JP3420110B2 - Ultrasound diagnostic equipment - Google Patents

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 technique for dynamically controlling the characteristics of a reception filter according to the reception depth.

[0002]

2. Description of the Related Art The attenuation rate of ultrasonic waves in a living body increases as the frequency increases. Therefore, when a wideband ultrasonic pulse is propagated in the living body, the spectrum of the ultrasonic wave differs between a shallow portion and a deep portion as seen from the probe. For this reason, in the ultrasonic diagnostic apparatus, in order to cut the frequency band of noise as appropriately as possible, conventionally, control is performed to dynamically change the characteristics of the reception filter according to the depth of the echo reception target point. For example, it is known that the center frequency of the reception signal at each reception depth draws a curve as shown in FIG. 4, and the characteristics of the reception filter are controlled so as to change along this curve.

In recent ultrasonic diagnostic apparatuses, digitalization of signal processing has progressed, and digital filters of FIR (non-recursive) type or the like have come to be used as a reception filter. As is well known, the filter characteristics of digital filters are
It is determined by the set of filter coefficients for each tap. In the case of controlling the characteristics of such a digital reception filter according to the reception depth, conventionally, the control is performed such that the filter characteristics are switched at predetermined intervals. Actually, assuming that the propagation speed of the sound wave in the living body is almost constant, the filter characteristics are switched at regular time intervals.

Specifically, in the conventional ultrasonic diagnostic apparatus,
For example, a set of filter coefficients at a switching timing at fixed time intervals is sequentially stored in a memory, and at each switching timing, a set of filter coefficients corresponding to the timing is read from the memory and set in a reception filter. Had a composition. In this configuration, the memory stores the filter characteristic (set of filter coefficients) at each switching timing. By using this memory as the RAM and allowing the set of filter characteristics stored in the memory to be exchanged, the filter characteristic can be changed. It is also performed to be able to switch in various patterns.

Since it takes several tens of clocks to set the coefficient to the receiving filter, depending on the number of taps of the filter, the conventional filter characteristic switching interval is set to be at least longer than the time required for setting the coefficient. It had been.

[0006]

In the conventional filter characteristic switching method described above, a steep range (intermediate depth range: FIG. 4) is obtained even in a range where the change of the filter characteristic is gradual (shallow and deep: see FIG. 4). However, the switching intervals of the filter characteristics were the same. Therefore, in the range where the change is sharp, the switching width of the filter characteristic per one time becomes larger than in the range where the change is gentle. Become more noticeable. To avoid this, the switching interval may be shortened to such an extent that the switching width of the filter characteristics does not cause a noticeable step in the image quality even in the sharp change range. However, there is a problem that when the switching timing comes, it is not necessary to change the filter characteristic, but wasteful operations such as setting the same filter characteristic again occur.

Further, the above conventional filter characteristic switching system is
Since the filter characteristic can be switched only at regular time intervals, there is a problem that it is impossible to finely control the switching timing. This will be described with reference to FIG.

In FIG. 5, a graph 100 is a part of the curve shown in FIG. 4, in which the vertical axis represents the center frequency and the horizontal axis represents the depth (time). Point ti on the horizontal axis (i = 1, 2, ...
() Indicates the switching timing for switching the filter characteristic, and the dot 102 indicated by a black circle indicates the set value of the filter characteristic (center frequency characteristic) set at each switching timing. As shown, the switching timing is at regular intervals. The graph 105 shows the change in the value of the filter characteristic realized by the filter setting at such constant intervals. Since the filter characteristic is selected and set from a finite characteristic value prepared in advance, it changes discretely. In this way, since the filter characteristic switching is performed at regular intervals, the obtained filter characteristic (graph 105)
Is the ideal filter characteristic (ie the characteristic of the received signal:
There is a case where the distance from the graph 100) greatly deviates (for example, timing t9). In order to get closer to the graph 100, for example, the filter characteristics may be switched at timings s1 and s2. However, since the conventional filter characteristic switching mechanism is configured to switch the filter characteristics at regular intervals, It was not possible to switch at any time.

As described above, in the conventional apparatus, since the degree of freedom in setting the filter switching timing is extremely small, the approximation of the filter characteristic to the ideal curve of FIG. 4 may be insufficient.

In order to avoid such a problem, it suffices to make the switching interval itself sufficiently short, but as described above, it takes some time to set the coefficient in the filter, and the switching interval is set to be shorter than this time. It couldn't be shortened. Therefore, in the conventional method, the problem of the degree of approximation of the filter characteristic to the ideal curve is a problem that is difficult to avoid.

The present invention has been made in order to solve such a problem, and it is an object of the present invention to provide an ultrasonic diagnostic apparatus capable of increasing the degree of freedom of the switching timing of the characteristics of the reception filter and realizing fine characteristic switching. To aim.

[0012]

In order to achieve the above object, an ultrasonic diagnostic apparatus according to the present invention comprises a reception filter for filtering an ultrasonic reception signal, and one or more defining a filter characteristic of the reception filter. Filter characteristic information,
A characteristic information registration unit that is registered so that it can be read according to the order applied to the reception filter, and the characteristic information registration
A timing information registration unit that registers, for each filter characteristic registered in the unit, information that defines timing corresponding to the reception depth at which the filter characteristic is applied to the reception filter; and the timing information registration unit. A switching timing instructing section for outputting a switching timing signal instructing a timing corresponding to a reception depth at which the filter characteristics are sequentially switched according to the information registered in, and the characteristic information in accordance with the switching timing signal. It is characterized by further comprising: a characteristic switching unit for sequentially reading the filter characteristic information from the registration unit and switching the filter characteristic of the reception filter according to the filter characteristic information.

In this configuration, a timing information registration unit is provided for each filter characteristic, in which information defining the timing for applying the characteristic to the reception filter is registered, and the switching timing signal generated based on the information registered in this is provided. The filter characteristic is switched accordingly. According to this configuration, the timing for switching the filter characteristics can be defined for each individual filter characteristic, so that it is possible to set flexible switching timing according to the ideal characteristic change, rather than the conventional switching at constant intervals. Becomes

In this configuration, for example, as the information registered in the timing information registration section, a switching interval for switching from each filter characteristic to the next filter characteristic can be used.

In this case, the timing information registration section is
A random access memory for storing the switching intervals,
Means for writing each switching interval selected by the user in the random access memory in an address order according to the application order, and the switching timing instructing section sets the switching interval and counts the system clock to set the switching interval. A counter that outputs the switching timing signal when the preset switching interval is reached, and a data output address of the random access memory is incremented by one data when the switching timing signal is output, and the information of the next switching interval is counted by the counter. And means for setting to.

In the present invention, the filter characteristics to be switched include the center frequency of the pass band of the reception filter,
For example, the pass band width of the reception filter.

[0017]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention (hereinafter referred to as embodiments) will be described below with reference to the drawings.

FIG. 1 is a diagram showing a main part of a receiving circuit system of an ultrasonic diagnostic apparatus according to the present invention. In FIG. 1, a transducer array 20 includes a plurality of ultrasonic transducers, transmits ultrasonic waves according to a drive signal from a transmission circuit system (not shown), receives echoes of the transmitted ultrasonic waves, and outputs the ultrasonic waves. Convert to an electrical received signal. The reception signal of each transducer of the transducer array 20 is amplified by the preamplifier 30, and the phasing addition unit 40
Entered in. The phasing addition unit 40 is a circuit for forming a reception beam, converts a reception signal of each transducer into a digital signal, adds a predetermined delay to each signal, adds the signals, and outputs the addition result. . The phasing-added received signal is filtered by a variable BPF (band pass filter) 50 to remove unnecessary frequency components.

This variable BPF 50 is FIR (non-cyclic).
Type digital filter, various filter characteristics can be obtained by changing the setting of the filter coefficient (multiplication coefficient) of each tap. The filter characteristics include the center frequency and bandwidth of the pass band, and these characteristics can be changed with a high degree of freedom depending on how the filter coefficient of each tap is set. The filter control unit 10 is means for controlling the filter characteristics of the variable BPF 50, that is, setting / changing the filter coefficient of each tap.

The signal in the required band extracted by the variable BPF 50 in this manner is subjected to signal processing (eg, autocorrelation calculation in the case of Doppler tomography) in the signal processing system 60 according to the display purpose. Then, the signal processing result is written in a DSC (digital scan converter) 70, scan-converted into the coordinate system of the display device, and then output to the display circuit.

In such an ultrasonic diagnostic apparatus, the filter control unit 10 executes dynamic filter characteristic control according to the reception depth. FIG. 2 is a diagram showing an internal configuration of the filter control unit 10.

In FIG. 2, the coefficient data memory 122
Is a memory in which definition information fi (i = 0, 1, 2, ..., N) of all filter characteristics usable in this apparatus is stored. The definition information fi of the filter characteristic is a variable BP
This is information that defines the filter characteristic of the F50, and is specifically a set of filter coefficient values of each tap of the variable BPF 50. For example, when the number of taps of the variable BPF 50 is 10,
Each definition information fi is a set of 10 filter coefficients. The coefficient data memory 122 may be a ROM (Read Only Memory).

The switching interval memory 110 corresponds to the timing information registration section in the claims. Switching interval memory 1
10, the filter characteristic switching interval ei (i = 0, 1,
2, ...) are stored by addressing according to the output order. The switching interval ei is equal to the system clock (CL
K) as a unit, and is represented as integer value data of about 1 byte or 2 bytes. The switching interval memory 110 is a RAM (random access memory), and the stored data of the switching interval ei can be rewritten if necessary.

The characteristic designation information memory 120 corresponds to the characteristic information registration section in the claims. In the characteristic designation information memory 120, characteristic designation information a (fi) for instructing the filter characteristic used at the echo reception from the shallowest portion to the deepest portion in one beam is stored by addressing according to the output order. That is, the characteristic designation information memory 120
Is the filter characteristic definition information f0 to fn registered in the coefficient data memory 122, which is used at the time of reception.
They are stored in the order in which they are used. However, the characteristic designation information a (fi) stored in the characteristic designation information memory 120
Is not the definition information fi (that is, a set of filter coefficients) itself but information such as an address indicating the definition information fi in the coefficient data memory 122. The characteristic designation information memory 120 is a RAM (random access memory), and the stored data of the characteristic designation information a (fi) can be rewritten as necessary.

The filter characteristic of the variable BPF 50 is the characteristic designation information a (fi) stored in the characteristic designation information memory 120.
Can be switched in this order. In the illustrated example, the filter characteristic is f
It will be switched in the order of 2, f5, f8, .... In the illustrated example, the time interval from the start of reception with the filter characteristic f2 to the switching to f5 is e0, the time interval from the switching from f5 to f8 is e1, and so on.

The switching interval memory 110 outputs the switching interval ei corresponding to the address input to the address terminal (adrs) from the output terminal (data out). The output value ei is input to the data input terminal (data) of the down counter 112.

The down counter 112 outputs the output value ei
When the loading of is completed, this value is used as the initial value and down-counting starts immediately. That is, down counter 1
A system clock (CLK; for example, about 20 to 40 MHz) 12 is input to a clock input terminal (clk), and counts down by 1 for each clock. When the count value reaches 0, the down counter 112 outputs a carry out signal from the carry terminal (carry out). This carry-out signal becomes a switching timing signal indicating the switching timing of the filter characteristic. This switching timing signal is applied to the delay device 11
4, supplied to the up counters 116 and 118.

Upon receiving the switching timing signal from the clock input terminal (clk), the up counter 116 increments the internal count value by a unit amount and outputs the result from the output terminal (out). This counter 11
The count value of 6 is the switching interval e of the switching interval memory 110.
It indicates the address of i, and the output of the counter 116 indicates the next switching interval ei due to the increase of this count value. This output is input to the address terminal of the switching interval memory 110, whereby the data of the next switching interval is output from the data output terminal of the switching interval memory 110 and loaded into the down counter 112.
With such a mechanism, when the switching timing signal is issued, the data of the next switching interval is loaded into the down counter 112, and the next down counting process is performed. By repeating this, the switching interval memory 11
The switching intervals ei stored in 0 are sequentially loaded into the down counter 112 in the order of addresses, and the down counter 112 outputs a switching timing signal every time the switching intervals are counted.

After the down counter 112 outputs the switching timing signal from the carry terminal, until the next switching interval data is supplied to the data input terminal (out), the up counter 116 and the switching interval memory 110.
There is a delay corresponding to the operating time of. To compensate for this,
The switching timing signal is delayed by the delay by the delay device 114 and supplied to the load enable terminal (load) of the down counter 112. As a result, the data of the next switching interval output from the switching interval memory 110 is correctly loaded into the down counter 112. As the delay device 114, a D flip prop having a system clock (CLK) as a clock input can be used.

The up counter 118 receives the switching timing signal output from the down counter 112 at the clock input terminal (clk). When the switching timing signal is input, the up counter 118 increments the internal count value by a unit amount and outputs the result from the output terminal (out). The count value of the up counter 118 is the characteristic designation information a of the characteristic designation information memory 120.
The address of (fi) is shown, and the output of the counter 118 points to the next characteristic designation information as the count value increases. This output is the characteristic designation information memory 120.
Is input to the address terminal (adrs).

The characteristic designation information memory 120 outputs the characteristic designation information a (fi) corresponding to the value input to the address terminal from the data output terminal (data out). This output is the address terminal (ad
rs). The coefficient data memory 122 outputs characteristic information fi (that is, a coefficient set) corresponding to the characteristic designation information a (fi) input to the address terminal from the data output unit (data out). The output of the coefficient data memory 122 is input to the variable BPF 50, and the coefficient of each tap of the variable BPF 50 is set according to this output.

The variable BPF 50 has two latches for holding the coefficient group (filter characteristic) of each tap, and while performing the filter processing using the coefficient group held in one latch, another variable The following coefficient group is set for one latch, and this is alternately repeated.
A switching timing signal is supplied from the down counter 112 to the variable BPF 50 for switching the coefficient group.

The change in the signal of each part of the circuit configuration of FIG. 2 described above is as shown in the timing chart of FIG. As shown in FIG. 3, the filtering process with the filter characteristic f2 continues for the period of the switching interval e0, and during this period, the coefficient data of the next filter characteristic f5 is set in the latch of the variable BPF 50. Then, when the period e0 elapses from the start of the processing with the filter characteristic f2, the down counter 11
A switching timing signal is output from 2, and the filter characteristic of the variable BPF 50 is switched to f5 in response to this.
Thereafter, by repeating the same operation, the filter characteristics fi are switched in the order designated by the characteristic designation information memory 120 for each switching interval ei stored in the switching interval memory 110.

As described above, in the present embodiment, by setting the series of the switching intervals ei in the switching interval memory 110, the intervals of each switching timing can be basically set freely. That is, each switching interval can be basically set to an arbitrary value with the system clock (CLK) as a unit. Therefore, in the ideal curve as shown in FIG. 4, it is possible to lengthen the switching interval of the filter characteristic in the portion where the change of the filter characteristic is gentle and shorten the switching interval of the filter characteristic in the portion where the change of the filter characteristic is abrupt.
Therefore, it is possible to increase the number of times of switching at the portion where the filter characteristics change abruptly without increasing the number of times of switching the filter characteristics as a whole, and it is possible to finely switch the filter characteristics in that portion, and reduce the difference in image quality due to the characteristics switching. You can

Further, according to the present embodiment, the switching timing of the filter characteristic can be freely determined in the system clock (CLK) unit, so that the filter characteristic can be finely switched in accordance with the ideal curve of FIG. Become.
That is, in this embodiment, the timing s shown in FIG.
Since 1 or s2 can be used as a switching timing ((s2-s1) can be set as a switching interval in the memory 110), the characteristic can be switched only at the timing ti at regular intervals. It is possible to switch characteristics that are closer to the ideal curve than the conventional method.

As can be seen from FIG. 5, conventionally,
Even if the filter characteristics are the same, it is necessary to specify the filter characteristics for each timing ti, but in the present embodiment, the filter characteristics need to be specified only when the filter characteristics are actually changed, so there is no waste. . Therefore, the capacity of the characteristic designation information memory 120 can be saved.

In the present embodiment, the switching interval memory 110 and the characteristic designation information memory 120 are composed of RAM, and the stored contents can be rewritten. Ultrasonic diagnostic equipment
Equipped with multiple filter characteristic switching patterns (Fig. 4). That is, the ultrasonic diagnostic apparatus, for each of the plurality of switching patterns, the series of the switching intervals ei and the characteristic designation information a.
A pair with the series of (f) is held. Then, at the time of diagnosis, the switching interval of the switching pattern selected by the user and the series of the characteristic designation information are set in the switching interval memory 110 and the characteristic designation information memory 120, respectively, and the above-described switching processing is performed. With such a configuration, it becomes possible to switch the filter characteristics in various patterns. Note that FIG. 4 and FIG.
Although the change of the center frequency is shown in the above, it is of course possible to change the pass band width of the variable BPF 50 in the present embodiment.

[0038]

As described above, according to the present invention,
It is possible to flexibly set the switching timing according to the ideal change in the filter characteristics, rather than the conventional switching at regular intervals, and it is possible to improve the image quality of the ultrasonic image.

[Brief description of drawings]

FIG. 1 is a diagram showing a main part of a receiving circuit system of an ultrasonic diagnostic apparatus according to the present invention.

FIG. 2 is a diagram showing an internal configuration of a filter control unit.

FIG. 3 is a timing chart schematically showing changes in signals of respective parts of the filter control unit.

FIG. 4 is a diagram showing a relationship between a reception depth and a center frequency of a reception signal.

FIG. 5 is a diagram for explaining the problems of the conventional filter characteristic switching method and the advantages of the method of the present embodiment.

[Explanation of symbols]

10 filter control unit, 20 transducer array, 30 preamplifier, 40 phasing addition unit, 50 variable BPF (band pass filter), 60 signal processing system, 70 DS
C (digital scan converter), 110 switching interval memory, 112 down counter, 114 delay device, 11
6, 118 up counter, 120 characteristic specification information memory, 122 coefficient data memory.

Claims (5)

(57) [Claims] 1. A reception filter for filtering an ultrasonic reception signal, and one or more filter characteristic information defining filter characteristics of the reception filter, which are registered so that they can be read out in an order of application to the reception filter. An information registration unit, for each filter characteristic registered in the characteristic information registration unit ,
Reception depth at which the filter characteristics are applied to the reception filter
According to the information registered in the timing information registration unit that registers information that defines the timing corresponding to the
A switching timing instructing unit that outputs a switching timing signal instructing a timing corresponding to the reception depth for sequentially switching the filter characteristics, and filter characteristic information in order from the characteristic information registration unit according to the switching timing signal. An ultrasonic diagnostic apparatus comprising: a characteristic switching unit for reading and switching the filter characteristic of the reception filter according to the filter characteristic information. 2. The ultrasonic diagnostic apparatus according to claim 1, wherein the information registered in the timing information registration unit is a switching interval for switching from each filter characteristic to the next filter characteristic. Diagnostic device. 3. The ultrasonic diagnostic apparatus according to claim 2, wherein the timing information registration unit sets the random access memory for storing the switching intervals and the switching intervals selected by the user according to the application order. Writing means to the random access memory in an address order, the switching timing instructing section sets a switching interval, counts a system clock, and outputs the switching timing signal when the set switching interval is reached. A counter, and means for incrementing the data output address of the random access memory by one data when the switching timing signal is output and setting information on the next switching interval in the counter. Sound wave diagnostic equipment. 4. The ultrasonic diagnostic apparatus according to any one of claims 1 to 3, wherein the filter characteristic includes a center frequency of a pass band of a reception filter. 5. The ultrasonic diagnostic apparatus according to any one of claims 1 to 4, wherein the filter characteristic includes a pass band width of a reception filter.