Patent Publication Number: US-2020297423-A9

Title: Surgery assisting apparatus and control method of the same, and surgery assisting system

Description:
This application is a continuation of International Patent Application No. PCT/JP2016/085615 filed on Nov. 30, 2016, and claims priority to Japanese Patent Application No. 2016-126708 filed on Jun. 27, 2016, the entire content of both of which is incorporated herein by reference. 
    
    
     BACKGROUND OF THE INVENTION 
     Field of the Invention 
     The present invention relates to a surgery assisting apparatus and a control method of the same, and a surgery assisting system. 
     Description of the Related Art 
     Laparoscopic surgery is conventionally performed by forming a small-diameter hole in the abdominal wall and inserting a medical instrument such as an endoscope or therapeutic device into the body cavity from the small-diameter hole. Since the range observable by the endoscope in the body cavity is narrower than the range within which the distal end of the medical instrument operates, there is the possibility that a part of the medical instrument touches and damages an organ or the like outside the field of view of the endoscope. To prevent contact on an organ by a medical instrument like this, methods of sensing contact or approach of a medical instrument to an organ or the like are known (Japanese Patent Laid-Open No. 2004-81277 and Japanese Patent Laid-Open No. 2015-159955). 
     Japanese Patent Laid-Open No. 2004-81277 discloses a technique which uses an endoscope having joints in a body insertion portion and controls the posture of the body insertion portion by sensing contact with a peripheral organ or another medical instrument by using a contact sensor of each joint. On the other hand, a technique which prevents contact between a medical instrument and an organ by measuring the three-dimensional shape of the organ by using a stereoscopic camera inserted from the body wall is known. Japanese Patent Laid-Open No. 2015-159955 discloses a technique in which a stereoscopic camera is installed in the distal end portion of a trocar inserted into the body cavity and a noninterference region between a medical instrument and an organ or the like positioned in the body cavity is set based on the three-dimensional position of the organ obtained by using the stereoscopic camera. 
     However, a medical instrument touches an organ in the technique disclosed in Japanese Patent Laid-Open No. 2004-81277, so this technique cannot be used for a fragile organ which is damaged only when touched. Also, in the technique disclosed in Japanese Patent Laid-Open No. 2015-159955, the camera is fixed in the distal end of the trocar for which only the angle of insertion into the abdominal cavity can be changed, so a dead angle is produced depending on the moving direction of a medical instrument. Consequently, the three-dimensional position of the medical instrument in a predetermined direction is not generated or the three-dimensional position is not the latest one in some cases. This sometimes makes it impossible to accurately sense approach of the medical instrument to a momentarily changing organ or the like. Japanese Patent Laid-Open No. 2015-159955 further discloses a method of setting a noninterference region by installing an electronic distance meter in the distal end of a medical instrument, instead of the stereoscopic camera. However, the measurement range is narrow because the electronic distance meter is installed in the distal end of a medical instrument, and it is impossible to detect interference in a shaft portion (a portion closer to the body wall than the distal end) other than the distal end of the medical instrument. 
     SUMMARY OF THE INVENTION 
     The present invention has been made in consideration of the above problems and realizes a technique capable of accurately sensing approach of a medical instrument inserted into the body cavity to an object in the body cavity. 
     In order to solve the aforementioned problems, one aspect of the present invention provides a surgery assisting apparatus comprising: a distance measuring unit configured to measure a distance to an object in a body cavity; a hollow tube including a cylindrical portion to be partially inserted into the body cavity and a portion that performs distance measurement by the distance measuring unit, the hollow tube enabling distance measurement by the distance measuring unit in a given position on a circumference at a predetermined distance from a major axis of the cylindrical portion; and a processor configured to perform the operations of a control unit configured to control the position on the circumference around the major axis where the distance measuring unit performs distance measurement, such that approach of a medical instrument inserted into the body cavity through the cylindrical portion to the object in the body cavity is sensed, wherein the control unit controls the position on the circumference around the major axis in accordance with an advancing direction of a distal end of the medical instrument. 
     Another aspect of the present invention provides, a surgery assisting apparatus comprising: a distance measuring unit configured to measure a distance to an object in a body cavity by using an optical part which emits light; and a hollow tube including a cylindrical portion to be partially inserted into the body cavity, and a holder in which a portion which causes the distance measuring unit to measure a distance in a major-axis direction of the cylindrical portion can project outside the cylindrical portion, wherein the hollow tube rotates around a major axis of the cylindrical portion such that approach of a medical instrument inserted into the body cavity through the cylindrical portion to the object in the body cavity is sensed, and the distance measuring unit measures the distance to the object in the body cavity by selecting one of a plurality of optical parts arranged in the holder such that optical-axis directions are different from each other. 
     Still another aspect of the present invention provides, a surgery assisting apparatus comprising: a distance measuring unit configured to measure a distance to an object in a body cavity by using an optical part which emits light; and a hollow tube including a cylindrical portion to be partially inserted into the body cavity, and a holder in which a portion which causes the distance measuring unit to measure a distance in a major-axis direction of the cylindrical portion can project outside the cylindrical portion, wherein the hollow tube rotates around a major axis of the cylindrical portion such that approach of a medical instrument inserted into the body cavity through the cylindrical portion to the object in the body cavity is sensed, and the holder further includes the optical part, and a wall which prevents a substance in the body cavity from sticking to the optical part, the optical part and the wall being spaced apart by a distance longer than a first distance at which the optical part can perform distance measurement such that sticking of the substance to the wall can be detected. 
     Yet another aspect of the present invention provides, a surgery assisting system comprising: a surgery assisting apparatus comprising: a distance measuring unit configured to measure a distance to an object in a body cavity; a hollow tube including a cylindrical portion to be partially inserted into the body cavity and a portion that performs distance measurement by the distance measuring unit, the hollow tube enabling distance measurement by the distance measuring unit in a given position on a circumference at a predetermined distance from a major axis of the cylindrical portion; and a processor configured to perform the operations of a control unit configured to control the position on the circumference around the major axis where the distance measuring unit performs distance measurement, such that approach of a medical instrument inserted into the body cavity through the cylindrical portion to the object in the body cavity is sensed, wherein the control unit controls the position on the circumference around the major axis in accordance with an advancing direction of a distal end of the medical instrument; and a medical instrument driving unit configured to control movement, in a body cavity, of the medical instrument inserted into the body cavity through the cylindrical portion, based on control information of the control unit, wherein in a case where approach of the medical instrument to the object in the body cavity is sensed, the control unit controls the medical instrument driving unit such that the medical instrument does not touch the object in the body cavity. 
     Still yet another aspect of the present invention provides, a method of controlling a surgery assisting apparatus including a distance measuring device for measuring a distance to an object in a body cavity, a hollow tube including a cylindrical portion to be partially inserted into the body cavity and a portion for performing distance measurement by the distance measuring device, the hollow tube enabling distance measurement by the distance measuring device in a given position on a circumference at a predetermined distance from a major axis of the cylindrical portion, and a control device, comprising: causing the control device to control the position on the circumference around the major axis where the distance measuring device performs distance measurement, such that approach of a medical instrument inserted into the body cavity through the cylindrical portion to the object in the body cavity is sensed, wherein, in the controlling, the position on the circumference around the major axis is controlled in accordance with an advancing direction of a distal end of the medical instrument. 
     Yet still another aspect of the present invention provides, a surgery assisting apparatus comprising: a distance measuring unit configured to measure a distance to an object in a body cavity; and a hollow tube having a cylindrical portion to be partially inserted into the body cavity, the hollow tube enabling distance measurement by the distance measuring unit in a given position around a major axis of the cylindrical portion, wherein the hollow tube further includes a holder in which a portion for performing distance measurement by the distance measuring unit can project outside the cylindrical portion, and the portion has an inclined portion in a position where the inclined portion comes in contact with another instrument into which the hollow tube is inserted in a case where the hollow tube is pulled out from the body cavity. 
     According to the present invention, it is possible to accurately sense approach of a medical instrument inserted into the body cavity to an object in the body cavity. 
     Other features and advantages of the present invention will be apparent from the following description taken in conjunction with the accompanying drawings. Note that the same reference numerals denote the same or like components throughout the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The accompanying drawings, which are incorporated in and constitute a part of the specification, illustrate embodiments of the invention and, together with the description, serve to explain the principles of the invention. 
         FIG. 1  is a view showing a configuration example of a surgery system including a surgery assisting apparatus according to an embodiment; 
         FIG. 2  is a view showing configuration examples of a hollow tube  6  and an optical part holder  5  according to the embodiment; 
         FIG. 3  is a view showing configuration examples of the hollow tube  6  and a hollow tube driving unit  7  according to the embodiment; 
         FIG. 4  is a view showing configuration examples of the hollow tube  6  and hollow tube driving unit  7  when using a hollow tube  41  according to the embodiment; 
         FIG. 5  is a view showing an example including a balloon  51  in the distal end of a mantle tube  4  according to the embodiment; 
         FIG. 6  is a view for explaining the optical axes of optical parts  21  and  22  according to the embodiment; 
         FIG. 7  is a view for explaining a method of controlling the sensing range of distance measurement in an object sensing process according to the embodiment; 
         FIG. 8  is a flowchart showing a series of operations of the object sensing process according to the embodiment; 
         FIG. 9  is a view showing the layout of optical parts according to another embodiment; and 
         FIG. 10  is a view showing the configuration of an optical part holder for sensing a stain according to still another embodiment. 
     
    
    
     DESCRIPTION OF THE EMBODIMENTS 
     Exemplary embodiments of the present invention will be explained in detail below with reference to the accompanying drawings. 
     (Configuration of Surgery Assisting Apparatus) 
       FIG. 1  is a view showing a functional configuration example of a surgery system including a surgery assisting apparatus according to an embodiment. 
     This surgery system includes a medical instrument  1 , a medical instrument driving unit  2 , a mantle tube (trocar)  4 , an optical part holder  5 , a hollow tube  6 , a hollow tube driving unit  7 , a distance measuring unit  8 , and a controller  9 . Of these components, the surgery assisting apparatus according to this embodiment includes the optical part holder  5 , the hollow tube  6 , the hollow tube driving unit  7 , the distance measuring unit  8 , and the controller  9 . 
     The medical instrument  1  includes forceps, tweezers, an electric knife, a suction tube, an ultrasonic scalpel, a hemostatic device, a radiofrequency ablation device, an endoscope, a thoracoscope, and a laparoscope, all of which are inserted into the body cavity and used, and is an arbitrary instrument having a straight shaft  10  which can be inserted into the body cavity through the hollow tube  6 . Also, the distal end of the medical instrument  1  can have a degree of freedom of bending, and a device for driving this bending portion can be included in the medical instrument or medical instrument driving unit. 
     The medical instrument driving unit  2  includes a driving unit for manipulating the position/posture of the medical instrument  1  from outside the body, and is configured so as to be able to control the position/posture of the medical instrument by at least two degrees of freedom. First, the medical instrument driving unit  2  can change the insertion angle of the medical instrument  1  with respect to the contact point between the mantle tube  4  and a body wall  3  (that is, a hole in the body wall  3 ). Also, the medical instrument driving unit  2  includes a rail  11  which is drivable parallel to the shaft  10  of the medical instrument, and can move the medical instrument  1  in the major-axis direction of the shaft  10 . The mechanism of the driving unit can be a known mechanism, for example, a mechanism using an R guide, a mechanism using parallel links, or a mechanism using a vertical articulated arm, and is not limited to the mechanism shown in  FIG. 1 . Any of these driving units includes a plurality of positioning actuators such as servo motors, and current position information such as joint angles of the mechanism can be obtained from encoders included in the actuators. Accordingly, the distal end position of the medical instrument  1  can be known on the coordinate system of the medical instrument driving unit  2 . 
     The mantle tube  4  has a hollow structure for inserting the medical instrument  1  or the like into it, and is inserted into a hole formed in the body wall  3  when in use. The mantle tube  4  according to this embodiment is configured so as to be connectable to the end portion, on the side of the body wall  3 , of the rail  11  of the medical instrument driving unit  2 . However, the mantle tube  4  can also be equivalent to a mantle tube used in ordinary laparoscopic surgery, provided that it is connectable to the medical instrument driving unit  2 . Also, the inner diameter of this mantle tube is larger than the outer shape of the hollow tube  6  (to be described below) in order to insert the hollow tube  6 . 
     In the vicinity of its distal end portion, the hollow tube  6  has the optical part holder  5  which can project outside the hollow tube  6 , and is configured so as to be insertable into the mantle tube  4 . Details of the configuration examples of the hollow tube  6  and optical part holder  5  will be explained with reference to  FIG. 2 . A hole having a predetermined size is formed in the circumferential surface close to the distal end portion of the hollow tube  6 , and a portion of the optical part holder  5  is projectable outside the outer shape of the hollow tube  6  through the hole ( 2   a  in  FIG. 2 ). Also, as indicated by  2   b  in  FIG. 2 , optical parts  21  and  22  for optical distance measurement are arranged in that portion of the optical part holder  5 , which projects outside the outer shape of the hollow tube  6 . These optical parts can include only optical fibers in order to reduce the weights or simplify the structures. Alternatively, each optical part can include one or more optical parts such as a lens, a diffraction grating, a mirror, a filter, a wavelength plate, a generation source (laser or LED), and a light-receiving portion (photodiode) in addition to the optical fiber, so as to improve the functionality implementable in the optical part holder  5 . 
     With reference to  2   a  in  FIG. 2  again, at least the root of the optical part holder  5  has a shape having a smooth inclined surface  23 . The optical part holder  5  can also include a connecting portion  26  as a portion to be connected to the distance measuring unit  8 . The connecting portion  26  is formed by an optical fiber or a cable for exchanging electrical signals, in accordance with the configuration of the optical part holder  5 . The optical part holder  5  includes a stopper  24  for preventing projection more than necessary from the hollow tube  6 . The optical part holder  5  is fixed to the hollow tube  6  by an elastic body  25 . When no external force is applied to the optical part holder  5  from outside the hollow tube  6 , the restoring force of the elastic body  25  causes the optical parts  21  and  22  of the optical part holder  5  to project from the outer diameter of the hollow tube  6 . On the other hand, as indicated by  2   c  in  FIG. 2 , when an external force which pushes the optical part holder  5  into the hollow tube  6  is applied, the optical part holder  5  is accommodated in the hollow tube  6 , and enters inside the outer diameter of the hollow tube  6 . That is, as indicated by  2   d  in  FIG. 2 , the optical parts  21  and  22  of the optical part holder  5  are accommodated in the hollow tube  6 . 
     When inserting the hollow tube  6  into the mantle tube  4 , the user of the surgery assisting system pushes the optical part holder  5  into the hollow tube  6  as indicated by  2   c  or  2   d  in  FIG. 2 , and inserts the hollow tube  6  into the mantle tube  4 . While the optical part holder  5  is passing inside the mantle tube  4 , an external force from the mantle tube  4  acts on the optical part holder  5 , so the optical part holder  5  maintains the state of  2   c  or  2   d  in  FIG. 2 . When the optical part holder  5  has passed through the mantle tube  4 , the restoring force of the elastic body  25  causes the optical parts  21  and  22  to project outside the outer diameter of the hollow tube (that is,  2   a  or  2   b ). In this state, at least a space in which the shaft  10  of the medical instrument  1  can pass is secured in the hollow tube  6 , so the shaft  10  of the medical instrument  1  can be inserted into the body cavity through the hollow tube  6 . When the shaft  10  of the medical instrument  1  is inserted into the hollow tube  6 , the optical part holder  5  projects outside the hollow tube  6  and is fixed in this state, thereby preventing fluctuations in positions of the optical parts  21  and  22  during distance measurement. 
     On the other hand, when removing the medical instrument  1 , the medical instrument  1  is first pulled out from the hollow tube  6 , and the hollow tube  6  is pulled out from the mantle tube  4 . Since the shape of the root of the optical part holder  5  has the inclined surface  23  including a smooth inclined portion, the optical part holder  5  is pushed by the distal end portion of the mantle tube  4  and automatically accommodated in the hollow tube  6  (without a touch on the optical part holder  5  by the user). That is, when the optical part holder  5  comes in contact with the end portion of the mantle tube  4  when the hollow tube  6  is pulled out from the mantle tube  4 , the inclined surface  23  generates a force of accommodating the optical part holder  5  in the cylindrical portion of the hollow tube  6 . Note that the optical part installation surface of the optical part holder  5  and the top of the optical part holder  5  form a corner in the above-described example, but a smooth inclined surface may also be formed. This facilitates insertion of the hollow tube  6 , and can also reduce the influence when the optical part holder  5  touches an organ or the like in the body cavity. 
     In this embodiment as described above, the optical parts  21  and  22  projecting from the circumferential surface of the hollow tube  6  perform distance measurement. This makes it possible to sense approach of not only the distal end of the medical instrument  1  but also a part of the shaft  10  to an object in the body cavity. In addition, the optical part holder  5  is accommodated in the hollow tube  6  when the hollow tube  6  is inserted into the mantle tube  4 , and projected outside the hollow tube  6  when the hollow tube  6  has passed through the mantle tube  4 . When inserting the optical part into the body cavity, therefore, it is unnecessary to form a new hole in the abdominal wall or enlarge the hole in the abdominal wall, and this can reduce the burden on the patient. Furthermore, the shape of the optical part holder  5  has the inclined surface  23 . This obviates the need for a mechanism of electrical control or the like for accommodating the optical part holder  5  in the hollow tube  6 , and makes it possible to simplify the structure of the hollow tube  6  and secure a wider space in the hollow tube  6 . 
     Note that in the example indicated by  2   a  and  2   c  in  FIG. 2 , the hole for projecting the optical part holder  5  is formed in the circumferential surface of the hollow tube  6 . This can prevent a liquid or the like sticking to the shaft  10  from directly sticking to the optical part holder  5  when the medical instrument  1  moves in the removing direction. On the other hand, instead of forming the hole, it is also possible to make a cut extending from the end face of the hollow tube  6 , or form the optical part holder  5  at the distal end of the hollow tube  6 . 
     As shown in  FIG. 3 , the hollow tube  6  is fixed to a support portion of the rail  11  of the medical instrument driving unit  2  in a state in which the hollow portion  6  has only a degree of freedom of rotation around the major axis. As a method of fixing the hollow tube  6 , a bearing structure using a general bearing or the like can be used. The major-axis direction of the hollow tube  6  is parallel to the major-axis direction of the shaft  10  of the medical instrument  1  and to the direction of the rail  11  of the medical instrument driving unit  2 . This allows the shaft  10  of the medical instrument  1  to freely move forward and backward in the hollow tube  6 . 
     The hollow tube driving unit  7  includes a driving unit for rotating the hollow tube  6  around the axis, and is fixed to the support portion of the rail  11  of the medical instrument driving unit  2 . The hollow tube driving unit  7  has a driving mechanism  31  capable of rotating the support portion of the rail  11  and the hollow tube  6  relative to each other. As the driving mechanism  31 , it is possible to use general torque transmitting mechanisms such as a gear, a belt pulley, and a friction wheel, and examples are not limited to them. An attaching/detaching mechanism  32  detachably fixes the mantle tube  4  and the support portion of the rail  11 , thereby restricting at least movement in the major-axis direction. The attaching/detaching mechanism  32  need only be a mechanism capable of temporary fixation in the major-axis direction, such as a fitting mechanism, a magnet, or an adhesive material, and can have any structure. 
     As shown in  FIG. 4 , the hollow tube driving unit  7  may also be included in a detachable hollow tube  41 . In this case, the hollow tube driving unit  7  and driving mechanism  31  are integrally detached from the support portion of the rail  11 . Attaching/detaching mechanisms  42   a  and  42   b  of the hollow tube  41  fix the hollow tube  41  so as to restrict rotation around the major axis and movement in the major-axis direction of the hollow tube  41  with respect to the support portion of the rail  11 . Like the attaching/detaching mechanism  32  of the mantle tube  4 , each of the attaching/detaching mechanisms  42   a  and  42   b  can be formed by a fitting mechanism, a magnet, an adhesive material, or the like. By thus making the hollow tube  41  detachable, it is possible to reduce the complicatedness when installing the surgery assisting apparatus or surgery assisting system. 
     The distal end shape of the mantle tube  4  can be a known shape used in ordinary laparoscopic surgery, or a shape including a balloon  51  surrounding the optical part holder  5  shown in  FIG. 5 . The use of the balloon  51  makes it possible to prevent a body fluid dropping from the root of the mantle tube  4  from sticking to the optical part holder  5 . Accordingly, it is possible to prevent a decrease in distance measurement accuracy caused by a liquid or the like sticking to the optical part holder  5 . 
     The distance measuring unit  8  implements a distance measuring unit configured to measure the distance to an object in the body cavity by emitted light, together with the optical parts  21  and  22  arranged in the optical part holder. To implement this function, it is possible to use the principles of known optical range finders, such as a method of estimating a distance by measuring the time required for light to go and return, a method of estimating a distance by using the interference of light, a method of estimating a distance by the intensity of reflected light, and a method of estimating a distance by triangulation. Generally, a method of measuring the distance to an object in the body cavity by using emitted light can perform distance measurement simpler and stabler than that performed by a method using a stereoscopic image. 
     In the example shown in  FIG. 1 , the distance measuring unit  8  includes a measuring unit accommodating a light generation source, a light-receiving portion, and an arithmetic chip for estimating the distance, and this measuring unit is connected to the optical parts  21  and  22  (that is, there is a distance between the optical part holder  5  and distance measuring unit  8 ). The measuring unit can include one or more optical parts such as a lens, a diffraction grating, a mirror, a filter, a wavelength plate, generation source (laser or LED), and a light-receiving portion (photodiode) in accordance with the members included in the optical part holder  5 . Instead of the above-described example, the measuring unit can be incorporated into the periphery of the medical instrument driving unit  2  or hollow tube driving unit  7 , and can also be incorporated into the optical part holder  5 . 
     The optical part  22  on the exit side of the optical part holder  5  has a function of collimating light, so an object is irradiated with spot light. The spot diameter on the object is equivalent to the diameter of the shaft of a medical instrument to be inserted, and is  20  mm or less. The optical part  21  on the light-receiving side of the optical part holder  5  receives the reflected light of light emitted from the optical part  22 . As shown in  FIG. 6 , an optical axis  61  of the optical part  21  on the light-receiving side is slightly inclined toward the optical part  22  on the exit side, and so adjusted as to be able of efficiently obtain the reflected light of light emitted on an object. Note that in  FIG. 6 , the dotted lines indicate the optical axes of the optical parts, and the solid lines indicate the exit range of the optical part  22  and the light-receiving range of the optical part  21 . Note that the optical part  22  on the light exit side is basically parallel to the major-axis direction of the shaft  10  of the medical instrument  1 , but can also have an angle at which the optical part  22  separates from the major-axis direction of the shaft. In this case, the optical axis  61  on the light-receiving side similarly has an angle at which the optical axis  61  separates from the shaft. 
     Since the hollow tube  6  can be rotated by the above-described hollow tube driving unit  7 , the distance measurement range extends to the region of a cylindrical shape or conical shape surrounding the shaft  10  of the medical instrument  1 , in addition to the distance measurement range when the optical part holder  5  is standing still. In this embodiment, the origin of distance measurement is the position of the optical part  22 . However, the present invention is not limited to this, and the origin of distance measurement can be an arbitrary position as long as the relative positions of the optical part  22  and medical instrument driving unit  2  are fixed. 
     The controller  9  includes a central arithmetic device such as a CPU or MPU, a ROM, and a RAM, and executes software stored in the ROM or a recording medium (not shown), thereby controlling an object sensing process (to be described later). The controller  9  is connected to the medical instrument driving unit  2 , the hollow tube driving unit  7 , and the distance measuring unit  8 . For example, the controller  9  obtains current position information for specifying the distal end position of the medical instrument, rotation information for specifying the rotation of the hollow tube  6 , and distance information for specifying the distance of the distance measuring unit  8 , from the joint angles of the medical instrument driving unit  2  and the position of the rail  11 , and performs an arithmetic operation. Also, based on the result of this arithmetic operation, the controller  9  transmits control information for controlling these units. Furthermore, the controller  9  is connected to an output unit (not shown) including a liquid crystal panel, a speaker, or a vibrating member, and outputs sounds, images, characters, or vibrations to the user as needed. 
     (Series of Operations According to Object Sensing Process) 
     Next, a series of operations according to the object sensing process of the surgery assisting apparatus according to this embodiment will be explained with reference to  FIGS. 7 and 8 . This process is started when, for example, the controller  9  has received an instruction to move the distal end of the shaft  10  of the medical instrument  1 . Note that the controller  9  implements this process by controlling each unit by executing a program stored in the ROM. 
     In step S 1 , the controller  9  determines the advancing direction of the medical instrument  1 . More specifically, when moving the medical instrument  1  in the body cavity by the medical instrument driving unit  2 , as shown in the left view of  FIG. 7 , the advancing direction of the distal end of the medical instrument  1  can be represented by a three-dimensional vector extending from the distal end of the medical instrument  1 . For example, the controller  9  first specifies the distal end position of the shaft  10  of the medical instrument  1  based on the current position information obtained from the medical instrument driving unit  2 . More specifically, assume an orthogonal coordinate system O s  having an arbitrary axis parallel to the shaft  10  of the medical instrument  1 . Two remaining axes can freely be determined as long as mutual conversion from the coordinate system of the medical instrument driving unit  2  is possible. For example, when a command angle from the hollow tube driving unit  7  is 0°, it is possible to select a vector parallel to the direction from the shaft  10  of the medical instrument  1  to the optical part, and define the orthogonal coordinate system O s  by using the vector. For the sake of simplicity, assume that the Z-axis is the direction of the shaft  10  of the medical instrument  1 , and the X-axis is the direction when the command angle from the hollow tube driving unit  7  is 0°. Assume also that the optical axes for distance measurement intersect each other on the X-axis when the command angle of the hollow tube driving unit  7  is 0°. Note that the coordinate system determination method is not limited to the above method as long as mutual conversion to the coordinate system of the medical instrument driving unit  2  is possible. 
     The distal end position of the shaft  10  of the medical instrument  1  is known from the current position information obtained from the medical instrument driving unit  2 , and the hollow tube  6  is fixed to the rail  11  of the medical instrument driving unit  2 . Therefore, the controller  9  can specify the distal end position and three-dimensional vector of the shaft  10  in relation to the origin of distance measurement (the position of the optical part  22 ) fixed to the hollow tube  6 . Likewise, the controller  9  can also specify the distal end position of the shaft  10  to be moved at the next time. The coordinates of these distal end positions are represented by: 
         P   k =( x   k   ,y   k   ,z   k ) 
         P   k+1 =( x   k+1   ,y   k+1   ,z   k+1 ) 
     By using these distal end positions, the controller  9  obtains a vector V m  extending from a point at a given time to a point at the next time. That is, this vector is represented by: 
     
       
      
       {right arrow over (v)} 
       m 
       =P 
       k+1 
       −P 
       k  
      
     
     The controller  9  thus calculates a three-dimensional vector representing the advancing direction of the distal end position of the shaft  10  of the medical instrument  1 , based on an instruction to move the distal end of the shaft  10  to a predetermined position (the controller  9  may also set this predetermined position). 
     In step S 2 , the controller  9  rotates the hollow tube  6  by controlling the hollow tube driving unit  7 , such that a distance measurement spot as a distance measurement sensing range  72  exists in the moving direction of the distal end of the shaft  10 . This is equivalent to rotating the hollow tube  6  such that a direction obtained by projecting a three-dimensional vector  71  onto a plane perpendicular to the major axis of the hollow tube  6  matches a direction from the major axis of the hollow tube  6  to the optical part  22 . More specifically, based on the three-dimensional vector  71 , the controller  9  rotates the hollow tube  6  by driving the hollow tube driving unit  7 , so that the three-dimensional vector  71  and the distance measurement sensing range  72  (that is, the optical axis on the exit side) intersect each other (the right view in  FIG. 7 ). For example, the above-described vector V m  is projected onto an XY plane of the orthogonal coordinate system O s . That is, it is only necessary to calculate the inner product of basic vectors representing the X-axis and Y-axis as follows: 
         {right arrow over (v)}   mp =( {right arrow over (v)}   m   ·{right arrow over (i)}   s   ,{right arrow over (v)}   m   ·{right arrow over (j)}   s ) 
     where vectors i s  and j s  are the basic vectors representing the X-axis and Y-axis of the orthogonal coordinate system O s . The advancing direction of the distal end position of the shaft  10  of the medical instrument  1  is represented by a vector V mp  on the XY plane of the orthogonal coordinate system O s , and hence can be represented as an angle θ to the X-axis by assuming a polar coordinate system around the Z-axis. As described above, the X-axis is the direction in which the command angle of the hollow tube driving unit is 0°. Therefore, the optical axis for distance measurement and the three-dimensional vector representing the advancing direction can be crossed by directly inputting the angle θ as the command angle of the hollow tube driving unit  7 . Consequently, the optical part holder  5  faces the space in which the distal end of the shaft  10  of the medical instrument  1  moves, and the distance measurement sensing range  72  exists in this space. Note that another method may also be used if it is possible to rotate the hollow tube  6  so that the distance measurement sensing range  72  exists in the advancing direction of the distal end position of the shaft  10 . 
     In step S 3 , the controller  9  instructs the distance measuring unit  8  to measure the distance while moving the distal end position of the shaft  10  of the medical instrument  1  in the advancing direction. 
     In step S 4 , the controller  9  determines whether the medical instrument  1  has approached an object in the body cavity by taking account of the distance obtained from the distance measuring unit  8  and the distal end position of the shaft  10  of the medical instrument  1 . More specifically, the controller  9  determines whether the distance measured by the distance measuring unit  8  is shorter than a predetermined threshold. If the measured distance is shorter than the predetermined threshold, the controller  9  determines that the object is sensed, and advances the process to step S 5 . As the predetermined threshold, it is possible to use, for example, a value obtained by adding a predetermined margin to the distance from the intersection of a perpendicular line, which is drawn from the origin of distance measurement to the major axis of the shaft  10 , to the distal end position of the shaft  10 . By thus moving the optical part holder  5  in the advancing direction of the distal end position of the shaft  10 , it is possible to sense approach of the shaft  10  (including the distal end position) of the medical instrument to the object. This makes it possible to accurately sense approach of the medical instrument inserted into the body cavity to the object in the body cavity. On the other hand, if the measured distance is equal to or larger than the predetermined threshold, no object is sensed. Accordingly, the controller  9  returns the process to step S 3  in order to continue the distance measurement. 
     In step S 5 , the controller  9  performs notification to the user. In this notification to the user, the controller  9  causes the output unit (not shown) to output information indicating the existence of the object in the body cavity by, for example, a sound, light, or a vibration. 
     In step S 6 , the controller  9  takes evasive action by controlling the movement of the distal end position of the shaft  10  of the medical instrument  1 . As this evasive action, the controller  9  can execute one of, for example, stopping the movement at once, pulling out the medical instrument  1  from the body so as to obtain a sufficient distance from the object position, and changing the advancing direction to a direction in which no object exists. It is also possible to perform one of the notification to the user in step S 5  and the evasive action in step S 6 . When performing the both, the notification to the user may also be performed after the evasive action. After that, the controller  9  terminates the series of operations. 
     In this embodiment as explained above, the optical part holder  5  in which the optical part  22  included in the distance measuring unit  8  is placed can be accommodated in the hollow tube  6 , and the optical part  22  of the optical part holder  5  projects outside the hollow tube  6  when a part of the hollow tube  6  is inserted into the body cavity. Also, approach of the shaft  10  (including the distal end position) of the medical instrument  1  to an object is sensed by rotating the optical part  22  in the advancing direction of the distal end position of the shaft  10  of the medical instrument  1 . This makes it possible to accurately sense approach of the medical instrument inserted into the body cavity to an object in the body cavity. 
     Note that the present invention is not limited to the above-described embodiment, and can include other embodiments without departing from the spirit and scope of the invention. 
     Other Embodiments 
     For example, an example using optical distance measurement as the optical parts  21  and  22  has been explained in the above-described embodiment. However, a stereoscopic camera may also be formed by using a camera as each of the optical parts  21  and  22 . Alternatively, it is also possible to use both optical distance measurement and a stereoscopic camera. When performing three-dimensional measurement in the body cavity by using the stereoscopic camera, optical distance measurement can be used if the accuracy of feature point extraction decreases and this decreases the accuracy of distance measurement. 
     In the above-described embodiment, an example in which distance measurement is performed by projecting the optical parts of the optical part holder  5  from the circumferential surface of the hollow tube  6  has been explained. However, it is also possible to form a gap between the hollow tube  6  and the section of the medical instrument  1  by increasing the diameter of the hollow tube  6 , and perform distance measurement by arranging the optical parts  21  and  22  in this gap. That is, it is also possible to perform distance measurement around the medical instrument  1  by arranging the optical parts inside the circumferential surface of the hollow tube  6 . 
     In the above-described embodiment, an example in which the pair of optical parts  21  and  22  are projected from the circumferential surface of the hollow tube  6  and the hollow tube  6  is rotated in accordance with the movement of the medical instrument  1  has been explained. However, it is also possible to arrange a plurality of pairs (for example, four or eight pairs) of optical parts outside (or inside) the hollow tube  6  along the outer circumference, and select a pair of optical parts for performing distance measurement in accordance with the movement of the medical instrument  1 . Distance measurement in the advancing direction of the medical instrument inserted into the body cavity can be performed in this case as well. 
     The surgery assisting apparatus according to this embodiment has been explained by taking, as an example, the case in which the apparatus includes the optical part holder  5 , the hollow tube  6 , the hollow tube driving unit  7 , the distance measuring unit  8 , and the controller  9 . However, the surgery assisting apparatus can further include an arbitrary component included in the surgery assisting system in addition to these components. In the above-described embodiment, an example in which the optical parts of the optical part holder  5  are projected from the hollow tube  6  by the elastic body  25  of the hollow tube  6  has been explained. However, the optical parts of the optical part holder  5  may also be projected from the hollow tube  6  in accordance with the insertion of the medical instrument  1  into the hollow tube  6  without using any elastic body. 
     Furthermore, the components of the above-described surgery assisting system may also be implemented as separated components or an integrated component. In addition to the case in which the controller reads out a program of a computer for executing the above-described processing from the storage medium and executes the program, the present invention can include a case in which the program is obtained by wired communication or wireless communication and executed. 
     In the above-described embodiment, an example in which the optical parts accommodated in the optical part holder  5  are the pair of the optical part  21  on the light-receiving side and the optical part  22  on the exit side has been explained. However, the above-described optical part holder  5  may also include a plurality of optical parts on one of the exit side and light-receiving side, instead of including one optical part on each side. 
     For example, the optical part holder  5  includes one optical part  21  on the light-receiving side, and a plurality of optical parts  22  on the exit side. In this configuration, the optical axes of the plurality of exit-side optical parts  22  incline to each other (are not parallel), and point in different directions. Furthermore, each of the optical axes of the plurality of exit-side optical parts  22  may point in a direction different from that of the optical axis of the light-receiving-side optical part  21 . 
     When the optical part holder includes the plurality of exit-side optical parts  22 , for example, the distance measuring unit  8  switches (selects) every predetermined time interval the optical parts  22  for emitting light of the plurality of exit-side optical parts  22 , thereby sequentially emitting exit light in a plurality of directions. The distance measuring unit  8  may also be able to switch the optical parts  22  for emitting light in accordance with the advancing direction of the distal end position of the shaft  10  of the medical instrument  1  or the rotating direction of the hollow tube  6 , thereby measuring the distance to a region closer to the advancing direction or rotating direction. By measuring the distance by switching the directions of exit light, it is possible to sense obstacles in a broader range without moving the optical part itself The distance measuring unit  8  includes a plurality of light sources such as laser diodes, and switches the optical parts  22  for emitting light by electrically switching the light sources for generating light. The optical parts  22  for emitting light may also be switched by using one light source such as a laser diode, and a mechanism such as an optical switch for switching optical paths between the light source and the plurality of optical parts  22 . 
     On the other hand, the optical part holder  5  may also include one exit-side optical part  22 , and a plurality of light-receiving-side optical parts  21 . The plurality of light-receiving-side optical parts  21  make distance measurement at higher sensitivity possible. More specifically, a region where the emitted light beam and the light beam to be received do not intersect each other and the sensitivity extremely decreases exists near the light-receiving-side optical part  21  and light-emitting-side optical part  22  shown in  FIG. 6 . Contrary to this, a new optical fiber is placed as the light-receiving-side optical part  21  near the light-receiving-side optical part  21  and light-emitting-side optical part  22 . For example, as shown in  FIG. 9 , a new light-receiving-side optical part (optical fiber  92 ) is placed between the light-receiving-side optical part  21  and light-emitting-side optical part  22 , thereby forming a new measurement region  91 . Note that optical fibers  93  and  94  respectively represent a fiber for transmitting light from the light-receiving-side optical part  21 , and a fiber for transmitting light to the exit-side optical part  22 . As described above, however, the optical parts  21  and  22  may also simply be formed by the distal ends of the optical fibers  93  and  94 . By thus further placing the light-receiving-side optical part (optical fiber  92 ) near the optical parts, it is possible to broaden the measurement region and further stabilize measurement. Note that it is desirable to use an optical fiber having as large a numerical aperture (NA) as possible as the optical fiber  92 . In the example shown in  FIG. 9 , the NA of the optical fiber  92  is larger than that of the other light-receiving optical fiber. Note that when a light-receiving-side optical part is added, the distance measuring unit  8  sometimes requires a new light-receiving part. However, the distance measuring unit  8  may also use only one light-receiving part together with the prepared light-receiving-side optical fiber  93 . 
     In the above-described embodiment, an example in which the optical parts of the optical part holder  5  are exposed in the body cavity has been explained. Since the optical part holder  5  is used in the body cavity, a substance (a sticking substance  1002 ) in the body cavity such as a blood may stick to the optical part and cause a detection error of the distance. To prevent this, as shown in  FIG. 10 , the optical parts  21  and  22  can be sealed by setting a glass plate  1001  in front of the optical parts  21  and  22 , so that a body fluid and the like do not touch the optical parts. In this case, the optical parts  21  and  22  can be arranged in positions retracted by a predetermined distance L from the distal end of that portion of the optical part holder  5 , which projects from the hollow tube  6 . The distance L is equal to or longer than a shortest distance measurable by the optical parts  21  and  22 . When the optical part holder  5  is thus configured, if a substance sticks to the surface of the glass plate  1001 , this sticking substance is sensed as an obstacle at the distance L, and this makes stain sensing possible. 
     If the controller  9  determines that a stain is sensed because the distance obtained from the distance measuring unit  8  is the distance L, the controller  9  notifies the user that the stain is sensed. In addition to this notification, the controller  9  can further encourage the user to perform cleaning, and can also automatically perform a process of cleaning the optical part holder  5 . As a method of automatically cleaning the optical part holder  5 , it is possible to use a known method of cleaning the glass plate  1001  by spraying a gas or liquid from an additionally prepared nozzle placed near the glass plate  1001 . 
     The present invention is not limited to the above-described embodiments, and various changes and modifications can be made within the spirit and scope of the present invention. Therefore, to apprise the public of the scope of the present invention, the following claims are made.