Abstract:
An anorectal probe system comprising; an anorectal probe assembly having an insertion end for insertion into a patient&#39;s rectum, said probe assembly including a transducer at or adjacent to the insertion end for collecting ultrasound data; a mounting in rotational engagement with said probe assembly at a point distal from the insertion end; said mounting pivotally coupled to the probe assembly at a point intermediate the insertion end and rotational engagement point; wherein on application of a moment about said pivotal coupling, said mounting and probe assembly are arranged to permit selective pivotal movement of the probe assembly about the coupling.

Description:
FIELD OF INVENTION 
       [0001]    The invention relates to anorectal examination, and methods and apparatus to achieve this. In particular the invention relates to the use of ultrasound methods to acquire a series of two dimensional images and create a 3-dimensional image so as to more readily identify tumors leading to rectal cancer. 
       BACKGROUND OF THE INVENTION 
       [0002]    Cancer management is most effective when the cancer is diagnosed early and hence treated early. This is especially true of rectal cancer as it requires surgery in nearly all cases for a complete cure, although radiation and chemotherapy are sometimes used in addition to surgery. Hence, an Endoscopic Ultrasonography (EUS) method is invaluable as a diagnostic tool in rectal cancer in obtaining valuable information about the tumor. 
         [0003]    Traditionally, the EUS procedure involves inserting an ultrasound probe manually by the surgeon through the patient&#39;s anus in order to scan the rectum. During the procedure, the surgeon adjusts the probe to maintain the transducer at the centroid of a 2D image slice and records down the desired ultrasound image by using a footpad. If the probe is not positioned at the center of the rectum, the ultrasound image produced will appear fuzzy in certain sections of the image. Therefore, it is important for a surgeon to be able to position and maneuver the probe to the center of the rectal canal in order to obtain a clear radial image. 
         [0004]    EUS procedure requires skillful surgeons to place and maneuver the ultrasound probe around the right location to extract the most accurate information for clinical diagnosis. Large amount of information is required to make the right diagnosis rendering a lot of time wasted and causing a lot of discomfort to the patient. 
         [0005]    The basic concept of 3D anorectal ultrasound scan is to acquire a series of 2D image slices with tracking the location of each 2D image slice. To date, linear pull back mover (or internal mover) and Magnetically-Tracked Freedhand (MTF) are two common approaches for conducting 3D ultrasound scan. A linear pull back mover is a computer-controlled, motor-driven probe positioner used to move the probe mounted on it backwards to produce a series of parallel images. Similarly, an internal mover (inside the sheath of the probe) drives the transducer inside the probe directly for a series of parallel image acquisition. The MTF approach still needs the skills and experience from an operator to control the position of the transducer for good image quality as mentioned in preceding paragraphs. The shortcoming of the external or internal pull back movers is that the approach cannot keep the transducer at the center of a rectal canal, thereby causing unsatisfactory image quality. It is possible to use untracked freehand probe, where the probe is moved by the operator. It is currently favored by the surgeon. Unfortunately, this does not provide accurate position information and is therefore without benefit for further 3D reconstruction and display. 
         [0006]    In many case, a sigmoidoscope will be inserted in advance of inserting the ultrasound probe. The main purpose of the sigmoidoscope is to prevent relative motion between the ultrasound probe and rectal wall to reduce possible discomfort or tearing of the tumor. Hence, the sigmoidoscope is useful during an anorectal ultrasound scanning. 
         [0007]    The present of the sigmoidoscope creates a problem in that it needs an additional hand to hold it and the ultrasound probe together, in order to move them in tandem. That means the surgeon will not be able to perform the scanning on his own. The surgeon will need an assistant to hold the sigmoidoscope and the ultrasound probe together so that he can operate the ultrasound machine and adjusts and withdraw the ultrasound probe to acquire desired quality images. 
         [0008]    A further problem arises when the surgeon injects water through a water stand to inflate the balloon inside of patient rectum. This may cause water leakage at a location between the water stand and the balloon. The reason is the seals are often not strong enough to prevent the water leakage. Further, there is a tendency for the balloon to inflate at a location between the water stand the sigmoidoscope when injecting water into balloon to inflate the balloon inside of rectum. The reason is the pressure inside the rectum is too high causing the water flow back so that the balloon inside the rectum will lose the contact with rectum wall. 
       SUMMARY OF INVENTION 
       [0009]    In a first aspect the invention provides an anorectal probe system comprising; an anorectal probe assembly having an insertion end for insertion into a patient&#39;s rectum, said probe assembly including a transducer at or adjacent to the insertion end for collecting ultrasound data; a mounting in rotational engagement with said probe assembly at a point distal from the insertion end; said mounting pivotally coupled to the probe assembly at a point intermediate the insertion end and rotational engagement point; wherein on application of a moment about said pivotal coupling, said mounting and probe assembly are arranged to permit selective pivotal movement of the probe assembly about the coupling. 
         [0010]    In a second aspect the invention provides an anorectal probe assembly comprising an anorectal probe; an inflatable membrane positioned over said probe; a water insertion system for inflating the membrane with water; a sigmoidoscope having a central bore for receiving the probe and inflatable membrane and a adaptor selectively engageable with said sigmoidoscope and said probe so as to fix said sigmoidoscope and probe and seal said membrane. 
         [0011]    In a third aspect the invention provides a method for centralizing an anorectal probe within a patient&#39;s rectum, said probe having an insertion end with an ultrasound transducer at or adjacent to the insertion end for collecting ultrasound data, the method comprising the steps of: positioning the insertion end within the patient&#39;s rectum; acquiring an ultrasound image from said transducer locating a centroid of said transducer from the image; locating a centroid of the rectal void from said image; calculating the difference in position of said centroids and instructing a controller to move said probe such that the centroids coincide. 
         [0012]    In a fourth aspect the invention provides a method of creating a 3D ultrasound image of a patient&#39;s rectum including the steps of: inserting an anorectal probe assembly in a patient&#39;s rectum; controlling movement of said probe assembly using a control system in communication with a drive system; positioning said probe such that a centroid of a transducer within said probe coincides with a centroid of a rectal void; acquiring a two dimensional ultrasound image at a first position within said patient&#39;s rectum; controlling said probe so as to withdraw the transducer to a next position, repeating said positioning, acquiring and withdrawing steps a predetermined number of iterations and combining said 2 dimensional images so as to create a 3 dimensional image is created. 
         [0013]    An automated anorectal ultrasound image acquisition system according to one embodiment of the present invention may include a PC based motion controlled system with a drive system and software control system that facilitates automated capturing of 2D ultrasound image slices for further 3D volume reconstruction and image feature extraction. 
         [0014]    In a further embodiment, the motion of the drive system for positioning the probe (or transducer) may be image guided to accurately obtain each slice of ultrasound scan according to the natural anatomy of the rectum. 
         [0015]    A system according to a further embodiment may capture a series of consecutive 2D ultrasound image scans for the anorectal tract by programmable position control of the ultrasound transducer. 
         [0016]    After the probe is inserted into the patient&#39;s rectum by the surgeon, it will be attached to the probe control platform using the acquired ultrasound image, may obtain the centroid of the rectal tract and the probe position and guide the probe control platform to adjust the transducer to the centroid of the rectum. The system may record the desired quality image and withdraw the probe to the next interval until the examination is complete. From the captured 2-dimension data, a 3-dimension model may be re-constructed. 
         [0017]    A system according to various embodiments may collectively or separately;
       (i) Be able to extract the 2D boundary shape and layer structure in the wall of the rectum automatically;   (ii) Be able to reconstruct the 3D view of the rectum base on the 2D slices whose relative position and orientation are known precisely, hence it may provide an intuitive and detailed anatomical view of the whole rectum or rectal wall;   (iii) Be able to display the 3D image in a “peel off” fashion allowing tumor penetration to be shown with respect to the mucosa;   (iv) Be able to extract the tumor boundary to show the proliferation of the tumor;   (v) Be able to extract external anal sphincter and internal anal sphincter as well as the fistula tract.   (vi) Be able to display the 3D structure of the boundary of rectal wall, the tumor and the anal sphincter in a “peel off” fashion.   (vii) Be able to obtain the centroid of the rectal tract automatically during the withdrawal interval of the procedure allowing consistent contract. Moreover, In a further embodiment, the invention may include software including an image acquisition module.       
 
         [0025]    The image acquisition module may guide the probe control platform and perform the image acquisition process. It may further assist in keeping the probe at the centroid of the rectal balloon area for each acquired image. The difference of these two centroids may be used to guide the x-, y- and z-axis motors&#39; motion in the probe control platform by a designed motion control system. 
     
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         [0026]    It will be convenient to further describe the present invention with respect to the accompanying drawings that illustrate possible arrangements of the invention. Other arrangements of the invention are possible, and consequently the particularity of the accompanying drawings is not to be understood as superseding the generality of the preceding description of the invention. 
           [0027]      FIG. 1  is an isometric view of an anorectal examination device mounted to a movable platform according to one embodiment of the present invention; 
           [0028]      FIG. 2  is an isometric view of the anorectal examination device of  FIG. 1 ; 
           [0029]      FIGS. 3A and 3B  are various views of an anorectal probe assembly according to an embodiment of the present invention; 
           [0030]      FIGS. 4A , B and C are various views of an anorectal examination using a device according to a further embodiment of the present invention; 
           [0031]      FIGS. 5A and 5B  are ultrasound images of a patient rectum indicator rectal void and probe centroids; 
           [0032]      FIG. 6  is a flow chart and screen dump of an anorectal examination; 
           [0033]      FIG. 7  is a schematic view of modules for a method according to one embodiment of the present invention; 
           [0034]      FIG. 8  is a screen dump of an ultrasound image taken by a device according to the present invention; 
           [0035]      FIG. 9  is an elevation view of an anorectal examination assembly according to the prior art; 
           [0036]      FIG. 10  is an exploded view of an anorectal examination assembly according to one embodiment of the present invention; 
           [0037]      FIGS. 11A and 11B  are isometric views of an adaptor according to a further embodiment of the present invention; 
           [0038]      FIGS. 12A and 12B  are isometric views of the adaptor of  FIGS. 11A and 11B  mounted to a water stand, and; 
           [0039]      FIGS. 13A and 13B  are various views of the adaptor of  FIGS. 11A and 11B  mounted to a sigmoidoscope. 
       
    
    
     DESCRIPTION OF PREFERRED EMBODIMENT 
       [0040]      FIGS. 1 and 2  show general arrangements of the present invention according one embodiment. Shown is an anorectal examination device  5  comprising an anorectal examination system  10  mounted to a trolley  15 . The system  10  includes an anorectal probe assembly  23  mounted to a mechanical arrangement, in this case, a mounting designed to apply controlled forces, and consequently movement of the probe assembly  23 . 
         [0041]    The mounting comprises a platform  35 , which forms a datum or fixture relative to which movement of the probe assembly  23  is measured. On the platform is placed a drive system  30  having three motors, on for movement in the X-direction  140 , one for the Y-direction  135  and one for the Z-direction  130 . Whilst a number of different actuators could be used, in this case, these motors use ball screws to effect the three linear movements. Three sets of linear guide systems are placed orthogonally to guide three linear motions along X, Y, Z axes. 
         [0042]    There are two revolute joints,  115  and  120 , which are passive joints and together form a rotational engagement between the mounting and the probe assembly  23 . Said joints permit rotation of the probe assembly  23  in the XY and YZ planes. The probe assembly is further attached to the mounting through a linkage, with the linkage coupling  100  the probe assembly at a point intermediate the extreme ends of the assembly  23 . The linkage is engaged at an opposed end to the platform of the mounting. Accordingly, the probe assembly  23  is attached to the mounting at two points  25 ,  100 , with one engagement subject to the forces and movement of the drive system  30 , and the other  100  fixed to the platform, and so fixed from translational movement relative to the platform. In this arrangement, the probe assembly  23  is capable of movement in 5 degrees of freedom (X, Y, Z, XY &amp; YZ) at one point  25  and capable of 3 degrees of freedom (XY, YZ, XZ), and so all rotational, at the other  100 . A probe datum  110  is placed at the proximal end of the probe to make sure the probe assembly  23  is attached in only one position 
         [0043]    For clarity, the first point will be referred to as the rotational engagement  25  and the second the pivotal coupling  100 . 
         [0044]    When the Z and Y axes  135 ,  130  move, the two passive joints  115  and  120  rotate respectively, using the pivotal coupling  100 . The coupling is then placed close to patient&#39;s anus as fulcrum, to adjust the transducer to the rectal centroid of within the 6 cm interval as shown in  FIGS. 4A , B, and C. 
         [0045]    It follows, from this arrangement, that by operating the motors  140 ,  135  &amp;  130  separately or in combination, the probe assembly  23  is capable of a wide range of movement. 
         [0046]    As shown in  FIGS. 2 ,  3 A and  3 B, the probe assembly  23  comprises an anorectal probe  20 , having a gripping end at which the mounting grips the probe at the rotational engagement  25  and an insertion end  96  which is the leading point for insertion of the probe assembly  23 . Located at or near the insertion end is an ultrasound transducer for acquiring ultrasound images from tissue within a known distance from the transducer. The type and operation of the probe  20  does not, of itself, form a part of the invention, and such probes are well known and widely used in the industry for just such examinations. 
         [0047]    The probe assembly further includes an inflatable membrane, similar to a condom which fits over the insertion end, and extends down the length of the probe  20 . The inflatable membrane  250 , more clearly seen in  FIG. 9 , is inflated with water or other liquid when the probe as been inserted. It serves the purpose of expanding the rectal void so as to more clearly examine the rectum of the patient. 
         [0048]    A sigmoidoscope  95  is also present into which the probe  20 , with the inflatable membrane, slides into position. The assembly in this arrangement is common and forms part of the art. However, as shown in  FIGS. 3A and 3B , further included is a further embodiment of the present invention, being an adaptor  105 . The adaptor serves the purpose of engaging the sigmoidoscope  95  and probe  20  so that they work as a single object. The benefits provided by this arrangement will be discussed in further detail later. 
         [0049]    An objective of the invention is to mimic a skilled surgeon in performing anorectal ultrasound scanning. To achieve this objective, the invention, as shown in  FIG. 1  is sufficiently stable and stiff as well as providing an ergonomically friendly set up to be handled by the surgeon. 
         [0050]    The system  10  may be made mobile by means of a trolley  15 , which includes a cart  70  so that it could be pushed by the handle  80  and stationed at desired position and orientation as shown in  FIGS. 4A ,  4 B and  4 C. For added stability, the four-wheel cart  70  has rubber padded retractable legs  65  that enable the system rest on the flour on the rubber pads, the wheels to be lifted up slightly by pushing down the paddle lock  90  when the system is pushed to desired position and orientation. 
         [0051]    To facilitate the ease of operating the probe assembly  23 , a four degree of freedom passive platform  35  is used to fine tune and lock the drive system  30  at desired position and orientation as shown in  FIG. 1 . A lead screw  50  driven by a bi-direction electrical motor  55  with power off breaker is used to adjust the vertical position of the drive system  30 . The direction of motor is controlled by two foot switches  60 . Just below the platform  35  are two pairs of orthogonally placed linear guide poles and linear bearings which allow the platform to move freely in the X-Y plane. Two lever locking devices  45  are used to freeze and unfreeze the movements. Between the platform and drive system  30  is a turning table which allows the drive system  30  to rotate freely 170 about Z axis. A knob locking device is use to lock and unlock the rotation. 
         [0052]    The X and Y linear movements  140 ,  135  are used to retract the probe back segment by segment tracing an “S” shape  160  according to the natural of human rectum anatomy  165 . This motion is controlled by an embedded CPU  85  and an emergency stop switch  75  will be activated by a surgeon according to his/her judgment. 
         [0053]    While the probe is retracted, the pivot ring will move along the probe. The force acting on the anus is minimized, and so assisting in making the patient feel more comfortable. 
         [0054]    In order to measure the distance between the pivot ring  100  and drive system  30  for control purpose, a vernier  145  is built between two devices and a knob-locking device  150  is used to lock the vernier at desired position. 
         [0055]    According to the preferred embodiment, the methodology of the present invention is represented as follows: 
         [0000]    A. Positioning of anorectal examination system with respect to patient ( FIG. 4A )
       i. The anorectal examination system is reset to home position;   ii. Patient is made to lie on the left-lateral position such that anus area is near to the edge of the operating table;   iii. The anorectal examination system is pushed to where the probe is at the same level with the patient&#39;s anus;   iv. The cart wheels are locked by depressing the foot pedal;   v. The pivot ring is pushed close to the patient&#39;s anus;   vi. The vernier is locked and the reading will be recorded.
 
B. Attaching the probe to the anorectal examination system
   i. The sigmoidoscope is inserted into the rectum through the pivot ring and patient&#39;s anus;   ii. The probe, covered by a condom, is inserted into rectum through the sigmoidoscope;   iii. The sigmoidoscope and the probe are connected together by means of an adaptor as shown in  FIGS. 3A , B;   iv. The height of the platform is adjusted to position the probe nearer to probe holder. Finer adjustments of the platform in X, Y axes and rotation about Z axis are performed by the respective mechanisms  40 ,  45  so as to fit the probe into probe holder;   v. The probe is secured onto the probe holder.
 
C. Acquisition of ultrasound images ( FIGS. 5A ,  5 B,  6 ,  7  and  8 )
   i. The anorectal examination system is activated to begin capturing ultrasound image of rectum  180 ,  185 ;   ii. The anorectal examination system computer finds out the centroid of rectum  195 ,  205  and adjusts the probe to this position  190 ,  195     iii. The anorectal examination system computer captures  210 ,  225  and records down this desired image. The ultrasound transducer is withdrawn to next interval;   iv. Repeating steps 2 to 4 until a 6 cm segment is completed   v. The drive system  30  pulls back the probe to the next 6 cm following “S” shape  160  trajectory as shown in  FIG. 4B     vi. Repeating steps 2 to 6 until the whole rectum is scanned.   vii. Detaching the probe from probe holder       
 
         [0074]    With reference to  FIG. 9 , a conventional ultrasound probe assembly comprises an ultrasound probe  20 , water stand  235  and a sigmoidoscope  95 . The water stands  235  connects to the ultrasound probe  20  mechanically by means of “O-Rings” which seal against water pressure during inflation of the membrane  250 . During the scanning, it is necessary to hold the probe  20 , water stand  235  and sigmoidoscope  95  together. 
         [0075]      FIG. 10  shows an alternative arrangement, according to one embodiment of the present invention. In addition to the components comprising a conventional probe assembly, an adaptor  275  is included to obviate the need for an assistant to provide an extra set of hands to the surgeon conducting the examination. Whereas previous, the assistant is required to hold the assembly together, now the use of the adaptor  275  facilitates the holding together of the assembly. Accordingly, the three parts ultrasound probe  20 , water stand  235  and sigmoidoscope  95  are connected together mechanically. Hence, the three parts will move together when the surgeon withdraws the probe  20  during anorectal ultrasound scanning. 
         [0076]      FIG. 11A  shows the unlocked position of the adaptor  275 . The locking latch  290  is in an unlocked position. The top half  280  and the bottom half  285  can rotate about the hinge  300 . An alternative arrangement may include two halves which may be press fit together. 
         [0077]      11 B shows the locked position of the adaptor  275 . The top half  280  and the bottom half  285  are fully engaged, with the locking mechanism  290  engaged with the corresponding latch  295 . In the closed arrangement, an inner profile  305  is formed, which is shaped to engage with a corresponding external profile  310  of a portion of water stand  235  to fix the adaptor  275  with the water stand  235  as shown in  FIGS. 12A and 12B . The external profile  310  is used to secure the inflatable membrane  250  at the water stand  235 . The locking device  290  is used to fasten the top half  15  and the bottom half  16 . 
         [0078]    Referring to  FIG. 13A , the adaptor  275  includes two slots  320  which facilitate securing and unsecuring to the sigmoidoscope  95  onto the adaptor  275 . For installation, the sigmoidoscope  95  is inserted along arrow A and turn along arrow B as shown in  FIG. 13B . This arrangement may be generally referred to as a bayonet fitting. Alternative arrangements may include a screw threaded engagement, a press fit or interference fit, which relies on frictional engagement. 
         [0079]    The adaptor  275  may be made of durable and light materials with enough stiffness and corrosion resistance which include, but not limited to, surface hardened aluminum alloys or Delrin. 
         [0080]    One such EUS procedure to operate the probe assembly using the adaptor  275  according to an embodiment of the present invention is as follows:
       i. The water stand  235  is fixed on the probe  20  by means of an “O-Ring” arrangement;   ii. The probe  20  is covered with an inflatable membrane  250  that is secured at the water stand  235  with two rubber rings  245 .   iii. About 100 cc of water is next used to fill up the membrane  250  and any air bubbles in the system are aspired through the water inlet  230 .   iv. The adaptor  275  is installed with the water stand  235 .   v. The sigmoidoscope  95  is inserted into patient&#39;s rectum  255  and the probe  20  is introduced through the sigmoidoscope  95 .   vi. The sigmoidoscope  95  is slotted into the adaptor  275 .   vii. More water is introduced into the membrane  250  in order to ensure that there is optimum contact between the rectal walls and the membrane, creating and enlarged rectal cavity  260 ;   viii. The surgeon adjusts the probe  20  by one hand to achieve a desirable quality of image captured while the ultrasound probe  20  is gradually withdrawn.