Patent Publication Number: US-2010113874-A1

Title: Teleoperated endoscopic capsule

Description:
FIELD OF THE INVENTION  
     The present invention relates generally to the field of endoscopic devices and more precisely, relates to an endoscopic capsule for diagnostic and/or therapeutic purposes, remote controlled, and able to move inside various areas in the human body, and in particular in the gastrointestinal area, more in particular, in a passive manner in the small intestine and in an active manner in the colon. 
     DESCRIPTION OF THE PRIOR ART  
     As is known in recent years there has been an increasing interest in devices that permit endoscopic examination and treatment in the most autonomous and least invasive manner. 
     For this purpose semi-automatic locomotive solutions have been studied with terminals mounted with a video camera, based on a “inchworm locomotion model, such as the endoscopic device described in WO02/68035. These systems have the drawback of limited possibility of control of the locomotion parameter, and the speed cannot be varied at all. In addition, they also have the drawback that their bodies creep along the walls of the body cavity inside which they move without being able to avoid possible lesions and pathological sites. 
     Endoscopic devices controlled from the exterior through force fields (a magnetic field for example) have been disclosed; these devices require that the patient wear suitable equipment to generate the field). As an example, the device known as Norika 3 produced by the Japanese company RF System Lab can be taken as a reference. However the use of these devices can create problems and even be dangerous because of possible interference with other biomedical devices applied to the patient. Moreover, this kind of externally controlled endoscopic devices also involve the risk of side effects due to extensive exposure to electromagnetic fields. 
     A completely autonomous endoscopic device for detecting images with wireless data transmission, integrated in a small capsule, is described in the U.S. Pat. No. 5,604,531. The device comprises a CMOS image generator, a transmitter, LED illumination and energy supply provided by a watch battery. The main limits of this device concern the lack of active locomotion control: the capsule move forward through the effect of normal peristalsis and, during its movement, cannot stopped nor oriented. 
     Some solutions intended to provide a solution to the problem of the active locomotion control comprise a capsule equipped with autonomous locomotion means controllable by an external operator. In general, these solutions comprise a cylindrical body having a plurality of locomotion modules arranged on the surface that permit the movement inside the body cavity to be explored. Housed in the cylindrical body are a source of energy, a microcontroller to drive the locomotion modules according to commands transmitted through remote control by the operator, a video camera for image acquisition controlled by a micro-controller, a transceiver system to receive the commands transmitted through remote control by the operator and to transmit the acquired images through the video camera. 
     In any case, these “autonomous” systems require that a gas be introduced to distend the walls of the cavity to be explored so as to permit the movement of the capsule, and an optimised vision of the cavity. The use of this gas is a painful experience for the patient subjected to endoscopic examination. 
     A solution aimed at avoiding the use of gas is described in WO2006121239 relating to a capsule with integrated locomotion means and a radio control managed by an external operator. The capsule has an external cylindrical body provided with a transparent spherical cap at the end housing a video camera and various electronic means for operation and control as well as for radio signal transmission/reception. The capsule locomotion means are basically composed of hooking teeth that protrude from longitudinal slits formed on the cylindrical body and that are hinged to a block mounted on a nut screw cursor coupled with a worm screw driven by an electric motor present inside, and firmly attached to, the body. When the worm screw is rotated in one direction, the teeth extend outside the body to grip the walls of the cavity to go through and to be examined, and the block with the teeth moves towards the rear end of the body; however, since the teeth are hooked into the cavity walls, this results in a forward movement of the body in the cavity similar to a creeping movement. When the worm screw is turned in the opposite direction, the block performs a forward axial movement, while the teeth are retracted back inside the body and the capsule remains still. 
     However fully satisfactory the component miniaturisation may be, the capsule in this solution is unable to turn or tilt to observe details of the cavity under examination. Moreover, it is unable to perform a reverse movement nor can it move in vertical direction, in view of the fact that for a part of the locomotion cycle, none of the teeth are able to hook into the cavity wall. Moreover, the capsule is unable to adapt itself to the various geometries featuring the gastrointestinal tract and it does not comprises any systems able to distend the surrounding intestinal walls adequately, an aspect which is very important from a diagnostic viewpoint to permit optimal observation of intestinal tissue. 
     Another solution aimed at avoiding the use of gas, is disclosed in WO2005082248. In particular, in this case the locomotion modules are formed by six legs hinged to the cylindrical body and controlled by a drive system composed of wires connected to each leg and acting in opposition to displace it angularly around the hinge axis. The wires are connected to electric contacts by transmission means. Both the legs and the wires are made in SMA (Shaped Memory Alloy). One of the two opposite wires is heated through the passage of electrical current, bringing it to the phase transition temperature of the SMA, resulting in the contraction of the wire (the cold wire is deformed through the action of the hot wire) and the rotation of the leg. When the electrical supply is cut off, the temperature is lowered and the wire stops its traction force, permitting the counteracting wire, heated successively, to contract, thus completing the return movement of the leg and at the same time, bringing the first wire back to its original length. The legs project in a radial direction in relation to the axis of the cylindrical body, and in an equally distanced manner around said axis, so that when the cavity tracts to be explored have a cross-section smaller than the size of the capsule with the legs projected, it provokes the expansion of the cavity. 
     However advantageous this solution may be as regards the possibility of directing the capsule, the compact size and the “distension” of the tracts to be explored compared to the prior art capsule devices, it nevertheless possesses certain aspects to be improved; these aspects are mainly related to the high power consumption due to the wire heating, this resulting in the reduction in the operating range of the device. Moreover, the force generated by the SMA wires can be insufficient for the complete expansion of the intestinal lumen, this resulting in a difficult forward movement due to the friction provided by the non-distended tissue. Furthermore, not always the legs are able to remain attached to, or in adhesion with, the cavity walls because of the wall irregularity and, slippery surface. To ensure adherence, the force of contact must be increased, but this requires the use of wires with a larger section, resulting in a size increase and greater energy consumption, as well as a reduction in the frequency of the locomotion cycle because of the amount of heat to be eliminated. 
     The main object of the present invention is to provide an endoscopic capsule having autonomous movement and energy supply within the body cavity, with the possibility of controlling the movement from the exterior to permit medical, diagnostic and therapeutic procedures, to be carried out and in particular, to be able to transmit images of the interesting areas in the body cavity through which it passes. 
     Another object of the present invention is to provide a teleoperated endoscopic capsule able to move in an autonomous manner inside the cavity to be explored without the need for using gas to expand the cavity walls. 
     Another object of the present invention is to provide a teleoperated endoscopic capsule that can adapt well to the environment in which it is placed without provoking, irritation or injury to the surrounding tissues. 
     A further object of the invention is to provide an endoscopic capsule equipped with autonomous locomotion means, wherein its movement can be easily stopped, accelerated or reduced according to need through an external remote control. 
     Another object of the invention is to provide an endoscopic capsule equipped with autonomous locomotion means that is able to turn corners easily. 
     SUMMARY OF THE INVENTION 
     These objects are achieved with a teleoperated endoscopic capsule for diagnostic and/or therapeutic purposes inside cavities in the human body, comprising a body defining a front part and a rear part, locomotion legs able to extend from said body, and moving means for said legs housed within the body, an energy source, means for acquiring images, means for signal reception/transmission from and to an operator in order to permit capsule control and the transfer of the acquired images. The legs are hinged to said body and are divided into two separate groups, the moving means comprising two driving devices, each one comprising a motor connected to a corresponding worm screw on which a translatable nut screw cursor is engaged, said nut screw cursor being kinematically connected to the legs of a respective group of legs. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Further characteristics and advantages of the endoscopic capsule according to the present invention will be made apparent from the following description of its embodiment, provided as a non-limiting example with reference to the appended drawings wherein: 
         FIG. 1  shows an axonometric view of a capsule according to the invention, illustrating the locomotion legs in their most extended position; 
         FIG. 2  shows an axonometric view of the capsule of  FIG. 1 , partially in section; 
         FIG. 3  shows an axonometric view of internal components of the capsule in the previous figures, in particular the device for the movement of the legs; 
         FIG. 4  shows a front view of the capsule, on a plane perpendicular to the axis of the capsule body; 
         FIG. 5  shows a schematic side view of part of the device which drives the leg movement, in which the most outspread position of a leg and the least outspread position shown in dotted line are depicted; 
         FIG. 6  shows a schematic side view of a part of the leg movement driving device, partially in section; 
         FIG. 7  shows a front view of a part of the driving device. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     With reference to the aforesaid figures, a teleoperated endoscopic capsule for diagnostic and/or therapeutic purposes according to the invention is identified throughout by the numeral  10 . 
     The capsule  10  comprises a body  11 , having a substantially cylindrical shape that defines a front part  12  and a rear part  13 . 
     At the end of the front part  12  the body  11  is provided with a transparent dome  14 , inside which are arranged means for image acquisition  15 , such as a digital video camera (associated lighting means of the known type, not shown) connected to a source of electrical energy  16  such as a watch battery, for example; both the video camera and the battery are shown schematically in  FIG. 2 . 
     Means for signal reception/transmission  17  to and from the external operator are housed under the dome  14 , to permit remote control of the capsule and the transfer of the acquired images to an external terminal, with which the operator is able to interface. These means are substantially of the known type, such as those described in the international patent application WO2005082248, but other functionally equivalent means can be used in alternative. 
     It is obvious how, in other embodiments, the video cameras can be more than one in number, such as two for example, positioned in the front part  12  and rear part  13  of body  11  respectively. 
     The, capsule  10  also comprises locomotion legs  18  able to project from the body  11 ; the means  19  for moving the legs  18 , illustrated in particular in  FIG. 3 , are positioned inside body  11 . In particular, the legs  18  are divided into two separate groups; a first group  20  is positioned towards the front part  12  the body  11 , while a second group  21  is positioned towards the rear part  13 . 
       FIGS. 2 and 3  show how the moving means  19  comprise two separate driving devices  22  for the legs  18 , which operate on the first and second groups  20  and  21  respectively; preferably, said driving devices  22  are substantially of the same type, as described below. 
     Each driving device  22  comprises a motor  23  connected to a corresponding worm screw  24  engaged with a nut screw cursor  25  kinematically connected to the legs  18 . The nut screw cursor  25  is forced to translate along the same worm screw  24  because of the slidable coupling to a guide bar  25   a , parallel to the worm screw  24  and connected rigidly to body  11 . 
     For example motor  23  is a direct current brushless type electric motor produced by Namiki Precision Jewel Co., Ltd., having an external diameter of 4 mm and a total length of 16.2 mm; said motor has an integrated speed reducer and the maximum delivered torque at the speed reducer shaft is equal to 2.92 mNm (the same motor without the speed reducer has a maximum delivered torque at the shaft equal to 0.058 mNm); said electric motor is powered by the battery  16 . 
     In particular, according to an important characteristic of the invention, the worm screws  24  of the two driving devices  22  are coaxial with the axis of body  11  and the motors  23  are positioned with their drive shafts  27  parallel to the axis of body  11 , and therefore on the opposite sides with respect to the common axis of the worm screws  24 . 
     Each motor  23  is connected to the corresponding worm screw  24  by means of a standard gearing with a transmission ratio less than 1; in particular the standard gearing is formed by a pinion  28  fixed at the end of the drive shaft  27  of motor  23  and a gearwheel  29 , having a diameter larger than the pinion  28 , fixed at the end of the worm screw  24 . The transmission ratio ranges between 0.420 and 0.430, preferably equal to 0.425; this is an optimal value in terms of the force delivered to the legs with the space occupied by the standard gearing. The motors  23  are positioned opposite to each other, and therefore the gearwheels  29  of the two worm screws  24  are positioned at each end of the screws. 
     The moving means  19  of the legs  18  also comprise electronic means (for simplicity not numbered in the figures) substantially of the known type, such as those described in the aforesaid international patent application WO2005082248, able to control the independent motion of the two groups of legs  18 , according to the commands from the external controller. 
     Each group  20  and  21  of legs  18  is connected to a respective nut screw cursor  25  (see in particular  FIGS. 5 ,  6  and  7 ). Preferably, at a first end of each of its own legs  18 , each group  20  and  21  has a first restraint  30  composed of a rotational attaching hinge  31  fixed to the nut screw cursor  25 , and at an intermediate position of the same leg  18 , a second restraint  32  that allows a roto-translation, with respect to a fixed point  33  of the body  11 , the rotation axis being parallel to the axis of the hinge  31 . 
     In particular, said second restraint  32  comprises a rotation pin fixed to the body  11  and a guide groove  35  defined along the corresponding leg  18 ; said pin  34  and groove  35  are coupled together with relative sliding, to allow the aforesaid rototranslation to be performed. 
     In practice, each nut screw cursor  25  can translate along the relative worm screw  24  from an initial position, in which the corresponding legs  18  are in their position of minimum extension (as can be seen in the part marked with the dotted line shown in  FIG. 5 ), laid along body  11 , to a final position, in which the legs  18  are in their maximum extension, projected towards the exterior of the body  11  with a angle such that the free ends  36  of the legs are positioned at the maximum distance from the axis of the body  11  (the part marked with the dark line in the drawing in  FIG. 5 ). 
     The driving devices  22  are housed inside the body  11 , which is formed with longitudinal slots  37  on the external surface, passing from the interior towards the exterior, to permit the legs  18  to protrude. More in particular, on the body  11  there are provided two groups of angularly equispaced slots, one group for each group of legs, extended respectively from the front end and from the rear end of the body  11  as far as an intermediate position thereof. The slots of one group are not aligned with the corresponding slots of the other group, but are staggered two by two, even though they are positioned closely to one another. 
     Advantageously, each group of legs  20  and  21  is formed of six legs  18 . This choice is the result of a number of tests performed with capsule prototypes presenting different numbers of legs. It was possible to observe from these tests that the locomotion performance increases with an increase in the number of legs. This is due to the fact that with an increased number of legs, the force of propulsion as well as the distension of the intestinal wall is distributed in a much more uniform manner. Therefore, while complying with the dimensional limits imposed by the diameter of the endoscopic capsules available on the market (approximately 11 mm), the number of legs has been maximised as far as twelve in number (six for each group). This number of legs achieves the aims proposed, as will be described more clearly below. 
     In  FIG. 4  the free ends of the legs of the first group  20  are identified with the numeral  36 ′, while the free ends of the legs of the second group  21  are identified with the numeral  36 ″. As shown in  FIG. 4 , the projections of the free ends  36  of the legs  18  of both the first group  20  and the second group  21  on a plane orthogonal to the axis of the corresponding worm screws  24  (coinciding with the axis of body  11 ) are arranged substantially on a same circumference, shown by the dotted line, whose centre coincides with said axis. 
     As can be seen from the figure, the free ends  36  are set at substantially the same angular distance from each other along the circumference. In particular, as shown in  FIG. 4 , when the legs  18  of both groups  20 - 21  are in their outspread position, the projections of the free ends on the plane orthogonal to the axis of the corresponding worm screw  24 , are arranged on a same circumference. More precisely, the legs belonging to the two groups alternate in the projection on the plane orthogonal to the axis of the capsule and, for dimensional reasons, the two legs of each group farthest from the respective motor are slightly displaced on an angle (about 4°) in relation to their ideal position. The above arrangement is required to avoid the degeneration of the volume of the capsule body that accounts for the equal distance spacing of the legs. More precisely, should the longitudinal slots of the aforesaid legs (slots inside which the said legs house when they fold to their completely retracted position) be arranged at the same angular distance in relation to one another, this would result in a collision between the legs during the retraction stage. This interference condition has been avoided by spacing the legs at a slight distance from each other. 
     In an intermediate point between the free end  36  and the guide groove  35 , each leg  18  is formed with an elastic knee portion  38  that forms a further degree of freedom to adapt the leg to the yielding nature of the tissue with which it comes into contact; in other words the terminal portion of the leg is elastically flexible around the knee portion. 
     Two opposing extensions  39  are positioned near the knee portion  38 , to limit the leg  18  rotation for a few degrees in its extension direction, while another pair of extensions  40  can be positioned at the opposite side of the leg  18  to abut each other after a wide rotation around the knee  38 . The pair of extensions  40  therefore limits the amount of flexion to which the leg  18  could be subjected, in order to prevent any possible damage thereof. 
     As shown in the figures, the free end of each leg is substantially hook-shaped for gripping the mucous membrane of the intestine to permit the forward movement; the size of the hooks is smaller than the thickness of the mucous membrane of the intestine (0.2 mm), in this way they do not damage the underlying tissue. 
     The function of the two groups of legs is different. The second group  21  is mainly aimed at driving the capsule motion, while the first group  20  is mainly aimed at attaching the capsule to the walls of the cavity under exploration, to facilitate the curved trajectories and to distend the walls to provide an optimal view thereof. 
     The endoscopic capsule according to the invention can be advantageously coated with a biocompatible and biodegradable layer that prevents the accidental outward extension of the legs during ingestion, making the swallowing action easier and safer. When the capsule reaches the stomach, the coating is destroyed by the acidity of the environment thus permitting the leg movements. 
     This capsule structure makes it possible to respect important constructive and dynamic parameters such as compact size (a length preferably between 24 mm and 28 mm), widespread angles for the legs (preferably between 90° and 130°), internal size that is sufficient to house the electronic components (thanks to motors that do not occupy more than 10.5% of the total volume of the body  11 ) controlled strength at the free ends of the legs (preferably between 1.8N and 3.2N) and number of legs (between 8 and 12). 
     Furthermore, thanks to the structure of the capsule according to the invention, it is possible to use a number of legs (twelve, in the example described) that is much larger than in other prior art capsules. 
     This provides several advantages, among which: a) the possibility of distending the cavity walls more easily for exploration, whereby the use of gas to expand the cavity is avoided; b) the possibility of low interaction force of each leg with the cavity walls, but with an overall force strong enough to permit hook gripping and locomotion along the walls, with the obvious advantage concerning the risk of tissue irritation and damage, and; c) greater flexibility in adjusting the locomotion speed. 
     The capsule according to the invention can be modified and varied in several ways, all of which are within the scope of the invention; all the details may further be replaced with other technically equivalent elements. In practice, the materials used, so long as they are compatible with the specific use, as well as the dimensions, may be any according to the requirements and the state of the art. 
     Wherever the characteristics and techniques described in any claim are followed by a specific reference, these have been included as an example for the sole purpose of making the claim descriptions easier to understand, and therefore they impose no limits on the interpretation of the element they refer to.