Patent Publication Number: US-2022218308-A1

Title: Ultrasonic transducer

Description:
TECHNICAL FIELD 
     The present disclosure in some embodiments relates to an ultrasonic transducer. 
     BACKGROUND 
     The statements in this section merely provide background information related to the present disclosure and do not necessarily constitute prior art. 
     Extracorporeal shockwave therapy (ESWT) is a method of treating an affected area by irradiating therapeutic ultrasonic waves on an object to be examined. 
     Commonly-used ESWT apparatuses include an ultrasonic transducer and use a method of irradiating therapeutic ultrasonic waves from the ultrasonic transducer to an affected area. 
     In general, an ultrasonic transducer includes piezoelectric elements for irradiating therapeutic ultrasonic waves on the object. 
     At this time, for the treatment of the object, the ultrasonic transducer needs to have the piezoelectric elements in an arrangement that can effectively deliver the therapeutic ultrasound irradiation to the affected area. 
     In addition, to properly arrange the piezoelectric elements in a typical ultrasonic transducer so that the therapeutic ultrasonic waves can be efficiently delivered to the affected area of the object, the ceramic material for the piezoelectric elements needs to be processed into an appropriate shape. 
       FIGS. 1A and 1B  are front views of the configuration of a conventional ultrasonic transducer  1 , including a ring-annular array. 
     As shown in  FIG. 1 , the ultrasonic transducer  1  has a piezoelectric multi-element array  10  including a plurality of piezoelectric elements  11  arranged in the form of ring-annular arrays and has an imaging probe  20 . Whereas, it should be noted that  FIG. 1B  shows the ultrasonic transducer  1  with the imaging probe  20  omitted for convenience of description. 
     The piezoelectric elements  11  irradiate the therapeutic ultrasonic waves toward the affected area of the object. 
     The plurality of piezoelectric elements  11  are configured in circumferential shapes, that is, ring shapes, each having a different diameter, as shown in  FIG. 1B . 
     Here, the therapeutic ultrasonic wave irradiated from each of the piezoelectric elements  11  may be irradiated intensively to the affected area of the object by arranging a separate acoustic lens (not shown). 
     Alternatively, adjustment of the amplitude or phase of the driving signal inputted to a separate piezoelectric element  11  can intensively irradiate the therapeutic ultrasonic wave to the affected area of the object. 
     On the other hand, if the innermost ring-shaped piezoelectric element  11  of the plurality of piezoelectric elements  11  has an inner diameter of R 1-in  and an outer diameter of R 1-out , then the second, larger diameter ring-shaped piezoelectric element  11  needs to be designed to have an inner diameter of R 2-in  which is equal to or slightly larger than R 1-out . 
     Similarly, the third, larger diameter ring-shaped piezoelectric element  11  needs to be designed to have an inner diameter of R 3-in  which is equal to or slightly larger than R 2-out . 
     Such an arrangement of the piezoelectric elements  11  in differently sized ring shapes as described above is to cause therapeutic ultrasonic waves emitted from the piezoelectric elements  11  to be effectively focused on the affected area of the object. 
     At this time, the piezoelectric elements  11  are manufactured by processing ceramic materials such as barium titanate (BaTiO 3 ), lead titanate (PbTiO 3 ), and lead zirconate system (PbZrO 3 ) by using a microelectromechanical systems (MEMS) technology. 
     In addition, there is a need for a process of attaching the piezoelectric elements  11  each having a differently sized ring shape on the substrate through a thermal pressing method or an ultrasonic bonding. 
     To manufacture the piezoelectric elements  11  made of ceramic materials to have different sizes in this way requires a special manufacturing facility capable of manufacturing respectively different diameters of ring-shaped piezoelectric elements  11  to go through a complicated manufacturing process. 
     Therefore, the ring-annular array type ultrasonic transducer  1  consumes a lot of effort to manufacture and increases the processing cost. 
     On the other hand, with a matrix array or a circular array type ultrasonic transducer other than the ring-annular array type shown in  FIG. 1 , there are difficulties in a manufacturing process similar to that described above. 
     Accordingly, there is a need to provide a proper arrangement of piezoelectric element arrays, which is easy to manufacture and has an appropriate therapeutic effect in the treatment of the subject. 
     SUMMARY 
     Technical Problem 
     Therefore, the present disclosure seeks to provide an ultrasonic transducer having a simple configuration while having an excellent therapeutic effect due to the effective focusing of therapeutic ultrasonic waves on a target region. 
     Further, the present disclosure aims to provide an ultrasonic transducer that saves time and cost for processing or manufacturing. 
     Technical Solution 
     According to some embodiments of the present disclosure, an ultrasonic transducer is provided, including a housing, a base disposed on a front surface of the housing, and multiple linear arrays each arranged in a radial direction on the base, extending from a central region of the base, and configured to irradiate a therapeutic ultrasonic wave, the linear arrays each comprising a plurality of piezoelectric elements which are linear elements extending side by side with each other in the radial direction. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIGS. 1A and 1B  are front views of the configuration of a conventional ultrasonic transducer, including a ring-annular array. 
         FIG. 2  is a side view of the configuration of an ultrasonic transducer according to at least one embodiment of the present disclosure. 
         FIG. 3  is a front view of the configuration of a first aspect of the ultrasonic transducer according to at least one embodiment of the present disclosure. 
         FIG. 4  is a front view of the configuration of a second aspect of the ultrasonic transducer according to at least one embodiment of the present disclosure. 
         FIG. 5  shows the configuration of piezoelectric elements that constitute a component of the ultrasonic transducer according to at least one embodiment of the present disclosure. 
         FIGS. 6A and 6B  show the configuration of an ultrasonic transducer according to another embodiment of the present disclosure. 
         FIGS. 7A to 7E  show the performance test results of the ultrasonic transducer according to at least one embodiment of the present disclosure. 
         FIGS. 8A to 8E  show the performance test results of a conventional ultrasonic transducer composed of ring-annular arrays. 
         FIG. 9  is a partial perspective view of an ultrasonic transducer according to yet another embodiment of the present disclosure. 
         FIG. 10  is a partial perspective view of the ultrasonic transducer of another embodiment of the present disclosure shown in  FIGS. 6A and 6B  for comparison with the embodiment of  FIG. 9 . 
         FIG. 11A  shows a curvature profile of a linear array  930  as partially cut in a transverse direction D T  according to the yet another embodiment of the present disclosure. 
         FIG. 11B  shows a curvature profile of a linear array  630  of another embodiment shown in  FIG. 10  as cut in transverse direction D T . 
         FIG. 12A  is a measurement of the intensity of therapeutic ultrasonic waves in a subject when a focus is formed on a focus position at a reference focal length distanced from the ultrasound transducer according to the embodiment of  FIG. 9 . 
         FIG. 12B  is a measurement of the intensity of the therapeutic ultrasonic waves from the ultrasound transducer according to another embodiment of  FIG. 10 . 
     
    
    
     DETAILED DESCRIPTION 
     Hereinafter, at least one embodiment of the present disclosure will be described in detail with reference to the accompanying drawings. In the following description, like reference numerals would rather designate like elements although the elements are shown in different drawings. Further, in the following description of the at least one embodiment, a detailed description of known functions and configurations incorporated herein will be omitted for the purpose of clarity and for brevity. 
     Additionally, various terms such as first, second, i), ii), (a), (b), etc., are used solely to differentiate one component from the other but not to imply or suggest the substances, order, or sequence of the components. Throughout this specification, when a part “includes” or “comprises” a component, the part is meant to further include other components, not excluding thereof unless there is a particular description contrary thereto. 
       FIG. 2  is a side view of the configuration of an ultrasonic transducer  100  according to at least one embodiment of the present disclosure. 
     As shown in  FIG. 2 , the ultrasonic transducer  100  according to at least one embodiment of the present disclosure includes a housing  110 , a base  120 , one or more linear arrays  130 , an imaging probe  140 , an acoustic lens  150 , and a gel pad  160 . 
     The housing  110  provides a space for placement of the base  120 , the linear arrays  130 , the imaging probe  140 , and others. 
     Of the housing  110 , an area in which the base  120 , the linear arrays  130 , and the imaging probe  140  are placed may be referred to as a front portion which may then be peripherally bent forward into an L or “¬” shape so that the front portion of the housing  110  has a space for the base  120 . 
     In addition, the front portion of the housing  110  may be formed in an exemplary cylindrical or polygonal column shape. Disposed on the front portion of the housing  110  is the base  120  having an upper surface, on which the linear arrays  130  are disposed. 
     In addition, disposed on the housing  110  centrally and forwardly thereof is the imaging probe  140 . 
     On the other hand, the housing  110  shown in  FIG. 2  is configured to have an outer diameter D 3  of 110 mm. 
     In addition, each linear array  130  extends to a position spaced 5 mm from the outermost of the housing  110 , and two diagonally opposite linear arrays  130  have their distal ends separated by a distance D 2  of 100 mm. 
     The base  120  provides a space for the linear arrays  130  to be disposed. The linear array  130  are disposed on the front surface of the base  120  which may serve as a backing panel supporting the linear arrays  130 . 
     As shown in  FIG. 3 , the base  120  may be formed in an octagonal shape as shown in  FIG. 3 , which is only exemplary and may have other shapes, such as a circular shape. 
     Disposed centrally of the base  120  is the imaging probe  140 , and the linear arrays  130  are disposed circumferentially of a region in which the imaging probe  140  is disposed. In the ultrasonic transducer  100  shown in  FIG. 2 , the region in which the imaging probe  140  is disposed is designed to have a width D 1  of about 42 mm. 
     The linear array  130  has its piezoelectric elements that generate vibrations which in turn generate therapeutic ultrasonic waves that are irradiated toward the object. 
     The linear array  130  refers to a linear array type in which rectilinear piezoelectric elements having similar lengths and widths are arranged side by side and adjacent to each other. The linear array  130  includes long sides formed to be relatively elongated along the longitudinal direction thereof, and short sides formed to be relatively short along the latitudinal or widthwise direction thereof. 
     Multiples of the linear array  130  are arranged over the front surface of the base  120 . The multiple linear arrays  130  are disposed adjacent to the central region of the front surface of the base  120 , and the linear arrays  130  are radially disposed around the central region of the front surface of the base  120 . 
     Specifically, a radial direction of the base  120  may refer to an arbitrary direction from the center point of the front surface of the base  120  toward the outer edge of the front surface of the base  120 , wherein the linear array  130  is arranged so that its longitudinal axis lies on the radial direction of the base  120 . 
     At this time, the long sides of the linear array  130  are disposed in parallel to the radial direction of the base  120 , and the short sides of the linear array  130  are vertically disposed to the radial direction of the base  120 . 
     On the other hand, each linear array  130  is composed of a plurality of piezoelectric elements, and due to such a configuration, the ultrasonic transducer  100  according to at least one embodiment of the present disclosure may be made advantageously through a simple manufacturing process and uncomplicated facilities for manufacturing as will be described in detail below. 
     The imaging probe  140  serves to generate information about the ultrasound image of the object and to transfer the same information to an unshown display unit. Although not shown, the imaging probe  140  includes an imaging ultrasound transmitter and an imaging ultrasound receiver. 
     The imaging ultrasound transmitter irradiates imaging ultrasonic waves toward an object. The imaging ultrasound receiver receives an echo signal of the imaging ultrasonic waves reflected by the object. 
     The echo signal received by the imaging ultrasound receiver is converted into an image signal by an unshown signal processing unit, and the image signal is transmitted to the display unit for outputting the ultrasonic image of the object. 
     The acoustic lens  150  concentrates therapeutic ultrasonic waves into a target region. 
     The acoustic lens  150  is disposed forwardly of the base  120  and the plurality of linear arrays  130 , and the therapeutic ultrasound component irradiated from the linear arrays  130  passes through the acoustic lens  150  to be focused on one area of the object. 
     The acoustic lens  150  provided as described above can efficiently focus the therapeutic ultrasonic waves, resulting in an enhanced curative effect. 
     On the other hand, at least one embodiment of the present disclosure illustrates the configuration having the acoustic lens  150  for focusing the therapeutic ultrasonic waves, although the one embodiment further includes a configuration for adjusting the focusing position of the therapeutic ultrasonic waves by using a beamforming technique. 
     In particular, the one embodiment of the present disclosure may still include a configuration in which the focusing position of the therapeutic ultrasonic waves is adjusted by adjusting the amplitude or phase of the driving signal inputted to the piezoelectric elements of the linear array  130 . In this case, the acoustic lens  150  is not necessarily provided for concentrating therapeutic ultrasonic waves. 
     On the other hand, since each therapeutic ultrasonic wave needs to be focused on a set focal region P 1 , the acoustic lens  150  may be configured so that the degree of refraction of each therapeutic ultrasound component is different. 
     Meanwhile, the acoustic lens  150  may have a curvature R 1  of, for example, 90 mmR, although and the acoustic lens  150  may be designed to have a different, appropriate curvature. 
     The gel pad  160  is disposed on the front of the acoustic lens  150  to facilitate the delivery of the therapeutic ultrasonic waves. The therapeutic ultrasound waves irradiated from the linear array  130  are focused by the acoustic lens  150  and passes through the gel pad  160  to be irradiated through the object. 
     The gel pad  160  may be internally filled with fluid and may serve to reduce attenuation, scattering, and the like of therapeutic ultrasonic waves irradiated from the linear array  130 . 
     In addition, once filled with a fluid, the gel pad  160  may also serve to cool the heat generated by ultrasonic waves. 
     The thickness of the gel pad  160  from the base  120  may be about 30 mm, although the thickness thereof may be designed differently. 
     In addition, the ultrasonic transducer  100  according to at least one embodiment of the present disclosure may include unshown signal transmission/reception lines inside the housing  110  or in an unshown controller. 
     In addition, the ultrasonic transducer  100  according to at least one embodiment of the present disclosure may include features such as an unshown power button and an operation input button capable of controlling its operation, and it may be linked to a separate control device. However, those features are not to be focused on in the configuration of the present disclosure, and a detailed description thereof will be omitted. 
       FIG. 3  is a front view of the configuration of a first aspect of the ultrasonic transducer  100  according to at least one embodiment of the present disclosure. 
     As showing in  FIG. 3 , the first aspect of the ultrasonic transducer  100  according to at least one embodiment of the present disclosure is configured to include four linear arrays  130  arranged on the base  120  along the radial direction of the base  120 . 
     The ultrasonic transducer  100  according to at least one embodiment of the present disclosure has a distinctive type in which multiple uniformly rectilinear piezoelectric elements are arranged adjacent to each other into a linear array type. Accordingly, each linear array  130  has a rectangular shape. 
     The at least one embodiment of the present disclosure illustrates a case where the linear array  130  has an aspect ratio of short side to long side of about 16 mm to 34 mm. The at least one embodiment may be modified to have other aspect ratios of the linear array  130 . 
     At this time, in consideration of the treatment efficiency by the degree of focusing the therapeutic ultrasonic waves when the ultrasonic transducer  100  is operated and of the arrangement and shape of the base  120  and other components, the aspect ratio of short side to long side is preferably 1:2 to 1:4 or less. 
     The linear arrays  130  constituting the first aspect of ultrasonic transducer  100  are disposed interspaced from one another at a predetermined angle, respectively. At this time, the angle at which each linear array  130  is spaced from the adjacent one may be about 90 degrees. 
     Accordingly, the linear arrays  130  are disposed to have a length in the upper, lower, left and right directions surrounding the center of the base  120 , respectively, and the respective linear arrays  130  are formed to have the same shape. 
     Therefore, the respective linear arrays  130  have a point-symmetrical arrangement relative to the center of the base  120 . 
     The respective linear arrays  130  may be fabricated to have a uniform shape and size. Therefore, in manufacturing the ultrasonic transducer  100 , there is no need for a manufacturing facility or the like for separately manufacturing each array or each piezoelectric element. 
     Accordingly, the ultrasonic transducer  100  according to at least one embodiment of the present disclosure takes a simple process of manufacturing the respective linear arrays  130  as will be detailed below, and it obviates the need for such a complicated process and a manufacturing facility as in the comparative example described above to manufacture the linear arrays  130 . 
     On the other hand, the present applicant was able to confirm that the first aspect of the ultrasonic transducer  100  according to the at least one embodiment has a significant efficiency in terms of its therapeutic effect when compared to the aforementioned comparative example. 
     Further, despite allocating a narrower area to its linear arrays  130  than the annular array type ultrasonic transducer  1  does, the ultrasonic transducer  100  according to the at least one embodiment was confirmed to have the curative effect similar to that of the annular array type ultrasonic transducer  1 . 
     This provides an advantage that the ultrasonic transducer  100  according to the at least one embodiment can be manufactured more simply, consuming less material than the comparative example as well as perform an effective treatment on a subject. 
       FIG. 4  is a front view of the configuration of a second aspect of the ultrasonic transducer  100  according to at least one embodiment of the present disclosure. 
     The second aspect of the at least one embodiment of the present disclosure, as in the case of the first aspect, a plurality of line-type linear arrays  130  are disposed on the base  120 . Specifically, the linear arrays  130  are disposed adjacent to the central region of the base  120  so that the linear arrays  130  have their longitudinal axes extend in the radial direction of the base  120 . 
     However, different from the first aspect, the second aspect has the linear arrays  130  spaced apart from each other by 45 degrees. Therefore, in contrast to the first aspect wherein a high-intensity focused ultrasound (HIFU) transducer unit is composed of a total of four linear arrays  130 , the second aspect provides a HIFU transducer unit composed of a total of eight linear arrays  130 . 
     In this way, the second aspect doubles the number of linear arrays  130  of the first aspect to minimize the difference in the area occupied by the linear arrays  130  on the base  120  when compared with the annular array type transducer. 
     This can increase the area of the irradiation source for irradiating the therapeutic ultrasonic waves, thereby increasing the ultrasound focusing and curative effect to a level almost the same as the annular array type transducer. 
       FIG. 5  shows the configuration of piezoelectric elements that constitute a component of the ultrasonic transducer  100  according to at least one embodiment of the present disclosure. 
     As shown in  FIG. 5 , the at least one embodiment of the present disclosure has the linear array  130  made of a plurality of piezoelectric elements. 
     At this time, the piezoelectric elements may be manufactured using a piezoelectric material such as lead zirconate titanate (PZT), polyvinylidene fluoride (PVDF), lead magnesium niobate (PMN), and they may be electrically connected to an unshown printed circuit board wherein the driving signal establishes the piezoelectric effect for generating therapeutic ultrasonic waves. 
     At this time, the plurality of piezoelectric elements are each made in a linear form, and each piezoelectric element may have the same shape and size. 
     Therefore, during the manufacture of the linear array  130  in the at least one embodiment, the multiple piezoelectric elements may be designed to undergo the same fabrication process. 
     During manufacture, different from the annular array type transducer which involves fabricating and placing individual devices having different diameters, the linear array  130  in the at least one embodiment obviates the need for complicated manufacturing equipment and manufacturing processes. 
       FIGS. 6A and 6B  show the configuration of an ultrasonic transducer  600  according to another embodiment of the present disclosure. 
     Specifically,  FIG. 6A  is a front view of the ultrasonic transducer  600  according to another embodiment of the present disclosure, and  FIG. 6B  is a side view of the ultrasonic transducer  600  according to the another embodiment. 
     The ultrasonic transducer  600  according to the another embodiment includes the configuration of the ultrasonic transducer  100  according to the at least one embodiment as long as they are not contrary to each other. 
     However, different from the ultrasonic transducer  100  according to the at least one embodiment, the ultrasonic transducer  600  according to the another embodiment has linear arrays  630  disposed on a curved surface. 
     As shown in  FIGS. 6A and 6B , the ultrasonic transducer  600  according to the another embodiment has a base  620  which is formed to have predetermined parabolic curved portions over the outer region except for the central region thereof, to face the area irradiated with therapeutic ultrasonic waves. 
     At this time, the central region of the base  620  may be formed to be constant in, for example, its thickness and may be provided with an imaging probe  640 . Meanwhile, in the another embodiment, the central portion of the base  620  has a height H 1  of about 12.4 mm. 
     The front portion of the base  620  needs to be curved toward the area to be irradiated with therapeutic ultrasonic waves, for which the thickness of the base  620  gradually increases as it deviates from the central region of the base  620 . For example, the base  620  has a height H 2  of about 30 mm at the outermost portion thereof. 
     At this time, the curvature of the front portion of the base  620  may be determined by roughly considering the distance from the base  620  to the focal position P 2  of the therapeutic ultrasonic waves, and illustratively, the front portion of the base  620  has a curvature R 2  of 90 mmR. 
     In addition, conforming to such curved configuration of the front portion of the base  620 , the respective piezoelectric elements lie flush with the same curvature surface of the base  620 . Accordingly, the respective linear arrays  630  are formed on the same curvature surface. 
     This can increase the efficiency of focusing the therapeutic ultrasonic waves irradiated from the respective piezoelectric elements into the single area of the object. 
     As described above, the another embodiment of the present disclosure, which has the respective piezoelectric elements formed on the curvature surface, can have a high focusing effect of therapeutic ultrasonic waves even without the acoustic lens  150  (see  FIG. 2 ) unlike the ultrasonic transducer  100  according to the at least one embodiment. 
     Accordingly, the ultrasonic transducer  600  according to the another embodiment can be manufactured save the process of manufacturing and attaching the acoustic lens  150  (see  FIG. 2 ), thus simplifying the manufacturing process and manufacturing equipment to save the manufacturing cost. 
       FIGS. 7A to 7E  show the performance test results of the ultrasonic transducer  100  according to at least one embodiment of the present disclosure. 
     At this time, the ultrasonic transducer  100  was tested using a configuration in which eight linear arrays  130  are disposed on the base, and detailed specifications of the ultrasonic transducer  100  are as described above. 
     Here,  FIG. 7A  is a measurement of the intensity of a therapeutic ultrasonic wave on a subject when a focus is formed on a focus position at a reference focal length distanced from the ultrasound transducer  100  according to the at least one embodiment. Meanwhile, for convenience of description, the focal length at this time is set to 0 mm. 
     In addition, the z-axis direction signifies the depth direction of the object, and the x-axis and y-axis directions signify the horizontal axis direction and the vertical axis direction perpendicular to the horizontal axis direction respectively at the same depth in the object. 
     On the other hand, the test was conducted by providing the therapeutic ultrasonic wave with a frequency of 1.5 MHz, and the dynamic range (DR) was set to be 60 dB. These settings apply to all of the following processes. 
     In addition, depending on the intensity of the therapeutic ultrasonic wave in the subject, the region with the strongest therapeutic ultrasonic wave was arranged to be displayed in red, and the region that has the weakest therapeutic ultrasonic wave was displayed in blue. 
     First, the lower-left graph of  FIG. 7A  shows the intensity of therapeutic ultrasonic wave dependent on depth at the point where the x-axis coordinate is 0, that is, the point where the strongest focused intensity is on the x-y plane. At this time, the amplitude of the therapeutic ultrasonic wave is the largest at a point having a depth of about 30 mm from the surface of the object, and thus the therapeutic ultrasonic wave exhibits the greatest intensity at this point. 
     The upper left graph of  FIG. 7A  shows the intensity of therapeutic ultrasonic waves according to a change in position in the x-axis direction at a depth of 29.80 mm in the object. At this time, it can be seen that where the x-axis coordinate is 0, the intensity of the therapeutic ultrasonic wave is the largest, and the intensity thereof is symmetrically decreased as it is further away from the x-axis coordinate 0. 
     In addition, as shown in the right graph of  FIG. 7A , graphs are formed radially around a point having a depth of about 30 mm in the object. Since the focusing point of the therapeutic ultrasonic waves is located at a point not deep in the object, it can be seen that the therapeutic ultrasonic waves are effectively focused at that point. 
       FIGS. 7B, 7C, 7D, and 7E  respectively show the intensities of a therapeutic ultrasonic wave at a position in the object when the focal position is 20 mm, 40 mm, 60 mm, and 80 mm from the reference focus. 
     Different focal positions of the therapeutic ultrasonic waves from that of  FIG. 7A  establish different positions in which the therapeutic ultrasonic waves are most strongly focused. In particular,  FIGS. 7B, 7C, 7D, and 7E  exhibit that the strongest therapeutic ultrasonic waves are focused at depths of 49.60 mm, 69.40 mm, 89.80 mm, and 109.60 mm in the object, respectively. 
     In  FIGS. 7B to 7E , the therapeutic ultrasound waves are focused in radial forms similar to the case of  FIG. 7A . However, the radial focus intensity decreases from  FIG. 7A  to  FIG. 7E  because the transfer efficiency of therapeutic ultrasonic waves gradually decreases toward the deeper position of the subject. 
       FIGS. 8A to 8E  show the performance test results of the conventional ultrasonic transducer  1  composed of ring-annular arrays. 
     Specifically,  FIGS. 8A, 8B, 8C, 8D, and 8E  show the ultrasound intensities in the object positions when the focal positions of the therapeutic ultrasound waves are 0 mm, 20 mm, 40 mm, 60 mm, and 80 mm, respectively. 
     The performance test was performed using the typical transducer  1 , as shown in  FIG. 1 . The transducer  1  has the ring-annular array  10  composed of a total of twenty-four ring-annular arrays of the piezoelectric elements  11  each having a thickness of 1.2 mm. 
     A comparison between  FIG. 7  and  FIG. 8  reveals that the performance graphs of the ultrasonic transducer  100  according to the at least one embodiment shown in  FIG. 7  are quite similar in shape to those of the ring-annular array type ultrasonic transducer shown in  FIG. 8 . 
     In other words,  FIGS. 7A and 8A ,  FIGS. 7B and 8B ,  FIGS. 7C and 8C ,  FIGS. 7D and 8D , and  FIGS. 7E and 8E  are very similar to each other in shape, and they show no significant difference in the strength of the therapeutic ultrasonic waves in the focused area. 
     This signifies that for the smaller footprint of the linear transducer arrays  130  of the ultrasonic transducer  100  than that of the ring-annular arrays of the ultrasonic transducer  1 , the ultrasonic transducer  100  yet provides the focus intensity and strength of the therapeutic ultrasonic waves as good as that of the ultrasound transducer  1  shown in  FIG. 1 . 
     Therefore, it can be seen that the ultrasonic transducer  100  of the present disclosure has a superior curative effect while being simple to manufacture compared to the prior art transducer  1 . 
       FIG. 9  is a partial perspective view of an ultrasonic transducer according to yet another embodiment of the present disclosure. 
       FIG. 10  is a partial perspective view of the ultrasonic transducer of the another embodiment of the present disclosure shown in  FIGS. 6A and 6B  for comparison with the yet another embodiment of  FIG. 9 . 
     The following will concentrate on differences between the yet another embodiment shown in  FIG. 9  and the aforementioned embodiment in  FIGS. 6A and 6B , and repeated description will be omitted. 
     As shown in  FIGS. 9 and 10 , the yet another embodiment in  FIG. 9  provides an ultrasonic transducer having a linear array  930  with a distinctive curvature that is bi-directional, i.e., in the longitudinal direction and transverse direction D T , as compared to the another embodiment illustrated in  FIG. 10 . 
     Accordingly, in the yet another embodiment of  FIG. 9 , the ultrasonic transducer has a base  920  that is at least partially curved in cross section in both the longitudinal and transverse directions, conforming to the curved surface defined by the linear array  930 . 
     Referring to  FIGS. 11A and 11B  for comparing profiles formed in transverse direction D T ,  FIG. 11A  illustrates a curvature profile of the linear array  930  as partially cut in transverse direction D T  according to the yet another embodiment of the present disclosure, and  FIG. 11B  shows a curvature profile of the linear array  630  of the another embodiment shown in  FIG. 10  as cut in transverse direction D T . 
     As shown, the linear array  930  illustrated in  FIG. 11A  has a curvature in which a height varies in the transverse direction, while the linear array  630  illustrated in  FIG. 11B  forms a plane without a height difference in the transverse direction. 
     Referring back to  FIGS. 9 and 10 , the linear array  930  of  FIG. 9  and the linear array  630  of  FIG. 10  have different ultrasound collecting performances due to their difference in the curvature formed along transverse direction D T . 
     For example, as illustrated in  FIG. 9 , the linear array  930  may be interpreted as irradiating ultrasonic waves to be concentrated at an ultrasound collection surface CA 1  distanced from the linear array  930  by an arbitrary radius R 3 . 
     In addition, as illustrated in  FIG. 10 , the linear array  630  may be interpreted as irradiating ultrasonic waves to be concentrated at an ultrasound collection surface CA 2  distanced from the linear array  630  by the same radius R 3  as illustrated in  FIG. 9 . 
     At this time, ultrasound collection surface CA 1  of  FIG. 9  may be smaller than ultrasound collection surface CA 2  of  FIG. 10  by approximately 20% in the illustrated embodiments. This means that assuming that the distance to the patient&#39;s affected area is determined as R 3 , an ultrasound pressure of 20% can be further increased by a transducer of the same size. 
     In particular,  FIG. 12A  is a measurement of the intensity of therapeutic ultrasonic waves in a subject with a focus formed on a focus position at a reference focal length distanced from the ultrasound transducer according to the yet another embodiment of  FIG. 9 , and  FIG. 12B  is a measurement of the intensity of therapeutic ultrasonic waves from the ultrasound transducer according to the another embodiment of  FIG. 10 . 
     As shown in  FIG. 12B , the other embodiment of  FIG. 10  shows an aspect in which the intensity of the vertical beamfield gradually increases as the focal length approaches 0 mm. In contrast, as illustrated in  FIG. 12A , the yet another embodiment of  FIG. 9  shows a tendency that the intensity of the vertical beamfield is rapidly increased as the focal length approaches 0 mm, and thus the beam intensity is concentrated near the focal length of 0 mm. 
     As described above, since the ultrasonic transducers  100 ,  600  according to the respective embodiments of the present disclosure are manufactured by using the line-type linear arrays  130 ,  630 , they are manufactured through simplified manufacturing process by advantageously utilizing simplified manufacturing equipment, as compared to using other types of arrays. 
     In addition, the ultrasonic transducers  100 ,  600  according to the respective embodiments of the present disclosure have the above manufacturing advantages and yet have excellent therapeutic effects as with the prior art ultrasonic transducers. 
     Although exemplary embodiments of the present disclosure have been described for illustrative purposes, those skilled in the art will appreciate that various modifications, additions, and substitutions are possible, without departing from the idea and scope of the claimed invention. Therefore, exemplary embodiments of the present disclosure have been described for the sake of brevity and clarity. The scope of the technical idea of the present embodiments is not limited by the illustrations. Accordingly, one of ordinary skill would understand the scope of the claimed invention is not to be limited by the above explicitly described embodiments but by the claims and equivalents thereof. 
     
       
         
           
               
             
               
                   
               
               
                 REFERENCE SIGNS LIST 
               
               
                   
               
             
            
               
                   
               
            
           
           
               
               
               
            
               
                   
                 100: ultrasonic transducer 
                 110: housing 
               
               
                   
                 120: base 
                 130: linear array 
               
               
                   
                 140: imaging probe 
                 150: acoustic lens 
               
               
                   
                 160: gel pad