JPH04341251A - Ultrasonic diagnostic device - Google Patents

Abstract

PURPOSE:To execute the observation of a diagnostic image in a real time by a simple constitution without deteriorating the distance resolution. CONSTITUTION:By a transmitting waveform generator 23, a transmitting signal subjected to pulse magnifying is generated, and by driving an ultrasonic vibrator 1, an ultrasonic wave is transmitted and received to and from a body to be examined. A receiving signal of the ultrasonic vibrator 1 is inputted to a correlation filter (1) 17, and a correlation filter (2) 18. The receiving signal inputted to the respective correlation filters is stored in a line memory (1) 27 or a line memory (2) 28 at every one scanning line, and a correlational operation of the present receiving signal and the receiving signal of one scanning line before is executed by a product sum arithmetic circuit 29. An output of the correlation filter (1) 17 and the correlation filter (2) 18 is inputted to a DSC 20, converted to a video signal by this DSC 20 and displayed as an ultrasonic diagnostic image on a monitor 21.

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 using a pulse compression method.

0002

[Prior art] Using an ultrasonic transducer, ultrasonic pulses are transmitted into a living body, and the echoes reflected by the living tissue are received again by the ultrasonic transducer, converted into electrical signals, and processed. 2. Description of the Related Art Various ultrasonic diagnostic devices that form and display tomographic images inside a living body are in use.

[0003]More recently, an ultrasonic diagnostic apparatus has been proposed which is capable of improving distance resolution and sensitivity by using a pulse compression method that has been put into practical use in the field of radar.

[0004] An ultrasonic diagnostic apparatus using such a pulse compression method, for example as disclosed in Japanese Unexamined Patent Publication No. 2-264858, transmits a coded pulse to a subject and combines a received signal and a reference signal. Some devices perform pulse compression by performing a correlation calculation with a kernel signal. Furthermore, in the ultrasonic diagnostic apparatus disclosed in Japanese Patent Application Laid-Open No. 1-304376, the length of the transmitted signal is changed according to the distance to the subject through which the ultrasound waves travel, and the length of the transmitted signal is adjusted to correspond to the received signal and the transmitted signal. The optimum diagnostic image corresponding to the distance is obtained by performing a correlation calculation with the reference signal and performing pulse compression. Further, an ultrasonic diagnostic apparatus has been proposed that performs pulse compression by performing a correlation calculation by switching a reference signal depending on the frequency of the ultrasonic wave and the attenuation characteristics of the subject.

[0005] Ultrasonic waves attenuate depending on the distance, and the transmitted and received signals shift to a lower frequency range, so as the depth of the object increases, the correlation becomes harder to establish. That is, the correlation deteriorates due to deterioration of the frequency band characteristics. This decrease in correlation causes an increase in temporal side lobes, leading to a problem in that the detection ability on the time axis, that is, the distance resolution decreases. Therefore, in the conventional ultrasonic diagnostic apparatus, the resolution is improved by changing the reference signal and performing correlation calculation by changing the value of the resistor string, the pattern on the ROM, etc.

[0006]

[Problems to be Solved by the Invention] However, in conventional ultrasonic diagnostic equipment, it is possible to prevent a decrease in resolution when the subject exhibits uniform attenuation characteristics depending on the distance; does not exhibit uniform attenuation characteristics in vivo, etc., so it has not always been possible to prevent a decrease in resolution.

[0007] Furthermore, when switching the resistor strings, if switching is performed while a signal is being received, switching noise will occur. Methods such as switching between transmitting and receiving are used. This reduces the frame rate and
Problems arise in that diagnostic images cannot be observed in real time, such as inability to obtain good diagnostic images of organs that move quickly. Furthermore, the circuit becomes complicated because the resistor strings are switched.

The present invention has been made in view of these circumstances, and it is an object of the present invention to provide an ultrasonic diagnostic apparatus capable of observing diagnostic images in real time with a simple configuration without reducing distance resolution. It is an object.

[0009]

[Means for Solving the Problems] An ultrasonic diagnostic apparatus according to the present invention includes an ultrasonic probe that transmits and receives ultrasonic waves, and a probe driving means that drives the ultrasonic probe with a pulse-stretched signal. , a correlation comprising at least two storage means for storing received signals of the ultrasound probe for each scanning line, and performing a correlation calculation between the current received signal and the previous received signal stored in these storage means. The apparatus includes a calculation means and an image display means for displaying the output of the correlation calculation means as an ultrasonic diagnostic image.

0010

[Operation] The ultrasonic probe is driven by a pulse-stretched signal by the probe driving means, and ultrasonic waves are transmitted and received by the ultrasonic probe. The correlation calculation means stores the reception signal of the ultrasonic probe for each scanning line by the storage means, and performs a correlation calculation between the current reception signal and the previous reception signal stored in the storage means. Then, the image display means displays the output of the correlation calculation means as an ultrasonic diagnostic image.

[0011]

Embodiments Hereinafter, embodiments of the present invention will be described with reference to the drawings. 1 to 3 relate to a first embodiment of the present invention, in which FIG. 1 is a block diagram showing the configuration of an ultrasonic diagnostic apparatus, FIG. 2 is an explanatory diagram showing the configuration of an ultrasound probe, and FIG. 3 is the tip of FIG. 2. It is a cross-sectional explanatory view showing details of the section.

As shown in FIG. 1, an ultrasonic transducer 1 that transmits and receives ultrasonic waves is connected to a transmitting amplifier 4 and a multiplier via a signal line 3 provided in a drive transmitting section 2 composed of a flexible shaft or the like. It is connected to a multiplier (1) 5 and a multiplier (2) 6. The ultrasonic transducer 1, as shown in FIG.
The ultrasonic probe 7 as an ultrasonic probe is provided within a sheath 11 having an acoustic window portion 11 a that transmits ultrasonic waves at the tip thereof, and is connected to the drive transmission portion 2 . The drive transmission unit 2 is mechanically connected to a motor 9 and an encoder 10 via a gear 8, and when the motor 9 rotates, the ultrasonic transducer 1 rotates to perform mechanical radial scanning. It has become. Further, the encoder 10 detects the amount of rotation of the ultrasonic transducer 1, that is, the position of the ultrasonic scanning line. As shown in FIG. 3, the tip of the ultrasonic probe 7 has a sheath 11 filled with a liquid 12 such as physiological saline, and a transducer unit attached to a support frame 13 connected to the drive transmission section 2. 1a is placed. This vibrator unit 1a is connected to a signal line 3 within the drive transmission section 2.

The multiplier (1) 5 is a local oscillator 15
The output signal is supplied via a 90° phase shifter 16. Further, the output signal of the local oscillator 15 is directly supplied to the multiplier (2) 6. The outputs of the multiplier (1) 5 and multiplier (2) 6 are supplied to a correlation filter (1) 17 and a correlation filter (2) 18, respectively, as correlation calculation means. The outputs of these correlation filters (1) 17 and (2) 18 are input to an adder 19, and the output of this adder 19 is input to a digital scan converter (DS).
C) 20. The DSC 20 converts the received signal into an image signal suitable for a display device, and is connected to a monitor 21 that displays a diagnostic image of the subject. The DSC 20 and monitor 21 constitute an image display means.

The output of the encoder 10 is supplied to a timing control circuit 22, and a control signal from this timing control circuit 22 is sent to a transmission waveform generator 23, a DSC 20, and a correlation filter (1) 17 and a correlation filter (2) 18.
The timing of each is controlled. The transmission waveform generator 23 generates a transmission wave to be transmitted to the subject, and a pulse-expanded signal such as an FM chirp signal or a coded signal is input to the transmission amplifier 4. The timing control circuit 22, the transmission waveform generator 23, and the transmission amplifier 4 constitute a probe driving means.

The correlation filter (1) 17 and the correlation filter (2) 18 have the same configuration, and only the correlation filter (1) 17 will be explained here. The correlation filter (1) 17 is provided with an A/D converter 25 to which the output of the multiplier (1) 5 is supplied. The output of the A/D converter 25 is input to a line memory (1) 27 or a line memory (2) 28 as a storage means via a changeover switch 26 for each scanning line. The outputs of line memory (1) 27 and line memory (2) 28 are each supplied to a product-sum calculation circuit 29, where a correlation calculation is performed and the output is input to an adder 19. ing. Note that the switching timing of the changeover switch 26 is controlled by the timing control circuit 22.

Next, the operation of this embodiment will be explained. The drive transmission unit 2 is rotationally driven by the motor 9, and the signal line 3 is rotated together with the ultrasonic transducer 1. The amount of rotation of the ultrasonic transducer 1 is detected by an encoder 10 provided coaxially with the motor 9, and a detection signal is input to the timing control circuit 22. The timing control circuit 22 generates a signal for controlling the timing of each part based on the detection signal from the encoder 10. As signals for controlling this timing, a transducer drive start signal is supplied to the transmission waveform generator 23, and an ultrasonic scanning line position signal is supplied to the DSC 20. The transmission waveform generator 23 generates a pulse-expanded transmission signal, and the transmission amplifier 4 amplifies this transmission signal. The transmission amplifier 4 supplies an output signal to the ultrasonic transducer 1 via the signal line 3 to drive the ultrasonic transducer 1. As a result, ultrasonic waves are transmitted to the subject.

The ultrasonic waves transmitted to the subject are reflected and returned to the ultrasonic transducer 1, where they are received and converted into electrical signals, which are transmitted via the signal line 3 to the multiplier (1) 5, and Multiplier (
2) Input in 6. Multiplier (1) 5, Multiplier (2
) 6 is multiplied by the signal of the local oscillator 15 to be band-converted to a low frequency band, and
A phase difference is generated by the 90° phase shifter 16 and converted into mutually orthogonal signals, which are input to a correlation filter (1) 17 and a correlation filter (2) 18.

In the correlation filter (1) 17, first, the A/D converter 25 converts the signal from the multiplier (1) 5 into a digital signal. The output of the A/D converter 25 is switched by a changeover switch 26 whose timing is controlled by the timing control circuit 22, and the output is switched between line memory (1) 27 or line memory (2).
) 28 stores received signal data for one scanning line. Here, line memory (1) 27 and line memory (2) are selected for each scanning line by switching switch 26.
Received signal data is stored alternately in 28. Then, the product-sum calculation circuit 29 performs a correlation calculation between the current received signal data and the received signal data one scanning line before. Similarly, in the correlation filter (2) 18, the multiplier (2)
Based on the signal from 6, a correlation calculation is performed between the current received signal data and the received signal data one scanning line before.

The outputs after the correlation calculations of the correlation filter (1) 17 and the correlation filter (2) 18 are sent to the adder 1.
9 converts the signal into a high frequency band again and inputs it to the DSC 20. Then, the DSC 20 converts the ultrasonic scanning line position signal from the timing control circuit 22 into an image signal suitable for a display device, and displays an ultrasonic diagnostic image on the monitor 21.

In this way, instead of performing correlation calculation using the reference signal, pulse compression is performed by taking the autocorrelation with the previous received signal data for each scanning line, so that high correlation can be achieved in correlation calculation. You can get sex. Therefore, it is possible to prevent deterioration of frequency band characteristics due to ultrasonic attenuation even in a subject that does not exhibit uniform attenuation characteristics such as in a living body, thereby preventing a decrease in correlation and a decrease in distance resolution. can be prevented. In addition, since pulse compression is performed without switching the reference signal resistor string, etc., the circuit can be simplified, making it possible to observe diagnostic images in real time even in diagnostic images of fast-moving organs. becomes.

4 to 9 relate to a second embodiment of the present invention, FIG. 4 is a block diagram showing the configuration of an ultrasonic diagnostic apparatus, and FIG. 5 is an explanatory diagram showing a first example of the tip of an ultrasonic probe. , FIG. 6 is an explanatory cross-sectional diagram of a piezoelectric element, FIG. 7 is an explanatory diagram showing a second example of an ultrasonic probe tip, FIG. 8 is an explanatory diagram showing a third example of an ultrasonic probe tip, and FIG. 9 is an explanatory diagram showing a third example of an ultrasonic probe tip. FIG. 7 is an explanatory diagram showing a fourth example of an ultrasonic probe tip.

As shown in FIG. 4, in the second embodiment, a piezoelectric element 31 is provided around the ultrasonic vibrator 1 instead of an encoder for detecting the amount of rotation of the ultrasonic vibrator 1. It is designed to detect the position of. Piezoelectric element 31
An amplifier 32 is connected to the A/D
It is designed to be supplied to a converter 33. A/D
The output of the converter 33 is supplied to the DSC 20 and the changeover switches in the correlation filter (1) 17 and the correlation filter (2) 18. Further, a control circuit 34 for controlling the driving timing of the ultrasonic transducer 1 is provided, and transmits control signals to the waveform generator 23 and the DSC 20.
It is designed to output to . Other pulse compression circuits such as a correlation filter are constructed in the same manner as in the first embodiment, and their explanation will be omitted.

A first example of an ultrasonic probe having the piezoelectric element 31 at its tip is shown in FIG. An ultrasonic transducer 1 is provided within the sheath 35, and a drive transmission section 2 is connected to the ultrasonic transducer 1. Opening surface 36 of the ultrasonic transducer 1
A piezoelectric element 31 made of polyvinylidene fluoride (PVDF) or the like is provided along the inner periphery of the sheath 35 so as to face the piezoelectric element 31 . The piezoelectric element 31 has different shapes (opening areas) in the circumferential direction of the sheath 35, and is connected to the amplifier 32 via a signal line 37. As shown in FIG. 6, the piezoelectric element 31 has a flexible sheet-like PVDF 38, and electrodes 39 are provided on both sides of the PVDF 38, which has been polarized by applying a high voltage. It is configured to be able to receive. Further, the electrode 39
A signal line 37 is connected to. By receiving a portion of the transmitted ultrasonic waves by the piezoelectric elements 31 having different opening areas in the circumferential direction, a voltage corresponding to the position of the opening surface 36 of the ultrasonic transducer 1 is outputted. There is.

As a second example of the tip of the ultrasonic probe, a piezoelectric element 41 whose opening area changes stepwise in the circumferential direction of the sheath 35 can be provided as shown in FIG.

A third example of the tip of the ultrasonic probe is shown in FIG. In the third example, an ultrasonic transducer 44 having a transducer 42 for ultrasonic diagnosis and a transducer 43 for position detection is provided. Piezoelectric elements 31 having different opening areas in the circumferential direction are provided along the inner periphery of the sheath 35 so as to face the position detection vibrator 43. The rest of the configuration is the same as in the first example.

A fourth example of the tip of the ultrasonic probe is shown in FIG. In the fourth example, the ultrasonic transmitting part 45 at the distal end of the sheath 35 is made of PVDF, and a position detection receiver with different opening areas in the circumferential direction is arranged so as to face the opening surface 36 of the ultrasonic transducer 1. A corrugated portion 46 is provided. This position detection wave receiving section 46 is formed by providing electrodes so that the opening areas differ in the circumferential direction, or by performing polarization processing so that the opening areas differ in the circumferential direction. By receiving a portion of the transmitted ultrasonic waves by the position detection wave receiving section 46, a voltage corresponding to the position of the aperture surface 36 of the ultrasonic transducer 1 is output.

When the diameter of the ultrasonic probe is reduced in order to observe the inside of a narrow lumen, the drive transmission section 2 also becomes smaller in diameter, and the rotation followability of the ultrasonic transducer 1 deteriorates. For this reason,
When detecting the position of the ultrasonic scanning line by detecting the amount of rotation of the ultrasonic transducer 1, if the amount of rotation of the ultrasonic transducer 1 is detected by an encoder connected to the motor, the actual ultrasonic wave will be detected. The amount of rotation of the vibrator 1 and the output of the encoder no longer match, resulting in a deviation in position detection. Due to this deviation, there is a problem that deterioration such as distortion occurs in the image when forming an ultrasonic diagnostic image. Therefore, in the second embodiment, the rotational position of the ultrasonic transducer 1 is accurately determined by receiving a portion of the ultrasonic waves transmitted from the ultrasonic transducer 1 using piezoelectric elements 31 having different opening areas in the circumferential direction. I'm trying to detect it.

The drive transmission section 2 is rotationally driven by the motor 9, and the ultrasonic transducer 1 is rotated. The control circuit 34 outputs the vibrator drive control signal to the transmission waveform generator 23, which causes the transmission waveform generator 23 to generate a pulse-expanded transmission signal. Then, the ultrasonic transducer 1 is transmitted through the transmitting amplifier 4.
is driven to transmit ultrasonic waves to the subject. While the transmitted ultrasound waves travel toward the subject, a portion of them is received by the piezoelectric element 31 . Here, since the opening area of the piezoelectric element 31 through which the ultrasonic waves are received differs in the circumferential direction, the output voltage differs depending on the position of the opening surface 36 of the ultrasonic vibrator 1. Since the piezoelectric element 31 is located near the ultrasonic transducer 1, the ultrasonic waves do not spread on the piezoelectric element 31, and a voltage corresponding to an accurate rotational position is output. This output voltage is input to the amplifier 32 via the signal line 37, and the A/D converter 3
3, the ultrasonic transducer 1 is converted into a digital signal to obtain a position signal indicating the rotational position of the ultrasonic transducer 1. This position signal is supplied to the changeover switch 26 in the correlation filter (1) 17 and the correlation filter (2) 18, and the received signal is switched every scanning line and is alternately sent to the line memory (1) 27, line memory (2) Stored in 28. Further, the position signal is inputted to the DSC 20 as a scanning line position signal. On the other hand, the drive timing of the ultrasonic transducer 1 is controlled by the control circuit 3.
4 independently generated. This ultrasonic transducer 1
An image signal at an accurate scanning line position is generated based on the driving timing of the ultrasonic transducer 1 and the rotational position of the ultrasonic transducer 1 detected by the piezoelectric element 31.

[0029] In this manner, by receiving a portion of the ultrasonic waves transmitted to the subject with the piezoelectric element, it is possible to accurately detect the rotational position of the ultrasonic transducer. This results in
Even when the rotational position of the ultrasound transducer does not match the drive amount, such as when the diameter of the ultrasound probe is reduced, it is possible to obtain good ultrasound diagnostic images without image deterioration based on accurate scanning line position information. Obtainable.

Other functions and effects are similar to those of the first embodiment.

Note that quadrature detection, which converts the received signal of the ultrasonic transducer into a quadrature signal, is not only carried out as an analog signal as in this embodiment, but also digitally by converting it into a digital signal and performing calculations. You can also do this. This allows the local oscillator to be simplified.

Further, the DSC may write a digital signal into the frame memory and convert it into an image signal, or may convert it into an analog signal and then convert it into an image signal. If the digital signals are written into the frame memory as they are, good diagnostic images can be obtained without deterioration in image quality. When processing is performed after converting to an analog signal, DSC compatibility can be maintained without using a processing method such as pulse compression.

[0033]

As explained above, according to the present invention, since pulse compression is performed by taking the autocorrelation with the previous received signal data for each scanning line, the distance resolution is not reduced. This has the effect of making it possible to observe diagnostic images in real time with a simple configuration.

[Brief explanation of drawings]

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

[Figure 2] Explanatory diagram showing the configuration of an ultrasound probe

[Fig. 3] Cross-sectional explanatory diagram showing details of the tip part in Fig. 2

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

[Fig. 5] Explanatory diagram showing a first example of the tip of the ultrasound probe

[Figure 6] Cross-sectional diagram of piezoelectric element

[Fig. 7] Explanatory diagram showing a second example of the tip of the ultrasonic probe

[Fig. 8] Explanatory diagram showing a third example of the tip of the ultrasound probe

FIG. 9 is an explanatory diagram showing a fourth example of the tip of the ultrasonic probe.

[Explanation of symbols]

1...Ultrasonic vibrator 5, 6...multiplier 15...Local oscillator 16...90° phase shifter 17, 18... Correlation filter 19... Adder 20...DSC 21...Monitor 22...Timing control circuit 23...Transmission waveform generator 26...Switch switch 27, 28...line memory 29...product-sum calculator

Claims (1)

[Claims] [Claim 1] An ultrasonic probe that transmits and receives ultrasonic waves;
A probe driving means for driving the ultrasonic probe with a pulse-stretched signal, and at least two storage means for storing the received signal of the ultrasonic probe for each scanning line, and these storage means The apparatus is characterized by comprising a correlation calculation means for performing a correlation calculation between the current reception signal and the previous reception signal stored in the apparatus, and an image display means for displaying the output of the correlation calculation means as an ultrasound diagnostic image. Ultrasound diagnostic equipment.