JPH09131343A - Ultrasonic diagnostic device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To allow quick signal processing without using a high-speed processing filter circuit and reduce the cost by converting the ultrasonic reception signal into the base band complex signal by orthogonal detection processing, processing it with a complex filter, and changing the filter characteristic of the complex filter along the time series. SOLUTION: This ultrasonic diagnostic device is provided with a dynamic filter 5 applying filter processing to the ultrasonic reception signal received by a transmitting/receiving circuit and A/D-converted by an A/D converter 4 and extracting only the signal in the required band. The output signal of the filter 5 is fed to a digital scan converter via a logarithmic amplifier 6 and a rectifying circuit 7. The dynamic filter 5 is provided with an orthogonal detecting circuit 10 applying orthogonal detection to the reception signal after A/D conversion and generating base-band complex signals I, Q, applies complex filter processing to the complex signals I, Q with the complex filter 11, and changes the filter characteristic of the complex filter 11 along the time series.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ultrasonic diagnostic apparatus, and more particularly to a dynamic filter function of the ultrasonic diagnostic apparatus.

[0002]

2. Description of the Related Art Generally, an ultrasonic signal obtained by an ultrasonic diagnostic apparatus is characterized in that the deeper the diagnostic portion (the farther it is from the ultrasonic probe) is, the higher the frequency is attenuated and the more the amplitude is attenuated. is there. Therefore, in the ultrasonic diagnostic apparatus, as a filter that extracts only a signal having a required bandwidth from the ultrasonic received signal, the filter characteristics, that is, the center frequency and the bandwidth of the signal pass band are dynamically changed in time series. A filter was used.

As such a dynamic filter, conventionally, there has been an RC type analog dynamic filter 50 shown in FIG. The analog dynamic filter 50 changes the filter characteristic by changing the resistance value of the variable resistor 51 forming the filter in time series.

However, with the recent digitalization of signals, instead of analog dynamic filters,
The digital dynamic filter 60 shown in FIG. 8 is used. This digital dynamic filter 60 is F
An IR (non-recursive) digital filter, which is an A / D
Converted the received ultrasound signals with delays in each delay element 61 _{1 to n,} coefficients in the coefficient multipliers 62 _{0 to n-1} to the outputs of the front and rear of each of the delay elements ₆₁ 1~n K 0~n- By multiplying by ₁ and summing the outputs of the respective stages obtained in this way by the adder 63, only the signal of the required bandwidth is taken out from the ultrasonic wave received signal. Coefficient multiplier 62 0 to _n-1
By _{varying the} coefficients K 0 to _{n-1 given} to the time series, the filter characteristics are changed according to the depth of the diagnosis region.

[0005]

However, in the ultrasonic diagnostic apparatus equipped with such a digital dynamic filter 60, the band of the ultrasonic received signal is 2-9M.
In order to filter an ultrasonic signal in a high frequency band such as Hz within such a high frequency band within a predetermined period, it is necessary to configure a dynamic filter with a digital filter circuit capable of high speed processing. However, the digital dynamic filter capable of high-speed processing is expensive, and this causes the cost of the ultrasonic diagnostic apparatus to increase.

Therefore, in the present invention, it is an object of the present invention to simplify the circuit configuration by enabling signal processing without using a filter circuit capable of high-speed processing, thereby providing an ultrasonic diagnostic apparatus at low cost. There is.

[0007]

In order to achieve such a subject, in the present invention, a quadrature detecting means for converting an ultrasonic received signal into a baseband complex signal by a quadrature detecting process, and the quadrature detecting means. The ultrasonic diagnostic apparatus is configured to include complex filter means for performing a complex filter process on the baseband complex signal converted by the above, and filter characteristic changing means for varying the filter characteristic of the complex filter means in time series.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below in detail with reference to the drawings.

FIG. 1 is a block diagram showing the overall configuration of an ultrasonic diagnostic apparatus according to an embodiment of the present invention.
FIG. 3 is a block diagram showing a configuration of a dynamic filter which is a main part thereof.

This ultrasonic diagnostic apparatus 1 includes an ultrasonic probe 2
A transmitting / receiving circuit 3 for transmitting and receiving ultrasonic waves by the ultrasonic probe 2, an A / D converter 4 for A / D converting the ultrasonic wave reception signal received by the transmitting / receiving circuit 3, and an A / D Dynamic filter 5 that filters the converted ultrasonic wave reception signal and extracts only the signal in the required band
And the output of the dynamic filter 5 by logarithmic amplification
A logarithmic amplifier 6 for og compression, a rectifying circuit 7 for rectifying and detecting the output of the logarithmic amplifier 6, a low-pass filter 8 for removing high frequency noise from the output of the rectifying circuit 7, and an ultrasonic wave reception signal which is polar coordinate data are orthogonalized. It is provided with a DSC (digital scan converter) 9 which converts the coordinate data, stores the display data at an address corresponding to the orthogonal coordinate data, and then transmits the display data to a display device (not shown).

The ultrasonic diagnostic apparatus 1 is characterized by the structure of the dynamic filter 5 in the structure described above. That is, the dynamic filter 5 is, as shown in FIG.
Quadrature detection circuit 10 that performs quadrature detection on the A / D-converted ultrasonic wave reception signal to generate baseband complex signals I and Q, and performs complex filter processing on the baseband complex signals I and Q. Complex filter 11 and complex filter 1
The filter characteristic changing unit 12 changes the filter characteristic of No. 1 in time series.

The quadrature detection circuit 10 includes a phase detection section 13A,
13B and low pass filters 14A and 14B. The phase detectors 13A and 13B multiply the A / D-converted ultrasonic wave reception signal by a cos reference phase signal and a sin reference phase signal to obtain a baseband complex signal that is a ± frequency signal centered on DC. I and Q are created. The low-pass filters 14A and 14B remove harmonics of the baseband complex signals I and Q. Further, the low-pass filters 14A and 14B also perform decimation to reduce the sample rate.

The complex filter 11 filters the baseband complex signals I and Q created by the quadrature detection circuit 10 to extract only signals in a required band. Since Q is a ± frequency signal centered on DC, a digital filter such as a real number type filter can perform only similar-shaped filter processing centered on DC as shown in FIG. However,
The baseband complex signals I and Q created by the quadrature detection circuit 10 do not necessarily have similar frequency characteristics centered on DC. Therefore, in the dynamic filter 5, a filter circuit is configured by the complex filter 11 that performs the complex filtering process, so that the center position of the frequency characteristic can be determined as shown in FIG.
It is possible to shift from DC as shown in FIG.

The complex filter 11 is constructed, for example, as shown in FIG. FIG. 5 shows a configuration of an N-stage complex filter, which has reference numerals 20a _{1 to N} , 20b _{1 to N} ,
c _{1 to N} and 20d _{1 to N} are arranged in multiple _stages to form the complex filter 11
21a 0 to _N , 21b 0 to _N , 2
1c 0 to _N and 21d 0 to _N are coefficient multipliers, and 22a and 22a
b, 22c, 22d and 23a, 23b are adders.

Next, the structure of the filter characteristic changing means 12 will be described with reference to FIGS. FIG. 6 is an enlarged view of part A of FIG. The filter characteristic changing unit 12 includes a look-up table-shaped coefficient memories 24a to 24d and a coefficient storage unit 2.
5a 0 to _N , 25b 0 to _N , 25c 0 to _N , 25d ₀ to _N. In the coefficient memories 24a to 24d, a parameter f ₀ that determines the center frequency of the signal pass band in the complex filter 11 corresponding to the passage of time with the ultrasonic wave transmission / reception timing as a reference point, and the time with the ultrasonic wave transmission / reception timing as a reference point. The parameter Bw that determines the bandwidth of the signal pass band in the complex filter 11 corresponding to the progress is called from the main body side of the ultrasonic diagnostic apparatus 1. Further, in the coefficient memories 24a to 24d, a correspondence table between the parameter f ₀ and the center frequency of the signal pass band in the complex filter 11, and a correspondence between the parameter Bw and the bandwidth of the signal pass band in the complex filter 11 are described. The table is stored in advance, and the coefficients for defining the center frequency and the bandwidth of the signal pass band, that is, the filter coefficient data stored in the address position designated by the called parameters f ₀ and Bw, are stored in the coefficient storage unit 25a.
_0~N, 25b _0~N, 25c _0~N, and outputs it to the 25d _0~N.

Coefficient storage units 25a 0 to _N , 25b 0 to _N , 25
c 0 to _N and 25d 0 to _N are a pair of registers 26a and 26b.
And stores the filter coefficient data output from the coefficient memories 24a to 24d to store the filter coefficient data in each coefficient multiplier 2
1a 0 to _N , 21b 0 to _N , 21c 0 to _N , 21d 0 to _N are used for calculation.

The filter characteristic changing means 12 configured as described above operates as follows. That is, the coefficient memory 2
4a to 24d call parameters f ₀ and Bw according to the passage of time with the ultrasonic wave transmission / reception timing as a reference point from the main body side of the ultrasonic diagnostic apparatus 1. These parameters f
₀ and Bw change with the lapse of time, and in the coefficient memories 24a to 24d, the input parameters f ₀ and Bw are input.
The filter coefficient data stored in the address specified by the coefficient multiplier 21a 0 to _N , 21b 0 to _N , 21
It outputs to _{c0- N} and _{21d0- N} , and thereby the complex filter 11 is changing the center frequency and bandwidth of a signal pass band. The fluctuations of the center frequency and the bandwidth of the signal pass band are set so that the output of the complex filter 11 is not affected by the attenuation of the ultrasonic wave on the high frequency side and the attenuation by the depth of the diagnostic region.

The coefficient storage units 25a 0 to _N , 25
b 0 to _N , 25c 0 to _N , 25d 0 to _N are coefficient multipliers 21a 0 to _N , 21b 0 to _N , 21c 0 to _N , 21d as _follows .
The filter coefficient data of 0 to _N is switched. That is, each coefficient multiplier 21 is based on the filter coefficient data stored in one register 26a (26b).
_{a 0~N, 21b 0 ~N, 21c} 0~N, while performing the calculation of the coefficient multiplication 21d _{0 to N,} the other register 26b (2
6a), the following filter coefficient data is read from the coefficient memories 24a to 24d and written. Then, such arithmetic processing and writing processing are performed by the registers 26a, 2
The filter coefficient can be changed by alternating between 6b.

Next, the operation of the dynamic filter 5 thus constructed will be described. That is, the received ultrasonic wave received signal is A / D converted by the A / D converter 4 and then input to the phase detection units 13A and 13B, respectively. In the phase detectors 13A and 13B, the input digital ultrasonic wave reception signal is multiplied by the cos reference phase signal or the sin reference phase signal to create the baseband complex signals I and Q, and the low pass filter 14A, Output to 14B. The low-pass filters 14A and 14B remove harmonics of the input baseband complex signals I and Q, and then output them to the complex filter 11. The complex filter 11 performs complex filter processing on the input baseband complex signals I and Q to extract only a signal in a required band and output it to the logarithmic amplifier 6.

Since the complex filter 11 filters a signal in a relatively low frequency range of ± frequency signals centered on DC, it is not necessary to perform such high-speed signal processing. Therefore, even if the complex filter 11 is configured by a filter circuit for low speed processing, which has a relatively simple structure, the filter processing can be performed within a predetermined period.

While the complex filter 11 performs the complex filter processing as described above, the filter characteristic changing means 12 sets the parameter f ₀ for determining the center frequency of the signal pass band and the parameter Bw for determining the bandwidth of the signal pass band. Based on this, the filter coefficient of the complex filter 11 is changed with time. Therefore, the complex filter 11 filters the baseband complex signals I and Q in a state in which the center frequency and the bandwidth of the signal pass band are cyclically changed according to the variation of the filter coefficient. As a result, the complex filter 11 acts as a dynamic filter, and performs the filtering process of the baseband complex signals I and Q without being affected by the attenuation of the high frequency side and the attenuation of the amplitude due to the difference in the depth of the diagnosis region. .

Note that by calculating √ (I ² + Q ² ) in the rectifier circuit 7 based on the baseband complex signals I and Q log-compressed by the logarithmic amplifier 6, the same luminance signal as before can be obtained. Will be created.

By the way, in the present embodiment, the quadrature detection circuit 1 receives the ultrasonic wave received signal A / D converted by the A / D converter 4.
Although the quadrature detection was performed at 0 to generate the baseband complex signals I and Q, in addition to this, the quadrature detection circuit 10 detects the ultrasonic reception signal.
Alternatively, the quadrature detection may be performed and then A / D conversion may be performed.

Further, in the present embodiment, the complex filter 1
Baseband complex signals I and Q subjected to complex filtering by 1
Was log-compressed by the logarithmic amplifier 6 and then rectified and detected by the rectifier circuit 7. In addition, the baseband complex signals I and Q complex-filtered by the complex filter 11 were rectified and detected by the rectifier circuit 7 and then logarithmized. The amplifier 6 may perform log compression.

Further, in this ultrasonic diagnostic apparatus 1, since the quadrature detection circuit 10 creates the baseband complex signals I and Q, the baseband complex signals I and Q are used as they are as Doppler signals. Ultrasonic diagnostic device 1
Can be easily diverted as an ultrasonic Doppler device.

[0026]

As described above, according to the present invention, since the ultrasonic wave reception signal is converted into a signal in a relatively low frequency range of ± frequency signals centered on DC, the filtering process is performed.
Even if a complex filter is configured with a relatively simple filter circuit for low-speed processing, filter processing can be performed. Therefore, the structure of the filter is simplified and the cost is reduced.

Further, by converting the ultrasonic wave received signal into a ± frequency signal centered on DC by the quadrature detection means,
In the circuit at the latter stage, signal processing has become possible with the same sampling frequency. Therefore, even when using an ultrasonic probe with different transmission / reception timing intervals, in the circuit in the subsequent stage, it becomes possible to perform signal processing with the same sampling frequency. Clock control has become simple and cost reduction has been achieved.

[Brief description of the drawings]

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

FIG. 2 is a block diagram showing a configuration of a dynamic filter which is a main part of the ultrasonic diagnostic apparatus according to the embodiment.

FIG. 3 is a diagram showing an example of filter characteristics of a real number type filter.

FIG. 4 is a diagram showing an example of filter characteristics of a complex filter.

FIG. 5 is a block diagram showing a configuration of a complex filter that constitutes an embodiment.

FIG. 6 is an enlarged view of a portion A in FIG. 5;

FIG. 7 is a circuit diagram showing a configuration of an analog dynamic filter incorporated in an ultrasonic diagnostic apparatus.

FIG. 8 is a block diagram showing a configuration of a conventional digital dynamic filter incorporated in an ultrasonic diagnostic apparatus.

[Explanation of symbols]

 10 quadrature detection circuit 11 complex filter 12 filter characteristic changing means I, Q baseband complex signal

Claims (1)

[Claims] 1. A quadrature detection means for converting an ultrasonic received signal into a baseband complex signal by quadrature detection processing, a complex filter means for performing complex filter processing on the baseband complex signal converted by the quadrature detection means, and An ultrasonic diagnostic apparatus comprising: a filter characteristic changing unit that changes the filter characteristic of the complex filter unit in time series.