JPH09122127A - Ultrasonic diagnostic device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To plot the blood flow information of a weaker and finer blood vessel by reducing the influence of a signal processing means provided with a narrow dynamic range such as an A/D converter or the like in a color flow ultrasonic diagnostic device. SOLUTION: In this ultrasonic diagnostic device for processing ultrasonic wave signals from the inside of a living body, demodulating the modulation of ultrasonic waves by a flood flow, A/D converting the demodulation signals, operating a blood flow speed, distribution and power, etc., and plotting the blood flow information inside the body, a means 25 for compressing signals is provided in the prestage of a means 21 for demodulating the signals or an A/D conversion means 22. Also, a means 26 for expanding the signals after conversion is provided which expands the signals before sending them to an arithmetic part 24 and after the compressed signals are A/D converted. By using the signals after expansion from which unrequired fixed part signals are removed in an MTI filter 23, the arithmetic part 24 operates the blood flow information and color-displays the arithmetic result.

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 an ultrasonic diagnostic apparatus having a Doppler signal processing function suitable for ultrasonic color Doppler diagnosis.

[0002]

2. Description of the Related Art In an ultrasonic diagnostic apparatus, a two-dimensional blood flow color drawing function called color flow mapping is capable of drawing the running state of blood vessels in real time using the Doppler effect. It is widely used in Japan.

In the two-dimensional blood flow color drawing function, the running state of the blood flow is expressed depending on whether the flow direction of the blood flow is closer to or farther from the probe. Red and blue hues are added.
Further, the power of the blood flow velocity information is displayed to show the distribution state of blood vessels in the organ.

In the ultrasonic diagnostic apparatus having such a two-dimensional blood flow color drawing function, as shown in FIG.
In order to calculate blood flow information such as blood flow velocity, dispersion, and power in addition to a system for detecting the signal received by the device and sending it to the video processing circuit 42 and the scan converter 43 as a B mode signal or an M mode signal. It is equipped with a signal processing system. This signal processing system mainly includes a quadrature demodulator 44 that mixes an ultrasonic signal with two reference frequency signals having phases different from each other by 90 degrees and demodulates the same, and an A / D converter 45 that digitizes the demodulated complex signal. An MTI filter 46 for removing unnecessary fixed reflection signals from the heart wall and the like, and a computing unit 47 for computing the velocity, dispersion, power, etc. of the blood flow by the autocorrelation method or the like.

In such an ultrasonic diagnostic apparatus, the ultrasonic signal received by the receiving circuit is ultrasonic waved in the phasing circuit 41 depending on whether the probe 40 is a single element or an array type probe. Processing for deflecting / focusing the beam is executed, and the signal sent to the scan converter 43 as a B-mode signal is subjected to processing such as logarithmic compression and γ correction in accordance with the dynamic range and brightness characteristics of the display 49. On the other hand, the output of the phasing circuit 41 is mixed and demodulated with the reference frequency signal, and then each complex signal is digitized, and the MTI filter 46 is output.
After the fixed component is removed by, the calculation such as taking the arctangent of the ratio of the real part and the imaginary part is performed. The calculation result in the calculation unit 47 is given a hue by the direction of blood flow in the color processing unit 48 and a color tone according to the power thereof, and is displayed on the display 49 together with the B mode signal or individually.

An ultrasonic diagnostic apparatus has also been developed in which the output of the phasing circuit is digitized and signal processing for color Doppler (demodulation, calculation for blood flow visualization, etc.) is performed by a DSP (digital signal processor). .

[0007]

By the way, the purpose of the two-dimensional blood flow color drawing function is to know the running state of blood vessels and to identify the presence / absence / distribution status of fine blood vessels.
A Doppler signal to be displayed as a color drawing function must handle a signal of 100 dB from a large amount of tissue motion to a small amount of peripheral blood vessels, but in the prior art, dynamics of elements in quadrature demodulation or A / D conversion are used. It was difficult to visualize even minute blood vessels due to lack of range.

For example, an A / D converter for digitizing a demodulated signal for speed / power calculation by digital processing is
At most 10-14 bits, its input dynamic range is only about 60-84 dB. Therefore, it has been difficult to draw blood flow information requiring a wide dynamic range as described above in the entire visual field like the kidney.

Therefore, an object of the present invention is to effectively expand the dynamic range of the signal processing means when it has to pass through the signal processing means having a narrow dynamic range in the color Doppler signal processing so that the blood flow in a wide range. It is to provide an ultrasonic diagnostic apparatus having a function of displaying information in two-dimensional color.

[0010]

The ultrasonic diagnostic apparatus of the present invention which achieves the above-mentioned object, includes a receiving means for receiving a blood flow signal from a living body and converting it into an electric signal, and a Doppler signal processing of the received signal. In an ultrasonic diagnostic apparatus including signal processing means, means for calculating blood flow information using the processed signal, and means for displaying the calculation result, the signal processing means is a demodulator for demodulating at least a received signal. Means and an A / D conversion means, further, a means for compressing the signal is provided in a stage before the demodulation means or the A / D conversion means, and a means for expanding the compressed signal is provided in a stage before the arithmetic means. It is a thing.

Here, the signal processing means demodulates the received signal and then performs A / D conversion, that is, even if the signal processing is performed in the order of the demodulation means and the A / D conversion means, the received signal is digitally processed. It may be demodulated and then demodulated, and in any case, the compression means is provided before either the demodulation means or the A / D conversion means. The compression means reduces the dynamic range of the received signal to the narrower dynamic range of either the demodulation means or the A / D conversion means.

On the other hand, the expansion means expands the received signal after demodulation and A / D conversion to the original dynamic range and sends it to the arithmetic means. The computing means processes the expanded dynamic range signal. As a result, a blood flow signal having a wide dynamic range of 100 dB can be processed without being restricted to a relatively narrow dynamic range of an A / D converter or the like, and a large amplitude Doppler signal such as tissue motion can be obtained. It is possible to draw from a weak signal such as to a peripheral blood vessel without causing a situation such as saturation or lack of a minute signal.

In the present invention, the conversion characteristics of the compression means and the decompression means are preferably inverse characteristics such as logarithmic conversion and exponential conversion. This can minimize the influence of signal compression on the spectrum and the like.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be specifically described below with reference to the drawings.

FIG. 1 is a diagram showing an embodiment of an ultrasonic diagnostic apparatus according to the present invention. An ultrasonic probe 10 comprising a transmitting unit 11 and a receiving circuit 12 and a single element or array type probe are used. A phasing circuit 13 that performs deflection / convergence operation of an ultrasonic beam according to the probe, and a video processing circuit that performs a logarithmic compression or detection process on the output of the phasing circuit 13 to form a B-mode signal. 14 and received signal (phase adjusting circuit 13 output)
Signal processing means 20 for performing Doppler signal processing, a scan converter 15 for inputting the B-mode signal from the video processing circuit 14 and blood flow information which is the calculation result from the signal processing means 20, and a display 16. .

The signal processing means 20 includes a pair of quadrature demodulators 21a and 21b for demodulating a received signal with reference frequency signals having a phase difference of 90 degrees from each other, and these quadrature demodulators 21a and 2b.
A / D converters 22a and 22b for A / D converting the complex signal from 1b, MTI filters 23a and 23b for removing unnecessary fixed reflection signals such as the heart wall, and velocity / speed based on the digital Doppler signal. And a calculator 24 for calculating blood flow information such as dispersion and power. Quadrature demodulator 2
1a and 21b are connected to a 0-degree reference frequency signal generator and a 90-degree reference frequency signal generator (not shown),
The input signal is mixed and demodulated with each reference frequency signal. As the A / D converters 22a and 22b, those of 10 to 14 bits are generally used, but in the present embodiment, 12-bit A / D converters are used. Although not shown, the calculation unit 24
Is provided with a color display circuit for displaying the blood flow directions in blue and red and the velocity (Doppler frequency) in luminance based on the blood flow information which is the calculation result. In addition, the quadrature demodulator 21
A low pass filter may be provided in the subsequent stage of a and 21b.

Further, the signal processing means 20 is an A / D converter 2
Nonlinear analog compressors 25a and 25b are provided as compression means in front of 2a and 22b, and MTI filters 23a and 23b.
The non-linear expanders 26a and 26b are provided in the preceding stage as expansion means. In this embodiment, the non-linear compressor has an input demodulated signal of about 102 dB and an amplitude of about 6
An analog compressor for compressing a 0 dB signal is used, and logarithmic conversion is used as its conversion characteristic.
As the nonlinear stretcher, amplitude information of the input address is A / D converted signal (about 60 dB: 0 to 2 ⁹⁾ corresponds to a signal output address is decompression conversion (about 102d
A ROM table corresponding to B: 0 to ± 2 ¹⁶ ) is used, and exponential conversion is used as its conversion characteristic.

The signal processing of the ultrasonic diagnostic apparatus having such a configuration will be described. First, the ultrasonic wave is transmitted from the wave transmission unit 11 into the living body 1 by the probe 10. The reflected ultrasonic signal reflected in the living body is received by the same probe 10 and converted into an electric signal by the receiving circuit 12, and an appropriate alignment is performed depending on whether the probe is a single element or array type probe. The phase circuit 13 performs the deflection / convergence operation of the ultrasonic beam. The output of the phasing circuit is the video processing circuit 14 for detection and the like.
Via the scan converter 15 as a B-mode signal.
And is displayed on the display 16.

On the other hand, the output S of the phasing circuit 13 is also distributed to the quadrature demodulators 21a and 21b, mixed and demodulated with the reference frequency signals S0 and S90 of 0 degree and 90 degrees, respectively, and the in-phase component I and the 90 degree component are obtained. Separated into Q and. The signal demodulated in this way is a modulation of ultrasonic waves due to blood flow, and is approximately 102 dB.
This is a signal (corresponding to 16 bits). Up to now, high-frequency components have been A / D-converted as noise in a blood flow signal after being cut by a low-pass filter, but it has been found that high-bit signals include important information such as peripheral blood vessels. Therefore, here, the high frequency component of the blood flow signal is logarithmically compressed and A / D converted without being cut by the low pass filter. That is, the demodulated composite signals I and Q are compressed to about 60 dB (10 bits) by the non-linear compressors 25a and 25b, respectively, and then the 12-bit A / D converter 22a,
It is digitally converted at 22b.

The dynamic range of the digitized Doppler signal is restored by the non-linear expanders 26a and 26b having the inverse conversion characteristics of the non-linear compressors 25a and 25b. That is, the non-linear decompressors 26a and 26b output the inputted amplitude information of about 10 bits in association with the 16-bit information by the built-in ROM table. The signals Id and Qd inversely converted (expanded) in this way are MTI.
After removing unnecessary fixed reflection signals by the filters 23a and 23b, the signals are supplied to the arithmetic unit 24, and V = tan ^-1 (is calculated by taking the arctangent of the ratio of the real number part and the imaginary number part as shown in the following equation. Q / I) Blood flow information such as velocity, dispersion, and power is calculated and extracted. The result of this calculation is added to the color tone in the color display section, and then supplied to the scan converter 15 and drawn on the display 16 in parallel or individually with the B mode signal.

With this configuration, blood flow signals having a wide dynamic range can be processed without being restricted by the relatively narrow dynamic range of the A / D converter, and Doppler with a large amplitude such as tissue motion can be processed. It is possible to draw from a signal to a weak signal such as a peripheral blood vessel without causing a situation such as saturation or lack of a minute signal. Furthermore, in this embodiment, since the data is compressed before A / D conversion, it is less susceptible to so-called quantization noise.

The influence of the non-linear processing by the compressor on the spectrum shape is relatively small due to the effect of expansion conversion.
No effect was observed in the color flow display for determining the average speed. Moreover, the influence was not visible even in the power display regardless of the shape of the spectrum.

Next, a second embodiment of the ultrasonic diagnostic apparatus of the present invention will be described. FIG. 2 is a diagram showing an outline of the ultrasonic diagnostic apparatus according to the second embodiment, and the same components as those in FIG. 1 are indicated by the same numbers. In the ultrasonic diagnostic apparatus of FIG. 2, the signal processing system sent from the phasing circuit 13 to the scan converter 15 through the video processing circuit 14 is the same as that of the apparatus of FIG. 1, but a signal processing means for Doppler signal processing. The configuration of 20 is different, and the non-linear compressors 25a and 25b are arranged before the quadrature demodulators 21a and 21b, respectively.

In this configuration, the output of the phasing circuit 13 is compressed by the non-linear compressors 25a and 25b and then distributed to the quadrature demodulators 21a and 21b, and the 0-degree reference frequency signal and the 90-degree reference frequency signal, respectively. Is mixed and demodulated. Thereafter, similar to the embodiment of FIG. 1, the complex signal is 12 bits A respectively.
After being digitally converted by the D / D converters 22a and 22b and the dynamic range thereof being restored by the non-linear expanders 26a and 26b, they are supplied to the calculation unit 24 after passing through the MTI filters 23a and 23b, and the speed / dispersion / Blood flow information such as power is calculated and extracted. After the color tone is added, the calculation result is supplied to the scan converter 15 and drawn on the display 16 in parallel or individually with the pulse Doppler signal and the B-mode signal (not shown).

In the present embodiment, unlike the embodiment shown in FIG. 1, since the received signal is subjected to nonlinear compression conversion before demodulation conversion, and after A / D conversion after demodulation conversion, the A / D converter 22 is used. The effect of the narrow dynamic range of the analog quadrature demodulator 21 can be reduced. Further, similarly to the embodiment of FIG. 1, since the data is compressed before A / D conversion, it has an advantage that it is hardly affected by quantization noise.

In the above-described embodiments, the ultrasonic diagnostic apparatus having a configuration in which the Doppler signal processing means A / D-converts the demodulated signal and calculates it in the calculation section has been described. However, the present invention is an array type probe. Also, the present invention can be applied to an ultrasonic diagnostic apparatus having a configuration in which each received signal is subjected to parallel A / D conversion, and then each digital signal is subjected to delay control and then added to demodulate a digital received signal obtained by a digital mixer.

FIG. 3 shows such a configuration. The number of bits of each parallel A / D converter 31 is 12, and therefore 72d.
It has a dynamic range of B. When the parallel addition of these A / D converters (for example, 256 channels) is performed, the output signal becomes 20 bits, about 120 dB. This digitized signal is then processed by the two digital demodulators 32.
Although each is mixed with an 8-bit reference frequency signal, the capability of the digital demodulator 32 is generally about 16 bits. Therefore, here, the nonlinear compressor 33 is arranged between the addition output (phased output) 31a and the demodulator 32 to compress the 20-bit signal to 16 bits. Further, a non-linear expander 34 is arranged in the subsequent stage of the demodulator 32. In this case, the non-linear compressor 33 is similar to the non-linear expander 26 of FIG. 1 or FIG.
A digital compressor using an OM table can be used. That is, a ROM table is used in which the input address corresponds to the amplitude information (0 to ± 2 ¹⁹ ) of the demodulated signal of about 120 dB, and the output address corresponds to the compressed and converted about 102 dB (0 to ± 2 ¹⁵ ). .

The 16-bit signal compressed in this way is demodulated by the demodulator 32 and then the dynamic range is restored by the non-linear decompressor 34. After that, the MTI filter is used as in the embodiment of FIGS. And is sent to the calculation unit.

In this embodiment, the compressor 33 and the decompressor 34 are arranged in the front stage and the rear stage of the digital demodulator 32, respectively, whereby the relatively narrow dynamic range of the digital demodulator 32 can be effectively expanded. .

In the present invention, the non-linear compressor and the non-linear decompressor can perform the compression conversion / expansion conversion by software, not by the ROM table, but by calculation by the DSP.

The characteristics of the compression conversion / expansion conversion are not limited to logarithmic conversion / exponential conversion, but may be combinations of square root / square, cube root / cubic, polygonal line approximation, etc. within the scope of the present invention. It is valid. Further, it is desirable that the conversion characteristics of the compression means and the decompression means are opposite to each other.
It is not necessarily limited to this.

Further, in each of the above-described embodiments, an example in which the present invention is applied to a real-time two-dimensional blood flow drawing function called color flow mapping has been described. However, the present invention has a function of displaying a spectral waveform such as so-called pulse Doppler. Similarly, it can be applied to the signal processing of the ultrasonic diagnostic apparatus having the above. In this case, it is particularly effective in the case of a spectrum having a normal distribution in which the spurious noise accompanying the non-linear processing / inverse non-linear processing is relatively small. It was

[0033]

According to the present invention, even when a signal passes through a processing means having a relatively narrow dynamic range such as an A / D converter in the process of Doppler signal processing, the processing is performed before and after such processing means. By providing the signal compressing means and the expanding means, respectively, the blood flow signal having a relatively wide dynamic range can be processed without being limited to the relatively narrow dynamic range of the signal processing means, and a large amount of motion such as tissue motion can occur. It is possible to draw from a Doppler signal of amplitude to a weak signal such as a peripheral blood vessel without causing a situation such as saturation or lack of a minute signal.

As a result, the running state of blood vessels in the body including the micro blood vessels can be easily visualized, and the usefulness of the color flow diagnostic apparatus can be particularly enhanced.

[Brief description of the drawings]

FIG. 1 is an ultrasonic color Doppler diagnostic apparatus 1 according to the present invention.
Figure showing an example

FIG. 2 is a diagram showing another embodiment of the ultrasonic color Doppler diagnostic apparatus according to the present invention.

FIG. 3 is a diagram showing another embodiment of the ultrasonic color Doppler diagnostic apparatus according to the present invention.

FIG. 4 is a diagram showing a conventional ultrasonic color Doppler diagnostic apparatus.

[Explanation of symbols]

 10- ・ Ultrasonic probe 11- ・ Transmission unit 12- ・ Reception circuit 13- ・ Phase adjustment circuit 14- ・ Video processing Circuit 15 ... Scan converter 16 ... Display 21a, 21b .... Quadrature demodulator 22a, 22b ..... A / D converter 23a, 23b ... ... MTI filter 24 ... Calculator 25a, 25b ... Nonlinear compressor 26a, 26b ... Nonlinear expander

Claims (2)

[Claims] 1. A receiving means for receiving a blood flow signal from the inside of a living body and converting it into an electric signal, a signal processing means for processing the received signal, and a blood flow information using the processed signal. In the ultrasonic diagnostic apparatus comprising means and display means for displaying the calculation result, the signal processing means includes at least demodulation means and A / D conversion means for demodulating a received signal, and the demodulation means or the A An ultrasonic diagnostic apparatus comprising: a signal compression means provided before the A / D conversion means; and a signal expansion means provided before the calculation means. 2. The ultrasonic diagnostic apparatus according to claim 1, wherein the conversion characteristics of the compression means and the expansion means are opposite to each other.