Patent Publication Number: US-2010125165-A1

Title: Endoscope system and assist device

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to an endoscope system and an assist device. More particularly, the present invention relates to an endoscope system in which a nasal type of an endoscope is used for medical treatment, and an assist device for use in combination with the nasal endoscope. 
     2. Description Related to the Prior Art 
     A nasal endoscope is known in the field of medical instruments, and has an elongated tube with a smaller diameter than that of an oral endoscope. Examples of the nasal endoscope are disclosed in JP-A 2006-068030 and 2007-061377. There are several advantages of examination with the nasal endoscope over the oral endoscope. The nasal endoscope does not contact a tongue root of a patient or a surface of his or her throat, and can reduce physical stress of the patient because his or her nausea and strange feeling can be reduced. Anesthetic drug for use can be a smaller amount than in the oral endoscope. Also, the patient can talk with a doctor or other staff even during the examination. The patient is enabled to breathe orally. 
     In the same manner as the oral endoscope, the nasal endoscope includes imaging optics and lighting optics incorporated in a distal portion or head assembly of the elongated tube for entry in the patient&#39;s body. An object in the body is illuminated by the lighting optics. An image of an object is picked up through the imaging optics, to produce an image signal. A display panel is driven to display the image. Various elements are contained in the elongated tube its tube lumen extending from the distal portion to a proximal portion, including an instrument channel (operable also as a suction channel), air/water supply channel, light guide optics and the like. 
     The light guide optics include an entrance end and an exit end for entry and exit of light, and guide light from the light source apparatus to the distal portion. The light from the exit end is passed through a lens, and is applied to an object through a lighting window formed in a distal end surface in the distal portion. A distal opening is a first end of the instrument channel and open in the distal end surface. A proximal opening is a second of the instrument channel and open is a proximal portion. A treatment instrument such as forceps device or other medical instrument is inserted in the instrument channel through the proximal opening, and guided toward the distal opening. 
     The endoscope of a nasal type is characterized in having higher flexibility of the elongated tube than the oral endoscope for the purpose of passage in a tortuous path from an external nostril to a middle or lower nasal tract. A diameter of the elongated tube is as small as 5-6 mm in contrast with that of the elongated tube of the oral endoscope (approximately 9 mm). The kinds and number of the treatment instrument or medical instruments that can enter the instrument channel may be restricted, because the diameter of the bore of the instrument channel in the elongated tube, which is as small as approximately 2 mm. There are problems in difficulties in the treatment, for example, cutting of polyp (polypectomy and mucosectomy) in a stomach or esophagus, tissue clamping (hemostasis) of bleeding tissue of a body part by use of medical clips, with a gastric ulcer of the like. 
     To solve such problems, a combined of use of an assist device is conceivable in combination with the endoscope. The assist device has the elongated tube of which a diameter is equal to or smaller than that of the endoscope. The assist device has the instrument channel contained in the elongated tube and having a greater bore than that of the instrument channel. For example, the elongated tube of the assist device is entered through a second nostril, and used in combination with the endoscope. This is for the purpose of providing an additional function to the endoscope. 
     A problem arises in the combined use of the endoscope with the assist device. Operability of the assist device is not good, as the distal portions of the elongated tubes which should be manipulated are discretely entered in the body. For the medical treatment by their combined use, it is conceivable to retain the distal portions of the elongated tubes on one another within a body cavity of the patient after discrete initial entry of the elongated tubes through the external nostrils, particularly in an area of the body cavity from the lower nasal tract to the esophagus. 
     If the assist device is fixed in relation to the endoscope in an improper position, problems may occur. For example, a shadow may occur in an image of an object with the treatment instrument advanced through the instrument channel of the assist device. Also, white smear may occur in the image with light improperly reflected by the treatment instrument in an illuminating condition. 
     SUMMARY OF THE INVENTION 
     In view of the foregoing problems, an object of the present invention is to provide an endoscope system in which a nasal type of an endoscope is used for medical treatment and in which an assist device can be positioned suitably, and the assist device for use in combination with the nasal endoscope. 
     In order to achieve the above and other objects and advantages of this invention, an endoscope system has an endoscope including a first elongated tube, having a first distal portion, for entry in a first external nostril, an imaging window formed in a first distal end surface of the first distal portion, a first instrument channel, contained in the first elongated tube, for extending from the first distal portion toward a proximal portion, a handle section connected with the proximal portion, and a steering section for steering the first distal portion at least in an upward or downward direction upon steering operation of a steering mechanism disposed in the handle section. In the endoscope system, there is an assist device including a second elongated tube, having a second distal portion, for entry in a second external nostril, and a second instrument channel, defined in the second elongated tube, for extending from a second distal end surface of the second distal portion in a proximal direction, the second instrument channel having a greater inner diameter than the first instrument channel. A retaining device retains the second distal portion on the first distal portion removably to orient the first and second distal end surfaces in an equal direction, to cause the second distal end surface to contact a lower peripheral part outside the first distal end surface lower than a horizontal line passing a center point of the imaging window when the first distal end surface is viewed in a state of orienting an upper side of steering of the steering section in the upward direction. 
     The imaging window is positioned eccentrically with reference to a center point of the first distal end surface. The retaining device retains the assist device in a peripheral part positioned outside the first distal end surface and offset from the imaging window with reference to the center point. 
     Furthermore, a lighting window is formed in the first distal end surface. First and second peripheral areas are defined around the first distal end surface and split by a straight line which is perpendicular to a straight line passing center points of the imaging window and the first distal end surface and is tangential to a circumference of the imaging window, and the retaining device retains the assist device in one of the first and second peripheral areas offset from the imaging window. 
     The endoscope further includes a proximal opening positioned at a proximal end of the first instrument channel for passing a medical instrument. The assist device further includes an additional proximal opening positioned at a proximal end of the second instrument channel. An engaging portion covers the proximal opening, and retaining a proximal portion of the second elongated tube on the proximal portion of the first elongated tube to orient the additional proximal opening in an outward direction. 
     Furthermore, a suction line is provided by branching off the first instrument channel short of the proximal opening, for suction of fluid from a body cavity. A bypass line is provided by branching off the second instrument channel short of the additional proximal opening, for connecting the proximal opening with the additional proximal opening in retention of the engaging portion. 
     The retaining device includes a magnetic component secured to one of the first and second elongated tubes. A magnetically attractable component is secured to a remaining one of the first and second elongated tubes, for attraction on the magnetic component. 
     In one preferred embodiment, the retaining device includes a retention lumen formed through the first elongated tube. A lumen outlet is defined at a distal end of the retention lumen, and formed through a peripheral surface of the first elongated tube and close to the first distal end surface. A pull strip has distal and proximal end portions, the distal end portion being inserted through the retention lumen, the proximal end portion being disposed to extend in a proximal direction from the retention lumen. A retention loop is secured to the distal end portion of the pull strip, disposed to extend through the lumen outlet, for capturing the second elongated tube when the proximal end portion of the pull strip is pulled. 
     In another preferred embodiment, an endoscope system has an endoscope including a first elongated tube, having a first distal portion, for entry in a first external nostril, an image pickup device for picking up an image of an object through an imaging window formed in a first distal end surface of the first distal portion, an instrument channel, contained in the first elongated tube, for extending from the first distal portion toward a proximal portion, a handle section connected with the proximal portion, and a steering section for steering the first distal portion at least in an upward or downward direction upon steering operation of a steering mechanism disposed in the handle section. In the endoscope system, there is an assist device including a second elongated tube, having a second distal portion, for entry in a second external nostril, and a working channel, defined in the second elongated tube, for extending from a second distal end surface of the second distal portion toward a proximal end, the working channel having a greater inner diameter than the instrument channel. A display panel operates according to an image signal of the image picked up by the image pickup device, and displaying the image in a state of orienting an upper side of steering of the steering section in the upward direction. A retaining device retains the second distal portion on the first distal portion removably to orient the first and second distal end surfaces in an equal direction, to cause the display panel to display an image of a medical instrument through the working channel in a partial area lower than a center point of a display area thereof. 
     In one preferred embodiment, an endoscope system has an endoscope including a first elongated tube, having a first distal portion, for entry in a first external nostril, an imaging window formed in a first distal end surface of the first distal portion, a first lighting window, formed in the first distal end surface, for illumination in a body cavity, and an instrument channel, contained in the first elongated tube, for extending toward a distal opening formed in the first distal end surface. In the endoscope system, there is an assist device, combined with the endoscope, including a second elongated tube, having a second distal portion, for entry in a second external nostril, and a second lighting window, formed in a second distal end surface of the second distal portion, for illuminating additionally to light from the first lighting window. A retaining device retains the second distal portion on the first distal portion removably to orient the first and second distal end surfaces in an equal direction, to cause a peripheral part of the second distal end surface to contact on a peripheral part of the first distal end surface positioned opposite to the first lighting window with reference to the distal opening. 
     Furthermore, lighting optics are disposed inside the second lighting window, and have a distribution characteristic in which a light flux thereof passes off from an axis of a movable range of a medical instrument passing the proximal opening. 
     The first lighting window is constituted by two lighting windows between which the imaging window is positioned. The retaining device retains the second distal portion on the first distal portion with a mounting surface, and the distal opening is positioned between one of the two lighting windows and the mounting surface. 
     The assist device further includes a longitudinal receiving surface, formed concavely in an outer wall of the second elongated tube, for partially receiving an outer wall of the first elongated tube upon retention of the first and second distal portions with the retaining device. 
     The retaining device positions the second lighting window on a straight line which passes through center points of the first lighting window and the distal opening. 
     The second lighting window is constituted by a diffusion lighting window for emitting light with a great illumination angle. A spot lighting window emits light with a smaller illumination angle than the great illumination angle. 
     The spot lighting window is offset from a straight line passing through center points of the first lighting window and the distal opening. 
     In still another preferred embodiment, the spot lighting window is disposed nearer to the first distal end surface than the diffusion lighting window. 
     At least one of the spot lighting window and the diffusion lighting window is constituted by plural lighting windows. 
     In one preferred embodiment, an assist device is for a combined use with an endoscope including a first elongated tube, having a first distal portion, for entry in a first external nostril, and an imaging window, a first lighting window and an instrument channel formed in a first distal end surface of the first distal portion, the first lighting window emitting light to illuminate an object. The assist device includes a second elongated tube, having a second distal portion, for entry in a second external nostril. A second lighting window is formed in a second distal end surface of the second distal portion, for illuminating additionally to light from the first lighting window. A peripheral part of the second distal end surface is caused to contact on a peripheral part of the first distal end surface positioned opposite to the first lighting window with reference to the instrument channel. 
     Consequently, it is possible in the present invention suitably to position the assist device for use with a nasal type of endoscope for medical treatment. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The above objects and advantages of the present invention will become more apparent from the following detailed description when read in connection with the accompanying drawings, in which: 
         FIG. 1  is a perspective view illustrating one preferred endoscope system including an endoscope and an assist device; 
         FIG. 2  is a cross section illustrating an elongated tube of the endoscope; 
         FIG. 3  is a front elevation illustrating a distal end surface of the elongated tube; 
         FIG. 4  is a vertical section illustrating the inside of a distal portion; 
         FIG. 5  is a cross section illustrating an elongated tube of the assist device; 
         FIG. 6  is a vertical section illustrating the inside of a distal portion of the assist device; 
         FIG. 7  is a front elevation, partially in a section illustrating a first distal end surface and a peripheral part determined for magnetic attraction; 
         FIG. 8  is a cross section illustrating magnets in the distal portion of the assist device; 
         FIG. 9  is a perspective view illustrating a secured state of the distal portions of the endoscope and assist device; 
         FIG. 10  is a front elevation illustrating a specifically preferred peripheral part for magnetic attraction in the secured state of the distal portions; 
         FIG. 11  is a plan illustrating a displayed image of a forceps device; 
         FIG. 12  is a block diagram schematically illustrating connection of various elements in the endoscope system; 
         FIG. 13  is an explanatory view illustrating switching of a flow for air with the air/water supply button; 
         FIG. 14  is an explanatory view illustrating switching of a flow for water with the air/water supply button; 
         FIG. 15  is a perspective view illustrating a suction device with a suction connector; 
         FIG. 16  is a flowchart illustrating endoscopy or treatment by use of the endoscope system; 
         FIG. 17  is a vertical section illustrating a nasal tract and entry of the endoscope or assist device; 
         FIG. 18  is an explanatory view illustrating one preferred endoscope system in which a proximal end of the assist device is free from the endoscope; 
         FIGS. 19 and 19A  are perspective views illustrating another preferred endoscope system having a snare device for the retention; 
         FIG. 20  is a perspective view illustrating one preferred endoscope system in which an assist device operates for lighting; 
         FIG. 21  is a cross section illustrating an elongated tube of the endoscope; 
         FIG. 22  is a front elevation illustrating a distal end surface of the elongated tube; 
         FIG. 23  is a vertical section illustrating the inside of a distal portion; 
         FIG. 24  is a cross section illustrating an elongated tube of the assist device; 
         FIG. 25  is a vertical section illustrating the inside of a distal portion of the assist device; 
         FIG. 26  is a front elevation illustrating the inside of the distal portion of the assist device; 
         FIG. 27  is a perspective view illustrating a secured state of the distal portions of the endoscope and the assist device; 
         FIG. 28  is a plan illustrating a displayed image of a forceps device; 
         FIG. 29  is a perspective view illustrating a relationship between an axis of a moving domain of the forceps device and a light flux; 
         FIG. 30  is a block diagram schematically illustrating circuit elements of the endoscope system; 
         FIG. 31  is a block diagram schematically illustrating mechanically connected elements in the endoscope system; 
         FIG. 32  is a perspective view illustrating a light source apparatus; 
         FIG. 33  is a flowchart illustrating endoscopy and treatment by use of the endoscope system; 
         FIG. 34  is a front elevation illustrating one preferred assist device settable in one of two mounting surfaces; 
         FIG. 35  is a front elevation illustrating another preferred assist device with two lighting windows; 
         FIG. 36  is a vertical section illustrating a distribution characteristic of the two lighting windows; 
         FIG. 37  is a front elevation illustrating one preferred assist device with plural sets of lighting windows. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT(S) OF THE PRESENT INVENTION 
     In  FIG. 1 , an endoscope system  10  includes a nasal endoscope  11 , an assist device  12  or endoscopic catheter, a light source apparatus  13 , a processing apparatus  14  and a display panel  15 . A first elongated tube  16  or insertion tube is included in the endoscope  11 , and used for entry through a first one of nostrils of a patient or person. A grip portion  22   a  extends from the first elongated tube  16 . A handle section  17  is secured to the grip portion  22   a . On the handle section  17 , a universal connector  18  is formed at an end of a universal cable  18   a , and becomes connected with the light source apparatus  13  and the processing apparatus  14 . A tube lumen is formed through the first elongated tube  16  of the endoscope  11 . An instrument channel is contained in the tube lumen. A first end of the instrument channel constitutes a distal opening in a distal portion of the first elongated tube  16 . A second end of the instrument channel constitutes a proximal opening  19  or inlet in the grip portion  22   a . Note that the proximal opening  19  may be formed in the handle section  17 . A handle is constituted by the grip portion  22   a  and the handle section  17 . 
     As is well-known in the art, the first elongated tube  16  of the endoscope  11  includes a first distal portion  20  with a head assembly, a steering section  21  and a flexible tube  22 . Two annular magnets or magnetic components  23  and  24  are disposed at ends of the steering section  21  for combined use with the assist device  12 . Note that the steering section  21  is important additionally to the first distal portion  20  of the first elongated tube  16  of the endoscope  11  of the invention. 
     In the endoscope  11 , the first distal portion  20  includes a rigid tubular structure and relevant devices contained in the tubular structure. The devices include imaging optics, an image pickup device and lighting optics. The universal connector  18  includes a light guide coupler  25  and a video connector  27  or plug. A signal cable  26  extends from the universal connector  18 , and has the video connector  27  disposed at its end. The video connector  27  is connected with the processing apparatus  14 . The light guide coupler  25  is connected with the light source apparatus  13 . 
     A power source circuit is contained in the processing apparatus  14 . Also, an image processor is incorporated in the processing apparatus  14 , and encodes the image to a composite signal or RGB component signal by image processing of the image signal from the image pickup device. The light source apparatus  13  contains a lamp, of which light passes through the handle section  17  and light guide optics (fiber bundle) inside the first elongated tube  16 . The light is guided from the grip portion  22   a  to the distal end, and enters the lighting optics. 
     The flexible tube  22  has flexibility, and extends between the handle section  17  and the steering section  21  with a small diameter. Steering wheels  28  or steering mechanism is disposed on the handle section  17 . Steering wires for steering are contained in a tube lumen in the first elongated tube  16 , and are moved back and forth by rotating the steering wheels  28  for steering. Thus, a distal end surface of the first distal portion  20  is directed in a desired direction in a body cavity to image an object. The object is illuminated by light emitted by the lighting optics. Reflected light from the object is picked up by an image pickup device through imaging optics, for the display panel  15  to display an image by use of an image processing circuit. 
     An air/water supply button  30 , a suction button  31  and a water jet opening  32  are disposed on the handle section  17  in addition to the steering wheels  28  and the proximal opening  19 . To the water jet opening  32 , a syringe, water supply device or the like are connected in a removable manner, the syringe containing washing water, drug solution and other fluid for ejection to an object in the body. In a normal state, the water jet opening  32  and the proximal opening  19  are closed tightly by a seal or lid fitted in a removable manner. 
     The assist device  12  is combined with the endoscope  11 , and includes a second elongated tube  35  or insertion tube and an engaging portion  36 . The second elongated tube  35  is entered through a second nostril which is different from the first nostril of entry of the first elongated tube  16  of the endoscope  11 . The engaging portion  36  is positioned at a proximal end of the second elongated tube  35 , and is engaged with the grip portion  22   a  or the handle section  17  of the endoscope  11  in a removable manner. The second elongated tube  35  of the assist device  12  includes a second distal portion  37 , a steering section  38  and a flexible tube  39  in a sequence in a proximal direction. 
     Annular magnets or magnetic components  40  and  41  are disposed on the steering section  38  of the assist device  12  and arranged in the axial direction of the endoscope. The magnets  40  and  41  magnetically attract the magnets  23  and  24  on the steering section  21  of the endoscope  11  when entered in a range from the internal nostril to the esophagus. Thus, the steering section  38  of the assist device  12  is bent for steering together with the bend of the steering section  21  of the endoscope  11 . A distal end surface of the second distal portion  37  of the assist device  12  is directed equally to the distal end surface of the first distal portion  20  of the endoscope  11 . 
     The second distal portion  37  of the assist device  12  is formed from rigid material. The steering section  38  is a flexible portion bendable together with the steering section  21  of the endoscope  11 . The flexible tube  39  is a long flexible portion with a small diameter, and extends between the engaging portion  36  and the steering section  38 . The steering section  38  is a portion extending from the second distal portion  37  as an important element in the second elongated tube  35  of the assist device  12  of the invention. 
     An instrument channel is formed through the second elongated tube  35  of the assist device  12  to extend from the distal end to the engaging portion  36 . A first end of the instrument channel constitutes a distal opening in the distal end surface of the assist device  12 . A second end of the instrument channel constitutes an additional proximal opening  42  or inlet in the engaging portion  36 . A sealing film  42   a  or channel lid is fitted to close the additional proximal opening  42 . A sealing portion of the sealing film  42   a  has flexibility, includes slits or small pores, and is openable when pushed by a medical instrument. The sealing film  42   a  partially seals the additional proximal opening  42  and prevents fluid from flowing out of a second instrument channel or working channel  72 . The engaging portion  36  is engaged with the proximal opening  19  in the handle section  17  in a removable manner. A short path or bypass line is defined by the engaging portion  36  for connecting the instrument channel of the assist device  12  with the proximal opening  19  of the handle section  17 . This enables selection of the instrument channel for use between the endoscope  11  and the assist device  12  by changing the direction of the distal end after inserting the forceps device into the additional proximal opening  42  of the assist device  12 . 
     For advance in a path from the external nostril, internal nostril, and esophagus to the stomach and duodenum with steerability, the elongated tubes  16  and  35  have a small diameter with flexibility, and have the diameter and length equal between those. For the purpose of endoscopic treatment, the engaging portion  36  of the assist device  12  can be engaged with the handle section  17  either before or after the entry of the elongated tubes  16  and  35  in a patient&#39;s body. For the subsequent engaging step, a length of the second elongated tube  35  of the assist device  12  preferably can be greater than a length of the first elongated tube  16  of the endoscope  11  in view of easy entry. Note that there may be a patient in which the first elongated tube  16  of the endoscope  11  cannot be entered through a first one of his or her nostrils according to a test. Accordingly, a diameter of the second elongated tube  35  of the assist device  12  is preferably smaller than a diameter of the first elongated tube  16  of the endoscope  11 . 
     In  FIG. 2 , a flexible structure  47  constitutes the flexible tube  22  of the endoscope  11 . The flexible structure  47  is a three layer structure and includes a helical coil  44 , a mesh material  45  and a covering layer  46 . The helical coil  44  is flexible, and defines a tube lumen where constituent components are contained. The mesh material  45  is disposed around the helical coil  44 . The covering layer  46  wraps the mesh material  45  in an overlaid manner and is reinforced by the mesh material  45 . 
     A plurality of constituent components are loosely inserted in the flexible tube  22  of the endoscope  11 , including light guide optics  48  and  49 , steering wires  50 , an instrument channel  51 , an air/water supply channel  52 , a multi-core cable  53 , and a water jet channel  54 . The multi-core cable  53  is a cable for transmitting a signal from a signal processor to drive the image pickup device, and for transmitting an image signal from the image pickup device to the image processor. The multi-core cable  53  includes plural signal lines and a protecting layer for wrapping the signal lines. The steering wires  50  are four wires contained in the flexible tube  22 , extend toward the steering section  21  to contact the periphery of two pulleys in a turnable manner for steering vertically and horizontally upon rotation of the steering wheels  28 . There is a winding  50   a  with tightly wound strands, in which each of the steering wires  50  is inserted. 
     A first distal end surface  20   a  is positioned at an end of the first distal portion  20  of the endoscope  11 . In  FIG. 3 , various elements are disposed on the first distal end surface  20   a , including an imaging window  55 , two lighting windows  56  and  57 , a water jet nozzle  58 , a distal opening  59  or outlet, and an air/water supply nozzle  60 . The imaging window  55  is constituted partially by imaging optics for receiving object light of an object in the body. The lighting windows  56  and  57  are disposed beside the imaging window  55 , and apply light from the light source apparatus  13  to the object in the body through the light guide optics  48  and  49 . 
     The distal opening  59  of the endoscope  11  is formed to communicate from the instrument channel  51  with the proximal opening  19  at the handle section  17 . The air/water supply nozzle  60  operates in response to operation of the air/water supply button  30  at the handle section  17 , draws air or water to an object in the patient&#39;s body, and ejects air or water to the imaging window  55  for cleaning. The water jet nozzle  58  ejects fluid to the object from a syringe connected with the water jet opening  32  in a removable manner, the fluid being such as washing water, drug solution or the like. 
     In  FIG. 4 , an objective optical system or imaging optics  61  are disposed to appear partially in the imaging window  55 . Light from the lighting windows  56  and  57  is reflected by the object in the body, and enters the imaging optics  61 . A prism  62  receives entry of the object light from the imaging optics  61 , and refracts the light. An image pickup device  63  has a light receiving surface where the refracted object light is focused in an originally erected orientation. The image pickup device  63  is kept fixed so that an upper direction of steering of the steering section  21  is set equal to an upper side of an image on the display panel  15 . A circuit board  64  is connected with the image pickup device  63 . Plural signal lines  53   a  in the multi-core cable  53  are connected with the circuit board  64 . 
     A rubber layer  65  for steering is overlaid on an intermediate layer of the first distal portion  20  and the steering section  21  of the endoscope  11 . A connection ring  66  is disposed inside the rubber layer  65 , and receives engagement of a distal end of the steering wires  50 . A plurality of chain links (not shown) are arranged and interconnected with pins in a direction toward the proximal side. The pins are oriented alternately in the vertical direction and then in the horizontal direction as pivotal axes of the chain links. The steering wires  50  are engaged with the inside of the chain links in the slidable manner. The chain links for steering make horizontal and vertical curves upon moving back or forth of the steering wires  50 . 
     The instrument channel  51  is disposed in the steering section  21  of the endoscope  11  and extends through the flexible tube  22 . The instrument channel  51  is formed from flexible synthetic resin. A rigid pipe  67  is connected with a distal end of the instrument channel  51  and disposed inside the first distal portion  20 . A distal end of the rigid pipe  67  is positioned in the distal opening  59 . 
     There is a flexible structure  71  constituting the flexible tube  39  of the assist device  12 . In  FIG. 5 , the flexible structure  71  is a three layer structure including a helical coil  68 , a mesh material  69  and a covering layer  70  in a manner similar to the flexible tube  22  of the endoscope  11 . The helical coil  68  is disposed around the working channel  72 , is flexible and contains the working channel  72 . The mesh material  69  is disposed around the helical coil  68 . The covering layer  70  wraps the mesh material  69  in an overlaid manner and is reinforced by the mesh material  69 . 
     The flexible structure  71  of the assist device  12  is formed from flexible synthetic resin. A bore of the working channel  72  is at least 70% as great as an outer diameter of the second elongated tube  35  of the assist device  12 , and at least two times as great as a bore of the instrument channel  51  of the endoscope  11 . Thus, a medical instrument of a large size can be inserted in the working channel  72  of the assist device  12 . 
     In  FIG. 6 , an end ring  73  is an outer covering part of the second distal portion  37  of the assist device  12 . A distal opening  76  or outlet is formed in a second distal end surface  37   a  of the second distal portion  37 . A support sleeve  75  or rigid pipe is connected with the distal opening  76 . The working channel  72  extends to communicate with the support sleeve  75 . An inner bore in the assist device  12  is equal between the distal opening  76 , the support sleeve  75  and the working channel  72 . 
     An outer layer  74  is positioned externally in the steering section  38  of the assist device  12 , and bendable together with the steering section  21  of the endoscope  11 . The outer layer  74  of the steering section  21  is structurally the same as the flexible tube  39 , but is slightly shiftable to expand and contract in the axial direction to prevent offsetting of the second distal end surface  37   a  of the second distal portion  37  from the first distal end surface  20   a  of the endoscope  11  when bent internally or externally upon bending of the steering section  38  of the endoscope  11 . 
     In  FIG. 7 , the two magnets on the peripheral surface of the first elongated tube  16  of the endoscope  11  has a C-shape as viewed in a cross section, namely, an arcuate shape by partially cutting a ring. A center O of the imaging window  55  is positioned on a line L 1  passing the center P of the first distal end surface  20   a  and higher than the center P of the first distal end surface  20   a  when the first distal end surface  20   a  of the endoscope  11  is viewed in a rotational position of directing an upper portion of the steering section  21  of the steering in an upward direction. An area of magnetic attraction of the magnets  23  and  24  is a range of securing a distal portion of the second elongated tube  35  of the assist device  12  lower than a horizontal line L 2  passing the center O of the imaging window  55  when the first distal end surface  20   a  of the endoscope  11  is viewed in the rotational position of directing the upper portion of the steering section  21  of the steering in the upward direction. In  FIG. 8 , the magnets  40  and  41  on the assist device  12  have a ring shape as viewed in a cross section. 
     Cutouts  77  and  78  are formed in the outer layer  74 . The magnets  40  and  41  are arranged on the steering section  38  in the axial direction of the assist device  12 , fitted in respectively the cutouts  77  and  78 , and set to have a surface flush with the outer layer  74 . Cutouts  79  and  80  are formed in the outer layer  74 . The magnets  23  and  24  are arranged on the steering section in the axial direction of the endoscope  11 , fitted in respectively the cutouts  79  and  80 , and set to have a surface flush with the outer layer  74 . A predetermined distance between the magnets  40  and  41  is equal to that between the magnets  23  and  24 . The steering sections  21  and  38  of the endoscope  11  and the assist device  12  can be retained on one another to orient the distal end surfaces  20   a  and  37   a  by the magnetic attraction at the two points with the predetermined distance. 
     In  FIG. 9 , a distal portion of the second elongated tube  35  of the assist device  12  is fixedly secured to a distal portion of the first elongated tube  16  of the endoscope  11  for the second distal end surface  37   a  of the assist device  12  to contact a lower surface of the first elongated tube  16  under a horizontal line L 2  passing the center O of the imaging window  55 . As illustrated in  FIG. 10 , a range of securing the distal end of the assist device  12  can be preferably defined to dispose the magnets  23  and  24  in a peripheral part which is defined by a line L 3  being perpendicular to a line L 1  passing the window center point and the center P of the distal end surface, the line L 3  being tangential to the outside of the lighting windows  56  and  57 , the peripheral part being contact with a dotted area which is outside an area containing the lighting windows  56  and  57 . 
     In  FIG. 11 , the display panel  15  displays an image of an object in an orientation of setting the upper side of the steering section  21  upwards. An image  15   b  or shadow of the forceps device or medical instrument is displayed in an area under a center of a display frame  15   a  when the elongated tubes  16  and  35  are fixedly set in the positions described with  FIGS. 9 and 10 . 
     The retaining device of the invention is constituted by the magnets  23  and  24  and the magnets  40  and  41 . Alternatively, plural magnets may be attached to a ring shaped belt, which can be mounted on the first elongated tube  16  of the endoscope  11 . For this structure, a positioning portion is formed with the mounting surface for the magnets to lie in the area of the attraction depicted in  FIG. 7 . 
     The endoscope  11  has the image pickup device  63  of  FIG. 12  in the first distal portion  20 . Also, the endoscope  11  includes a CPU  83 , a reference clock oscillator  84 , a TG (timing generator)  85 , and an AFE (analog front end circuit)  86  or AFE processor, all contained in the universal connector  18 . 
     Examples of the image pickup device  63  are a CCD or CMOS image sensor and the like, to pick up an object image focused by the imaging optics  61 . A color filter is disposed on a light receiving surface, and includes plural color segments, for example, a color filter of primary colors of the Bayer array. 
     The CPU  83  controls various elements in the endoscope  11 . The TG  85  creates drive pulses (vertical and horizontal) according to the reference clock signal from the reference clock oscillator  84 , creates a sync pulse for the AFE  86 , and supplies the image pickup device  63  and the AFE  86  with respectively the drive pulses and the sync pulse. The image pickup device  63  responds to a drive pulse input by the TG  85 , picks up an image, and outputs an image signal to the AFE  86 . 
     The AFE  86  includes a CDS (correlated double sampling circuit)  88 , an AGC (automatic gain control) circuit  89  and an A/D converter  90 . The CDS  88  processes the image signal from the image pickup device  63  in the correlated double sampling, and removes reset noise and amplification noise generated in the image pickup device  63  from the image signal. The AGC circuit  89  adjusts the gain of the image signal from the CDS  88  after the noise removal. The A/D converter  90  converts the amplified image signal from the AGC circuit  89  into a digital signal of a predetermined number of bits, and sends the digital signal to the processing apparatus  14  through the universal connector  18 . 
     The TG  85  inputs the horizontal and vertical sync signals and clock signal to the processing apparatus  14  through the universal connector  18  according to the image signal from the AFE  86 . 
     The processing apparatus  14  includes a CPU  91 , an isolator  92 , a digital signal processor (DSP)  93 , a sync signal generator (SSG)  94  and a D/A converter  95 . 
     The CPU  91  controls the processing apparatus  14  and the light source apparatus  13 . The isolator  92  operates for isolating the endoscope  11  from the processing apparatus  14 . The digital signal processor  93  creates a video signal by signal processing of the image signal. 
     The sync signal generator  94  is supplied by the isolator  92  with a horizontal drive pulse, vertical drive pulse and clock pulse which have been output by the TG  85  of the endoscope  11 . The sync signal generator  94  corrects a phase difference between the horizontal drive pulse, vertical drive pulse and clock pulse. The corrected horizontal drive pulse, vertical drive pulse and clock pulse are generated and input to the digital signal processor  93 . 
     The image signal from the AFE  86  of the endoscope  11  is supplied through the isolator  92  to the digital signal processor  93 . The digital signal processor  93  processes the image signal for various functions such as color separation, color interpolation, gain correction, white balance adjustment, gamma correction, image enhancement, and the like, and produces a video signal of the Y/C format including luminance (Y) and chrominance (C). The video signal is output to the D/A converter  95 . The D/A converter  95  converts the video signal into an analog video signal of the NTSC format. There is a connector  96  or plug through which the D/A converter  95  outputs the analog video signal to the display panel  15 . 
     The light source apparatus  13  includes an illuminator  97  or lamp, a light source driver  98 , an aperture stop device  99 , a condensing lens  100  and an illumination CPU  101 . Examples of the illuminator  97  are a xenon lamp, halogen lamp and other white light sources. The light source driver  98  drives the illuminator  97 . The aperture stop device  99  is disposed between the illuminator  97  and entrance ends of the light guide optics  48  and  49 , and adjusts a light amount of the light incident upon the light guide optics  48  and  49 . The condensing lens  100  condenses light from the aperture stop device  99 , and directs the light to the entrance ends of the light guide optics  48  and  49 . The illumination CPU  101  communicates with the CPU  91  of the processing apparatus  14 , and controls the light source driver  98  and the aperture stop device  99 . Light emitted by the illuminator  97  passes through the aperture stop device  99  and the condensing lens  100 , and becomes incident upon the entrance ends of the light guide optics  48  and  49 . Lighting lenses  102  and  103  are disposed to receive the light exited from the exit ends of the light guide optics  48  and  49 , and pass the light to travel toward the object in the body through the lighting windows  56  and  57 . 
     A proximal end of the air/water supply channel  52  in connection with the air/water supply nozzle  60  in the endoscope  11  has an air supply channel  104  and a water supply channel  105  provided by branching. The air supply channel  104  and the water supply channel  105  are respectively connected with the air/water supply button  30 . In  FIG. 13 , the air/water supply button  30  operates for switching the flow, and includes a first outlet orifice  106  for air, a second outlet orifice  107  for water, a second inlet orifice  108  for water, and a first inlet orifice  109  for air. The water supply channel  105  is connected with the second outlet orifice  107 . The air supply channel  104  is connected with the first outlet orifice  106 . A water supply conduit  110  is formed to extend through the universal connector  18 . A water supply tank  111  is connected with the second inlet orifice  108  by the water supply conduit  110 . A valve  112  and an air supply pump  113  are incorporated in the light source apparatus  13  and are connected with the first inlet orifice  109  by the universal connector  18 . 
     An air supply button  114  is disposed to appear externally on the light source apparatus  13 , and operable for setting pressure of an air flow. Information of the pressure set by the air supply button  114  is sent to the illumination CPU  101 , which adjusts the valve  112  according to the pressure information. There is a vent  115  formed through the air/water supply button  30 , for drawing out air as the air/water supply button  30  is driven constantly. In  FIG. 14 , the structure is depicted more specifically. When the air/water supply button  30  is depressed, the first inlet orifice  109  is closed to draw air into the water supply tank  111 . The air ejects water from the endoscope  11 . The water flows through the second inlet orifice  108 , the second outlet orifice  107  and the air/water supply channel  52 , and is ejected through the air/water supply nozzle  60 . 
     In  FIG. 12 , the water jet channel  54  contained in the first elongated tube  16  of the endoscope  11  has a first end connected with the water jet nozzle  58  and a second end connected with the water jet opening  32  in the handle section  17 . A syringe  121  or a tube in connection with the syringe  121  is connected with the water jet opening  32 . When a plunger in the syringe  121  is slid in an axial direction, fluid in the syringe  121  is drawn to flow from the water jet channel  54  toward a lesion through the water jet nozzle  58 . 
     A proximal end of the instrument channel  51  of the endoscope  11  has branches extending to the proximal opening  19  and to the suction button  31  of the handle section  17 . In the suction button  31 , a port  116  is connected with the instrument channel  51 . A port  117  is connected with a suction connector  118  provided in the universal connector  18 . Specifically in  FIG. 15 , a tube  120  extends between the suction connector  118  and a suction device  119  for connection. When the suction button  31  is depressed, the port  117  comes in register with the port  116 . The suction device  119  sucks fluid through the distal opening  59  from the instrument channel  51  of the endoscope  11 , for example mucus, blood or the like. A suction tank  123  is installed for collecting the fluid. 
     In  FIG. 12 , the engaging portion  36  of the assist device  12  is engaged with the proximal opening  19  of the endoscope  11 . The engaging portion  36  includes a short tube  122  or bypass line for connecting the proximal opening  19  of the endoscope  11  with the working channel  72 , and an engaging claw (not shown) which is engageable with the proximal opening  19  of the endoscope  11 . When the engaging portion  36  is connected with the proximal opening  19 , the instrument channel  51  of the endoscope  11  becomes connected with the working channel  72  of the assist device  12 . The suction button  31  of the handle section  17  is depressed. As the assist device  12  is combined for use, the suction device  119  can suck and remove fluid rapidly through the distal opening  59  and the distal opening  76  from the instrument channel  51  and the working channel  72  of the endoscope  11  and the assist device  12  or endoscopic catheter, the fluid being such as mucus, blood or the like. 
     The operation of the above construction is described by referring to  FIG. 16 . In the nasal endoscopy, a middle or lower nasal tract is anesthetized through a nasal cavity inside a first one of the external nostrils for entry of the first elongated tube  16  of the endoscope  11 . A test of the entry is conducted for a doctor to determine one nostril where the first elongated tube  16  can pass for endoscopy. If the first nostril is found too narrow, a second one of the nostrils is used. A nasal tract is anesthetized inside both of the external nostrils. The pretreatment is carried out while the patient is in the sitting position or supine position. Then the first elongated tube  16  is entered in one external nostril while the patient is in the supine position or left lateral position. In  FIG. 17 , a path of the entry is illustrated, and extends from one external nostril  130  to either one of a middle nasal tract  131  and a lower nasal tract  132 , then to an internal nostril  133  and an esophagus  134 , which extends to a stomach. 
     If no treatment is required as a result of observing the duodenum, stomach or the like, then the first elongated tube  16  of the endoscope  11  is pulled away from the body. If a lesion is found and if treatment is possible by use of the instrument channel  51  of the endoscope  11 , then a medical instrument is entered through the instrument channel  51  to carry out the treatment, for example, a small snare instrument, forceps or the like. 
     If it is impossible to treat the lesion by use of the instrument channel  51  of the endoscope  11 , the assist device  12  is used in combination. To this end, a nasal tract in connection with the second nostril is anesthetized for the purpose of entering the second elongated tube  35  of the assist device  12  in the second nostril. Then the first elongated tube  16  of the endoscope  11  is sufficiently moved back to locate its distal end in a range from the internal nostril  133  to the esophagus  134  for the purpose of simultaneous entry of the elongated tubes  16  and  35  of the endoscope  11  and the assist device  12  in a retained state. After this, the second elongated tube  35  of the assist device  12  is entered in the second nostril, and moved through the middle nasal tract  131  or the lower nasal tract  132  to a range from the internal nostril  133  to the esophagus  134 . The elongated tubes  16  and  35  are shifted relative to one another in order to position the distal end surfaces  20   a  and  37   a  equally in the elongated tubes  16  and  35 , so that the magnet  23  of the endoscope  11  attracts the magnet  40  of the assist device  12  and that the magnet  24  of the endoscope  11  attracts the magnet  41  of the assist device  12 . This attraction keeps the distal portion of the second elongated tube  35  of the assist device  12  positioned on the distal portion of the first elongated tube  16  of the endoscope  11  in a manner of contact of the second distal end surface  37   a  of the assist device  12  with the attraction area described with  FIGS. 7 and 10 . Thus, the steering sections  21  and  38  tightly contact one another to direct the distal end surfaces  20   a  and  37   a  in the equal direction. 
     Then the engaging portion  36  of the assist device  12  is engaged with the proximal opening  19  of the endoscope  11 . After the engagement, the elongated tubes  16  and  35  are entered gradually in the body. A doctor observes an image on the display panel  15 , and rotates the steering wheels  28  to enter the tubes by steering the steering section  21  of the endoscope  11 . The steering section  38  of the assist device  12  is bent together with the steering section  21  of the endoscope  11  because stuck on the steering section  21  of the endoscope  11  by magnetic attraction between the magnets  23  and  24  and the magnets  40  and  41 . The second elongated tube  35  can advance by following the entry of the first elongated tube  16  of the endoscope  11 . It is possible to enter the second elongated tube  35  of the assist device  12  only by operation of handling the first elongated tube  16  of the endoscope  11  for entry. 
     Then a lesion requiring treatment is displayed on the display panel  15 . Then a snare instrument, biopsy forceps device or other instrument is inserted through the additional proximal opening  42  of the engaging portion  36  into the second instrument channel or working channel  72  of the assist device  12 . A distal portion of the instrument is moved out of the distal opening  76  of the assist device  12  to carry out the treatment, for example, a pair of biopsy jaws, snare loop, and the like. 
     The biopsy forceps device as an example of treatment instrument includes a pair of biopsy jaws, a control wire and a flexible sheath. The biopsy jaws are jaw cups secured at a distal end of the control wire in an openable manner. The control wire is inserted through the sheath. A proximal end of the control wire is moved back and forth in the axial direction on the side outside the proximal opening, so as to move the biopsy jaws back and forth through the distal end of the sheath. The biopsy jaws are driven for opening and closing. The biopsy forceps device is mainly used for the purpose of capturing tissue. A required outer diameter of an example of forceps channel adapted to the biopsy forceps device is equal to or more than 2.8 mm. 
     In a preferred example of snare instrument, the snare loop produced from resilient wire is set movable into and out of an end portion of a sheath in response to manual operation on the sheath. The snare loop, when pulled back in the sheath, is resiliently deformed in a closed state, and when advanced from the sheath, becomes developed in the widely looped shape. For polypectomy with the snare instrument, at first the snare loop is wound on a root portion of the polyp sufficiently tightly. Then a current of high frequency is drawn in the snare loop to burn tissue contacting the snare loop for simultaneous cutting and coagulation. In general, a required outer diameter of the forceps channel suitable for the snare instrument is equal to or more than 2.8 mm. 
     Through the working channel  72  of the assist device  12 , the snare instrument, biopsy forceps device or other instrument is used for biopsy of tissue, or for treatment, for example, removal of foreign material, hemostasis, removal of a tumor, destruction of biliary stones or the like. 
     The lighting windows  56  and  57  in the first distal end surface  20   a  of the endoscope  11  are so disposed that the imaging window  55  is between those. See  FIG. 3 . The second distal end surface  37   a  of the assist device  12  is located fixedly lower than the imaging window  55 . See  FIG. 7 . Also, the second distal end surface  37   a  is located fixedly on the periphery associated with an area (dotted in  FIG. 10 ) opposite to the area of the lighting windows  56  and  57 . Therefore, the image  15   b  of the forceps device inserted in the working channel  72  of the assist device  12  is displayed under the center of the display frame  15   a  of the display panel  15 . This prevents occurrence of a shadow on the object due to blocking light with the forceps device, and occurrence of white defects in an image with light reflected by the forceps device. 
     In order to suck fluid such as mucus, blood or the like, the suction button  31  of the handle section  17  can be depressed to suck the fluid not only through the distal opening  59  of the endoscope  11  but also through the distal opening  76  of the assist device  12 . So the fluid can be sucked rapidly. An amount of the suction can be high, because of simultaneous operation through both of the distal openings  59  and  76 . 
     After the treatment is finished, the medical instrument such as biopsy forceps device and snare instrument is removed from the additional proximal opening  42  of the assist device  12 . Then the second elongated tube  35  and the first elongated tube  16  of are removed from the body at a sufficient slow speed. The distal portions of the elongated tubes  16  and  35  are released from their retention before their passage from the internal nostrils to the esophagus. The magnets  40  and  41  can be released from magnetic attraction on the magnets  23  and  24  by shifting one of the elongated tubes  16  and  35  of the endoscope  11  and the assist device  12  from one another in the axial direction. After the release, the elongated tubes  16  and  35  are removed in the order of the assist device  12  and then the endoscope  11 . Finally, the engaging portion  36  of the assist device  12  is removed from the proximal opening  19  of the handle section  17 . 
     Note that there is a situation in which impossibility of the treatment by use of the instrument channel  51  of the endoscope  11  has been found initially. For this situation, the assist device  12  is used as a fixed process. Connection of the engaging portion  36  of the assist device  12  to the handle section  17  may be carried out before entry of the second elongated tube  35  of the assist device  12 , or after the retention between the elongated tubes  16  and  35 . 
     In the above embodiment, the engaging portion  36  is connected with the handle section  17 . However, proximal portions of the endoscope  11  and the assist device  12  may have structures without engageable parts. In  FIG. 18 , another preferred assist device  140  or endoscopic catheter is illustrated. There are a proximal opening  141  or inlet and a suction connector  142  provided by branching at a proximal end of the second instrument channel or working channel  72 . A suction device  143  is connectable to the suction connector  142 . The suction device  143  includes a control unit  145  and a pump  146 , and is structured in a manner specialized for the assist device  140 . It is preferable to connect a foot switch  144  to the control unit  145 , and to operate the assist device  12  for suction by depressing the foot switch  144  with a foot of a doctor or operator. This is effective in simplifying his or her manual operation when the endoscope  11  is used in combination. In the present embodiment, the suction is possible discretely through the instrument channel  51  of the endoscope  11  and the working channel  72  of the assist device  12 . For example, the working channel  72  of the assist device  12  can be used for retrieving relatively large pieces of tissue. The instrument channel  51  of the endoscope  11  can be used for retrieving relatively small pieces of tissue. 
     In the above embodiments, the magnets  23 ,  24 ,  40  and  41  are permanent magnets. However, it is possible in the invention to dispose the electromagnet on a first one of the elongated tubes and the ferromagnetic component on a second one of the elongated tubes. A switching portion for turning on and off the electromagnet may be disposed on the first elongated tube. An electric current flows in the electromagnet upon operation of the switching portion to attract the ferromagnetic component. In a structure of the endoscope  11  having the electromagnet, a current can be drawn through the universal connector  18  from the light source apparatus  13  of the processing apparatus  14 . In contrast, in a structure of the assist device  12  having the electromagnet, a terminal can be positioned on a proximal end of the assist device  12  for being supplied with the current. The terminal can be connected with the light source apparatus  13  or the processing apparatus  14 . Alternatively, a separate power source can be prepared and can be connected with the terminal of the assist device  12 . 
     In  FIGS. 19 and 19A , one preferred nasal endoscope  150  having a retaining device  151  with a pull strip is illustrated. A retention lumen  152  is formed through the first elongated tube  16  of the endoscope  150 . The retaining device  151  of a snare form is inserted in the retention lumen  152 . A retention loop  153  is an end portion of the retaining device  151 , and captures and retains the second elongated tube  35  of the assist device  12 . This retaining device retains the elongated tubes  16  and  35  to direct the distal end surfaces in the same direction. A lumen outlet  154  is a first end of the retention lumen  152  and is formed at a distal end of the endoscope  150 . A lumen inlet  155  is a second end of the retention lumen  152  and is formed in the handle section. The retaining device  151  is constituted by a sheath and a resilient pull strip of wire contained in the sheath in a slidable manner. The retention loop  153  is formed by bending the wire and shiftable between its open and closed states. A pull portion  156  or handle is a proximal end portion of the pull strip of the retaining device  151 , and extends outside the lumen inlet  155 . 
     When the pull portion  156  is moved back or forth relative to the sheath, the retention loop  153  of the retaining device  151  is resiliently deformed in a state pulled in the sheath, but becomes developed widely in a looped form in a state shifted in the axial direction. Before entry of the endoscope  150  in the patient&#39;s nostril, the retention loop  153  is initially closed. To retain the distal portions on one another, the retention loop  153  spreads in the looped form to receive insertion of the distal portion of the second elongated tube  35  of the assist device  12 . Then the pull portion  156  is pulled back to tighten the retention loop  153 . Thus, the distal portion of the assist device  12  can be retained on the distal portion of the endoscope  150 . 
     The lumen outlet  154  for protrusion of the retention loop  153  can be formed in the area of the attraction described with  FIGS. 7 and 10  in the peripheral part of the second distal portion  37  of the endoscope  150 . The distal portion of the assist device  12  or endoscopic catheter can be kept stationary in an area under the imaging window  55 , or on the peripheral surface in an area (dotted in  FIG. 10 ) opposite to the area of the lighting windows  56  and  57 . Note that the lumen outlet  154  is depicted in  FIG. 10  in such an orientation as to direct the upper side of the steering of the steering section  21  in the downward direction for clarification. 
     Only one light source, or three or more may be incorporated in the endoscopes  11  and  150 . Also, a light source may include an LED and a driver for driving the LED in place of the light guide optics  48  and  49  and the lighting lens. 
     In  FIGS. 20-32 , another preferred endoscope system  210  is illustrated, which is for the purpose of removing a shadow of a forceps device in an endoscopic image in imaging of an object in a body. Elements of the above embodiments are designated with identical reference numerals. The endoscope system  210  includes a nasal endoscope  211 , an assist device  212  or light delivery catheter, the light source apparatus  13 , the processing apparatus  14  and the display panel  15 . A proximal end  216   a  is included in the first elongated tube  16 , and is connected with the grip portion  22   a  having a great diameter. 
     The handle section  17  includes the air/water supply button  30  and the suction button  31  in addition to the steering wheels  28 . A sealing film  225  or channel lid is disposed in the proximal opening  19  in a removable manner. A sealing portion of the sealing film  225  has flexibility, includes slits or small pores, and is openable when pushed by a medical instrument. The sealing film  225  partially seals the proximal opening  19  and prevents fluid from flowing out of the proximal opening  19  through the instrument channel. 
     The first distal portion  20  includes a rigid tubular structure and relevant devices contained in the tubular structure. The devices include imaging optics, an image pickup device and lighting optics. The universal connector  18  includes the light guide coupler  25  and a video connector  234  or plug. There is a signal cable  233  of which the video connector  234  is secured to an end. An electric connector  235  or plug or socket is disposed in the front panel of the processing apparatus  14 , and connected with the video connector  234 . A light guide coupler  236  or socket is disposed in the front panel of the light source apparatus  13 , and connected with the light guide coupler  25 . 
     In the assist device  212 , a grip portion  240  is attached to a proximal end  229   a  of the second elongated tube  35 , and has a great diameter to facilitate manual grasping. A light guide cable  242  extends from the grip portion  240 . An auxiliary light guide coupler  241  is disposed at an end of the light guide cable  242 . An auxiliary light guide coupler  243  is an optical element associated with the light source apparatus  13 . The auxiliary light guide coupler  241  is connected with the auxiliary light guide coupler  243  in a removable manner. 
     A second distal tube region  250  is included in the second elongated tube  35  of the assist device  212 . Light guide optics are contained in a tube lumen which extends from the second distal tube region  250  to the proximal end  229   a  through the second elongated tube  35 . The light guide optics transmit light from the light source apparatus  13  toward lighting optics disposed behind a lighting window on the second distal end surface  37   a  of the second elongated tube  35 . 
     The grip portion  240  of the assist device  212  is engaged with the handle section of the endoscope  211  in a removable manner, and can be handled together. There are receiving holes  251  and  252  or receiving portions formed in the grip portion  22   a  of the endoscope  211 . Engaging projections  253  and  254  or engaging portions are formed on the grip portion  240  of the assist device  212  for engagement with the receiving holes  251  and  252 . A structure including the engaging projections  253  and  254  and the receiving holes  251  and  252  constitutes an engaging mechanism in a removable manner. The receiving holes  251  and  252  are recesses or cutouts. A small flexible ridge is formed with each of the engaging projections  253  and  254  for engagement with the hole in a manner with a click. The receiving hole  252  is positioned from the receiving hole  251  at a predetermined distance in the axial direction of the first elongated tube  16 . The engaging projection  254  is positioned from the engaging projection  253  at a predetermined distance in the axial direction of the second elongated tube  35 . One of the receiving holes  251  and  252  and one of the engaging projections  253  and  254  operate for positioning. A remaining one of the receiving holes  251  and  252  and a remaining one of the engaging projections  253  and  254  operate for an anti-rotation purpose. Note that other structures can be used for the engagement, for example, a claw and a hole in combination, magnetic attraction with magnetic components, a strip for winding to retain, and the like. 
     In  FIG. 23 , a part of the imaging optics  61  is disposed in the imaging window  55 . Light emitted from the lighting window  56  travels to and is reflected by an object in the patient&#39;s body, and then becomes incident on the imaging optics  61 . A prism  271  receives the object light from the imaging optics  61  and refracts the object light. A light receiving surface of an image pickup device  272  receives the object light from the prism  271 . A circuit board  273  is connected with the image pickup device  272 . Signal lines  274  of the multi-core cable  53  are connected with the circuit board  273 . 
     The light guide optics  48  are contained in the steering section  21  of the endoscope  211 . A plurality of optical fibers are bundled in a cylindrical shape. A protective tube  260   a  is formed from elastic material such as silicone resin, and wraps the optical fibers to constitute the light guide optics  48 . The lighting lens  102  has an entrance surface  280 . An exit end  277  of the light guide optics  48  is kept in contact with the entrance surface  280  inside the rubber layer  65 . An exit surface  279  of the lighting lens  102  is located opposite to the entrance surface  280 , and constitutes the lighting window  56 . The lighting lens  102  is the lighting optics according to the invention. The exit end  277  of the light guide optics  48  is also kept stationary inside the rubber layer  65 . 
     In  FIG. 24 , a longitudinal receiving surface  281  is formed in the second elongated tube  35  of the assist device  212 , and has a shape with a concave surface for tight contact with a first distal tube region  220  of the endoscope  211 . The receiving surface  281  causes the second elongated tube  35  to have a form of a crescent as viewed in a cross section. In the covering layer  70  of the receiving surface  281 , the magnets  40  and  41  are fitted to have the receiving surface  281  for attraction of the magnets  23  and  24  of the endoscope  211 . The shape of the second elongated tube  35  of the assist device  212  can be circular. Also, ferromagnetic components attractable magnetically may be used in place of the magnets  40  and  41 . 
     Light guide optics  286  are contained in the assist device  212 . A plurality of optical fibers  287  are bundled in a cylindrical shape. A protective tube  288  is formed from elastic material such as silicone resin, and wraps the optical fibers  287  to constitute the light guide optics  286 . A diameter of the light guide optics  286  except for the protective tube  288  is set greater than a diameter of the light guide optics  48  of the endoscope  211 . 
     In  FIG. 25 , an outer rigid ring  290  is a covering part of the second distal portion  37  of the assist device  212 . A lens holder  291  is retained inside the second distal portion  37  in a stationary manner. A lighting lens  289  is retained in the lens holder  291  as lighting optics. An exit surface  293  of the lighting lens  289  is positioned in a lighting window  292  which is formed in the second distal end surface  37   a . An entrance surface  294  of the lighting lens  289  is positioned opposite to the exit surface  293 . An exit end  295  of the light guide optics  286  is disposed at the entrance surface  294 . Note that the lighting lens  289  may include plural lens elements instead of a single lens element. In addition to the removal of a shadow with the lighting lens  289  in the assist device  212 , it is possible to change a region of diffusion of a light lens on the entrance surface  294  between a narrow region for compensating for shortage in the light amount of the endoscope  211  and a wide region for enlarging the angle of the distribution. 
     The steering section  38  has a covering layer  296 . Two cutouts  297  are formed in the covering layer  296 , and receive the magnets  40  and  41 . In  FIG. 26 , the magnets  40  and  41  are fitted in a peripheral part of the second distal tube region  250  as viewed with respect to the second distal end surface  37   a  in an arcuate form. The peripheral part is so determined as to attract the second distal tube region  250  of the assist device  212  to position the lighting window  292  in the second distal end surface  37   a  of the assist device  212  opposite to the lighting window  56  with reference to the distal opening  59  in the first distal end surface  20   a  of the endoscope  211 . 
     Upon the magnetic attraction, the endoscope  211  and the assist device  212  are so positioned that the isolator  92  is positioned opposite to the lighting window  56  with reference to the distal opening  59  of the endoscope  211 . Note that it is preferable to position a window center point  292   a  of the lighting window  292  of the assist device  212  on a straight line  300  which passes a window center point  266   a  of the lighting window  56  of the endoscope  211  and an opening center point  267   a  of the distal opening  59 . 
     In  FIG. 27 , the magnets  40  and  41  of the assist device  212  are fitted in the cutouts  297  formed in the covering layer  296 , and are set to have a surface flush with the covering layer  296 . Also, a cutout  301  is formed in the outer wall of the endoscope  211 , and receives the magnets  23  and  24  to define their surface flush with the outer wall. 
     The distal opening  59  is disposed on the lower left side from the imaging window  55 . In  FIG. 28 , an image of a forceps device  302  or treatment instrument appears on the display panel  15  in a form protruding from the lower left side. Also, the lighting window  56  is disposed on the right side from the distal opening  59  as viewed from the imaging window  55 . A shadow due to the forceps device  302  and an instrument head  303  appears in the image. As the assist device  212  is combined for use, the lighting window  292  of the assist device  212  is positioned on the left side as viewed from the imaging window  55 . A shadow  304  of the forceps device  302  and the instrument head  303  can be eliminated by lighting of the assist device  212  to the left side of the forceps device  302  and the instrument head  303 . 
     Specifically with a large distribution of light from the assist device  212 , a problem is likely to occur with shadows of a forceps device or its instrument head on a side opposite to the assist device  212  with reference to the distal opening  59 . Let an axis  269  be a line where a forceps device moves out of the distal opening  59  of the endoscope  211 . In  FIG. 29 , it is preferable for the lighting lens  289  to have such a distribution characteristic that a light flux  298  exited from the lighting lens  289  of the assist device  212  does not intersect with the axis  269  irrespective of an object distance in an imaging direction from the distal end surfaces  20   a  and  37   a  of the elongated tubes  16  and  35  of the endoscope  211  and the assist device  212 . Note that a movable range  259  is defined as a range where the forceps device can be moved in and out. The lighting lens  289  has an optical axis  289   a  which is substantially parallel with the axis  269 . 
     In the light source apparatus  13 , a filter device  323  for limiting light is movable into and out of a light path of light from the illuminator  97 , and limits a light amount of a component of a particular band of a wavelength in the white light from the illuminator  97 . 
     Light from the illuminator  97  is adjusted by the aperture stop device  99  and the condensing lens  100 . Entrance ends  326  and  327  are included in respectively the light guide optics  48  of the endoscope  211  and the light guide optics  286  of the assist device  212 . The adjusted light becomes incident upon the entrance ends  326  and  327 . Light emitted from the exit end  277  of the light guide optics  48  of the endoscope  211  is applied to an object in the body through the lighting lens  102  and the lighting window  56 . Light emitted from the exit end  295  of the light guide optics  286  of the assist device  212  is applied to the object in the body through the lighting lens  289  and the lighting window  292 . 
     In  FIG. 32 , a power button  345  is disposed on the front of the light source apparatus  13  near to the right corner. The power button  345  is turned on and off to switch the supply of power to the light source apparatus  13  by use of a commercial power source. There are a lighting button  346 , a light adjusting button group  347  and a light limiting button  348  arranged beside the power button  345 . Also, the light guide coupler  236  is disposed on the front of the light source apparatus  13  for connection with the light guide coupler  25 . The auxiliary light guide coupler  243  is disposed on the front of the light source apparatus  13  for connection with the auxiliary light guide coupler  241  of the assist device  212 . 
     The lighting button  346  is a pushbutton for turning on and off the light source. The light adjusting button group  347  includes an increase button  347   a  and a decrease button  347   b , and adjusts the light stepwise by control of a diameter of the aperture, for example in  10  steps. Note that the brightness can be adjusted by insertion of a light limiting filter, adjustment of current for a light source lamp, and the like. The light limiting button  348  is a pushbutton for turning on or off the limitation of light amount of a component of a predetermined band in the white light by use of a filter movable into or out of the light path. 
     Before imaging by use of the endoscope  211 , the lamp of the light source is adjusted for brightness and a wavelength of light to be emitted according to information such as personal data of a patient, a result of the diagnosis, information of an object or tissue in his or her body. In the light source apparatus  13 , the power button  345  is turned on, before the lighting button  346  is turned on. The light adjusting button group  347  is operated to adjust and optimize the brightness of the object. Then the light limiting button  348  is turned on or off as required. 
     The operation of the embodiment is hereinafter described by referring to  FIG. 33 . When a doctor discovers a lesion in a duodenum, stomach or other organs in the gastrointestinal tract, it is checked by use of the endoscope  211  whether treatment of the lesion is possible. If the treatment is possible, the lesion is treated by use of a forceps device or other medical instruments. Specifically, the forceps device is inserted in the proximal opening  19  of the endoscope  211  for an instrument head to protrude through the distal opening  59 . A handle is positioned at a proximal end of the forceps device, and is slid outside the proximal opening  19  to move the instrument head back and force. In  FIG. 28 , shadows appear on the display panel  15  according to shapes of the forceps device and the instrument head. It is likely that a lesion cannot be clearly imaged due to the shadows. To solve this problem, the assist device  212  is used. 
     To combine the assist device  212  with the endoscope  211 , at first a nasal tract in connection with the second nostril is anesthetized for the purpose of entering the second elongated tube  35  of the assist device  212  in the second nostril. The elongated tubes  16  and  35  are shifted relative to one another in order to position the distal end surfaces  20   a  and  37   a  equally in the elongated tubes  16  and  35 , so that the magnet  23  of the endoscope  211  attracts the magnet  40  of the assist device  212  and the magnet  24  of the endoscope  211  attracts the magnet  41  of the assist device  212 . 
     Then the grip portion  240  of the assist device  212  is secured to the grip portion  22   a  of the endoscope  211  next. To this end, the receiving holes  251  and  252  are engaged with the engaging projections  253  and  254 . This facilitates the manual handling because the grip portion  240  of the assist device  212  can be grasped together with the grip portion  22   a  of the endoscope  211 . 
     Then the auxiliary light guide coupler  241  of the assist device  212  becomes connected with the auxiliary light guide coupler  243  of the light source apparatus  13 . The lighting button  346  remains turned on. There is a cap fitted on the auxiliary light guide coupler  243  for preventing leaking of light. The auxiliary light guide coupler  243  can be connected only after removing the cap. After the connection, the elongated tubes  16  and  35  are entered gradually. 
     As has been described with  FIG. 26 , the second distal end surface  37   a  of the assist device  212  is positioned on the left from the imaging window  55  because of the use of the assist device  212 . The left side of the forceps device and instrument head can be illuminated to remove their shadows. If the instrument head remains open, a lesion in front of the instrument head can be illuminated to carry out the treatment in a good condition of observation with the endoscope. 
     After the treatment is finished, the medical instrument such as biopsy forceps device and snare instrument is removed from the proximal opening  19  of the endoscope  211 . The second distal tube region  250  is disengaged from the first distal tube region  220  of the endoscope  211 . Then the second elongated tube  35  and the first elongated tube  16  of the assist device  212  and the endoscope  211  are removed from the body, in the order of the second and then the first. Finally, the lighting button  346  is turned off. The auxiliary light guide coupler  241  of the assist device  212  is removed from the auxiliary light guide coupler  243  of the light source apparatus  13 . Note that the assist device  212  can be used in addition from the initial step of the operation. 
     In the endoscope  211  of the above embodiment, only the lighting window  56  is formed in the first distal end surface  20   a . In  FIG. 34 , one preferred nasal endoscope  160  is illustrated, and includes two lighting windows  161  and  162  beside the imaging window  55 . It is possible to dispose the lighting window  292  of the assist device  212  on a side opposite to the lighting window  161  with reference to the distal opening  59  of the endoscope  160 , and to dispose a window center point  292 ’ of an assist device  212 ′ or light delivery catheter on a side opposite to the lighting window  162  with reference to the distal opening  59 . Thus, magnets or magnetic components  163  and  164  of the endoscope  211  are arranged in a range to retain the second distal tube region  250  of the assist device  212  at the two points. The magnets  163  and  164  are so disposed that the window center point  292   a  of the lighting window  292  of the assist device  212  is positioned on a straight line  165  which passes a window center point  161   a  of the lighting window  161  and the opening center point  267   a  of the distal opening  59 . Furthermore, it is possible to dispose the magnets  163  and  164  so that a window center point  292   a ′ of the lighting window  292 ′ of the assist device  212 ′ is positioned on a straight line  166  which passes a window center point  162   a  of the lighting window  162  and the opening center point  267   a  of the distal opening  59 . 
     In the above embodiment, one lighting window is formed in the assist device  212 . In  FIG. 35 , another preferred assist device  170  or light delivery catheter includes two lighting windows  171  and  172 . Two magnets or magnetic components  173  are disposed on the elongated tube of the endoscope  160 , and arranged in the axial direction. Two magnets or magnetic components  175  are positioned on a periphery of the elongated tube of the assist device  170 . The magnets  175  are attracted on the magnets  173  in such a position that a window center point  172   a  of the lighting window  172  of the assist device  170  is positioned on a straight line  176  passing the window center point  161   a  of the lighting window  161  and the opening center point  267   a  of the distal opening  59  and opposite to the lighting window  161  with reference to the distal opening  59 . 
     In  FIG. 36 , a lighting lens  178  is disposed in the lighting window  171  or spot lighting window of the assist device  170 . There is created a spot area  180  illuminated by light from the lighting lens  178  in spot illumination or high beam illumination in a manner of suppressing diffusion. A lighting lens  179  is disposed in the lighting window  172  of which the window center point  172   a  is positioned on the straight line  176 . There is created a large area  181  illuminated by light from the lighting lens  179  in low beam illumination. Note that optical axes  178   a  and  179   a  of the lighting lenses  178  and  179  are parallel with one another. 
     In the embodiment of  FIG. 36 , a first area B illuminated through the lighting lens  179  at a predetermined irradiance is larger than a second area A illuminated through the lighting lens  178  at the equal predetermined irradiance, at any object distance from the second distal end surface  37   a  of the assist device  170  in the imaging direction. It is possible to remove a shadow of the forceps device by the low beam illumination and to obtain a high light amount of illumination because of the single lighting window  161  of the endoscope  211  in the high beam illumination. In  FIG. 36 , light guide optics  182  and  183  are illustrated. 
     In  FIG. 37 , one preferred assist device  185  or light delivery catheter is illustrated, and has four lighting windows  186 ,  187 ,  188  and  189 . A magnet or magnetic component  184  is disposed on the outside of the endoscope  160 . A magnet or magnetic component  192  is disposed on the outside of the assist device  185 , and attracts the magnet  184  at a single point. The lighting windows  186  and  187  of the assist device  185  become positioned opposite to the lighting window  162  of the endoscope  160  with reference to the distal opening  59 . The lighting windows  188  and  189  of the assist device  185  become positioned opposite to the lighting window  161  of the endoscope  160  with reference to the distal opening  59 . 
     Window center points  186   a  and  187   a  of the lighting windows  186  and  187  of the assist device  185  are disposed on the straight line  176  which passes the window center point  162   a  of the lighting window  162  of the endoscope  160  and the opening center point  267   a  of the distal opening  59 . Window center points  188   a  and  189   a  of the lighting windows  188  and  189  of the assist device  185  are disposed on a straight line  177  which passes the window center point  161   a  of the lighting window  161  of the endoscope  160  and the opening center point  267   a  of the distal opening  59 . The lighting windows  186  and  188  nearer to the endoscope  211  operate for high beam illumination as spot lighting windows. The lighting windows  187  and  189  farther from the endoscope  211  operate for low beam illumination as diffusion lighting windows. 
     In the above embodiments, the assist devices  170 ,  185  and  212  are connected directly to the light source apparatus  13 . Alternately, a coupler may be added to the light guide optics by branching off in the endoscope  211 . The light guide optics of the assist devices  170 ,  185  and  212  can be connected with the coupler for transmitting light from the endoscope  211  to the assist devices  170 ,  185  and  212 . 
     In the above embodiments, the light source for the endoscope  211  is used also for lighting in the assist devices  170 ,  185  and  212 . However, two light source units may be contained in the light source apparatus  13  for the endoscope  211  and the assist devices  170 ,  185  and  212 . For this structure, an auxiliary lighting button  190  is disposed in the light source apparatus  13  for turning on the lighting of the assist devices  170 ,  185  and  212 . See  FIG. 32 . 
     Also, a second light source may be added for generating light for the assist devices  170 ,  185  and  212  discretely from the light source apparatus  13  for generating light for the endoscope  211 . 
     In the above embodiments, the light source for the assist devices  170 ,  185  and  212  is associated with light guide optics. However, a light source may have a white LED. For this structure, a driver and an auxiliary connector are incorporated in each of the assist devices  170 ,  185  and  212 . The driver drives the LED by connection of a signal line. The auxiliary connector is disposed at an end of a cable extending from a proximal end of the assist devices  170 ,  185  and  212 , and is connected with an LED controller. The LED controller is connected with the processing apparatus  14 , retrieves brightness information by communication with the CPU in the processing apparatus  14  upon creating a video signal, and controls the driver to optimize the brightness of the LED for the imaging condition. A lighting button is associated on the LED controller. The LED can be turned on and off by operating the lighting button. Note that the driver may be incorporated in the distal portion of the assist devices  170 ,  185  and  212  or in the LED controller. Also, it is possible to incorporate the LED controller in the light source apparatus  13  and connect the auxiliary connector with the light source apparatus  13 . 
     Also, a white LED for lighting may be used in the endoscope  211  instead of the light guide optics. For this structure, the single LED controller can be used in connection with both of the endoscope  211  and the assist devices  170 ,  185  and  212 . Alternatively, two LED controllers can be installed discretely for connection with the endoscope  211  and the assist devices  170 ,  185  and  212 . 
     Furthermore, it is possible in an assist device or light delivery catheter to incorporate an instrument channel, a water jet channel and the like in addition to the lighting structure. 
     Although the present invention has been fully described by way of the preferred embodiments thereof with reference to the accompanying drawings, various changes and modifications will be apparent to those having skill in this field. Therefore, unless otherwise these changes and modifications depart from the scope of the present invention, they should be construed as included therein.