GB2239605A

GB2239605A - An arrangement for supporting and positioning a mobile article

Info

Publication number: GB2239605A
Application number: GB9000258A
Authority: GB
Inventors: Koorosh Khodabandehloo; Peter Nigel Brett
Original assignee: University of Bristol
Current assignee: University of Bristol
Priority date: 1990-01-05
Filing date: 1990-01-05
Publication date: 1991-07-10
Anticipated expiration: 2010-01-05
Also published as: GB9000258D0; GB2239605B

Abstract

An article such as a surgical tool (22) is carried by a carriage (10) which is movable along a curved track (4). The track (4) is pivotable in a support frame (2). By moving the carriage (18) along the track (4), and by pivoting the track (4), the tool (22) can be positioned at any desired orientation and at any position within a working envelope. Further flexibility can be achieved by displacing the support frame (2) relatively to a base. The arrangement may be operated by drive motors under the control of a computer. <IMAGE>

Description

AN ARRANGEMENT FOR SUPPORTING A MOBILE ARTICLE This invention relates to an arrangement for supporting a mobile article, and particularly, although not exclusively, to an arrangement for supporting an article such as a surgical tool in the course of operations on, for example, a patient's head.

In surgery, particularly surgery on the brain, the accurate positioning and movement of surgical probes and other tools are vital if a spot to be treated, or from which a sample is to be taken, is to be reached with the minimum interference with other parts of the brain. To assist a surgeon in this, it is known to fasten a ri#gid frame to the patient's skull, and to support an arched bridge on the frame. A carriage is movable along the bridge, and the bridge is graduated so that the position of the carriage can be accurately determined. For performing an operation, an appropriate tool is fitted to the carriage. Operation of the tool, and its adjustment along the bridge, are performed manually by the surgeon. The bridge may be linearly adjustable with respect to the frame, this movement also being controlled manually by the surgeon.

More recently, consideration has been given to the use of robotic control for positioning surgical tools.

Known forms of tool support arrangements for surgical operations are not suited to robotic control and provide inadequate freedom of movement. Also, known robotic manipulators, generally in the form of articulated robot arms, suffer from the major disadvantage that, in the event of a fault, it is possible for the robot arm itself to enter the working envelope, possibly harming the patient. Another disadvantage is that it is very difficult, if not impossible, to move an end effector of an articulated arm along a required path under manual control. This is because coordinated movement of more than one joint is usually required.

According to the present invention there is provided an arrangement for supporting a mobile article, the arrangement comprising a support, a nonlinear track pivotably mounted on the support, and a carriage, for receiving the article, mounted on the track for movement along the track.

The support itself may be mounted on a base so that it can be moved relatively to the base, either linearly or rotationally. Thus, the track may have as many degrees of freedom as necessary, for example up to six. The variety of possible positions for the track gives rise to numerous paths for the carriage, each path being defined by the shape of the track.

The article may be in the form of a tool, such as a surgical tool.

In a preferred embodiment in accordance with the present invention, the arrangement functions as a robotic tool positioner, movement of the track relatively to the support and/or movement of the carriage along the track being performed by drive motors under the control of a computer.

The support may be in the form of a closed frame, the track being pivotable within the frame about an axis which lies generally in the plane of the frame.

The track may be curved through 1800 or more, and be supported by the frame at two oppositely disposed locations.

Where the article is a tool, the support, the track and the carriage Inlay define a three-dimensional effective working volume or envelope which is accessible by the tool, but not by the other components of the arrangement. In other words, once the position of the support is fixed, all possible paths for the track and the carriage lie outside the working envelope. Thus, even if a fault occurs, it is not possible for the carriage or the track to enter the working envelope.

The track may have an operative region, for receiving one or more of the carriages carrying operative tools, and a waiting region, for the storage of carriages carrying operative tools. required at other stages of an operation.

For a better understanding of the present invention, and to show how it may be carried into effect, reference will now be made, by way of example, to the accompanying drawing, which shows a tool positioning arrangement for use in surgical procedures on a patient's head.

The arrangement comprises a support in the form of a closed, substantially D-shaped frame 2. A curved track 4 is pivotably supported within the frame 2 at two oppositely disposed locations 6, 8. Two carriages 10, 12 are provided on the track 4, the carriage 10 being situated on a working region 14 of the track 4, and the carriage 12 being situated on a waiting region 16.

The carriages 10 and 12 are provided with motors 18 for driving them along the track 4 in any appropriate manner. For example, the motors 18 may drive a pinion engaging a rack formed on the track 4.

Also, a motor 20 is provided at the location 8 for pivoting the track 4 about the axis A shown in the Figure. The operation of the motors 18 and 20 is controlled by a computer (not shown) in response to data input by a surgeon.

A tool 22, for example a surgical probe, is fitted to the carriage 10, and an alternative surgical tool 24 is fitted to the carriage 12. The carriages 10 and 12 may be driven along the track 4 independently of each other.

For use, the arrangement shown in Figure 1 is positioned so that the frame 2 surrounds the head 26 of a patient on an operating table 28. To ensure that the patient's head 26 is maintained accurately in position, a stereotactic frame 30 is secured to the patient's skull and is then fixed in position relatively to the support arrangement for the tool 22. By appropriate diagnostic techniques, such as CAT scanning, the surgeon will have identified the area of the patient's brain which is to be reached by the tool 22. The CAT scan will have been performed on the patient with the stereotactic frame 30 fixed to the patient's skull, and consequently the frame 30 can be used as a reference for initial setting up and calibration of the tool support arrangement.When this is completed, the surgeon can input into the controlling computer the coordinates of the point in the patient's brain which he intends to reach, as well as the desired direction of entry of the tool 22 in order to reach that point.

The computer then operates the motor 18 of the carriage 10, and the motor 20, in order to displace the track 4 and the carriage 10 to the required positions. It is also possible for the support frame 2 to be displaced or tilted. For example it may be moved in the direction of the arrows X and Y as shown in the Figure.

When the carriage 10 is in position, the surgeon performs the required operation using the tool 22 either manually or by means of a drive motor for the tool 22.

It will be appreciated that, provided the frame 2 remains stationary, it is not possible for any part of the track 4 or the carriages 10 or 12 to collide with the patient's head 26, even if a serious malfunction occurs. Thus, the working envelope which includes the patient's head 26 is accessible only to the tool 22.

This configuration thus minimises the danger of any harm to the patient should the system malfunction.

It is important, particularly in surgical procedures, to provide a means of manual override so that, should the surgeon so wish, manual operation of the arrangement is possible. Thus, manual controls for pivoting the track 4 relatively to the frame 2, and for displacing the carriages 10, 12 along the track 4, may be provided. With the configuration shown in the Figure, it is possible for the tool to be retracted safely by operating only one joint or linear actuator at a time. Additionally, graduated scales may be provided for indicating the pivoted position of the track 4 relatively to the frame 2, and for indicating the position of the carriages 10, 12 along the track 4.

These graduated scales may also be useful during computerised control of the arrangement, since they would enable the surgeon to check visually that the tool 22 is in the required position before any surgical procedure is initiated.

Although the track 4 is shown as being smoothly curved, tracks of other shape could be used, particularly if the arrangement is to be used for surgical operations on parts of the body other than the head. Also, it will be appreciated that the arrangement shown in the Figure could be adapted for purposes other than surgery, where accurate positioning of a tool or other article, along with several degrees of freedom, are required.

Claims

1. An arrangement for supporting a mobile article, the arrangement comprising a support, a nonlinear track pivotably mounted on the support, and a carriage, for receiving the article, mounted on the track for movement along the track.

2. An arrangement as claimed in claim 1, in which the support is mounted on a base for movement relatively to the base.

3. An arrangement as claimed in claim 2, in which the support is movable linearly with respect to the base, in directions perpendicular to the axis of pivotal movement between the track and the support.

4. An arrangement as claimed in any one of the preceding claims, in which the article is a tool.

5. An arrangement as claimed in claim 4, in which the tool is displaceable relatively to the track in a direction transverse to the track.

6. An arrangement as claimed in claim 4 or 5, in which the support, the track and the carriage define a three-dimensional working volume which is accessible by the tool, but not by the other components of the arrangement, at least while the support is stationary.

7. An arrangement as claimed in any one of the preceding claims, in which the support is in the form of a closed frame, the track being pivotable within the frame about an axis which lies generally in the plane of the frame.

8. An arrangement as claimed in any one of the preceding claims, in which the track is curved through at least 180 and is supported by the support at two oppositely disposed locations.

9. An arrangement as claimed in any one of the preceding claims, in which the track has an operative region, for receiving one or more of the carriages carrying operative tools, and a waiting region, for the storage of carriages carrying operative tools required at other stages of an operation.

10. An arrangement in accordance with any one of the preceding claims, in which displacement of displaceable components of the arrangement is performed by drive motors under the control of a computer.

11. An arrangement for supporting a mobile article, substantially as described herein with reference to, and as shown in, the accompanying drawing.