GB2568051A

GB2568051A - Magnetic stimulation (MS) apparatus and method

Info

Publication number: GB2568051A
Application number: GB1718094.4A
Authority: GB
Inventors: Biginton Matthew; Krinke Lothar
Original assignee: Magstim Co Ltd
Current assignee: Magstim Co Ltd
Priority date: 2017-11-01
Filing date: 2017-11-01
Publication date: 2019-05-08
Also published as: GB201718094D0

Abstract

An apparatus suitable for transcranial magnetic stimulation (TMS) procedures comprising a magnetic field generator 2 for providing TMS and an augmented reality (AR) system to generate an AR environment providing the operator with target site indicators 5 on the patient 1. The AR environment may feature graphical and textual information and may provide a voice or gesture controlled interface. The AR may provide a representative image of the patient’s brain 3 that may be generated from MRI images and may be mapped to a standard model, tools may be provided for optimal mapping. The AR may visually define portions of the brain, predicted magnetic penetration or focal point location. The target and generator positions may be tracked by an optical or electromagnetic system using visual markers or shape recognition. The target site location may be identified by motor cortex tracking and may be stored or retrieved for future procedures.

Description

The present invention relates to a Magnetic Stimulation (MS) Apparatus and preferably a Transcranial Magnetic Stimulation (TMS) coil arrangement. In particular, but not exclusively, the present invention relates to a transcranial magnetic stimulation apparatus

Magnetic stimulating of neuromuscular tissue is well known and comprises a stimulating coil made up of one or more windings, each having a plurality of turns which may generate a succession of electrical discharge pulses producing magnetic pulses which further induce electrical signals in the tissue. Such a coil arrangement is disclosed in US6179770 where the magnetic stimulator generally comprises a charging circuit, a capacitor, a discharge control and a winding which is of a size and power rating appropriate for the generation of magnetic fields sufficient to cause stimulation of a body portion. The individual winding or plurality of windings may be size adapted to fit partly over the cranium of a human patient in many applications, as well as being used for stimulation of other body parts. The coil arrangement including windings acts as an inductor and when connected to a stimulator which includes the capacitor provides an input voltage to the inductor which creates a circuit that passes an out of phase, sinusoidal voltage and current through the Transcranial Magnetic Stimulation (TMS) winding. An intense sinusoidal magnetic field is formed near the winding and is used to stimulate neurons in patients for medical and research applications. An example of a coil arrangement is presented in Figure 1 which shows a single winding coil arrangement 2 presented without a covering that may suitably be positioned on a patient’s cranium. The winding is made up of a single wound conductive element connected to the capacitor via an elongate neck (not shown in Figure 1) that allows positioning of the coil arrangement appropriate to the patient.

Such TMS coil arrangements are used for medical and research applications. A problem exists particularly in TMS of positioning the coil arrangement appropriately. There are many locations that are used to treat various medical conditions that involved TMS for example over the occipital nerve for the treatment of Migranes and the dorsolateral prefrontal cortex (also known in the field as F3) for the treatment of major depressive disorder. Finding F3 can be achieved by using the B3 method or the 5.5cm method. In

-2this example we will describe the 5.5cm method. The TMS coil is placed over the motor cortex area of the brain associated with the right thumb (C3). A procedure involving power adjustment and fine movements of the coil is followed until a thumb twitch is observed when the coil is pulsed over the patient specific area for the thumb found from the motor mapping. This represents the minimum power setting to stimulate the cortex. This point is then typically manually marked by some means and then the treatment location is determined by moving the coil 5.5cm forward from C3 to F3. Once this location is appropriately identified, an indicator is placed on the patients cranium at F3 and the coil arrangement directed to this location. However this is difficult to achieve as the coil arrangement obscures the view of the operator. TMS operators take a great deal of time and effort to ensure that the TMS coil is correctly placed in the correct location and to do this as in the manual method described above is costly in time and therefore there is a need for a better system. Many tracking solutions exist however the operator is still left in doubt if the coil is correctly positioned due to the fact that the operator cannot see with their own eyes that the coil is on the right spot.

The present invention provides an improved apparatus

Viewed from a first aspect, there is provided a transcranial magnetic stimulation (TMS) apparatus for carrying out a TMS procedure; the apparatus comprising a magnetic field generator configured to be positioned relative to a target position on the TMS patient to generate a magnetic field in the vicinity of the TMS patient for providing transcranial magnetic stimulation, an augmented reality system configured to generate an augmented reality environment around a TMS patient, wherein the TMS apparatus is configured to augment visual data indicative of the target position on the TMS patient into the augmented reality environment.

The magnetic field generator may comprise a coil arranged to generate the magnetic field using electromagnetic induction.

An apparatus in accordance with the first aspect enables visual data to be placed into the augmented reality environment generated by the augmented reality system. The visual

-3data indicates a target position on the TMS patient so that the user of the TMS apparatus can see the target position in the augmented reality environment so that they may position the magnetic field generator accordingly.

The target position may be an optimal position for TMS treatment and may indicate a position on the cranium of the TMS patient, which may otherwise be described as a cranial position.

The apparatus may be configured to augment the data indicative of the target position on the TMS patient into the augmented reality environment in a position coincident with the TMS patient’s cranial position.

The effect of this is that the user of the TMS apparatus will not use up time trying to find the appropriate position on the head of the TMS patient before carrying out the procedure.

The data indicative of the target position may comprise indicia indicating the target position on the TMS patient. The effect of this is that the user does not have to take their eyes away from the augmented reality system in order to discern what they are looking at.

The indicia may comprise a text portion providing a description of the respective position.

The apparatus may be further configured to augment into the augmented reality environment operational data relating to the TMS procedure.

The target position may be overlaid in the augmented reality environment over the magnetic field generator component which removes any visual obstacle provided by the magnetic field generator

The augmented reality system may be configured to receive input from the user requesting data relating to the TMS procedure to be augmented into the augmented reality environment generated by the augmented reality system.

-4The input may comprise a voice command or a gesture.

The augmented reality system may augment into the augmented reality environment a display of either the patients individual (magnetic resonance imaging) MRI image or a standard Brain atlas merged to the patient’s head. If this is a standard brain atlas then the motor cortex (for motor mapping) may be pre-identified on the image. The motor cortex may then be displayed in any or each of the coronal, sagittal or transverse sections on the brain atlas.

The augmented reality system may also provide tools to adjust the brain atlas based on identification of discrepancy between the target visible on the atlas and the actual motor response obtained.

The apparatus may be configured to automatically suggest a location for the magnetic field generator based on the MRI image. The operator may then adjust the suggested coil location based on medical or anatomical judgement. The adjustment may be made using the user input functionality of the augmented reality system.

The augmented reality system may utilise the full rich range of user input features provided by an augmented reality headset such as, for example, the Microsoft Hololens to provide a TMS apparatus which is easy to use and enables the user to use the full range of inputs to perform the TMS procedure.

The apparatus may be further configured to augment an image representative of the TMS patient’s brain into the augmented reality environment. This enables the user of the TMS apparatus to visualise the position on the brain that is most exposed to the magnetic field generated by the magnetic field generator.

The representative image of the TMS patient’s brain may augmented into the augmented reality environment in a position determined using the TMS patient’s facial features.

That is to say, the apparatus enables the position of the image representing the TMS patient’s brain to be placed in a position which is predicted using facial features of the

-5TMS patient which removes the requirement for difficult, long-winded procedures to predict the location of the brain and reduces the impact on the patient.

The representative image of the TMS patient’s brain may visually define distinct portions of the brain.

The representative image of the TMS patient’s brain may comprise indicia describing corresponding portions of the brain.

The apparatus may be further configured to augment a visual representation of the predicted penetration and focal point of the generated magnetic field into the TMS patient’s brain.

The effect of this is that the user of the apparatus is kept informed of the predicted penetration and focal point of the generated magnetic field so that the user of the TMS apparatus can easily identify which areas of the TMS patient’s brain are most exposed to the magnetic field.

The apparatus may be further configured to augment an image representative of the magnetic field generator firing into the augmented reality environment to illustrate the path and pattern taken by the generated magnetic field into the TMS patient’s brain.

The target position may be generated using optical tracking or electromagnetic tracking.

The target position may be identified using motor mapping to identify the motor cortex.

The apparatus may use real world markers on the coil and patient to aid in forming a reference frame for tracking relative movement between the coil and patient.

The magnetic field generator may be adjustable in six degrees of freedom. Specifically, the six degrees of freedom may correspond to three angular dimensions and 3 cartesian dimensions.

-6The target position may remains at least partially visible during adjustment of the magnetic field generator relative to the TMS patient. The effect of this is that the user of the TMS apparatus can still monitor where the target position is whilst moving the magnetic field generator.

The data relating to the TMS procedure carried out using the TMS apparatus may be captured and stored for use in a future procedure.

The data indicative of the target position on the TMS patient may be generated using data stored from a previous procedure. This improves the efficiency and repeatability of the procedure.

The augmented reality system may comprise a display to display the contents of the augmented reality environment to a user of the apparatus.

The apparatus may additionally augment a visual representation of a control panel which may be used to control the TMS procedure from within the augmented reality environment. The control panel may be augmented in a “head-up” fashion so that the user of the system can see it whilst they carry out the procedure.

An embodiment in accordance with the first aspect will now be described by way of example only and with reference to the following drawings in which:

Figure 1 is a schematic representation of a coil arrangement which may be used to carry out a transcranial magnetic stimulation procedure in accordance with the embodiment;

Figure 2a illustrates a real world view of a TMS patient’s head with a transcranial magnetic stimulation coil in front of the position on the TMS patient’s head;

Figure 2b illustrates a view of the TMS patient’s head using an apparatus in accordance with the embodiment;

-7Figure 3a illustrates a real-world view of the TMS patient’s head and a user’s finger;

Figure 3b illustrates a view of the TMS patient’s head and a visual display provided by an apparatus in accordance with the embodiment;

Figure 4 illustrates an image representative of the TMS patient’s brain with an image representing the electric field generated by the TMS apparatus in accordance with the embodiment.

We will now describe an apparatus in accordance with the embodiment with reference to Figures 2a and 2b.

Figure 2a shows a real-world view of a user’s head when carrying out a TMS procedure. The transcranial magnetic stimulation coil 2 obstructs the view of the patient’s head which means it is difficult to accurately position the coil 2 during the TMS procedure.

Although the example describes the use of the apparatus on a TMS patient’s head, this is for illustration only and is entirely within the scope of this description for the TMS procedure to be used on another part of the body.

A TMS apparatus in accordance with the embodiment comprises an augmented reality headset such as a Microsoft Hololens or an Oculus Rift. Such a headset provides a view of the ambient environment around a TMS patient which is augmented with various examples of visual data related to the TMS procedure which is being carried out.

The TMS patient may be seated relative to a TMS coil 2 to await treatment and the user of the TMS apparatus may don the augmented reality headset to generate an augmented reality environment around the TMS patient and the TMS coil 2.

An augmented reality environment is a live direct or indirect view of the physical world which has its elements augmented by computer-generated or real-world input such as, for example, sound, video, graphics, haptics or GPS data. That is to say, an augmented reality

-8environment is a view of the physical world which has other data augmented into the environment to provide an augmented view of the physical world to enhance one’s current perception of reality.

The view of the patient’s head through the augmented reality headset is shown in Figure 2b. As can be seen in Figure 2b, the view that is shown to the user comprises an image representative of the patient’s brain 3 overlaid over the TMS coil 2. The effect of this is that the visual obstruction created by the TMS coil is removed as the image of the brain is provided within the augmented reality environment generated by the augmented reality headset.

The image representative of the patient’s brain can be generated using known procedures and the image data corresponding to the image may be fed into the augmented reality environment using the augmented reality headset. Such known procedures may utilise facial features of the TMS patient.

The augmented reality environment also contains further data which includes the target position 5 on the cranium of the TMS patient. The target position 5 can be identified using indicia such as an easily distinguishable dot which may be coloured appropriately to delineate it from the remainder of the image.

As can also be seen from Figure 2b, the augmented reality environment can also include data related to the position of the centre of the TMS coil 2. This data may be indicated by an easily distinguishable dot 4 which may also be coloured appropriately to de-lineate it from the remainder of the image.

The augmentation of indicia into the augmented environment provides a visual indication indicating the position of the TMS coil where the magnetic field is being generated and also highlighting the target position on the TMS patient’s head which is determined to be the optimal place to position the TMS coil 2 to carry out the TMS procedure.

-9The TMS coil 2 is adjustable having six degrees of freedom to enable it to be oriented correctly on the TMS patient’s cranium in order to effectively treat the TMS patient. The inclusion in the augmented reality environment of visual indicators such as the dots indicating the target position and the centre of the TMS coil 2 means that the user of the TMS apparatus can adjust the position of the TMS coil such that the centre of the TMS coil 2 and the target location 5 are aligned during the TMS procedure. This is ensures correct delivery of the therapeutic effect of the TMS coil.

The position of the TMS coil 2 may be suggested by the apparatus but can be adjusted by the user in accordance with professional judgement.

As the target position remains visible during the orientation of the TMS coil 2 the user does not need to worry about the user moving relative to the TMS coil 2 as the apparatus maintains the indicia indicating the target position whilst the TMS coil is positioned accordingly. That is to say, the indicia indicating the target position is effectively locked onto the user and remains visible even if the user cannot keep their head still or wishes to change position to achieve a comfortable position.

The image representative of the brain may be maintained in the augmented reality environment even when the TMS coil 2 is being adjusted.

The image representative of the brain may also be generated using an image of the TMS patient’s brain taken during an MRI scan. The image taken during the MRI scan may then be mapped to a standard brain atlas which may include coronal, sagittal and transverse sections of the image representative of the brain.

The location of the motor cortex which is identified during the procedure may also be displayed on the image representative of the TMS patient’s brain.

The augmented reality system may also provide tools to adjust the standard brain atlas based on identification of a discrepancy between the target position 5 which visible on the

-10brain atlas and the location of the motor cortex which generated the actual motor response obtained at the start of the TMS procedure.

The MRI generated image in addition to the image representative of the standard brain atlas may also be augmented into the augmented reality environment at locations other than the TMS patient’s head. This enables the user of the apparatus to see an enhanced range of information which is pertinent to the TMS procedure being carried out. These images may be respectively introduced into and removed from the augmented reality environment responsive to user input recognised by the augmented reality headset. These images may also be moved around the augmented reality environment to ensure they are in the most optimal position for the user of the TMS apparatus.

We now illustrate with reference to Figures 3a and 3b how the augmented reality headset can be used to provide the user of the TMS apparatus with a wide range of user input possibilities.

Figure 3a shows the user’s hand 7 and the TMS coil 2 in front of the TMS patient’s head. In order to make any changes to the TMS procedure which is being carried out, the user will need to look away or turn to another display.

Figure 3b shows the user’s hand 7, which of course exists in reality, and the target location 5 on the TMS patient’s head 1 as augmented into the augmented reality environment generated by the augmented reality headset donned by the user of the TMS apparatus. That is to say, the user of the TMS apparatus, when they don the augmented reality headset, can see the visual data which is augmented into the augmented reality environment by the TMS apparatus in addition to their own hand.

Also shown in Figure 3b is a user interface 6 which enables the user to both look at and modify the TMS procedure being carried out. The user interface 6 also enables the user of the TMS apparatus to run the TMS procedure in accordance with the stipulated parameters, save the data relating to the TMS procedure and select from a series of options which can also be used to modify the TMS procedure. The user interface 6 may also be used to

-11restore data from a previous TMS procedure which may be recalled from storage. The interface may also have many other common features associated with TMS such as a patient data managed system to record patient details, an interface to motor evoked potential functionalities or an interface to Electroencephalography functionalities for example

The “head-up” nature of the user interface 6 means that a control panel can be provided for the TMS procedure without the user needing to turn their head away from the procedure whilst using the TMS apparatus.

The augmented reality headset is configured such that it recognises the motion generated by any gesture input from the user’s hand 7 and interprets that motion as a gesture which is used to provide input into the TMS apparatus. This gesture input may be used to place inputs into the user interface 6, meaning that the user can simply use the user interface 6 to place input into the TMS apparatus rather than have to look at another display screen or a keypad which requires the user to move their attention away from the TMS patient.

The augmented reality headset is also configured to receive voice input which may be used to request further data that is relevant to the TMS procedure which is being carried out. One example may involve the user inputting a voice command to request that the regions on the image representing the brain which correspond to the different physiological regions of the brain be displayed in different colours or that they be labelled with the name of those regions.

That is to say, if the user wished for the amygdala to be highlighted in green, they may simply say “Label amygdala in green” and the TMS apparatus would colour the portion of the image corresponding to the amygdala in green and also include a text portion which says “Amygdala”.

The user of the apparatus may also use voice commands to request medical data relating to the patient which may then be augmented into the augmented reality environment.

-12We will now describe with reference to Figure 4 how the TMS apparatus can display details of the field generated by the TMS coil 2 as part of the augmented reality environment.

As shown in Figure 4, the TMS apparatus may illustrate the electric field generated by the TMS coil 2 on the surface of the TMS patient’s brain.

The path may be predicted using finite element modelling of the TMS coil 2 and its interaction with the brain of the TMS patient wherein the size of the TMS coil can be used as a parameter in order to estimate which TMS coil 2 would be most appropriate for the procedure.

The illustration may show the depth of penetration and focal point of the generated electric field and this may be normalised by pulse frequency. It is appreciated that other metrics to illustrate the output of the coil may be illustrated such as magnetic field or current density. Higher granularity finite element modelling may also be used to model the depth of penetration and the focal point of the generated electric field in different parts of the brain. The example shows the penetration achieved by a 40mm TMS coil and a 70mm TMS coil.

The shape and orientation of the magnetic field generator may also be determined by the system using standard image processing techniques applied to a visual image of the TMS coil 2.

In order to determine the position of the TMS coil 2 and to accurately measure the magnetic field generated by the TMS coil 2, information regarding the visual identifying features of the TMS coil 2 may be input into the apparatus. These features may include the size of the TMS coil 2.

The position of visual features of the TMS patient may also be input into the apparatus.

The apparatus may then use standard image processing techniques to process the information regarding the visual identifying features of the TMS coil and the patient to

-13establish a frame of reference for the TMS coil which can then be used to normalise the measurements taken during the TMS procedure.

The reference frame may also be determined using optical markers which are placed on the 5 TMS patient and the TMS coil 2. The markers can be arranged on the TMS coil 2 and the patient in a known geometry. The real-world movement of the optical markers can then be tracked using a tracking camera which is then used to determine the movement of both the TMS patient and the TMS coil 2 to generate a frame of reference for the TMS coil 2 and the patient.

Other forms of real-world marker, such as electromagnetic markers, can also be used to determine the frame of reference for the TMS coil 2 and the patient.

Claims

1. A transcranial magnetic stimulation (TMS) apparatus for carrying out a TMS procedure; the apparatus comprising:

a magnetic field generator configured to be positioned relative to a target position on the TMS patient to generate a magnetic field in the vicinity of the TMS patient for providing transcranial magnetic stimulation;

an augmented reality system configured to generate an augmented reality environment around a TMS patient, wherein the TMS apparatus is configured to augment visual data indicative of the target position on the TMS patient into the augmented reality environment.

2. An apparatus according to Claim 1, wherein the target position is an optimal position for TMS treatment.

3. An apparatus according to Claim 1 or Claim 2 wherein the target position is a position on the cranium of the TMS patient.

4. An apparatus according to any preceding claim wherein the apparatus is configured to augment the data indicative of the target position on the TMS patient into the augmented reality environment in a position coincident with the TMS patient’s cranial position.

5. An apparatus according to Claim 4 wherein the data indicative of the target position comprises indicia indicating the target position on the TMS patient.

6. An apparatus according to Claim 5 wherein the indicia comprises a text portion providing a description of the respective position.

7. An apparatus according to any preceding claim wherein the apparatus is further configured to augment into the augmented reality environment operational data relating to the TMS procedure.

8. An apparatus according to any preceding claim wherein the augmented reality component is configured to receive input requesting visual data relating to the TMS procedure to be augmented into the augmented reality environment generated by the augmented reality system.

9. An apparatus according to Claim 8 wherein the input comprises a voice command.

10. An apparatus according to Claim 8 wherein the input comprises a gesture.

11. An apparatus according to any preceding claim wherein the apparatus is further configured to augment an image representative of the TMS patient’s brain into the augmented reality environment.

12. An apparatus according to Claim 10 wherein the representative image of the TMS patient’s brain is augmented into the augmented reality environment.

13. An apparatus according to Claim 11 wherein the representative image of the TMS patient’s brain is augmented into the augmented reality environment in a position determined using the TMS patient’s facial features.

14. An apparatus according to any of Claims 10 to 13 wherein the representative image of the TMS patient’s brain visually defines distinct portions of the brain.

15. An apparatus according to any of Claims 10 to 13 wherein the representative image of the TMS patient’s brain comprises indicia describing corresponding portions of the brain.

16. An apparatus according to any of Claims 10 to 14 wherein the apparatus is further configured to augment visual representation of the predicted penetration and focal point of the generated magnetic field into the TMS patient’s brain.

17. An apparatus according to any of Claims 10 to 15 wherein the apparatus is further configured to augment an image representative of the magnetic field generator firing into the augmented reality environment to illustrate the path taken by the generated magnetic field into the TMS patient’s brain.

18. An apparatus according to any preceding claim wherein the magnetic field generator comprises a coil arranged to generate the magnetic field using electromagnetic induction.

19. An apparatus according to any preceding claim wherein the target position is generated using optical tracking system.

20. An apparatus according to any preceding claim wherein the target position is generated using electromagnetic tracking system.

21. An apparatus according to any preceding claim wherein the target position is identified using motor mapping to identify the motor cortex.

22. An apparatus according to any preceding claim wherein the magnetic field generator is adjustable in six degrees of freedom.

23. An apparatus according to Claim 22 wherein the target position remains at least partially visible during adjustment of the magnetic field generator relative to the TMS patient.

24. An apparatus according to any preceding claim wherein data relating to the TMS procedure is captured and stored for use in a future procedure.

25. An apparatus according to any preceding claim wherein the data indicative of the target position on the TMS patient is generated using data stored from a previous procedure.

26. An apparatus according to any preceding claim wherein the augmented reality system comprises a display to display the contents of the augmented reality environment to a user of the apparatus.

27. An apparatus according to any preceding claim wherein the augmented apparatus provides a control panel as part of the augmented reality environment, the control panel configured to receive input to adjust parameters of the TMS procedure.

28. An apparatus according to any preceding claim whereby the system establishes a reference frame of the magnetic field generator relative to the patient via visual identifying features on the magnetic field generator and patient

29. An apparatus according to any preceding claim whereby the apparatus is configured to recognise the shape and orientation of the magnetic field generator from a visual image of the magnetic field generator.

30. An apparatus according to Claim 11 wherein the representative image of the TMS patient’s brain is formed by an MRI image of the TMS patient’s brain

31. An apparatus according to Claim 11 wherein the representative image of the TMS patient’s brain is formed by mapping an MRI image of a standardised brain to that of the TMS patient.

32. An apparatus according to Claim 11 wherein the system is configured to automatically display a representation of the motor cortex on the representative image of the TMS patient’s brain.

33. An apparatus according to Claim 11 wherein the apparatus is configured to provide tools to optimally map an MRI image to the image representative of the TMS patient’s brain.

34. An apparatus according to any of the preceding claims wherein the apparatus is configured to automatically suggest a location for the magnetic field generator and wherein this location can be adjusted by the operator to a desired location.

5

35. An apparatus according to any preceding claim whereby the system is instead used on other body portion of the TMS patient.

36. An apparatus according to any preceding claim wherein the apparatus is configured to use information identifying the position of real world markers on the coil and 10 patient to determine a reference frame for tracking relative movement between the magnetic field generator and the TMS patient.

Intellectual Property Office