JPH05200029A - Ultrasonic wave diagnosing device - Google Patents

Abstract

PURPOSE:To provide a ultrasonic tomographic image with simple circuit constitution and uniform high resolution by providing a concave aspheric surface transducer having the smallest radius of curvature near the central portion and the larger radius of curvature nearer the outer periphery to have a wide range of focus on the center axis of the concave surface. CONSTITUTION:A probe 20 is composed of fine portions of N transducers from 20-1 to 20-N. The central fine portion 20-1 is provided to have the nearest focus G1 at the focal distance, and as the fine portion is brought toward the outside, its focus is placed gradually at more remote position and the outermost fine portion 20-N is set to have the focus at the remotest position GN so that the focus region is expanded in the direction of depth. By focusing the ultrasonic wave beams in a wide range the actual foci can be prevented from being pulled by the focus in the transmission and deviated from the focus in the reception even when the receiving dynamic focusing is performed by the transducers divided in the ring-like form.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ultrasonic diagnostic apparatus for transmitting and receiving ultrasonic waves to and from a subject and obtaining ultrasonic tomographic images based on the received reflected waves. The present invention relates to an ultrasonic diagnostic apparatus characterized in that an ultrasonic beam is focused by means of.

[0002]

2. Description of the Related Art Conventionally, in an ultrasonic diagnostic apparatus for transmitting and receiving ultrasonic waves by a concave transducer to obtain a tomographic image, since the concave transducer has a spherical shape, the ultrasonic beam is focused at one point. .

Referring to FIG. 3, when an ultrasonic pulse is transmitted from the vibrator 1 having a spherical shape, the ultrasonic pulse is focused at the center O of the spherical surface. That is, the focus (F0) can be set by making the shape of the vibrator spherical.

The point F0 is also the focal point in reception. When such a focal point is set, a high resolution can be obtained near the focal point (F0), but a sufficient resolution can be obtained in a portion away from the focal point (F0). Was not obtained, and a good ultrasonic tomographic image could not be obtained over a wide range.

In order to improve this drawback, that is, in order to focus the ultrasonic beam in a wider range, the diameter of the vibrator was reduced, but at the same time, the sensitivity was lowered.

Further, in order to improve this drawback, the concave vibrator is divided into a ring shape and the reception dynamic focus is used. If the number of divisions is small, the focus (F
Other than 0), the ultrasonic beam cannot be focused, and the physical quantity and the cost are increased to realize the receiving dynamic focus.

The reception dynamic focus is a method of giving a delay time to a reception signal received by each vibrating element and changing the delay time according to the focal length to obtain an ultrasonic tomographic image. Explaining with reference to FIG. 4, the reflected wave from the focal point F0 has no time delay as described above, and each vibrating element 10-1.
The reflected wave from a point F1 near the focal point F0 reaches the ring-shaped vibrating element 10-1 at the center of the transducer row 10 the earliest and is received by the focal point F0. The vibration element 10-16 arrives at the latest. By correcting this time delay by the delay circuit 11 and aligning the phases of the signals received from the respective vibrating elements, the focus at the time of reception can be set to the point F1. Reception dynamic focus is a method in which the delay time set by this delay circuit is changed and the focus position is appropriately set by this to widen the focus range during reception.

[0008]

Since the conventional concave transducer has a spherical shape, the ultrasonic beam is focused on the focal point F0 determined by the concave shape of the transducer during transmission. Therefore, there is a problem that the actual focus is shifted to the focus F0 side even when the receiving dynamic focus is performed by the concave vibrator divided into the ring shape as described above.

This will be described with reference to the drawings. FIG. 5 shows the case where the transmission focus and the reception focus match at F0. As described above, the ultrasonic wave transmitted from each transducer maximizes its sound pressure level 101 at the focus F0. Also in reception, the sound pressure level 102 becomes maximum at the focus F0, and the total sound pressure level 103 also becomes maximum at the point F0, and this point becomes the focus. However, when the transmission focus and the reception focus do not match as shown in FIG. 6, the maximum value of the summed sound pressure level 113, which is the sum of the sound pressure levels 111 and 112, is neither the point F0 nor the point F1. This is the point F10, which is the focus. This phenomenon in which the actual focus shifts to the transmission focus F0 is especially at the point F0.
This is remarkable in the vicinity. Therefore, even if the focal points set by the receiving dynamic focus are evenly spaced, the actual focal points are not equally spaced, and a uniform ultrasonic tomographic image cannot be obtained.

The present invention has been made to solve the above-mentioned problems, and an ultrasonic diagnostic apparatus capable of obtaining an ultrasonic tomographic image having a uniform and high resolution over a wide range is provided by a simple circuit configuration. To aim.

[0011]

In the ultrasonic diagnostic apparatus according to the present invention, the concave vibrator has an aspherical shape so that each minute portion constituting the vibrator has a different focus. .

[0012]

Since the minute portions forming the vibrator have different focal lengths, the ultrasonic beam can be focused over a wide range.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT A preferred embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 shows a schematic view of the ultrasonic probe of this embodiment. The probe 20 is composed of a minute portion of N oscillators 20-1 to 20-N. The minute portion 20-1 at the center of the vibrator is arranged so that its focal length becomes the nearest point G1. Then, the focus position is arranged so that it gradually becomes farther toward the outside of the vibrator. In the outermost minute portion 20-N of the oscillator, the focus is set to the farthest point GN.

Therefore, the vibrator 20 is arranged so that its radius of curvature gradually increases from the inside to the outside. According to the embodiment shown in FIG. 1, in the case of the present embodiment, the focus of each minute portion of the vibrator is set separately in order to make the focus region wide in the depth direction. The focal point is set from G1 to GN, and the closest point is G1 and the farthest point is GN as described above. The minute portion 20-1 of the vibrator whose focus is set to the nearest point
Is a spherical surface 20 whose center is its focal point G1 and whose radius is the distance (focal length) from the center point T of the probe 20 to the focal point.
It is arranged above 1. The small portion 20-I of the oscillator near the center is on the spherical surface 20I with the focal point GI as the center and the distance between the focal point GI and the point T (focal length) as the radius.
It is located in. The focal length TGI at this time becomes larger than the above-mentioned focal length TG1, and therefore the radius of curvature becomes large. Furthermore, the minute parts 20-N of the vibrator at both ends
, The focal point is located on a spherical surface 20N having a GN radius as a focal length TGN. The radius of curvature at this time is larger than the radius of curvature. Thus, the arrangement of the minute portions of the three vibrators has been described,
Similarly, it is possible to widen the focal area of other minute portions by gradually changing the focal position and arranging it on a spherical surface corresponding to the focal position.

By focusing the ultrasonic beam in such a wide range, the actual focus is pulled to the focus at the time of transmission even when the dynamic focusing for reception is performed by the transducer divided into the ring shape. It is possible to prevent the time from being out of focus. That is, as shown in FIG. 2, the sound pressure level of the transmitted ultrasonic wave does not have a peak, and the phenomenon in which the focus shifts to the focal point side at the time of transmission as described above even in the sum with the sound pressure level at reception. Absent.

As described above, in the present embodiment, the respective set focal points are set as the centers, and they are arranged on a plurality of spherical surfaces inscribed at the center point T of the probe, but the points T are shared. It is not necessary that the vibrating elements forming a pair are arranged equidistant from the corresponding focal point.

Further, in the present embodiment, the ring-shaped divided vibrator has been described. However, even a non-divided vibrator may have a shape in which the focus position gradually becomes farther from the inside to the outside of the vibrator. Good.

[0019]

As described above, by setting different focal points for each minute portion of the vibrator, it is possible to obtain a high resolution in a wide range in the distance from the probe. Moreover, the number of transmissions can be reduced when one scan data is obtained by transmission dynamic focus using the transducers divided in a ring shape. Also, when performing the receiving dynamic focus, the actual focus synthesized by transmission and reception becomes the focus at the time of reception, and it is possible to suppress the occurrence of the valley of the focus.

As described above, according to the present invention, an image having a high resolution and a uniform resolution can be obtained without reducing the frame rate.

[Brief description of drawings]

FIG. 1 is a diagram illustrating an arrangement of transducer elements of a probe of an ultrasonic diagnostic apparatus according to the present invention.

FIG. 2 is a diagram showing a relationship between reception and transmission focal points of the ultrasonic diagnostic apparatus according to the present invention.

FIG. 3 is a structure explanatory view of a conventional concave vibrator.

FIG. 4 is an explanatory diagram of dynamic focus.

FIG. 5 is a diagram showing the relationship between reception and transmission focal points, and is a diagram in the case where the respective focal points are the same.

FIG. 6 is a diagram showing a relationship between reception and transmission focal points, and is a diagram when respective focal points are different.

[Explanation of symbols]

 11 Delay circuit 20 Ultrasonic probe

Claims (2)

[Claims] 1. An ultrasonic diagnostic apparatus for transmitting an ultrasonic pulse by a predetermined concave transducer, receiving an ultrasonic pulse reflected from a subject, and obtaining an ultrasonic tomographic image based on the received reflected wave. The ultrasonic transducer is an aspherical surface, in which the radius of curvature is smallest near the center of the concave surface, and the radius of curvature becomes larger toward the outer peripheral portion, and has a wide range of focal area on the central axis of the concave surface. apparatus. 2. The ultrasonic diagnostic apparatus according to claim 1, wherein the concave vibrator is a divided vibrator.