GB2559175A

GB2559175A - Instrument guidance

Info

Publication number: GB2559175A
Application number: GB1701462.2A
Authority: GB
Inventors: Rachowiecki Michal
Original assignee: On Target Medical Ltd
Current assignee: On Target Medical Ltd
Priority date: 2017-01-30
Filing date: 2017-01-30
Publication date: 2018-08-01
Also published as: GB201701462D0

Abstract

A guidance unit 10 for use with a medical device 30 having an instrument 70 extending therefrom along an instrument axis for interaction with a body. The guidance unit comprises a sensor unit 20. The sensor unit comprising a sensor attachable to said medical device and operable to sense a target position on said body indicated by a target probe 80; and guidance logic operable to indicate when said instrument axis is orientated to intersect said target position. The sensor may comprise a coupling 60 for removable attachment to the device. The guidance logic is operable to indicate a change in orientation or a rotation of said instrument axis so that it intersects the target position. The target probe may comprise a body 90, locators 100,110 and a pointer 120; the pointer may comprise a laser. A target probe calibrator may also be provided to retain the pointer in a fixed location. The guidance unit may comprise a processing logic which may generate an instrument model using detected locations. A method and computer program are also disclosed for the use of the guidance unit.

Description

(54) Title of the Invention: Instrument guidance

Abstract Title: Guidance unit for a medical device (57) A guidance unit 10 for use with a medical device 30 having an instrument 70 extending therefrom along an instrument axis for interaction with a body. The guidance unit comprises a sensor unit 20. The sensor unit comprising a sensor attachable to said medical device and operable to sense a target position on said body indicated by a target probe 80; and guidance logic operable to indicate when said instrument axis is orientated to intersect said target position. The sensor may comprise a coupling 60 for removable attachment to the device. The guidance logic is operable to indicate a change in orientation or a rotation of said instrument axis so that it intersects the target position. The target probe may comprise a body 90, locators 100,110 and a pointer 120; the pointer may comprise a laser. A target probe calibrator may also be provided to retain the pointer in a fixed location. The guidance unit may comprise a processing logic which may generate an instrument model using detected locations. A method and computer program are also disclosed for the use of the guidance unit.

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INSTRUMENT GUIDANCE

FIELD OF THE INVENTION

The present invention relates to a guidance unit, method and computer program product.

BACKGROUND

Surgeons often use powered tools in surgery to drill, cut, saw or perform similar operations on parts of the body. When using these tools, accuracy is very important. Surgeons must be confident that the hole, cut or similar is in the correct place on the body. Due to this, several attempts at drilling or cutting are often performed before the position is correct.

Modern Computer Aided Surgery systems, such as BRAINLAB/STRYKER systems, often use image guided systems with markers attached to the patient's body, that are tracked using principles of computer vision. Computer vision principles are well described in 'Multiple View Geometry in Computer Vision” (Hartley, Zisserman 2003). Methods of computer aided surgical navigation are described in DE 196 39 615 Ai where patient image data, taken from MRI, CT, X-ray etc. is used together with tracked instruments. These systems are large, require many individual pieces of equipment and not suitable for simple procedures. A mobile tracking system is described in US 2009 0068620 At, where a mobile system can be used to track surgical instruments. The use of tracked surgical tools is described in US 2010 179418 Ai.

Current methods for small bone (typically hand or arm) surgery typically do not use any computer assisted systems. Surgeons often make multiple attempts to drill in the correct orientation and position within the bone. After each attempt the position of the hole is checked using x-ray, and if not optimal the hole is redrilled.

It is desired to provide improve techniques for medical device guidance.

SUMMARY

According to a first aspect, there is provided a guidance unit for a medical device having an instrument extending therefrom along an instrument axis for interaction with a body, the guidance unit comprising: a sensor unit having a sensor attachable to the medical device, the sensor being operable to sense a target position on the body indicated by a target probe; and guidance logic operable to indicate when the instrument axis of the instrument is orientated to intersect the target position.

Accordingly, a guidance unit or device is provided. The guidance unit maybe for guiding a medical device. The medical device may have an instrument which extends from the medical device. The instrument may extend from the medical device in the direction of an instrument axis. The guidance unit may have a sensor unit. The sensor unit may have a sensor. The sensor may be attachable or coupleable to the medical device. The sensor may sense or image a target position or target point on a body which is indicated by a target probe. The sensor unit may also have guidance logic.

The guidance logic may indicate when the axis of the instrument is orientated or aligned to intersect with the target position. In this way, a simplified arrangement is provided which enables accurate guidance of the instrument. In contrast to existing systems which utilise inward-looking sensors which need to identify the locations of the target position on the body and together with the location and orientation of the instrument, the first aspect is outward-looking, sensing just the target position indicated by the target probe from the medical device itself, which simplifies the sensing and processing required. Also, the closer proximity of the target probe to the sensor increases accuracy. As such, the first aspect provides a system, where the sensor is on the medical device looking outwards towards the target probe.

In one embodiment, the sensor comprises a sensor coupling for removable attachment to the medical device. Accordingly, the sensor may be coupled and de-coupled from the medical device, enabling it to be used with different devices.

In one embodiment, the guidance logic is operable to indicate when the instrument axis fails to intersect the target position. Accordingly, an indication may be provided of when the instrument axis and the target position are divergent so that the instrument axis is unaligned with the target position.

In one embodiment, the guidance logic is operable to indicate a change in orientation of the instrument axis required to intersect the target position. Accordingly, an indication maybe provided which identifies a reorientation or change in direction of the instrument required in order that the instrument axis will then align with the target position.

In one embodiment, the guidance logic is operable to indicate a rotation of the instrument axis required to intersect the target position.

In one embodiment, the guidance unit comprises the target probe.

In one embodiment, the target probe comprises a target probe body having target probe locators sensable by the sensor unit and a target probe pointer locatable to indicate the target position. Accordingly, the target probe may have target probe locators. Those locators may be arranged so that they may be sensed by the sensor unit. The target probe may also have a target probe pointer which can be located to indicate the target position on the body.

In one embodiment, the target probe comprises a laser which provides the target probe pointer locatable to indicate the target position. Accordingly, the target probe may have a laser. The beam from the laser may be located on the body to indicate the target position.

In one embodiment, the target probe is configured with respective fixed distances between each of the target probe locators and the target probe pointer. Accordingly, the target probe locators maybe each located at a respective predetermined or selected distance from the target probe pointer in order that the location of the target probe pointer can be derived from the locations of the target probe locators.

In one embodiment, the target probe comprises a distance unit operable to indicate a distance between the target probe locators and the target probe pointer. Accordingly, the target probe may provide an indication to the sensor unit of the distances between the target probe locators and the target probe pointer.

In one embodiment, the sensor is operable to detect a location of the target probe locators from which the target position is derived. Accordingly, the sensor may be able to detect or image the location or position of the target probe locators. The location of those target probe locators may provide an indication of the pose of the target probe from which the target position can be derived.

In one embodiment, the guidance unit comprises processing logic having a target probe model operable to derive the target position from the location of the target probe locators. Accordingly, a model may be provided which receives the sensor information and determines the target position.

In one embodiment, the guidance unit comprises a target probe calibrator operable to retain the target probe pointer at a fixed location with respect to the sensor. Accordingly, a calibrator maybe provided which locates or holds the target probe pointer at a fixed or unvarying location or position with respect to the sensor.

In one embodiment, the target probe calibrator comprises a complimentary-shaped body to engage with the target probe pointer. Accordingly, the calibrator may be shaped to engage with or hold the target probe pointer in the fixed location.

In one embodiment, the complimentary-shaped body is configured to rotate about a fixed point within the target probe calibrator. Allowing rotation can make it easier to retain the target probe pointer in the fixed location.

In one embodiment, the processing logic is operable to generate the target probe model using detected locations of the locators when the target probe is manipulated into different orientations while retained by the target probe calibrator. Accordingly, the processing logic may generate or optimize the target probe model based on the detected or sensed locations of the locators as the target probe is moved into different orientations while the target probe pointer is retained at the fixed location by the target probe calibrator.

In one embodiment, the processing logic is operable to determine a location of the instrument axis. Accordingly, the processing logic may identify a pose, position and/or orientation of the instrument axis. Typically, this maybe determined relative to the location of the sensor.

In one embodiment, the processing logic has an instrument model from which the location of the instrument axis is derived. Accordingly, an instrument model may be provided which may derive the position and orientation of the instrument axis.

In one embodiment, the guidance unit comprises an instrument location calibrator having an instrument calibrator body with instrument calibrator locators sensable by the sensor and an instrument calibrator positioner operable to locate the instrument calibrator body at positions along the instrument axis. Accordingly, an instrument location calibrator may be provided. The instrument location calibrator may have locators which can be sensed by the sensor. The instrument location calibrator may also have an instrument calibrator positioner which locates the instrument calibrator body at different positions along the instrument axis. Hence, the instrument location calibrator maybe located along the instrument axis in order to provide an indication of the pose, position and/or orientation of that axis.

In one embodiment, the instrument calibrator positioner locates the instrument calibrator body at different positions along the instrument axis.

In one embodiment, the instrument calibrator positioner engages the instrument calibrator body with the instrument. Accordingly, the instrument calibrator positioner may engage with or be received by the instrument itself.

In one embodiment, the instrument calibrator positioner engages the instrument calibrator body with the medical device in place of the instrument. Accordingly, the instrument calibrator positioner may be used to locate the instrument location calibrator on the instrument axis in lieu of the instrument.

In one embodiment, the instrument location calibrator is removably attachable to the sensor. Accordingly, the instrument location calibrator may also be supported by the sensor to provide additional mechanical support.

In one embodiment, the processing logic is operable to generate the instrument model using detected locations of the instrument calibrator locators when the instrument calibrator body is manipulated into positions along the instrument axis. Accordingly, the processing logic may generate or optimize the instrument model using sensed locations of the instrument calibrator locators, as the instrument calibrator body is moved to different positions along the instrument axis.

In one embodiment, the sensor coupling removably attaches the sensor to the medical device in one of a plurality of different sensor positions. Accordingly, the sensor may be located on the medical device at a number of different positions, locations and/or orientations. This enables the sensor to be repositioned, if required, to facilitate sensing of the target probe when the medical device is orientated into different positions during use.

In one embodiment, the processing logic is operable to generate the instrument model using detected locations of the instrument calibrator locators when the instrument calibrator body is manipulated into positions along the instrument axis in each sensor position. Accordingly, the instrument model maybe generated or optimized to identify the pose, position and/or orientation of the instrument axis for each different sensor position.

In one embodiment, the sensor is operable to indicate the sensor position and the processing logic is operable to determine an orientation of the instrument axis for that position. Accordingly, the current sensor position may be indicated from which the relative pose, position and/or orientation of the instrument axis for that position may be derived.

In one embodiment, at least one of the processing logic and the guidance logic is one of integral with and remote from the sensor. Accordingly, the processing logic and/or the guidance logic may be either collocated with the sensor or elsewhere. Typically, when remote from the sensor a wireless or wired communication link is used to provide communication therebetween.

In one embodiment, the sensor is operable to sense locations of the target probe locators from which the processing logic determines the target position with respect to the instrument axis.

In one embodiment, the processing logic determines a correction required to the instrument axis to intersect the target position.

In one embodiment, the guidance unit comprises the medical device and instrument.

In one embodiment, the instrument comprises one of a drill, saw, chisel, fraise, implant, needle, trocar and drainage device.

According to a second aspect, there is provided a method of guiding a medical device having an instrument extending therefrom along an instrument axis for interaction with a body, the method comprising: attaching a sensor to the medical device sensing a target position on the body indicated by a target probe using the sensor; and indicating when the instrument axis of the instrument is orientated to intersect the target position.

In one embodiment, the sensor comprises a sensor coupling for removable attachment to the medical device.

In one embodiment, the method comprises indicating when the instrument axis is orientated to intersect the target position.

In one embodiment, the method comprises indicating when the instrument axis fails to intersect the target position.

In one embodiment, the method comprises indicating a change in orientation of the instrument axis required to intersect the target position.

In one embodiment, the method comprises indicating a rotation of the instrument axis required to intersect the target position.

In one embodiment, the target probe comprises a target probe body having target probe locators sensable by the sensor unit and a target probe pointer locatable to indicate the target position.

In one embodiment, the method comprises indicating the target position with a laser of the target probe.

In one embodiment, the target probe is configured with respective fixed distances between each of the target probe locators and the target probe pointer.

In one embodiment, the method comprises indicating a distance between the target probe locators and the target probe pointer.

In one embodiment, the method comprises detecting a location of the target probe locators from which the target position is derived.

In one embodiment, the method comprises deriving the target position from the location of the target probe locators using a target probe model.

In one embodiment, the method comprises retaining the target probe pointer at a fixed location with respect to the sensor with a target probe calibrator.

In one embodiment, the method comprises engaging the target probe pointer with a complimentary-shaped body of the target probe calibrator.

In one embodiment, the method comprises rotating the complimentary-shaped body about a fixed point within the target probe calibrator.

In one embodiment, the method comprises generating the target probe model using detected locations of the locators when the target point is manipulated into different orientations while being retained by the target probe calibrator.

In one embodiment, the method comprises determining a location of the instrument axis.

In one embodiment, the method comprises deriving the location of the instrument axis from an instrument model.

In one embodiment, the method comprises locating an instrument location calibrator having an instrument calibrator body with instrument calibrator locators sensable by the sensor at positions along the instrument axis.

In one embodiment, the method comprises locating the instrument calibrator body at different positions along the instrument axis.

In one embodiment, the method comprises engaging the instrument calibrator body with the instrument.

In one embodiment, the method comprises engaging the instrument calibrator body with the medical device in place of the instrument.

In one embodiment, the method comprises removably attaching an instrument location calibrator to the sensor.

In one embodiment, the method comprises generating the instrument model using detected locations of the instrument calibrator locators when the instrument calibrator body is manipulated into positions along the instrument axis.

In one embodiment, the method comprises removably attaching the sensor to the medical device in one of a plurality of different sensor positions.

In one embodiment, the method comprises generating the instrument model using detected locations of the instrument calibrator locators when the instrument calibrator body is manipulated into positions along the instrument axis in each sensor position.

In one embodiment, the method comprises indicating the sensor position and determining an orientation of the instrument axis for that position.

In one embodiment, the method comprises sensing locations of the target probe locators from which the processing logic determines the target position with respect to the instrument axis.

In one embodiment, the method comprises determining a correction required to the instrument axis to intersect the target position.

In one embodiment, the instrument comprises one of a drill, saw, chisel, fraise, implant, needle, trocar and drainage.

According to a third aspect, there is provided a computer program product operable, when executed on a computer, to perform steps of the second aspect.

Further particular and preferred aspects are set out in the accompanying independent and dependent claims. Features of the dependent claims may be combined with features of the independent claims as appropriate, and in combinations other than those explicitly set out in the claims.

Where an apparatus feature is described as being operable to provide a function, it will be appreciated that this includes an apparatus feature which provides that function or which is adapted or configured to provide that function.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of the present invention will now be described further, with reference to the accompanying drawings, in which:

Figure l illustrates a guidance unit according to one embodiment;

Figures 2A, 2B and 3 illustrate target probes according to embodiments;

Figures 4A to 4D illustrates techniques for target probe calibration according to embodiments;

Figure 5 illustrates an arrangement for calibrating a target probe according to one embodiment;

Figures 6A to 6C illustrate techniques for calibrating the instrument access according to embodiments;

Figure 7A and 7B illustrates couplings of embodiments for connecting the sensor unit to medical devices; and

Figure 8 describes the main steps when operating the guidance unit according to one embodiment.

DESCRIPTION OF THE EMBODIMENTS

Overview

Before describing embodiments in any more detail, first an overview will be provided. Embodiments provide a compact arrangement which guides an instrument to a target position. Unlike existing techniques which can be described as “outside-in” approaches that have remotely-located cameras which seek to image a target probe as well as an instrument, embodiments provide an “inside-out” arrangement where the sensor is colocated with the instrument. This simplifies the amount of processing required, since the pose of the instrument (the position and orientation of the instrument with respect to the sensor) is fixed for any fixed sensor position, and the only variable then becomes the relative location of a target point, typically indicated by a target probe. The location of the target position can be derived by sensing a target probe using the sensor, and its relative location to the sensor (and therefore its relative location with respect to the instrument axis) can readily be derived. An indication can then be provided of whether or not the instrument axis is aligned with the target position, together with an indication of any reorientation of the instrument required so that the instrument will intersect the target position. Having the sensor co-located with the instrument significantly improves accuracy, since only one relative position (that of the target probe) needs to be sensed, rather than two relative positions performed by existing techniques. Also, the distance between the sensor and the target probe is reduced. Furthermore, embodiments provide for a more flexible arrangement, since the close location of the sensor to the target probe reduces the likelihood of obstructions occurring which can be common in existing techniques where the cameras are located remotely.

Guidance Unit

Figure l illustrates a guidance unit, generally io, according to one embodiment. The guidance unit io comprises a sensor unit 20 which is releasably attachable to a medical device 30. In this embodiment, the sensor unit 20 has a number of cameras 40, typically two, which sense by visual imaging. The sensor unit 20 also has a processor 50. The sensor unit 20 can be attached and released from the medical device 30 by way of a coupling 60. The medical device 30 has an instrument 70 extending from the body of the medical device 30. The instrument 70 extends from the medical device 30 in a direction or along an instrument axis A. A target probe 80 is also provided. The target probe 80 has a target body portion 90, target probe locators too, 110 and a target probe pointer 120 which marks a target position P.

In operation, the cameras 40 image the target probe locators too, 110 and provide image data to the processor 50. In embodiments, the processor 50 then performs image processing on the image data to identify the locators too, 110 and, using conventional computer vision techniques using pre-stored information regarding the configuration of the target probe 80 such as, for example, a target probe model, identifies the orientation or pose of the target probe 80 and a target position P in space (in 3 dimensions) of the target probe pointer 120. The processor 50 also utilises prestored information about the location of the instrument axis A and determines a vector offset a required to orientate the instrument axis A so that it intersects the target position P of the pointer 120.

Accordingly, a user can place the target probe pointer 120 at a location on a body 130 which defines the target position P for the instrument. The device 30 is manipulated so that the instrument 70 contacts with the body 130 at an entry location E. The cameras 40 image the target probe locators too, 110 and an indication is provided to the user of an orientation required to make the instrument axis A intersect the target position P. That indication is typically an indication of what reorientation to the medical device 30 is required, together with an indication of when the instrument 70 is correctly orientated. For example, a display may be provided on the body of the sensor 20 which indicates which direction to move the medical device 30. Such indications may be provided Usually, audibly or through haptic feedback. Although in this embodiment the processing and feedback is provided by the sensor unit 20, it will be appreciated that either or both of these may be provided by a remote unit, such as a tablet, computer or the like.

Once the medical device 30 and the instrument 70 are correctly orientated, the user can then activate the instrument 70 so that it interacts with the body 130 and the cameras 40 continue to image the target probe 80 and provide feedback on whether the instrument axis A remains aligned with the target position P. The instrument 70 will then eventually exit the body 130 at the point P. Hence, it can be seen that the guidance unit 10 provides an arrangement for guiding the instrument 70 from a selected entry location E to a selected target position P. It will be appreciated that the user may cease operating the instrument 70 short of the target position P, if required.

Target Probes

Figures 2A and 2B illustrate alternative target probes 80A, 80B according to embodiments. As can be seen in Figure 2A, a target probe 80A is provided. The target probe 80A has a target body portion 90A and target portion locators 110A. In this embodiment, a pair of lasers 125A is provided which are orientated so that the laser beams 127A converge at a fixed distance D_A from the target body portion 90A. Accordingly, the target probe 80A is located so that the laser beams 127A converge at a target position P_A on the body 130A and the target position P_A can be derived by imaging the target probe locators 110A using the cameras 40 of the sensor unit 20.

Figure 2B illustrates a similar arrangement of a target probe 80B. The target body portion 90B has target probe locators 110B and a laser 125B. The laser 125B has rangefinder functionality which measures the distance D_B from the target body portion 90B to the target position P_B on the body 130B. An indication of the distance D_B is transmitted (in this embodiment wirelessly) by a transmitter 95B, typically to the sensor unit 20 or a remote processing device such as a tablet. Accordingly, the target probe 80B is located so that a laser beams 127B illuminates a target position P_B on the body 130B and the target position P_B can be derived by imaging the target probe locators 110B using the cameras 40 of the sensor unit 20.

Figure 3 illustrates the configuration of target probes according to different embodiments. As can be seen, the target probes have various straight or bent target probe pointers as well as different configuration target probe locators which are used to determine the location and orientation of the target probe.

Target Probe Calibration

Figure 4A illustrates a technique for target probe calibration. A retainer 140 is provided in a fixed location with respect to the cameras 40. The retainer 140 has a recess 150 which receives the target probe pointer 120. The sensor unit 20 is positioned in a fixed location where it is able to image the target probe 80 using the cameras 40. For example, the sensor unit 20 maybe placed on a table, either attached or unattached to the medical device 30. Alternatively, the retainer 140 may form part of a jig and the sensor unit 20 is attached to a coupling on that jig. In either event, the sensor unit 20 and the retainer 140 remain static while the target probe pointer 120 is located into the recess 150. The target probe body 90 is then displaced while the target probe pointer 120 remains retained by the recess 150. The image data collected by the cameras 40 and passed to the processor 50 provide a so-called “point cloud” for the different locations of the locators too, 110 imaged by the cameras 40 as the target probe body 90 is manipulated. Using known mathematical techniques, such as those described in “Point-cloud-to-point-cloud technique on tool calibration for dental implant surgical path tracking”, Lorsakul, Auranuch et al, Medical Imaging 2008: Visualization, Image-Guided Procedures, and Modeling, Proceedings of the SPIE, Volume 6918, article id. 691829,12 pp. (2008), the processor 50 determines the relative locations of the locators too, 110 and the location of the target probe pointer 120. A model representing the target probe 80 is then generated and stored by the processor 50. Accordingly, subsequent imaging of the target probe 80 by the cameras 40 can be provided to the model stored by the processor 50, from which the orientation or pose, together with the target position P of the target probe pointer 120 is then derived.

Figure 4B illustrates target probe calibration for a target probe 80C. The target probe 80C has a target probe body portion 90C and target probe locators 100C. The target probe pointer 120C has a conduit 95C which is coaxially-located along an elongate axis B of the target probe 80C. A laser is located such that the laser beam 127C travels along the conduit 95C. The laser has a range-finder function which measures the distance to the object that is illuminated. As can be seen, the target probe 80C is calibrated using the technique mentioned in relation to Figure 4A above.

Figure 4C illustrates a retainer 140A for target probe calibration according to one embodiment. In this embodiment, rather than providing a recess 150 within which a target probe pointer is received, instead the retainer 140A is provided with a spherical socket 145A within which an annular ring 147A (which has a spherical outer surface) is rotatably retained. This enables an appropriate target probe pointer to be located and rotated about a fixed point C. This arrangement is particularly useful for calibrating laser-type target probe pointers which tend to have larger target probe pointers which may otherwise slip within the recess 150.

Figure 4D illustrates a retainer 140E for target probe calibration according to one embodiment. In this example, the retainer 140E comprises a generally cylindrical body having a tapered, reduced diameter portion 145E which is received within the chuck of a medical device 30E. In this example, the medical device 30E is a drill. At one end of the retainer 140E there is provided a recess 150E which receives the target probe pointer 120E of a target probe 80E. The target probe 80E has a target probe body 90E which has target probe locators 100E, 110E. The image data collected by the cameras 40 and passed to the processor 50 provide the “point cloud” for the different locations of the locators 100E, 110E imaged by the cameras 40 as the target probe body 90E is manipulated. A model representing the target probe 80 is then generated and stored by the processor 50. Accordingly, subsequent imaging of the target probe 80E by the cameras 40 can be provided to the model stored by the processor 50, from which the orientation or pose, together with the target position P of the target probe pointer 120E is then derived.

Laser Target Probe Calibration

Figure 5 illustrates an arrangement for calibrating a target probe 80D. The target probe 80D has a target body portion 90D and target probe locators 110D. A laser beam 127D is emitted from the target probe pointer 120D. A calibration unit 160D attaches to the target body portion 90D. The calibration unit 160D has a sensor 170D which detects the laser beam 127D. The orientation of the laser within the target body portion 90D may then be adjusted to fall on the sensor 170D. Also, the distance of the sensor 170D from the body 90D is fixed by the dimensions of the calibration unit 160D and this maybe used to calibrate the range-finder function of the target probe 80D.

Instrument Axis Calibration

Figure 6A illustrates a technique for calibrating the instrument access A. In this embodiment, the medical device 30D is a drill. The sensor unit 20 is fixed to the drill using the coupling 60. An instrument calibrator 200A is provided which has an instrument calibrator body 210A which has instrument calibrator locators 220A thereon. The instrument calibrator body 210A is attached to a positioner 230A. The positioner 230A is a cylindrical body having a tubular aperture extending therethrough. The tubular aperture is received around a drill bit 70A which extends from the medical device 30D along the instrument axis A. The instrument calibrator 200A is free to rotate about the drill bit 70A and move along the drill 70A along the instrument axis A.

During calibration, the instrument calibrator locators 220A are imaged by the cameras 40 as the instrument calibrator 200A is positioned at different locations along the instrument axis A and rotated about the drill bit 70A in each location. The image data collected by the cameras 40 and passed to the processor 50 provide a “point cloud” for the different locations of the instrument calibrator locators 220A imaged by the cameras 40 as the instrument calibrator body 210A is manipulated in each location. Using known mathematical techniques, the processor 50 determines the relative locations of the instrument calibrator locators 220A and the location of the axis of rotation in each location. Those locations are then fitted to generate the orientation of the instrument axis A. A model representing the instrument axis A is then generated and stored by the processor 50.

Figure 6B shows a similar arrangement, but in this case the medical device 30D utilises a wire 70B which may have insufficient rigidity to support the instrument calibrator body itself. Accordingly, an instrument calibrator 200B is provided which has an instrument calibrator body 210B having instrument calibrator locators 220B extending therefrom. The instrument calibrator body 210B is connected to a telescopic positioner 230B which engages with and is supported by both the chuck of the medical device 30D and via a support structure 240B to the coupling 60. The positioner 230B has an outer portion 235 and a slideably-received inner portion 237. The inner portion 237 is received around the wire 70B.

During calibration, the instrument calibrator locators 220B are imaged by the cameras 40 as the instrument calibrator body 210B is positioned at different locations along the instrument axis A and rotated about the wire 70B in each location. The image data collected by the cameras 40 and passed to the processor 50 provide a “point cloud” for the different locations of the instrument calibrator locators 220B imaged by the cameras 40 as the instrument calibrator body 210B is manipulated in each location. Using known mathematical techniques, the processor 50 determines the relative locations of the instrument calibrator locators 220B and the location of the axis of rotation in each location. Those locations are then fitted to generate the orientation of the instrument axis A. A model representing the instrument axis A is then generated and stored by the processor 50.

Figure 6C illustrates the instrument axis calibration of a medical device 30E. In this embodiment, the medical device 30E is a saw. Accordingly, a saw blade 70E extends from the medical device 30E along the axis A normally either in a horizontal or vertical orientation with respect to the handle of the saw. An instrument calibrator 200E is provided having an instrument calibrator body 210E with instrument calibrator locators 220E extending therefrom. The instrument calibrator body 210E is connected to a positioner 230E. The positioner 230E comprises a body which has an internal aperture shaped to fit the external surface of the saw blade 70E. The instrument calibrator body 210E is rotatably fixed so that it is rotatable about the axis A.

During calibration, the instrument calibrator locators 220E are imaged by the cameras 40 as the instrument calibrator body 210E is positioned at different locations along the instrument axis A and rotated about the axis A which extends through saw blade 70E in each location. The image data collected by the cameras 40 and passed to the processor 50 provide a “point cloud” for the different locations of the instrument calibrator locators 220E imaged by the cameras 40 as the instrument calibrator body 210E is manipulated in each location. Using known mathematical techniques, the processor 50 determines the relative locations of the instrument calibrator locators 220E and the location of the axis of rotation in each location. Those locations are then fitted to generate the orientation of the instrument axis A. A model representing the instrument axis A is then generated and stored by the processor 50. The orientation of the saw blade 70E can either be provided by the user, can be derived by indicating when the instrument calibrator body 210E is at a predetermined orientation with respect to the saw blade 70E (such as in the plane of the saw blade 70), or can be derived from the rotation of the instrument calibrator body 210E (for example, the instrument calibrator body 210E may be configured to rotate +/- X degrees about the plane of the saw blade 70E and the plane of the saw blade 70E can be determined to be the mid-point between those extremes).

Sensor Connectors

Figure 7A illustrates a coupling 60A for connecting the sensor unit 20 with a medical device 30F. In this embodiment, an arcuate track 65A is fixed to an outer surface of the medical device 30F. A runner 65B is retained within the track 65A, which enables the sensor unit 20 to be moved to different positions relative to the medical device 30F. This enables the sensor unit 20 to be moved during use, in order to help ensure that the cameras 40 can retain the locators within their field of view, irrespective of the orientation of the medical device 30F during use.

Figure 7B illustrates a similar arrangement of coupling 60B. An arcuate body 65B is provided which engages with a structure provided on the underside of the sensor unit 20, which enables the sensor unit 20 to be pivoted to different positions.

Where such structures are used to enable the sensor to be located at different positions, it will be appreciated that the position will need to be determined in order that the location of the instrument axis A for that position can be accurately determined. Typically, position locators are provided which report to the processor 50 the current location of the sensor unit 20 in order that the position of the instrument axis A with respect to that current location of the sensor unit 20 is determined.

Guidance Unit Operation

Figure 8 describes the main steps when operating the guidance unit 10 according to one embodiment.

At step S10, the sensor unit 20 is attached to the medical device 30.

At step S20, the location of the instrument axis A is determined using the techniques mentioned in Figures 6A to 6C above. If the sensor unit 20 is moveable to different positions, such as described in Figures 7A or 7B above, then this calibration is performed for each possible position or for a number of positions from which the location from any position can be interpolated.

At step S30, the appropriate target probe is selected and calibrated in accordance with any of the techniques mentioned in Figures 4A to 4D above.

Once the calibration has been completed then, at step S40, the target probe pointer is placed at the appropriate location on the body, as illustrated in Figures 1, 2A and 2B above to indicate the target position P for the instrument 70.

At step S50, the medical device 130 is orientated so that the working end of the instrument 70 is placed in the desired entry location E. If required, the sensor unit 20 is repositioned or the target probe body 80 reorientated such that the cameras 40 are able to image the target probe locators 100,110.

At step S6o, the processor 50 receives images from the cameras (and distance information if laser range-finding is used) and the guidance logic executes a guidance program which utilises the target probe and instrument axis models.

At step S70, the guidance program determines whether the instrument axis A will intersect the target position P identified by the target probe pointer 120. If the two do not intersect, then at step S80 an indication is provided to the user which identifies the correction to be made in order to align the instrument axis A to intersect the target position P.

At step S90, the user reorientates the instrument 70 and processing returns to step S60 where the image of the target probe locators too, 110 from this revised position is provided to the processing logic. If it is determined at step S70 that the instrument axis A intersects the target position P then an indication is provided to the user at step S100. Accordingly, the user may then start the procedure knowing that the instrument 70 is correctly aligned.

It will be appreciated that a variety of different medical devices and instruments may be utilised in embodiments such as, for example, a drill, saw, chisel, fraise, implant, needle, trocar and drainage device. Also, it will be appreciated that the initial location of the instrument and/or control of the instrument during operation may be performed autonomously under computer control, using feedback provided by the guidance program.

Embodiments recognise that an apparatus that could enable first pass accuracy would greatly help reduce surgical time and increase quality of treatment. Embodiments provide a combination of a probe, vision system and feedback system. Embodiments assist surgeons when performing surgery on small bones, where they are required to drill into or through the bone. The surgeon places the probe on the ideal exit point of the bone, and the embodiments present visual feedback to the surgeon on the relative position of the drill. If the drill is pointing at the probe tip, the surgeon receives a ‘goahead’ signal through the feedback system, such as a target turning green. Embodiments provide an improvement on the prior art, enabling even simpler use of the technology to improve surgical accuracy.

Embodiments provide feedback to the user on the relative position of the probe to the tool. This is a simple and effective means of guidance for one tool towards the point of another instrument, the probe, with reference to existing techniques.

Embodiments comprise a tracker head, tracker head mount, calibration unit and probe. The tracker head is mounted, using the tracker head mount, to a tool, which may be a powered saw, drill, reamer or similar. The tracker head has a built-in camera system and a display or arrangement of LEDs for visual feedback. It contains a processing unit and may contain a battery or other means of power, including a socket for a power cable. The mount is designed such that it can securely attach to the majority of small powered tools. The mount enables the tracker head to pivot about the tool central axis, which allows the user to hold the tool in a rotated position, with the tracker head remaining above the tool. The mount includes an attachment for a calibration tool. The probe is an instrument with a pointed end, with three or more markers on the other end, which can be tracked by the tracker head. The function of the system is to provide feedback to the user on the relative position of the tool to which the system is mounted and the probe. The probe is positioned at a point that is of interest to the user, where the end point of the probe is the target to be aimed at. The system tracks the position and orientation of the probe in real -time, and calculates the required movement to bring the axis/plane/direction of the tool into alignment. It provides this information as visual feedback to the user, where the user can then move the tool as required. Prior to use the system is calibrated. The probe and/or tool may require calibration. The probe may be either pre-calibrated, where the positions of the markers relative to the probe tip are known, or must undergo calibration. Probe calibration would be performed using a 'hotspot' method, where the tip of the probe would remain in a fixed position relative to the tracker head. The probe would be pivoted about the point, such that many data points are gathered and subsequently processed to calibrate the system. The calibration tool attaches to the tracker head mount and is adjustable in order to make contact with the tool central axis or plane of work. The end of the calibration tool, in contact with the tool, typically has a minimum of three markers rigidly fixed to it. These markers are tracked by the tracker head. The calibration tool end axis/plane is adjusted such that it is coaxial or coplanar with the tool. It is then moved along a fixed path, such that the tracker captures data points from the markers. The data points are processed to calibrate the tracker head with respect to the tool. Embodiments provide: a combined tracking and feedback unit that mounts to a surgical power tool; a 2D visual feedback system that solves a 3D problem; a mount that can attach to the majority of generic small surgical power tools; a mount that enables the system to rotate about the axis of the tool; and a calibration tool that attaches to the mount, and a method of calibration using said tool.

In embodiments, the camera system attaches to the drill through a mount, that can fit any type of drill. The vision system is small and lightweight. It also may have an LED array on the back as an additional feedback method for the surgeon. If the surgeon is ‘on target’, the green LEDs light up. The probe has markers that can be tracked by the vision system. The system is calibrated by using a cup-like insert which is attached to the drill. The probe is rotated around while its tip sits in the centre of the cup, calibrating the probe. When in use by the surgeon, an algorithm calculates the relative position of the probe relative to the drill centre axis. Feedback is provided by a display that shows a target that moves in real time as the drill / probe positions change.

Embodiments provide the following features: the vision system attaches to surgical tool (drill) and tracks a single instrument (probe); feedback is provided on the relative position (accuracy) through LEDs/display on the back of the tool mounted system; calibration is performed with the system attached to the drill using an additional tool;

the system can be attached to any drill through a clamp-like mount.

Although illustrative embodiments of the invention have been disclosed in detail herein, with reference to the accompanying drawings, it is understood that the invention is not limited to the precise embodiment and that various changes and modifications can be effected therein by one skilled in the art without departing from the scope of the invention as defined by the appended claims and their equivalents.

Claims

1. A guidance unit for a medical device having an instrument extending therefrom along an instrument axis for interaction with a body, said guidance unit comprising:

a sensor unit having a sensor attachable to said medical device, said sensor being operable to sense a target position on said body indicated by a target probe; and guidance logic operable to indicate when said instrument axis of said instrument is orientated to intersect said target position.

2. The guidance unit of claim l, wherein said sensor comprises a sensor coupling for removable attachment to said medical device.

3. The guidance unit of claim l or 2, wherein said guidance logic is operable to indicate when said instrument axis fails to intersect said target position.

4. The guidance unit of any preceding claim, wherein said guidance logic is operable to indicate a change in orientation of said instrument axis required to intersect said target position.

5. The guidance unit of any preceding claim, wherein said guidance logic is operable to indicate a rotation of said instrument axis required to intersect said target position.

6. The guidance unit of any preceding claim, comprising said target probe.

7. The guidance unit of any preceding claim, wherein said target probe comprises a target probe body having target probe locators sensable by said sensor unit and a target probe pointer locatable to indicate said target position.

8. The guidance unit of any preceding claim, wherein said target probe comprises a laser which provides said target probe pointer locatable to indicate said target position.

9- The guidance unit of any preceding claim, wherein said target probe is configured with respective fixed distances between each of said target probe locators and said target probe pointer.

10. The guidance unit of any preceding claim, wherein said target probe comprises a distance unit operable to indicate a distance between said target probe locators and said target probe pointer.

11. The guidance unit of any preceding claim, wherein said sensor is operable to detect a location of said target probe locators from which said target position is derived.

12. The guidance unit of any preceding claim, comprising processing logic having a target probe model operable to derive said target position from said location of said target probe locators.

13. The guidance unit of any preceding claim, comprising a target probe calibrator operable to retain said target probe pointer at a fixed location with respect to said sensor.

14. The guidance unit of claims 12 or 13, wherein said processing logic is operable to determine a location of said instrument axis.

15. The guidance unit of any one of claims 12 to 14, wherein said processing logic has an instrument model from which said location of said instrument axis is derived.

16. The guidance unit of any preceding claim, comprising an instrument location calibrator having an instrument calibrator body with instrument calibrator locators sensable by said sensor and an instrument calibrator positioner operable to locate said instrument calibrator body at positions along said instrument axis.

17. The guidance unit of claim 16, wherein said instrument calibrator positioner locates said instrument calibrator body at different positions along said instrument axis.

18. The guidance unit of claims 16 or 17, wherein said instrument calibrator positioner engages said instrument calibrator body with said instrument.

19- The guidance unit of any one of claims 16 to 18, wherein said instrument calibrator positioner engages said instrument calibrator body with said medical device in place of said instrument.

20. The guidance unit of any one of claims 16 to 19, wherein said an instrument location calibrator is removably attachable to said sensor.

21. The guidance unit of any one of claims 16 to 20, wherein said processing logic is operable to generate said instrument model using detected locations of said instrument calibrator locators when said instrument calibrator body is manipulated into positions along said instrument axis.

22. The guidance unit of any preceding claim, wherein said sensor coupling removably attaches said sensor to said medical device in one of a plurality of different sensor positions.

23. The guidance unit of any one of claims 15 to 22, wherein said processing logic is operable to generate said instrument model using detected locations of said instrument calibrator locators when said instrument calibrator body is manipulated into positions along said instrument axis in each sensor position.

24. The guidance unit of claim 23, wherein said sensor is operable to indicate said sensor position and said processing logic is operable to determine an orientation of said instrument axis for that position.

25. The guidance unit of any one of claims 12 to 24, wherein at least one of said processing logic and said guidance logic is one of integral with and remote from said sensor.

26. The guidance unit of any preceding claim, wherein said sensor is operable to sense locations of said target probe locators from which said processing logic determines said target position with respect to said instrument axis.

27. The guidance unit of any preceding claim, wherein said processing logic determines a correction required to said instrument axis to intersect said target position.

28. The guidance unit of any preceding claim, comprising said medical device and instrument.

29. The guidance unit of any preceding claim, wherein said instrument comprises one of a drill, saw, chisel, fraise, implant, needle, trocar and drainage device.

30. A method of guiding a medical device having an instrument extending therefrom along an instrument axis for interaction with a body, said method comprising:

attaching a sensor to said medical device sensing a target position on said body indicated by a target probe using said sensor; and indicating when said instrument axis of said instrument is orientated to intersect said target position.

31. The method of claim 30, wherein said sensor comprises a sensor coupling for removable attachment to said medical device.

32. The method of claim 30 or 31, comprising indicating when said instrument axis is orientated to intersect said target position.

33. The method of any one of claims 30 to 32, comprising indicating when said instrument axis fails to intersect said target position.

34. The method of any one of claims 30 to 33, comprising indicating a change in orientation of said instrument axis required to intersect said target position.

35. The method of any one of claims 30 to 34, comprising indicating a rotation of said instrument axis required to intersect said target position.

36. The method of any one of claims 30 to 35, wherein said target probe comprises a target probe body having target probe locators sensable by said sensor unit and a target probe pointer locatable to indicate said target position.

37. The method of any one of claims 30 to 36, comprising indicating said target position with a laser of said target probe.

38. The method of claims 36 or 37, wherein said target probe is configured with respective fixed distances between each of said target probe locators and said target probe pointer.

39. The method of any one of claims 36 to 38, comprising indicating a distance between said target probe locators and said target probe pointer.

40. The method of any one of claims 36 to 39, comprising detecting a location of said target probe locators from which said target position is derived.

41. The method of any one of claims 36 to 40, comprising deriving said target position from said location of said target probe locators using a target probe model.

42. The method of any one of claims 36 to 41, comprising determining a location of said instrument axis.

43. The method of any one of claims 36 to 42, comprising deriving said location of said instrument axis from an instrument model.

44. The method of any one of claims 36 to 43, comprising locating an instrument location calibrator having an instrument calibrator body with instrument calibrator locators sensable by said sensor at positions along said instrument axis.

45. The method of claim 44, comprising locating said instrument calibrator body at different positions along said instrument axis.

46. The method claims 44 or 45, comprising engaging said instrument calibrator body with said instrument.

47. The method of any one of claims 44 to 46, comprising engaging said instrument calibrator body with said medical device in place of said instrument.

48. The method of any one of claims 36 to 47, comprising removably attaching an instrument location calibrator to said sensor.

49. The method of any one of claims 43 to 48 comprising generating said instrument model using detected locations of said instrument calibrator locators when said instrument calibrator body is manipulated into positions along said instrument axis.

50. The method of any one of claims 36 to 49, comprising removably attaching said sensor to said medical device in one of a plurality of different sensor positions.

51. The method of any one of claims 43 to 50, comprising generating said instrument model using detected locations of said instrument calibrator locators when said instrument calibrator body is manipulated into positions along said instrument axis in each sensor position.

52. The method of any one of claims 36 to 51, comprising indicating said sensor position and determining an orientation of said instrument axis for that position.

53. The method of any one of claims 36 to 52, comprising sensing locations of said target probe locators from which said processing logic determines said target position with respect to said instrument axis.

54. The method of any one of claims 36 to 53, comprising determining a correction required to said instrument axis to intersect said target position.

55. The method of any one of claims 36 to 54, wherein said instrument comprises one of a drill, saw, chisel, fraise, implant, needle, trocar and drainage.

56. A computer program product operable, when executed on a computer, to perform steps of any one of claims 30 to 55.

Intellectual

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Office

Application No: GB 1701462.2