be collected in a short time. #1 in FIG. 5(d). #2. . . . indicates the timing of data collection for each scanning line, and each scanning line corresponds to each scanning line on the sector scanning pattern in FIG. 6.

Next, the operation of this embodiment will be explained.

While 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, an ultrasound beam controlled by the rate pulse 3r is transmitted from the ultrasound probe 3. The wave is transmitted to tissue P.

The ultrasound beam that has undergone a Doppler shift fd in the tissue P is received by the probe 3 and input as a signal containing a Doppler signal to a receiving circuit after the preamplifier 8. The signal output from the adder 27 is input to the mixers 9 and 10 for only a predetermined time τW via a switch SW turned on by an enable signal Se, thereby detecting a Doppler signal. By setting the time τW, the phase of the low-frequency seismic region 1 motion at which the Doppler signal is detected is specified. This makes it possible to detect a Doppler signal uniquely determined by the vibration velocity.

The Doppler shift frequency fd thus detected is normalized by the speed of low-frequency vibration by the conversion table 35, and Doppler information based on this is displayed on the monitor. In this case, since the timing at which the Doppler shift frequency is detected is set to a specific phase period normalized by the mechanical vibration, the Doppler signal does not fluctuate with the fluctuation of the mechanical vibration as in the conventional case. Therefore, accurate and effective diagnostic information can be obtained.

Furthermore, according to this embodiment, since the period for detecting the Doppler signal can be set to approximately the entire half period of low frequency vibration, it is possible to collect data within one frame in a short time. For example, the oscillation frequency fL of the low frequency probe 2 = 5QI-1z, the data collection time for one scanning line Td = 250IJsX 8 = 2
m5k: If set, TL=20, 8 within ms
If it is possible to collect scanning lines (2 m5 x 8 = 16 ms, 4 ms is the blanking period), the number of scanning lines is 128.
As a matter of fact, one frame of data can be collected in 128/8x20ms=0.32 seconds. This allows a large number of frames to be taken, making it possible to obtain diagnostic information in real time.

The vibration velocity (17) of the tissue P according to this embodiment reflects the hardness of the tissue P, so the condition of the tissue can be identified by understanding this hardness. For example, if the tissue is acoustically uniform, the entire tissue displayed on the monitor vibrates at the same speed, so Doppler information is uniformly observed. However, if there is an acoustically non-uniform area, the Doppler information will be uniformly I! Since the abnormal tissue is not detected, 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. Also, one period TL of the low frequency vibration is one period Tr 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 (TL = m・Tr) of One cycle of the rate pulse Tr can be set.

[Effects of the Invention] As described above, according to the present invention, since the waveform of the Doppler signal is normalized by the waveform of low frequency vibration,
Doppler signals can be detected accurately and effective diagnostic information can be obtained.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing an embodiment of the ultrasonic diagnostic apparatus of the present invention, FIGS. 2 and 8 are schematic diagrams explaining the present invention in detail, and FIGS. 3(a) to (d). 4(a) to (C) and FIG. 9(a>,(b) are timing charts explaining the present invention in detail, and FIG. 5(a)
) to (d) are timing charts explaining the operation of the device of this embodiment, FIG. 6 is a sector scanning pattern diagram explaining the operation of this embodiment, FIG. 7 is a block diagram of the conventional device, and FIG.
FIGS. 0(a) to 0(c) are timing charts illustrating a conventional device. 1... Subject, 2... Low frequency probe, 3... Ultrasonic probe, 5... Rate pulse generator, 24...
- Sine wave oscillator, 33... Enable signal generator, 34... fL setting device, P, Pt, P2, P3... Desired tissue of the subject, S
W...Switch, Sr...Rate pulse, Se...
・Enable signal. Agent Patent Attorney Nori Chika Kanshu
Near B Takeo-no-

Claims (2)

[Claims] (1) In an ultrasonic diagnostic device that applies low frequency vibration to a subject to vibrate the desired tissue, transmits and receives ultrasonic waves to and from this tissue, and detects the vibration speed by detecting a Doppler signal. An ultrasonic diagnostic apparatus comprising means for normalizing a time-varying waveform of a Doppler shift frequency with a time-varying waveform of a low-frequency vibration. (2) Doppler information based on the detected Doppler signal
The ultrasonic diagnostic apparatus according to claim 1, which displays the image dimensionally.