JPH0217046A - Ultrasonic doppler blood flowmeter - Google Patents

Abstract

PURPOSE:To always obtain highly accurate blood data without relying on the magnitude of velocity (v) by adjusting the magnitude of a sample volume by controlling a caliber or gate width on the basis of a cross-correlation function R(tau) so as to maximize the absolute value of saidfunction. CONSTITUTION:In an ultrasonic Doppler blood flowmeter obtaining blood flow data,an array probe is used and ultrasonic transmission-reception is performed three times at three different rates to obtain receiving echoes ei, ei+1, ei+2. From these echoes, signals vi, vi+2 (formulae II, III) after the removal of clutter determined on the basis of a range gate width are obtained. Subsequently, the cross-correlation coefficient R(tau) (formula III) between both signals vi, vi+1 is obtained and, from a value taumax of tau wherein R(tau) becomes max., blood flow velocity v=taumax.fr.c/2 (wherein fr is rate frequency and c is sonic velocity) is obtained. This flow velocity (v) is set to the mapping data on one ultrasonic raster and a series of these procedures are repeated with respect to each raster to form one frame. The caliber or range gate width of the array probe is controlled so as to make the absolute value of the aforementioned cross-correlation function R(tau) in this means max.

Description

[Detailed Description of the Invention] [Objective of the Invention] (Industrial Application Field) The present invention utilizes ultrasonic transmission/reception waves and the Dogura effect to obtain blood flow velocity information as functional information accompanying the movement of a moving object within a living body. The present invention relates to an ultrasonic Doppler blood flow meter that obtains and visualizes images, and particularly relates to an ultrasonic Doppler blood flow meter with an improved imaging method.

(Prior art) Ultrasonic diagnostic methods provide anatomical information, typically represented by B-mode images, detailed information on the movement of organs in the living body, typically represented by M-mode images, and P-mode images, typically represented by blood flow imaging. Machine #J associated with the movement of a moving object within a living body using the Dera effect! The information is used for diagnosis.

Further, typical methods for scanning inside a living body using ultrasound waves include electronic scanning and mechanical scanning. Here, the electronic scanning method will be explained.

In other words, in the case of linear electronic scanning using a play-type ultrasound probe (glove) consisting of multiple ultrasound transducers arranged side by side, a plurality of ultrasound transducers is regarded as one unit, and this one unit This is a method of transmitting an ultrasonic beam by exciting an ultrasonic transducer. For example, the pitch is sequentially shifted by l transducers and the position of one unit of element is sequentially changed. This is a scanning in which the transmitting point position of the ultrasonic beam (fit) is electronically shifted by moving the ultrasonic beam.

Then, in order to focus the ultrasonic waves as a beam, the excitation timing of the excited ultrasonic sensor is shifted between those located in the center of the beam and those located on the sides, and the resulting ultrasonic The reflected ultrasonic waves are focused (electronically focused) by using the phase difference between the sound waves generated by the sound wave sensor. Then, the reflected ultrasonic waves tIL are received by the same vibrator that was excited and converted into electrical signals, and the echo signals resulting from each transmitted and received wave are formed, for example, as a tomographic image, and the image is displayed on an anode ray tube or the like.

In addition, in the case of sector electronic scanning, for one unit of ultrasonic transducer group to be excited, each transducer is set so that the transmission direction of the ultrasonic beam changes in a J@th sector shape every one pulse of the ultrasonic beam. The excitation timing is changed according to the desired direction.The subsequent processing is basically the same as the linear electronic scanning described above.

In addition to the above-mentioned IJ near and sector electronic scanning.

There is also mechanical scanning in which a transducer (probe) is attached to a scanning mechanism and ultrasonic scanning is performed by moving the scanning mechanism.

On the other hand, in the imaging method, in addition to the B-mode image in which nine signals are combined to form a tomographic image by transmitting and receiving ultrasonic waves, an M-mode image using a set meal fixed in the same direction is typical. This M-mode image represents temporal changes in the ultrasonic wave transmitting/receiving site, and is particularly suitable for diagnosing moving organs such as the heart.

Further, the ultrasonic Dob 2 method, whose representative example is blood flow imaging, is a method of obtaining functional information associated with the movement of a moving object within a living body and visualizing it, and this will be described in detail below. In other words, the ultrasonic Doppler method utilizes the ultrasonic Doppler effect in which when ultrasound is reflected by a moving object, the frequency of the reflected wave shifts in proportion to the moving speed of the moving object. Specifically, ultrasonic wave rate (or continuous wave)
is transmitted into the living body, and from the phase change of the reflected wave echo,
By obtaining the frequency shift due to the Doppler effect, it is possible to obtain motion information of the moving object at the depth position where the echo was obtained.

According to this ultrasonic Doppler method, blood flow conditions such as the direction of the blood flow, the state of the flow (disturbed or regular), the i4 turn of the flow, the velocity value, etc. at a certain position in the living body can be determined. -Can be known.

Next, we will introduce a device that applies this ultrasonic door method (ultrasonic door 6
I will explain about the caries blood flow meter). In other words, in order to obtain blood flow information from ultrasound echoes, an ultrasound probe and a transmitter/receiver circuit are driven to transmit ultrasound pulses in a certain direction a predetermined number of times, and the received ultrasound waves are The echo is detected by a phase detector to obtain phase information or a signal consisting of a Doppler shift signal due to blood cells and a clutter component. This signal is A/D
The Doppler shift signal from the blood cells is converted into a digital signal by a converter, and the ciclutter component is removed by a filter.For example, in order to obtain a color Doppler image in real time, the Doppler shift signal is frequency-analyzed by a high-speed frequency analyzer such as an autocorrelation method. Obtain the average value of the deviation, the variance value of the Doppler deviation, the average intensity of the Doppler deviation, etc.

Here, by performing the above-described series of processes while scanning the ultrasound beam from one side to the other in correspondence with the sector scan screen, information on two-dimensionally distributed blood flow can be detected.

Then, blood flow information such as a two-dimensional blood flow velocity image showing the direction and velocity of blood flow described above, and B-mode and M-mode images obtained with another system are processed using DSC (digital scanning).・Converter) to superimpose and synthesize the images and display them on a TV monitor.

The conventional ultrasonic Doppler blood flow meter described above employs an autocorrelation method as a method of producing blood flow information. This autocorrelation method calculates the average value of the Doppler shift frequency from the phase change of ultrasound echoes, and uses the average frequency to obtain the flow velocity. However, in the case of high-speed blood flow, 'aliasing' occurs. A phenomenon occurred and it was a problem.

As a method for solving the above-mentioned interval N', that is, as a method for obtaining high-speed blood flow without aliasing, a correlation function (cross-correlation function) t- on the time axis of received echo waveforms obtained at different rates is used. The method of determining the blood flow velocity using this cross-correlation function is described in the literature (ULTRASONICIMAGING).
8, 73-85 (1986).

” TIME DOMAIN FORMULATION
OF' pULsE-DOPPLggULTRASO
LJND AND BLOOD VELOCIT
Y ESTTMATION BYCRO8SCOR
RELATIONl').

In other words, the cross-correlation method uses three different types of ultrasound transmission and reception.
By performing the received echo at the rate of ll ei
+11'i+2 is obtained, and based on these, the signal after clutter removal is obtained '11 vi+1, Vt = e, (t)+et+1(t)'t+1 =
8l-1-1(t)+-+20) Both signal ma5. Mar+1
Obtain the cross-correlation function R(τ) for , this flow velocity map is used as the mapping data on one ultrasonic rask, and one frame is formed by repeating this series of moves +1- each rask.

Furthermore, the cross-correlation type ultrasonic Doppler blood flow meter will be explained in detail. For example, a device that can measure blood flow velocity on a two-dimensional plane using a cross-correlation function and display it in color, for example, will be described.

Here, for example, the data necessary to obtain velocity data on one rask can be obtained by transmitting and receiving ultrasonic waves three different times. received echo , (t), a2(t).

・5(t), and these are subjected to signal processing as follows.

Based on the above e, (t), ez(t)-53(t), the signals after clutter removal, m(t), v2(t)ff: are obtained.

Ma, (t) = e+(t) -82<t) Ma2(t)
= ez(t) −as(t) Both signal ma, (t
), V2Ct) is calculated as follows.

Here, the flow velocity Ma is determined from the value τm□ of τ that maximizes R(τ).

Ma = τ + f l□ max r 2 (Problem to be solved by the invention) According to the above-mentioned cross-correlation type ultrasonic Doppler blood flow meter,
“It is advantageous to be able to obtain blood flow information without any loopbacks, but the measurement precision of blood flow reports is no different from the autocorrelation method, and higher precision has been strongly desired.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a cross-correlation type ultrasonic Doppler blood flow meter that can obtain highly accurate blood IL information.

"Structure of the Invention" (!!Means for Solving the Problems) The present invention has a structure in which the following means are taken to solve the above problems and achieve the objects.

That is, the present invention transmits ultrasonic waves to the blood flow in the circulatory tissue in a living body, and detects a Doppler sound component shifted by the blood flow from the echo signal obtained thereby,
In an ultrasonic Doppler blood flow meter that obtains blood flow information, a received echo ee-1 is obtained by transmitting and receiving ultrasound at three different rates using a play glove, and from these, 1'l-1111+2 Signal 11 after clutter removal determined by range ff-) width
Obtain v1+1, Ma = 6 (t) + e,, (t) Ma = e (t) + 6 + 2 (t) 1 + 1 1
+1 Obtain the cross-correlation function R(τ) between both signals 'il vi+1, and from the value of τrnax at which R(τ) is maximum, flow velocity Ma=τ ・1−! −<However, f is the rate frequency.

max r 2
rC is the speed of sound), this flow velocity M is used as mapping data on one ultrasonic raster, and this series of steps is repeated for each raster to form one frame, and the cross-correlation in this means is and means for controlling the aperture of the array rope or the range gate width so that the absolute value of aR(τ) is maximized.

(Function) According to such a configuration, Doppler signal samples can be sampled by controlling the aperture of the array probe or the range gate width. The size of the volume can be adjusted and the absolute value of the cross-correlation function can be maximized, making it possible to always obtain blood flow reports with high measurement accuracy regardless of the magnitude of blood flow velocity. .

(Example) An example of the ultrasonic Doppler blood flow needle according to the present invention will be described below.
This will be explained with reference to FIG. As shown in FIG. 1, for example, an array probe 1 for sector electronic scanning includes a rate/pulse generator 2. A preamplifier 5, which is driven to transmit with a delay ms* error generator 4 capable of controlling the aperture, and forms an ultrasonic receiving system. Delay line 6. The adder 7 enables aperture control and is driven for reception, for example,
A wave pulse toshira method scan and a B mode scan are performed. Here, in the ultrasonic/f-Russ Doppler scan, the ultrasonic transmitting system is driven at three different rates, and the ultrasonic receiving system receives the received echo J (
t), "l+1""l+2(t)" are obtained.

And the received echo by the ultrasonic i4 Lusdodera method is
A signal at a Doppler measurement point is extracted by an r-) circuit 8 having a variable range gate width, and converted into a digital signal by an A/D converter 9. This dinotal signal is sent to a switch 10.A first memory 11 consisting of three memories. an adder 12, a second memory 13 consisting of two memories; Switch J4,
FFT analyzer 15, switch 16, 8g3 memory 17 consisting of four memories. The data is input to a cross-correlation analyzer CCA K consisting of an arithmetic unit 18, which calculates the average value and variance of the blood flow velocity as mapping data (blood flow velocity r-ta) on each raster as described above, and DSC (7J digital scan converter) 19VC is applied for each time.

On the other hand, the ultrasonic transmitting system is driven by B-mode scanning such as sector scanning, and thereby the ultrasonic receiving system transfers the received echo data of the sector scanning to the B-mode image generating section 2.
Give to 0. Therefore, in general, B mode scan (root) → Doppler scan (3 different rates), l
A raster is formed, and in the DSC 19, after collecting B mode data and Doppler data for 2 minutes of N rasters,
I'm trying to create a frame image.

As described above, one frame data in the television format created by the DSCJ 9 is converted into an analog signal by the D/A converter 21, and displayed on the monitor 22 in the television format.

In the above, the diameter of the ultrasonic transmitting system and the ultrasonic receiving system is controlled by the beam controller 23, and the range gate width in the primary dart circuit 8 is controlled by the beam controller 23. And beam controller 2
3 receives control data from the arithmetic unit 1g of the cross-correlation method analyzer CCA.

This calculator 18 calculates a cross-correlation function R(τ), and this R(τ) is given to the beam controller 23. Then, the beam controller 23 performs aperture control or range gate width control so that the absolute value of R(τ) is maximized.

Figure 2 is a diagram showing the relationship between the aperture or range gate width and the Doppler signal sample size. By controlling the aperture, the azimuth width tX of the sample volume can be adjusted be able to.

Furthermore, by controlling the range r-) width, the width of the sample/IJ neem in the distance direction can be adjusted. Specifically, when the velocity V is large, the aperture is made small or the lens date is made large to make the sample volume large. Further, when the speed V is small, the aperture is made large or the range gate width is made small to make the sample volume small.

Note that the rate period is constant.

As described above, according to this embodiment, the cross-correlation function R(τ)
Based on this, aperture control or Lenz gate width control is performed so that its absolute value is maximized, so the size of the sample volume can be adjusted, and therefore the accuracy is always maintained regardless of the size of the velocity V. It becomes possible to obtain high blood flow information.

The present invention is not limited to the above embodiments, but can be implemented with various modifications without departing from the gist of the present invention.

[Effects of the Invention] As described above, according to the present invention, it is possible to provide an ultrasonic Doppler blood flow meter that can obtain highly accurate blood flow information regardless of the magnitude of V.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing the configuration of an embodiment of the ultrasonic Doppler blood flow meter according to the present invention, and FIG. 2 is a diagram showing the relationship between the aperture or range gate width and the sample volume. 1... Probe, 2... Rate noculus occurrence D, 3
delay line, 4...)9 Luther 5...preamplifier, 6...delay line, 7...adder, 8...f-) circuit, 9...A/D converter , CCA... cross-correlation method analysis section, 19... DSC (digital scan converter), 20... B-mode f-image generation section, 2...
- D/A converter, 22...monitor.

Claims (1)

[Scope of Claims] Ultrasound is transmitted to the blood flow in the circulatory tissue in the living body, and a Doppler shift component shifted by the blood flow is detected from the echo signal obtained thereby, and the blood flow is detected. In an ultrasonic Doppler blood flow meter for obtaining information, an array probe is used to transmit and receive ultrasonic waves at three different rates to obtain received echoes e_i, e_i_+_1, e_i_+_2,
From these, signals v_i, v_i_+_1 after clutter removal determined by the range gate width are obtained, and v_i=e_1(t
)+e_i_+_1(t)v_i_+_1=e_i_+
_1(t)+e_i_+_2(t) Both signals v_i, v_
Obtain the cross-correlation function R(τ) between i_+_1, ▲ There are mathematical formulas, chemical formulas, tables, etc. ▼ From the value of τ τ_m_a_x that maximizes R(τ), the flow velocity Ma = τ_m_a_x・f_r・c/2 (however, f_r
is the rate frequency and c is the sound velocity), this flow velocity v is used as mapping data on one ultrasonic raster, and this series of steps is repeated for each raster to form one frame; An ultrasonic Doppler blood flow meter comprising means for controlling the aperture of the array probe or the range gate width so that the absolute value of the cross-correlation function R(τ) is maximized.