JPS5944052B2 - Ultrasonic diagnostic probe - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an ultrasonic diagnostic probe, and particularly an improved ultrasonic probe capable of obtaining an arbitrary focusing effect of an ultrasonic beam in the transverse direction orthogonal to the scanning direction of the probe. Regarding a probe for ultrasound diagnosis.

2. Description of the Related Art Ultrasonic diagnostic apparatuses that emit an ultrasonic beam into a subject and display images of living tissues such as organs based on reflected echoes generated from differences in acoustic impedance are well known.

In order to transmit and receive ultrasonic beams, a vibrating element made of an electroacoustic transducer such as PZT is excited by an electric signal at an ultrasonic frequency. It is known that the beam spreads and the resolution of the obtained image decreases. Various improvements have been made in the past in order to suppress the above-mentioned scattering of the ultrasound beam and obtain a sharply directional ultrasound beam. There is. FIG. 1 shows the arrangement of the vibrating elements in a conventional probe.
n vibrating elements 10 are arranged in the scanning direction (X-axis). Each vibrating element 10 has a vibrating element length of 2b in the horizontal direction (Y-axis) orthogonal to the scanning direction, and When excited, an ultrasonic beam is emitted in the radial direction (Z-axis) perpendicular to both the scanning direction (X-axis) and the lateral direction (Y-axis), and the excitation of each vibrating element 10 is electronically scan-controlled. By doing so, a scanning plane in the XZ plane can be obtained.

FIG. 2 shows an electronic scanning action using the conventional probe described above, in which a number of vibrating elements arbitrarily selected from a plurality of vibrating elements 10, five vibrating elements each in FIG. By switching and sequentially exciting the element group with repeated pulses 100, a scanning action of a plurality of ultrasonic beams 200 is obtained, and a tomographic image 300 in FIG. 2 is displayed on a display section (not shown).
can be obtained.

As mentioned above, the ultrasound beam has a diffusion effect, and as the depth in the radial direction (Z axis) increases, the tomographic image 300
However, in the conventional device, each vibration element 10
By delay-controlling the timing of transmission and reception of waves to It is possible to obtain an arbitrary focusing effect on the plane, that is, the However, the above-mentioned focusing effect is performed only on the XZ plane, and in conventional devices, it is possible to maintain good directivity in the YZ plane, which is perpendicular to the scanning plane. This resulted in a disadvantage that the final image quality deteriorated.

For example, the length of the vibrating element 2b is 10 m1! If the wavelength λ of the ultrasonic wave is 0.5, the first zero angle of the ultrasonic beam (
The directional sound field of the ultrasonic beam emitted from the vibrating element 10 at this time is shown in Figure 3. As is clear from Figure 3, the radiation depth increases. As a result, the lateral directivity of the ultrasonic beam decreases, resulting in a significant decrease in image resolution, making it difficult to ensure good image quality.

As an improved conventional probe, a probe having a laterally concave ultrasonic beam emission surface was proposed, and this probe made it possible to obtain a lateral focusing effect.
The figure shows a probe in which a concave radiation surface is formed by an arc-shaped vibrating element 10, and FIG. 5 shows the vibrating element 1 of FIG.
0 shows a configuration in which an acoustic lens 12 having a concave radiation surface is closely fixed. In each of the probes, the concave radiation surface has a curvature of R.

With this improved conventional device, a focusing effect in the lateral direction is obtained, and to express this focusing characteristic, D
A constant is used〇This D constant represents the strength of focusing,
The sound pressure at the point of curvature is: For example, if the D constant is 2, the sound pressure 1 becomes approximately 6, making it possible to obtain three times the sound pressure compared to the conventional probe shown in Fig. 1, which does not focus. Therefore, according to the conventional devices shown in FIGS. 4 and 5, it is possible to obtain three times sharper directivity. In FIG. 6, λ=0.5
1t1, R=751! The sound pressure distribution characteristics of the probe with 1 and 2b = 13 are shown, and the D constant is D = 1.
．． 1, and the maximum point of sound pressure is approximately 45W from the radiation surface! l
However, as is clear from the figure, in the conventional device, it is not always possible to obtain a good focusing effect at points other than the desired focusing point. In other words, the conventional probe with a concave radiation surface has a focal point determined by its shape, and the probe must be replaced each time the diagnostic depth is changed. The present invention was developed in view of the above-mentioned conventional problems, and its purpose is to be able to arbitrarily vary the lateral focusing characteristics of an ultrasonic beam, and to An object of the present invention is to provide an improved ultrasonic diagnostic probe that can cover various diagnostic depths with a probe that is arranged along the scanning direction. for ultrasonic diagnosis, including a plurality of vibrating elements, each of the vibrating elements having an ultrasonic beam radiation surface that is concave in the transverse direction to obtain a focusing action of the ultrasonic beam in the transverse direction perpendicular to the scanning direction. In the probe, an acoustic mask is detachably attached to the ultrasonic beam emitting surface of the transducer to arbitrarily change the width of the emitting surface in the lateral direction, so that the lateral focusing characteristics of the ultrasonic beam can be arbitrarily changed. It is characterized by being selectable.

In the present invention, in the above equation (2), even if the condensation rate R is the same, the D constant can be changed by changing the vibrating element length 2b, and the focal point can be changed by changing the D constant. According to the present invention, the desired focusing characteristics can be obtained by arbitrarily adjusting the effective length of the vibrating element in the lateral direction using an acoustic mask. By increasing the amount of shielding and shortening the effective length of the vibrating element, the focal point approaches the radiation surface, and conversely, by increasing the effective length of the vibrating element, the focal point is set farther away from the radiation surface. By arbitrarily selecting the mounting position of the acoustic mask on the vibrating element, it is possible to obtain a desired focusing effect. FIG. 7 shows an embodiment in which the present invention is applied to the conventional device shown in FIG. 4, in which an acoustic mask 14 is attached to the ultrasonic beam emission surface 10a, and similarly, FIG. FIG. 5 shows an example in which an acoustic mask 14 is attached to the concave radiation surface 12a of the acoustic lens 12 in the conventional device. etc., and is removably fixed to each radiation surface 10a, 12a at an arbitrary mounting position by a holding device (not shown).

The acoustic mask 14 absorbs ultrasonic vibration energy with high efficiency, and the ultrasonic beam is not emitted into the subject from the radiation surface on which the acoustic mask 14 is attached. As a result, each radiation surface 10a, By attaching the acoustic mask 14, the effective length of 12a becomes shorter, making it possible to change the D constant shown in equation (2) to an arbitrary value.
2b = 1.4 mm, λ = 0.5 mm, and R = 80 m1 The change in sound pressure distribution characteristics when the acoustic mask according to the present invention is attached to the probe is shown, and characteristic 401 shows the change in the sound pressure distribution characteristic when the acoustic mask 14 is attached. At this time, the D constant is approximately 1.2, and the maximum sound pressure point, that is, the focal point, occurs at a position approximately 52 fins from the radiation surface.In contrast, the characteristic 402 indicates that the acoustic mask 14 with a width of 3 m1 is Vibration elements 10 are mounted on both sides of the radiation surface.
The state in which the effective length of is shortened to 8 is shown, and the D constant at this time is 0.4, and as a result, it is understood that the maximum sound pressure point, that is, the focal point, moves to the 0th position of approximately 24. As is clear from the characteristics shown in FIG. 9, by attaching the acoustic mask 14, it is possible to obtain a good focusing effect at the diagnostic depth of a short distance, and for this reason, in the present invention, adjustment of the radiation surface by the acoustic mask 14 is effective. As described above, according to the present invention, by attaching the acoustic mask to the ultrasonic beam radiation surface at a desired position, it is possible to obtain arbitrary sound pressure distribution characteristics. It is now possible to arbitrarily select the focusing characteristics, and it is now possible to emit an ultrasound beam with the desired focusing characteristics over a wide range of diagnostic depths using a single probe. It significantly increases the range of use and makes it possible to obtain high-quality images with high resolution.

[Brief explanation of the drawing]

FIG. 1 is a perspective view of a conventional transversely focused transducer;
Fig. 2 is an explanatory diagram showing the linear electron scanning effect using the probe of Fig. 1, Fig. 3 is an explanatory diagram showing the lateral ultrasonic beam diffusion effect of the probe of Fig. 1, and Fig. The figure is a perspective view of a conventional improved probe capable of performing a radial focusing action, and FIG. 5 shows another conventional probe capable of performing a radial focusing action using an acoustic lens. Perspective view,
6 is a sound pressure distribution characteristic diagram of the conventional probe shown in FIGS. 4 and 5, FIG. 7 is a perspective view showing a preferred embodiment in which the present invention is applied to the conventional device shown in FIG. 4, and FIG. The figure is a perspective view showing a preferred embodiment in which the present invention is applied to the conventional device shown in Fig. 5, and Fig. 9 is a characteristic diagram showing the focusing characteristic adjustment effect in the embodiment shown in Figs. 7 and 8.〇10 ... Vibration element, 10a ... Radiation surface, 14 ... Acoustic mask.

Claims (1)

[Claims] 1. An ultrasonic beam including a plurality of vibrating elements arranged along the scanning direction, each of the vibrating elements having a concave surface in the transverse direction in order to obtain a focusing action of the ultrasonic beam in a transverse direction perpendicular to the scanning direction. In an ultrasonic diagnostic probe having a radiation surface, an acoustic mask is removably attached to the ultrasound beam radiation surface of the transducer to arbitrarily vary the width of the radiation surface in the lateral direction. An ultrasonic diagnostic probe characterized in that the transverse focusing characteristics of the probe can be arbitrarily selected.