WO2010136799A2

WO2010136799A2 - Device positioning system

Info

Publication number: WO2010136799A2
Application number: PCT/GB2010/050871
Authority: WO
Inventors: Andrew Thomas; Roch Comeau
Original assignee: The Magstim Company Limited; Rogue Research In.
Priority date: 2009-05-29
Filing date: 2010-05-26
Publication date: 2010-12-02
Also published as: GB0909281D0; WO2010136799A3

Abstract

A positioning system (1) for positioning a scientific or medical device (particularly a TMS coil (2) ) in a predetermined location with respect to a living subject, includes a manipulator arrangement (5) which is movable to position the device and a mounting platform (3) for mounting the device. The mounting platform includes a displacement device (14) for displacing the device with respect to the manipulator arrangement; the displacement device being a variable volume displacement device (such as a bag or pouch for example) supplied with a fluid.

Description

Device Positioning System

The present invention relates to positioning systems for devices, such as automated positioning systems enabling positioning of a respective device with respect to a living subject. The system is particularly, although not exclusively, suited to applications involving Transcranial Magnetic Stimulation (TMS) techniques.

There are numerous situations in which it is important to accurately and/or repeatedly position a device (such as for example a medical or scientific device) with respect to a living subject, for example a medical patient or research subject. In certain instances such systems may be used as a manual aid to position and/or support or hold a medical device in a desired location with respect to a patient. In more complex situations the positioning system may be automated and for example a navigation or guidance system may be used to automatically navigate or guide the device to the desired location.

Medical or scientific devices may be monitoring devices, treatment devices, investigation devices and/or surgical devices and may be invasive or non-invasive.

One example of situations in which it is important to accurately and consistently position a medical device with respect to a living subject is in respect of Transcranial Magnetic Stimulation (TMS) techniques. Such techniques are used in medical and other applications. TMS techniques require an electromagnetic coil to be accurately placed on the scalp of the subject and operated to effect electromagnetic stimulation of a specifically targeted brain structure. There are various image guidance systems that enable the user to track the position of the coil on the scalp to accurately target the structure for stimulation. One such system is a Magnetic Resonance Imaging guidance system. Such a system is disclosed in for example WO2004/006750. Positioning of electromagnetic coils for TMS use by means of robotic positioning systems has been proposed. Examples of systems are disclosed in US6266556 and WO02/089902. With living conscious subjects a problem encountered is the need to maintain accurate positioning with respect to the subject in the event that the subject moves position (even slightly).

Image-guided TMS systems allow stimulation targets to be identified and recorded on Magnetic Resonance images displayed on a computer screen. A navigation system may then be used to guide the positioning of the coil on the head to stimulate that target to an accuracy of about 3mm. Image-guided TMS has enabled the widespread adoption of TMS in the research field, and reinvigorated clinical research in the psychiatric and neurological applications.

Despite the benefits of image-guided TMS₃ there are inherent problems. The stimulator coil is relatively heavy, and it can often be a complex task to position the stimulator coil over the target in the correct orientation despite the computer feedback. In addition, many TMS experimental protocols require that the coil be held at the same location for extended periods (for example approaching one hour). This means that both the coil and subject's head must remain fixed with respect to each other, this requirement often requires that the subject's head be uncomfortably restrained and that the heavy coil is held by the operator or by a mechanical arm.

According to a first aspect, the present invention provides a positioning system for positioning a scientific or medical device in a predetermined location with respect to a living subject, the positioning system including:

a manipulator arrangement which is movable (under system control) to position the device;

a mounting platform for mounting the device with respect to the manipulator arrangement, the mounting platform including a displacement device for displacing the device with respect to the manipulator arrangement, wherein the displacement device comprises a variable volume displacement device supplied with a fluid.

Beneficially the fluid supplied to the variable volume displacement device is supplied pressurised from remote source.

In one embodiment, it is preferred that variable volume displacement device comprises a collapsible and expandable container. In certain embodiments the variable volume device may beneficially comprise an inflatable device such as an inflatable bag, bladder or pouch device, hi another embodiment the device may comprise a concertina or bellows type device.

It is preferred that the system includes a pressure transducer enabling pressure representative of the pressure of the variable volume displacement device to be monitored. Beneficially, the output from the pressure transducer may be used to control operation of the manipulator arrangement.

In one embodiment the output from the pressure transducer may be used to control operation of the variable volume displacement device in order to move the device toward or away from the living subject.

The mounting platform provides a means of mounting the device (for example a TMS coil) to the manipulator arrangement. The mounting platform may take various physical forms and does not necessarily need to include planar surfaces or plates.

In one embodiment the mounting platform is caused to expand and contract upon displacement of the displacement device. For example portions of the mounting platform may move toward or away from one another to vary the separation distance between the device and the manipulator arrangement. Beneficially, in certain embodiments the mounting platform may be provided with resilient biasing means arranged to act to inhibit expansion of the variable volume displacement device. The resilient biasing means may comprise spring means.

Beneficially, a control system is provided for controlling operation of the manipulator device and the variable volume displacement device. Such a control system may comprise a navigation and/or guidance control system for moving the device to a predetermined position by means of the manipulator arrangement and/or the displacement device of the mounting platform.

Beneficially, for certain applications the device comprises a TMS coil device.

According to a further aspect, the present invention provides a positioning system for positioning a scientific or medical device in a predetermined location in contact with a living subject, the positioning system including:

a manipulator arrangement which is movable to position the device in contact with the subject;

a contact force sensing arrangement arranged to provide an indication of the contact force applied by the scientific or medical device to the living subject.

Preferred features described in relation to the first aspect of the invention may also be preferred in respect of the further aspect of the invention. For example, the sensing arrangement may beneficially comprises a fluid pressure sensing arrangement.

Beneficially the fluid pressure sensing arrangement is arranged to sense pressure indicative of the displacement device which comprises a variable volume displacement device supplied with a fluid.

It is preferred that a control system enables repositioning of the medical or scientific device in response to control signals from the contact force sensing arrangement. According to a further aspect, the present invention provides a mounting platform for mounting a medical or scientific device with respect to a manipulator arrangement, the mounting platform including a displacement device for displacing the device with respect to the manipulator arrangement, wherein the displacement device comprises a variable volume displacement device supplied with a fluid.

Preferred features described in relation to earlier aspects of the invention may also be preferred in respect of this further aspect of the invention.

According to a further aspect, the present invention provides a TMS system comprising:

a stimulator coil;

a manipulator arrangement which is movable to position the coil in contact with the head of the subject; and,

i) a contact force sensing arrangement arranged to provide an indication of the contact force applied by the coil to the head of the individual; and a control system enabling repositioning of the coil in response to control signals from the contact force sensing arrangement; and/or

ii) a mounting platform for mounting the coil with respect to the manipulator arrangement, the mounting platform including a displacement device for displacing the coil with respect to the manipulator arrangement, wherein the displacement device comprises a variable volume displacement device supplied with a fluid.

In certain realisations, the invention provides a system whereby an operator can identify the target on a display device (such as a computer screen), and the system can monitor and display the device (for example the TMS stimulator coil) position with respect to the target, and manipulate the coil to the desired position using a manipulator/robotic mechanism. This would allow the operator to simply select the target, and the system computer would position the device (for example the TMS coil) automatically. By monitoring the location of both the device and the target, constant adjustments can be made to the device location to accommodate for subject movement. This would improve comfort for the subject as, for example their heads would not have to be restrained and improve accuracy for the operator.

The invention will now be further described in specific embodiments and with respect to the accompanying drawings, in which:

Figure 1 is a schematic representation of an exemplary positioning system in accordance with the present invention;

Figure 2 is a schematic perspective view of an embodiment of a positioning system in accordance with the invention; and

Figure 3 is a perspective view of a mounting system for use in a positioning system in accordance with the invention.

Referring to the drawings, and initially to figure 1, there is shown a positioning system 1 for positioning an electromagnetic stimulator coil 2 of a TMS system in contact with the head of an individual. The positioning system 1 includes a mounting platform 3 to which the TMS stimulator coil 2 is mounted. The mounting platform 3 is in use secured to a movable arm (such as a robot arm) or manipulator arrangement in order to enable the mounting platform (and hence the coil 2) to be moved about under the control of a navigation and guidance control system 4. The robot arm or manipulator arrangement is shown schematically in figure 1 as item 5. An exemplary manipulator system that can readily be adapted for use is disclosed for example in GB2454721. A system having multiple degrees of freedom is preferred as it enables accurate positioning of the TMS stimulator coil 2 in a variety of attitudes and positions. Figure 2 shows a multiple degree of freedom manipulator arrangement 205 provided with a mounting platform 203. The arrangement of figure 2 will be described in greater detail later in this document.

Returning to figure 1, in the embodiment shown, the mounting platform 3 for the TMS coil 2 comprises a pair of plates 6,7 which are spaced apart. Guide rods 9 are mounted to plate 6 and extend through respective apertures in plate 7. The guide rods 9 are provided with end stops to prevent the plate 7 from becoming disengaged with the guide rods 9. Respective extension springs 10,11 are fixed between plate 6 and a fixing flange 12 mounted to plate 7. The fixing flange 12 enables the mounting platform 3 to be connected to the robot arm or manipulator arrangement 5. The springs 10,11 extend through respective apertures in the plate 7 and act upon displacement of the plates 6,7 to tend to restore the separation between the plates to an equilibrium position. A displacement sensor

13 is mounted to the plate 7 in order to provide displacement positional feedback to the navigation and guidance control system 4.

Between the plates 6,7 of the coil mounting platform 3 is positioned a variable volume displacement device in the form of an inflatable air bladder 14. The variable volume inflatable air bladder 14 is supplied with pressurised air via a pneumatic circuit including pneumatic line 15 extending via a branch 15a and valve 16 to a pump 17. The pump 17 is controlled by the navigation and guidance control system 4. The pneumatic circuit 15 has a branch 15b extending to a pressure transducer 18 located in the navigation and guidance control system 4. A pneumatic switch 19 is controlled by the navigation and guidance control system 4 to control operation of the pneumatic valve 16. The pneumatic valve can also be operated to vent the bladder 14 to atmosphere to deflate the bladder 14.

In use the coil 2 is desired to be applied by the robot arm or manipulator arrangement 5 to contact the individuals head at known, predetermined and constant contact pressure or contact force. It is well known in the art that for optimal performance the operating surface of the coil 2 needs to be maintained in contact with the subjects head exerting a small but definite pressure or force. The use of the variable volume inflatable air bladder

14 enables this to be achieved in a convenient manner and also in a way which avoids electrical circuitry to control pressure application in the vicinity of the coil 2. In use the air bladder is held in an inflated (or partially inflated) condition with a known inflation pressure measured by the pressure transducer 18 and controlled by the navigation and guidance control system 4 operating the pneumatic switch 19 to control the pneumatic valve 16. The degree of inflation of the bladder 14 is therefore controlled by means of the navigation and guidance control system 4 operating the pneumatic switch 19 to control the pneumatic valve 16

When increasingly inflated the variable volume inflatable bladder 14 increases in volume and as the pressure increases the plates 6,7 of the mounting platform move apart from one another acting against the restoring force of the springs 11. As the plates 6, 7 move apart the TMS coil 2 effectively moves away from the connection to the robot arm or manipulator arrangement 5. In this way inflation or deflation of the bladder 14 effectively expands and contracts the mounting platform 3 and can be used to fine tune the position of the coil with respect to the individual's head. For example the robot arm or manipulator arrangement 5 can be used for coarse adjustment to position the TMS coil 2 in the general vicinity of the patients head. Inflation of the variable volume bladder 14 can then be used to urge the TMS coil into engagement with the patients head at the desired application force or pressure.

Further benefits can be realised because by using the pressure transducer 18 to monitor the pressure of the air in the bladder. By doing so, movement of the individual's head toward or away from the TMS coil (either changing the pressure with which the TMS coil is held against the head, or causing contact to be lost between the subject's head and the TMS coil 2) can be detected and compensated for. Compensation in such circumstances can be achieved either by the navigation and guidance control system 4 causing the robot arm or manipulator arrangement 5 to be re-orientated or the separation of the plates 6,7 of the mounting platform to be adjusted by inflation or deflation of the variable volume inflatable air bladder 14 (also under the control of the navigation and guidance control system 4). This provides a novel and original approach to monitor and control the contact of the TMS coil 2 in relation to the subject's head. The system enables pneumatic monitoring and control of the fine positioning of the TMS coil 2. Various corrective scenarios can be pre-programmed such that the navigation and guidance control system 4 can initiate appropriate corrective action in response to different detected changes. For example:

1. The subject moves their head away from the TMS coil. The TMS coil needs to be moved forward to contact the head and the correct contact force re-applied. Initially the bladder can be inflated to achieve this but if a maximum threshold separation of the plates is achieved with out head contact being detected, the robot arm or manipulator arrangement 5 needs to be re-orientated to ensure that the TMS coil contacts the subject's head.

2. The subject moves their head gently towards the coil. The increased pressure is detected by the pressure transducer and the TMS coil is moved back (away from the head) by deflating the variable volume air bladder 14 until the desired contact pressure (as measured by the pressure transducer 18) is achieved.

3. The subject moves their head aggressively to butt the coil 2 (sudden large movement). The TMS coil is moved completely away from the subjects head (by movement of the robot arm or manipulator arrangement 5). The pressure in the bladder 14 is released and the TMS coil is reset in the correct initial position at the correct contact force.

The navigation and guidance control system 4 accordingly operates to re-orientate/reposition either by means of the robot arm or manipulator arrangement 5 or the plates of the support platform 3 (by means of the bladder) or both. The system provides a contact force sensing arrangement arranged to provide an indication of the contact force applied by the coil to the head of the individual.

In this embodiment the mounting platform 3 is provided with the bladder 14 to adjust the separation of the coil 2 and the position of mounting to the robot arm or manipulator arrangement 5. The bladder may have an elastically expandable boundary wall or may in certain embodiments simply be a flexible bag type arrangement having a flexible but not elastically expandable wall. Other variable volume enclosures or devices are envisaged. For example a collapsible bellows arrangement may be used. A gas piston arrangement may also be used, although this may be less preferred.

As mentioned earlier, Figure 2 shows a multiple degree of freedom manipulator arrangement 205 provided with a mounting platform 203 for mounting a TMS coil. In figure 2 the position at which the TMS coil is mounted to the manipulator arrangement is indicated schematically at 202. In such an arrangement the mounting platform 203 is connected by articulated arms 251, 252, 253 to a main support frame 250. Servo motors 259 control articulation of the arms to control the positioning and orientation of the mounting platform 203 in response to control signals from the navigation and guidance control system 4. A similar arrangement is described in GB2454721.

The mounting platform 203 is shown more clearly in figure 3. The upper plate 207 of the mounting platform 203 is provided with sockets 262 enabling articulated connection to the respective arms 251, 252, 253 of the multiple degree of freedom manipulator arrangement 205. The lower plate 206 provides a docking surface to which the TMS coil 202 can be secured. The plates 206 and 207 are connected and can be maintained spaced apart by a collapsible hinge 209, which has first and second hinge elements 209a 209b connected at a median hinge 211. The hinge 211 is a spring hinge which is biased to try and draw the plates 206, 207 toward one another. The variable volume bladder (corresponding to item 3 in figure 1 and not shown in figures 2 and 3) is positioned intermediately between the upper plate 207 and the lower plate 206 of the mounting platform 203.

The system of the invention can be used as part of, or in conjunction with, an image guided system including for example an image display to aid the user. A system whereby the operator can identify the target on a display, and the system can monitor and display the TMS coil stimulator's position with respect to that target, and manipulate the coil to the desired position using a robotic or other automated manipulator arrangement. This would allow the operator to simply pick the target, and the computer (navigation and guidance control system 4) would position the TMS coil stimulator automatically. By monitoring the location of both the TMS stimulator coil and the subject's head, constant adjustments can be made to the coil location to accommodate for subject movement. This would improve comfort for the subject as their heads would not have to be restrained and improve accuracy for the operator.

The invention has been primarily described in the context of an application to a TMS technique. The invention has particular utility in this area, however it will be appreciated that the invention extends to other applications that require accurate positioning of technical devices for medical or scientific purposes. For example, the invention will have applicability to surgical and microsurgical devices; NIRS array positioning; electrode placement for electrophysiology techniques; needle placement for accurate tracer injection into medical subjects.

Claims

Claims:

1. A positioning system for positioning a scientific or medical device in a predetermined location with respect to a living subject, the positioning system including:

a manipulator arrangement which is movable to position the device;

2. A positioning system according to claim 1 , wherein the variable volume displacement device comprises a collapsible and expandable container (which may be flexible).

3. A positioning system according to claim 1 or claim 2, wherein the variable volume displacement device comprises an inflatable device such as an inflatable bag, bladder or pouch device.

4. A positioning system according to any preceding claim, wherein the variable volume displacement device is supplied with pressurised fluid.

5. A positioning system according to any preceding claim, wherein the system includes a pressure transducer enabling pressure representative of the pressure in the variable volume device to be monitored.

i 6. A positioning system according to claim 5, wherein the output from the pressure transducer is used to control operation of the manipulator arrangement.

7. A positioning system according to clam 5 or claim 6, wherein the output from the pressure transducer is used to control operation of the variable volume displacement device.

8. A positioning system according to any preceding claim, wherein the mounting platform is caused to expand and contract upon displacement of the variable volume displacement device.

9. A positioning system according to any preceding claim, wherein the mounting platform is provided with resilient biasing means arranged to act to inhibit expansion of the variable volume displacement device.

10. A positioning system according to according to claim 9, wherein the resilient biasing means comprises a spring means.

11. A positioning system according to according to any preceding claim wherein a pressurised fluid supply line supplies pressurised fluid to the variable volume displacement device from a region remote from the variable volume displacement device.

12. A positioning system according to any preceding claim further including a control system for controlling operation of the manipulator device and the variable volume displacement device.

13. A positioning system according to claim 12, wherein the control system comprises a navigation or guidance control system for moving the device to a predetermined position by means of the manipulator arrangement and/or the variable volume displacement device of the mounting platform.

14. A positioning system according to any preceding claim, wherein the scientific or medical device comprises a TMS coil device.

15. A positioning system for positioning a scientific or medical device in a predetermined location in contact with a living subject, the positioning system including:

16. A positioning system according to claim 15, wherein the contact force sensing arrangement comprises a fluid pressure sensing arrangement.

17. A positioning system according to claim 16, wherein the fluid pressure sensing arrangement is arranged to sense pressure indicative of a variable volume displacement device supplied with a fluid.

18. A positioning system according to any of claims 15 to 17, including a control system enabling repositioning of the medical or scientific device in response to control signals from the contact force sensing arrangement.

19. A mounting platform for mounting a medical or scientific device with respect to a manipulator arrangement, the mounting platform including a displacement device for displacing the device with respect to the manipulator arrangement, wherein the displacement device comprises a variable volume displacement device supplied with a fluid.

20. A TMS system comprising:

a stimulator coil; a manipulator arrangement which is movable to position the coil, the coil being required to be in contact with the head of the subject; and,