JPS6145457B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention is used when connected to an ultrasonic diagnostic device, transmits ultrasonic waves to a subject, receives the reflected waves, and converts them into electrical signals to perform ultrasonic diagnosis. The present invention relates to an ultrasonic probe that can be sent back to the main body of the device and is equipped with an acoustic lens that narrows the transmitted ultrasonic beam in the thickness direction.

An example of a conventional ultrasonic probe of this type is shown in FIG. In the same figure, 1 is a large number of thin rectangular oscillators.
The array transducer consists of E ₁ , E ₂ , E _o-1 , E _{o ,} and 2 is an acoustic cylindrical lens made of a rubber-like material or the like bonded to the surface of the array transducer 1 . Oscillators E ₁ , E ₂ , E _o-1 , E _o
is energized by a drive signal given from the main body of the ultrasonic diagnostic apparatus (not shown), and generates ultrasonic waves.
This ultrasonic beam emitted in the Z-axis direction is focused by the lens 2 in the Y-axis direction (thickness direction), which is perpendicular to the arrangement direction (longitudinal direction) of the transducers E ₁ to _{E o} .
Near the focal point of the lens 2, the beam has a substantially uniform width W. In this case, the beam width in the longitudinal direction is narrowed down by phase-driving the vibrator. However, in such an ultrasonic probe, the lens cross section is convex, and the lens thickness is maximum at the center, which determines the quality of the image, and the energy loss of reflected waves passing through this center is maximum. As a result, the S/N ratio of the received echo signal decreases, making it difficult to obtain an image of as high quality as expected. As a solution to this problem, it is also known to use a concave cylindrical lens made of a different material (the magnitude relationship of the sound velocity with respect to the subject is opposite to that of a convex lens) instead of a convex lens. However, with this probe, although the energy loss of the reflected waves can be reduced in the central part, the closeness to the body surface is poor and a void is created, so overall the reduction in energy loss in the central part in the thickness direction is almost negligible. The problem was that I couldn't expect it. Furthermore, it is generally considered desirable that the beam aperture be set in accordance with the depth to the target object from which the beam is reflected, that is, a small aperture for a shallow region and a large aperture for a deep region. However, the above-mentioned probe always has a constant aperture, which poses a problem in that it is difficult to obtain high-quality images.

In view of these points, the present invention is designed so that the energy loss in the central part is not greater than that in the peripheral part, and the beam aperture width in the thickness direction is automatically widened according to the depth of the diagnostic site. The purpose of this invention is to provide an ultrasonic probe.

The present invention will be explained in detail below using the drawings. FIG. 2 is a cross-sectional configuration diagram showing an embodiment of the ultrasonic probe according to the present invention. This figure differs from FIG. 1 in that the lens 21 is made of materials with different acoustic properties. That is, the central portion is made of material A, the sides thereof are made of material B, and both peripheral portions are made of material C. The acoustic properties of each material, that is, the attenuation properties of ultrasonic energy, are, for example, 1 dB/cm/MHz for material A and 2 dB/cm/MHz for material B.
cm/MHz, and material C is 3 dB/cm/MHz.

In such a configuration, it is assumed that the drive frequency of the vibrator 1 is 3.5MHz. It is known that the frequency of ultrasound propagating within a living body becomes lower as the length of the propagation path becomes longer. Therefore, the sound waves reflected from the target object 31 located at a shallow part of the subject 30 as shown in the drawing reach the lens 21 with almost no change and at a frequency of approximately 3.5 MHz. This 3.5 MHz reflected wave is lowered by 3.5 dB when passing through material A at the center, by 7 dB at material B, and by 10.5 dB at material C at the periphery before reaching the vibrator 21. This means that only the sound waves that have passed through the material A portion mainly contribute to the vibrator 21. Therefore, the wave receiving aperture in this case is a narrow aperture having the width of the material A portion. on the other hand,
The sound waves reflected from the target object 32 located deep inside the subject 30 have a long path, for example, 1M.
If it comes down to Hz, material A
dB in the material B part, 2 dB in the material B part, and 3 dB in the material C part. That is, in this case, there is almost no difference in energy loss between the materials, and the vibrator 1 receives the reflected wave using the entire thickness of the lens 21 as an aperture. In other words, waves can be received with a wide aperture.

Note that the lens 21 is not limited to being formed in multiple layers using a material having three levels of characteristics as in the embodiment, but may also be formed in multiple layers using a material that is further subdivided into multiple levels.
With a lens formed in this way, it is possible to realize an ultrasonic probe whose aperture changes more closely.

Further, the transducer 1 is not limited to the linear array type, but may be a curved array transducer as shown in FIG. 3. Of course, the lens 21 in this case is integrated with the transducer 1 and curved in the longitudinal direction.

As explained above, according to the present invention, with a simple configuration, by skillfully utilizing the frequency characteristics of ultrasonic waves in the subject, reflected waves from shallow areas can be detected at the central part in the thickness direction. It is possible to create an ultrasonic probe with a so-called automatic variable aperture, which can receive waves with a narrow aperture and receive waves reflected from deep parts with a wider aperture, guaranteeing high-quality images. It has the effect of

[Brief explanation of the drawing]

FIG. 1 is a configuration diagram of a conventional ultrasound probe, FIG. 2 is a cross-sectional configuration diagram showing one embodiment of an ultrasound probe according to the present invention, and FIG. 3 is another embodiment of the present invention. FIG. 1...Array transducer, _E1 ~ _Eo ...
Oscillator, 21...Cylindrical lens.

Claims (1)

[Claims] 1. In an ultrasound probe in which an acoustic cylindrical lens is bonded to the surface of an array transducer to focus an ultrasound beam in the thickness direction, the cylindrical lens has a multilayer structure in the thickness direction, and the center An ultrasonic probe characterized in that the lower layers are made of a material whose attenuation of ultrasonic energy is smaller.