JPH0146147B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an ultrasonic diagnostic apparatus capable of displaying an image of a biological tissue in a subject, and particularly an ultrasonic diagnostic apparatus capable of focusing an ultrasonic beam on a biological tissue located at an arbitrary depth from the surface of a subject. Regarding.

Ultrasonic diagnostic equipment that transmits and receives ultrasound beams into a subject to display an image of a desired biological tissue is well known, and various scanning methods are used in this ultrasound diagnostic equipment. A so-called B-mode ultrasonic diagnostic apparatus that can display a tomographic image of a subject, a so-called C-mode ultrasonic diagnostic apparatus that can display a planar image of a living tissue in a subject, etc. are known. In this type of ultrasound diagnostic equipment, an electronic scanning ultrasound probe is suitable for beam scanning, and excitation is supplied to each vibrating element arranged at equal intervals on the electronic scanning ultrasound probe. By controlling the delay of the signal, it is possible to scan the beam as desired, focus the ultrasound beam on the living tissue at any depth in the subject, and display an image of a specific site with good resolution.

However, with conventional devices, it has been difficult to set a focal point, and it has sometimes been impossible to display a clear image.

FIG. 1 shows a conventional ultrasonic diagnostic apparatus capable of displaying a planar image by focusing an ultrasonic beam on a living tissue in a subject.

In FIG. 1, 10 is the surface of the object to be examined, and 1
Reference numeral 2 denotes a biological tissue surface in the subject that is located at a depth l from the subject surface 10 and is used for diagnosis. A plurality of vibrating elements arranged at equal intervals are provided on the lower surface of the electronic scanning probe 14, and the ultrasonic beam is directed toward the biological tissue surface 12 in the subject, that is, in the Z-axis direction in the figure. , and the biological tissue surface 1 in the subject.
2. Receive the ultrasound echo signal from 2. and,
The electronic scanning probe 14 can electronically scan an ultrasonic beam in the X-axis direction, and furthermore, the probe 14
If the ultrasonic beam is scanned in the X-axis direction while moving it in the Y-axis direction by the scanner 16, a plane scanning effect of the ultrasonic beam can be obtained.

The electronic scanning probe 14 and the scanner 16 are controlled by a scanning control section 18. The scan control unit 18 focuses the ultrasonic beam emitted from the probe 14 onto the biological tissue surface 12 in the subject located at a predetermined distance l in the Z-axis direction from the lower surface of the probe 14, and In order to scan and control the beam, the excitation signal to each vibrating element of the electronic scanning probe 14 is controlled with a predetermined delay time.

Biological tissue surface 1 received by electronic scanning probe 14
The ultrasonic echo signal from 2 is sent to the image signal converter 20
is supplied to The image signal converter 20 is the probe 14
The image signal from the image signal converting section 20 is supplied to the display section 22. The display section 22 can display an image of the biological tissue surface 12 in the subject based on the image signal from the image signal conversion section 20.

In this way, since the ultrasound beam is focused on the biological tissue surface 12 in the subject, it is possible to display the biological tissue surface 12 with good resolution on the display screen.

As described above, the conventional example shown in FIG. 1 can display a clear image with good resolution on its display unit 22. The focal point of the ultrasonic beam emitted from the probe 14 must be accurately set on the biological tissue surface 12 in the subject.
That is, if the living tissue surface 12 in the subject and the focal point are even slightly separated, the resolution and clarity of the living tissue surface 12 displayed as an image on the display unit 22 will rapidly deteriorate. be.

However, in conventional ultrasonic diagnostic apparatuses, there have been cases in which a focal point cannot be set on the biological tissue surface 12.

The reason for this will be explained below with reference to FIG. 2, taking the case of mammary gland diagnosis as an example.

Generally, the electronic scanning probe 14 has a characteristic that its resolution decreases in a relatively short distance region, whereas the mammary gland 23 is located at a shallow depth of about 1 to 3 cm from the breast surface 10 (subject surface). Therefore, in order to obtain a clear display image, the probe 14 must be placed at a distance L from the subject surface 10. Since this distance L is indeterminate depending on the diagnostic conditions, it is difficult to accurately set the focusing point F, resulting in the disadvantage that the accurate beam focusing effect at the diagnostic site described above cannot be obtained.

The present invention has been developed in view of the above-mentioned conventional problems, and its purpose is to accurately focus the ultrasound beam emitted from a probe onto the diagnostic site in the subject, thereby clearly identifying the living tissue in the subject. The object of the present invention is to provide an ultrasonic diagnostic device that can display images.

In order to achieve the above object, the present invention provides an electronic scanning probe that has a plurality of vibrating elements arranged at equal intervals and emits an ultrasonic beam into a subject and receives ultrasonic echoes from the subject. an image signal converter that converts the received echo signal from the probe into an image signal; a display unit that displays an image of the living tissue in the subject using the image signal from the image signal converter; a scan control unit that controls an excitation signal to each vibrating element with a predetermined delay time in order to focus the emitted ultrasonic beam at a predetermined distance from the probe and scan the ultrasonic beam; In the ultrasonic diagnostic apparatus, the scanning control section includes a distance detection circuit that detects the distance from the probe to the surface of the object using an echo signal from the surface of the object, and a distance detection circuit that detects the distance from the probe to the object surface using an echo signal from the object surface; and a focus distance correction circuit that focuses the ultrasound beam to an arbitrary depth from the surface, and the image signal conversion unit amplifies the echo signal from the biological tissue in the subject with a gain that increases with the passage of time.
The present invention includes an STC amplification circuit, and the STC amplification circuit is characterized in that the STC operation is started by an echo signal from the surface of the subject in order to correct attenuation of the ultrasonic signal within the subject.

Hereinafter, preferred embodiments of the present invention will be described based on the drawings. FIG. 3 shows an embodiment of the present invention, in which the same members as in FIGS. 1 and 2 are given the same reference numerals, and illustration of the scanner 16 is omitted.

The probe 14 emits an ultrasonic beam toward the surface 10 of the subject, and sets a focal point F on the biological tissue surface 12 in the subject. The ultrasound echo signal from the focal point F returns to the probe 14, and the probe 14 receives the ultrasound echo signal. When the ultrasonic beam emitted from the probe 14 is scanned in the X-axis direction, the probe 14 receives an ultrasonic echo signal during this scanning. In this way, when the scanner 16 (not shown) moves the probe 14 in the Y-axis direction while the probe 14 is scanning in the X-axis direction, the probe 14 is exposed to the living body. Organizational surface 12
This means that the ultrasonic echo signal from the

In mammary gland diagnosis, the probe 14 is placed at a distance L from the breast surface 10, and a water bag 24 filled with water is provided between the probe 14 and the subject surface 10. ing. This water bag 24 functions to prevent attenuation of ultrasonic signals between the probe 14 and the surface 10 of the subject.

The scan control unit 18 includes an electronic scanner 26 that performs scan control and focus control of the probe 14, a distance detection circuit 30 that detects the distance between the object surface 10 and the probe 14, and a distance L ₀ +l that is stored in advance. The focus distance control circuit 28 includes a focus distance correction circuit 32 and a focus distance correction circuit 32.

Distance stored in focus distance correction circuit 32
L ₀ +l is the actual distance L between the object surface 10 and the probe 14 and the diagnostic site depth l in order to obtain an accurate focusing point.
However, as mentioned above, since the actual distance L is indefinite, in the present invention, at the start of diagnosis, the focus distance correction circuit 32 calculates a rough estimated distance.
A feature is that a distance L ₀ +l corresponding to the sum of L ₀ and depth l is temporarily stored, and this is corrected by preliminary transmission and reception of an ultrasound beam. The depth l can be set to a desired value by a depth command signal from the outside, and for example, the value of the depth l can be set to a predetermined value by rotating a knob.

The received echo signal received by the probe 14 is supplied to a distance detection circuit 30 provided in the focus distance control circuit 28, and the distance detection circuit 30 determines the distance L between the probe 14 and the breast surface 10. The distance detection signal from the distance detection circuit 30 is supplied to the focus distance correction circuit 32. The electronic scanner 26 can newly correct and set the diagnostic focusing point F using the distance correction signal from the focus distance correction circuit 32.

On the other hand, the received echo signal of the probe 14 is supplied to the image signal conversion circuit 34 of the image signal conversion section 20. The image signal of the image signal conversion circuit 34 is supplied to an STC amplifier circuit 36 whose gain changes over time, and the STC amplifier circuit 36 is connected to the distance detection circuit 30.
The trigger signal from the trigger circuit 38 to which the detection signal is supplied starts STC amplification of the amplified detection signal. The amplified output of the STC amplifier circuit 36 is supplied to a memory 40, and the memory 40 supplies an image signal to the display unit 22 every time one plane scan is completed.

A preferred embodiment of the present invention has the above configuration,
The effect will be explained below.

In the present invention, preliminary ultrasonic waves are used to detect the distance L between the breast surface 10 and the probe 14, which is fixed at an indefinite distance from the breast surface 10, prior to transmitting and receiving the ultrasonic beam used for actual diagnosis. Beams are transmitted and received.

For this preliminary transmission and reception, the distance L ₀ +l stored in the focus distance correction circuit 32 is supplied to the electronic scanner 26, and when an excitation signal is supplied from the electronic scanner 26 to the probe 14, the probe 14 is an arbitrarily determined preliminary focal point in the subject
A focus-controlled ultrasonic beam is emitted to a point F ₀ , that is, a distance L ₀ +l from the probe 14.

In this embodiment, the preliminary focusing point F ₀ is determined based on the depth l of the desired diagnosis site and the roughly set position L ₀ of the probe 14, but it can be determined completely independently of the diagnosis site. It may also be a decision. On the breast surface 10, the biological tissue of the subject and water have different acoustic impedances, so part of the ultrasound beam that reaches the breast surface 10 is reflected, and the other part passes through the breast surface 10 and is probed. It focuses on a preliminary focus point F ₀ at a distance L ₀ +l from child 14.

The probe 14 receives an ultrasonic echo signal from the object surface 10 and supplies the received echo signal to the distance detection circuit 30 .

The distance detection circuit 30 has previously obtained a synchronization pulse tp from the electronic scanner 26 when the electronic scanner 26 supplies an excitation signal to the probe 14, and the time between this synchronization pulse tp and the echo signal from the breast surface 10 is The distance L between the probe 14 and the breast surface 10 is detected from the misalignment. Then, the focus distance correction circuit 32 reads the distance L from the distance detection circuit 30, compares it with the previously stored distance _L0 , and calculates the difference Δl between the two distances. Next, the correction amount Δl is added to the previously stored distance L ₀ +l, and the distance L + l (=
L ₀ +l+Δl) is calculated.

As described above, the distance L+l to the focal point F to be set on the biological tissue surface 12 in the subject whose image is desired to be displayed on the display unit 22 is obtained.

Diagnostic transmission and reception for displaying an image of the biological tissue surface 12 in the subject on the display unit 22 is performed subsequent to the preliminary transmission and reception.

The distance L+l obtained by the focus distance correction circuit 32 is supplied to the electronic scanner 26, and the ultrasonic beam is accurately focused on the focal point F on the biological tissue surface 12 in the subject. The reflected ultrasound echo signal from the focal point F is received by the electronic scanning probe 14 and stored in the memory 40 of the image signal converter 20 as image information.

As described above, diagnostic transmission and reception has been performed, and together with the preliminary transmission and reception described above, 1
The transmission/reception is completed. When such transmission/reception consisting of preliminary transmission/reception and diagnostic transmission/reception is performed in the X-axis direction and the Y-axis direction, image information of the biological tissue surface 12 in the subject with high information density is stored in the memory 40. Here, biological tissue surface 1 in the subject
2, the depth command signal at depth l that has been supplied to the focus distance control circuit 28 is supplied to the image signal conversion circuit 34 as shown by the broken line in the figure, and Only the echo signals from the biological tissue surface 12 inside are selected and converted into image signals.

When the image signal is supplied from the memory 40 to the display unit 22, the display unit 22 displays the biological tissue surface 12 in the subject.
Display images with good resolution.

Next, an explanation will be given of the operation of the STC amplifier circuit 36 that effectively compensates for the change in the depth l of the diagnostic site and the resulting change in the level of the received echo signal due to the attenuation of the ultrasound beam.

The STC amplifier circuit 36 is connected to the biological tissue surface 1 in the subject.
The ultrasonic beam is adjusted so that the image displayed on the living tissue surface 12 has a uniform brightness level, regardless of whether the tissue surface 2 is located at a long distance or a short distance from the subject surface 10. This is an amplifier circuit that temporally controls the gain during the sweep.

As is well known, during an examination, the attenuation of the ultrasonic signal is large, and therefore, in the living tissue from the object surface 10 to the focal point F located at a depth l, the value at the depth l A corresponding attenuation of the ultrasound signal occurs. Therefore, as described above, if the ultrasonic echo signal from the focal point F is received and the image is simply displayed, a deep area (that is, when the depth l is large) will be displayed darkly on the display, and a shallow area will be displayed darkly on the display. On the contrary, a portion (that is, when the depth l is small) is displayed brightly, and the image on the display section 22 does not have a uniform brightness level as a whole, which causes inconvenience in diagnosis.

In this case, the STC amplifier circuit 36 is used as a means to maintain uniform brightness in the display section 22 regardless of the value of the depth l.
0 is provided with an STC amplifier circuit 36.

FIG. 4 shows an explanatory diagram of the operation of the STC amplifier circuit 36.

In the STC amplification circuit 36 of this embodiment, whereas the conventional circuit starts the STC amplification action upon emission of an ultrasound beam, the echo signal 100 from the object surface 10 shown in FIG. STC operation when received i.e. Figure 4c
According to this embodiment, even when the distance between the probe 14 and the surface 10 of the subject is indefinite, the biological tissue 12 in the subject is kept at the same level. It has the advantage of being able to display images at a brightness of . As is clear from FIG. 4c, the echo signal 102 from the focal point F on the biological tissue surface 12 in this embodiment is amplified by the gain A.

The state of attenuation of the ultrasonic signal in the subject is shown in the fourth figure.
The increase in gain of the STC amplifier circuit 36 is shown in FIG. 4c, and the output characteristic of the STC amplifier circuit 36 is shown in FIG. 4d. According to Fig. 4, the echo signal of Fig. 4b is
When supplied to the STC amplifier circuit 36, the STC amplifier circuit 36 performs amplification with the gain characteristics shown in FIG. 4c, and as shown in FIG. Perform output.

In this embodiment, the object surface detection signal 200 of the distance detection circuit 30 in FIG. 3 is used as the start signal for the STC operation described above, and this surface position detection signal 200 is supplied to the trigger circuit 38. Then, an ultrasound beam for actual diagnosis is emitted, and an echo signal 1 from the breast surface 10 is emitted.
00 is received, the trigger circuit 38 provides a trigger signal to the STC amplifier circuit 36, and the STC amplifier circuit 36 starts increasing the gain by the trigger signal. Therefore, when the echo signal 102 from the focal point F on the biological tissue surface 12 in the subject is supplied to the STC amplifier circuit 36 via the image signal conversion circuit 34, the STC amplifier circuit 36 is converted to the STC amplifier circuit 36 at the gain A at that time. amplifies the echo signal 102. obtained in this way
As described above, the level of the amplified output of the STC amplifier circuit 36 is constant regardless of the depth l, so the display image of the biological tissue surface 12 in the subject displayed on the display unit 22 is the biological tissue surface. The brightness level is uniform regardless of whether the area is deep or shallow.

As explained above, the present invention emits a preliminary ultrasonic beam in advance, receives an echo signal from the object surface 10, and measures the actual distance L to the object surface.
Then, based on this distance L, the focusing point F is accurately set on the biological tissue surface 12 in the subject, so regardless of the size of the distance L, the subject can be detected with good resolution on the display unit 22. The living tissue surface 12 inside can be displayed. In addition, the image signal converter 20 is provided with an STC amplifier circuit 36, and the gain control of the STC amplifier circuit 36 is started when the diagnostic ultrasound beam reaches the surface of the subject. Regardless of the size of l, images can be displayed with a uniform brightness level.

[Brief explanation of drawings]

Figure 1 is an explanatory block diagram of a conventional ultrasonic diagnostic device that can focus an ultrasound beam on living tissue in a subject and display a planar image.
FIG. 3 is a block explanatory diagram showing a preferred embodiment of the ultrasonic diagnostic apparatus according to the present invention; FIG. The figure is an explanatory diagram of the operation of the STC amplifier circuit 36. DESCRIPTION OF SYMBOLS 10... Subject surface, 12... Biological tissue surface in the subject, 14... Electronic scanning probe, 18... Scanning control unit, 20... Image signal conversion unit, 22... Display unit, 26 ...Electronic scanner, 28...Focus distance control circuit, 30...Distance detection circuit, 32...
...Focus distance correction circuit, 36...STC amplifier circuit.

Claims (1)

[Claims] 1. An electronic scanning probe that has a plurality of vibrating elements arranged at equal intervals and emits an ultrasonic beam into a subject and receives ultrasonic echoes from the subject; an image signal converter that converts the echo signal received from the probe into an image signal; a display unit that displays an image of the living tissue in the subject using the image signal from the image signal converter; and an image signal converter that converts the received echo signal from the probe into an image signal; An ultrasonic diagnosis comprising: a scanning control unit that controls an excitation signal to each vibrating element with a predetermined delay time in order to focus a sound wave beam at a predetermined distance from a probe and control scanning of the ultrasonic beam; In the apparatus, the scanning control section includes a distance detection circuit that detects the distance from the probe to the surface of the object using an echo signal from the surface of the object, and a distance detection circuit that detects a distance from the surface of the object using the distance detection signal from the distance detection circuit. A focus distance correction circuit that focuses the ultrasonic beam to the depth,
The image signal conversion unit includes an STC amplification circuit that amplifies an echo signal from a living tissue in the subject with a gain that increases over time, and the STC amplification circuit amplifies the ultrasound signal in the subject. An ultrasonic diagnostic apparatus characterized in that an STC operation is started by an echo signal from the surface of a subject in order to correct attenuation.