Abstract:
A microwave applicator device comprising a probe ( 11 ) for ablating the body of a human or animal, a cooling passage sage ( 20, 21 ) extending through the probe ( 11 ) and arranged to carry a cooling fluid, a pump ( 71 ) for pumping the fluid through the probe ( 11 ), and an elongate flexible duct ( 104 ) extending between the pump ( 71 ) and one end of the cooling passage ( 20, 21 ), the pump comprising a pump body ( 73 ) including a motor ( 120 ) and a pump head ( 72 ) detachably mounted to the pump body ( 73 ), the pump head ( 72 ) comprising a first port ( 86 ) connected to a proximal end of the elongate flow duct ( 104 ), a second port ( 85 ) and fluid propulsion means ( 84, 92 ) for creating a flow of fluid between the ports ( 85, 86 ) and along the elongate flow duct  104  upon energization of the motor ( 120 ), the pump head ( 72 ) being arranged to sealingly contain the fluid. The pump head ( 72 ), the elongate flexible duct ( 104 ) and the probe ( 11 ) form a replaceable assembly that can be detached from the pump body ( 73 ) and discarded following use.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This is a National Stage entry of International Application No. PCT/GB2010/051625, with an international filing date of Sep. 29, 2010 which claims priority of Great Britain patent application no. 0917431.9, filed Oct. 6, 2009 entitled “Medical Devices and Pumps Therefor” 
     FIELD OF INVENTION 
     This invention relates to medical devices and to pumps which are more particularly but not solely intended for use therewith. 
     RELATED BACKGROUND ART 
     It is well known to ablate body tissue using a microwave applicator which heats and destroys the surrounding tissue. One use of such an applicator is in the non-invasive treatment of cancer in an internal body organ such as the liver. GB2415630 discloses an applicator of the above-mentioned type comprising a probe having a thin elongate shaft which can be inserted into the patient for treatment. The proximal end of the probe comprises a handle which is connected to an external microwave generator by an elongate flexible cable. A thin elongate microwave transmission line extends inside the probe from the handle to a radiating tip or antenna disposed at or adjacent the distal end of the probe. In use, the microwave field radiated from the tip heats and ablates the surrounding tissue in a localised area. 
     A disadvantage of the above-mentioned applicator is that the probe can heat up for a variety of reasons. Firstly, power losses can occur in the transmission line extending along the probe to the tip, which power losses heat the transmission line and the surrounding parts of the probe. Secondly, the radiated microwave energy can heat the probe. Thirdly, the heat from the ablation can be conducted back along the probe. Such heating of the probe is undesirable, since it can burn the patient&#39;s skin at the point of entry of the probe or it can burn other parts of the patient&#39;s body adjacent the shaft of the probe: for this reason UK government regulations specify that no external part of any medical apparatus should exceed 48° in temperature. 
     In order to overcome the above-mentioned problems, it is known to pass a liquid, such as a saline solution, along the probe of the applicator so as to cool the probe. One such applicator is disclosed in our co-pending International Patent Application No. PCT/GB2009/050113 filed 5 Feb. 2009, the contents of which are incorporated herein by reference, and comprises a probe having a pair of flow channels extending longitudinally along its shaft parallel to the transmission line, the channels being interconnected at the distal end of the shaft adjacent the radiating tip. In use, cooling fluid can be pumped through the probe to its distal end along one flow channel and then returned along another flow channel. A pair of flexible ducts extend from a handle of the probe and respectively allow the fluid flow into and out of the channels. 
     It will be appreciated that the flow channels have a very small diameter and hence and object of the present invention is to provide a pump which can create a sustained and reliable fluid flow through these channels that sufficiently cools the shaft of the probe. 
     Microwave applicator probes are generally single-use disposable items due to the fact that they cannot be reliably cleaned and sterilised following insertion into the human body. Also, since there is a risk that fluid flowing through the probe inside the body could become contaminated, it will be appreciated that both the fluid and the ducts carrying the fluid into and out of the probe need to be discarded following use. A problem with this is that the fluid also comes into contact with the pump and thus there is a risk that the fluid will contaminate the pump either directly or by virtue of the fact that there is a direct path for contaminants to travel back to the pump along the duct which connects it to the probe. Whilst pumps are difficult to clean and sterilise, they are too expensive to be discarded after each use. Accordingly, another object of the present invention is to provide a pump which overcomes this problem. 
     We have now devised a medical device which meets the above needs and objectives and which can be used in the treatment, therapy or diagnosis of the human or animal body. 
     SUMMARY OF THE INVENTION 
     In accordance with the present invention, as seen from a first aspect, there is provided a medical device comprising a distal head portion for contacting the body of a human or animal, a cooling passage extending through the head portion and arranged to carry a fluid for cooling the head, a pump for pumping said fluid through the head portion, and an elongate flexible duct extending between the pump and one end of the cooling passage, said pump comprising a pump body including a motor and a pump head detachably mounted to the pump body, the pump head comprising a first port connected to a proximal end of said elongate flow duct, a second port and fluid propulsion means for creating a flow of said fluid between said ports and along said elongate flow duct upon energisation of said motor, said pump head being arranged to sealingly contain said fluid, wherein the pump head, the elongate flexible duct and the head portion form replaceable assembly that can be detached from the pump body following use. 
     It will be appreciated that any risk of contamination is avoided because the pump head, the elongate flexible duct and the head portion are all provided as a single and preferably sterile assembly which can be discarded following use. Since only the head of the pump is replaced, the replacement cost is reduced and indeed the pump head can be formed as a relatively low cost item. The pump head sealingly contains the fluid and thus the fluid does not come into contact with any unsterile parts and also cannot contaminate any parts of the device other than the replaceable assembly. Since, all of the parts which come into contact with the fluid are discarded, the need for cleaning and sterilisation is avoided. 
     Preferably the assembly comprises a further elongate flexible duct having a distal end extending from the other end of the cooling passage of the head portion: this further elongate flexible duct carries fluid in the opposite direction to the aforementioned elongate flexible duct and, in a preferred embodiment, is arranged for connecting to a fluid drain. 
     Preferably said further elongate flexible duct forms part of the disposable assembly. 
     Preferably an electrical cable extends to said head portion of the device, the cable preferably also forming part of said replaceable assembly. 
     Preferably the pump comprises a pump housing, said cable extending from said pump housing preferably being connected thereto by means of a connector provided on the pump housing. 
     Preferably a further cable extends from the pump housing to a main unit of the device, means being provided in said pump housing for connecting said further cable to the aforementioned cable which extends to said head portion of the device. In this way the main unit can be positioned at a remote location and the head portion is then simply electrically connected thereto by connecting it to the pump housing, which can be located adjacent the human or animal. 
     Preferably, the head portion comprises a microwave antenna for performing ablation of the human or animal body, the main unit comprising a magnetron or other source of microwave radiation. 
     Preferably the cable is also arranged to be cooled by said fluid as it flows along a said elongate flexible duct. The cable preferably forms a wall of said elongate flexible duct, the duct preferably defining a cooling jacket which surrounds the cable. 
     Preferably the cable is cooled by said fluid as it flows along said further elongate flexible duct. 
     Preferably, said further elongate flexible duct comprises a first portion having a distal end connected to said head portion of the device and a proximal end connected a first port of a manifold, the first portion of said further elongate flexible duct being arranged to cool said cable, said further elongate flexible duct further comprising a second portion which extends from a second port of the manifold, the manifold having a third port for entry of the cable, the manifold being sealed and arranged such that the cable entering the manifold extends inside said first portion of said further elongate flexible duct and is cooled by fluid flowing via the first and second ports of the manifold, said manifold forming part of the disposable assembly. 
     Preferably the manifold comprises a further port to allow another cable to extend inside said first portion of said further elongate flexible duct: this further cable may carry signals from a sensor disposed in said head portion of the device. 
     Preferably the manifold is disposed adjacent the pump 
     Preferably the assembly comprises another elongate flexible duct connected to said second port of the pump head: preferably the distal end of this other elongate flexible duct is arranged for connecting to a fluid source, such as a bag containing saline. 
     Preferably said other elongate flexible duct forms part of the disposable assembly. 
     Preferably the pump comprises an actuator which is driven by said motor, said fluid propulsion means being arranged to detachably engage the pump actuator. 
     Preferably said fluid propulsion means is arranged to magnetically couple with the pump actuator. 
     Preferably said fluid propulsion means comprises a piston. 
     Preferably the pump actuator comprises a reciprocating shaft having one end arranged to couple with said propulsion means. 
     Preferably the shaft reciprocates along an axis, said end of the shaft extending through an aperture in an outer wall of the pump body, the wall lying normal to said axis. 
     Preferably the pump comprises means for positioning the shaft in a position in which said end thereof is substantially in the same plane as the outer surface of said pump wall when stopped, so as to facilitate connection of the pump head. 
     Preferably the pump head is arranged to slide into a position on said outer surface of said pump wall in which said fluid propulsion means couples with the pump actuator. 
     Preferably the pump head is arranged to slidably rotate into a position on said outer surface of said pump wall in which said fluid propulsion means couples with the pump actuator. 
     Preferably the pump head is arranged to slidably rotate about an axis which extends normal to the plane of said outer surface of said pump wall, means being provided for rotationally coupling the pump head to the pump body for rotation about said axis. 
     Preferably the said means for rotationally coupling the pump head to the pump body comprises an electrical connector for coupling the cable to the pump body. 
     Preferably the electrical connector comprises a coaxial connector. 
     Preferably the pump head comprises one or more electrical terminals which engage corresponding electrical terminals on the pump body when the pump head is slid into said position on the pump body: these terminals may carry signals from a sensor in the head of the device. 
     Preferably means are provided for locking the pump head to the pump body when the motor is running. 
     Also in accordance with the present invention, as seen from a second aspect, there is provided a pump comprising pump body having a pump motor arranged to drive an actuator, and a pump head detachably mounted to the pump body and having a first port, a second port and fluid propulsion means for creating a flow of said fluid between said ports upon energisation of said pump motor, said pump head being arranged to sealingly contain said fluid. 
     Also in accordance with the present invention, as seen from a third aspect, there is provided a pump comprising pump body having a pump motor arranged to drive an actuator, and a pump head detachably mounted to the pump body and having fluid propulsion means for creating a flow of fluid between first and second ports of the pump head, the propulsion means being magnetically coupled to the pump actuator. 
     Also in accordance with the present invention, as seen from a third aspect, there is provided a motor having a body, a stator shaft fixed to the body and a rotor arranged to rotate around the shaft, the rotor having an axially extending circumferential formation on its external surface, means being provided on the body for engaging the formation to impart linear movement to an actuator upon rotation of the rotor. 
     Preferably the actuator comprises a reciprocating shaft which reciprocates along an axis, said axis extending parallel to the axis of motor rotation. 
     Preferably the actuator comprises an arm which extends radially from the shaft and engages the formation at the outer end thereof. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       An embodiment of the present invention will now be described by way of an example only and with reference to the accompanying drawings, in which: 
         FIG. 1  is a schematic view of an embodiment of microwave applicator device in accordance with the present invention; 
         FIG. 2  is a perspective outline view of the distal end of a probe of the applicator device of  FIG. 1 ; 
         FIG. 3  is a perspective outline view of the proximal end of a shaft of the probe of the applicator device of  FIG. 1 ; 
         FIG. 4  is a perspective outline view of the proximal end of the probe and a microwave feed cable of the applicator device of  FIG. 1 ; 
         FIG. 5  is a perspective view of a pump of the applicator device of  FIG. 1 ; 
         FIG. 6  is a sectional view through a portion of the head of the pump of  FIG. 5 ; 
         FIG. 7  is a sectional view through a manifold of the applicator device of  FIG. 1 ; and 
         FIG. 8  is plan view of a motor and actuator of the pump of  FIG. 5 . 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Referring to  FIG. 1  of the drawings, there is shown a microwave applicator device comprising a microwave generator  10  having an elongate main output cable  70  connected to a pump  71 . The cable  70  is directed connected inside the pump  71  to the proximal end of an elongate flexible feed cable  12 . The distal end of the elongate flexible feed cable is connected to an applicator probe  11 . The probe  11  comprises a handle portion  13  and an elongate shaft portion  14  extending from the handle  13 . In use, the generator  10  generates a microwave signal which is transmitted along the cables  70 , 12  to the probe  11 . The microwave signal is then transmitted along the shaft  14  of the probe to a radiating tip  15  at the distal end thereof. 
     Referring to  FIG. 2  of the drawings, the shaft  14  comprises an external elongate tubular wall  14  formed of stainless steel. A co-axial transmission line  17  extends internally of the tubular wall  14 , the transmission line  17  being coupled at its proximal end to the microwave feed cable  12  and at its distal end to a radiating antenna  16  which extends inside the tip  15  of the probe  11 . An elongate flow dividing member  19 , in the form of a solid cable or wire, co-extends with the co-axial transmission line  17  along a substantial part of the length thereof, the member  19  terminating a short distance away from the radiating antenna  16 . 
     The combined diameter of the transmission line  17  and the flow dividing member  19  is slightly greater than the internal diameter of the tubular external wall  18 , such that the transmission line  17  and flow dividing member both positively contact the internal surface of the external tubular wall  18  and each other along a substantial part of the length of the shaft  14 . The transmission line  17  and flow dividing member  19  thus together define two flow channels  20 ,  21 , which extend longitudinally of the shaft  14  from the proximal end to the point at which the flow dividing member  19  terminates. The two flow channels  20 ,  21  are interconnected beyond the point at which the flow dividing member  19  terminates. 
     Referring to  FIGS. 3 and 4  of the drawings, one of the channels  20  is sealed by a member  22  at the proximal end of the shaft  14 . A plurality of apertures  27  are formed in the external tubular wall  18  of the shaft  14  at the proximal end thereof, the apertures  27  communicating with the sealed channel  20 . The proximal end of the shaft  14  extends into a manifold  23  disposed inside the handle  13  of the probe  11 . The manifold  23  is generally cylindrical and is divided into two axially-disposed chambers  24 ,  25  by a boundary wall  26  which extends normal to the longitudinal axis of the shaft  14 . The proximal end of the shaft  14  extends into the manifold  23  and through the boundary wall  26 , such that the apertures  27  open into the distal chamber  24  of the manifold  23 , the second (un-sealed) flow channel  21  of the shaft  14  opening into the proximal chamber  25  of the manifold  23 . An inlet port  28  extends radially outwardly from the side wall of the manifold  23 , the inlet port  28  communicating with the distal chamber  24  of the manifold  23 . 
     The distal end of the feed cable  12  extends through the proximal end wall  30  of the manifold  23  and is connected to the proximal end of the transmission line  17 . The feed cable  12  extends from the probe  11  towards the pump  71  inside a tube  28 . 
     Referring to  FIG. 5  of the drawings, the pump  71  comprises a pump head  72  detachably mounted to a pump body  73 . The pump head  72  comprises a back plate  74  having a flat rear surface for fitting against the flat front surface  75  of a housing  76  of the pump body  73 . The main microwave cable  70  from the microwave generator  10  is directly connected inside the pump housing  76  to a co-axial connector  77  disposed on the front wall  75  of the housing  76 . The proximal end of the feed cable  12  extends into the back of a complimentary co-axial connector  78  disposed on the front surface of the back plate  74  of the pump head  72 , the connector  78  having a co-axial terminals (not shown) which project rearwardly from the rear surface of the back plate  74  for engaging with the corresponding terminals of the connector  77  on the pump body  73 . 
     A reciprocally-driven pump actuator shaft  79  of ferromagnetic material has an outer end which extends through an aperture  80  in the front wall  75  of the pump body  73 . The aperture  80  is disposed radially outwardly of the connector  77 . A T-shaped projection  81  having an enlarged outer end extends outwardly from the front wall  75  of the pump body  73  at a position that is disposed between the connector  77  and the aperture  80 . 
     An aperture  82  is formed in the back plate  74  of the pump head  72 , the aperture  82  having a diameter which is slightly greater than the diameter of the enlarged head of the T-shaped projection  81 . A slot  82  extends across the back plate  74  from the aperture  82  in a counter clockwise direction, along an arcuate line which is centred about the centre of the co-axial connector  77 . 
     An elongate tubular-walled pump barrel  84  extends outwardly from the front surface of the back plate  74  of the pump head  72 , the pump barrel  84  being closed at its outer end by a hemispherical end wall. The inner end of the pump barrel  84  opens through an aperture in the back plate  74  of the pump head  72 . Fluid inlet and outlet ports  85 ,  86  extend through the side wall of the pump barrel  84  at diametrically opposed positions adjacent the back plate  74 . 
     In use, the rear surface of the back plate  74  of the pump head  72  is fitted in face-to-face registration with the front wall  75  of the pump body  73  by aligning the pump head  72  in front of the pump body  73 , such that the connector  78  thereon is disposed in front of the connector  77  on the pump body  73  and such that the head of the T-shaped projection  81  is aligned with the aperture  82  in the back plate  74 . The pump head  72  and the pump body  73  are then brought together, so that the connector  78  couples with the connector  77  and so that the head of the projection  81  extends through the aperture  82 . Next, the pump head  72  is rotated in a clockwise direction, with the connector  77 ,  78  acting as the rotational axis for the pump head  72 : the connector  77  is preferably free to rotate with respect to the pump body  73 . Continued rotation of the pump head  72  causes the stem of the projection  81  to travel along the slot  83  in the back plate  74  until it reaches the end thereof: in this position the head of the projection  81  extends over the front surface of the back plate  74  and thereby locks the pump head  72  in-situ on the pump body  73  in a position where the proximal end of the pump barrel  84  is axially aligned with the aperture  80  in the front wall  75  of the pump body  73 . 
     A pump motor is disposed inside the pump body  73 , as shown in  FIG. 8 . When the motor is actuated, a pin  90  extends out of the front wall  75  of the pump body  73  into an aperture  91  formed in the back plate  74  of the pump head  72 . In this manner, removal of the pump head  72  from the pump body  73  is prevented when the motor is running. 
     Referring  FIG. 6  of the drawings, a piston  92  is mounted inside the pump barrel  84  for reciprocal movement axially of the pump barrel  84 . The proximal end of the piston  92  comprises a magnet  93 , which magnetically couples to the end of the actuator shaft  79  disposed inside the aperture  80  in the front wall  75  of the pump body  73 . The pump motor ( FIG. 8 ) is controlled such that the axial end of the shaft  79  always lies co-planer with the front wall  75  of the pump body  73  when stopped, thereby ensuring that the pump head  72  can rotatably slide into position on the pump body  73  as hereinbefore described and ensuring that the magnet  73  satisfactorily couples with the shaft  79  once the locked position is reached. 
     The fluid inlet and outlet ports  85 ,  86  on the pump body  84  comprise respective valves  95 ,  96  which respectively allow fluid into and out of the pump barrel  84 . The ports  85 ,  86  communicate with respective channels  97 ,  98  which extend axially along the internal surface of the tubular side wall of the pump valve  84  towards the distal end thereof. 
     In use is the shaft  79  of the pump actuator reciprocates, the piston  92  moves in and out of the pump barrel  84 , thereby drawing fluid into the pump barrel  84  through the inlet  85  on the inward stroke and pumping fluid out of the pump barrel  84  through the outlet  86  on the outward stroke. 
     Referring again to  FIG. 1  of the drawings, the inlet port  85  of the pump head  72  is connected via a tube  100  to a bag  101  of saline solution or other cooling fluid. The bag  101  may be suspended at an elevated position on an arm  102  extending upwardly from a trolley  103  in which the pump  71  is mounted. The outlet port  86  of the pump head  72  is connected via an elongate tube  104 , which connects to the port  28  on the handle  13  of the probe ( FIG. 4 ). 
     Referring again to  FIGS. 2 to 4  of the drawings, when energised, the pump  71  pumps cooling fluid along the tube  104  into the distal chamber  24  of the manifold  23  of the probe  11  through the inlet port  28 . The cooling fluid then flows through the apertures  27  in the external tubular wall  18  of the shaft  14  and into the flow channel  20 . The cooling fluid then flows longitudinally of the shaft  14 , thereby cooling the external wall  18  of the shaft and the transmission line  17 . The cooling fluid then crosses from the flow channel  20  to the other flow channel  21  at the distal end of the shaft  14 , beyond the point at which the flow dividing member  19  terminates. The cooling fluid then returns along the shaft  14  via the cooling channel  21 , whereupon it flows into the proximal chamber  25  of the manifold  23 . The fluid then flows out of the manifold  23  and into the tube  28 , whereupon it flows over the cable  12  in an annular flow channel defined formed between the tube  28  and the co-axial cable  29 . 
     The proximal end of the tube  28  is connected to a manifold  110  positioned adjacent the pump head  72 . Manifold  110  comprises a first port  111 , through which the cable  12  sealingly leaves the manifold  110  to enter the back of the connector  78  on the pump head  72 . The manifold  110  comprises a second port  112 , which fluidly connects to a tube  113  ( FIG. 1 ) leading to a drain or collection vessel  114 . One or more other ports  115  optionally allow other wires or cables  116  to sealingly enter the tube  28  and to co-extend with the cable  12  to the probe  11 . These cables or wires  116  can carry signals from sensors, such as thermocouples mounted in the probe  11 . Such sensors may disable the microwave generator  10  in the event that the probe  11  overheats. 
     The fluid from the bag  101  thus initially flows through the pump head  72  and along the tube  104  to the probe  11  where it cools the shaft  14  and transmission lines  17  of the probe. The fluid then returns via the tube  28  to cool the feed cable  12  before flowing to the drain or collection vessel  114 . 
     Following use, the pump head can be disconnected from the pump body  73  by rotating it in a counter clockwise direction. The tube  100 , the pump head  72 , the tube  104 , the probe  11 , the tube  28 , the cable  12 , the manifold  110  and the tube  113  form a disposable sterile assembly which can be discarded following use to avoid any risk of cross-contamination and to avoid any necessity to clean any of the parts through which fluid flows. It will be appreciated that a disposable assembly can be provided as a relatively inexpensive item compared with the cost of the pump body  73 . 
     Referring to  FIG. 8  of the drawings, the pump body  73  comprises a pump motor  120  comprising a static shaft  121 , which is mounted at its opposite ends to the pump housing  76 . A tubular rota  122  extends around the shaft  121 , means being provided between the shaft  121  and rota  122  for causing rotation of the latter about the shaft upon application of a suitable energisation signal. 
     The circumferential outer surface of the rota comprises a groove  123 , which circumferentially and axially of the rota  123 . A block  126  are slidably mounted on rails  125 , which extend parallel to the motor shaft  121 . A pin  124  projects from the block  126  into the grove, such that rotation of the rota  122  causes the block  126  to move to-and-fro along the rails  125 . The aforementioned actuator shafts  79  of the motor extends from the block  126  into the aperture  80  in the front wall  75  of the pump body  73 . 
     The grove  23  maybe sinusoidal, so that the actuator moves at the same rate in both directions. However, the groove  23  is preferably configured so that the inward stroke of the pump is short and so that the outward (pumping) stroke is long, thereby reducing intervals between successive fluid flows through the probe  11 . 
     A microwave applicator probe in accordance with the present invention is relatively simple and inexpensive in construction, yet enables the probe to be reliably cooled.