JP4463924B2 - Ultrasonic diagnostic equipment - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a CFM (Color Flow Mapping) image display method and an ultrasonic diagnostic apparatus, and more particularly to a CFM image display method and an ultrasonic diagnostic apparatus that can suitably display low-speed and low-power blood flow.
[0002]
[Prior art]
FIG. 6 is a configuration diagram illustrating an example of a conventional ultrasonic diagnostic apparatus.
The ultrasonic diagnostic apparatus 500 includes an ultrasonic probe 10, a beam former 11, a scan controller 12, a quadrature detection unit 13, an MTI (Moving Target Indication) filter 14, Autocorrelator 15, speed calculator 16, dispersion calculator 17, power calculator 18, power level detector 20, AND circuits 21 and 22, DSC (Digital Scan Converter) 23, CRT (Cathode Ray Tube) 22.
[0003]
The ultrasonic probe 10 and the beam former 11 transmit an ultrasonic pulse into the subject, receive an ultrasonic echo from the subject, and output a reception echo signal e based on the ultrasonic echo.
The scan controller 12 controls the transmission of ultrasonic pulses and the reception of ultrasonic echoes and, for example, instructs a pulse repetition frequency (PRF).
The quadrature detection unit 13 extracts I data (in-phase component) and Q data (quadrature component) of the Doppler signal from the ultrasonic echo signal e.
[0004]
The MTI filter 14 extracts only moving components from the I data and Q data.
FIG. 7 shows the pass characteristic of the MTI filter 14.
The MTI filter 14 has a pass characteristic in which a portion with a relatively low Doppler angular velocity is blocked and a portion with a relatively high frequency is passed in order to remove only the clutter component. Since this pass characteristic is defined by being normalized by the pulse repetition frequency PRF, the actual stop band becomes relatively narrow at a relatively low pulse repetition frequency PRF, and the actual stop band at a relatively high pulse repetition frequency PRF. Is relatively wide.
[0005]
The autocorrelator 15 calculates a Doppler component from the I data and Q data by autocorrelation calculation.
The speed calculator 16 calculates and outputs the speed v.
The variance calculation unit 17 calculates and outputs a velocity variance σ.
The power calculation unit 18 calculates and outputs a motion power p.
[0006]
The power level detection unit 20 compares the power p with a certain threshold th, and outputs “1” to the AND circuits 21 and 22 if the power p is equal to or greater than the certain threshold th. Is smaller than the threshold th, “0” is output to the AND circuits 21 and 22.
The AND circuit 21 passes the speed v to the DSC 23 only during a period in which “1” is input from the power level detection unit 20.
The AND circuit 22 passes the variance σ to the DSC 23 only during a period when “1” is input from the power level detection unit 20.
Thus, by removing a component having a power p smaller than the threshold th (shaded portion in FIG. 8), white noise is suppressed from appearing on the screen.
[0007]
The DSC 23 generates CFM image data based on input signals from the power calculation unit 18 and the AND circuits 21 and 22 and outputs the CFM image data to the CRT 24.
The CRT 24 displays a CFM image on a screen based on the CFM image data.
[0008]
[Problems to be solved by the invention]
FIG. 9 is an explanatory diagram showing a state in which the ultrasonic probe 10 is applied to the subject H and a blood vessel T1 through which a high-speed / high-power blood flow flows and a blood vessel T2 through which a low-speed / low-power blood flow flows are imaged. It is.
For convenience of explanation, the blood flow Vc near the center of the blood vessel T1 is high speed and large power, the blood flow Vp near the tube wall of the blood vessel T1 is medium speed and medium power, and the blood flow Vl of the blood vessel T2 is Suppose that it is low speed and small power.
As shown in FIG. 7, it is assumed that the Doppler angular frequency corresponding to the blood flow Vc is ωc, the Doppler angular frequency corresponding to the blood flow Vp is ωp, and the Doppler angular frequency corresponding to the blood flow Vl is ωl.
Further, as shown in FIG. 8, it is assumed that the power corresponding to the blood flow Vc is Pc, the power corresponding to the blood flow Vp is Pp, and the power corresponding to the blood flow Vl is Pl.
[0009]
FIG. 10 is a schematic diagram of a CFM image Gh displayed when the pulse repetition frequency is relatively high.
From the high PRF pass characteristic of the MTI filter 14 shown in FIG. 7, the high-speed / high-power blood flow Vc and the medium-speed / medium-power blood flow Vp are drawn, but the low-speed / low-power blood flow Vl is drawn. Not.
[0010]
FIG. 11 is a schematic diagram of a CFM image Gl displayed when the pulse repetition frequency is relatively low.
From the low PRF pass characteristic of the MTI filter 14 shown in FIG. 7, the high-speed / high-power blood flow Vc, the medium-speed / medium-power blood flow Vp, and the low-speed / low-power blood flow Vl are all depicted.
However, due to the movement of the tube wall, the thickness of the ultrasonic beam, and the like, a bleeding region Vm in which the motion component is depicted also appears in the region outside the blood vessel T1.
For convenience of explanation, it is assumed that the Doppler angular frequency corresponding to the bleeding region Vm is ωm as shown in FIG. Further, as shown in FIG. 8, it is assumed that the power corresponding to the bleeding region Vm is Pm.
[0011]
As described above, the conventional ultrasonic diagnostic apparatus 500 has a problem that the bleeding region Vm appears when the pulse repetition frequency is lowered in order to see the low-speed blood flow Vl.
Accordingly, an object of the present invention is to improve the CV image display method and the ultrasonic diagnosis so that the bleeding region Vm does not appear even if the pulse repetition frequency is lowered, and the low-speed and low-power blood flow can be suitably displayed. To provide an apparatus.
[0012]
[Means for Solving the Problems]
In a first aspect, the present invention transmits an ultrasonic pulse into an object, receives an ultrasonic echo from the object, extracts a Doppler signal component from a received echo signal based on the ultrasonic echo, A CFM image display method for detecting a power level based on the Doppler signal component, generating CFM data relating to a flow region having the power level equal to or greater than a threshold, and displaying a CFM image based on the CFM data, wherein a Doppler angular velocity is The threshold value in the relatively low region is substantially smaller than the threshold value in the region where the Doppler angular velocity is relatively high, and the threshold value is 2 or more in the region where the Doppler angular velocity is relatively high, and the pulse repetition frequency is lower. A CFM image display method characterized in that the threshold value is substantially increased.
In the CFM image display method according to the first aspect, the threshold value is substantially increased as the pulse repetition frequency is lower. Therefore, when the pulse repetition frequency is relatively low, the threshold value is relatively large. For this reason, when the pulse repetition frequency is relatively low, the threshold value becomes larger than the power of the bleeding area that appears outside the blood vessel wall, and CFM data corresponding to the bleeding area is not generated. Therefore, the bleeding area does not appear. On the other hand, when the Doppler angular velocity is relatively low, the threshold value is set to a relatively small value. For this reason, the threshold value is smaller than the power of the low-speed / low-power blood flow, and CFM data corresponding to the low-speed / low-power blood flow is generated. Therefore, it is possible to depict a low-speed and low-power blood flow. After all, it is possible to display a low-speed, low-power blood flow without causing the bleeding region to appear.
In the above configuration, “substantially increasing / decreasing the threshold value” means “to increase or decrease the threshold value for one power level”, for example, “the threshold value is fixed, It means that the power level may be increased or decreased.
[0013]
In a second aspect, the present invention transmits an ultrasonic pulse into a subject, receives an ultrasonic echo from within the subject, extracts a Doppler signal component from a received echo signal based on the ultrasonic echo, An ultrasonic diagnostic apparatus having a function of detecting a power level based on the Doppler signal component, generating CFM data relating to a blood flow region having the power level equal to or higher than a threshold, and displaying a CFM image based on the CFM data. The threshold value in the region where the Doppler angular velocity is relatively low is made substantially smaller than the threshold value in the region where the Doppler angular velocity is relatively high, and the threshold value is 2 or more in the region where the Doppler angular velocity is relatively high, and pulse repetition is performed. Provided is an ultrasonic diagnostic apparatus comprising threshold changing means for changing the threshold so that the lower the frequency is, the larger the threshold is substantially. That.
In the ultrasonic diagnostic apparatus according to the second aspect, the CFM image display method according to the first aspect can be suitably implemented.
[0014]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the present invention will be described in more detail with reference to embodiments shown in the drawings. Note that the present invention is not limited thereby.
FIG. 1 is a configuration diagram showing an ultrasonic diagnostic apparatus according to an embodiment of the present invention.
The ultrasonic diagnostic apparatus 100 includes an ultrasonic probe 10, a beam former 11, a scan controller 12, a quadrature detection unit 13, an MTI filter 14, an autocorrelator 15, a velocity calculation unit 16, and a variance. The calculation unit 17, power calculation unit 18, threshold generation unit 19, power level detection unit 20, AND circuits 21 and 22, DSC 23, and CRT 24 are configured.
[0015]
The ultrasonic probe 10 and the beam former 11 transmit an ultrasonic pulse into the subject, receive an ultrasonic echo from the subject, and output a reception echo signal e based on the ultrasonic echo.
The scan controller 12 controls transmission of ultrasonic pulses and reception of ultrasonic echoes, for example, instructs a pulse repetition frequency.
The quadrature detection unit 13 extracts I data (in-phase component) and Q data (quadrature component) of the Doppler signal from the ultrasonic echo signal e.
[0016]
The MTI filter 14 extracts only moving components from the I data and Q data.
FIG. 2 shows the pass characteristic of the MTI filter 14.
In order to remove only the clutter component, the MTI filter 14 has a pass characteristic that blocks a portion where the Doppler angular velocity is relatively low and allows a portion where the Doppler angular velocity is relatively high to pass. Since this pass characteristic is normalized by the pulse repetition frequency PRF, the actual stopband is relatively narrow at a relatively low pulse repetition frequency PRF, and the actual stopband is relatively low at a relatively high pulse repetition frequency PRF. Become wider.
[0017]
The autocorrelator 15 calculates a Doppler component from the I data and Q data by autocorrelation calculation.
The speed calculator 16 calculates and outputs the speed v.
The variance calculation unit 17 calculates and outputs a velocity variance σ.
The power calculation unit 18 calculates and outputs a motion power p.
[0018]
The threshold generator 19 knows the pulse repetition frequency PRF from the scan controller 12, generates a threshold Thx based on the pulse repetition frequency PRF, and passes it to the power level detector 20.
FIG. 3 illustrates the threshold value Thx (x = 1, 2, 3, 4).
The threshold values Th1, Th2, Th3, and Th4 have pulse repetition frequencies corresponding to PRF1, PRF2, PRF3, and PRF4, respectively. Here, PRF1 <PRF2 <PRF3 <PRF4.
Regarding the Doppler angular velocity, the thresholds Th1 to Th3 are relatively small values in a region where the Doppler angular velocity is relatively low, and relatively large values in a region where the Doppler angular velocity is relatively high. The threshold value Th4 is constant with respect to the Doppler angular velocity as in the prior art.
On the other hand, regarding the pulse repetition frequency PRF, in the region where the Doppler angular velocity is relatively high, the threshold values Th4, Th3, Th2, Th1 increase in the order of the pulse repetition frequencies RF4, PRF3, PRF2, PRF1. That is, when the pulse repetition frequency PRF is relatively high, the value is relatively small, and when the pulse repetition frequency is relatively low, the value is relatively large. In the region where the Doppler angular velocity is relatively low, the threshold values Th1 to Th4 are all small values.
[0019]
The power level detection unit 20 compares the power p with the threshold Thx, and outputs “1” to the AND circuits 21 and 22 if the power p is equal to or greater than the threshold Thx. If it is smaller than Thx, “0” is output to the AND circuits 21 and 22.
The AND circuit 21 passes the speed v to the DSC 23 only during a period in which “1” is input from the power level detection unit 20.
The AND circuit 22 passes the variance σ to the DSC 23 only during a period when “1” is input from the power level detection unit 20.
Thereby, at least the component with the power p smaller than the threshold value Thx is removed, thereby suppressing the appearance of white noise on the screen.
[0020]
The DSC 23 generates CFM image data based on input signals from the power calculation unit 18 and the AND circuits 21 and 22 and outputs the CFM image data to the CRT 24.
The CRT 24 displays a CFM image on a screen based on the CFM image data.
[0021]
FIG. 4 is an explanatory diagram showing a state in which the ultrasonic probe 10 is applied to the subject H and a blood vessel T1 in which a high-speed / high-power blood flow flows and a blood vessel T2 in which a low-speed / low-power blood flow flows are imaged. It is.
For convenience of explanation, the blood flow Vc near the center of the blood vessel T1 is high speed and large power, the blood flow Vp near the tube wall of the blood vessel T1 is medium speed and medium power, and the blood flow Vl of the blood vessel T2 is Suppose that it is low speed and small power.
As shown in FIG. 2, it is assumed that the Doppler angular frequency corresponding to the blood flow Vc is ωc, the Doppler angular frequency corresponding to the blood flow Vp is ωp, and the Doppler angular frequency corresponding to the blood flow Vl is ωl. Further, it is assumed that the Doppler angular frequency corresponding to the bleeding component Vm in FIG. 11 that appears in the region outside the blood vessel T1 due to the movement of the tube wall, the thickness of the ultrasonic beam, and the like is ωm.
Further, as shown in FIG. 3, it is assumed that the power corresponding to the blood flow Vc is Pc, the power corresponding to the blood flow Vp is Pp, and the power corresponding to the blood flow Vl is Pl. Further, it is assumed that the power corresponding to the bleeding region Vm is Pm.
[0022]
FIG. 5 is a schematic diagram of a CFM image Gl displayed when the pulse repetition frequency PRF2 is relatively low.
From the low PRF pass characteristic of the MTI filter 14 shown in FIG. 2 and the threshold Th2 shown in FIG. 3, the high-speed / high-power blood flow Vc, the medium-speed / medium-power blood flow Vp, and the low-speed / low-power blood flow. Since Vl passes through the MTI filter 14 and has a power level greater than the threshold value Th2, all are depicted. However, although the bleeding region Vm passes through the MTI filter 14, it is not drawn because the power level is lower than the threshold Th2. Therefore, it is possible to display the low-speed and low-power blood flow Vl so that the bleeding region Vm does not appear.
[0023]
In the ultrasonic diagnostic apparatus 100, the threshold value generation unit 19 switches the threshold value Thx according to the pulse repetition frequency PRF. However, since the threshold value is a relative value with respect to power, the pulse repetition frequency PRF and the Doppler angular velocity (or It is equivalent if the power p is increased or decreased with respect to a certain threshold according to the speed v).
That is, instead of the threshold value generating unit 19, the power level is multiplied by two or more coefficients with respect to the Doppler angular velocity, a relatively large value when the Doppler angular velocity is relatively low, and a relatively small value when the Doppler angular velocity is relatively high. At least in the region where the Doppler angular velocity is relatively high, the coefficient for multiplying the power level with respect to the pulse repetition frequency is set to two or more stages. If the pulse repetition frequency is relatively high, the coefficient is relatively large, and the pulse repetition frequency is compared. If the power level is low, a coefficient generating means for generating a coefficient having a relatively small value may be provided, and a multiplying means for multiplying the power level by the coefficient may be inserted between the power calculation section 18 and the power level detection section 20. .
[0024]
【The invention's effect】
According to the CFM image display method and ultrasonic diagnostic apparatus of the present invention, a bleeding region does not appear even if the pulse repetition frequency is lowered, so that a low-speed and low-power blood flow can be suitably displayed.
[Brief description of the drawings]
FIG. 1 is a configuration diagram showing an ultrasonic diagnostic apparatus according to an embodiment of the present invention.
FIG. 2 is a graph showing pass characteristics of an MTI filter.
FIG. 3 is an explanatory diagram of thresholds generated by a threshold generation unit.
FIG. 4 is an explanatory diagram showing a state in which blood flow in a subject is imaged.
FIG. 5 is a schematic diagram showing a CFM image at low PRF displayed by the ultrasonic diagnostic apparatus of the present invention.
FIG. 6 is a configuration diagram showing an example of a conventional ultrasonic diagnostic apparatus.
FIG. 7 is a graph showing pass characteristics of an MTI filter.
FIG. 8 is an explanatory diagram of threshold values in a conventional ultrasonic diagnostic apparatus.
FIG. 9 is an explanatory diagram showing a state in which blood flow in a subject is imaged.
FIG. 10 is a schematic diagram showing a CFM image at high PRF.
FIG. 11 is a schematic diagram showing a CFM image at low PRF displayed by a conventional ultrasonic diagnostic apparatus.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 100 Ultrasonic diagnostic apparatus 10 Ultrasonic probe 11 Beam former 12 Scan controller 13 Orthogonal detection part 14 MTI filter 15 Autocorrelator 16 Speed calculation part 17 Dispersion calculation part 18 Power calculation part 19 Threshold generation part 20 Power level detection part 21 , 22 AND circuit 23 DSC
24 CRT

Claims (2)

An ultrasonic pulse is transmitted into the subject, an ultrasonic echo is received from the subject, a Doppler signal component is extracted from a received echo signal based on the ultrasonic echo, and a power level is determined based on the Doppler signal component. An ultrasonic diagnostic apparatus having a function of detecting, generating CFM data related to a blood flow region having a power level equal to or higher than a threshold, and displaying a CFM image based on the CFM data,
The threshold value in the region where the Doppler angular velocity is relatively low is substantially smaller than the threshold value in the region where the Doppler angular velocity is relatively high, and the threshold value is 2 or more in the region where the Doppler angular velocity is relatively high, and the pulse repetition frequency An ultrasonic diagnostic apparatus comprising: a threshold value changing unit that changes the threshold value so that the lower the value is, the larger the threshold value becomes. The ultrasonic diagnostic apparatus according to claim 1,
Orthogonal detection means for orthogonal detection of the received echo signal;
An ultrasonic diagnostic apparatus comprising: a filter that allows a high-pass to the data output from the quadrature detection means, and an MTI filter that passes a high-frequency according to a pulse repetition frequency and has different Doppler angular velocities. .

Images