Abstract:
A treatment device comprising a cavity to receive body tissue, the cavity comprising a side wall, a closed end wall and an opening to admit tissue, and at least four ultrasonic transducers disposed to transmit ultrasound into the cavity.

Description:
RELATED APPLICATIONS 
       [0001]    This application is a continuation application of PCT Application Ser. No. PCT/IB2014/065113, filed Oct. 7, 2014, which claims priority to Great Britain Application Ser. No. 1317711.8, filed Oct. 7, 2013. 
     
    
     FIELD OF THE INVENTION 
       [0002]    This invention relates to a treatment device, particularly but not exclusively for the treatment of adipose tissue, a treatment apparatus and a method of operating the treatment device. 
       BACKGROUND OF THE INVENTION 
       [0003]    A known aesthetic body shaping technique is the use of ultrasound to treat fat tissue layers below the skin. A problem with known systems is that of directing or concentrating the ultrasonic energy to only affect or treat the desired volume of tissue, i.e. the fat cells, without affecting other regions of the skin. A related problem is that, for ultrasonic transducers, the power transmitted falls away with distance from the transducer. This can be addressed using high-intensity focussed ultrasound, but this is a relatively complex solution. An example of an alternative device is known from US2012/0277587 showing a treatment device which has a cavity into which skin surface tissue is drawn by applying a vacuum. The treatment device comprises two parallel ultrasonic transducers which direct energy into the tissue between them. To provide an effective treatment volume between a pair of transducers however, the power has to be raised sufficiently such that surrounding tissue may be affected and damaged. Circular transducers are also known to provide a strong focal point for the ultrasound but the focal point is relatively small and the transducers are expensive. 
       SUMMARY OF THE INVENTION 
       [0004]    According a first aspect of the invention there is provided a treatment device comprising a cavity to receive body tissue, the cavity comprising a side wall, a closed end wall and an opening to admit tissue, and at least four ultrasonic transducers disposed to transmit ultrasound into the cavity. 
         [0005]    The ultrasonic transducers may be disposed such that the beams generated by the transducers overlap to define a treatment volume within the cavity. 
         [0006]    The treatment volume may be spaced from the end wall. 
         [0007]    The plurality of ultrasonic transducers may comprise an opposed pair of ultrasonic transducers. 
         [0008]    The treatment device may comprise six ultrasonic transducers arranged in a hexagonal configuration. 
         [0009]    The treatment device may comprise three opposed pairs of ultrasonic transducers arranged in a regular hexagonal configuration. 
         [0010]    The side wall may comprise internal walls arranged in a hexagonal configuration and the ultrasonic transducers may be disposed within the internal walls. 
         [0011]    The treatment device according may comprise a plurality of radio frequency electrodes disposed around the cavity and disposed to transmit radio frequency energy into the cavity 
         [0012]    The radio frequency electrodes may be disposed in the side wall. 
         [0013]    The radio frequency electrodes may be disposed closer to the end wall than the ultrasonic transducers. 
         [0014]    The treatment device may comprise tissue engagement means to draw tissue into the cavity. 
         [0015]    The tissue engagement means may comprise a connection from the cavity for connection to a low-pressure source. 
         [0016]    An auxiliary ultrasonic transducer may be disposed in the end wall of the cavity. 
         [0017]    Additional treatment elements comprising light sources may be disposed in the end wall of the cavity. 
         [0018]    An auxiliary radiofrequency electrode may be disposed in an upper wall of the cavity. 
         [0019]    The treatment device may comprise a TENS electrode to provide pain relief. 
         [0020]    According to a second aspect of the invention there is provided a treatment apparatus comprising a treatment device according to any one of the preceding claims and a control apparatus to control the ultrasonic transducers and the radiofrequency electrode. 
         [0021]    According to a third aspect of the invention there is provided a method of operating a treatment device according to the first or second aspects of the invention, the method comprising receiving body tissue in the cavity and operating the ultrasonic transducers to transmit ultrasound into the cavity. 
         [0022]    The method may comprise operating the ultrasonic transducers with a frequency in the range 200 kHz to 4 MHz, preferably 1 MHz to 3 MHz and most preferably 1.5 to 2.5 MHz, 
         [0023]    The method may comprise operating the ultrasonic transducers for durations in the range 0.1 seconds to 20 minutes, preferably 0.5 to 10 minutes and most preferably 1 to 6 minutes. 
         [0024]    The method may comprise operating the ultrasonic transducers such that the energy transmitted into the tissue is in the range 50 to 700 J cm−3, preferably in the range 75 to 250 J cm−3 and most preferably 100 to 250 J cm−3. 
         [0025]    The method may comprise operating the transducers with duty cycle in the range 8 to 100%, preferably in the range 16.6 to 100% and most preferably in the range 33.33 to 100%. 
         [0026]    The method may comprise performing a cooling cycle between operation of the ultrasonic transducers. 
         [0027]    Where the treatment device comprises RF electrodes, the method may comprise operating the RF electrodes with a frequency in the range 100 to 4000 kHz, preferably 300 to 2000 kHz and most preferably 500 to 1000 kHz. 
         [0028]    The method may comprise operating the RF electrodes for durations in the range 10 to 5000 ms, preferably 30 to 2000 ms and most preferably 50 to 750 ms. 
         [0029]    The RF power may be in the range 5 to 100 W, preferably in the range 10 to 60 W and most preferably 20 to 40 W. 
         [0030]    The method may comprise operating the RF electrodes with a duty cycle in the range 8 to 100%, preferably in the range 16.6 to 100% and most preferably in the range 33.33 to 100%. 
         [0031]    Where the treatment device comprises a TENS electrode, the method may further comprise supplying an electrical signal to the TENS electrode. 
         [0032]    The method may comprise operating the ultrasonic transducers to generate a generally even energy distribution in body tissue in the cavity. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0033]    Embodiments of the present invention are described by way of example only with reference to the accompanying drawings, wherein; 
           [0034]      FIG. 1  is a perspective view of the underside of a treatment device embodying the present invention. 
           [0035]      FIG. 2  is a perspective view of the upper side of the device of  FIG. 1 . 
           [0036]      FIG. 3  is a plan view of the top of the device of  FIG. 1  and  FIG. 2 , 
           [0037]      FIG. 4  is a cross-section on line  4 - 4  of  FIG. 3 . 
           [0038]      FIG. 5 a    and  FIG. 5 b    are graphs showing the energy distribution of pairs of opposed ultrasonic transducers. 
           [0039]      FIG. 6  is a diagrammatic illustration of the ultrasonic beams generated by the device of  FIG. 1 . 
           [0040]      FIG. 7  is a diagrammatic illustration of the device of  FIG. 1  in a first mode of operation. 
           [0041]      FIG. 8  is a diagrammatic illustration of the device of  FIG. 1  in a second mode of operation. 
           [0042]      FIG. 9  is a graph showing temperatures of tissue layers during cooling and heating, and 
           [0043]      FIG. 10  is a perspective view similar to  FIG. 1  showing additional treatment elements. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0044]    With specific reference now to the drawings in detail, it is stressed that the particulars shown are by way of example and for purposes of illustrative discussion of the preferred embodiments of the present invention only, and are presented in the cause of providing what is believed to be the most useful and readily understood description of the principles and conceptual aspects of the invention. In this regard, no attempt is made to show structural details of the invention in more detail than is necessary for a fundamental understanding of the invention, the description taken with the drawings making apparent to those skilled in the art how the several forms of the invention may be embodied in practice. 
         [0045]    Before explaining at least one embodiment of the invention in detail, it is to be understood that the invention is not limited in its application to the details of construction and the arrangement of the components set forth in the following description or illustrated n the drawings. The invention is applicable to other embodiments or of being practiced or carried out in various ways. Also, it is to be understood that the phraseology and terminology employed herein is for the purpose of description and should not be regarded as limiting. 
         [0046]    Referring now to  FIG. 1  to  FIG. 4 , a treatment device embodied in the present invention is generally shown at  10 . The device comprises a generally toroidal upper element  11 , a generally circular lower element  12  and a contact part  13 . The upper element  11  and lower element  12  are joined by bolts  14  passing through apertures  15  in the upper element  11  and received in threaded bores  16  in the lower element  12 . The contact part  13  is connected to the lower element  12  by screws  17  passing through apertures in an annular outer flange  18  of the contact part  13 . 
         [0047]    The contact part  13  has a generally annular contact surface  20 , around the periphery of a cavity  21 . The cavity  21  comprises a closed cavity defined by an inwardly directly side wall  22  of the contact part  13  which extends perpendicularly or at an angle to the contact surface  20 . The closed end wall  23  of the cavity  21  is defined by a shaped surface of the lower element  12 . In the present example, the inner face  23  has a generally flat centre surface  24  joined to the wall  22  by angled surfaces  25 . As best seen in  FIG. 1 , a central portion  26  of the flat face  24  is formed as a circular recess. In this example the side wall  22  is generally hexagonal and made of six internal walls, defining a cavity  21  which is a regular hexagon 
         [0048]    A tissue engagement means is generally shown at  30  to draw tissue into the cavity  21 . In the present example, this is performed by suction. A central part of the lower element  12  defines a vacuum distribution chamber  31 , the distribution chamber having annular upstanding wall  32 . The chamber  31  is in flow communication with the cavity  21  through channels  31   a.  The upper surface of the distribution chamber  31  is closed by a cap part  33 . The cap part  33  comprises a planar element  34  with annular wall  35  extending around the periphery. The dimensions of the planar element  34  and annular walls  35  are such that when the cap  33  is in position, the annular wall  35  engages the outer surface of the upstanding wall  32 . Seals  36  ensure a sealing engagement between the annular wall  35  and upstanding wall  32 . A connection nipple  37  is mounted on the cap  33  with a channel  38  extending therethrough to enable the vacuum distribution chamber  31  to be connected to a vacuum or low pressure source. 
         [0049]    To provide for treatment, the treatment device  10  comprises ultrasonic transducers  40  and radiofrequency (RF) electrodes. As shown in  FIG. 4 , the ultrasonic transducers are shown at  40  and are mounted as opposed pairs adjacent the surfaces of the side wall  22  inwardly of the contact surface  20  and spaced from the closed end wall  23 . The internal volume  27  of the contact part  13  may be filled with any appropriate material. The ultrasonic transducers  40  may alternatively be mounted elsewhere in the volume  27  and suitably angled as desired. In this example, the ultrasonic transducers comprise flat piezoelectric ultrasonic transducers, each of which generates a generally straight, unfocussed ultrasonic beam in a direction perpendicular to their surface, and hence perpendicular to walls  22  and into the cavity  21 . 
         [0050]    Radio frequency (“RF”) transducers  41  are similarly mounted on the angled surfaces  35 . In the present example, an auxiliary RF electrode is shown at  42  disposed in the recessed area  26  of the flat face  24  of the cavity  21 . The RF transducers  41  are thus offset from the ultrasonic transducers  40 , and are located closer to the closed end wall  23 . 
         [0051]    The ultrasonic transducers are preferably mounted in opposed pairs to overcome attenuation of the ultrasonic beams within tissue, as illustrated in the graphs of  FIG. 5 a    and  FIG. 5 b   . The higher the ultrasonic frequency, the greater the attenuation within the tissue.  FIG. 5 a    is a graph showing the transmitted power between two transducers separated by 3 cm, at a frequency of 2 MHz.  FIG. 5 b    shows the transmitted power between two plates separated by 6 cm, at a frequency of 400 kHz. In each case, the power transmitted by the separate plates is shown by red and blue lines, from the right and left respectively, and the attenuation with distance is clearly apparent. The combined power is shown in green, and it is apparent that there is a generally even energy distribution generated in the tissue between the plates. In this way, the treatment occurs across the gap between the two plates. In particular, as the tissue between the plates is heated above the treatment level across the whole of the cavity in an even manner, there is no need to ‘overheat’ tissue near an ultrasonic transducer to increase the treated area, as would be required by a single transducer. 
         [0052]    In the present example, where there are 3 pairs of transducers arranged in a hexagonal orientation, the power generated within the cavity is shown diagrammatically in  FIG. 6 . Opposed ultrasonic transducers  40  each generate a beam generally illustrated at  50 . The beams overlap in a central area  51 . By selection of the power generated by each of the ultrasonic transducers  40 , the temperature elevation in tissue can be controlled such that only tissue within the zone  51  is heated to the required temperature to remove or destroy fat cells or adipose tissue, thus defining a treatment volume. In areas affected by only a single beam  52  or a pair of beams  53 , the energy imparted to the tissue is not sufficient to cause damage. At the same time as the ultrasonic transducers  40  are operated to cause fat destruction, the radiofrequency electrodes  41  may be operated to cause tightening in the skin above the treated area of tissue. 
         [0053]    In operation, as illustrated in  FIG. 7  and  FIG. 8 , tissue generally shown at  60  is drawn into the cavity  21  by applying a suitable vacuum to vacuum distribution chamber  31 . The side wall  22  can be shaped to optimise contact between the skin and side wall  22 . A suitable transmission medium such as a gel can also be applied to the skin. The skin layers in diagrammatic form have an epidermis  61 , a dermis  62  and a subdermal layer  63  containing fatty tissue. By drawing the tissue  60  into the cavity  21 , as can be seen the fatty tissue  63  is located between the transducers  40 , and only that tissue within volume  51  is affected, raising the temperature sufficiently to destroy the fat cells. As illustrated in  FIG. 8 , the RF electrodes  41  may be simultaneously operated to raise the temperature in the epidermis and dermis to cause skin tightening in known manner. By offsetting the ultrasonic transducers  40  and RF electrodes  41  in this way, different layers of the skin can be treated at once. 
         [0054]    Although the hexagonal arrangement of the cavity and ultrasonic transducers as shown herein is advantageous in terms of the volume treated, it is envisaged that other arrangements of the ultrasonic transducers may be used, such that a suitable treatment volume may be defined within the cavity  21  without the disadvantages of requiring local overheating as seen in known devices. For example, four or more transducers  40  may be arranged in a square, pentagonal or heptagonal configuration, or indeed with any number of sides. The polygonal arrangement need not be regular, as in the present example, but may comprise a compressed or irregular polygon depending on the shape and size of the desired treatment volume to be generated by the treatment device. 
         [0055]    When included in a treatment apparatus, a suitable controller may be provided to control the ultrasonic transducers  40  and RF electrodes in accordance with an operator&#39;s instruction to provide a desired operating regime. The ultrasonic transducers may be operated with a frequency in the range 200 kHz to 4 MHz, preferably 1 MHz to 3 MHz and most preferably 1.5 to 2.5 MHz, for durations in the range 0.1 seconds to 20 minutes, preferably 0.5 to 10 minutes and most preferably 1 to 6 minutes. The energy transmitted into the tissue may be in the range 50 to 700 J cm−3, preferably in the range 75 to 500 J cm−3 and most preferably 100 to 250 J cm−3. The transducers may be operated with duty cycle in the range 8 to 100%, preferably in the range 16.6 to 100% and most preferably in the range 33.33 to 100%. 
         [0056]    The ultrasonic transducers may be activated simultaneously or separately. For example, each pair of ultrasonic transducers may be operated in sequence, the duty cycle of each pair of transducers being controlled such that while one transducer pair is active, the other two transducer pairs are in a quiescent part of the duty cycle. Alternatively, individual transducers may be operated in any order, or groups of transducers may be operated together. In a particular cycle of operation, each individual transducer, pair of transducers or group of transducers may be operated once, or may be operated a plurality of times. Similar considerations may apply to the operation of the RF electrodes  41 . Accordingly, pairs of RF electrodes may be operated in sequence, the duty cycle of each pair of electrodes being controlled such that while one electrode pair is active, other electrode pairs are in a quiescent part of the duty cycle. It is believed this operation cycle may reduce patient discomfort. However, any other operation cycle may be used, and may be the same as, or different from, the operation cycle of the ultrasonic transducers. 
         [0057]    The RF electrodes may be operated with a frequency in the range 100 to 4000 kHz, preferably 300 to 2000 kHz and most preferably 500 to 1000 kHz, for durations in the range 10 to 5000 ms, preferably 30 to 2000 ms and most preferably 50 to 750 ms. The RF power may be in the range 5 to 100 W, preferably in the range 10 to 60 W and most preferably 20 to 40 W. The RF electrodes may be operated with a duty cycle in the range 8 to 100%, preferably in the range 16.6 to 100% and most preferably in the range 33.33 to 100%. The operating parameters may be selected in accordance with the desired treatment or results and the characteristics of the skin or tissue. 
         [0058]    The operating regime may include a cooling step as illustrated in  FIG. 9 . In  FIG. 9 , the temperature of a fatty subdermal layer (upper line) and skin or dermal layer (lower line) over time are shown. At 0s, a heating cycle has ended and a cooling period A occurs, in this example 60s. As the fatty subdermal layer is deeper, has a higher thermal capacity and a lower thermal conductivity, it cools at a much slower rate than the dermis. In a subsequent ultrasound heating cycle B, the temperatures of both the dermis and subdermal layer are increased, but because of cooling cycle A, the dermis has a lower starting temperature and is maintained below the temperature at which damage occurs. In contrast, the subdermal layer is raised above a treatment temperature, in this case about 44°. By allowing a further cooling cycle C before beginning heating, it will be apparent that the subdermal layer can be repeatedly treated without causing damage to an overlaying dermal layer. 
         [0059]    In the present example, the hexagonal walls 22 are about 30 mm long and enable a volume of 226.1 cm3 to be treated in six minutes, substantially more efficiently than an equivalent high-intensity focused ultrasound device. 
         [0060]    Further treatment elements are illustrated at  70  and  80  in  FIG. 10 , although one or both of these elements may be omitted or included as desired. 
         [0061]    Elements  70  are disposed on the closed end wall  23 , in such a manner that when tissue is drawn into the cavity  21 , the elements  70  can treat the skin or dermal layer which is disposed near the elements  70 . The elements  70  may be light sources or additional ultrasonic transducers, depending on the type of treatment desired. The energy delivered by the elements  70  may be delivered in a fractional manner, such that energy from each element  70  is delivered into separate, physically spaced locations on the skin, Advantageously, by treating the upper skin layers at the same time or immediately after treating the subdermal tissue layer, a skin tightening effect may be induced over the layers where fat reduction has been performed. 
         [0062]    Elements  80  comprise electrodes disposed on the contact surface  20  to perform pain reduction using transcutaneous electrical nerve stimulation (TENS). In TENS, an electrical current is used to stimulate A13nerve fibres, associated with touch signals. According to the ‘Gate’ theory of TENS, the activation of the A13 nerve fibres causes the activation of inhibitory spinal interneurons. The inhibitory spinal interneurons then block the transmission of information from Aδ and C nerve fibres associated with pain sensation. Consequently, by applying a suitable electrical signal to electrodes  80 , a local analgesic effect can be induced, minimising subsequent discomfort caused by the ultrasound treatment. 
         [0063]    In the above description, an embodiment is an example or implementation of the invention. The various appearances of “one embodiment”, “an embodiment” or “some embodiments” do not necessarily all refer to the same embodiments. 
         [0064]    Although various features of the invention may be described in the context of a single embodiment, the features may also be provided separately or in any suitable combination. Conversely, although the invention may be described herein in the context of separate embodiments for clarity, the invention may also be implemented in a single embodiment. 
         [0065]    Furthermore, it is to be understood that the invention can be carried out or practiced in various ways and that the invention can be implemented in embodiments other than the ones outlined in the description above. 
         [0066]    Meanings of technical and scientific terms used herein are to be commonly understood as by one of ordinary skill in the art to which the invention belong, unless otherwise defined.