Patent Description:
Trans-oral laser surgery (or microsurgery) is a commonly used method in which light from a laser is used to perform vaporization, incision, ablation, or photocoagulation on the hypopharynx and larynx tissues, for example the vocal cord tissue. Two convention techniques are known, referred to as `far field' and `near field'.

<FIG> shows a conventional far field trans-oral laser surgery set-up. A suspension laryngoscope <NUM> is used to create a direct and rigid line-of-sight working channel for the laser beam and instruments to access the tissue. A microscope <NUM> provides the surgeon with a magnified visualization of the operative field. A laser unit <NUM> directs a laser beam vertically downward onto a mirror that deflects the laser beam <NUM> to the operative site. The distance between the laser aperture and the target tissue is about <NUM>. A micromanipulator <NUM> adjusts the mirror to steer the laser beam as required by the surgeon, either under manual control or electronic control. However, this technique can only be performed under direct line-of-sight, which causes problems. These include surgeon fatigue after prolonged operations, poor controllability, and the need for extensive training. Most significantly, the need to maintain direct line-of-sight between the microscope and the operative anatomy induces considerable strain on the cervical vertebrae which can suffer lesions; it can cause damage to the dental arch; and can be accompanied by post-operative pain.

<FIG> shows a near field trans-oral surgery in progress. To overcome the straight line-of-sight requirement, a robot-assisted flexible laryngeal scope or flexible robotic surgery system may be used, and the laser light is transmitted via a flexible optical fiber. However, these suffer from problems such as lack of manipulability of the instruments, and the motion performance of the instruments can be of poor accuracy and poor repeatability. A further conventional system uses a micro-fabricated laser deflection mechanism on the distal tip of a semi-flexible endoscope robotic system laryngoscope. Such a laser deflection mechanism is illustrated in <FIG> in which laser light emerges from an optical fiber <NUM> and impinges on a fixed micro-mirror <NUM> which reflects the light to a steerable mirror <NUM>. The light is then deflected by the steerable mirror <NUM> towards the target tissue, such as the vocal folds. However, this is near field, so the working distance of the laser beam (from the last mirror to the target tissue) has been decreased to about <NUM>. This means that changing the position at which the beam hits the target tissue significantly affects the angle of incidence of the beam. The maximum angle of incidence to vocal fold tissue for surgery is about <NUM> degrees from perpendicular. At larger angles there are problems such as: more non-target tissue is removed (tilted cutting), the spot size is enlarged, and the spot shape becomes elliptical. These problems mean that the working area that can be operated on at one time is greatly restricted. In addition, integrating the mechanism into the tip of the scope restricts the available space such that there is not room for other surgical instruments, such as forceps. There are further problems because the micro-mechanism is expensive to fabricate and align; it is difficult to sterilize (or suffers performance degradation due to re-sterilization and reuse), and it has potential electromagnetic compatibility concerns.

<CIT> discloses a coaxial oral intubation device for which a plastic tube can be tightly coupled to a blade via a suture, the suture being passed through the plastic tube, being looped around the distal end of the blade and - in the tightly coupled configuration - being tied to the proximal end of the blade.

The present invention has been devised in view of the above problems.

Accordingly, the present invention provides a trans-oral surgery device comprising:.

Further aspects of the invention are defined in the dependent claims.

In the drawings, like parts are indicated with like reference signs, and duplicated description thereof is avoided.

<FIG> shows a trans-oral surgery device according to an embodiment of the invention comprising a scaffold <NUM> fixed at one end of a curved blade <NUM>. A plurality of cables <NUM> exit the rear of the scaffold <NUM> and follow along the line of the blade <NUM>. The scaffold <NUM> in this embodiment is a generally hollow cylinder, slightly flattened, but could take many different forms, such as a more open structure, provided it can support and accommodate the parts and provide the function discussed below, for example with reference to <FIG> and <FIG>.

The blade <NUM> is seen side-on in <FIG>, and is a thin, substantially rigid or semi-rigid strip, curving through approximately <NUM> degrees (though it does not need to have a smooth continuous curve, but could have a series of discrete angular folds). The blade can be made from any suitable materials, such as biocompatible plastics or steels. In this specific embodiment, the blade is made from a plastics resin. The blade length can be in the range of approximately <NUM> to <NUM>, the width in the range of from approximately <NUM> to <NUM>, and the thickness approximately <NUM> to <NUM> (the thickness and width are not necessarily uniform and can be profiled). The term 'blade' in this context refers to a thin strip, like a blade of grass, and has no connotation of a cutting blade. However, the blade is not limited to a flat strip profile, and could be formed of any suitable rod, lattice, or other structure that resists twisting, fits within the anatomy, and allows clearance for an airway and for the cables <NUM> (and other wires and fiber). The scaffold <NUM> and blade <NUM> can be formed integrally as one piece, for example by 3D-printing, molding, or forming. The axis of the scaffold <NUM> can be inclined at an angle A with respect to the direction of the end of the blade <NUM> as shown in <FIG>. The angle A can be in the range of from <NUM> to <NUM> degrees. This can improve access for example to the larynx of a subject (patient, in this case a human). A range of surgery devices embodying the invention can be fabricated with different angles A, and the appropriate one selected depending on the subject's specific anatomical data. Alternatively, an adjustable, lockable hinge connection between the blade <NUM> and scaffold <NUM> can be provided, so that a desired angle can be selected.

<FIG> shows the scaffold <NUM> in cross-section, and <FIG> is a front end view of the scaffold <NUM>. In this embodiment, the scaffold <NUM> comprises a 'barrel' i.e. a hollow, elliptical or circular cylinder. The length L1 of the barrel of the scaffold <NUM> is in the range of about <NUM> to <NUM> (such as around <NUM>), and the length L2 of the lip is in the range of about <NUM> to <NUM> (typically about <NUM>), such that the total length L is in the range of about <NUM> to <NUM>, such as around <NUM>. As viewed in <FIG>, the diameter of the scaffold is in the range of about <NUM> to <NUM>, with in this example the width being about <NUM> and the height being about <NUM>. Again, the dimensions of the scaffold to be used can be selected based on a subject's specific anatomical data.

At the rear end of the scaffold <NUM>, there are two light sources <NUM>, e.g. LEDs, for illuminating the operative area (multiple sources avoid forming shadows). Also at the rear end are two cameras <NUM> (e.g. CMOS devices; two cameras can be used to provide a stereoscopic view). The light sources <NUM> and cameras <NUM> are provided on a strut extending across the rear end of the scaffold; apart from the strut, the rear end of the scaffold is open. Electrical cables pass along the length of the blade <NUM> to provide external connections to the light sources and cameras. In other embodiments, only one camera need be provided, such as in a low-end version of the device, and two or more cameras in a high-end version of the device. Similarly, the device is not limited to only two light sources widely spaced apart from each other. For example, in another embodiment, a compact ring of light sources can be provided around each camera, and can comprise six of more LED light sources for each camera.

Within the scaffold <NUM> in this embodiment are two supports <NUM> (only one is seen in <FIG> because it is a cross-section showing only the further half). Each support <NUM> comprises a small hollow tube. In this embodiment, the diameter of the tube of the support <NUM> is about <NUM> to <NUM>, and the length is in the range of about <NUM> to <NUM>. Each support <NUM> is anchored in place relative to the scaffold <NUM> by a plurality of tendons <NUM>. The tendons are formed of thin wire. In this embodiment, a set of three tendons <NUM> are attached toward the front end of each support <NUM>, and a set of three tendons <NUM> are attached toward the rear end of the support <NUM>. The tendons <NUM> are slidably attached to the scaffold <NUM>, passing through eyelets (small apertures in the wall of the scaffold) that define entry points into the interior of the scaffold <NUM>. The tendons <NUM> pass along grooves, channels, and/or bores (not shown) in the wall of the scaffold <NUM> to reach the rear of the scaffold where they enter sheaths to form cables <NUM>. The cables <NUM> are in the form of Bowden cables, such that pulling on a tendon <NUM> at the opposite end from the support <NUM>, transmits the pulling force to the support <NUM> even along a curved path of the blade <NUM> that is followed by the cables <NUM>.

<FIG> show one embodiment of a surgery device of the invention in which the rear end of the blade <NUM> (the end furthest from the scaffold <NUM>) is attached to a body <NUM>. The body <NUM> is in the form of a frame, on the outside of which are disposed motor units <NUM>, one for each tendon, and each motor unit having a spool for receiving a tendon, such that operating the motor unit can wind, unwind and tension the respective tendon. On the inside of the frame are force sensors <NUM> for sensing the tension in each tendon, and units for terminating the cables carrying the tendons. In use, the body <NUM> is connected to a support arm (not shown) via an adaptor <NUM>. The support arm holds the surgery device in a fixed position during the surgery, after the scaffold and end of the blade have been inserted within a subject, as shown in <FIG>. The body <NUM> and adaptor <NUM> allow rotation about three axes as shown by the curved arrows (<FIG>), and linear extension and retraction of the blade, to enable fine positioning of the scaffold within the subject.

<FIG> illustrate a different embodiment of the surgery device, having essentially the same components as the embodiment of <FIG>, but with the frame <NUM> being a closed polygon in cross-section, with the motor units <NUM> arranged equally around the periphery. This surgery device is rigid and not articulated (apart from rotation about the arm adaptor <NUM>). Positional adjustment is achieved by repositioning the support arm, and a handle <NUM> is provided.

<FIG> show a further variant of the surgery device of <FIG> with the addition of a screen <NUM>, such as an LCD screen, for viewing images, for example images obtained from one or both of the cameras <NUM>.

<FIG> is an image of an embodiment of a surgery device similar to that of <FIG>. <FIG> also shows a flexible optical fiber <NUM> (which can be within a catheter) which is fixed to one of the supports <NUM> within the scaffold <NUM>. The tip <NUM> of the optical fiber can be seen at the front of the scaffold <NUM> approximately level with the upper lip of the scaffold. The other end of the optical fiber <NUM> can be coupled to a laser source to delivery laser light to the operative area adjacent to the scaffold <NUM>. <FIG> show the surgery device in relation to the head of a model subject <NUM>. The surgery device is suspended by a flexible, articulated support arm <NUM> fixed to a table. In <FIG>, the scaffold <NUM> and front end of the blade <NUM> have been insert through the oral cavity of the subject <NUM>. <FIG> shows a positioning of a surgery device from <FIG> within the human anatomy.

<FIG> shows the connection between the blade <NUM> and the body <NUM> disassembled. The blade <NUM> is fixed to a connection piece <NUM> in which the cables <NUM> terminate, but the tendons <NUM> continue. In use the connection piece <NUM> is attached to the body <NUM>. The tendons <NUM> pass into the body <NUM> and onto the spools of the motor units. However, tendon connectors <NUM> are provided such that the tendons are separable. The tendon connectors <NUM> can be in the form of threaded screw connectors, hooks, clasps, or any other suitable form. By undoing the tendon connectors <NUM>, the blade <NUM> and associated scaffold assembly can be completely detached from the body <NUM>. This facilitates the separate sterilization of the blade and scaffold assembly. The tendons can then be reconnected and the blade and scaffold assembly can then be conveniently reattached to the body <NUM> without having to completely rewind the tendons to all of the motor units. Alternatively, some or all of the blade and scaffold assembly can be single-use items that are replaced by a new one which is then reassembled and connected to the body.

In one embodiment of the invention, the tendons <NUM> comprise ultra-high-molecular-weight polyethylene (UHMW-PE). Such cables are extremely stiff for their cross-sectional area and are not prone to fatigue. The tendons can be approximately <NUM> to <NUM> in diameter, such as <NUM>, and rated for breaking at a load of at least <NUM> N, such as approximately <NUM> N. The Bowden cables can be lined with PTFE tubing to minimize friction between the tendons and the sheath of the cable. The tendons can be accurately fixed to the support by glue. Each motor unit <NUM> can comprise a brushless DC motor and a spool for the tendon with a diameter such as <NUM>. Each force sensor <NUM> can be in the form of a load cell.

The operation of the surgery device will now be explained. The tendons <NUM> are used to position and orient a support <NUM>, as previously mentioned with reference to <FIG>. The combination of the position and orientation is also referred to as the 'pose' of the support <NUM>. Adjusting the position and/or orientation (i.e. pose) is also simply referred to as moving the support relative to the scaffold.

To calibrate the tendons <NUM> for controlling a support <NUM>, one tendon is pulled (by operating its respective motor unit to wind it onto its spool), while the other tendons are essentially slack. When increased resistance to further winding is sensed by the force sensor for that one tendon, it is known that the attachment point of the tendon to the support is pulled fully toward the entry point of the tendon into the scaffold <NUM>. This provides a datum, such that when the motor (which is a servo motor) is unwound, it is known (from the amount of rotation and size of the spool) how much tendon has been released, so that the distance from the entry point to the attachment point of the tendon to the support <NUM> is always precisely known. This process is repeated for each tendon in turn.

By subsequently winding the motor units and suitably tensioning all the tendons, the spatial position and angular orientation of the support <NUM> is uniquely defined in 3D relative to the scaffold. A control unit (not shown, but which may be a computer running software) can compute the position and orientation of the support <NUM>, using triangulation and trigonometry, knowing the lengths of the tendons unwound from the datum calibration positions. The control unit can also drive the motor units to reposition the support to a required position and orientation. An optical fiber is fixed to the support <NUM> (with the position of the tip of the fiber known relative to the support), so knowing the position and orientation of the support also defines the position and orientation of the tip of the fiber.

<FIG> shows a schematic representation of a scaffold <NUM>, with the end of a support <NUM> attached by three tendons <NUM>. In this example, the entry points of two of the tendons <NUM> from the scaffold <NUM> are diametrically opposite each other, at the top and bottom, and the third entry point is at the side. The top row of diagrams of <FIG> illustrates that, by adjusting the lengths of the tendons <NUM>, the end of the support <NUM> can be made to describe a linear path (indicated by the straight arrow). The bottom row of diagrams of <FIG> illustrates that, by suitably adjusting the lengths of the tendons <NUM>, the end of the support <NUM> can be made to describe an arcuate path (indicated by the curved arrow). Other shapes of path are possible, such as circular or other trajectories, or freely defined paths. A number of paths can be pre-programmed into the control unit to perform autonomously, or can be manually controlled (but whereby the shape of path indicated by a surgeon using, for example, a joystick, is automatically converted into appropriate drive signals for the motor units by the control unit). An incision path can be defined by the surgeon and stored in the control unit, and then the device can perform the actual incision along the path autonomously, using laser light, from the stored information. In this way, high accuracy, repeatability, and uniform velocity of motion of the laser beam path can be achieved.

<FIG> only shows one end of the support <NUM>; there are of course tendons at the other end to further control the position and orientation of the support, and hence the direction of a laser beam emitted from an optical fiber fixed to the support.

In use, with the surgery device positioned with the scaffold adjacent to the hypopharynx or larynx, an aiming beam of visible light is emitted from the tip of the optical fiber so that the surgeon can see the point where it impinges on the anatomy. The aim of the light beam can be moved by manual or automated control. When in a desired position, the surgical laser light is passed through the optical fiber and emitted from the tip to impinge on the tissue. The term 'light' used herein is not restricted to visible light, but can include, for example, infra-red and ultra-violet light. The surgical laser light can be pulsed. The aiming beam can be a low power level setting of the surgical light, or the aiming beam can be provided by a completely different source from the surgical laser light (such as the aiming beam being a visible wavelength of light and the surgical laser light being infra-red). The surgical laser light can be provided from a suitable laser source such as a gas laser or a solid state laser, and examples include a CO<NUM> laser, thulium laser, potassium titanyl phosphate (KTP) laser, blue laser, and so forth.

In more detail, in one embodiment of the invention, the size and shape of a laser scan pattern are pre-programmed, and a joystick is used to set the center of the scanning pattern and change its direction. With conventional apparatus, an arbitrary free scan pattern is not allowed, and therefore many small-scaled scan patterns are required to dissect irregular pathological margins. This leads to increased procedural time and some loss of accuracy, thereby compromising the advantages of the free beam delivery technique. An improved approach for describing and executing a free scan path is as follows: the implementation is a master-slave controller in which by using control points, an autonomous path can be determined. The master manipulator (such as a joystick) is used to determine and select desired control points in the workspace, which are then used to generate the final path and perform the path scan automatically. The ideal pose of the fiber tip is normal to the target tissue, which results to a circular spot shape of the aiming beam. The operator can choose the proper pose based on the apparent spot shape. The control points include a starting point, an endpoint, and roughly equidistant 'via' points to sparsely describe the desired trajectory.

The pose of the support is recorded for all control points, and the sequentially saved points serve as the input data to generate the entire scan path (x, y, z, yaw, pitch), for example using the Catmull-Rom spline interpolation. The control unit then executes the continuous generated path. An inverse dynamics PD (proportional-derivative) control algorithm with tension optimization is performed. The control is based on a PD tension control routine. Inverse Kinematics is used to transform the desired position in the support pose space to a desired rotation in the motor joint space. The Jacobian which describes this transformation can be used in combination with the static equilibrium equations of all the tendon force-vectors to numerically calculate the optimal tension distribution. By only allowing solutions which are within bounds - i.e. a positive tension to prevent tendon slackness and within a maximum limit to prevent tendon failure - the support remains controllable within its workspace.

Friction can also be minimized by reducing tendon tensions by the control routine. The above method calculates the desired tendon tension, which is compared to the measured tendon tension. The error between the desired and measured tendon tension is multiplied by a proportional gain to control the rotation of each motor. The parameters of the PD controller and the tension gain are determined heuristically.

As can be seen in <FIG>, in this embodiment, the end of the support can be moved to any position within a triangle in the right-hand side of the scaffold as viewed in the Figure. This is so that another support can be provided in the left-hand side of the scaffold (as shown in <FIG>). However, embodiments of the invention are not limited to this arrangement. For example, more than three tendons can be provided, such as four at the front of the support and four at the rear of the support. The points of entry of the tendons can also be arranged to define different regions for the support or supports.

Claim 1:
A trans-oral surgery device comprising:
a scaffold (<NUM>) insertable into the vicinity of the larynx or hypopharynx of a subject;
a support (<NUM>) arranged for holding a flexible optical fiber (<NUM>) for delivering light to the subject;
a plurality of tendons (<NUM>) connected to the support (<NUM>) and slidably anchoring the support (<NUM>) to the scaffold (<NUM>), whereby the tendons (<NUM>) are adjustable to move the support (<NUM>) relative to the scaffold (<NUM>);
a blade (<NUM>) having a front end and a rear end, wherein the scaffold (<NUM>) is provided at the front end of the blade (<NUM>), and the blade (<NUM>) is non-straight.