JP2526452B2 - Ultrasonic applicator - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ultrasonic applicator for an ultrasonic warming therapy device, and more particularly to an improvement of an acoustic lens which is joined to an ultrasonic transducer to propagate and focus ultrasonic waves.

[0002]

2. Description of the Related Art Conventionally, heating is applied by forming an ultrasonic heating region 7a in a living body by phase control using a ring-shaped oscillator (annual ray) 4a as shown in FIG. . However, as shown in FIG. 5, unnecessary heating spots are generated behind the heating region 7a.
In order to remove such a heating point, the use of a circular oscillator 4b further divided in the radial direction as shown in FIG. 6 is disclosed in Japanese Patent Laid-Open No. 62-42773.
The heating area 7a is divided into two, and the phases of the focused ultrasonic waves are opposite to each other at a position where an unnecessary heating point 7b behind the heating area 7a occurs, and such an unnecessary heating point is generated. Is proposed to be removed.

However, the proposed radial division oscillator has the drawbacks that the structure of the oscillator becomes very complicated, and the control device to which a delay circuit is added becomes complicated and expensive.

Therefore, the applicant of the present application filed Japanese Patent Application No. 63-141.
According to No. 48, in a hyperthermia device for forming a heating region by focusing ultrasonic waves obtained from this using an ultrasonic transducer through an acoustic lens and deaerated water, the concave portion of the acoustic lens is oriented in the azimuth direction. Disclosed is a hyperthermia device which has a plurality of ridges of ridges and ridges of valleys alternately, and is formed by an oblique plane or a curved surface with equal intervals between the ridges, and it is not necessary to divide the oscillator, and therefore the oscillator We also proposed a drive circuit that is simple and does not cause unnecessary heating points.

[0005]

However, even in the above-mentioned prior invention by the applicant of the present application, there is actually unevenness in the heating distribution at the focusing stage, which is caused by the ultrasonic radiation of the acoustic lens. This is because the ultrasonic wave has uneven distribution due to the thickness of the lens.

It is an object of the present invention to provide an ultrasonic applicator, which is an improvement of the above-mentioned prior invention, in which there is less unevenness in the distribution of ultrasonic waves during radiation, which results in less unevenness in the heating distribution. is there.

[0007]

The above-described object is to provide an ultrasonic transducer, an acoustic lens, and a propagation medium interposed between the acoustic lens and the surface of the body to be irradiated, and the concave portion of the acoustic lens is In an ultrasonic applicator having a plurality of mountain ridges and valley ridges alternately in the azimuth direction, and forming an inclined flat surface or curved surface at equal intervals between both ridges, the mountain ridge and valley ridges The thickness change width L is within 1/2 of the wavelength λ of the ultrasonic wave, and the relationship of 3VM <VL is established between the sound velocity VM in the propagation medium and the sound velocity VL in the acoustic lens. This will be achieved.

[0008]

As a means for converging the ultrasonic waves, an acoustic lens is used, and an inclined plane or a curved surface is continuously formed in the concave surface portion thereof, which continuously gives a portion where at least one wavelength shift occurs. At that time, no discontinuous portion is formed between the inclined planes. By reducing the unevenness of the radiation distribution of ultrasonic waves by setting the above-mentioned conditions, the unevenness of the heating distribution is reduced, so that the temperature rise becomes uniform and the burden on the patient can be reduced.
Further, since the concave surface portion of the acoustic lens configured as described above is an aspherical surface, by rotating the concave surface portion, a more uniform heating region can be obtained.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT A preferred embodiment of the present invention is described with reference to FIGS. FIG. 1 is an exemplary diagram showing the configuration of a main part of the first embodiment. In this figure, the high frequency obtained from the oscillator 1 is amplified by the amplifier 2 and sent to the ultrasonic transducer 4 through the matching circuit 3. The ultrasonic waves obtained from the ultrasonic transducer 4 are sent to the living body 7 through the acoustic lens 5 and degassed water 6 as a sound wave propagation medium. Thus, the ultrasonic applicator is composed of the ultrasonic transducer 4, the acoustic lens 5, and degassed water.

FIG. 2 is a front view of a half section showing an example of an acoustic lens according to the present invention, and FIG. 3 is a bottom view or a development view of a concave surface portion. As shown in this figure, the acoustic lens has a variation width L of thickness due to unevenness. R is the radius of curvature. Z is the distance between the lens bottom surface and the center of curvature. Reference numeral 5a is a central recessed portion, and 5b is a stepped portion. These portions are necessary only for processing when an acoustic lens is made of metal such as aluminum. Reference numeral 5c is a ridgeline of a mountain, and 5d is a ridgeline of a valley, which are formed at equal intervals in the azimuth direction, and a slant plane portion 5e is formed between the two ridgelines 5c and 5d.

As shown in FIG. 3, for one sloping plane portion 5e, for example, the ridge line 5c of the mountain and the one-dot chain line 5f of the intermediate radial direction line of the sloping plane portion 5e are in opposite phase to each other in the case of focusing. . Further, the radial line 5g forming an angle α from the ridgeline 5c of the mountain and the radial line 5h forming the same angle α degrees from the one-dot chain line 5f are also in opposite phases.

With respect to the entire inclined plane 5e thus configured,
That is, one wavelength is continuously deviated in the circumferential direction, the phases are opposite to each other, and the ultrasonic waves cancel each other. Therefore, by using such an acoustic lens, a sound field in which an unnecessary heating point does not occur at the focus position is formed. The acoustic lens is
In addition to aluminum, acrylic, polystyrene, and other materials that are higher than the speed of sound of water are selected. Further, when the acoustic lens is made of aluminum, machining is efficient by numerical control. In that case, for example, the radius of curvature R and the center of curvature Z
Is used as a parameter to determine the processing conditions for each angle in the circumferential direction from the azimuth reference line.

Here, when the sound velocity VM in the degassed water or the sound wave propagation medium 6 and the sound velocity VL in the acoustic lens 5 are set, the maximum change in the thickness of the acoustic lens 5 is set to L. Ideally, this change in thickness causes the cancellation of ultrasonic waves, where L is the frequency f and T is the period, L / VM-L / VL
= T ... Equation 1 When this equation 1 is transformed,
L = T / (1 / VM-1 / VL) .. Equation 2 is obtained,
In the limit range (thickness change width) L considering the efficiency with respect to the thickness of the acoustic lens, it is necessary to set L <λ / 2, so T / (1 / VM-1 / VL) <λ / 2 ... 3 holds, λ = T · VL is obtained from T = λ / VL, and this is substituted into the right side of Expression 3 to obtain T / (1 / VM−1 / V
L) <T · VL / 2 ·· Equation 4 holds. Eliminating and rearranging T on both sides of this equation 4, 2VL · VM <VL
(VL-VM) is obtained, and both sides are divided by VL, so that 3VM <VL is established. This means that the point where the ultrasonic wave is unevenly distributed due to the thickness of the acoustic lens 5 is within a range where the unevenness is not so noticeable if the above relational expression is satisfied.

FIG. 4 is a cross-sectional view of an essential part showing the same one as the embodiment shown above. Reference numeral 5 is an acoustic lens having the same configuration. The ultrasonic wave generated by the oscillator 4 is focused by the acoustic lens 5,
It is shot through the degassed water 6 and bolus 9 to the whole. 1
0 is the entrance and exit of degassed water. The degassed water 6 is sent to a cooling circulation device (not shown) through a degassed water inlet / outlet port 10, converted to a constant temperature, and then enters the bolus 9 from another inlet / outlet port again. The portion holding the oscillator 4 and the acoustic lens 5 by the motion O-ring 11 is a bolus 9
It is rotatable relative to (the part that comes into contact with the part to be inspected). By such rotation, the isothermal distribution of the heating region spreads concentrically, the heating region is uniformly heated, and its effect is enhanced when applied to the heating treatment. Therefore, if such rotation is applied after satisfying the relational expression as described above, a synergistic effect is obtained in that the unevenness of the heating distribution is reduced. The rotating means 12 is not particularly limited and can be selected from various known mechanisms.

[0015]

[Effects] According to the present invention, since it is not necessary to divide the vibrator, the vibrator and its drive circuit are simple, and the acoustic lens according to the present invention does not cause unnecessary heating points.
Further, since the distribution of ultrasonic waves is evenly and uniformly radiated, it is possible to inexpensively provide an ultrasonic applicator whose heating region is obtained by uniform heating.

[0016]

[Brief description of drawings]

FIG. 1 is an exemplary diagram showing a main part configuration showing an embodiment of the present invention.

FIG. 2 is a front view showing an example of an acoustic lens according to the present invention.

FIG. 3 is a bottom view or a developed view of a concave portion.

FIG. 4 is a cross-sectional view of another preferable main part.

FIG. 5 is an explanatory diagram of generation of a heating region using an ultrasonic transducer of a conventional example.

FIG. 6 is a similar view using another conventional ultrasonic transducer.

[Explanation of symbols]

 4 Ultrasonic transducer 5 Acoustic lens 6 Degassed water or sound wave propagation medium 7 Irradiation object 5c Mountain ridgeline 5d Valley ridgeline 9 Bolus 10 Degassed water inlet / outlet 11 Exercise O-ring L Variation range of thickness due to unevenness

Claims (1)

(57) [Claims] 1. An ultrasonic transducer, an acoustic lens, and a propagation medium interposed between the acoustic lens and the surface of an object to be irradiated, wherein the concave portion of the acoustic lens has a plurality of ridge lines in the azimuth direction. In an ultrasonic applicator that has alternating ridges and valley ridges and is formed by oblique planes or curved surfaces that are equally spaced between the ridges, the variation width L of the thickness between the ridgeline of the ridge and the ridgeline of the valley is very large. Within the half wavelength λ of the sound wave, and between the sound velocity VM in the propagation medium and the sound velocity VL in the acoustic lens, a relationship of 3VM <VL is established. Sonic applicator.