JP2000217825A - Ultrasound diagnostic equipment - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide noiseless B-mode images. SOLUTION: A received ultrasonic signal subjected to detection is passed through two digital IIR filters having the same arrangement. The digital IIR filters comprise respective adders 51-53, 61-63, multipliers 54, 55, 64, 65, registers 56, 66, and counters 57, 67. Feedback coefficients are used as values outputted from the counters 57, 67 and clock signals CLK (a), CLK (b) are inputted to the counters 57, 67 and counted up from the timing of ultrasonic wave ejection.

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 for obtaining an image of the inside of a human body or the like using ultrasonic waves.

[0002]

2. Description of the Related Art In a processing system for a B-mode image and an M-mode image, a dynamic filter for changing a filter characteristic of a received ultrasonic signal corresponding to one line of an ultrasonic beam in accordance with the arrival time of a reflected wave. Is used. Conventionally, an analog circuit constituted by a coil and a variable capacitance diode has been used as the dynamic filter.

[0003]

However, in a conventional dynamic filter using an analog circuit including a variable capacitance diode and the like, it is inevitable that the characteristics of the variable capacitance diode and the like vary and the frequency characteristics themselves vary. There is a problem.

[0004] In view of the above, it is an object of the present invention to provide an ultrasonic diagnostic apparatus having a dynamic filter improved so that the frequency characteristics can be easily varied without variations in the characteristics.

[0005]

In order to achieve the above object, in an ultrasonic diagnostic apparatus according to the present invention, means for transmitting / receiving an ultrasonic wave and a frequency of a received ultrasonic signal are set so that a DC has a center frequency. A digital IIR filter processing means in which a filter coefficient is changed every time according to the arrival time of a received ultrasonic signal, and a means for converting the digital data after the filter processing into a luminance signal and displaying the luminance signal. It is characterized by being provided.

[0006] The filter processing means is constituted by a digital IIR filter, and its filter coefficient is changed every moment according to the arrival time of the received ultrasonic signal. The digital IIR filter does not vary in filter characteristics and can easily change the frequency characteristics according to the filter coefficient. Therefore, optimal B-mode images and M-mode images without noise can be obtained.

[0007]

Next, embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 shows an example of a dynamic filter used in the present invention. This dynamic filter is configured as a digital IIR filter having feedforward and feedback. Here, two stages having the same configuration are provided.

FIG. 2 is a block diagram showing the entire ultrasonic diagnostic apparatus. In FIG. 2, the array type probe 11 has a number of ultrasonic transducers arranged in an array. The transmission / reception circuit 12 includes a large number of individual transmission / reception circuits connected to the individual vibrators. The transmission beamformer 13 gives a drive signal whose timing is slightly changed to each transmission / reception circuit in the transmission / reception circuit 12,
Many ultrasonic transducers of the array type probe 11 are operated by changing the timing little by little, and the ultrasonic waves generated from these are synthesized. Receive beamformer 1
Numeral 4 gives a delay time to each of the received ultrasonic signals obtained from each ultrasonic transducer of the array type probe 11, and synthesizes these signals.

The scan controller 15 controls the focus and the direction of the synthesized transmission ultrasonic wave by controlling the timing and the delay time of the driving signal, and also controls the focus and the direction of the synthesized reception ultrasonic wave obtained by the signal synthesis. The direction is set to be the same as the above-mentioned transmission ultrasonic wave. Then, control is performed on the drive timing and the delay time that determine the direction so that the combined transmitted / received ultrasonic wave to be transmitted / received one after another scans a plane.

Therefore, the array-type probe 11 is applied to a diagnosis site of a subject, a specific cross section is scanned with a synthetic ultrasonic beam, and the received signal is processed by a B-mode and M-mode processing system 16 to provide a fan. An ultrasound image (B-mode image) of the mold is obtained. This image data is sent to a DSC (Digital Scan Converter) and an image memory 20, and
It is converted to a V-video signal and sent to the display device 21. Further, Doppler processing system 17 and CFI processing system 18
Are controlled by the CPU 19.

The B-mode and M-mode processing systems 16 are configured as shown in FIG. Receive beamformer 14
(A digital signal sampled at the sampling frequency fs) is input to the mixer 31 and frequency-converted so that the frequency of the input signal has DC as a center frequency. For example, as shown in FIG. 4, the quadrature detection outputs I and Q are obtained by multiplying the cosine wave and sine wave digital data by the multipliers 41 and 42.
Digital data of cosine wave and sine wave are stored in ROM4
3 and 44, the read address is designated by the output of a depth address counter 45 that is incremented at the emission timing of the ultrasonic beam and counts up by the clock signal CLK. This changes the frequency according to the reflection position (depth) of the reflected wave,
The frequency component of the reflected wave from the deep position is made to correspond to the shift to the lower frequency side (the reflected wave from the shallow position has a higher frequency, and the deeper the position, the more the frequency shifts to the lower frequency side).

The quadrature detection outputs I and Q are filtered by passing through dynamic filters 32 and 33, converted into amplitude values by an amplitude calculator 34, and further log-compressed by a log compressor 35. This digital output is
Sent to the DSC and the image memory 20 as described above,
It is converted into a luminance signal and converted into a TV video signal, sent to the display device 21 and displayed.

As the dynamic filters 32 and 33, digital IIR filters having the configuration shown in FIG. 1 are used. In FIG. 1, adders 51, 52 and 53 and multipliers 54 and 55 are provided in the digital IIR filter of the first stage.
, A register 56, and a counter 57. The multiplier 54 is inserted in the feedback loop, and multiplies the feedback data by the output value of the counter 57.
That is, the feedback coefficient is determined by the output value of the counter 57. The feedforward coefficient is always 1.0.

The counter 57 is incremented at the timing of emission of the ultrasonic beam, and is incremented by a clock signal CLK.
Count up by (a). Therefore, the feedback coefficient increases every moment, and the frequency characteristic as a digital IIR filter changes. At the first time point, for example, as shown by the rightmost curve in FIG. 5, the low-pass filter characteristic passes through a relatively high frequency band, and then gradually shifts to the left-hand curve, and the low-pass filter characteristic has a low-pass band. .

The adder 53 and the multiplier 55 are for gain correction. The output of the adder 52 is multiplied by the output value of the counter 57 and then subtracted by the adder 53 so that the output value of the counter 57 is multiplied and fed back to subtract the value corresponding to the added value. Thus, the gain at the center is corrected, and the gain of the DC component is always kept constant.

The digital IIR filter of the second stage also has the first
Exactly like the stage, it is composed of adders 61, 62, 63, multipliers 64, 65, a register 66, and a counter 67, and inserts the multiplier 64 into a feedback loop to output feedback data and the output of the counter 67. Value and the feed forward coefficient is always 1.0
And The adder 63 and the multiplier 65 are also for gain correction.

The frequency characteristic of the second stage digital IIR filter alone is the same as that of the first stage digital IIR filter. In response to the output of the counter 67 which counts up by the clock signal CLK (b), The curve on the right side of FIG. 5 sequentially moves to the curve on the left side.

Therefore, these clock signals CLK
In the case where (a) and CLK (b) are the same, the frequency characteristic of the two-stage digital IIR filter is 2
As shown in FIG. Clock signal CLK
(A) and CLK (b) may be separated to change the overall frequency characteristics of the two-stage digital IIR filter.

Therefore, the more the reflected wave is from a deeper place, the lower the cutoff frequency of the dynamic low-pass filters 32 and 33 corresponding to the signal component shifted to the lower frequency side to remove noise. Becomes possible. Moreover, since the dynamic low-pass filters 32 and 33 are constituted by digital IIR filters as described above, there is no variation in the frequency characteristics, and it is easy to change the frequency characteristics according to the depth.

The above shows only one embodiment of the present invention, and it is a matter of course that the present invention is not intended to be limited to this description. The specific configuration and the like can be variously changed. For example, although the number of stages of the digital IIR filter is two, one stage or more stages may be used. Further, as the N-stage configuration, the number of stages can be sequentially switched from 1 to N according to the depth of the reflected wave.

[0021]

As described above, according to the ultrasonic diagnostic apparatus of the present invention, the digital IIR filter in which the filter coefficient is changed every time according to the arrival time of the received ultrasonic signal is used. , The frequency characteristics thereof can be easily changed, and optimal B-mode images and M-mode images without noise can be obtained.

[Brief description of the drawings]

FIG. 1 is a block diagram showing an example of a dynamic low-pass filter used in an embodiment of the present invention.

FIG. 2 is an exemplary block diagram showing the whole embodiment;

FIG. 3 is an exemplary block diagram showing an example of a B-mode and M-mode processing system according to the embodiment;

FIG. 4 is an exemplary block diagram showing an example of a mixer in the B-mode and M-mode processing systems according to the embodiment;

FIG. 5 is a graph showing frequency characteristics of a digital IIR filter having only one stage.

FIG. 6 is a graph showing the overall frequency characteristics of a two-stage digital IIR filter.

[Explanation of symbols]

Reference Signs List 11 array type probe 12 transmission / reception circuit 13 transmission beamformer 14 reception beamformer 15 scan controller 16 B mode and M mode processing system 17 Doppler processing system 18 CFI processing system 19 CPU 20 DSC and image memory 21 display device 31 mixer 32, 33 Dynamic Low Pass Filter 34 Amplitude Calculator 35 Log Compressor 41, 42, 54, 55, 64, 65 Multiplier 43 ROM for Cosine Wave Data 44 ROM for Sine Wave Data 45 Depth Address Counter 51-53, 61-63 Addition Container 56, 66 Register 57, 67 Counter

Continued on the front page F-term (reference) 2G047 AC13 BA03 BC05 BC13 DA01 DA05 EA00 EA10 EA12 GB02 GF00 GF17 GF18 GF22 GG01 GG09 GG11 GG17 GG21 GG35 GH07 GH13 GH14 4C301 AA02 BB23 CC02 CC04 DD02 EE11H03 H03H03H03H03H03H03J03 JB38 JB42 JB50 KK02 KK22 LL02 LL04

Claims (1)

[Claims] 1. A means for transmitting and receiving an ultrasonic wave, a means for frequency-converting a frequency of a received ultrasonic signal so that a DC becomes a center frequency, and a filter coefficient which changes every moment according to an arrival time of the received ultrasonic signal. An ultrasonic diagnostic apparatus, comprising: digital IIR filter processing means to be processed; and means for converting digital data after the filter processing into a luminance signal and displaying the luminance signal.