GB2623949A

GB2623949A - Patient information solution

Info

Publication number: GB2623949A
Application number: GB2216045.1A
Authority: GB
Inventors: Carlander Erik
Original assignee: Elekta ltd
Priority date: 2022-10-30
Filing date: 2022-10-30
Publication date: 2024-05-08
Also published as: GB202216045D0; WO2024094659A1

Abstract

A system comprising a radiotherapy machine 100 comprising a bore 160 and a projector 200 arranged to project an image onto a surface of the bore. The system may comprise a controller arranged to control the projector to change the position of the image on the bore. The system may comprise a patient positioning system 120 arranged to position a patient within the bore comprising a patient support surface. A method of displaying the image is also provided.

Description

PATIENT INFORMATION SOLUTION

Field

The present disclosure relates to a system including a radiotherapy machine and a projector.

Background

Radiotherapy can be described as the use of ionising radiation, such as X-rays, to treat a human or animal body. Radiotherapy is commonly used to treat tumours within the body of a human or animal patient, or subject. In such treatments, ionising radiation is used to irradiate, and thus destroy or damage, cells which form part of the tumour.

A radiotherapy machine used to create a beam of radiation typically includes a gantry which carries a treatment head including beam delivery components. The treatment head is moveable on the gantry along a circular travel path. A housing is formed around the beam delivery components and other parts of the radiotherapy machine. A bore is created in the housing to allow a patient to be moved into the area inside the circular travel path in order to receive treatment. The bore is essentially a tunnel, which is typically cylindrical in shape.

The patient is positioned lying down, typically face up, on a patient positioning system akin to a bed. The patient positioning system moves the patient through the bore to an appropriate position to receive treatment. Where the treatment area is broad, or there are multiple locations within the body to be treated, the patient positioning system moves the patient between different positions within the bore.

When receiving treatment, all that is usually visible to the patient is the inner surface of the bore. This can create a mildly anxious or other unpleasant sensation in the patient. For example, the patient may feel mildly claustrophobic, bored, or disconnected from the environment or healthcare professionals administering treatment. Furthermore, patients receiving treatment are not able to view screens or other information displays situated elsewhere in the treatment environment and such screens or displays cannot be placed in the path of the radiation beam lest they be damaged. Therefore, information and images cannot be displayed to the patient during treatment.

Summary

An invention is set out in the claims.

Brief description of the drawings

Specific embodiments are now described, by way of example only, with reference to the drawings, in which: Figure la illustrates a radiotherapy machine which can be used in a system according to the present disclosure; Figure lb illustrates a system including a radiotherapy machine and a projector according to the present disclosure; Figure 2 illustrates a field of projection of a projector onto a surface of a bore within a radiotherapy machine according to the present disclosure; Figure 3 illustrates a viewing position of a patient positioned within a bore of a radiotherapy machine, and projection of an image according to the viewing position; Figure 4 illustrates an alternative viewing position of the patient, and projection of an image according to the viewing position; and Figure 5 illustrates an image projected onto an inner surface of the bore according to the present disclosure.

Overview The present disclosure is directed to a system comprising: a radiotherapy machine comprising a bore; and a projector arranged to project an image onto a surface of the bore.

By projecting an image onto the surface of the bore of the radiotherapy machine, the patient can be presented with a view other than that of the plain surface. The content of the image can include content associated with the treatment or content which distracts from the treatment, for example that which distracts, soothes or reassures the patient. The content associated with treatment can include information relating to the status of the radiotherapy machine, the status of a treatment program, the status of an environment of the patient and/or the status of a patient. A medical practitioner can modify the content of the image during treatment.

Optionally, the system further comprises a controller arranged to control the projector to change the position of the image on the surface of the bore. The controller can be the same controller used to control the radiotherapy machine, or a separate controller. For example, the controller can be one dedicated to providing images for the projector -thus the controller can be disposed within the projector itself or within a media device connected to the projector. Alternatively, the controller can be the main controller of the radiotherapy device adapted to also control the projector. The controller may be configured to receive information about the operation or status of the radiotherapy device, which information may be used to determine the form or position of the image, and/or the form or position of content within the image, to be projected onto the surface of the bore.

The system further comprises a patient positioning system arranged to position a patient within the bore, wherein the patient positioning system comprises a patient support surface arranged to support the patient, and the projector is arranged to position the image so that the patient support surface is moveable to face the image. The controller may also be configured to control the patient support surface, or to receive information about the status or position (including orientation) of the patient support surface, which information may be used to determine the form or position of the image, and/or the form or position of content within the image, to be projected onto the surface of the bore.

The projector is arranged to project an image onto any surface of the bore visible to a patient positioned on the patient support surface. The bore typically comprises a cylindrical portion and the projector is arranged to project the image onto this portion. When the patient's head is in the cylindrical portion, the surface of the bore directly faces the patient. Projecting onto a surface of the cylindrical portion allows the patient to view images while the patient's head is positioned inside the bore.

In some radiotherapy machines, the bore widens gradually at the exit end, creating a funnel-shaped portion of the bore surface. The projector can alternatively (or in addition) project the image on to this portion. In this way, the patient is able to view an image even though they are level with a part of the surface of the bore which does not directly face them. In some radiotherapy treatments, for example those in the abdomen or lower body, the patient's head may be positioned beyond the end of the bore. In this case, the projection of the image onto the funnel-shaped portion allows the patient to view an image even though the patient's head is not positioned within the main cylindrical section of the bore.

In some embodiments, the controller is configured to control the projector and/or the patient support surface so that the position and/or content of the image is based on the position (including orientation) of the patient support surface. The controller may be arranged to cause the projector to move the position of the image, and/or move the position of content within the image, based on movement of the patient support surface. This allows the image to be projected onto the parts of the bore most visible to the patient.

In some embodiments, distortion is applied to adapt an input image so that the image projected onto the surface of the bore is of a suitable format, shape or size for viewing by a patient positioned within the bore. That is, the controller is configured to distort an input image and provide a distorted image to the projector to be projected onto the surface of the bore. The degree and/or type of distortion may vary according to the position of the image on the surface of the bore. The image projected onto the surface of the bore may correspond to the input image from the perspective of a viewing position adoptable by a patient positioned on the patient support surface. That is, the image projected on the surface of the bore may appear identical to the input image when viewed from the viewing position. The controller may be configured to apply keystone correction to the input image so that the image projected onto the surface of the bore is of constant width along the length of the bore. Alternatively, or in addition, the controller is configured to projection map the image to the surface of the bore so that the image is 'wrapped' onto the surface.

It is helpful to consider the angles and other geometric relationships between the projected image and the surface of the bore. A first axis between the projector and the centre of the projected image on the surface of bore intersects the bore at a first intersection point and at a first angle relative to the surface normal of the bore at the first intersection point.

If the projector is positioned outside of the bore, the first angle will be a non-zero angle. That is to say that the projector will not be positioned 'head on' to the surface of the bore because in that case the first angle would be zero. By use of a projector positioned outside of the bore, an image can be projected onto the surface of the bore without the projector being subjected to high doses of radiation from the radiation beam or other high intensity fields, such as high intensity magnetic fields in the case of an MRI Linac radiotherapy machine.

If the first angle is non-zero, the controller adapts the image or the content of the image based on a magnitude of the first angle. The controller adjusts an aspect ratio of the projected image (or content thereof) based on the magnitude of the first angle so that the image or content thereof appears to have the normal (i.e. correct or intended) aspect ratio when viewed from the viewing position. It may be understood that when a controller is said to adapt the image, this can refer to an adaptation of the overall picture to be displayed, including the outline, aspect ratio, shape and/or size of the projected (i.e. illuminated) area. When the controller is said to adapt the content of the image, this can refer to an adaptation of displayed lines, colours, text, shapes and other forms contained within the boundaries of the overall projected area.

As described earlier, the patient positioning system is arranged to position a patient within the bore such that the patient adopts a viewing position. For some treatments, the patient remains static relative to the bore once positioned therein. However, the viewing position is often dependent on patient height, location of the treatment area in the patient and other factors. Therefore, the viewing position is often different between treatment cycles(i.e. different between patients and even different for the same patient between treatments). Furthermore, for some treatments (for example those involving multiple treatment areas), the patient moves during the treatment cycle. That is, as well as changing fixed position between treatments, the viewing position can change dynamically during treatments.

In embodiments, the controller is configured to control the projector to adapt the position and/or content of the image based on the viewing position. For example, as the patient travels through the bore or rotates within the bore, the projector can move the image in sync with the moving viewing position of the patient, so that the patient has the image within their field of view without head movement, regardless of the patient's position.

In embodiments, the controller is configured to cause the projector to move the image in the lengthwise direction of the bore (parallel to the cylindrical axis of the bore) when the patient moves through the bore in this direction to match the patient's viewing position. If the projector is stationary, the first angle will change as the patient moves in the lengthwise direction, because the image and its centre (i.e. the first intersection point) will move along with the patient. When the patient is rotated within the bore, the projector is arranged to rotate the position of the image within the bore to match the patient's viewing position. Therefore, the first intersection point (centre of the image) may move as the patient viewing position moves so that the two are aligned during treatment.

A second axis defining the centre of a field of view from the viewing position intersects the bore at a second intersection point and at a second angle relative to the surface normal of the bore at the second intersection point. The second angle can be thought of as a viewing angle, with zero degrees being a 'head on' view.

If the viewing position is inside the cylindrical portion of the bore, the second angle is usually zero since the patient is aligned approximately centrally in the bore and so the viewing position positioned on or close to the cylindrical axis of the bore. In this case, the centre of field of view of the patient forms a virtual line which is aligned with a radius of the bore.

The second angle may be a non-zero angle even though the patient is positioned on or near the cylindrical axis of the bore as described above. For example, if the viewing position is in the frustroconical or funnel-shaped section of the bore, the centre of field of view forms a virtual line that is still aligned with a radius of the bore, but the second angle formed with respect to the surface normal of the bore will be greater than zero and less than 90 degrees, optionally greater than 10 degrees and less than 80 degrees.

In the above cases, the projector is arranged to position the centre of the image at the second intersection point. In this way, the viewing position is aligned with the centre of the image.

If the image is projected onto the frustroconical portion the content of the projected image is adapted based on the magnitude of the second angle. As the second angle increases, so the apparent length of the surface of the bore decreases from the patient's point of view. A surface spline of actual length L viewed at a viewing angle 0 will have an apparent length A=LcoscP. When projecting onto such a surface, the projector adjusts the length of the image to allow the aspect ratio and relative dimensions of the image to appear normal to the patient. The length of the image M as projected onto the surface is M=A/cos0.

Alternatively, the image can remain stationary relative to the bore while showing the patient different content at different positions within the bore. For example, the image extends along the full length of the bore during the entire treatment even though the patient can only see a portion of the image at any one position within the bore. In this case, the content of the image or the position of content within the image, is adapted based on the position of the patient. However, it is preferable that that the projector is arranged to project an image only within the field of view of the patient. Images projected outside of the field of view can distract the patient, detracting from the viewing experience or causing undesirable movement of the patient's head during treatment.

The content of the image can be chosen by the patient or medical practitioner prior to treatment. For a patient interested in or anxious about the radiotherapy process, images can include information about the treatment program, its status or progress, or the status of the radiotherapy machine or the local environment. The medical practitioner administering the treatment is able to modify the content of the image during treatment in order to relay instructions or reassuring messages to the patient. For a paediatric patient, the images can be cartoons or other child-friendly images. For a claustrophobic patient, the image can be expansive scenes, such as landscapes, or images which create an optical illusion of space around the patient. Other images suitable for display to a patient are also envisaged.

Whether or not the image itself is moved, the content of the projected image may be adapted based on the position of the second intersection point. That is, as the patient viewing position is changed, the content of the projected image may also change. At a first position within the bore, the patient views first content and at a second position within the bore, the patient views second content different from the first content. For example, the first content can include information concerning the start of a treatment program and the second content can include information concerning the end of a treatment program. Alternatively, the first and second content are time-separated portions of a time-evolving content, such as a movie.

Use of a laser projector provides a large depth of focus which allows the image quality (sharpness and brightness) to be maintained over the entire length of the surface of the bore without moving the projector relative to the bore even though the projector is not positioned 'head on' to the bore surface.

The projector is placed predominantly oblique to the surface of the bore. That is, for the most part, the projector is not substantially perpendicular to the surface of the bore except over a small range of the length of the second (funnel-shaped or frustroconical) portion. To avoid distortion of the image due to the angle of projection relative to the surface of the bore, the controller (or projector) applies keystone correction to the image. The controller uses the well-known technique of projection mapping to transform an input image so that the projected image is the input image wrapped onto the surface of the bore (i.e. the projected image conforms to the surface of the bore). Optionally, the projected image and/or its content are distorted on the surface to create the optical illusion of a flat image being displayed even when the surface of the bore is angled away from the patient.

Detailed description of the drawings

Figure la shows a radiotherapy system, or device, suitable for delivering, and configured to deliver, a beam of radiation to a patient during radiotherapy treatment. The device and its constituent components will be described generally for the purpose of providing useful accompanying information for the present disclosure. The device shown in Fig. la is in accordance with the present disclosure and is suitable for use with the disclosed systems and apparatuses. While the device in Fig. la is an MR-linac (magnetic resonance linear accelerator), the implementations of the present disclosure may be any radiotherapy machine, for example a linac (linear accelerator) device.

The device 100 shown in Fig. la is an MR-linac. The device 100 comprises both MR imaging apparatus 112 and radiotherapy (RT) apparatus which may comprise a linac device. The MR imaging apparatus 112 is shown in the diagram in a partially cut away perspective manner. In operation, the MR scanner produces MR images of the patient, and the linac device produces and shapes a beam of radiation and directs it towards a target region within a patient's body in accordance with a radiotherapy treatment plan. Fig. la does not show the usual 'housing' which would cover the MR imaging apparatus 112 and RT apparatus in a commercial setting such as a hospital.

The MR-linac device shown in Fig. la comprises a source 102 of radiofrequency (RF) waves, a waveguide 104, an electron source 106, a radiation source 103, a collimator 108 such as a multi-leaf collimator configured to collimate and shape the beam, MR imaging apparatus 112 (shown partially cut away), and a patient support surface 114. In use, the device would also comprise a housing (not shown) which, together with the ring-shaped gantry, defines a bore. The patient support surface 114 is moveable and can be used to support a patient and move them, or another subject, into the bore when an MR scan and/or when radiotherapy is to commence. The MR imaging apparatus 112, RT apparatus, and a patient support surface actuator are communicatively coupled to a controller or processor. The controller is also communicatively coupled to a memory device comprising computer-executable instructions which may be executed by the controller.

The RT apparatus comprises a radiation source 103 and a radiation detector (not shown). Typically, the radiation detector is positioned diametrically opposed to the radiation source 103. The radiation detector is suitable for, and configured to, produce radiation intensity data. In particular, the radiation detector is positioned and configured to detect the intensity of radiation which has passed through the subject. The radiation detector may also be described as radiation detecting means and may form part of a portal imaging system.

The radiation source 103 may comprise a beam generation system. For a linac, the beam generation system may comprise a source 102 of RF waves, an electron source 106 such as an electron gun, and a waveguide 104. The radiation source 103 is attached to the rotatable gantry 116 so as to rotate with the gantry 116. In this way, the radiation source 103 is rotatable around the patient so that a treatment beam 110 can be applied from different angles around the gantry 116. In a preferred implementation, the gantry is continuously rotatable. In other words, the gantry can be rotated by 360 degrees around the patient, and in fact may continue to be rotated past 360 degrees. The gantry may be ring-shaped. In other words, the gantry may be a ring-gantry so as to allow the radiation source to travel in a circular path around the patient.

The source 102 of radiofrequency waves, such as a magnetron, is configured to produce radiofrequency waves. The source 102 of radiofrequency waves is coupled to the waveguide 104 via a circulator 118 and is configured to pulse radiofrequency waves into the waveguide 104.

Radiofrequency waves may pass from the source 102 of radiofrequency waves through an RF input window and into an RF input connecting pipe or tube. The electron source 106 is also coupled to the waveguide 104 and is configured to inject electrons into the waveguide 104. In the electron source 106, electrons are thermionically emitted from a cathode filament as the filament is heated. The temperature of the filament controls the number of electrons injected. The injection of electrons into the waveguide 104 is synchronised with the pumping of the radiofrequency waves into the waveguide 104. The design and operation of the source 102 of radiofrequency waves, the electron source 106 and the waveguide 104 is such that the radiofrequency waves accelerate the electrons to very high energies as the electrons propagate through the waveguide 104.

The design of the waveguide 104 depends on whether the linac accelerates the electrons using a standing wave or travelling wave, though the waveguide typically comprises a series of cells or cavities, each cavity connected by a hole or 'iris' through which the electron beam may pass. The cavities are coupled in order that a suitable electric field pattern is produced which accelerates electrons propagating through the waveguide 104. As the electrons are accelerated in the waveguide 104, the electron beam path is controlled by a suitable arrangement of steering magnets, or steering coils, which surround the waveguide 104. The arrangement of steering magnets may comprise, for example, two sets of quadrupole magnets.

Once the electrons have been accelerated, they may pass into a flight tube. The flight tube may be connected to the waveguide by a connecting tube. This connecting tube or connecting structure may be called a drift tube. The electrons travel toward a heavy metal target which may comprise, for example, tungsten. Whilst the electrons travel through the flight tube, an arrangement of focusing magnets act to direct and focus the beam on the target.

To ensure that propagation of the electrons is not impeded as the electron beam travels toward the target, the waveguide 104 is evacuated using a vacuum system comprising a vacuum pump or an arrangement of vacuum pumps. The pump system is capable of producing ultra-high vacuum (UHV) conditions in the waveguide 104 and in the flight tube. The vacuum system also ensures UHV conditions in the electron gun. Electrons can be accelerated to speeds approaching the speed of light in the evacuated waveguide 104.

The radiation source 103 is configured to direct the treatment beam 110 of therapeutic radiation toward a patient positioned on the patient support surface 114. The radiation source 103 may therefore also be referred to as a therapeutic radiation source. The radiation source 103 may comprise a heavy metal target towards which the high energy electrons exiting the waveguide are directed. When the electrons strike the target, X-rays are produced in a variety of directions. A primary collimator may block X-rays travelling in certain directions and pass only forward travelling X-rays to produce the treatment beam 110. The X-rays may be filtered and may pass through one or more ion chambers for dose measuring. The beam can be shaped in various ways by beam-shaping apparatus, for example by using the multi-leaf collimator 108, before it passes into the patient as part of radiotherapy treatment.

In some implementations, the radiation source 103 is configured to emit either an X-ray beam or an electron particle beam. Such implementations allow the device to provide electron beam therapy, i.e. a type of external beam therapy where electrons, rather than X-rays, are directed toward the target region as the therapeutic radiation. It is possible to 'swap' between a first mode in which X-rays are emitted and a second mode in which electrons are emitted by adjusting the components of the linac. In essence, it is possible to swap between the first and second mode by moving the heavy metal target in or out of the electron beam path and replacing it with a so-called 'electron window'. The electron window is substantially transparent to electrons and allows electrons to exit the flight tube.

The subject or patient support surface 114 is configured to move between a first position substantially outside the bore, and a second position substantially inside the bore. In the first position, a patient or subject can mount the patient support surface. The patient support surface 114, and patient, can then be moved inside the bore, to the second position, in order for the patient to be imaged by the MR imaging apparatus 112 and/or imaged or treated using the RT apparatus. The bore may hence lie about a portion of space that is suitable for receiving at least a portion of a patient -a patient receiving space. The movement of the patient support surface is effected and controlled by a patient support surface actuator, which may be described as an actuation mechanism. Together, these components may be described as a patient positioning system, or patient positioning apparatus, which may comprise other components. The actuation mechanism is configured to move the patient support surface in a direction parallel to, and defined by, the central axis of the bore. The terms subject and patient are used interchangeably herein such that the patient support surface can also be described as a subject support surface. The patient support surface may also be referred to as a moveable or adjustable couch or table.

The radiotherapy machine (also known as a radiotherapy device or apparatus) shown in Fig. la also comprises MR imaging apparatus 112. The MR imaging apparatus 112 is configured to obtain images of a subject positioned, i.e. located, on the patient support surface 114. The MR imaging apparatus 112 may also be referred to as the MR imager. The MR imaging apparatus 112 may be a conventional MR imaging apparatus operating in a known manner to obtain MR data, for example MR images. The skilled person will appreciate that such an MR imaging apparatus 112 may comprise a primary magnet, one or more gradient coils, one or more receive coils, and an RF pulse applicator. The operation of the MR imaging apparatus is controlled by the controller.

The controller is a computer, processor, or other processing apparatus. The controller may be formed by several discrete processors; for example, the controller may comprise an MR imaging apparatus processor, which controls the MR imaging apparatus 110; an RT apparatus processor, which controls the operation of the RT apparatus; and a subject support surface processor which controls the operation and actuation of the patient support surface. The controller is communicatively coupled to a memory, e.g. a computer readable medium.

The linac device also comprises several other components and systems as will be understood by the skilled person. For example, in order to ensure the linac does not leak radiation, appropriate shielding is also provided.

Figure lb illustrates a system including a radiotherapy machine 100 and a projector 200 according to the present disclosure. The radiotherapy machine 100 of Figure lb can be an MR linac as shown in Figure la or can be any other kind of radiotherapy machine, for example a conventional linac radiotherapy machine. The projector 200 is configured to project an image onto a surface of a bore 160 of the radiotherapy machine 100. A patient positioning system 120 is configured to position a patient (not shown in Figure lb) within the bore 160 in order to receive treatment.

In contrast with the depiction of the radiotherapy machine in Figure la, the depiction of the radiotherapy machine shown in Figure lb includes a housing 130 configured to house the beam generation and beam delivery components of the radiotherapy machine. The housing 130 comprises an approximately cuboid (orthotope) structure with a vertically oriented front face 130a and rear face 130b between which faces the bore 160 extends.

As with the radiotherapy machine depicted in Figure la, the beam delivery components are mounted to a ring-shaped gantry 140 which is configured to position the beam delivery components to deliver the beam from different angles toward the patient 300. The housing 130 around the inside of the gantry 140 defines an inner surface 150 of the bore 160. The bore 160 has a substantially cylindrical, or tunnel-like, shape, with a central axis extending horizontally and perpendicular to the front and rear faces 130a, 130b. The inner surface 150 comprises a first portion 151 and a second portion 152. The first portion 151 is cylindrical and the second portion 152 is a gradual widening of the first portion 151 to form a substantially frustroconical or funnel-shaped part.

The patient positioning system 120 comprises a moveable patient support surface 121 configured to position a patient, or other subject, within the bore 160. The support surface 121 is configured to move the patient 300 relative to the beam delivery components, by moving the patient 300 into and through the bore 160.

The projector 200 is positioned outside of the bore 160 and outside of the housing 130 of the radiotherapy machine. This minimises exposure of the projector 200 to the radiation beam. The projector 200 is a conventional laser projector.

The patient positioning system 120, projector 200 and radiotherapy machine 100 are communicatively coupled to a controller (not shown). The controller is arranged to control and monitor the position and orientation of the moveable patient support surface 121. The controller is also arranged to control the radiotherapy machine 100 including monitoring and execution of the treatment program. The controller is also arranged to control the projector 200. The controller is arranged to control the projector 200 based on the position and/or orientation of the moveable support surface 121 relative to the bore 160. Alternatively, or in addition, the controller is arranged to control the projector 200 based on the status of the radiotherapy machine, the status of the environment and/or the status of the treatment program. The controller is arranged to cause the projector to adapt the image or content of the image in any of the ways described herein.

The controller is a computer, processor, or other processing apparatus. The controller may be formed by several discrete processors; for example, the controller may comprise radiotherapy machine processor, which controls the radiotherapy machine; a patient support surface processor which controls the operation and actuation of the patient support surface; and a projector processor which controls the operation of the projector. The controller is communicatively coupled to a memory, e.g. a computer readable medium. The memory comprises instructions which, when executed by a system including the projector and the controller (and optionally also the radiotherapy machine and/or patient positioning system), cause the system to carry out any of the methods or functions described herein. A radiotherapist, or other medical practitioner, can interact with the controller through a user interface (not shown), such as a graphical user interface, to program or control operation of the radiotherapy machine, the patient support surface and the projector to perform any of the methods or functions described herein.

Figure 2 illustrates a field of projection of a projector 200 onto a surface of a bore 160 within a radiotherapy machine 100 according to the present disclosure. Figure 2 is a cross-sectional view of the system shown in Figure lb, with the cross section in a vertical plane bisecting the bore wherein the plane lies along the cylindrical axis of the bore 160.

The bore 160 of the radiotherapy machine 100 will now be described in more detail. As described earlier, the bore 160 comprises the first portion 151 and second portion 152, which are cylindrically-and frustroconically-(or funnel-) shaped, respectively.

The first portion 151 has a first diameter which is substantially constant along the length of the bore 160, the length dimension being parallel to the cylindrical axis of the bore. The length of the first portion 151 is of the order of the height of the average adult.

The second portion has a diameter which gradually increases along its length between the first diameter immediately adjacent to the first portion and a second diameter immediately adjacent to the rear face 130b of the housing 130. The length of the second portion is of the order of around 1/8 the length of the second portion.

The first portion 151 is adjacent to and contiguous with the second portion 152. Thus, the second portion 152 is smoothly connected to the first portion 151 to the extent that the bore surface 150 is substantially continuous (i.e. without any step or gap between the first and second portions).

The bore 160 has a front end proximate to the front face 130a of the housing and a rear end proximate to the rear face 130b of the housing 130. The patient positioning system 120 carries a patient into the bore by entering the bore via the front end. The second portion 152 is located at the rear end of the bore 160 relative to the usual direction of travel of a patient through the bore (i.e. the end of the bore 110 furthest from the entry point of the patient positioning system 120 into the bore). The second portion 152 provides a smooth (i.e. less abrupt) angular transition from the first cylindrical portion 151 of the surface 150 to the rear face 130b of the housing 130.

In the embodiment shown in Figure 2, the projector 200 is a laser projector. The laser projector 200 comprises one or more monochromatic lasers, an optical scanning system, one or more focussing elements and one or more magnification elements (not shown). The structure of the electronic, optical and other components of a laser projector and their detailed operation, as well as the configuration of the laser projector for projecting an image onto a surface, will be familiar to the skilled person such that a detailed description is not required.

The projector 200 is positioned outside of the bore 160 and at a distance from the rear face 130b of the housing 130; in other words, the projector is located behind the rear end of bore 160. The projector 200 is arranged to project an image 240 onto the inner surface 150 of the bore 160. More particularly, the projector 200 is arranged to project the image 240 onto sections of the first portion 151 and second portion 152 of the surface 150. Each section is defined as a swept-out arc portion of the circumference of the bore A first axis 210 between the projector 200 and the centre of the projected image on the surface 150 of the bore intersects the bore 160 at a first intersection point 220 and at a first angle 230 relative to the surface normal of the bore 160 at the first intersection point 220. In the embodiment shown in Figure 2, the projector 200 is angled such that it projects onto the upper part of the inner surface 150 of the bore 160 such that the first intersection point 220 is approximately in the middle of the bore 160 (midway between the front and rear ends of the bore 160) and the first angle 230 is approximately 60 degrees. The projector 200 is arranged such that the projection field covers the entire length of the inner surface 150 of the bore including the entire length of the first 151 and second 152 portions, the length direction being defined as parallel to the cylindrical axis of the bore 160.

The position of the projected image 240 on the surface 150 is modified based on the position of the patient 300 within the bore 160.

The laser projector 200 maintains focus and illumination strength over a wide range of distances from the projector 200. This ensures that focus and brightness of the image 240 projected at different locations on the inner surface 150 of the bore 160 is consistent and therefore that the image quality is independent of image position within the bore 160. This also allows the projector 200 to remain outside the bore 160.

Figures 3 and 4 are close ups of the cross-sectional view of the system of Figure 2. Figures 3 and 4 each illustrate a patient 300 positioned within the bore 160 so that the patient adopts a viewing position VP, and projection of an image 240 according to the viewing position VP.

As described earlier, the support surface 121 (not shown in Figure 3) is used to move the patient 300 relative to the beam delivery components, by moving the patient 300 into and through the bore 160. The support surface 121 is configured to position the patient 300 within the bore 160 such that the patient adopts the viewing position VP. The viewing position VP is defined as the midpoint between the patient's eyes.

A second axis 310 defines a centre of a field of view of the patient 300 from the viewing position. The second axis 310 intersects the bore 160 at a second intersection point 320 and a second angle 330 relative to the surface normal of the bore 160 at the second intersection point 320. In Figure 3, the patient position is such that their view of the surface of the bore is 'head on' and the second angle is therefore approximately zero degrees. However, as will be seen in Figure 4, in other patient positions within the bore, depending on the orientation of the surface relative to the patient, the second angle 330 may be a non-zero angle.

As described with reference to Figure 2, a first axis 210 between the projector 200 and the centre of the projected image 240 on the surface 150 of the bore intersects the bore 160 at a first intersection point 220 and at a first angle 230 relative to the surface normal of the bore 160 at the first intersection point 220. The projector 200 is configured to project an image 240 onto the surface 150 of the bore 160 such that the projected image 240 lies within the field of view of the patient 300 in the viewing position. More particularly, the second intersection point 320 is located within the section of the surface 150 of the bore onto which the image 240 is projected.

The embodiment shown in Figure 3 shows the patient 300 in a first viewing position, such that the second intersection point 320 is approximately collocated with the first intersection point 220. The second angle 330 is approximately zero as the surface normal of the bore 160 at the second intersection point 320 is colinear with the second axis 310. In this embodiment, the first and second intersection points 220, 320 are located on the first portion 151 of the surface of the bore 150.

The projected image 240 lies completely within the field of view of the patient 300. The field of view of the patient 300 covers a section of the inner surface 150 of the bore. More particularly, the field of view of the patient 300 covers a section of the field of projection which contains at least a part of the image.

Projection mapping allows projection of an image onto non-uniform surfaces, for example curved surfaces, so that the image conforms to the surface. Projection mapping is a known technique in which the image projected is manipulated by the projector so that appears in proper proportion on the surface onto which it is projected. A contour map of the surface and the relative positions of the project and the surface are used to calculate perform the projection mapping. In the embodiments shown in Figures 3, 4 and 5, the projector is configured to use projection mapping to ensure that the projected image conforms to the inner surface of the bore. More particularly, the laser projector 200 is configured to use projection mapping to project an image 240 onto the first and/or second portions 151, 152 of the inner surface of the bore 160 so that the image 240 conforms thereto.

Figure 4 shows the patient 300 adopting a second viewing position VP, such that the first and second intersection points 220, 320 are collocated on the second portion of the surface 152 of the bore 160. The projector 200 is arranged to modify the position of the image 240 based on the viewing position. More particularly, the projector 200 is configured to modify the location of the first intersection point 220 according to the location of the second intersection point 320. The location of the second intersection point 320 can be changed as the support surface 121 (not shown in Figure 4) moves to adjust the position of the patient 300 (and hence the viewing position VP) within the bore 160.

In the embodiment shown in Figure 4, the viewing position VP adopted by the patient 300 is further towards the rear of the bore 160 than in the embodiment shown in Figure 3, and correspondingly the position of the image 240 on the surface of the bore 160 is further towards the rear face 130b of the housing 130.

The projector 200 is positioned both behind the bore 160 and behind the patient's head, ensuring that no component vector of the first axis 210 lies in an opposite direction to a line of sight of the patient from the viewing position VP. Thus, light emitted from the projector directly is never directed towards the eyes of the patient 300. This allows a projector, particularly a laser projector, to be used safely as pad of the system including the radiotherapy machine 100.

Figure 5 illustrates an image projected onto the surface of the bore according to the present disclosure. Figure 5 is an oblique projection of the radiotherapy machine 100 depicted in Figure lb showing a portion of the rear face 130b of the housing 130 and a view through the bore showing the internal surface 150 of the bore 160.

In the embodiment shown in Figure 5, the image 240 is projected onto the entire length of the bore but covers only the section of the circumference of the bore which lies above the patient. The image 240 has a part projected onto the first portion 151 and a part projected onto the second portion 152 of the surface of the bore 160. Only a part of the image 240 is within the field of view of the patient. The intersection between the field of view of the patient 300 and the image 240 is demarcated by dashed lines on the surface 150 of the bore 160.

The projector (not shown in Figure 5) is placed predominantly oblique to the surface 150 of the bore 160. That is, for the most part, the projector is not substantially perpendicular to the surface 152 of the bore 160 except over a small range of the length of the second portion 152. To avoid distortion of the image due to the angle of projection relative to the surface of the bore, keystone correction is applied to the image. Keystone correction involves correcting the image so that its width does not vary along its length. The degree of keystone correction required is dependent on the magnitude and sign of the first angle (see Figures 3 and 4) and the distance of the first intersection point 220 from the projector. If keystone correction is not applied, pads of the image may have a width (in the circumferential direction on the surface 150) that is greater than the width of other parts of the image. The width of the image on parts of the surface closer to the projector is less than the width of the image on parts of the surface further from the projector. Such distortion of the image due to the angle of projection therefore differs between the first portion 151 and second portion 152.

It is helpful to define a normal orientation of the image 240 as having a top end 240a which is closer to the rear end of the bore than the bottom end 240b, since this is how the image is oriented from the patient's perspective when positioned in the bore. It is also helpful to define that in the first portion 151, the first angle is positive, but in the second portion 152 the first angle 230 becomes negative in the part of the second portion 152 closest the rear face 130b.

In the first portion 151, since the first angle 230 is positive and the projector 200 is positioned behind the rear end of the bore, the distortion is such that the bottom end of the image 240 would be greater in width than the top end. Keystone correction ensures that the width of the image is uniform along the full length of the first portion 151.

In the part of the second portion 152 closest the rear face 130b of the housing 130, since the first angle 230 is negative and the rear-most portion of the second portion 152 is furthest from the projector, the distortion is such that the top end of the image 240 would be greater in width than the bottom end. Keystone correction ensures that the width of the image is uniform along the full length of the second portion 152. Thus, keystone correction may be applied in opposite directions depending on the orientation of the surfaces of the bore relative to the projector and the angle of projection.

The projector also uses projection mapping to ensure that the projected image conforms to the surface of the bore. Keystone correction and projection mapping are known in the art and therefore a detailed explanation of such techniques is omitted from this disclosure.

In some embodiments, the projection-mapped and/or keystone-corrected image is deliberately distorted on the surface of the bore to take into account orientation of the patient 300 relative to the surface 150. This can be to give the optical illusion of a flat image arranged perpendicular to the line of sight of the patient when the surface 150 of the bore 160 is not perpendicular to the line of sight of the patient On other words when the second angle 330 described with reference to Figures 3 and 4 is non-zero). In the embodiment shown in Figures lb and 2-5, the patient line of sight when inside the first portion 151 is perpendicular to the surface (i.e. the second angle 330 is zero) and therefore no such deliberate distortion is required. However, the patient line of sight when in the second portion 152 is not perpendicular to the surface (i.e. the second angle 330 is non-zero) and therefore the deliberate distortion may be applied to the image in the second portion to provide the optical illusion of a flat image arranged perpendicular to the line of sight of the patient. To achieve this optical illusion, the image 240 and the contents of the image may be stretched in the longitudinal direction (top to bottom of the image 240) in the second portion 152.

An improved optical illusion can be created by first mapping an undistorted image onto a virtual plane in the 3D space between the patient 300 and the surface 150, the virtual plane being perpendicular to the line of sight of the patient. The mapped image on the virtual plane together with knowledge of the position of the viewpoint and the relative position and orientation of the surface 150 relative to the viewpoint and mapped image can be used to project a virtual image onto the surface 150. For example, straight reference lines extending from the viewing position through reference points in the mapped image on the virtual plane can be used to map those reference points to positions on the surface 150 at the points of intersection of the reference lines and the surface 150. The virtual image can then be recreated by the projector 200 on the surface 150 using known projection mapping techniques. In this case, software is used to map the corners of the image or video to the surface of the bore. The image is then placed on the surface. Alternatively, the entire bore surface is mapped in 3D the image is projected and masked back onto its framework. The next step is masking, using opacity templates to "mask" the exact shapes and positions of the different elements of the surface of the bore. In 3D mapping, coordinates are defined for where the surface of the bore is positioned in relation to the projector. The projector's orientation and position relative to the surface of the bore, together with the projector lens specification, result in a determined virtual scene and the software maps the image onto the surface of the bore so that, when projected, the image conforms to the surface of the bore.

In Figure 5, the contents of the image 240 include computer or arcade game graphics designed to distract the patient's attention from the treatment or the environment. In other embodiments, as described earlier, other images, either stills or video, may be used instead.

Those skilled in the art will recognise that a wide variety of modifications, alterations, and combinations can be made with respect to the above described examples without departing from the scope of the disclosed concepts, and that such modifications, alterations, and combinations are to be viewed as being within the ambit of the disclosed concepts.

Those skilled in the art will also recognise that the scope of the invention is not limited by the examples described herein but is instead defined by the appended claims.

Claims

CLAIMS: 1. A system comprising: a radiotherapy machine comprising a bore; and a projector arranged to project an image onto a surface of the bore.
2. The system of claim 1, further comprising a controller arranged to control the projector to change the position of the image on the surface of the bore.
3. The system of claim 1 or 2, further comprising a patient positioning system arranged to position a patient within the bore, wherein the patient positioning system comprises a patient support surface arranged to support the patient, and the projector is arranged to position the image so that the patient support surface is moveable to face the image.
4. The system of claim 3, wherein the controller is configured to control the projector and/or the patient support surface so that the position and/or content of the image is based on the position of the patient support surface.
5. The system of any of claims 3 or 4, wherein the controller is arranged to cause the projector to move the position of the image, and/or move the position of content within the image, based on movement of the patient support surface.
6. The system of any of claims 2, 4 or 5, or claim 3 when dependent on claim 2, wherein the controller is configured to distort an input image and provide a distorted image to the projector to be projected onto the surface of the bore.
7. The system of claim 6, wherein the degree and/or type of distortion varies according to the position of the image on the surface of the bore.
8. The system of claim 6 or 7, wherein the image projected onto the surface of the bore corresponds to the input image from the perspective of a viewing position adoptable by a patient positioned on the patient support surface.
9. The system of any of claims 6-8, wherein the controller is configured to apply keystone correction to the input image so that the image projected onto the surface of the bore is of constant width along the length of the bore, and/or wherein the controller is configured to projection map the image to the surface of the bore.
10. The system of any preceding claim, wherein a first axis between the projector and the centre of the projected image on the surface of bore intersects the bore at a first intersection point and at a first angle relative to the surface normal of the bore at the first intersection point, wherein the first angle is a non-zero angle.
11. The system of claim 10, wherein the projected image and/or content of the projected image is adapted based on the magnitude of the first angle.
12. A method of displaying an image on a surface of a radiotherapy machine comprising: projecting an image onto the surface of a bore of the radiotherapy machine.
13. The method of claim 12, wherein the position of the image is moved on the surface of the bore.
14. The method of claim 12 or 13, wherein the radiotherapy machine comprises a patient positioning system arranged to position a patient within the bore, wherein the patient positioning system comprises a patient support surface arranged to support the patient, wherein the image is positioned so that the patient support surface is moveable to face the image.
15. The method of claim 14, wherein the position and/or content of the image is adapted based on the position of the patient support surface.
16. The method of claim 14 or 15, wherein the position of the image, and/or the position of content within the image, is moved based on movement of the patient support surface.
17. The method of any of claims 12-16, wherein an input image is distorted to provide the image projected onto the surface of the bore.
18. The method of claim 17, wherein degree and/or type of distortion is varied according to the position of the image on the surface of the bore.
19. The method of claim 17 or 18, wherein the image projected onto the surface of the bore corresponds to the input image from the perspective of a viewing position adoptable by a patient positioned on the patient support surface.
20. The method of any of claims 17-19, wherein keystone correction is applied to the input image so that the image is projected onto the surface of the bore is of constant width along the length of the bore, and/or wherein the image is projection mapped to the surface of the bore.
21. A system comprising a projector and a controller, wherein the system is configured to perform the method of any of claims 12-20.
22. A computer-readable storage medium comprising instructions which, when executed by a system comprising a projector and a controller, cause the system to carry out the method of any of claims 1221.