JPS5841535A - 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 The present invention relates to an electronic scanning type ultrasonic diagnostic apparatus.

The present applicant proposed in Japanese Patent Application No. 55-88129 an ultrasonic diagnostic apparatus having an ultrasonic probe having an acoustic lens provided in front of an array of ultrasonic transducers arranged in an arc shape. First, the ultrasonic diagnostic apparatus according to this application filed by the present applicant will be explained. FIG. 1 is a diagram illustrating the scanning line of ultrasound, in which the ultrasonic transducer row 1 and the acoustic lens 2 are shown in a cross section by the scanning plane. is emitted toward the acoustic lens 2 from the transducer group determined by i). The radiation direction is the direction of the straight line connecting the center of curvature 5 of the ultrasound transducer row 1 on the central axis 9 and the selected transducer group. The ultrasonic beam 4 radiated in this straight direction is transmitted at the boundary between the acoustic lens 2 and the living body 3.
Refraction occurs due to the difference in sound speed between the two. acoustic lens 2
Since the speed of sound is slower than that of the living body 3, the ultrasound beam is refracted in a direction away from the central axis 9. The intersection point between the extension line of the refracted ultrasound beam 4 and the center line 9 is designated as 6. The intersection point 8 is found in the same way for the ultrasonic beam 4 as well as the ultrasonic beam 7 near the center.

This intersection 8 is located in the direction of the center of curvature 5 from the previous intersection 6. These intersection points and the acoustic lens2. The distance r from the boundary between the living bodies 3 is the angle between the straight line connecting the selected transducer group and the center of curvature and the perpendicular to the boundary surface. Then, it is shown as . However, R is the distance between the center of curvature 5 and the boundary surface, and V and C are the sound speeds of the acoustic lens 2 and the living body 3, respectively. Therefore, when the sound speeds C and V are different, the distance r is θ.

That is, it changes depending on the ultrasonic scanning line.

The images obtained by such scanning, as shown schematically in Figure 2, have the characteristics of being able to obtain a wide field of view with a small aperture, and also being able to observe from an oblique direction even after obstacles such as bones. . However, such devices required extensive equipment to scan convert to standard television scanning because the distance I varied from scan line to scan line.

In view of these drawbacks, the present invention provides an ultrasonic diagnostic apparatus that is simple and capable of displaying standard television images and has a wide field of view with a small aperture.

An embodiment of the present invention will be described below with reference to the drawings.

FIG. 3 illustrates an ultrasonic scanning line in one embodiment of the present invention, in which the ultrasonic transducer array 1 is arranged on a circular arc centered on the center of curvature 5, similar to the example in FIG. . Furthermore, an acoustic lens 2' is bonded to the front surface of this transducer array 1.

The boundary surface 10 where the acoustic lens 2' and the living body 3 come into contact is a curved surface, unlike the example shown in FIG. The ultrasound transducer row 1 selects several adjacent transducers as a group, similar to the well-known linear electronic scanning, emits an ultrasound beam to the living body 3, and receives reflected ultrasound with the same transducer group. do.

This group of transducers is sequentially moved by switching the transducers to scan the ultrasonic beam.

Note that the transducer array 1 and the acoustic lens 2' are shown in cross section on the ultrasonic scanning plane. The ultrasonic beam 4' emitted from one of the transducer groups propagates inside the acoustic lens 2' in the direction of a straight line connecting the center of curvature 5 and this selected transducer group,
It is refracted at the boundary surface 10. This boundary surface 1o is set so that the refraction direction of the ultrasonic beam coincides with a straight line passing through the virtual origin 6' on the central axis 9. Therefore, the extension lines of the ultrasound beams 4' and 7' in the living body 3 pass through the virtual origin 6' together with other ultrasound beams. The directional characteristics in reception are similar to those of the ultrasound beam in transmission. The image obtained by such ultrasonic scanning is almost the same as that shown in FIG. 2, as shown schematically in FIG. 4, except that the body surface part is not a straight line.

FIG. 6 is a block diagram for explaining the operating principle of an apparatus according to an embodiment of the present invention. The transmission pulse generated by the transmitter 11 is applied to the probe 12, which emits ultrasonic waves in the selected direction.The returned echo signal is converted into an electrical signal by the same probe 12, and then sent to the receiver 13. is converted into a signal representing the intensity of the echo signal.

This converted signal is converted into a digital signal by the analog-to-digital converter 14 and written into the main memory 16. The timing for performing analog-to-digital conversion and sampling the echo intensity signal is based on the ultrasonic scanning lines 25-1 to 26-5 and the standard television scanning lines 26-1 to 26-6 in the display image of FIG. Let be the intersection of Therefore, the samples will be at regular intervals defined by each ultrasound scan line. The write and read addresses to the main memory 16 in FIG. 5 are controlled by the main memory control section 16 and transferred to the line memory 17 in units of one horizontal scanning line of a standard television. In response to a signal from the main memory control section 16, an adder calculates a value from the read-only memory 18 that is inversely proportional to the distance between a constant display point corresponding to the virtual origin 6' and this horizontal scanning line on the horizontal scanning line of a standard television. Output to 19. This output data is cumulatively added by an adder 19 and a latte 2o. This cumulative addition data is sent to the address converter 2.
Enter 1. The address converter 21 is a read-only memory that outputs a signal that selects the corresponding ultrasound scan line and the method of interpolation between the ultrasound scan lines by a conversion that is invariant to the horizontal scan lines of a standard television display. Further, the above cumulative addition is repeated at regular intervals for each horizontal scanning line of a standard television display, and the data to be displayed is selected from the line memory 1A by the output of the address converter 21 determined by each result. Interpolation processing is performed and the digital-to-analog converter 22 converts the signal into an analog signal, which is mixed with other signals by the mixer 23 and displayed on the monitor 24.

Next, a method for obtaining the curve in the ultrasonic scanning section of the boundary surface 10 in FIG. 3, that is, the acoustic lens 21, will be explained. The origin is the intersection of the boundary surface 1o and the center line 9, the T axis is above the center line, and the S axis is perpendicular to the center line. Living body 3
and the sound speed of the acoustic lens are C and ■, respectively, and the positions of the center of curvature of the transducer array 1 and the virtual origin on the T-axis are R and r, respectively, then a point on the boundary surface 1o according to the present invention (S,
T) is dSV, P Takumi] 7 - (T - r ) - (T - R) W...
...(1) Follows the differential equation. The position of the center of curvature of the transducer array (position R
Table 1 shows the results of numerical integration of a curve with a boundary of 1° passing through the origin when the position r of the virtual origin is between 62 and 48 degrees, with R being 91 degrees.

Table 1 Unit of deviation (T) of acoustic lens surface from straight line
Further, the present invention is not limited to a method of modifying the shape of an acoustic lens, and the arrangement shape of the ultrasonic transducer array can be modified from a cylindrical surface, or both can be modified together.

Next, a method for correcting the arrangement of ultrasonic transducer arrays will be explained. Using the same ST axis as above, let the position of the virtual origin be r, and the sound speeds of the living body and acoustic lens be C and V, respectively, then the position (S, T) of the ultrasonic transducer array surface is 1, -6, (2) 5a-8 This becomes a differential equation. Note that a is a function used as an auxiliary function, and is the position where the ultrasonic beam from the position (S, T) passes through the S axis, which is the interface between the living body 3 and the acoustic lens 2'. The position r of the virtual origin 6' is assumed to be 48 cylinders. acoustic lens 2
Since the interface 10 with the living body 3 ' is a straight line, the second
T in equations and equation 2' match the thickness of the acoustic lens. Table 2 shows the results of integrating the second equation while determining the position of a from the equation 2', assuming that the thickness of the center of the acoustic lens 2' is 1. T' in this table indicates a cylindrical surface close to the value of T for reference.

Table 2 Lens thickness T: Depends on the virtual origin. If the acoustic lens is configured in this way and the contact surface of the acoustic lens with the living body is made flat, the images can have the same shape.

In the above explanation, two examples were explained regarding the arrangement of the ultrasonic transducers and the shape of the acoustic lens, but the present invention is not limited to these examples. You can also do that. In this case as well, scan conversion can be performed in the same manner as the scan conversion explained using the block diagram of FIG.

Furthermore, in the cross section of the ultrasound probe perpendicular to the ultrasound scanning plane, the boundary line between the ultrasound transducer, the acoustic lens, and the living body is
It can also be shaped to focus ultrasonic waves.

As described above, according to the present invention, by slightly modifying the array shape of the ultrasonic transducers or the shape of the acoustic lens, all scanning lines can be made to pass through a predetermined constant, thereby making it possible to An ultrasonic diagnostic device that has a wide field of view and can be easily displayed on a standard television display by digital conversion can be realized at low cost using a small scale device.

[Brief explanation of the drawing]

Figure 1 is a cross-sectional view showing the configuration of an ultrasound probe using an acoustic lens that the applicant has already proposed, Figure 2 is a diagram showing an image obtained by the probe, and Figure 3 is a diagram of the present invention. A sectional view showing an example of the configuration of an ultrasound probe in an ultrasound diagnostic apparatus according to the invention, FIG. 4 is a diagram showing an example of an image obtained by the probe, and FIG. 5 is an embodiment of the invention. FIG. 6 is a block diagram showing the ultrasonic diagnostic apparatus in FIG. 1... Ultrasonic transducer, 2, 2'... Acoustic lens, 3... Living body, 6, 6'...
Virtual origin, 11... Transmitter, 12...
Probe, 13... Receiver, 15... Main memory, 17... Line memory, 21...
...Address converter, 24...Monitor. Name of agent: Patent attorney Toshio Nakao and 1 other person No. 1
Figure 2 Figure 3 Figure 4 Figure 5

Claims (2)

[Claims] (1) Ultrasonic detection in which a plurality of ultrasonic transducers are arranged in an arc shape, an acoustic lens is provided between the ultrasonic transducers and the living body, and a predetermined number of the ultrasonic transducers are sequentially selected and scanned. The ultrasonic device is characterized in that the ultrasonic transducer is provided with a probe, and the arrangement shape of the ultrasonic transducer or the shape of the acoustic lens is shaped so that all the scanning lines of the ultrasonic transducer substantially pass through one predetermined point. Sonic diagnostic equipment. (2) The ultrasonic diagnostic apparatus according to claim 1, wherein the surface of the acoustic lens that comes into contact with a living body is a flat surface.