referring now to fig1 to 13 , a marker used in the endoscopic treatment tool ( hereinafter , referred to as “ marker ”) according to an embodiment of the invention will be described . fig1 is a perspective view of a marker 1 . the marker 1 is formed of an elastic material such as silicone rubber . the marker 1 includes a substantially cylindrical body 2 and a engaging portion 3 provided at a front end of the body 2 . fig2 is a right side view , partially shown in cross - section , of the marker 1 . the marker 1 includes an insertion hole 4 along its central axis in which an endoscopic treatment tool is inserted . the insertion hole 4 includes a tip section 4 a at the side of engaging portion 3 , an inserting section 4 c at the side of an opposite rear end , and a middle section 4 b between the tip section 4 a and the inserting section 4 c . as shown in fig1 and 3 , the tip section 4 a is square - sectioned and functions as a fixing portion for fixing the body 2 to an intended position of the middle section of the endoscopic treatment tool due to frictional force generated at the contact face of the tip section 4 a and the external surface of the endoscopic treatment tool as described later . the middle section 4 b is circular - sectioned and has a diameter larger than the maximum inner diameter ( i . e ., the diagonal diameter in the cross - section ) of the tip section 4 a . thus , the middle section 4 b does not come in direct contact with an external surface of the endoscope treatment tool . the inserting section 4 c is also circular - sectioned and has a diameter that is substantially the same as that of the middle section 4 b at the side of the middle section 4 b and gradually expands toward the rear end . namely , the inserting section 4 c is formed in a tapered shape such that the endoscopic treatment tool may be easily inserted from the expanded rear end of the insertion hole 4 . the marker 1 is removably attached to the endoscopic treatment tool . in particular , after the endoscopic treatment tool is inserted from the inserting section 4 c and the marker 1 is attached , the endoscopic treatment tool can be removed . the engaging portion 3 includes an annular engaging groove 5 provided in a circumferential direction thereof on a radial direction outside of the insertion hole 4 , and a flange 6 circumferentially projecting from the radial direction outside of the engaging groove 5 . the engaging groove 5 is provided between the external surface of the tip section 4 a of the insertion hole 4 and the body 2 concentrically with the insertion hole 4 . a guide sheath is engaged in the engaging groove 5 as described later . as shown in fig2 , the engaging groove 5 includes a first surface 5 a at the side of the flange 6 formed substantially parallel with the axial direction of the marker 1 , and a second surface ( wall surface ) 5 b at the side of the insertion hole 4 formed such that a radial direction width w 1 of the engaging groove 5 at the front end is slightly larger than a radial direction width w 2 at the rear end . that is , the engaging groove 5 is tapered such that the radial direction width thereof becomes smaller toward the axial direction of the insertion hole 4 . fig4 is a partial cross - sectional view of a guide sheath 7 used with the marker 1 . the guide sheath 7 includes a tubular , flexible sheath body 8 made of , for example , resin , and a stick ( engaging member ) 9 attached to a base end of the sheath body 8 . as shown in fig4 , a tubular indexing member 10 made of stainless steel or the like is thermoformed at an inner surface of the sheath body 8 near the tip thereof . with the x - ray radioscopy , the indexing member 10 is an indication of the tip position of the sheath body 8 . a base end of the sheath body 8 is press - fit at the tip of the stick 9 and is fixed by a coil 11 from the outside . the stick 9 is a tubular member made of resin or the like , and includes a through hole 12 inside thereof . an endoscopic treatment tool is inserted in the through hole 12 . the through hole 12 is circular - sectioned and includes a first section 12 a with a constant diameter and a second section 12 b with a diameter gradually expanding toward the rear end . the inner surface of the second section 12 b is formed such that the wall surface of the stick 9 becomes thicker in the axial direction of the stick 9 from the rear end where the stick 9 enters the engaging groove 5 of the marker 1 . the taper angle of the inner surface of the second section 12 b is larger than that of the second surface 5 b of the engaging groove 5 of the marker 1 . referring now to fig5 to 13 , an operation of the marker 1 and the guide sheath 7 will be described . fig5 is a flow chart illustrating a procedure of lung biopsy using an endoscopic treatment tool performing with the marker 1 and the guide sheath 7 . first , in step s 1 shown in fig5 , the guide sheath 7 is moved to the target site where tissue samples are to be taken . in particular , the endoscope is advanced within a bronchus while the position of the target site is observed through x - ray radioscopy images . fig6 illustrates a state in which an endoscope 100 is advanced to the vicinity of a target site r . since the diameter of a bronchiole 101 in which the target site r exists is smaller than that of the endoscope 100 , the endoscope 100 cannot be advanced further toward the target site r . here , an ultrasonic probe 102 placed in the guide sheath 7 is inserted together with the guide sheath 7 from an opening for forceps ( not shown ) of the endoscope 100 and is projected from the tip of the endoscope 100 as shown in fig7 . since the diameters of the sheath body 8 and the ultrasonic probe 102 of the guide sheath 7 are smaller than that of the endoscope 100 , the guide sheath 7 can reach the target site r through the bronchiole 101 . as shown in fig8 , the sheath body 8 itself is stopped at a position considered near but not touching the target site r , and the ultrasonic probe 102 is moved ahead to a position beyond the target site r . then , the ultrasonic probe 102 is slowly pulled back in the direction of an arrow in fig8 . images of the tissue around the ultrasonic probe 102 are displayed on unillustrated test equipment through the ultrasonic wave emitted from the ultrasonic probe 102 . thus , the operator can confirm whether the ultrasonic probe 102 has reached the target site r . after the operator confirmed that the ultrasonic probe 102 has reached the target site r , the procedure proceeds to step s 2 . in step s 2 , the sheath body 8 is advanced to the vicinity of the target site r along the ultrasonic probe 102 as shown in fig9 . the position of the tip of the sheath body 8 is confirmed by the indexing member 10 ( not shown ). here , in a state in which the tip of the ultrasonic probe 102 is placed in the position where the tissue samples are to be taken , the position of the ultrasonic probe 102 projected from the rear end of the stick 9 of the guide sheath 7 is marked . then , only the ultrasonic probe 102 is removed from the guide sheath 7 and the guide sheath 7 is held there . in the next step s 3 , a known biopsy cup ( endoscopic treatment tool ) 103 is inserted in the insertion hole 4 from the rear end of the marker 1 , and the marker 1 is fixed to the biopsy cup 103 as shown in fig1 . the marker 1 is then slid to a position where the distance between the rear end of the engaging groove 5 and the tip of the biopsy cup equals the distance between the tip of the ultrasonic probe 102 and the marking taken in step s 2 . instead of the biopsy cup 103 , other treatment tools such as a biopsy brush may alternatively be used . as described above , since the tip section 4 a of the insertion hole 4 which functions as the fixing portion is square - sectioned , the tip section 4 a is made to contact the biopsy cup 103 at four sides 4 d as shown in fig1 . thus , the frictional force generated between the tip section 4 a and the biopsy cups 103 is small , whereby the marker 1 can be slid smoothly for positional alignment . if the marker 1 is formed of a transparent material , the rear end of the engaging groove 5 is more clearly visible , and positioning of the marker 1 can be made more precisely . next , in step s 4 , the biopsy cup 103 to which the marker 1 is attached is inserted in the guide sheath 7 from the base end of the stick 9 . then , as shown in the dotted line in fig1 , the rear end of the stick 9 is made to advance into the engaging groove 5 of the marker 1 , and the marker 1 is engaged in the guide sheath 7 . since the taper angle of the inner surface of the second section 12 b of the through hole 12 formed in the stick 9 is larger than that of the second surface 5 b of the engaging groove 5 of the marker 1 , the second surface 5 b of the engaging groove 5 is pressed against the insertion hole 4 as the stick 9 advances in the engaging groove 5 . as a result , as shown in fig1 , the tip section 4 a of the insertion hole 4 nips the biopsy cup 103 with far stronger force than before engagement , while keeping point contact with the biopsy cup 103 . as a result , the marker 1 is securely fixed to the biopsy cup 103 , and forward and backward movement of the biopsy cup 103 within the guide sheath 7 is prevented . in the state in which the marker 1 and the stick 9 are engaged together , the biopsy cup 103 is projected only the same distance as that of the ultrasonic probe 102 in step s 2 from the tip of the sheath body 8 , and the tip of the biopsy cup 103 reliably reaches the target site r as shown in fig1 . here , in step s 5 , the biopsy cup 103 is operated to take tissue samples at the target site r . after taking the tissue samples , the biopsy cup 103 is removed and the tissue samples are collected . taking tissue samples in step s 5 may be repeated several times when needed . it is also possible to estimate the size ( i . e ., the length along the direction in which the bronchiole 101 extends ) of the target site r by repeating taking tissue samples several times with the position of the marker 1 fine - controlled and moving the tip of the biopsy cut 103 forward and backward in order to specify the position at which no more tissue sample can be taken . the steps shown in fig5 are not necessarily performed in the described order . instead , a projecting length of the biopsy cup 103 from the guide sheath 7 may be determined in advance , the marker 1 may be attached at a predetermined position on the biopsy cup 103 so that the biopsy cup 103 projects at the predetermined length , and then the guide sheath 7 may be disposed such that the distance between the tip of the ultrasonic probe 102 and the tip of the guide sheath 7 equals the above predetermined length while observing via x - ray radioscopy . in step s 1 , instead of providing the ultrasonic probe 102 , the biopsy cup 103 inserted in the guide sheath may be advanced to the target site r . alternatively , the guide sheath 7 alone may be advanced to the target site . x - ray radioscopy , a ultrasonic image or an endoscope image may be suitably selected for guiding instruments to the target site r . the marker 1 is attached to the biopsy cup 103 before the biopsy cup 103 is inserted in the guide sheath 7 , but the marker 1 is not necessarily engaged and fixed to the stick 9 immediately after the ultrasonic probe 102 is removed . for example , the marker 1 may be engaged with the stick 9 when the tip of the biopsy cup 103 is positioned under x - ray radioscopy , thereby positioning and engagement may occur at the same time . according to the marker 1 of the present embodiment , the positional relationship between the biopsy cup 103 and the guide sheath 7 is fixed when the engaging groove 5 of the engaging portion 3 engages the guide sheath 7 . in this manner , the tip of the biopsy cup 103 can be projected precisely by the predetermined amount . thus , the tip of the biopsy cup 103 can reliably reach the target site r , thereby performing a precise biopsy . the marker 1 is slidably fixed to the biopsy cup 103 in the axial direction thereof due to frictional force between the inner surface of the tip section 4 a of the insertion hole 4 and the outer surface of the biopsy cup 103 . thus , the projecting length of the biopsy cup 103 from the guide sheath 7 can be controlled as intended by changing the position at which the marker 1 is fixed to the biopsy cup 103 . the marker 1 and the biopsy cup 103 are in contact with each other not in the entire inner surface of the insertion hole 4 , but only in the inner surface of the tip section 4 a . further , since the tip section 4 a is square - sectioned as described above , the tip section 4 a is made to point contact with the biopsy cup 103 only at four sides 4 d . thus , since the marker 1 is structured to have a smaller contact area with the biopsy cup 103 to be attached to , the frictional force generated between the marker 1 and the biopsy cups 103 in the axial direction is small , whereby the marker 1 can be slid smoothly for positional alignment . the marker 1 is engaged with the stick 9 of the guide sheath 7 such that , as the stick 9 advances in the engaging groove 5 , the second surface 5 b of the engaging groove 5 is pressed against the insertion hole 4 due to a difference in taper angles as described above . thus , the marker 1 is firmly fixed to the biopsy cup 103 , and the positional relationship with the guide sheath 7 in operation including taking tissue samples is reliably maintained . in this manner , a marker which slides smoothly for positional alignment and is firmly fixed for engagement can be obtained . in addition , since the flange 6 is provided in the engaging portion 3 , even if the external surface of the body 2 is drawn toward the rear end side due to deformation at the time of engagement with the stick 9 , the flange 6 moves toward the radial direction inner side , the movement of the entire external surface of the body 2 can be prevented . therefore , a marker with holding performance which is not easily decline during engagement can be obtained . while the embodiments of the invention have been described , the technical range of the invention is not limited to those described . various modifications may be made without departing from the scope of the invention . in the described embodiment , although the marker 1 includes the engaging portion 3 and is engaged with the base end of the guide sheath 7 , an abutting portion may be provided instead of the engaging portion 3 for abutting the base end of the guide sheath 7 . in particular , if the engaging groove 5 is not provided in the marker 1 , a front end surface of the body 2 abuts the base end of the guide sheath 7 and functions as the abutting portion . in this manner , when the endoscopic treatment tool with the marker attached thereon is inserted in the guide sheath and the abutting portion is made to abut the base end of the guide sheath , a predetermined length of the tip of the endoscopic treatment tool can always be projected from the tip of the guide sheath . in the described embodiment , although the marker 1 is fixed slidably in the axial direction of the endoscopic treatment tool by the inner surface of the insertion hole 4 , the invention is not limited thereto . for example , the marker 1 may be removably fixed at an intended position by nipping the endoscopic treatment tool like a clip . in addition , neither the engaging portion nor the abutting portion is indispensable . so long as the marker is fixed to a predetermined position of the endoscopic treatment tool , when the guide sheath is inserted to the position of the marker , a predetermined length of the tip of the endoscopic treatment tool can always be projected from the tip of the guide sheath . in addition , in the described embodiment , although the marker is attached to the endoscopic treatment tool such as the biopsy cup for taking tissue samples , the invention is not limited thereto . the marker may be attached to any treatment tools that are difficult to locate in a body . for example , the marker of the invention may be attached to an ultrasonic probe for reliable ultrasonic image diagnosis in a position repeatedly .
a marker to be attached to an endoscopic treatment tool for precisely directing a tip of the treatment tool to a target site with no additional physical burden to the patient is provided . a marker 1 used in an endoscopic treatment tool to be inserted in a guide sheath , the marker including : a body 2 ; and a tip section 4 a for removably fixing the body 2 to a middle section of the endoscopic treatment tool , wherein the distance between the body 2 and a tip of the endoscopic treatment tool can be determined freely .