JPS61272039A - Ultrasonic diagnostic apparatus - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

Detailed Description of the Invention [Technical Field of the Invention] The present invention relates to an ultrasonic diagnostic apparatus that obtains an ultrasound image of a subject based on echo signals from the subject of ultrasound waves transmitted toward the subject. Regarding.

[Technical background of the invention and its problems] In recent years, in ultrasonic diagnostic equipment, ultrasound beams transmitted from a transducer group consisting of a plurality of elements arranged in an array have been electronically transmitted. By focusing on the ultrasonic beam and providing a focus point on the ultrasonic beam, the resolution of the ultrasonic image is improved.

FIG. 4 is an explanatory diagram for explaining focusing of an ultrasonic beam. FIG. 1 shows a transducer group consisting of a plurality of elements 1-1 to 1-n, and r is the focal point of the ultrasonic waves transmitted from this transducer group. However, the focus point f is assumed to be in the Fraunhoffer region for each element, and in the Fresnel region for all the apertures. Actual element aperture is 0.5M, total aperture is 3 CIR,
When the excitation frequency is 3 MHz and the speed of sound is 150011/S, the above two conditions are: -(1). Ultrasonic diagnostic equipment generally falls within this range.

Further, the sound field Up near the focus point f is expressed as the following equation.

Here is. However, the equation (4) above expresses the delay time given to each element as a phase correction. Note that k indicates a wave number and is 2π/λ.

Furthermore, since the Fraunhoffer approximation can be used for the element aperture, if the term Xo''/zi is ignored, the above equation (3) can be rearranged as the following equation.

Here, It is.

Furthermore, since the sound field considered here is limited to the vicinity of the focus point, by setting xi(nx), the above equation (0) can be expressed as the following equation.

Te. What is shown by equation 0 is a value indicating the directional characteristic of each element, and is called an element factor. this is,
This shows that among the sound waves emitted from each element and focused on the focus point f, those emitted from the end elements are weaker.

FIGS. 5A and 5B are explanatory diagrams showing the relationship between the sound waves radiated from the central element IS and the end element 1n, respectively, and the focus point f. Figure (a),
As is clear from equations (b), (8), and 0 above, the sound field near the focus point is expressed by discrete Fourier transform of the element factors with respect to n. Since the element of is weak, the sound field near the focus point f when subjected to discrete Fourier transform becomes dull, and this cannot be said to be optimal focusing. Therefore, the resolution of the visualized ultrasound image is not sufficient.

[Object of the Invention] The present invention has been made in view of the above circumstances, and its purpose is to provide an ultrasound diagnostic apparatus that can optimize focusing and improve the resolution of ultrasound images. It is about providing.

[Summary of the Invention] The present invention for achieving the above object is characterized in that it includes a gain correction means for performing gain correction on ultrasonic transmission/reception signals according to the directivity characteristics of each transducer. By configuring an ultrasonic diagnostic device, the resolution of ultrasonic images is improved.

[Embodiments of the invention] Hereinafter, the present invention will be specifically explained with reference to Examples.

FIG. 1 is a block diagram showing the main parts of an ultrasonic diagnostic apparatus according to an embodiment of the present invention. In the figure, 1 is a transducer group formed by arranging a plurality of transducers 1-1 to l-n in an array, and 2-1 to 2-n are the transducer groups 1-1 to 1-n.
The amplifiers (amplification means) 3-1 to 3-n arranged corresponding to the amplifiers 2-1 to 2-n' are delay means arranged corresponding to the amplifiers 2-1 to 2-n'. Further, 4 is a gain setting section, which sets the gain of the amplifiers 2-1 to 2-n according to the directional characteristics (element factors) of the oscillators 1-1 to 1-n. be. For example, vibrator 1
The gain of the amplifier corresponding to the transducer located in the center is set to O dB, and the gain of the amplifier corresponding to the transducer located near the edge is set high. The gain of the amplifier is approximately determined by multiplying the element factor of the vibrator by a reciprocal number. Specifically, as shown in the previous equation 0, the directivity ratio caused by the superposition of sound waves, the effective area when the element aperture is viewed diagonally from the focus point r, and the mechanical/electrical coupling of the element material. Since the actual element factor is determined by various factors such as the directional mobility of the coefficient with respect to the sound wave, it is preferable to take these factors into consideration when determining the gain.

In this sense, the amplifiers 2-1 to 2-n
and the gain setting section 4 are collectively referred to as gain correction means 5.

Further, 6 is a transmitter that generates a pulse signal of a predetermined frequency, and the generated pulse signal is transmitted to the delay means 3-1 to 3-3.
8 oscillators 1-1 via n and amplifiers 2-1 to 2-n
1 to 1-n. 7 is a receiving unit that performs various arithmetic processing for visualization of ultrasound images, and transmits echo signals received by each of the transducers 1-1 to 1-n to amplifiers 2-1 to 2-n and delays. Means 3-1
3-n to 3-n.

Incidentally, the delay times of the delay means 3-1 to 3-n are determined in relation to the focus point f, but the control thereof is the same as that of the conventional device, so a description thereof will be omitted.

In the embodiment device configured as described above, the transmitter 6
The pulse signals output from the delay means 3-1 to 3-
After being delayed for a predetermined time by n, the amplifier 2-1
It is used to excite the corresponding sensor of the transducer group 1 via the transducers 2-n to 2-n. The reflected wave from the object of the ultrasonic wave transmitted toward the object (not shown) by the excitation of the transducer group 1 is as follows.
The wave is received by the vibrator group 1 again. The electrical signals generated in the eight oscillators 1-1 to 1-n by receiving the reflected waves are as follows:
After being amplified by the corresponding amplifiers 2-1 to 2-n and delayed for a predetermined time by delay means 3-1 to 3-n, the currents are added together and input to the receiving section 7.

In the above transmission/reception operations, the pulse signals used for excitation of the imagers 1-1 to 1-n and the oscillators 1-1 to 1-n
The electric signal received by the wave, that is, the transmitted and received wave signal, is subjected to gain correction by the gain correction means 5 according to the directivity characteristics of the eight transducers 1-1 to 1-n.

Here, if no gain correction is performed, the intensity of the sound wave at the full aperture will be as shown by 8 in FIG. , the intensity of the sound wave has a rectangular shape as shown by 9 in FIG. 2(b). When the waveform shown by 8.9 is Fourier transformed, it becomes 8' in FIGS. 3(a) and (b), respectively.

The waveform is shown as 9'. Therefore, by performing gain correction, the main beam of the ultrasonic wave becomes narrower, and focusing is improved compared to before gain correction.

As described above, in the device of this embodiment, the amplifiers 2-1 to 2-n arranged corresponding to the camera elements 1-1 to 1-n and the gains of the amplifiers 2-1 to 2-n Since it is equipped with a gain correction means having a gain setting section 4 that performs settings and can achieve appropriate focusing, it is possible to visualize a high-resolution ultrasonic image.

Although one embodiment of the present invention has been described above, it goes without saying that the present invention is not limited to the above-mentioned embodiment, and can be modified as appropriate within the scope of the gist of the present invention.

For example, in the above embodiment, the amplifiers 2-1 to 2-n are arranged corresponding to the transducers 1-1 to 1-n. As long as the gain of the amplifier is set to OdB, the amplifier can be omitted.

Further, in the above embodiment, the amplifiers 2-1 to 2-n are used in common for transmitting and receiving ultrasonic waves, but they may be provided separately.

Furthermore, although the device of the above embodiment is called a current adding device, it is a device called an aperture synthesis device, that is, a device that performs phase correction not as a time delay, but as a device that performs phase correction using digital signal processing. The present invention can also be applied to such cases. In this case, gain correction may be performed by multiplying the echo component converted into a digital signal by the reciprocal of the element factor of the transducer. In the case of the aperture synthesis device, all points can be treated as focus points, so the effect of gain correction is greater than in the above embodiment.

Note that the scanning method by the transducer group 1 may be either linear or sector.

[Effects of the Invention] As described in detail above, according to the present invention, it is possible to provide an ultrasound diagnostic apparatus that can optimize focusing and improve the resolution of ultrasound images.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing the main parts of an ultrasonic diagnostic apparatus according to an embodiment of the present invention, FIGS. 2(a) and 3(b), and FIG.
a) and (b) are waveform diagrams for explaining the operation of the device of this embodiment in comparison with a conventional device; FIG. 4 is an explanatory diagram for explaining focusing of the ultrasonic beam; FIG. 5(a) , (b
) are explanatory diagrams showing the relationship between the focus point and the sound waves radiated from the center element and end elements in the transducer group, respectively. 1... Vibrator group, 1-1 to 1-n... Vibrator, 5
...gain correction means. Agent Patent attorney Noriyuki Chika (1 person) Figure 2 (b) CG) (b)

Claims (1)

[Claims] An ultrasound system that transmits and receives ultrasound waves using multiple transducers arranged in parallel in an array, and obtains an ultrasound image of the subject based on the reflected waves of the ultrasound waves sent toward the subject. What is claimed is: 1. An ultrasonic diagnostic apparatus, characterized in that the ultrasonic diagnostic apparatus includes gain correction means for performing gain correction on ultrasonic transmission and reception signals according to the directivity characteristics of each of the transducers.