JPH0856943A - Ultrasonic diagnostic equipment - Google Patents

Abstract

(57) [Abstract] [Purpose] To provide a low-cost ultrasonic diagnostic apparatus having a small circuit scale. [Structure] Pseudo noise generating means 6 for generating a pseudo noise signal
And a plurality of adding means for adding the pseudo noise signal to the received signal
17-1 to 17-4, a plurality of A / D converting means 4-1 to 4-4 for converting the outputs of the respective adding means into digital signals, and a delay for delaying and adding the outputs of the plurality of A / D converting means. In the ultrasonic diagnostic apparatus including the adding means 5, as delay adding means, delay means 19-1 to 19-4 for delaying and outputting the digital data input from each of the A / D converting means,
Interpolating means 20-which interpolates the digital data input from the delay means with zero, and then outputs the filtered data.
1 to 20-4 and addition means 21 for adding the outputs of a plurality of interpolation means are provided, and the interpolation means is configured to remove the components of the pseudo noise signal. Since the pseudo noise signal is removed by the filter of this interpolation means, it is not necessary to provide a special filter for removing the pseudo noise signal, and the circuit scale can be reduced.

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 digitally processing echo signals received by a plurality of transducers and displaying an image of a region to be examined, and in particular, realizes highly accurate A / D conversion. It is configured to be possible.

[0002]

2. Description of the Related Art An ultrasonic diagnostic apparatus sends ultrasonic waves into a living body from a plurality of elements (transducers) of a probe, receives reflected echoes generated by the difference in acoustic impedance of internal tissues at each element, and An image of the site to be examined is formed based on the image information obtained from the echo signal.

The probe is provided with several tens to several hundreds of elements, and a group consisting of a plurality of these elements is driven all at once to emit one ultrasonic beam.
The ultrasonic beam is moved by removing the leftmost element of this group and repeating the operation of adding one element to the right side.

By giving a slight time difference to the ultrasonic wave emission time of each element of this group, an ultrasonic beam that converges in a certain direction can be obtained. By changing the time difference, the ultrasonic beam is emitted. It is possible to change the direction and the focal range where the beam converges.

The echo signal of the ultrasonic beam emitted from each element of the group is received by each element, and the received echo signal is corrected according to the arrival time difference from the site to be examined to each element. By adding after adding, an image signal with high resolution can be obtained.

An analog delay line composed of a coil and a capacitor has been conventionally used for this time correction. However, it is difficult to secure the performance of the analog delay line when a high frequency or a long delay time is required. There were problems such as variations in delay time depending on parts. Therefore, a method has been devised in which an echo signal is converted into a digital signal by an A / D converter and then delayed addition is performed (Japanese Patent Laid-Open No. 61-8039).

As shown in FIG. 14, the ultrasonic diagnostic apparatus of this type has a probe 1 having a plurality of elements T1 to T4 (in this case, the number of elements is four to simplify the structure). , Pulser receivers 2-1 to 2-4 that generate pulses for driving each element and that receive the pulses received by each element, and gain control amplifiers 3-1 to 3-4 that amplify the received signal , A / D converter 4-1 for converting input signal to digital signal
4-4, a delay adder 5 that delays and adds input digital signals, and a controller 7 that controls the operation of each unit. In addition, in pulse Doppler and color flow blood flow imaging equipment, in order to obtain blood flow information using the Doppler effect,
Reference signal generator 10 for generating orthogonal reference signals and multipliers 8, 9 for multiplying orthogonal reference signals and echo signals
And a filter 11, which removes the harmonic components of the input signal,
12 and a signal processing unit 13 for performing velocity calculation based on the signals output from the filters 11 and 12, and detects the output of the digital beam synthesizing unit 5 for B mode (tomographic image display). A digital scan converter (DSC) 15 that includes a detector 14 and that outputs the digital signal output from the detector 14 and the signal processing unit 13 in accordance with television scanning (scanning), and an ultrasonic image. And a display unit 16 for displaying.

In this ultrasonic diagnostic apparatus, the control unit 7
A pulse trigger signal whose phase is controlled in order to perform electronic focusing, steering (fan-shaped scanning), linear scanning, etc. is output to the pulser receivers 2-1 to 2-4, and the pulser receivers 2-1 to 2-4 generate pulses. In synchronization with the trigger signal, drive pulses for driving the elements (transducers) T1 to T4 of the probe 1 are generated. The ultrasonic waves reflected in the subject are received by the same elements T1 to T4, pass through the pulsar receivers 2-1 to 2-4, are appropriately amplified by the gain control amplifiers 3-1 to 3-4, and A / D converter 4
It is sent to -1 to 4-4 and converted into a digital signal.
The digital signals converted by the A / D converters 4-1 to 4-4 are delay-added by the delay adder 5.

The digital signal output from the delay adder unit 5 is processed for displaying a video. In the pulse Doppler or color flow blood flow imager, the digital output signal is multiplied by the reference signal generated by the reference signal generator 10 in the multipliers 8 and 9 to obtain the filters 11 and 12.
After the harmonic components have been removed by, the signal processing unit 13 removes the clutter signal and calculates the speed, and the result is displayed on the display unit 16 via the DSC 15.

In the B mode, the output of the delay adder 5 is detected by the detector 14, and a tomographic image is displayed on the display 16 via the DSC 15.

The echo signal received by each element has a wide dynamic range because it includes reflected waves from those having different reflectances such as diaphragm and blood.
Therefore, A for converting the echo signal into digital data
It is necessary to use an A / D converter having a large number of bits so that it can support a wide dynamic range. But,
A / uses the same number of elements as dozens or hundreds
If a D converter having such a wide dynamic range and high A / D characteristics is prepared, the cost of the ultrasonic diagnostic apparatus will increase significantly.

In order to solve these problems, the inventors of the present invention need not improve the performance of the A / D converter itself.
We devised an ultrasonic diagnostic apparatus that can reduce the error in A / D conversion (Japanese Patent Application No. 5-30427).

As shown in FIG. 15, this apparatus has an array type ultrasonic probe 1 (N = N in this example for simplification of explanation) composed of N transducers T1 to TN. Four
And pulse generators 2-1 to 2-4 that receive pulses received by each element and pseudo noise that outputs a staircase noise waveform (dither signal). The source 6, the adders 17-1 to 17-4 for adding the outputs of the pulser receivers 2-1 to 2-4 and the dither signal, and the outputs of the adders 17-1 to 17-4 are A / D converted. A / D converters 4-1 to 4-4 and A / D converters
A delay addition unit 5 that delays and adds the outputs of the D converters 4-1 to 4-4 and a control unit 7 that controls each unit are provided. Further, the configuration for forming a video display signal using the output of the delay adder 5 is the same as that of the conventional device (FIG. 14) except that the filter 18 is added in the B mode.

The basic operation of this ultrasonic diagnostic apparatus is the same as that of the apparatus shown in FIG. However, the output of the pseudo noise source 6 is added to the echo signals received by the pulser receivers 2-1 to 2-4 by the adders 17-1 to 17-4, and the output of the delay addition unit 5 in the B mode. The only difference is that the pseudo noise signal contained in is removed by the filter 18.

The operation using the pseudo noise signal will be described in detail.

There are various types of noise waveforms generated from the pseudo noise source. Now, this pseudo noise signal N
(M) sets 4 sample clocks to 1 as shown in FIG.
A signal having a sawtooth waveform with an amplitude of 0.75 corresponding to a cycle is used. At this time, N (m) can be expressed as follows.

N (m + 0) = − 0.375 N (m + 1) = − 0.125 N (m + 2) = 0.125 N (m + 3) = 0.375 The 1 LSB of the A / D converter is equal to the amplitude 1, If a DC signal with an amplitude of 1.51 is input to the A / D converter and the threshold level of the A / D converter is 1.5, if there is no dither signal addition, the A / D All four values output from the converter during four sample clocks are 2, and an error of 0.49 is generated between the four values and the input DC signal.

On the other hand, in the case where the dither signal is added, the A / D converter has 1.1 times between 4 sample clocks.
The values 35, 1.385, 1.635, 1.885 are sequentially input, and the A / D converter A / D-converts the values into 1, 1, 2, 2. Taking the average of these converted values, the average value is 1.5, so the error with the input signal is 0.01
Will be reduced to.

As in this example, the quantization error can be reduced by adding the pseudo noise signals and taking the average. Comparing with the maximum value of the quantization error, the maximum value of the normal quantization error is ± 0.5, but when the process of adding the pseudo noise signals and taking the average is performed, the average value The maximum value of the quantization error is ± 0.125, which is 1/4 of the normal value.

When A / D conversion is performed by this method, the sampling speed is equivalently reduced, but the quantization error is reduced.

The pseudo noise source 6 generates noise for such a purpose. For the pseudo noise signal, it is necessary to select one having a period and a waveform such that its frequency spectrum does not overlap with the band of the received signal.

The received signals that have been input are added to adders 17-1 to 17-
4, the pseudo noise signal output from the pseudo noise source 6 is added, the added signal is converted into digital data by the A / D converters 4-1 to 4-4, and the converted digital data is delayed. Delay addition is performed in the adder 5. At the time of this delay addition, the delay addition section 5 adds the outputs of the A / D converters 4-1 to 4-4 in each channel over four samples (every new sample data is input, the previous three Together with sample data),
The data of each channel thus added is delayed and added to one.

In the B mode, the delay-added received signals are passed through the filter 18 having a low-pass characteristic. The pseudo noise signal component included in the delay-added received signal is different from the original frequency band of the received signal (echo) and is higher than the frequency band of the received signal. The component of is removed by this filter 18. The received signal that has passed through the filter 18 is subjected to envelope detection by the detection unit 14 and displayed on the display unit 16 via the DSC 15.

In the Doppler blood flow meter or the Doppler imager, the delay-added received signals are input to the multipliers 8 and 9, where they are mixed with two reference signals that are orthogonal to each other, and then to the filters 11 and 12. input.

The filters 11 and 12 are intended to remove the harmonic components in the phase detection output, but it is also possible to remove the pseudo noise signal together. As a result of the phase detection in the multipliers 8 and 9, the band of the received signal shifts to the direct current and low frequency bands. Although the spectrum of the pseudo noise signal also shifts in frequency, its band does not overlap with that of the received signal, so only the received signal is taken out by the filters 11 and 12 having the low-pass characteristic.

The signal processing unit 13 calculates blood flow information from the received signal in which only low frequency components are extracted by the filters 11 and 12, and a screen showing the blood flow is displayed on the display unit 16 through the DSC 15 based on this calculation. Is displayed.

As described above, by introducing the above-described method for the A / D conversion of the ultrasonic diagnostic apparatus, the conversion accuracy can be enhanced and the S / N ratio can be improved.

[0028]

However, in the conventional ultrasonic diagnostic apparatus using the pseudo noise signal, a filter for removing the pseudo noise signal is required, which increases the circuit scale and dither signal. A unless the frequency falls between the input signal frequency and the Nyquist frequency
There is a problem that the / D conversion characteristic cannot be improved, in other words, it cannot be improved when the input frequency is high.

Further, there is a problem that the dither effect is difficult to appear when the signal input to the A / D converter contains a large amount of noise components or when the signal amplitude is large.

The present invention solves the above-mentioned conventional problems and prevents the increase of the circuit scale by substituting the filter function for removing the pseudo noise signal with another function, thereby reducing the ultrasonic diagnostic cost. The purpose is to provide a device.

It is another object of the present invention to provide an ultrasonic diagnostic apparatus which can accurately capture an echo signal even when the frequency of the echo signal is high.

It is another object of the present invention to provide an ultrasonic diagnostic apparatus capable of displaying a high quality image even when the noise amount or the signal amplitude of the input signal is large.

Further, it is possible to provide an ultrasonic diagnostic apparatus capable of performing highly accurate A / D conversion by preventing the generation of unnecessary noise from a pseudo noise source and displaying a high quality image. Has an aim.

[0034]

Therefore, in the present invention, pseudo noise generating means for generating a pseudo noise signal, a plurality of adding means for adding a pseudo noise signal to a received signal, and outputs of each adding means are digital signals. In the ultrasonic diagnostic apparatus provided with a plurality of A / D conversion means for converting to A and D and a delay addition means for delaying and adding outputs of the plurality of A / D conversion means The delay means for delaying and outputting the digital data input from, the interpolating means for interpolating the digital data input from the delay means with zero, and then applying the filtering process, and the outputs of the plurality of interpolating means are added. An adding means is provided, and the component of the pseudo noise signal is removed by this interpolating means.

Further, inverting means for inverting the phase of the pseudo noise signal added to half of the adding means is provided.

Further, the switching means for switching the phase of the pseudo noise signal applied to each addition means to the normal phase or the negative phase, and the delay addition means when the switching means selects either the normal phase or the negative phase. A memory for storing the output and an adding means for adding the output of the delay adding means and the data read from the memory when the switching means selects the other of the normal phase and the reverse phase are provided.

Further, the addition of the pseudo noise signal to one received signal is performed by the 2n number of addition means, and this 2
Inversion means for inverting the phase of the pseudo noise signal added to half of the n addition means is provided.

Further, a band limiting means for setting the frequency of the pseudo noise signal to a low frequency band which does not overlap with the frequency of the received signal and for limiting the band of the output signal of the A / D conversion means is provided.

Further, the waveform of the pseudo noise signal is changed according to the noise amount of the received signal.

Further, the phase of the pseudo noise signal is changed according to the transmission sequence of the reception signal.

When the amplitude of the received signal slightly increases with the increase of the transmission sequence, the phase of the pseudo noise signal is decreased with the increase of the transmission sequence, and the amplitude of the received signal is increased with the increase of the transmission sequence. When decreasing slightly,
The phase of the pseudo noise signal is increased as the transmission sequence is increased.

Further, a ramp wave is generated as the pseudo noise signal from the pseudo noise generating means.

Further, the offset of the ramp wave is changed for each transmission sequence.

Further, the slope of the ramp wave is changed according to the noise amount of the received signal.

The slope of the ramp wave is changed according to the frequency of the received signal.

[0046]

Therefore, in the device including the interpolating means in the delay adding means, the pseudo noise signal is removed by the filter of the interpolating means, so that it is not necessary to provide a special filter for removing the pseudo noise signal, and the circuit scale is reduced. Can be made smaller.

After adding the normal phase pseudo noise signal to half of the adding means and adding the anti-phase pseudo noise signal to the remaining half, or inverting the pseudo noise signal to be added to each adding means every time. , By adding the delayed addition results, or by dividing one received signal into two and adding the pseudo noise signal of the normal phase to one and the pseudo noise signal of the opposite phase to the other , It is possible to cancel the pseudo noise signal. Therefore, even if the frequency of the received signal that does not require a special filter for removing the pseudo noise signal is high, the frequency of the pseudo noise signal is set low so as not to overlap the frequency band of the received signal, and the A / D It is possible to improve the S / N ratio and the dividing function by limiting the band of the converted signal to remove the component of the pseudo noise signal.

Further, the pseudo noise signal waveform capable of improving the A / D conversion with high accuracy will rather increase the error when the received signal contains a lot of noise. for that reason,
The pseudo noise signal waveform is selectively used according to the noise amount of the received signal, and when the noise is small, the pseudo noise signal waveform with a high degree of improvement in A / D conversion is used, and when the noise is large, the A / D conversion is improved. By using a pseudo noise signal waveform with a low degree, optimum improvement can be achieved under each situation.

When the amplitude of the received signal varies greatly with time, the quantization error cannot be expected to be reduced even if the pseudo noise signal is added to the sampling data of one transmission sequence that is temporally preceding and succeeding. However, when the transmission sequence is repeated, the amplitude of the received signal from the same depth in each transmission sequence is almost constant, so a pseudo noise signal is added to such sampling data (that is, pseudo noise is added for each transmission sequence). The accuracy of A / D conversion can be improved by adding different phase levels of the noise signal.

In this case, if the amplitude of the received signal at the same depth slightly increases as the transmission sequence increases, a pseudo noise signal waveform whose phase decreases as the transmission sequence increases is used to cancel this. Conversely, in the case of a slight decrease, the effect can be further enhanced by using the pseudo noise signal waveform in which the phase increases.

When a ramp wave is used instead of the pseudo noise signal, unnecessary noise generation from the pseudo signal generation source is eliminated, and the S / N ratio and resolution are improved. In this case, by changing the offset of the ramp wave for each transmission sequence, it is possible to obtain the same effect as in the case of adding different phase levels of the pseudo noise signal for each transmission sequence described above.

When the slope of the ramp wave is changed according to the noise amount of the received signal, the same effect as when changing the waveform of the pseudo noise signal according to the noise amount can be obtained.

Further, by changing the slope of the ramp wave according to the frequency of the received signal, the A / D conversion accuracy can be increased and the S / N ratio can be improved in an optimum form that can be obtained in the received state.

【Example】

(First Embodiment) In the ultrasonic diagnostic apparatus of the first embodiment, the delay addition section removes the pseudo noise signal together with the delay addition processing.

As shown in FIG. 1, this apparatus includes analog adders 17-1 to 17-4 for adding the pseudo noise signal generated from the pseudo noise generator 6 to the echo signal, and an analog adder 17-1. -17-4 are provided with A / D converters 4-1 to 4-4 for A / D converting the outputs and delay adder 5 for delaying and adding the converted digital data. Delay means 19-1 to 19-4 for realizing a delay by making a difference between the time of writing data to the memory and the time of reading data,
Interpolation means 20-1 to 20-1 to set the delay time in smaller units
20-4 and an adder 21 for adding the outputs of the respective interpolators 20-1 to 20-4. Although the means for obtaining the echo signal and the means for displaying the delayed addition output from the delay addition section 5 as an image are omitted, they are the same as those in the conventional apparatus shown in FIG.

The echo signals received by the respective elements are input to the adders 17-1 to 17-4 of this apparatus after being amplified to a proper amplitude and input from the pseudo noise generator 6. . These signals are added by adders 17-1 to 17-4, converted to digital data by A / D converters 4-1 to 4-4, and input to the delay addition unit 5.

The input digital data is written in the memories constituting the delay means 19-1 to 19-4 of the delay adder unit 5 and is asynchronously read to be delayed. At this time, from each of the delay means 19-1 to 19-4, the sample data of the number corresponding to one cycle of the pseudo noise signal, which is input to the respective channels before and after in time, is read.

What is important here is this delay means 19-1.
The delay units obtained in 19-4 are A / D converters 4-1 to 4-4.
That is, the sampling frequency is -4. Since the sampling frequency of a generally used A / D converter is several tens of MHz, the unit of delay time is several tens of nsec. However, the delay addition requires a finer unit of delay time with an accuracy of several nsec.

Therefore, by the interpolating means 20-1 to 20-4,
Set the delay time unit more finely. This interpolation means 20
-1 to 20-4 are configured by a low-pass filter that smoothes the interpolated data of zero as well as inserting zero between the sampling data, and by inserting zero between the true sampling data, It works by increasing the sampling frequency and making the unit of delay time finer. The delay time is set in various units by changing the number of zeros inserted.

The outputs of the respective interpolating means 20-1 to 20-4 are input to the adding means 21, and the digital data of each channel are delayed and added under a fine delay time unit.

This interpolation method is the same as that used when reproducing the CD player.

The pseudo noise signal added to the echo signal is
It is removed by the low-pass filters of the interpolation means 20-1 to 20-4.

As described above, in the device of the first embodiment, since the filters in the interpolating means 20-1 to 20-4 of the delay adder 5 are also used for removing the pseudo noise, a filter for removing the pseudo noise signal is used. There is no need to provide it separately. Therefore, the circuit scale of the ultrasonic diagnostic apparatus can be reduced.

(Second Embodiment) The ultrasonic diagnostic apparatus of the second embodiment is constructed so that the pseudo noise signal added to the echo signal is canceled by the delay addition. As shown in FIG. 2, this device has two (17) of four analog adders.
-3, 17-4) is provided with an inverting amplifier 22 for inverting the phase of the pseudo noise signal. The other structure is the same as that of the device of the first embodiment (FIG. 1).

In this apparatus, it is assumed that the ultrasonic beam is not steered, that is, it is linearly scanned. Under this condition, ch1 and ch4, ch2 and c
The same delay time is given to h3.

Due to the presence of the inverting amplifier 22, the adder 17-
3 and 17-4, from the pseudo noise generator 6 to the adder 17-
A pseudo noise signal whose phase is inverted from that of the pseudo noise signal added to 1 and 17-2 is added. Therefore, in the addition in the adding means 21 of the delay addition unit 3, ch1 and ch4 are added.
The pseudo noise signals included in the above are canceled in opposite phases, and similarly, the pseudo noise signals included in ch2 and ch3 are also canceled. Therefore, a filter for removing the pseudo noise signal is unnecessary, and an ultrasonic diagnostic apparatus having a small circuit scale can be realized.

(Third Embodiment) The ultrasonic diagnostic apparatus of the third embodiment is constructed so that each of the delayed addition outputs that are temporally before and after contains a normal noise phase and an antiphase noise signal. The pseudo noise signal is canceled by adding.
As shown in FIG. 3, this device includes a switch 23 for switching the phase of a pseudo noise signal and a memory 24 for storing the output of the delay adder 5 in the received signal for one transmission sequence.
And an adder 25 for adding the new output of the delay adder 5 and the output read from the memory 24. The other structure is the same as that of the device of the first embodiment (FIG. 1).

This device is supposed to be used for beamforming twice in the same direction. The delay time setting at the time of reception at this time is not changed.
First, in the first sequence, the switch 23 is switched so that the pseudo noise signal generated from the pseudo noise generator 6 does not pass through the inverting amplifier 22 and is added to each of the adders 17-1 to 17-4. The obtained delayed addition signal is stored in the memory 24. Next, in the second sequence, the switch 23 is switched so that the pseudo noise signal is applied to each of the adders 17-1 to 17-4 through the inverting amplifier 22. Then, the delayed addition signal obtained at that time and the delayed addition signal in the first sequence are read from the memory 24 and added by the adder 25.

At this time, in the adder 25, the phases of the pseudo noise signals included in the first sequence and the second sequence are opposite to each other, so that they are canceled by the addition. This eliminates the need for a filter for removing the pseudo noise signal and realizes an ultrasonic diagnostic apparatus having a small circuit scale.

In this example, the case where the sequence is added twice has been described, but it is clear that the same effect can be obtained by the addition of three times or more by the configuration of the memory 24 and the adder 25.

(Fourth Embodiment) In order to cancel the pseudo noise signal, the ultrasonic diagnostic apparatus of the fourth embodiment adds the normal phase pseudo noise signal and the reverse phase to the received signal of one channel. The pseudo noise signal of is added. Further, in this device, the number of channels is switched depending on whether the echo of the deep region is captured or the echo of the shallow region is captured, and the pseudo noise signal is added by the above method only when the echo of the shallow region is captured. ing.

This apparatus, as shown in FIG. 4, corresponds to eight channels of beamforming and has eight adders 17
-1 to 17-8 and eight A / D converters 4-1 to 4-8
And a delay adder 5 that delays and adds the digital data output from each of the A / D converters 4-1 to 4-8, and turns on / off the pseudo noise signal output from the pseudo noise generator 6.
The switch 26 for turning off and the adders 17-1, 17-2, 17-
Inverting amplifier that inverts the pseudo noise signal added to 7, 17-8
22, ch1 and ch3, ch2 and ch4, ch5 and ch
Switch for switching between 7 and ch6 and ch8 respectively
27-1, 27-2, 27-3, and 27-4.

When the echo of a deep part is to be captured by this device, the switch 26 is turned off and the switches 27-1 to 27-1.
27-4 are connected to the a side, respectively, and the conventional operation without using the pseudo noise signal is performed using 8 channels.

When the echo of the shallow region is taken in, the switch 26 is turned on and the switches 27-1 to 27-4 are connected to the side b. As a result, the channel used is
Although it is reduced to four channels of ch3, ch4, ch5 and ch6, the signal of each channel is in each of two circuits, that is, the echo signal of ch3 is in the adders 17-1 and 17-3,
The echo signal of ch4 is sent to the adders 17-2 and 17-4 and ch5
Echo signal to adders 17-5 and 17-7, and ch6
The echo signal of is input to the adders 17-6 and 17-8. This is because if the number of A / D converters used is reduced as the number of channels decreases, the increase in the dynamic range at the time of delay addition decreases, so the echo data of one channel is input to multiple A / D converters. By doing so, it is intended to prevent the decrease of the dynamic range.

The pseudo noise signal that has passed through the switch 26 is in normal phase to the adders 17-3 to 17-6, and the adders 17-1 and 17-
The signals are input to 2, 17, 7 and 17-8 in reverse phase via the inverting amplifier 22. Therefore, for example, with respect to the echo signal of ch3, the normal-phase pseudo noise signal is added in the adder 17-1 and the anti-phase pseudo noise signal is added in the adder 17-3. Since the digital data of these added values are based on the same echo data, they are delayed and added with the same delay in the delay adder 5. Therefore, the pseudo noise signal is canceled. The same applies to echo signals of other channels.

As described above, in the ultrasonic diagnostic apparatus of the fourth embodiment, when the pseudo noise signals are added, all the pseudo noise signals are canceled out, so that means for removing the pseudo noise signals is required. do not do.

(Fifth Embodiment) The ultrasonic diagnostic apparatus of the fifth embodiment adds a pseudo noise signal having a low frequency component to the echo signal in order to accurately obtain digital data of an echo signal having a high frequency. To do. In this device, a pseudo noise generator generates a low frequency pseudo noise signal. Further, band limiting means for removing a low-frequency pseudo noise signal from the output signal after A / D conversion is provided. Other configurations are the same as those of the devices of the above-described embodiments.

The operating principle of this device will be described with reference to FIG. In FIG. 5, (a) shows an input high frequency echo signal waveform. The amplitude of this input signal is 1LSBp
When it is p or less, the threshold value inside the A / D converter is not crossed, and therefore A /
The D conversion output becomes constant.

At this time, in the conventional example, a pseudo noise signal is used to solve the problem. However, when the frequency of the input signal is high and is close to the frequency component of the pseudo noise signal, the pseudo noise by the filter after A / D conversion is used. It becomes difficult to separate the noise signal, which causes a problem that the noise amount rather increases.

In the apparatus of this embodiment, as shown in (b),
This problem is solved by using a pseudo noise signal that has a lower frequency component than the input signal. (C) is the sum of the input signal (a) and the pseudo noise signal (b),
A / D conversion of this results in (d). Since (d) contains a pseudo noise signal component, the desired signal (e) can be obtained by performing band limitation to remove it.

(Sixth Embodiment) The ultrasonic diagnostic apparatus of the sixth embodiment uses the waveform of the pseudo noise signal to be added together with the echo signal according to the noise amount of the echo signal to obtain the optimum S / N ratio. Withdraw. In this device, the pseudo noise generator generates a pseudo noise signal having a different waveform depending on the noise amount of the received signal. Other configurations are the same as those of the devices of the above-described embodiments.

The point that the relationship between the noise amount of the received signal and the pseudo noise signal waveform affects the A / D conversion accuracy will be described with reference to FIG.

In FIG. 6A, the amplitude is 0.75LSBSBpp.
The pseudo noise signal of is shown. When the pseudo noise signal is applied to the input signal and the band is limited by the filter after A / D conversion, as described above, theoretically, 1 / 4LS
It is possible to obtain a B resolution. On the other hand, (b)
When applying the pseudo noise signal of 0.5 LSBpp
Only the resolution up to can be expected. However, what should be noted here is that various noises are present in an actual circuit. When considering the operation under noise, the theoretically excellent range of noise in which the waveform of (a) is effective is narrower than the effective range of the waveform of (b), and thus the waveform of (a) is lower. Request noise.

Therefore, in the ultrasonic diagnostic apparatus of this embodiment, the waveform of the pseudo noise signal applied to the input signal is changed according to the amount of noise in the circuit. For example, 2 of (a) and (b)
When different types of waveforms are prepared, the optimum S / N under each condition can be obtained by properly using the waveform of (a) when the noise is small and the waveform of (b) when the noise is large. The ratio can be drawn.

(Seventh Embodiment) The ultrasonic diagnostic apparatus of the seventh embodiment changes the phase level of the pseudo noise signal with respect to the echo signal of each transmission sequence when the ultrasonic beam is transmitted and received a plurality of times. A / D conversion accuracy is improved by adding. In this device, the pseudo noise generator is configured to output a pseudo noise signal having a different phase level for each transmission sequence, and the delay adder adds the sampling data of each transmission sequence that is temporally before and after. Instead, sampling data of the same depth is collected from each transmission sequence and added. Other configurations are the same as those of the devices of the above-described embodiments.

The apparatus of this embodiment can be used for pulse Doppler,
A device that transmits and receives a plurality of times in the same direction is assumed. FIG. 7 shows a waveform of an echo signal captured by such transmission and reception.

In FIG. 7, the x-axis represents the time from the transmission pulse generation, the y-axis represents the number of transmissions, and z represents the amplitude of the echo signal. The thick line represents the waveform of the echo signal, and dij represents the sample point after each transmission. The subscript i represents the number of transmissions, and j represents the order of sampling times. For example, the sampling data of the echo signal in the first transmission is d11, d12, d13, ....

In the apparatus of the above-described embodiments, N (m + 0) of the pseudo noise signal is added to d11, and N (m + 1) is d.
12 is added, N (m + 2) is added to d13, and different phase levels of the pseudo noise signal are added to the sampling data of one transmission sequence that is temporally before and after, as shown in this figure. As described above, when the sampling frequency is about several times as high as the echo frequency, the quantization noise component becomes white noise, and therefore it is hardly expected that the accuracy is improved by applying the pseudo noise signal.

However, if most of the echo signals are due to blood vessel walls or organs and the echo of blood flow is small, the echo signals at the same depth in different transmission sequences, for example, changes in d13, d23, d33 ,. Is loose.

Therefore, by adding the pseudo noise signal whose phase level is changed for each transmission sequence to the sampling data of each transmission sequence, the pseudo noise signal is different from the echo signal of the same depth in each transmission sequence. Phase level is added, that is, N (m +
0) to d13, N (m + 1) to d23, N (m +
By performing addition such as 2) to d33, it is possible to improve the accuracy at the time of A / D conversion.

The pseudo noise signal component in this case can be removed by providing an integrator after the phase detection.

(Eighth Embodiment) In the ultrasonic diagnostic apparatus of the seventh embodiment described above, the phase of the pseudo noise signal added to the echo signal is changed for each transmission sequence. In the ultrasonic diagnostic apparatus, the directionality of the pseudo-noise signal (pseudo-noise increases as the number of transmission sequences increases) according to whether the echo signals at the same depth at this time increase as the number of transmission sequences increases. It selects whether to raise or lower the phase level of the signal), thereby improving the A / D conversion accuracy.

The waveform of the pseudo noise signal is directional as shown in FIG. 8, and when the input signal also has an increased number of transmission sequences, the echo signal of the same depth slightly increases or decreases slightly. There is a direction. By combining the directionality of the waveform of the pseudo noise signal and the directionality of the input signal so as to cancel each other, the A / D conversion accuracy can be improved. For example, the waveform of the pseudo noise signal whose phase level increases as the number of transmission sequences increases as shown in FIG. 8 is better for an input signal having a slightly decreasing direction than for an input signal having a slightly increasing direction. High A / D conversion accuracy can be provided.

Therefore, the increase / decrease of the clutter signal in each part is detected, and a pseudo noise signal having directivity suitable for it is generated from the pseudo noise generator.
It is possible to perform highly accurate A / D conversion.

(Ninth Embodiment) The ultrasonic diagnostic apparatus of the ninth embodiment adds a ramp wave to the echo signal. As shown in FIG. 9, this device includes a ramp wave generator 28 in place of the pseudo noise source of the conventional device (FIG. 15), and
Since it is used for the pulse Doppler mode, the B mode configuration is removed.

The method of adding the pseudo noise signal to the received signal is intended to improve the accuracy by spreading the quantization noise by applying the pseudo noise signal to a wide frequency and limiting the band. The pseudo noise signal generation circuit is a high-speed digital circuit, and its output signal contains high frequency components, so noise components other than the pseudo noise signal that should be originally applied are applied, and the S / N ratio is reversed. It also happens when it gets worse. On the other hand, in the apparatus of this embodiment, since the ramp wave is used as the pseudo noise signal, it is possible to prevent such noise.

In the B mode, it is necessary to take in a wide range of signals from a shallow portion to a deep portion. Therefore, when a ramp wave is used as a pseudo noise signal, the range of change of the ramp wave becomes wide and the dynamic range is lowered and A / There is concern that it may cause saturation of the D converter.

However, the pulse Doppler opens the gate of the receiving amplifier only when the reflected wave from the desired portion returns,
Since it is a method of measuring only the reflected wave of a desired depth, the gate section for obtaining data is a very short time, and the change of the ramp wave between the gate start point and the gate end point is small. Therefore, the above-mentioned concerns are unnecessary in pulse Doppler, and in the case of pulse Doppler, the method of this embodiment using a ramp wave is extremely effective.

(Tenth Embodiment) The ultrasonic diagnostic apparatus of the tenth embodiment applies a ramp wave to the echo signal when the ultrasonic beam is transmitted and received a plurality of times in a form capable of increasing the A / D conversion accuracy. Can be applied. In this device, a ramp wave generator generates a ramp wave having a different offset for each transmission sequence. The other structure is the same as that of the device of the ninth embodiment (FIG. 9).

As described in the ninth embodiment, in the pulse Doppler mode, a ramp wave is applied to the echo signal instead of the pseudo noise signal to prevent noise from mixing.
Although the D / D conversion accuracy can be improved, however, as in the case of the seventh embodiment, when the amplitude of the echo signal changes greatly with time and the difference between the echo frequency and the sampling frequency is small, the ramp Even if a wave is applied, a great effect cannot be obtained.

Therefore, in the apparatus of this embodiment, the same effect as in the case of the seventh embodiment is obtained by changing the offset of the ramp wave for each transmission sequence.

FIG. 10 exemplifies the waveform of the ramp wave generated from the ramp wave generator of this apparatus. This DC
By selecting four ramp waves with different offsets in order each time the transmission sequence changes, and adding to the sampling data in the transmission sequence, A /
The accuracy in D conversion can be improved.

(Eleventh Embodiment) The ultrasonic diagnostic apparatus of the eleventh embodiment changes the slope of the ramp wave according to the noise level of the input signal to improve the A / D conversion accuracy. In this device, the ramp wave generator generates a ramp wave whose slope is changed according to the noise amount of the received signal. Other configurations are
It is no different from the device of the ninth embodiment (FIG. 9).

As described in the ninth embodiment, in the pulse Doppler mode, a ramp wave is applied to the echo signal as a pseudo noise signal, so that A /
Although the D conversion accuracy can be improved, however, as in the case of the sixth embodiment, the degree of this effect depends on whether the waveform of the pseudo noise signal matches the noise amount of the input signal. .

To change the waveform of this pseudo noise signal,
Ramp wave is equivalent to changing its slope.

FIG. 14 exemplifies the waveform of the ramp wave generated from the ramp wave generator of this device. 14A corresponds to the waveform (a) of FIG. 6, and FIG. 14B corresponds to the waveform (b) of FIG. Therefore, when the noise is small, the ramp wave (A) having a small slope is used, and when the noise is large, the ramp wave (B) having a large slope is properly used, whereby the improvement of the S / N ratio can be expected.

(Twelfth Embodiment) The ultrasonic diagnostic apparatus of the twelfth embodiment improves the A / D conversion accuracy by changing the slope of the ramp wave according to the frequency component contained in the received signal. In this device, the ramp wave generator changes the slope of the ramp wave to be generated according to the frequency component included in the received signal. The other structure is the same as that of the device of the ninth embodiment (FIG. 9).

When the slope of the ramp wave added to the received signal is changed, the cycle of change in the quantization error changes.
FIG. 12 shows this, and in the case of the waveform of FIG. 12A in which the slope of the ramp wave is small, the quantization error is
As shown by a circle in the lower part of FIG. On the other hand, the slope of the ramp wave is large in FIG.
In the case of the waveform of (B), the quantization error changes in two sampling cycles as indicated by x.

That is, in the case of the ramp wave (A), the frequency of the pseudo noise is 1/4 of the sampling frequency, and in the case of the ramp wave (B), it is 1/2 of the sampling frequency.
Becomes

As is clear from the above description, when the temporal fluctuation of the amplitude of the echo signal is small, the smaller the frequency of the pseudo noise signal is, the more the A / D conversion accuracy is improved. However, if the amplitude of the echo signal fluctuates greatly during the sampling period, improvement in A / D conversion accuracy cannot be expected. Therefore, when the frequency component included in the echo signal is high, it is necessary to use a pseudo-noise waveform with the highest possible frequency so that it does not overlap the frequency band, and when the frequency component included in the echo signal is low. ,
In order to improve the conversion accuracy, it is desirable to use a pseudo noise waveform having a frequency as low as possible.

Therefore, in the apparatus of this embodiment, the ramp wave having a large slope (B) is used when the received signal includes a high frequency, and the slope is used when the received signal includes only a low frequency component. Is used to add to the received signal.

As described above, by properly using the ramp wave depending on the frequency component contained in the received signal, the A / D conversion accuracy can be improved and the S / N ratio can be improved.

[0112]

As is apparent from the above description of the embodiments, the ultrasonic diagnostic apparatus of the present invention removes the pseudo noise signal applied to the received signal by substituting the filter of the delay addition section, It is possible to realize a low-cost ultrasonic diagnostic apparatus having a small circuit scale.

Further, the pseudo noise signal can be completely removed with a small circuit scale by adopting a configuration for canceling the pseudo noise signal.

For a received signal having a high frequency, a pseudo noise signal having a low frequency component is added and A / D converted, and then band limiting is performed to obtain A / D.
The accuracy of D conversion can be improved.

Further, by changing the waveform of the pseudo noise signal added to the received signal according to the noise amount of the received signal, A / D conversion can be performed with optimum accuracy in the noise state.

Even if the amplitude of the received signal is large and the frequency thereof is close to the Nyquist frequency, the phase level of the pseudo noise signal added to the received signal is changed for each transmission sequence, so that the A / D in the pulse Doppler mode is changed. The conversion accuracy can be improved.

In this pulse Doppler mode,
By selecting the directionality of the pseudo noise signal according to the increasing / decreasing tendency of the received signal for each transmission sequence, highly accurate A / D conversion can be realized.

Further, in the pulse Doppler mode, by applying the ramp wave as the pseudo noise signal to the received signal, the A / D conversion accuracy can be improved without generating noise.

Even when the amplitude of the received signal is large and the frequency thereof is close to the Nyquist frequency, the A / D conversion accuracy can be improved by changing the offset amount of this ramp wave for each transmission sequence.

Further, by changing the slope of the ramp wave according to the amount of noise in the received signal and the frequency of the received signal, A / D conversion in the pulse Doppler mode can be performed with high accuracy.

[Brief description of drawings]

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

FIG. 2 is a block diagram showing a configuration of an ultrasonic diagnostic apparatus according to a second embodiment of the present invention,

FIG. 3 is a block diagram showing a configuration of an ultrasonic diagnostic apparatus according to a third embodiment of the present invention,

FIG. 4 is a block diagram showing the configuration of an ultrasonic diagnostic apparatus according to a fourth embodiment of the present invention,

FIG. 5 is a waveform diagram of signals input to and output from an ultrasonic diagnostic apparatus according to a fifth embodiment of the present invention,

FIG. 6 is a waveform diagram of a pseudo noise signal used in an ultrasonic diagnostic apparatus according to a sixth embodiment of the present invention,

FIG. 7 is an explanatory diagram explaining a received signal in the ultrasonic diagnostic apparatus according to the seventh embodiment of the present invention;

FIG. 8 is a waveform diagram of a pseudo noise signal used in the ultrasonic diagnostic apparatus according to the eighth embodiment of the present invention,

FIG. 9 is a block diagram showing the configuration of an ultrasonic diagnostic apparatus according to a ninth embodiment of the present invention,

FIG. 10 is a waveform diagram of a ramp wave used in the ultrasonic diagnostic apparatus according to the tenth embodiment of the present invention,

FIG. 11 is a waveform diagram of a ramp wave used in the ultrasonic diagnostic apparatus of the eleventh embodiment of the present invention,

FIG. 12 is a waveform diagram of a ramp wave used in an ultrasonic diagnostic apparatus according to a twelfth embodiment of the present invention and a diagram showing a pseudo noise period;

FIG. 13 is a waveform diagram of a pseudo noise signal used in a conventional ultrasonic diagnostic apparatus,

FIG. 14 is a block diagram showing the configuration of a conventional ultrasonic diagnostic apparatus,

FIG. 15 is a block diagram showing the configuration of another conventional ultrasonic diagnostic apparatus.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Probe 2-1 to 2-4 Pulser receiver 3-1 to 3-4 Gain control amplifier 4-1 to 4-8 A / D converter 5 Delay addition part 6 Pseudo noise generator 7 Control part 8, 9 Multiplier 10 Reference signal generator 11, 12 Filter 13 Signal processing unit 13-1 to 13-2, 23, 26, 27-1 to 27-4 Switch 14 Detector 15 DSC 16 Display unit 17-1 to 17-8 , 25 Adder 19-1 to 19-4 Delay means (memory) 20-1 to 20-4 Interpolation means 21 Addition means 22 Inverting amplifier 24 Memory 28 Ramp wave generation circuit

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI Technical indication location G01S 7/527 7/536 (72) Inventor Yoshihiko Ito 4-3 Tsunashimahigashi, Kohoku-ku, Yokohama-shi, Kanagawa No. 1 In Matsushita Communication Industrial Co., Ltd. (72) Inventor Yoshito Higashizawa 2-45, Hikosancho, Kanazawa, Ishikawa Prefecture Matsushita Communication Kanazawa Research Institute

Claims (12)

[Claims] 1. A pseudo noise generating means for generating a pseudo noise signal, a plurality of adding means for adding the pseudo noise signal to a received signal, and a plurality of A / D converters for converting the output of each adding means into a digital signal. In the ultrasonic diagnostic apparatus, including: means for delaying and adding outputs of a plurality of A / D converting means, the delay adding means delays the digital data input from each of the A / D converting means. A delay unit for outputting the digital data input from the delay unit, an interpolation unit for interpolating the digital data input from the delay unit with zero, and then outputting the filtered data, and an addition unit for adding the outputs of the plurality of interpolation units. An ultrasonic diagnostic apparatus, wherein a component of the pseudo noise signal is removed by the interpolating means. 2. A pseudo noise generating means for generating a pseudo noise signal, a plurality of adding means for adding the pseudo noise signal to a received signal, and a plurality of A / D converters for converting the output of each adding means into a digital signal. An ultrasonic diagnostic apparatus including means and delay-adding means for delaying and adding outputs of a plurality of A / D converting means, and inverting means for inverting the phase of the pseudo noise signal added to half of the adding means is provided. An ultrasonic diagnostic apparatus characterized by the above. 3. A pseudo noise generating means for generating a pseudo noise signal, a plurality of adding means for adding the pseudo noise signal to a reception signal, and a plurality of A / D conversions for converting the output of each adding means into a digital signal. In an ultrasonic diagnostic apparatus including means and delay-and-add means for delaying and adding outputs of a plurality of A / D conversion means, the phase of the pseudo noise signal added to each of the adding means is switched to a normal phase or a reverse phase. Switching means, a memory for storing the output of the delay adding means when the switching means selects one of the normal phase and the reverse phase, and the switching means selects the other of the normal phase and the reverse phase An ultrasonic diagnostic apparatus comprising: an addition unit that adds the output of the delay addition unit and the data read from the memory at this time. 4. Pseudo noise generating means for generating a pseudo noise signal, a plurality of adding means for adding the pseudo noise signal to a received signal, and a plurality of A / D converters for converting the output of each adding means into a digital signal. In the ultrasonic diagnostic apparatus including means and delay-and-add means for delaying and adding outputs of a plurality of A / D conversion means, the addition of the pseudo noise signal to one received signal is 2n
The ultrasonic diagnostic apparatus is characterized in that an inverting means for inverting the phase of the pseudo noise signal added to half of the 2n adding means is provided while being performed by the adding means. 5. A pseudo noise generating means for generating a pseudo noise signal, a plurality of adding means for adding the pseudo noise signal to a reception signal, and a plurality of A / D conversions for converting the output of each adding means into a digital signal. In an ultrasonic diagnostic apparatus including means and delay adding means for delaying and adding outputs of a plurality of A / D converting means, the frequency of the pseudo noise signal is set to a low frequency band that does not overlap with the frequency of the received signal. Together with the above A /
An ultrasonic diagnostic apparatus comprising band limiting means for limiting the band of the output signal of the D conversion means. 6. A pseudo noise generating means for generating a pseudo noise signal, a plurality of adding means for adding the pseudo noise signal to a received signal, and a plurality of A / D converters for converting the output of each adding means into a digital signal. An ultrasonic diagnostic apparatus comprising: means for delaying and adding outputs of a plurality of A / D conversion means, wherein the waveform of the pseudo noise signal is changed according to the noise amount of the received signal. Ultrasonic diagnostic equipment. 7. A pseudo noise generating means for generating a pseudo noise signal, a plurality of adding means for adding the pseudo noise signal to a reception signal, and a plurality of A / D converters for converting the output of each adding means into a digital signal. An ultrasonic diagnostic apparatus comprising: means and delay-adding means for delaying and adding outputs of a plurality of A / D converting means, wherein the phase of the pseudo noise signal is changed according to a transmission sequence of a reception signal. Sound wave diagnostic equipment. 8. When the amplitude of the received signal slightly increases as the transmission sequence increases, the phase of the pseudo noise signal decreases as the transmission sequence increases, and the amplitude of the received signal increases as the transmission sequence increases. The ultrasonic diagnostic apparatus according to claim 7, wherein the phase of the pseudo noise signal is increased as the number of transmission sequences increases when the ultrasonic diagnostic signal slightly decreases. 9. A pseudo noise generating means for generating a pseudo noise signal, a plurality of adding means for adding the pseudo noise signal to a received signal, and a plurality of A / D converters for converting the output of each adding means into a digital signal. In the ultrasonic diagnostic apparatus, which is provided with a means and a delay adding means for delaying and adding outputs of a plurality of A / D converting means, the pseudo noise generating means generates a ramp wave as a pseudo noise signal. Ultrasonic diagnostic equipment. 10. The ultrasonic diagnostic apparatus according to claim 9, wherein the offset of the ramp wave is changed for each transmission sequence. 11. The ultrasonic diagnostic apparatus according to claim 9, wherein the slope of the ramp wave is changed according to the noise amount of the received signal. 12. The ultrasonic diagnostic apparatus according to claim 9, wherein the slope of the ramp wave is changed according to the frequency of the received signal.