JP3446148B2 - Ultrasound Doppler diagnostic equipment - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention transmits and receives ultrasonic waves to and from a diagnostic region of a subject, detects a frequency signal subjected to Doppler shift due to blood flow from the obtained reflection echo signal, and detects the subject. Ultrasonic Doppler diagnostic device for measuring blood flow of
Especially for velocity measurement of blood flow where Doppler frequency changes with time
The present invention relates to an ultrasonic Doppler diagnostic apparatus capable of improving the resolution of spectrum display .

[0002]

2. Description of the Related Art In a conventional ultrasonic Doppler diagnostic apparatus of this type, as shown in FIG. 3, an ultrasonic signal acquisition system 1 and a Doppler detection system 2 orthogonally detect reflected echo signals from the blood flow of a subject. Two A / D converters 4 for digitizing the obtained complex Doppler signals 3a and 3b at a predetermined sampling period.
a and 4b, a frequency analyzer 5 that takes in the time series data from these A / D converters 4a and 4b and performs a Fourier transform, and calculates the absolute value of the Fourier transform output from this frequency analyzer 5 to calculate the power. The absolute value calculator 6 for obtaining the spectrum data and the display device 7 for converting the power spectrum data from the absolute value calculator 6 into the luminance and displaying the temporal change of the Doppler shift frequency are provided. In FIG. 3, reference numerals 8 and 9 denote memories for storing required data, and reference numeral 10 denotes a controller for controlling operation timings of the display device 7 and the memories 8 and 9.

The complex Doppler signals 3a and 3b output from the Doppler detection system 2 are digitized by the respective A / D converters 4a and 4b at a predetermined sampling period, and when the number of data points required for frequency analysis is reached. The sequence data 11a and 11b are formed and temporarily stored in the first memory 8, and the frequency analyzer 5 reads the time-series data 11a and 11b from the first memory 8 in a predetermined analysis cycle to perform Fourier transform. To do. The Fourier-transformed complex spectrum data 12a and 12b are input to the next absolute value calculator 6, the absolute value is calculated by the absolute value calculator 6, and the power spectrum data 13 is sent to the display device 7. The display device 7 displays the blood flow pattern image 14 on the screen with the horizontal axis as the analysis cycle (elapsed time), the vertical axis as the frequency (blood flow velocity), and the signal intensity as the brightness. In this way, the process of displaying the temporal change in the blood flow velocity at the diagnostic region of the subject has been performed.

At this time, the frequency of the Doppler signal 3a or 3b changes with the passage of time t, as shown in FIG. 4 (a). The code W ₁ indicates the time width of the first window for setting the data analysis points, the code W ₂ indicates the time width of the second window, and the code W ₃
Also shows the time width of the third window. Further, the power spectrum data 13 analyzed and calculated for each of the windows W ₁ , W ₂ and W ₃ is shown in FIG.
As shown in. Further, the blood flow pattern image 14 obtained by converting the power spectrum data 13 obtained as described above into luminance is as shown in FIG. Note that FIG.
FIG. 3C is an enlarged view of a portion of the blood flow pattern image 14 displayed on the screen of the display device 7 shown in FIG.

[0005]

However, in such a conventional ultrasonic Doppler diagnostic apparatus, the Doppler signal 3 is used.
All frequency components of the output data in one frequency analysis performed on a and 3b are shown in FIG. 4B within the time width of each window W ₁ , W ₂ and W ₃ shown in FIG. 4A. It was treated as the same time. As a result, the setting of the number of data analysis points for the Doppler signals 3a and 3b has a contradictory effect on the frequency resolution and the time resolution, and is thus determined by a trade-off by mutual adjustment of the two. Therefore, if an attempt is made to improve the frequency resolution and perform highly accurate measurement, the number of data analysis points, that is, the time width of the above-mentioned window, will be increased. That is, in the blood flow velocity measurement in which the Doppler frequency changes with time, the resolution of the spectrum display is lowered and the change in blood flow is not well understood.

Therefore, the present invention addresses such a problem and measures the velocity of blood flow in which the Doppler frequency changes with time.
It is an object of the present invention to provide an ultrasonic Doppler diagnostic apparatus capable of improving the resolution of spectrum display in the above.

[0007]

In order to achieve the above object, an ultrasonic Doppler diagnostic apparatus according to the present invention is a complex obtained from a reflected echo signal of a blood flow obtained by transmitting and receiving ultrasonic waves in a subject. Means for taking in a Doppler signal and performing a Fourier transform , and means for computing an absolute value of this Fourier transformed output signal to obtain power spectrum data,
An ultrasonic Doppler diagnostic apparatus comprising a display device for converting the obtained power spectrum data into luminance and displaying the temporal change of the Doppler shift frequency as a blood flow pattern image , in parallel with the absolute value calculation means. Provided above
A means for calculating the group delay amount of the frequency component of the output signal from the Fourier transform means, and a group delay amount from the group delay amount calculating means.
The power spectrum data from the absolute value calculating means is divided into a plurality in the time axis direction according to the extension amount, and the display device is provided.
And means for displaying on .

It is also possible to provide a memory for inputting the calculation results of both the absolute value calculating means and the group delay amount calculating means and storing the power spectrum data as the frequency-delay amount address.

[0009]

The ultrasonic Doppler diagnostic apparatus configured as described above uses a Fourier transform means to convert the complex Doppler signal obtained from the reflected echo signal of the blood flow obtained by transmitting and receiving ultrasonic waves into the subject. After taking in and Fourier transforming , the absolute value of this Fourier transformed output signal is calculated by the absolute value calculating means to obtain power spectrum data, which is installed in parallel with the absolute value calculating means.
From the Fourier transform means by the group delay amount calculation means
Calculates the group delay amount of the frequency component of the output signal and outputs the absolute value according to the group delay amount from the group delay amount calculating means.
Multiple power spectrum data from the stage along the time axis
And is displayed on the display device as a blood flow pattern image.
This allows the velocity of blood flow where the Doppler frequency changes with time.
To improve the resolution of the spectrum display in the frequency measurement.
You can Further, in the case where a memory for storing the calculation results of both the absolute value calculating means and the group delay amount calculating means and storing the power spectrum data as the frequency-delay amount as an address is provided, the power spectrum data is cumulatively stored in this memory. Then, the accumulated result is read and a blood flow pattern image is displayed for each frequency analysis cycle.

[0010]

Embodiments of the present invention will now be described in detail with reference to the accompanying drawings. FIG. 1 is a block diagram showing an embodiment of an ultrasonic Doppler diagnostic apparatus according to the present invention. This ultrasonic Doppler diagnostic device transmits and receives ultrasonic waves to and from a diagnostic site of a subject, detects a frequency signal that is Doppler-shifted by blood flow from the obtained reflected echo signal, and detects the blood flow of the subject. As shown in FIG. 1, the ultrasonic signal acquisition system 1
A Doppler detection system 2, A / D converters 4a and 4b, a frequency analyzer 5, an absolute value calculator 6, a display device 7, a memory 8 and a controller 10, and a group delay. It comprises a quantity calculation means 15 and a two-dimensional memory 16.

The ultrasonic signal acquisition system 1 transmits / receives ultrasonic waves to / from a diagnostic site in a subject (not shown) and receives a reflected wave from the diagnostic site to obtain an echo signal. However, it has a probe and an ultrasonic transmission / reception unit that controls the drive of this probe. Further, the Doppler detection system 2 performs quadrature detection from the reflected echo signal obtained by the ultrasonic signal acquisition system 1 for the purpose of detecting a frequency signal that has undergone Doppler shift due to blood flow, and outputs complex Doppler signals 3a and 3b. Although not shown, a demodulation circuit for extracting a Doppler shift component and a high-pass filter for extracting a complex Doppler signal are provided inside. The two A / D converters 4a and 4b digitize the complex Doppler signals 3a and 3b obtained by the Doppler detection system 2 at a predetermined sampling period, and the number of data points required for frequency analysis respectively. Time series data 11a, 11
b is output.

The frequency analyzer 5 includes time series data 11a and 11 output from the two A / D converters 4a and 4b.
It is a means for fetching b and performing a Fourier transform, and is composed of, for example, an FFT (Fast Fourier Transform), and Fourier transforms the time series data 11a, 11b to output complex spectrum data 12a, 12b. . In addition, the absolute value calculator 6 is used for the complex spectrum data 12a, 12 which has been Fourier-transformed by the frequency analyzer 5.
a means for calculating the absolute value of b, such as a ROM
It consists of a table and outputs the power spectrum data 13. Further, the display device 7 receives the power spectrum data 13 output from the absolute value calculator 6 and converts the power spectrum data 13 into luminance to display a temporal change of the Doppler shift frequency as a blood flow pattern image. On the screen, the horizontal axis represents the analysis cycle (time elapsed), the vertical axis represents the frequency (blood flow velocity), and the power of the spectrum is used as the luminance to display the blood flow pattern image 14. There is.

Then, one memory 8 has two A / Ds.
Time series data 1 digitized by the converters 4a and 4b
1a and 11b are temporarily stored. Further, the controller 10 controls the operation timings of the display device 7, the memory 8, the group delay amount calculation means 15, which will be described later, and the two-dimensional memory 16.

Here, in the present invention, the group delay amount calculating means 15 is provided in parallel with the absolute value calculating device 6, and the absolute value calculating device 6 and the group delay amount calculating means 15 are provided.
A two-dimensional memory 16 is provided on the output side of. The group delay amount calculation means 15 calculates the phase angle data with respect to the frequency of the Fourier transform output (12a, 12b) from the frequency analyzer 5 and calculates the group delay amount by calculating the difference for each frequency of the phase angle data. The complex spectrum data 12 output from the frequency analyzer 5
The phase angle calculator 17 including a ROM table for inputting a and 12b and calculating the phase angle data (vector angle and direction) by the arctan function, and the output data from the phase angle calculator 17 are temporarily held. A subtracter 1 for calculating a difference between adjacent frequencies between the latch 18 and the phase angle data directly input from the phase angle calculator 17 and the phase angle data temporarily held in the latch 18 and input with a delay.
9 and an adder 20 that adds the output from the subtractor 19 to calculate the group delay amount of the frequency component. That
Then, the controller 10 controls the group delay amount calculation means 1
The power from the absolute value calculator 6 according to the group delay amount from 5
Spectral data is divided and displayed in the time axis direction
It is adapted to be displayed on the device 7.

The two-dimensional memory 16 receives the calculation results of both the absolute value calculator 6 and the group delay amount calculating means 15 and stores the power spectrum data 13 as a frequency-delay amount address. The delay amount as is the value obtained by dividing the frequency analysis period by the sampling period of the analysis data, that is, the amount corresponding to the shift amount of the time-series data between the frequency analysis cycles is shifted every time, and the data is accumulated and stored. ing.

Next, the operation of the ultrasonic Doppler diagnostic apparatus thus constructed will be described. In FIG. 1, the operation up to the frequency analyzer 5 is exactly the same as that of the conventional example shown in FIG. 3, and therefore its explanation is omitted. The frequency analyzer 5
Fourier transform of complex spectrum data 1
2a and 12b are input to the absolute value calculator 6 and the phase angle calculator 17 in the group delay amount calculator 15, respectively. Then, the absolute value calculator 6 calculates the absolute value of the input complex spectrum data 12a, 12b and sends it to the two-dimensional memory 16 as the power spectrum data 13. Further, the phase angle calculator 17 calculates the frequency series data of the phase angle (vector angle, direction) for the input complex spectrum data 12a, 12b by the arctan function and sends it to the latch 18 and the subtractor 19. Then, the subtractor 19 calculates the difference between adjacent frequencies between the phase angle data directly input from the phase angle calculator 17 and the phase angle data temporarily held in the latch 18 and delayed. Then, this is used as the data 21 of the group delay amount in the analysis cycle. Thereafter, the adder 20 adds the group delay amount data 21 sequentially output from the subtractor 19 and the time 23 of the analysis cycle output from the controller 10 to calculate the delay amount 22 of the frequency component.

After that, the power spectrum data 13 thus obtained and the delay amount 22 are used to store the power spectrum data 13 in the two-dimensional memory 16 with the frequency-delay amount as an address. At this time, the time as the address of the two-dimensional memory 16 is a value obtained by dividing the frequency analysis cycle of the frequency analyzer 5 by the sampling cycle of the analysis data, that is, the amount corresponding to the shift amount of the time series data between the frequency analysis cycles. Is to be shifted every time. Then, the cumulative result is read from the two-dimensional memory 16 in which the power spectrum data 13 is cumulatively stored in this way, and the read data is sent to the display device 7 for each frequency analysis cycle, and the blood flow pattern image 14 is obtained. Is displayed.

The Doppler signal 3a or 3b at this time is as shown in FIG. 2 (a) as in the conventional example. In addition, with respect to the Doppler signal 3a or 3b shown in FIG.
Each window for setting the number of data analysis points W ₁ , W ₂ , W
_As shown in FIG. 2B, the power spectrum data 13 calculated by analyzing and calculating ₃ is displayed in each window W ₁ ,
Divide W ₂ and W ₃ into multiple, for example, four time zones,
In that, the group delay amount of the output is calculated, and the delay amount is divided into, for example, four and analyzed. Then, using the analysis data obtained by analyzing the delay amount, the context of time t'in one window is selected, and the block-shaped power spectrum data 13 is obtained, for example, divided into four in the time direction. . Further, the blood flow pattern image 14 obtained by converting the power spectrum data 13 obtained as described above into luminance is as shown in FIG. This and
Under the control of the controller 10, the group delay amount calculation means
According to the group delay amount from 15, the power from the absolute value calculator 6
-Split the spectrum data into multiple parts along the time axis
It is displayed on the display device 7.

FIG. 2C shows the display device 7 shown in FIG.
2 is an enlarged view of a portion of the blood flow pattern image 14 displayed on the screen surrounded by a circle A. As shown in FIG. 2B, the time in each window W ₁ , W ₂ , W ₃ is changed. For example, the block-shaped power spectrum data 13 divided in four in the t ′ direction is combined with the power spectrum data of the latter two power spectrum data in the previous window and the power spectrum data of the first two power windows in the next window to obtain one. The blood flow pattern image 14 is divided into, for example, two passages of time in the window.
Are displayed respectively. That is,
As shown in FIG. 2B, within the time width of each window W ₁ , W ₂ , and W ₃ shown in FIG. Can be prevented.

In FIG. 2 (b), the block-shaped power spectrum data 13 divided into, for example, four in the time t'direction in each of the windows W ₁ , W ₂ , W ₃ is shown. However, the present invention is not limited to this, and may be divided into another plurality in the time direction. Also, FIG.
In (c), the time lapse in one window is shown as being divided into, for example, two, and the blood flow pattern images 14 are respectively displayed, but the present invention is not limited to this, and the time lapse is divided into another plurality. It may be displayed. Further, the function calculation and address operation in the group delay amount calculating means 15 shown in FIG. 1 and the cumulative addition of data in the two-dimensional memory 16 may be implemented by software by using a DSP or the like. The two-dimensional memory 16 shown in FIG. 1 may be omitted, and the output signals from the absolute value calculator 6 and the group delay amount calculator 15 may be directly input to the display device 7.

[0021]

Since the present invention is constructed as described above,
The complex Doppler signal obtained from the reflected echo signal of the blood flow obtained by transmitting and receiving ultrasonic waves in the subject is taken into the Fourier transform means and Fourier transformed, and the absolute value of the output value of this Fourier transformed is calculated as the absolute value. Means to obtain power spectrum data, and install it in parallel with the absolute value calculation means.
Output from the Fourier transforming means by the group delay amount calculating means.
The group delay amount of the frequency component of the force signal is calculated, and the absolute value calculation means is operated according to the group delay amount from the group delay amount calculation means.
These power spectrum data are divided into multiple in the time axis direction.
It can be divided and displayed as a blood flow pattern image on the display device. Thus, increasing the time width of the data analysis points i.e. window as attempt to highly accurate measurement to improve the frequency resolution, to prevent the deterioration of the time resolution, the Doppler frequency is time varying It is possible to improve the resolution of the spectrum display in the blood flow velocity measurement, and to better understand the changes in blood flow. Further, by providing both the calculation results of the absolute value calculation means and the group delay amount calculation means and storing the power spectrum data as the frequency-delay amount address, the power spectrum data is cumulatively stored in this memory. The accumulated result can be read and the blood flow pattern image can be displayed for each frequency analysis cycle.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of an ultrasonic Doppler diagnostic apparatus according to the present invention.

FIG. 2 is a graph for explaining the operation of the ultrasonic Doppler diagnostic apparatus.

FIG. 3 is a block diagram showing a conventional ultrasonic Doppler diagnostic apparatus.

FIG. 4 is a graph for explaining the operation of the conventional ultrasonic Doppler diagnostic apparatus.

[Explanation of symbols]

1 ... Ultrasonic signal acquisition system 2 ... Doppler detection system 4a, 4b ... A / D converter 5 ... Frequency analyzer 6 ... Absolute value calculator 7 ... Display device 8 ... Memory 10 ... Controller 14 ... Blood flow pattern image 15 ... Group delay amount calculation means 16 ... Two-dimensional memory

Continuation of front page (58) Fields surveyed (Int.Cl. ⁷ , DB name) A61B 8/00

Claims (2)

(57) [Claims] 1. A means for fetching a complex Doppler signal obtained from a reflection echo signal of a blood flow obtained by transmitting and receiving ultrasonic waves in a subject and performing a Fourier transform , and an absolute value of an output signal obtained by the Fourier transform. It is provided with an absolute value calculation means for performing calculation to obtain power spectrum data, and a display device for converting the obtained power spectrum data into luminance and displaying the temporal change of the Doppler shift frequency as a blood flow pattern image. In the ultrasonic Doppler diagnostic apparatus, the Fourier transform is provided in parallel with the absolute value calculation means.
Means for calculating the group delay amount of the frequency component of the output signal from the means, and the group delay amount from the group delay amount calculating means
Power spectrum data from the above absolute value calculation means
Display on the above display device by dividing it into multiple pieces in the time axis direction
An ultrasonic Doppler diagnostic apparatus comprising: 2. A memory for inputting the calculation results of both the absolute value calculating means and the group delay amount calculating means and storing the power spectrum data as a frequency-delay amount address. Ultrasonic Doppler diagnostic device.