Abstract:
An optical probe, comprising:
       a sheath to be inserted into a body cavity;   an optical fiber inside the sheath;   an optical component attached to a distal end portion of the optical fiber inside the sheath;   wherein a light beam transmitted through the optical fiber is emitted from the optical component toward a body tissue in the body cavity, and   wherein the sheath comprises   a plurality of balloons spaced at predetermined intervals on a part on the distal end portion side of an outer periphery and capable of inflating/deflating in a radial direction orthogonal to a longitudinal axis,   a suction inlet located between the plurality of balloons to draw the body tissue at the part on the distal end portion side of the outer periphery by suction,   a balloon inflation port connected to the balloons, and   a suction port connected to the suction inlet, and   the plurality of balloons are airtightly locked to an body cavity inner wall by supplying a fluid or a gas through the balloon inflation port to pressurize and inflate the balloons, and pressure in a space formed between the plurality of locked balloons and the body cavity inner wall is reduced through the suction port to cause the body tissue to adhere strongly to the part on the distal end portion side of the outer periphery by suction.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    1. Field of the Invention 
         [0002]    The present invention relates to an optical probe for acquiring an optical coherent tomographic image of the interior of a body cavity, a drive control method for the optical probe, and an endoscope apparatus and, more particularly, to an optical probe which stably transmits and receives a measuring light beam in a lumen, a drive control method for the optical probe, and an endoscope apparatus. 
         [0003]    2. Description of the Related Art 
         [0004]    Conventionally, diagnostic imaging that includes rendering a tomographic image of a living body by inserting an optical probe into a body cavity of a blood vessel, a bile duct, a pancreatic duct, a stomach, an esophagus, or the large intestine and performing radial scanning has been widely performed. As an example, an optical coherent tomography (OCT) apparatus which, when a probe which incorporates an optical fiber having an optical lens and an optical mirror attached to its distal end is inserted in a body cavity, emits a light beam into the body cavity while performing radial scanning using the optical mirror arranged on the distal end side of the optical fiber and renders a cross-sectional image of the body cavity on the basis of a light beam reflected from a tissue is used. 
         [0005]    Excellent features of OCT include the capability to render a tomographic image with a resolution of 10 μm. In order to take advantage of the feature, fluctuations in the positional relationship with a target body tissue need to be prevented. As shown in  FIG. 14 , a sheath  901  of an OCT probe  900  is brought into contact with a lumen inner wall  902 , and a measuring light beam is applied from a ball lens  904  which is provided at the distal end of a shaft  903  incorporating a fiber (not shown) by radial scanning (or spiral scanning). 
         [0006]    However, when the interior of a body cavity is observed by OCT, the positional relationship between the OCT probe  900  and a body tissue varies during the observation due to beating or pulsation of the body tissue, movement of the hands of an operator, or the like, the above-described feature of OCT cannot be taken advantage of. Accordingly, there is strong demand for fixation of the relative positional relationship between the OCT probe  900  and a body tissue. 
         [0007]    To meet this demand, an OCT system in which a balloon is provided at the distal end of an OCT probe, and the OCT probe is fixed to a body tissue by inflation of the balloon is proposed (Japanese Patent Application Laid-Open No. 2007-75403). 
         [0008]    However, the OCT system disclosed in Japanese Patent Application Laid-Open No. 2007-75403, which fixes the OCT probe to a body cavity by inflating the balloon, suffers from the following problems: 
         [0000]    1) a part to be observed is away from the center of the probe and has an unobservable area; and
 
2) the spacing between scan lines for a part away from the center is large in radial scanning, and the quality of an image of the part is low.
 
         [0009]    More specifically, the above-described OCT system of Japanese Patent Application Laid-Open No. 2007-75403, which fixes the OCT probe to a body cavity by inflating the balloon, cannot display an image of a part away from the OCT probe because OCT, in principle, has a shallow displayable depth equal to a coherence length of about 3 mm. Additionally, since a measuring light beam is radially emitted in radial scanning, the spacing between scan lines for a part away from the center is large, and the quality of an image of the part is low. 
       SUMMARY OF THE INVENTION 
       [0010]    The present invention has been made in consideration of the circumstances, and has as its object to provide an optical probe capable of stably locking an OCT probe in a body cavity and acquiring a blur-free tomographic image with high resolution, a drive control method for the optical probe, and an endoscope apparatus. 
         [0011]    In order to achieve the above-described object, an optical probe according to a first aspect of the present invention is an optical probe, comprising: 
         [0012]    a sheath to be inserted into a body cavity; 
         [0013]    an optical fiber inside the sheath; 
         [0014]    an optical component attached to a distal end portion of the optical fiber inside the sheath; 
         [0015]    wherein a light beam transmitted through the optical fiber is emitted from the optical component toward a body tissue in the body cavity, and 
         [0016]    wherein the sheath comprises a plurality of balloons spaced at predetermined intervals on a part on the distal end portion side of an outer periphery and capable of inflating/deflating in a radial direction orthogonal to a longitudinal axis, 
         [0017]    a suction inlet located between the plurality of balloons to draw the body tissue at the part on the distal end portion side of the outer periphery by suction, 
         [0018]    a balloon inflation port connected to the balloons, and 
         [0019]    a suction port connected to the suction inlet, and 
         [0020]    the plurality of balloons are airtightly locked to an body cavity inner wall by supplying a fluid or a gas through the balloon inflation port to pressurize and inflate the balloons, and pressure in a space formed between the plurality of locked balloons and the body cavity inner wall is reduced through the suction port to cause the body tissue to adhere strongly to the part on the distal end portion side of the outer periphery by suction. 
         [0021]    In the optical probe according to the first aspect, the plurality of balloons are airtightly locked to the body cavity inner wall by supplying the fluid through the balloon inflation port to pressurize and inflate the balloons, and the pressure in the space formed between the plurality of locked balloons and the body cavity inner wall is reduced through the suction port to cause the body tissue to adhere strongly to the part on the distal end portion side of the outer periphery by suction. This configuration makes it possible to stably lock an OCT probe in a body cavity and acquire a blur-free tomographic image with high resolution. 
         [0022]    As in the case of an optical probe according to a second aspect of the present invention, the optical probe according to the first aspect is preferably configured such that the balloon inflation port and the suction port are provided at a proximal end portion of the sheath. 
         [0023]    As in the case of an optical probe according to a third aspect of the present invention, the optical probe according to one of the first and second aspects is preferably configured such that the optical fiber is arranged in a drive shaft which rotatably drives the optical fiber, and radial scanning is performed in the body cavity by rotatably driving the optical component. 
         [0024]    As in the case of an optical probe according to a fourth aspect of the present invention, the optical probe according to the third aspect is preferably configured such that the drive shaft is also movable in a longitudinal direction, and spiral scanning is performed in the body cavity by rotatably driving the optical component and driving the optical component back and forth within a longitudinal driving range. 
         [0025]    As in the case of an optical probe according to a fifth aspect of the present invention, the optical probe according to any one of the first to fourth aspects is preferably configured such that the optical component comprises a ball lens having a reflecting surface which bends a traveling direction of the light beam transmitted through the optical fiber almost at a right angle. 
         [0026]    As in the case of an optical probe according to a sixth aspect of the present invention, the optical probe according to any one of the first to fifth aspects is preferably configured such that the optical fiber transmits wavelength swept laser light into the body cavity. 
         [0027]    As in the case of an optical probe according to a seventh aspect of the present invention, the optical probe according to any one of the first to sixth aspects is preferably configured such that the balloons are each thicker at two end portions than at a central portion. 
         [0028]    As in the case of an optical probe according to an eighth aspect of the present invention, the optical probe according to any one of the first to seventh aspects preferably further comprises a fluid supply control device which detects internal pressure of each of the balloons and controls supply of the fluid through the balloon inflation port in order to keep the balloon airtightly locked to the body cavity inner wall. 
         [0029]    As in the case of an optical probe according to a ninth aspect of the present invention, the optical probe according to any one of the first to eighth aspects is preferably configured such that the fluid is one of an X-ray contrast medium and a fluid containing an X-ray contrast medium. 
         [0030]    As in the case of an optical probe according to a tenth aspect of the present invention, the optical probe according to any one of the first to eighth aspects is preferably configured such that the fluid is saline. 
         [0031]    As in the case of an optical probe according to an 11th aspect of the present invention, the optical probe according to any one of the first to tenth aspects is preferably configured such that the optical fiber transmits wavelength swept laser light into the body cavity. 
         [0032]    A drive control method for an optical prove according to a 12th aspect of the present invention is a drive control method for an optical probe which comprises an optical fiber and an optical component attached to a distal end portion of the optical fiber inside a sheath to be inserted into a body cavity and emits a light beam transmitted through the optical fiber from the optical component toward a body tissue in the body cavity, the optical probe further comprising a longitudinal drive section which drives the optical component in a longitudinal direction of a longitudinal axis of the sheath in the sheath, the sheath comprising a plurality of balloons spaced at predetermined intervals on a part on the distal end portion side of an outer periphery and capable of inflating/deflating in a radial direction orthogonal to the longitudinal axis, a suction inlet located between the plurality of balloons to draw the body tissue at the part on the distal end portion side of the outer periphery by suction, a balloon inflation port connected to the balloons, and a suction port connected to the suction inlet, comprising a locking step of airtightly locking the plurality of balloons to an body cavity inner wall by supplying a fluid or a gas through the balloon inflation port to pressurize and inflate the balloons and an adhesion step of reducing pressure in a space formed between the plurality of locked balloons and the body cavity inner wall through the suction port to cause the body tissue to adhere strongly to the part on the distal end portion side of the outer periphery by suction. 
         [0033]    As in the case of a drive control method for an optical probe according to a 13th aspect of the present invention, the drive control method for the optical probe according to the 12th aspect preferably further comprises a fluid supply control step of detecting internal pressure of each of the balloons and controlling supply of the fluid through the balloon inflation port in order to keep the balloon airtightly locked to the body cavity inner wall. 
         [0034]    An endoscope apparatus according to a 14th aspect of the present invention comprises an optical probe according to any one of the first to 11th aspects and an endoscope having a treatment tool channel which is inserted through the sheath of the optical probe. 
         [0035]    As has been described above, the present invention has the advantage of the capability to stably lock an OCT probe in a body cavity and acquire a blur-free tomographic image with high resolution. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0036]      FIG. 1  is a block diagram showing the internal configurations of an OCT probe and an OCT processor according to an embodiment of the present invention; 
           [0037]      FIG. 2  is a cross-sectional view showing the configuration of an optical rotary joint to which a rotating-side optical fiber in  FIG. 1  is connected; 
           [0038]      FIG. 3  is a longitudinal cross-sectional view showing the configuration of the OCT probe in  FIG. 1 ; 
           [0039]      FIG. 4  is a cross-sectional view showing a cross section taken along line A-A in  FIG. 3 ; 
           [0040]      FIG. 5  is a cross-sectional view showing a cross section taken along line B-B in  FIG. 3 ; 
           [0041]      FIG. 6  is a cross-sectional view showing a cross section taken along line C-C in  FIG. 3 ; 
           [0042]      FIG. 7  is a cross-sectional view showing a cross section taken along line D-D in  FIG. 3 ; 
           [0043]      FIG. 8  is a cross-sectional view showing a cross section taken along line E-E in  FIG. 3 ; 
           [0044]      FIG. 9  is a view showing the configuration of each balloon in  FIG. 3 ; 
           [0045]      FIG. 10  is a flow chart for explaining the operation of the OCT processor in relation to the OCT probe in  FIG. 3 ; 
           [0046]      FIG. 11  is a schematic view of a case where the interior of a body cavity is observed by the OCT probe in the process in  FIG. 10 ; 
           [0047]      FIG. 12  is a longitudinal cross-sectional view showing the configuration of a modification of the OCT probe in  FIG. 1 ; 
           [0048]      FIG. 13  is a view showing a diagnostic imaging apparatus used in combination with an endoscope apparatus, to which the OCT probe in  FIG. 1  can be applied; and 
           [0049]      FIG. 14  is a view showing how a conventional OCT probe is inserted in a body cavity. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0050]    An embodiment of the present invention will be described in detail below with reference to the accompanying drawings.  FIG. 1  is a block diagram showing the internal configurations of an OCT probe and an OCT processor according to the embodiment of the present invention. 
         [0051]    As shown in  FIG. 1 , an OCT probe  600  and an OCT processor  400  according to this embodiment are intended to acquire an optical tomographic image of an object to be measured by an optical coherence tomography (OCT) measurement method. 
         [0052]    The OCT processor  400  includes a first light source (first light source unit)  12  which emits a light beam La for measurement, an optical fiber coupler (demultiplexing and multiplexing section)  14  which demultiplexes the light beam La emitted from the first light source  12  into a measuring light beam (first rays of light) L 1  and a reference light beam L 2  and multiplexes a return light beam L 3  from an object S to be measured serving as a test object and the reference light beam L 2  to produce interfering light beams L 4  and L 5 , the OCT probe  600  comprising a rotating-side optical fiber FB 1  which guides the measuring light beam L 1  obtained through demultiplexing by the optical fiber coupler  14  to the object to be measured and guides the return light beam L 3  from the object to be measured, a fixed-side optical fiber FB 2  which guides the measuring light beam L 1  to the rotating-side optical fiber FB 1  and guides the return beam L 3  guided by the rotating-side optical fiber FB 1 , an optical connector  18  which rotatably connects the rotating-side optical fiber FB 1  to the fixed-side optical fiber FB 2  and transmits the measuring light beam L 1  and the return light beam L 3 , an interfering light detection section  20  which detects the interfering light beams L 4  and L 5  produced by the optical fiber coupler  14  as interference signals, and a processing section  22  which processes the interference signals detected by the interfering light detection section  20  and acquires optical structure information. An image is displayed on a monitor device  500  on the basis of the optical structure information acquired by the processing section  22 . 
         [0053]    The OCT processor  400  also includes a second light source (second light source unit)  13  which emits an aiming light beam (second rays of light) Le for indicating a measurement mark, an optical path length adjustment section  26  which adjusts the optical path length of the reference light beam L 2 , an optical fiber coupler  28  which splits the light beam La emitted from the first light source  12 , detection sections  30   a  and  30   b  which detect the interfering light beams L 4  and L 5  obtained through multiplexing by the optical fiber coupler  14 , and an operation control section  32  which inputs various conditions to the processing section  22 , changes settings, and performs other processes. 
         [0054]    Note that various optical fibers FB including the rotating-side optical fiber FB 1  and the fixed-side optical fiber FB 2  (FB 3 , FB 4 , FB 5 , FB 6 , FB 7 , FB 8 , and the like) are used as light paths for guiding and transmitting various light beams including the emitted light beam La, the aiming light beam Le, the measuring light beam L 1 , the reference light beam L 2 , and the return light beam L 3  described above between components such as the optical devices in the OCT processor  400  shown in  FIG. 1 . 
         [0055]    The first light source  12  emits light for OCT measurement (e.g., laser light with a wavelength of 1.3 μm or low-coherence light). The first light source  12  is a light source which emits the laser light beam La with, e.g., a center wavelength of 1.3 μm in the infrared region while periodically sweeping the frequency of the light beam. The first light source  12  includes a light source  12   a  which emits the laser light beam or low-coherence light beam La and a lens  12   b  which focuses the light beam La emitted from the light source  12   a . Although the details will be described later, the light beam La emitted from the first light source  12  passes through the optical fibers FB 4  and FB 3  and is split into the measuring light beam L 1  and the reference light beam L 2  by the optical fiber coupler  14 , and the measuring light beam L 1  is inputted to the optical connector  18 . 
         [0056]    The second light source  13  emits visible light as the aiming light beam Le for facilitating confirmation of a part to be measured. For example, red semiconductor laser light with a wavelength of 0.66 μm, He—Ne laser light with a wavelength of 0.63 μm, blue semiconductor laser light with a wavelength of 0.405 μm, or the like can be used as the aiming light beam Le. The second light source  13  includes a semiconductor laser  13   a  which emits, e.g., red, blue, or green laser light and a lens  13   b  which focuses the aiming light beam Le emitted from the semiconductor laser  13   a . The aiming light beam Le emitted from the second light source  13  is inputted to the optical connector  18  through the optical fiber FB 8 . 
         [0057]    At the optical connector  18 , the measuring light beam L 1  and the aiming light beam Le are multiplexed, and a resultant light beam is guided to the rotating-side optical fiber FB 1  in the OCT probe  600 . 
         [0058]    The optical fiber coupler (demultiplexing and multiplexing section)  14  is composed of, e.g., a 2×2 optical fiber coupler and is optically connected to the fixed-side optical fiber FB 2 , the optical fiber FB 3 , the optical fiber FB 5 , and the optical fiber FB 7 . 
         [0059]    The optical fiber coupler  14  splits the light beam La incident from the first light source  12  through the optical fibers FB 4  and FB 3  into the measuring light beam (first rays of light) L 1  and the reference light beam L 2  and causes the measuring light beam L 1  to enter the fixed-side optical fiber FB 2  and the reference light beam L 2  to enter the optical fiber FB 5 . 
         [0060]    The optical fiber coupler  14  also multiplexes the light beam L 2 , which is inputted to the optical fiber FB 5 , is frequency shifted and changed in optical path length by the optical path length adjustment section  26  (to be described later), and is returned through the optical fiber FB 5 , and the light beam L 3 , which is acquired by the OCT probe  600  and is guided from the fixed-side optical fiber FB 2  and emits a resultant light beam to the optical fiber FB 3  (FB 6 ) and the optical fiber FB 7 . 
         [0061]    The OCT probe  600  is connected to the fixed-side optical fiber FB 2  through the optical connector  18 . The measuring light beam L 1  from the fixed-side optical fiber FB 2  is multiplexed with the aiming light beam Le and is inputted to the rotating-side optical fiber FB 1  through the optical connector  18 . The inputted measuring light beam L 1  multiplexed with the aiming light beam Le is transmitted by the rotating-side optical fiber FB 1  and is applied to the object S to be measured. The return light beam L 3  from the object S to be measured is acquired, and the acquired return light beam L 3  is transmitted by the rotating-side optical fiber FB 1  and is emitted to the fixed-side optical fiber FB 2  through the optical connector  18 . 
         [0062]    The optical connector  18  multiplexes the measuring light beam (first rays of light) L 1  and the aiming light beam (second rays of light) Le. 
         [0063]    The interfering light detection section  20  is connected to the optical fiber FB 6  and the optical fiber FB 7  and detects the interfering light beams L 4  and L 5 , which are produced by multiplexing the reference light beam L 2  and the return light beam L 3  in the optical fiber coupler  14 , as interference signals. 
         [0064]    The OCT processor  400  has the detector  30   a , which is provided on the optical fiber FB 6  diverging from the optical fiber coupler  28  and detects the light intensity of the interfering light beam L 4 , and the detector  30   b  on an optical path of the optical fiber FB 7 , which detects the light intensity of the interfering light beam L 5 . 
         [0065]    The interfering light detection section  20  detects the intensity of reflected light (or backscattered light) at each depth position of the object S to be measured by Fourier-transforming the interfering light beam L 4  detected from the optical fiber FB 6  and the interfering light beam L 5  detected from the optical fiber FB 7  on the basis of detection results from the detectors  30   a  and  30   b.    
         [0066]    The processing section  22  acquires optical structure information from the interference signals extracted by the interfering light detection section  20 . The processing section  22  generates an optical three-dimensional structure image on the basis of the acquired optical structure information and outputs an image obtained by subjecting the optical three-dimensional structure image to various processes to the monitor device  500 . 
         [0067]    The optical path length adjustment section  26  is arranged on the side where the reference light beam L 2  is emitted from the optical fiber FB 5  (i.e., at the end opposite to the optical fiber coupler  14  of the optical fiber FB 5 ). 
         [0068]    The optical path length adjustment section  26  includes a first optical lens  80  which collimates a light beam emitted from the optical fiber FB 5 , a second optical lens  82  which focuses the light beam collimated by the first optical lens  80 , a reflecting mirror  84  which reflects the light beam focused by the second optical lens  82 , a base  86  which supports the second optical lens  82  and the reflecting mirror  84 , and a mirror transfer mechanism  88  which moves the base  86  in a direction parallel to an optical axis direction. The optical path length adjustment section  26  adjusts the optical path length of the reference light beam L 2  by changing the distance between the first optical lens  80  and the second optical lens  82 . 
         [0069]    The first optical lens  80  collimates the reference light beam L 2  emitted from a core of the optical fiber FB 5  and focuses the reference light beam L 2  reflected by the reflecting mirror  84  onto the core of the optical fiber FB 5 . 
         [0070]    The second optical lens  82  focuses the reference light beam L 2  collimated by the first optical lens  80  onto the reflecting mirror  84  and collimates the reference light beam L 2  reflected by the reflecting mirror  84 . As described above, the first optical lens  80  and the second optical lens  82  constitute a confocal optical system. 
         [0071]    The reflecting mirror  84  is arranged at the focal point of a light beam focused by the second optical lens  82  and reflects the reference light beam L 2  focused by the second optical lens  82 . 
         [0072]    With the above-described configuration, the reference light beam L 2  emitted from the optical fiber FB 5  is collimated by the first optical lens  80  and is focused onto the reflecting mirror  84  by the second optical lens  82 . After that, the reference light beam L 2  reflected by the reflecting mirror  84  is collimated by the second optical lens  82  and is focused onto the core of the optical fiber FB 5  by the first optical lens  80 . 
         [0073]    The base  86  fixedly holds the second optical lens  82  and the reflecting mirror  84 . The mirror transfer mechanism  88  moves the base  86  in an optical axis direction of the first optical lens  80  (a direction indicated by an arrow A in  FIG. 1 ). 
         [0074]    Movement of the base  86  in the direction indicated by the arrow A effected by the mirror transfer mechanism  88  changes the distance between the first optical lens  80  and the second optical lens  82 . This allows adjustment of the optical path length of the reference light beam L 2 . 
         [0075]    The operation control section  32  includes an input device such as a keyboard or a mouse and a control device which manages various conditions on the basis of entered information and is connected to the processing section  22 . The operation control section  32  performs, e.g., inputting of various processing conditions and the like to the processing section  22  and setting and change of the processing conditions in the processing section  22  in accordance with an operator&#39;s instructions entered from the input device. 
         [0076]    Note that the operation control section  32  may display an operation screen on the monitor device  500  or display an operation screen on a separately provided display section. The operation control section  32  may be configured to control the operation of the first light source  12 , the second light source  13 , the optical connector  18 , the interfering light detection section  20 , the optical path length adjustment section  26 , and the detection sections  30   a  and  30   b  and set various conditions for the components. 
         [0077]    As shown in  FIG. 2 , the rotating-side optical fiber FB 1  and the fixed-side optical fiber FB 2  are connected by the optical connector  18 . The optical fibers FB 1  and FB 2  are optically connected such that rotation of the rotating-side optical fiber FB 1  is not transmitted to the fixed-side optical fiber FB 2 . The rotating-side optical fiber FB 1  is arranged to be rotatable with respect to a sheath  681  and be movable in a longitudinal direction of the sheath  681 . 
         [0078]    A torque transmission coil  624  is fixed to an outer periphery of the rotating-side optical fiber FB 1 . The rotating-side optical fiber FB 1  and the torque transmission coil  624  are connected to an optical rotary joint (not shown) in the optical connector  18 . 
         [0079]    In the OCT probe  600 , the rotating-side optical fiber FB 1 , the torque transmission coil  624 , and a ball lens  680  (see  FIG. 1 ) as an optical component are configured to be movable in the sheath  681  both in a direction indicated by an arrow S 1  (a direction toward a forceps outlet) and in a direction indicated by an arrow S 2  (a direction toward a distal end of the sheath  681 ) by a forward and reverse drive section (to be described later) which is provided at the optical connector  18 . 
         [0080]    The sheath  681  is fixed to a fixed member  670 . In contrast, the rotating-side optical fiber FB 1  and the torque transmission coil  624  are connected to a rotary cylinder  656 . The rotary cylinder  656  is configured to rotate in accordance with rotation of a motor  652  transmitted through a gear  654 . The rotary cylinder  656  is connected to the optical rotary joint of the optical connector  18 . The measuring light beam L 1  and the return light beam L 3  are transmitted between the rotating-side optical fiber FB 1  and the fixed-side optical fiber FB 2  through the optical connector  18 . 
         [0081]    A frame  650  incorporating the components includes a support member  662 . The support member  662  has a tapped hole (not shown). The frame  650  occludes with a ball screw  664  for forward and reverse movement at the tapped hole (not shown) of the support member  662 . The ball screw  664  for forward and reverse movement connects with a motor  660 . The tapped hole, the ball screw  664  for forward and reverse movement, the motor  660 , and the like constitute the forward and reverse drive section as a forward and reverse movement device. 
         [0082]    The forward and reverse drive section for the optical rotary joint of the optical connector  18  moves the frame  650  back and forth by rotatable driving of the motor  660 . With the forward and reverse movement, the forward and reverse drive section is capable of moving the rotating-side optical fiber FB 1 , the torque transmission coil  624 , the fixed member  670 , and the ball lens  680  in the directions S 1  and S 2  in  FIG. 2 . 
         [0083]    Note that the motor  660  performs forward and reverse driving in predetermined steps (e.g., 1 mm steps). At each predetermined step, the motor  652  rotates the rotating-side optical fiber FB 1 , the torque transmission coil  624 , and the ball lens  680  once, thereby applying the measuring light beam L 1  to the object S to be measured for radial scanning. 
         [0084]    In the OCT probe  600  with the above-described configuration, the rotating-side optical fiber FB 1  and the torque transmission coil  624  are rotated in a direction indicated by an arrow R in  FIG. 2  by the optical rotary joint of the optical connector  18 . With the rotation, the OCT probe  600  applies the measuring light beam L 1  emitted from the ball lens  680  to the object S to be measured while performing radial scanning in the direction indicated by the arrow R (a circumferential direction of the sheath  681 ) and acquires the return light beam L 3 . 
         [0085]    For this reason, at each angle along the circumferential direction of the sheath  681 , a desired part of the object S to be measured can be accurately captured, and the return light beam L 3  reflected from the object S to be measured can be acquired. 
         [0086]    When a plurality of pieces of optical structure information are to be acquired to generate an optical three-dimensional structure image, the ball lens  680  is first moved to an end of a movable range in the direction indicated by the arrow S 1  in  FIG. 2  by the forward and reverse drive section for the optical rotary joint of the optical connector  18 . The ball lens  680  moves in the direction S 2  in predetermined steps to the other end of the movable range while acquiring pieces of optical structure information composed of tomographic images or the ball lens  680  alternates between acquisition of optical structure information and movement in the direction S 2  in  FIG. 2  in predetermined steps until the ball lens  680  reaches the other end of the movable range. 
         [0087]    As described above, the OCT probe  600  and the OCT processor  400  according to this embodiment are capable of acquiring a plurality of pieces of optical structure information for a desired range of the object S to be measured and acquiring an optical three-dimensional structure image on the basis of the plurality of acquired pieces of optical structure information. 
         [0088]    More specifically, the OCT probe  600  and the OCT processor  400  acquire a piece of optical structure information in a depth direction of the object S to be measured (a first direction) from interference signals. The OCT probe  600  and the OCT processor  400  are capable of acquiring a piece of optical structure information on a scan plane formed by the depth direction of the object S to be measured (the first direction) and a direction almost perpendicular to the depth direction (a second direction) by radial scanning of the object S to be measured in the direction indicated by the arrow R in  FIG. 2  (the circumferential direction of the sheath  681 ) and are further capable of acquiring a plurality of pieces of optical structure information for generating an optical three-dimensional structure image by moving the scan plane along a direction almost perpendicular to the scan plane (a third direction). 
         [0089]    A diagnostic imaging apparatus according to the embodiment of the present invention will be described in detail below with reference to the drawings.  FIG. 3  is a schematic cross-sectional view of the OCT probe in  FIG. 1 .  FIGS. 4 to 8  are cross-sectional views showing cross sections at points (a cross section taken along line A-A, a cross section taken along line B-B, a cross section taken along line C-C, a cross section taken along line D-D, and a cross section taken along line E-E) in  FIG. 3 .  FIG. 9  is a view showing the configuration of each balloon in  FIG. 3 . 
         [0090]    As described above, the OCT probe  600  performs radial scanning while rotating the ball lens  680  by rotating the torque transmission coil  624  arranged outside the rotating-side optical fiber FB 1  with the ball lens  680  at its distal end. At the same time, the OCT probe  600  performs longitudinal scanning by means of the forward and reverse drive section for the optical rotary joint of the optical connector  18 . This allows spiral scanning. A combination of the rotating-side optical fiber FB 1 , the torque transmission coil  624 , and the ball lens  680  will be referred to as an image core hereinafter. 
         [0091]    The sheath  681  incorporates the extending image core and includes two cylindrical balloons  700  and  701  which are respectively arranged before and behind a longitudinal scan range at a distal end portion. The balloons  700  and  701  are connected to a balloon inflation port  710  which is provided at a proximal section  681 A of the sheath  681 . Although not shown, saline, an X-ray contrast medium, or gas such as air or carbon dioxide is injected into the balloons  700  and  701  by a pressure device (not shown) such as a syringe with lock or an indeflator through the balloon inflation port  710  to increase or reduce the pressures in the balloons  700  and  701 . In the sheath  681 , the balloons  700  and  701  can be inflated and deflated by increasing and reducing the pressures in the balloons  700  and  701  under control of a pressure control section  410  (see  FIG. 1 ) in the OCT processor  400 . Note that the X-ray contrast medium may be used in undiluted form or may be diluted with saline. 
         [0092]    The balloons  700  and  701  are made of a flexible material such as silicone rubber and are configured to closely fit microscopic asperities on the surface of a living body when they are inflated. Although silicone rubber is used here, the present invention is not limited to the material. Any other material such as latex rubber or nylon may be used as long as the material meets the requirement. 
         [0093]    As will be described later, the OCT probe  600  is used while a space between the two balloons  700  and  701  is under negative pressure, after the balloons  700  and  701  are inflated. In order to reduce deformation of the balloons  700  and  701  attracted to each other in this case, two end portions of each of the balloons  700  and  701  are formed as thick-wall portions  720 , and a central portion is formed as a thin-wall portion  721 , as shown in  FIG. 9 . It is desirable that the flexibility of each of the balloons  700  and  701  is enhanced at the thin-wall portion  721  to improve the ability to closely fit a luminal tissue in a radial direction with respect to a rotation axis of the OCT probe  600  and that the flexibility of the balloon  700  and  701  is lowered at the thick-wall portions  720  on both sides (in a longitudinal direction) to reduce deformation. 
         [0094]    A plurality of suction inlets  712  are formed in the sheath  681  between the two balloons  700  and  701 . Each suction inlet  712  is connected to a suction port  714  of the proximal section  681 A through a communication channel  750  (see  FIGS. 7 and 8 ). In the sheath  681 , connection of a vacuum pump (not shown) to the suction port  714  allows suction through the suction inlets  712  under control of the pressure control section  410  (see  FIG. 1 ) in the OCT processor  400 . 
         [0095]    The procedure from when the OCT probe  600  is inserted into an affected part to when the OCT processor  400  acquires a tomographic image will be described below using the flow chart in  FIG. 10  with reference to  FIG. 11 .  FIG. 10  is a flow chart for explaining the operation of the OCT processor in relation to the OCT probe.  FIG. 11  is a schematic view of a case where the interior of a body cavity is observed by the OCT probe in the process in  FIG. 10 . 
         [0096]    When the OCT probe  600  is to be inserted into a body cavity, it is for example inserted into a coelomic tissue of a bile duct, a pancreatic duct, the large intestine, or the like through a forceps outlet of an endoscope (not shown) and is advanced to a lesioned part, as in the case of a common OCT probe. 
         [0097]    As shown in  FIG. 10 , when the distal end of the sheath  681  of the OCT probe  600  reaches a part to be examined (observed), the OCT processor  400  injects saline or an X-ray contrast medium into the balloons  700  and  701  through the balloon inflation port  710  by the pressure device (not shown) and pressurizes the balloons  700  and  701  under control of the pressure control section  410 . With the injection of the saline or the X-ray contrast medium, the balloons  700  and  701  inflate, and the OCT probe  600  is airtightly locked and fixed to a body cavity inner wall  800  through the balloons  700  and  701  (step S 1 ). At this time, the body cavity is prevented from inflating excessively due to the inflation of the balloons  700  and  701 . 
         [0098]    In a part observable by endoscopy, such as the large intestine, a fluid such as saline may be injected into the balloons  700  and  701 . If the OCT probe  600  is inserted into a part unobservable by endoscopy, such as a bile duct or a pancreatic duct, observation is performed under fluoroscopy. Where and how the OCT probe  600  is inserted and the shapes of the balloons  700  and  701  can be observed by injecting an X-ray contrast medium into the balloons  700  and  701 . 
         [0099]    The OCT processor  400  performs depressurization through the suction port  714  (see  FIG. 3 ) of the proximal section  681 A by means of the vacuum pump (not shown) under control of the pressure control section  410 . With the depressurization, the OCT processor  400  draws a body tissue  801  at the part to be observed through the suction inlets  712  at the distal end portion of the sheath  681  by suction such that the body tissue  801  adheres strongly to the OCT probe  600  (step S 2 ). 
         [0100]    The OCT processor  400  monitors the balloons  700  and  701  by means of the pressure control section  410 . When the body tissue  801  is drawn through the suction inlets  712  by suction such that the body tissue  801  adheres strongly to the OCT probe  600 , an enclosed space formed between the balloons  700  and  701  and the body cavity inner wall  800  is brought under negative pressure. In this state, the balloons  700  and  701  are deformed toward the enclosed space, and the internal pressures of the balloons  700  and  701  decrease. This may reduce the airtightness between the balloons  700  and  701  and the body cavity inner wall  800 . Accordingly, the OCT processor  400  controls the internal pressures of the balloons  700  and  701  to a predetermined pressure by the pressure control section  410  (step S 3 ). 
         [0101]    In this state, the OCT processor  400  simultaneously performs radial scanning by rotating a drive shaft and performs longitudinal scanning at a constant rate. The combination allows spiral scanning. The OCT processor  400  starts OCT measurement (step S 4 ). Since the OCT processor  400  acquires three-dimensional tomographic image data of the body cavity in this situation, a blur-free image can be acquired with high resolution. 
         [0102]    The OCT processor  400  determines the presence or absence of instructions to end the OCT measurement (step S 5 ). If instructions to end the OCT measurement are issued, the process shifts to step S 6 . Otherwise, the process returns to step S 4 . 
         [0103]    The OCT processor  400  stops suction in the space formed between the balloons  700  and  701  and the body cavity inner wall  800  through the suction inlets  712  under control of the pressure control section  410  and causes the body tissue  801  to lose its adhesion to the OCT probe  600  in step S 6 . The OCT processor  400  sucks the saline or the X-ray contrast medium from the balloons  700  and  701  under control of the pressure control section  410  to deflate the balloons  700  and  701  in step S 7  and ends the process. 
         [0104]    As described above, in this embodiment, a plurality of balloons (e.g., the two balloons  700  and  701 ) communicating with the balloon inflation port  710  in the longitudinal direction are provided at a distal end portion of the OCT probe  600 , and the suction inlets  712  communicating with the suction port  714  are provided between the balloons  700  and  701 . The OCT processor  400  controls the pressure device (not shown) connected to the balloon inflation port  710  and the vacuum pump (not shown) connected to the suction port  714 . With this control, the distal end portion of the OCT probe  600  can be stably locked to the body cavity inner wall  800 , and the body tissue  801  between the balloons  700  and  701  can be brought into contact with an outer peripheral surface of the sheath  681  of the OCT probe  600 . The OCT processor  400  is thus capable of acquiring a blur-free tomographic image with high resolution. 
         [0105]    Note that although this embodiment has described a case where two balloons are provided at the distal end portion of the OCT probe  600 , the present invention is not limited to this. For example, the configuration may be such that three balloons, the balloons  700  and  701  and a balloon  702  are provided along a longitudinal axis of the sheath  681 , and the suction inlet  712  is provided between the balloons  700  and  701  and between the balloon  701  and  702 , as shown in  FIG. 12 . It should be appreciated that the number of balloons may be three or more. 
         [0106]    The OCT probe  600  according to this embodiment can be applied to a diagnostic imaging apparatus used in combination with an endoscope apparatus. 
         [0107]    More specifically, as shown in  FIG. 13 , a diagnostic imaging apparatus  10  used in combination with the OCT probe  600  according to this embodiment and an endoscope apparatus is mainly composed of an endoscope  100 , an endoscope processor  200 , a light source device  300 , the OCT processor  400  as a living body tomographic image generation device, and the image display section  500  that is a monitor device as a display device. Note that the endoscope processor  200  may be configured to incorporate the light source device  300 . 
         [0108]    The endoscope  100  includes a proximal operation section  112  and an insertion section  114  which is provided to be continuous with the proximal operation section  112 . An operator holds and operates the proximal operation section  112  and performs observation by inserting the insertion section  114  into a body of an examinee. 
         [0109]    A forceps insertion section  138  is provided at the proximal operation section  112  and communicates with a forceps outlet  156  of a distal end portion  144  through a forceps channel (not shown) provided in the insertion section  114 . In the diagnostic imaging apparatus  10 , the OCT probe  600  as a probe is inserted through the forceps insertion section  138  and is led out through the forceps outlet  156 . The OCT probe  600  is composed of an insertion section  602  which is inserted through the forceps insertion section  138  and is lead out through the forceps outlet  156 , an operation section  604  which is intended for an operator to operate the OCT probe  600 , and a cable  606  which is connected to the OCT processor  400  through a connector  401 . 
         [0110]    An observation optical system  150 , an illumination optical system  152 , and a CCD (not shown) are disposed at the distal end portion  144  of the endoscope  100 . 
         [0111]    The observation optical system  150  forms an image of a test object on a light-receiving surface of the CCD (not shown), and the CCD converts the image of the test object into electric signals by means of light-receiving elements. The CCD according to this embodiment is a color CCD in which color filters of the three primary colors (red (R), green (G), and blue (B)) are arranged in a predetermined pattern (a Bayer pattern or a honeycomb pattern) to correspond to pixels of the CCD. 
         [0112]    The light source device  300  causes visible light to enter a light guide (not shown). One end of the light guide is connected to the light source device  300  through an LG connector  120 , and the other end of the light guide faces the illumination optical system  152 . A light beam emitted from the light source device  300  passes through the light guide and is emitted from the illumination optical system  152  to illuminate a visual field range of the observation optical system  150 . 
         [0113]    An image signal outputted from the CCD is inputted to the endoscope processor  200  through an electric connector  110 . The analog image signal is converted into a digital image signal in the endoscope processor  200  and is subjected to processing required for display on a screen of the monitor device  500 . 
         [0114]    As described above, data of an observation image acquired by the endoscope  100  is outputted to the endoscope processor  200 , and the image is displayed on the monitor device  500  connected to the endoscope processor  200 . 
         [0115]    An optical probe, a drive control method for the optical probe, and an endoscope apparatus according to the present invention have been described in detail above. The present invention, however, is not limited to the above-described example. Of course, various improvements and modifications may be made without departing from the scope of the present invention.