Ultrasonic medical treatment apparatus

Abstract: An ultrasonic medical treatment apparatus having a piezoelectric transducer assembly (11) for generating ultrasonic energy is provided. The assembly is constituted by a plurality of unit piezoelectric transducer elements (13a-h, 14a-h) of two or more different shapes. The surface areas of these unit elements (13a-h, 14a-h) are substantially equal to each other. The unit elements (13a-h, 14a-h) are individually removable.

Description: This invention relates to an ultrasonic medical treatment apparatus for use in giving medical treatment to a human body with ultrasonic energy, and more particularly to an applicator for use in such treatment. A shock wave type apparatus for destroying calculuses (kidney stones) has received practical application. The apparatus utilizes shock wave energy generated by an electric discharge or by explosion. However, in recent years, the use of focused ultrasonic energy to destroy calculuses in a human body has become feasible. This method has become of major interest as a substitute for the utilization of shock wave energy. This is because the use of ultrasonic energy can result in a significant reduction in the size and the manufacturing cost of calculus-destroying apparatus. In addition, such apparatus requires substantially no expendable materials. The conventional applicator for use in ultrasonic calculus-destroying apparatus has a spherical piezoelectric element that generates ultrasonic energy and concentrates the same on the focal point thereof; see e.g. EP-A-0 209 053, figure 14. The piezoelectric element type calculus-destroying apparatus usually generates acoustic energy smaller than that generated by an electric discharge shock wave type apparatus, when both have an applicator of the same area. Thus, in order to obtain the necessary acoustic energy, a piezoelectric element having a relatively larger area is required. However, such a piezoelectric element is usually made of ceramics. Thus, the size of a single concave piezoelectric element is inevitably limited. Therefore, a plurality of unit piezoelectric elements are combined so as to form the necessary area in combination. FIGURES 4a through 4c show conventional applicators manufactured by the combination of unit piezoelectric elements. FIGURE 4a shows an applicator formed by combination of plural circular concave piezoelectric elements 1a through 1g , which are all the same size. In this case, there are gaps between adjacent concave elements 1a through 1g . Thus, these gaps decrease the space factor of the applicator. FIGURE 4b shows an applicator made by combination of plural hexagonal concave elements 2a through 2g . This applicator has a space factor higher than that of the applicator of FIGURE 4a . However, the outside diameter of this applicator is limited. Moreover, at the center of this applicator, a hole for inserting an imaging ultrasonic probe is often provided. Thus, the space factor of this applicator decreases at the periphery thereof. FIGURE 4c shows an applicator provided with auxiliary small-size elements 3a through 3f that fill the periphery thereof. However, in general, the individual elements are respectively connected to plural separate driving circuits. Thus, when plural elements having different surface areas are used, the electrical loads of such driving circuits are varied in proportion to the respective surface areas. Thus, plural driving circuits with specifications different from each other are required. As a result, the apparatus becomes cumbersome and complicated. Moreover, this raises the manufacturing costs thereof. FIGURE 5 shows another conventional ultrasonic medical treatment applicator. In FIGURE 5 , an ultrasonic medical treatment applicator 4 has a base plate 5 . The internal surface of base plate 5 is formed in a spherical configuration. As can be seen from the drawing, a plurality of unit elements 6 of equilateral hexagons are combined and adhere to the base plate 5 so as to constitute the applicator 4 . The plural unit elements 6 are fixed such that ultrasonic energy generated from these elements 6 is accurately concentrated on a focal point. Thus, once the unit elements 6 are fixed accurately, the ultrasonic medical treatment applicator 4 functions steadily without being out of focus, and it is free from undesirable dispersion of the ultrasonic energy. However, as described above, the unit elements 6 are made of ceramics. Thus, these elements 6 are susceptible to damage during the process of manufacturing the applicator 4 or its operation. Actually, it is not a rare case that even when the ultrasonic medical treatment applicator 4 is used, some of unit elements 6 are found to be defective. Such defectives of the unit elements 6 decrease the generation of ultrasonic energy. Moreover, the unit elements 6 are fixed to the base plate 5 so as to be united therewith. Thus, the entire ultrasonic medical treatment applicator 4 , per se, must be replaced. Otherwise the maximum performance thereof cannot be completely insured. As described above, in the conventional ultrasonic medical treatment applicator, there are problems as follows. When plural unit elements identical in size and shape are used, the space factor of the applicator decreases. When plural unit elements with surface area different from each other are used in combination, the driving circuits therefor become complicated. Moreover, in the conventional ultrasonic medical treatment applicator, plural unit elements are fixed to the base plate in order that the focuses of these elements invariably coincide with each other. However, this causes disadvantages in that when only a part of the unit elements become defective, the whole applicator must be replaced. Accordingly, one object of the present invention is to provide an ultrasonic medical treatment apparatus with an applicator having a maximum space factor within the specified shape thereof. Another object of the present invention is to provide an ultrasonic medical treatment apparatus with an applicator that can readily maintain the ultrasonic energy generated by an ultrasonic element at a maximum amount. Accordingly the present invention provides an ultrasonic medical treatment apparatus comprising: an ultrasonic transducer assembly (11) for emitting ultrasonic energy, wherein said transducer includes a plurality of unit transducer elements (13, 14) of two or more different shapes, but all having surface areas which are substantially equal, and wherein each said unit element is individually detachable. BRIEF DESCRIPTION OF THE DRAWINGS A more complete appreciation of the invention and many of the attendant advantages thereof will be readily obtained as the same becomes better understood by reference to the following detailed description when considered in connection with the accompanying drawings, wherein: FIGURE 1 is a plan view illustrating one embodiment according to the present invention; FIGURE 2 is a partially enlarged back side view of the embodiment of FIGURE 1 ; FIGURE 3 is a cross-sectional view taken along line A-A of FIGURE 1 ; FIGURES 4a through 4c are plan views of conventional examples; and FIGURE 5 is a plan view illustrating another conventional example. DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring now to the drawings, wherein like reference numerals designate identical or corresponding parts throughout the several views, and more particularly to FIGURE 1 thereof, one embodiment of this invention will be described. In FIGURE 1 , a piezoelectric element 11 of an applicator (hereinafter, simply referred to as element) is formed in a circular concave shape of about 40 cm in diameter. At the center portion of the element 11 , a hole 12 of about 8 cm in diameter is provided. This hole 12 is used for inserting an imaging ultrasonic probe (not shown). The element 11 is constituted by sixteen unit piezoelectric elements (hereinafter, simply referred to as unit element) of two different shapes. Namely, eight unit elements 13a through 13h and eight unit elements 14a through 14h are provided. Specifically the shapes of the two kinds are formed such that the entire shape of element 11 is divided radially into eight portions. Further, the thus divided eight portions are each respectively divided into two portions in a concentric configuration with respect to the center hole 12 . The eight portions inside the concentric circle are fan-shaped unit elements 13a through 13h . The eight portions outside the concentric circle are fan-shaped unit elements 14a through 14h . The diameter of the concentric circle is determined such that all the unit elements 13a through 13h and 14a through 14h are identical in area or size. Here, the front electrodes of these unit elements 13a through 13h and 14a through 14h are connected in common to the ground potential. Thus, they can be connected without any electrical insulation. However, the back electrodes 15 of these elements are separately connected to the respective driving circuits so as to receive signal voltages of 2 to 4 kV. When the individual unit elements are operated separately by the respective driving circuits, potential differences occur between the adjacent elements because of the signals being out of phase. To prevent a short circuit between these potential differences, portions 16 with no electrode are provided between the respective adjacent elements. The non-electrode portions 16 are about 1 mm or more in width as shown in FIGURE 2 . These unit elements are electrically insulated. However, they are constructed in close contact. Thus, the applicator in this embodiment can achieve stable construction. This ultrasonic medical treatment applicator is constituted by a plurality of unit elements of shapes of two kinds as described above. The applicator has gaps of minimum size between the respective adjacent unit elements. Therefore, the space factor thereof can be enhanced. Moreover, these unit elements are identical in area. Thus, the driving circuits of identical specifications can be used. As a result, the entire apparatus can be simplified in configuration. Moreover, according to the present invention, there is provided an ultrasonic medical treatment applicator having a spherical ultrasonic element constituted by a plurality of unit elements for generating ultrasonic energy, wherein the unit elements are detachably fixed to a base plate by the use of screws. FIGURE 3 is a cross-sectional view taken along line A-A of FIGURE 1 . In FIGURE 3 , the front surfaces of base plates 31 and 32 are partial portions of spherical face. A hole 12 is provided at the center of the spherical face. An imaging ultrasonic probe (not shown) is inserted into the hole 12 . The base plates 31 , 32 , and other surrounding base plates (not shown, but eight pieces as a whole) respectively adhere to corresponding pairs of unit elements 13a and 14a , 13b and 14b , 13c and 14c , 13d and 14d , 13e and 14e , 13f and 14f , 13g and 14g , and 13h and 14h of FIGURE 1 . In FIGURE 3 , the base plates 31 and 32 are respectively secured by screws 34 , 35 , 36 and 37 to a supporting disk 33 . Thus, these eight base plates 31 , 32 and others can be independently removed from the supporting disk 33 by loosening the screws 34 through 37 , as required. Gaps 38 through 41 are provided between the base plates 31 and 32 and the unit elements 13b , 14b , 13f and 14f , respectively. Signal-lead passing bores 42 through 45 are provided piercing through the supporting disk 33 and the base plates 31 and 32 , and reaching the gaps 38 through 41 . Terminals 46 through 49 are provided at the periphery of the supporting disc 33 through L-shaped members 50 and 51 . The signal electrodes 15 (shown in FIGURE 2 ) provided on the back sides of the unit elements 13b , 14b , 13f and 14f are respectively connected to the terminals 46 through 49 by signal leads 53 through 56 by way of signal-lead passing bores 42 through 45 . Ground-lead passing bores 57 and 58 are provided outside of the signal-lead passing bores 42 through 45 . The unit elements 13b , 14b , 13f and 14f are connected by ground potential jumpers 10 on the front sides thereof. Further, the front sides of the unit elements 13b , 14b , 13f and 14f are connected to the outer portions of the terminals 46 through 49 by ground-leads 59 and 60 by way of the ground-lead passing bores 57 and 58 . The above-described construction has the following advantages. Namely, in the case where a unit element becomes defective and unable to perform necessary operations, the defective unit element can be readily removed by loosening screws so as to be repaired or replaced. As described above, in this embodiment, the use of screws allows the unit elements to be removed. Thus, the repair or replacement of the unit elements can be readily performed. As a result, the ultrasonic medical treatment applicator in this embodiment can always maintain the ultrasonic energy at a required maximum amount. Moreover, the conventional unit elements are fixed to the base plate by use of an adhesive. The fixing process of the unit elements should be performed in a state where all the focuses of the unit elements accurately coincide with each other. This requires cumbersome and complicated procedures in manufacturing. To the contrary, in this embodiment, first, the unit elements can be coarsely attached to the base plate by use of screws. Thereafter, the fine adjustment of focusing of the unit elements can be performed by use of screws. This can significantly reduce the above-mentioned cumbersome and complicated procedures in manufacturing. In addition, when adhesive is used instead of screws, the positions of unit elements are in danger of shifting while the adhesive is hardening. However, this problem can also be eliminated. The number of pairs of unit elements is not limited to eight, but a greater or smaller number of pairs may be used. However, the number of unit elements are determined taking into consideration such factors as the processing techniques of manufacturing materials, the probability of damage, and the cost necessary for repairs or replacement. In the first and second embodiments, the unit elements are secured by screws to the base plate. However, instead of screwing, any other manner may be employed so long as the unit elements are readily detachable. For example, the unit elements and the base plate may be sandwiched by use of securing parts. Otherwise, they may be attracted to each other by use of magnetic force. Whatever construction is used, advantages equal to those of the present invention can be obtained so long as the fine adjustment of positions of unit elements can be performed. In addition, the shape of the applicator is not limited to a circle. Also, the appearance of the unit elements is not limited to a fan-shape, a circle, or a polygon. Specifically, any unit elements of different appearances may be selectively utilized. Moreover, according to the present invention, it is desirable that the areas of the unit elements be identical. However, the embodiment of the present invention can be practiced by use of unit elements having areas substantially identical. Furthermore, in the previous description, the embodiment has been described as to an apparatus for destroying calculuses in a human body. However, the present invention may be applied to other apparatus such as an ultrasonic hyperthermia.

Claims: An ultrasonic medical treatment apparatus comprising: an ultrasonic transducer assembly (11) for emitting ultrasonic energy, wherein said transducer includes a plurality of unit transducer elements (13, 14) of two or more different shapes, but all having surface areas which are substantially equal, and wherein each said unit element is individually detachable. Ultrasonic apparatus according to claim 1, wherein said unit elements are radially and concentrically spaced around a focus of said transducer assembly. Ultrasonic apparatus according to claim 2 in which all of said elements are fan-shaped and are arranged in at least two concentric rings (13a, 13b, 14a, 14b) the elements in each ring having a different ratio of radial depth to circumferential length to those of the or each other ring. Ultrasonic apparatus according to any preceding claim, wherein each unit element includes a ground potential electrode on one side thereof, and a signal electrode (15) on the other side thereof. Ultrasonic apparatus according to claim 4, wherein said signal electrode of each said unit element has a surface area smaller than the surface area of the ground electrode side. Ultrasonic apparatus according to claim 5, wherein each said signal electrode is spaced at least 1mm from the outer periphery of said unit element. Ultrasonic apparatus according to claim 1, including means (33) for supporting said plurality of unit elements to form a partially spherically shaped face. Ultrasonic medical treatment apparatus according to any preceding claim and further comprising: a support member (33); a plurality of base plates (31, 32) removably attached to said support member, each of the unit transducer elements (13, 14) being attached to one of the base plates; and each unit transducer element (13, 14) being a piezoelectric element. The apparatus of claim 8, wherein each of said plural unit elements includes a partially spherically shaped surface. Ultrasonic medical treatment apparatus according to claim 1 and comprising: a support plate having a hole (12) at the center thereof for inserting an ultrasonic probe; a plurality of base plates (32, 22) removably attached to said support plate, said base plates having fan-shaped surfaces substantially equal in area to each other; a plurality of pairs of fan-shaped unit transducer elements (13, 14) having opposite sides, and attached to the fan-shaped surfaces of said respective base plates, the elements of each pair having said substantially equal surface areas and said different shapes from each other; a ground potential electrode provided on one side of each said unit element, and a plurality of signal electrode provided on the other side of each said unit element. The apparatus of claim 8, further comprising plural electrode-lead passing bores (42, 43, 44, 45) passing through said support plate and said plural base plates attached thereto, and reaching the other sides of said respective unit elements.

Inventors: AIDA SATOSHI, ISHIGURO AKIHIRO, IWAMA NOBUYUKI, SUZUKI SYUZI, AIDA, SATOSHI, ISHIGURO, AKIHIRO, IWAMA, NOBUYUKI, SUZUKI, SYUZI, AIDA, SATOSHI C/O PATENT DIVISION, ISHIGURO, AKIHIRO C/O PATENT DIVISION, IWAMA, NOBUYUKI C/O PATENT DIVISION, SUZUKI, SYUZI C/O PATENT DIVISION
Applicants: TOSHIBA KK, KABUSHIKI KAISHA TOSHIBA
Application year: 1988
Main classification: A61B17
IPC codes: B06B1