JPH0113532B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an ultrasonic imaging device for use in an ultrasonic imaging device that projects ultrasonic waves onto a subject, receives the reflected waves, and obtains a tomographic image of the subject based on the signal. It concerns the probe.

Conventionally, so-called linear scanning is performed in which a plurality of strip-shaped transducers are arranged in a straight line to form a transducer array, and n transducers are sequentially scanned as a set while shifting one transducer one by one. There is an ultrasonic probe that scans a beam of sound waves. In such a linear scanning type probe, the scanning line spacing is equal to the center spacing of adjacent transducers, so in order to make the scanning lines denser, the transducers must be made thinner. However, if the transducer is made thinner, the beam will spread, so in order to have sharp directivity, it is necessary to have a certain width. Therefore, there is a drawback that the scanning line spacing cannot be made denser than a certain limit.

On the other hand, according to so-called sector scanning, in which n transducers are phase-driven and the beam is swung in a fan shape by sequentially changing the phase, it is not possible to make the scanning line spacing dense regardless of the center spacing of the transducers. However, the scanning lines of such sector scanning are not parallel as in the case of linear scanning, but are spread out in a fan shape, so there is a problem that the spacing between the scanning lines increases as the depth increases. Attempts have also been made to increase the spacing between scanning lines by combining sector scanning with a small deflection angle and linear scanning. There is a problem that it leads to

An object of the present invention is to eliminate such drawbacks and provide an ultrasonic probe that can generate parallel scanning lines extremely densely with a simple configuration, regardless of the center spacing of the transducers. It's about doing.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described in detail below using examples and drawings. FIG. 1 is a diagram showing the configuration of essential parts of an embodiment of an ultrasonic probe according to the present invention. In the figure, reference numeral 1 denotes a transducer array consisting of a plurality of rectangular transducers arranged in a plane, for example, 10 transducers.
They are arranged at 2.54mm intervals. 2 is a backing material adhered to the back surface of the transducer array, 3 is a housing that houses a propagation medium 4 for propagating ultrasonic waves, and 5 is an acoustic lens made of a material such as acrylic. As the propagation medium 4, water, gel, or the like with low propagation loss is used, and the casing 3 is formed of an acrylic resin plate or the like. The casing 3 has the transducer array 1 attached to its upper end, and is formed in a fan-like shape toward the lower end. The lower end portion of this housing 3 is formed so as to be in close contact with the curved surface 51 of the acoustic lens 5. For example, if the propagation medium 4 is water, the lower end may be made of a thin film of rubber or the like. Depth (thickness) of the housing 3 and acoustic lens 5
The direction is substantially uniform and flat as shown in FIG. 1B. FIG. 3 is a diagram showing a drive circuit for the vibrator array 1, in which each vibrator 1 ₁ , 1 ₂ , . . .
..., 1n include delay circuits 31 ₁ , 31 ₂ ,
......, 31n are connected to each other. A transmitting circuit 32 and a receiving circuit 33 are commonly connected to these delay circuits, so that a vibrator excitation signal and an echo signal from the vibrator are transmitted and received. These delay circuits delay signals by a predetermined amount of time, and the delay time can be appropriately determined by a controller (not shown). By setting an appropriate delay time, the acoustic beam can be narrowed over a wide range before and after the focal point (so-called electronic focusing). Next, the shape of the curved surface of the lens 5 will be described in detail. Let us now assume that the sound velocity in the propagation medium 4 is V ₁ and the sound velocity in the lens 5 is V ₂ (V ₂ > V ₁ ), and the ultrasonic beam is set at the center of the transducer array (point A) for the sake of simplicity. ). Second
As shown in the figure, in order for the sound wave that has come out from point A and passed through the propagation medium 4 to be sent out at right angles from the lower end surface through the lens 5, the shape of the curved surface 51 of the lens 5 must be an ellipse that satisfies the following formula. It must be a curved line.

Here, f is the focal length related to this curve, V ₁ is the speed of sound in the propagation medium, and V ₂ is the speed of sound in the acoustic lens (V ₂ >V ₁ ).

Note that a substantially sufficient effect can be obtained by using a circular arc curve instead of an elliptic curve. Due to such a curved surface, a beam is projected from the lower end surface of the acoustic lens 5 in a direction substantially perpendicular to that surface.

By the way, the transducer array 1 is phase-driven with an appropriate time delay in a delay circuit in order to focus the emitted beam. By arbitrarily changing the deflection angle θ of the ultrasonic beam shown in
Sector-like scanning can be performed. When sector scanning is performed in this manner, the projection beam moves leftward or rightward on the lower end surface of the acoustic lens 5, as shown in FIG. 1A, resulting in so-called linear scanning. Note that the reflected wave also passes through the same wave path as the projected wave.

In the above explanation, in Fig. 2, the sound wave beam is
Although it is shown as a line in the book, it actually has a certain width as shown in Figure 1.

The interval between the respective acoustic beams projected into the subject in this way, that is, the interval between the scanning lines, depends on the deflection angle θ of the beam in the propagation medium 4, and this deflection angle θ is determined by the delay circuits 31 ₁ , 31 It is determined by the delay time of ₂ , . . . , 31n. Therefore, by appropriately controlling the delay time, the interval between linearly scanned scanning lines can be arbitrarily controlled, and the interval can be easily made dense. The linear scanning line spacing can be set to, for example, 1 mm, or can be made arbitrarily coarse or dense depending on the location.

FIG. 4 shows another embodiment of the present invention, which differs from the one in FIG. 1 in that a convex acoustic lens 5' is used in place of the concave acoustic lens 5. In this case, the acoustic lens 5' is formed of a material such that the sound velocity V ₂ ' in the lens is greater than the sound velocity V ₁ in the propagation medium, and its convex curved surface 51' is as shown in FIG. It is formed into a hyperbola that satisfies the following equation with respect to the x-y axes.

In this case as well, instead of the hyperbola, it may be formed into a curved surface approximated by a circular arc curve with a radius of curvature R expressed by the following equation.

R=f(V ₁ /V ₂ -1) The same purpose as the probe shown in FIG. 1 can also be achieved with such an acoustic lens.

Note that although the beam width in the scanning direction can be narrowed down by electron focusing, the beam width in the thickness direction cannot be narrowed down. Therefore, an acoustic lens may be formed in the shape shown in FIG. 6 so that the beam can be focused in the thickness direction. That is,
A in FIG. 6 is a case in which the curved surface 51 is concave in the thickness direction, B in FIG. 6 is a case in which the lower end surface of the lens 5 is concave, and A in FIG. 6 is a case in which the curved surface 51' is convex. , C in FIG. 6 shows that the lower end surface of the lens 5' is made convex. Alternatively, the transducer array 1 may be curved in the thickness direction to narrow the beam without changing the lens shape. Further, the transducer array section and the housing 3 may be configured to be detachable so that they can be easily attached to a probe dedicated to sector scanning.

As explained above, according to the present invention, since the acoustic beam emitted from the transducer array is configured to pass through the acoustic lens capable of post-sector linear conversion via the propagation medium, the transducer array is phase-driven. By controlling the phase difference, it is possible to realize an ultrasonic probe in which the scanning line spacing can be easily made dense without changing the arrangement spacing of the transducers.

[Brief explanation of drawings]

FIG. 1 is a configuration diagram showing an embodiment of the ultrasonic probe according to the present invention, FIG. 2 is a diagram for explaining the curved surface of the acoustic lens 5, and FIG. 3 is a diagram showing the main components of the drive circuit for the transducer array. 4 is a diagram showing another embodiment of the present invention, FIG. 5 is a diagram for explaining the curved surface of the acoustic lens 5', and FIG. 6 is a diagram showing another embodiment of the acoustic lens. 1... Vibrator array, 3... Housing, 4... Propagation medium, 5, 5'... Acoustic lens, 51, 51'...
Curved surface, 6...Object.

Claims (1)

[Scope of Claims] 1. A transducer array formed by arranging a plurality of transducers linearly, and a propagation medium for propagating ultrasonic waves, the transducer array is adhered to one end, and the transducer array is bonded to one end of the transducer array. A housing is formed to widen toward the other end, and a material is used that is bonded to the other end of the housing and has a sound velocity faster than the sound velocity of the propagation medium, and Equipped with an acoustic lens to direct all the sound wave beams passing through the medium in the same direction, each vibrator of the transducer array is driven with appropriate phase, so that the sound wave beam scanned in sectors in the propagation medium becomes acoustic. An ultrasonic probe characterized in that the lens is scanned linearly.