JP3530681B2 - Ultrasound imaging device - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ultrasonic imaging method and apparatus, and more particularly to an ultrasonic imaging method and apparatus for imaging a fluoroscopic image of a portion of a subject deeper than a predetermined cross section.

[0002]

2. Description of the Related Art As a technique for ultrasonically imaging a fluoroscopic image of a portion of a subject deeper than a predetermined cross section, for example, Japanese Patent Publication No. 8-1
A reflection transmission imaging method (RTI (Reflex Transmission Imaging)) as described in Japanese Patent No. 6700 is known.

In this method, a predetermined cross section of a subject is two-dimensionally scanned with an ultrasonic beam focused on the cross section, a signal corresponding to an echo from a region behind the cross section is extracted from an echo reception signal, and Based on this, a C mode image is generated. This makes it possible to obtain an image (reflection / transmission image) in which the region behind the cross section is seen through in the irradiation direction of the ultrasonic beam.

In order to extract the echo from the area behind the cross section, the echo received signal is ranged over a predetermined range on the time axis corresponding to the area behind the cross section.
ate), envelope detection, and integration over the range gate interval. Then, this section integration value becomes image data of one pixel of the perspective image.

[0005]

In order to properly extract the echo from the area behind the cross section, it is necessary to adjust the position of the range gate according to the depth of the cross section. Also, the integration interval must be adjusted according to the position of the range gate. That is, in the prior art, it is necessary to control the range gate or the like according to the depth of the cross section in order to extract a desired echo.

The present invention has been made to solve the above-mentioned problems, and an object thereof is to realize an ultrasonic imaging method and apparatus for performing reflection / transmission imaging without a range gate.

It is known that when an ultrasonic beam is focused on a focus, harmonics of the transmitted ultrasonic wave are generated in the focused sound field. This phenomenon is called the nonlinear effect of the focused sound field. Proceedings of the Acoustical Society of Japan, pp. 1009-101
According to No. 0 (1996.3), the sound pressure of the second harmonic becomes the maximum in the forward direction of the ultrasonic wave from the position where the sound pressure of the fundamental wave becomes the maximum, and the sound pressure of the third harmonic becomes higher. Is further reported to be the largest in front of it.

The position where the sound pressure of the fundamental wave is maximum corresponds to the focal point of the ultrasonic beam. Therefore, the front of the ultrasonic wave traveling direction at this position means farther than the focal point. That is, the second harmonic is generated in a region deeper than the focal point of the ultrasonic beam, and the third harmonic is generated further behind. The present invention is
The nonlinear effect of the focused sound field of the ultrasonic wave is applied.

[0009]

[Means for Solving the Problems]

[1] A first invention for solving the problem is to two-dimensionally scan a predetermined cross section of a subject with an ultrasonic beam focused on the cross section, receive an echo, and obtain a harmonic component of the echo. It is an ultrasonic imaging method characterized by generating a C-mode image based on the above.

According to the first invention for solving the problem, the fact that the harmonics of the transmitted ultrasonic wave are generated in the region behind the cross section due to the nonlinear effect of the focused sound field is utilized, and the echo of this harmonic component is utilized. Since the C-mode image is generated based on the above, it is possible to naturally obtain a perspective image of the area behind the cross section. That is, it is possible to realize an ultrasonic imaging method for performing reflection / transmission imaging without a range gate.

In the first invention for solving the problem, it is preferable that the higher harmonic component is a second higher harmonic component in order to perform imaging using a contrast agent. [2] A second invention for solving the problem is an ultrasonic wave transmitting / receiving means for two-dimensionally scanning with an ultrasonic beam focused on a predetermined cross section of an object to receive an echo, and the ultrasonic wave transmitting / receiving means. And an image generating unit for generating a C-mode image based on the harmonic component of the echo received by the unit.

According to the second invention for solving the problem, the fact that the harmonics of the transmitted ultrasonic wave are generated in the region behind the cross section due to the nonlinear effect of the focused sound field is utilized, and the echo of this harmonic component is utilized. Since the C-mode image is generated based on the above, it is possible to naturally obtain a perspective image of the area behind the cross section. That is, it is possible to realize an ultrasonic imaging apparatus that performs reflection / transmission imaging without a range gate.

In the second invention for solving the problem, it is preferable that the higher harmonic component is the second higher harmonic component in order to perform imaging using a contrast agent. [3] A third invention for solving the problem is to provide an ultrasonic probe that transmits ultrasonic waves to a subject and receives ultrasonic echoes from the subject, and through the ultrasonic probe. Transmitting and receiving means for two-dimensionally scanning an ultrasonic beam focused on a predetermined cross section of the subject to receive an echo; and signal extracting means for extracting a second harmonic component of the echo received by the transmitting and receiving means, C based on the output signal of the signal extraction means
An ultrasonic imaging apparatus comprising: an image generating unit that generates a mode image.

According to the third invention for solving the problem, the fact that the second harmonic of the transmitted ultrasonic wave is generated in the region behind the cross section due to the nonlinear effect of the focused sound field is utilized.
Since the C-mode image is generated based on the echo of the harmonic component, the perspective image of the region behind the cross section can be obtained naturally. That is, it is possible to realize an ultrasonic imaging apparatus that performs reflection / transmission imaging without a range gate.

In the third invention for solving the problem, it is preferable that the signal extracting means uses a bandpass filter in order to simplify the configuration. In the third invention for solving the problem, it is preferable that the signal extracting means uses a quadrature detection circuit.
It is preferable in that the signal extraction is performed accurately.

[0016]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. The present invention is not limited to the embodiment.

FIG. 1 is a block diagram of the ultrasonic imaging apparatus.
The figure is shown. This device is an example of an embodiment of the present invention.
It should be noted that the configuration of the present apparatus shows an example of an embodiment relating to the apparatus of the present invention. The operation of the present apparatus also shows an example of an embodiment relating to the method of the present invention. The same applies to other examples of the embodiment of the present device.

As shown in FIG. 1, an ultrasonic probe
e) 10 is adapted to irradiate a predetermined cross section 22 in the subject 14 with an ultrasonic beam 20 that focuses on a focal point F. To form such an ultrasonic beam 20, for example, a concave disk vibrator is used as an ultrasonic vibrator, an acoustic lens is combined with a flat disk vibrator, or a plurality of concentric ring vibrators or One-dimensional or two-dimensional array
It can be realized by operating a plurality of transducers forming an (array) as a phased array. The ultrasonic probe 10 is an example of an embodiment of the ultrasonic probe according to the present invention.

FIG. 2A shows an example in which an acoustic lens 102 is combined with a vibrator 101 having a flat disk shape. (B), (c) and (d) of the same figure respectively show a plurality of transducers 101 forming a concentric ring, a combination of a plurality of transducers 101 and an acoustic lens 102 forming a one-dimensional array, and a two-dimensional array. An example of a plurality of vibrators 101 that form a.

A concave disk-shaped oscillator is preferable in that a focused ultrasonic beam can be easily obtained. A combination of a flat disk vibrator and an acoustic lens is preferable because the focus can be changed by exchanging the acoustic lens. A phased array using a plurality of transducers forming a concentric ring or a plurality of transducers forming a one-dimensional or two-dimensional array has a focus (focus (f
ocus)) is preferable because it can be freely adjusted by electrical means.

In addition, the one-dimensional or two-dimensional phased array has a direction (beam steering (bea steering)
m steering)) is also preferable in that it can be freely adjusted by electric means. With the one-dimensional phased array, beam steering can be performed in one axis direction. According to the two-dimensional phased array, beam steering can be performed in two axis directions orthogonal to each other.

The ultrasonic beam 20 is emitted from the scanning actuator (a
A ctuator) 24 scans in the xy directions in the drawing. As a result, the focal point F of the ultrasonic beam 20 scans the cross section 22 two-dimensionally. The two-dimensional scanning by the scanning actuator 24 is performed by mechanical scanning, electrical scanning or a combination of mechanical scanning and electrical scanning.

Mechanical scanning is carried out when a concave disk oscillator, a combination of a flat disk oscillator and an acoustic lens, or a plurality of oscillators forming a concentric ring are used. In this case, the ultrasonic beam 20 is scanned in the xy directions by mechanically moving the ultrasonic probe 10. Electrical scanning is performed when a two-dimensional phased array is used. in this case,
Ultrasonic beam 20 by electric beam steering
Are scanned in the xy directions. The combination of mechanical scanning and electrical scanning is performed when a one-dimensional phased array is used. In this case, for example, scanning in the y direction is performed by the ultrasonic probe 1.
It is performed by mechanically moving 0, and scanning in the x direction is performed by electric beam steering.

The two-dimensional scanning of the ultrasonic beam is performed under the control of the control unit 28.
The control unit 28 controls the pulsar 16 in synchronization with the two-dimensional scanning of the ultrasonic beam 20 to output a drive pulse for transmitting the ultrasonic beam 20.

The frequency of the drive pulse is adjusted to the center frequency f ₀ of the ultrasonic transducer. At this time, a bandpass filter (frequency bandpass filter) for the frequency f _{0 is} output to the output side of the pulsar 16.
lter) is preferable in that the drive pulse does not include harmonic components.

The output pulse of the pulser 16 is T / R (transmi
The ultrasonic wave is applied to the ultrasonic probe 10 through the (t / receive) switch 18, and the ultrasonic transducer is vibrated to transmit an ultrasonic wave as indicated by a signal 52 in FIG.

The pulsar 16 used corresponds to the oscillator configuration of the ultrasonic probe 10. That is, a pulser having a single output channel is used for a single-plate transducer such as a concave disk or a flat disk. In the case of a phased array oscillator, multiple pulsers with multiple output channels are used. In this case, the output pulse of each channel is provided with a time difference for focusing the beam. In the case of a one-dimensional or two-dimensional array, a time difference for beam steering is also added.

The transmitted ultrasonic beam 20 is focused on the focal point F on the cross section 22. At this time, due to the above-mentioned non-linear effect, a harmonic wave is generated in the area Z behind the focus F.
The harmonics are mainly composed of the second harmonic and the third harmonic.

An echo for the transmitted ultrasonic wave is returned to the ultrasonic probe 10. The echo contains a harmonic component in addition to the fundamental wave component of the transmitted ultrasonic wave. The harmonic echo is mainly returned from the area Z that is deeper than the cross section 22.

The echo is received by the ultrasonic probe 10,
The echo reception signal is input to the signal processing unit 30 via the T / R switch 18. In the signal processing unit 30, the echo reception signal is amplified by the variable gain amplifier 34. The gain of the variable gain amplifier 34 is controlled by the output signal of the gain function generator 36, and increases with the elapse of the reception time of the echo signal. As a result, the so-called TGC (t
ime-gain control) is performed, and the echo attenuation correction is performed according to the echo return time, that is, the depth of the reflection point.
The gain function generator 36 is controlled by the controller 28.

The ultrasonic probe 10, the scanning actuator 24, the pulser 16, the T / R switch 18 and the variable gain amplifier 34 are an example of the ultrasonic transmitting / receiving means or the transmitting / receiving means according to the present invention.

The output signal of the variable gain amplifier 34 is adapted to be filtered by the bandpass filter 38. The band of the bandpass filter 38 is adjusted to the second harmonic 2f ₀ , for example. As a result, for example, the second harmonic component is extracted from the echo reception signal as shown by the signal 56 in FIG.

The second harmonic echo returns after time T4, which is later than time T3 when the echo from the focus F returns. The signal duration after time T4 corresponds to the length of the area Z.

The output signal of the bandpass filter 38 is envelope-detected by the envelope detection circuit 40, as indicated by the signal 58 in FIG. 3, for example. The bandpass filter 38 and the envelope detection circuit 40 are an example of the embodiment of the signal extraction means in the present invention. The output signal of the envelope detection circuit 40 is input to the integrator 42 and integrated as shown by the signal 60 in FIG. 3, for example. This causes the second harmonic echo to be integrated over the entire length of region Z.

After the time T5 corresponding to the rear end of the area Z, the second harmonic echo almost disappears and the increase of the integrated output stops. At this point, the control of the retainer 44 is performed by the controller 28, as indicated by the signal 62 in FIG.
The integrated output is held in the holder 44. Thereafter, for example, as shown by the signal 64 in FIG.
2 is reset.

The output signal of the holder 44 is input to the scan converter 46. Under the control of the controller 28, the scan converter 46 stores this input signal in a memory (not shown) as image data of one pixel of the C mode image. The position of the pixel corresponds to the two-dimensional position of the focal point F on the cross section 22.

Here, the image data is the image data of the area Z at the back of the cross section 22. Moreover, it is the area Z
Since it is integrated over the entire length of, the data represents the perspective image of the region Z viewed through the focus F. That is,
The data for one pixel of the fluoroscopic image is obtained by transmitting and receiving the ultrasonic beam 20 once. Band pass filter 38, envelope detection circuit 40, integrator 42, holder 44
The scan converter 46 is an example of an embodiment of the image generating means of the present invention.

The transmission and reception of ultrasonic waves as described above are repeated while the position of the focal point F is successively moved (two-dimensional scanning) on the cross section 22 by the scanning actuator 24. As a result, the fluoroscopic image data for the area Z behind each point on the cross section 22 is sequentially obtained, and when the two-dimensional scanning is completed, the image transilluminating the area behind the cross section 22, that is, the reflection / transmission image is a scan converter. Completed in 46 memories.

The reflection / transmission image is scanned and changed in the scanning converter 46 according to the scanning system of the display 48, and is displayed on the display 48 as a visible image. The display operation of the display 48 is controlled by the control unit 28.

In this way, by utilizing the second harmonic, the reflection / transmission image can be picked up without the need for a range gate as in the prior art. Since the range gate is not performed, it is possible to capture a perspective image of the region behind it without requiring any adjustment, no matter how the depth of the cross section is changed.

Even when the band pass filter 38 is for the third harmonic and image data is formed by the third harmonic, the reflection / transmission image of the inner portion of the cross section 22 can be similarly picked up.

In the imaging using the second harmonic, a contrast agent having a resonance absorption property with respect to a specific ultrasonic frequency, such as a microcapsule type contrast agent, is used to perform contrast imaging of a region of interest. It is particularly effective in some cases.

FIG. 4 shows another example of the embodiment of the present invention. The same parts as those in FIG. 1 are designated by the same reference numerals and the description thereof will be omitted. The part different from FIG. 1 is a quadrature detection circuit 51, low-pass filters 52 and 52 ′ as signal extraction means,
The point is that the complex absolute value circuit 53 is used.

Reference of the quadrature detection circuit 51
ce) signal is provided from the control unit 28. The control unit 28 controls the frequency f of the driving pulse of the pulsar 16.
A reference signal obtained by multiplying ₀ by 2f ₀ is supplied to the quadrature detection circuit 51. When extracting the third harmonic, the reference signal multiplied by 3f ₀ is supplied.

The quadrature detection circuit 51 quadrature-detects the output signal of the variable gain amplifier 34 based on the reference signal,
The in-phase component i and the quadrature component q are output. Quadrature detection circuit 51
Output signals i and q of the low-pass filter (low-pass filte
r) Two components i, 52, 52 ', which are low-pass filtered and have mutually orthogonal phases of the second (or third) harmonic component,
It becomes q (complex signal).

These complex signals i and q are converted into a complex absolute value circuit 5
It is input to 3 and is subjected to calculation by the following equation.

[0047]

[Equation 1]

The equation (1) is a calculation for obtaining the absolute value of the complex signal, and by this, a signal corresponding to the signal obtained by envelope detection of the second (or third) harmonic component is obtained. That is, as in the case of FIG. 1, the envelope detection signal of the second (or third) harmonic component is obtained.

Since this embodiment utilizes quadrature detection, it is preferable in terms of precisely extracting a desired harmonic component.
On the other hand, the one using the Pand-pass filter is preferable because the configuration is simplified.

[0050]

As described in detail above, according to the first invention for solving the problems, the harmonics of transmitted ultrasonic waves are generated in the region behind the cross section due to the nonlinear effect of the focused sound field. Since the C-mode image is generated based on the echo of the higher harmonic component, it is possible to naturally obtain a perspective image of the region behind the cross section. That is, it is possible to realize an ultrasonic imaging method for performing reflection / transmission imaging without a range gate.

According to the second invention for solving the problem, the fact that the harmonics of the transmitted ultrasonic waves are generated in the region behind the cross section due to the nonlinear effect of the focused sound field is utilized. Since the C-mode image is generated on the basis of the echo of 1, the transparent image of the region behind the cross section can be naturally obtained. That is, it is possible to realize an ultrasonic imaging apparatus that performs reflection / transmission imaging without a range gate.

According to the third invention for solving the problem, the second effect of the transmitted ultrasonic wave is generated by the nonlinear effect of the focused sound field.
The C-mode image is generated based on the echo of the second harmonic component by utilizing the fact that the harmonics are generated in the area behind the cross section, so that a perspective image of the area behind the cross section can be obtained naturally. it can. That is, it is possible to realize an ultrasonic imaging apparatus that performs reflection / transmission imaging without a range gate.

[Brief description of drawings]

FIG. 1 is a block diagram of an apparatus according to an example of an embodiment of the present invention.

FIG. 2 is a configuration diagram of an ultrasonic probe in an apparatus according to an example of an embodiment of the present invention.

FIG. 3 is a time chart showing the operation of the apparatus according to the exemplary embodiment of the present invention.

FIG. 4 is a block diagram of an apparatus according to an example of an embodiment of the present invention.

[Explanation of symbols]

10 Ultrasonic probe 101 oscillator 102 acoustic lens 14 subject 16 Pulsa 18 T / R switch 20 ultrasonic beam 24 scanning actuator 28 Control unit 30 signal processor 34 Variable gain amplifier 36 Gain Function Generator 38 bandpass filter 40 Envelope detector 42 integrator 44 cage 46 scan converter 48 display 51 Quadrature detection circuit 52,52 'low pass filter 53 Complex absolute value circuit

─────────────────────────────────────────────────── ─── Continuation of the front page (58) Fields surveyed (Int.Cl. ⁷ , DB name) A61B 8/00-8/14

Claims (3)

(57) [Claims] 1. An ultrasonic wave transmitting / receiving unit for two-dimensionally scanning with an ultrasonic beam focused on a cross section of a subject at a predetermined depth, and an echo received by the ultrasonic wave transmitting / receiving unit. An ultrasonic imaging apparatus comprising: an image generating unit that generates a C-mode image corresponding to the region based on a harmonic component generated from a region deeper than the focal point. 2. An ultrasonic probe for transmitting ultrasonic waves to a subject and receiving ultrasonic echoes from the subject, and a cross section at a predetermined depth of the subject through the ultrasonic probe. Transmitting / receiving means for two-dimensionally scanning an ultrasonic beam focused on the top to receive an echo, and signal extraction for extracting a second harmonic component generated from a region deeper than the focus in the echo received by the transmitting / receiving means. An ultrasonic imaging apparatus comprising: a means for generating a C-mode image corresponding to the area based on an output signal of the signal extracting means. 3. The ultrasonic imaging apparatus according to claim 2, wherein the signal drawing means uses a bandpass filter that passes a second harmonic.