WO2005120341A1

WO2005120341A1 - Projection system for use with a medical imaging device

Info

Publication number: WO2005120341A1
Application number: PCT/GB2005/002294
Authority: WO
Inventors: Lucy Abigall Zimmermann
Original assignee: Royal College Of Art
Priority date: 2004-06-11
Filing date: 2005-06-13
Publication date: 2005-12-22

Abstract

A system is described for enabling a person to view images when in a restricted environment, e.g. when undergoing medical treatment in a restricted environment such as an MRI scanner. The system has a projector (12) for forming a first focussed image in the vicinity of the person and optics arranged between the first image and the person to receive light from the first focussed image and to form a second virtual image that is perceived by the person to be located beyond the first image, e.g. beyond the tunnel wall of the MRI scanner, thereby reducing the feeling of claustrophobia.

Description

PROJECTION SYSTEM FOR USE WITH A MEDICAL IMAGING DEVICE

Technical Field

The present invention relates generally to the provision of images to a person in a confined environment, especially when undergoing medical or diagnostic treatment or treatment during research, e.g. within a magnetic resonance imaging (MRI) apparatus.

Background Art

A typical MRI scanning apparatus has torroidal-shaped magnetic coils having a central cavity or tunnel that is typically of the order of 60cm in diameter (providing

43cm of headroom) and 1.7m long. A patient is partly or wholly located within the tunnel and is usually supported on a bed or table that can be slid into and out of the tunnel within the magnetic coils. An MRI scan can take a substantial time to complete and the patient must remain absolutely still during that time. If the patient moves, it may be necessary to repeat that part of the scan.

MRI scanning equipment gives rise to two particular problems, namely claustrophobia and boredom. The restricted space within the MRI tunnel, particularly when the patient's head is within the tunnel, can cause patients suffering from claustrophobia to panic and refuse to start or complete the scan, requiring the scan to be repeated later. At the very least, it is generally unpleasant for all patients (whether suffering from claustrophobia or not) to be confined within such a narrow space for an extended time. The second problem encountered during MRI scans is the lack of stimulus to distract a patient from the noise of the scanner and their feelings about the unpleasantness of the scan and to entertain the patient. The lack of stimulus, together with the unpleasantness of the situation, can lead to the vicious circle of the patient concentrating on their anxiety, which exacerbates the anxiety further.

Numerous proposals have been made to distract patients during an MRI scan. For example, most MRI apparatus are fitted with audio ducts through which music and verbal instructions and information can be piped during the scan. However, that does not solve the problem of claustrophobia and only provides a mild distraction to the patient.

There have been several proposals to enable patients to watch video images during scanning. However, the provision of video images within an MRI scanner is not straightforward since it is not possible to place unshielded electronic equipment containing magnetic materials in the vicinity of an MRI scanner since it will interfere with the operation of the scanner. Accordingly, any electronic equipment that is to be placed in the same room as the MRI scanner must be shielded; most MRI scanner manufacturers require that their approval is sought for the use of such electrical equipment before it can be used in the same room as an MRI scanner.

Prior art proposals to feed a video image to a patient within an MRI scanner in order to distract the patient and relieve boredom include:

US-4,901,141 discloses the feeding of a video image via an optical fibre that passes through a shield to a tapered end; the image is viewed by the patient on the expanded end of the taper, thereby avoiding having any electronic equipment in the vicinity of the MRI scanner. However, the image is small and not very satisfactory

US-5,877,732, US-5,414,459 andUS-5,412,419 disclose the feeding of a video image to a liquid crystal display screen in the vicinity of the patient within the tunnel. This will require the screen and its associated power source to be shielded.

It has also been proposed to view a screen along the tunnel of the MRI scanner, optionally with the aid of a magnifier and/or a mirror. Examples of such arrangements can be found in EP-1205145, US-5,861,865, US-5,864,331, US- 5,825,563, US-5,339,813 and US-5,076,275. However, the tunnel walls will still be visible to a patient and this only adds to the feeling of claustrophobia.

DE3844482 describes a system for providing a visible image to a patient within the tunnel of an MRI scanner; the system has (a) an image generator, which may be a simple lens colleting light from the scanner room, or a camera or a video cassette recorder, (b) an image guide (which may be a series of lenses or a bundle of optical fibres) that conduct the light from the image generator into the MRI tunnel and (c) an eyepiece mounted in front of the patient's eyes. The image generator forms a first image (which is a real image) within the tunnel near the patient's head and the patient views the image through the eyepiece by way of a plane mirror placed between the image and the eyepiece to change the direction of the light path from horizontal, so that it can pass along the tunnel, to vertical so that the patient lying down within the tunnel can see the image. The image is located in the focal plane of the eyepiece, which means that the eyepiece forms a real image and there will be no illusion of space for the patient. The first image can be produced using a light guide, e.g. a bundle of optical fibres or a series of lenses, to conduct light from outside the tunnel.

US 5706070 describes a system for allowing a patent to see an image while undergoing treatment, e.g. in an MRI scanner. The system includes (a) an image generator, e.g. a cathode ray tube (CRT), (b) fibre optic bundles to conduct the image from the image generator into the tunnel of an MRI scanner and (c) an eyeglass assembly worn by the patient to receive the light passing down the optical fibres and to allow the patient to focus on the image; this is done by a lens that forms the light from the fibre optic bundle into a parallel beam that is subsequently reflected by a mirror into the patient's eyes. The parallel beam produced by the eyepieces will form a real image and will not give a feeling of space to the patient.

An article by Cornelissen et al in Spatial Vision, Vol 11, No 1, pp75-81 (1977) describes a system for presenting visual stimuli to a patient during MRI scanning. A

CRT is located in a shielded room and light from the CRT screen is focussed by a zoom lens on one end of a bundle of optical fibres, which conducts the image into the tunnel of an MRI scanner and forms an image at the other end of the optical fibre bundle. This image is observed by the patient through a magnifying eyepiece. Since the CRT is located in the scanning room, the optical fibres must be fed through a hole in a screening wall separating the MRI equipment from a control room, which makes the installation of the equipment expensive, especially the retro-fitting of such equipment to already existing MRI scanner rooms.

Although the above proposals can distract the patient and relieve boredom, they do not necessarily deal with the unease felt by most patients at being in a confined space or claustrophobia in extreme cases, other than by means of distraction. In other words, the patient is still aware of the presence of the narrow tunnel in the MRI scanner.

The shielding of electronic equipment in the vicinity of MRI scanners is exceptionally expensive. The present invention provides a relatively inexpensive method of providing a video image to a patient within a confined space that avoids the necessity of shielding and, in addition, provides the patient with an illusion of space to obviate the feeling of unease at being confined or, in extreme cases, claustrophobia. The present invention can be used in existing MRI facilities without substantial alteration of the facility.

Disclosure of Invention

According to the present invention, there is provided a system for enabling a person to view images when in a restricted environment, e.g. when undergoing medical treatment, exploration or diagnosis in a restricted environment such as an MRI scanner, the system having a location for the person, e.g. a patient station, wherein the system comprises: an imaging arrangement for forming a first focussed image, the imaging arrangement comprising: a projector; a lens system arranged to receive light from the projector and to focus it to form the first focussed image; and a reflector arranged to deflect light from the lens towards the optics; and optics; wherein the optics are capable of being arranged between the first image and the said location to receive light from the first focussed image and are such as to form a second image, which is a virtual image, that is perceived by a person in the location to be beyond the first image.

The reflector may be a prism or a mirror. It will preferably be located in the space between the patient station and the wall and accordingly it should be compatible with the medical or diagnostic installation; in the case of an MRI scanner, the mirror should be a dielectric mirror containing no metal.

A screen may be provided onto which the first image is projected. However, a screen is not strictly necessary but is useful in cutting out all light other than the light transmitted by the projector. Preferably, the screen is larger than the first focused image to achieve that. Such an arrangement is highly beneficial when it effectively limits the light reaching the patient in his her field of view to the light from the screen and the patient can then only see the image and not equipment behind the image; since the image appears to be further away from the patient than the boundary of the confined space and the image is seen in isolation, the patient has a feeling of space, thereby reducing the feeling of claustrophobia.

The reflector is preferably arranged in a fixed location relative to the patient station and optimally can be supported on a patient table or bed that supports the patient.

However, the location is preferably adjustable in a direction along the axis of the patient bed (and the MRI tunnel), e.g. it can be mounted on an arm that is held on a slide extending along or parallel to the axis of the bed. Alternatively, it can be supported by the medical installation (e.g. the MRI scanner) itself but this will necessitate adjusting the reflector in accordance with the position of the patient.

Alternatively, the reflector can be incorporated into a pair of goggles or spectacles worn by the patient but this gives rise to problems in aligning the reflector with the projector. Accordingly, securing the reflector to the patient table is preferred.

The screen and the optics may be connected in a carriage so that they move together with respect to the mirror and the patient station to accommodate the different head sizes of patients. Preferably, the mirror, screen and optics are held by a common support with the mirror being in a fixed position and the screen and optics being formed in a single carriage that can be moved with respect to the reflector.

Preferably, the carriage comprises an enclosed box containing the screen and the optics, with the walls of the box being blackened to absorb any light incident on it and to prevent extraneous light from coming into the peripheral view of the patient.

Patients often have spectacles to correct eyesight defects and will need some sort of correction to view the image in the system of the present invention but metallic spectacle frames and/or parts cannot be used in an MRI scanner. In order to accommodate the different eyesight of different patients, the distance between the screen and the optics may be adjustable. Separate adjustable optics can be used for each eye to achieve this, but that is expensive. Alternatively, a range of plastic spectacles of differing power may be provided. A further possibility is to include a sight-correction lens (either for both eyes together or for each eye individually) in front of the screen, which lens could be for example, a liquid-filled lens whose focal length can be adjusted by adjusting the amount of liquid in the lens. Such lenses are well known, see for example GB-2391638, GB-2316767, GB-2333858, GB2184562 and GB-2183059.

The optics can take the form of a single lens that fits over both eyes, in which case the lens should preferably have a cut-out section to accommodate the patient's nose so that the lens has the general shape of a pair of goggles, which can be brought down to a level immediately adjacent to the patient's eyes. Alternatively, the optics can take the form of separate lenses for each eye, in which case, as discussed above, the individual lenses could be adjustable to compensate for the different sight in each of the patient's eyes. Prisms may be used together with these lenses to ensure the agreement between the accommodation of the eyes and the convergence of the eyes (the angle at which the eyes point together) when both eyes are looking at a single image. Alternatively, a separate image can be provided for each eye. In both these cases adjustment is preferably provided to allow for differences in eye separation in different patients. A single lens extending across both the patient's eyes is preferred since no adjustment for different eye separations is necessary. Also, the convergence and accommodation of a single lens agree without the need for additional prisms; each eye does not look through the centre of the lens, but through a part of the lens that is to the side of the centre. The surfaces of this part of the lens are hence not orthogonal to the direction in which the person is looking, but have curvature. This makes the system much simpler.

In order to give the illusion of space, the focal length of the optics is preferably as small as possible, but generally lenses with a focal length approaching or smaller than their diameter are expensive. Accordingly the choice of the focal length is a compromise between cost and focal length. Thus the focal length of the optics is preferably in the range of 120 to 180 mm, e.g. 135-160 mm, such as 140-150mm.

Blinkers may also be provided to cut out any peripheral light entering the patient's peripheral vision from the side.

According to a second aspect of the present invention, there is provided an installation, e.g. a medical installation, comprising: a location for holding a person; a wall facing a patient when present at the patient station a viewing system as defined above, wherein the optics are arranged between the patient station and the wall and the optics are such as to form a virtual image that appears to a person in the location to be behind the wall.

According to a third aspect of the present invention, there is provided a method of providing an image to a person in a confined space between him her and a wall, e.g. to a patient undergoing medical or diagnostic treatment or exploration in a confined space between a patient station and a wall, wherein the method comprises: projecting an image towards the space and focusing the projected light to form a first image, which is a real image, in the said space; forming light from the first image into a second image visible by the person, the second image being a virtual image located beyond the wall as perceived by the person.

Although the invention has been discussed above in connection with the treatment and diagnosis performed on patients, equipment such as MRI scanners are used in research, e.g. to study the activity of the brain and the present invention covers such activity. The invention can also be utilised in other places where a person is confined in a small space.

Brief Description of Drawings

There will now be described, by way of example only, an embodiment according to the present invention with reference to the accompanying drawings in which: Figure 1 is a schematic view of a MRI scanner installation; Figures 2 and 3 are schematic views of the optics, screen and reflector of the viewing system in two different operational positions; Figures 4 and 5 show perspective view of the optics, screens and reflector in two alternative positions; and Figure 6 is a representation of an MRI scanner showing, superimposed, an image that is observable by the patient.

Best Mode of Carrying out the Invention

Referring initially to Figure 1, there is shown a schematic view of an MRI scanner installation. It consists of a first room 10 (the "scan" room) and a second room 20 (the "operator" room). The scan room and the operator room are divided by a partition 15 that includes a window 16 and, as is usual, the partition and the window 15, 16 are shielded against electromagnetic fields from the MRI scanner by means of conductive wires running through them.

The MRI scanner 22 in the scan room 10 includes magnetic coils within a housing 23; the coils have a central bore or tunnel 24 in which the patient is placed during an MRI scan. A patient station 26 is provided for supporting the patient, which is in the form of a table or bed that is moveable to slide the patient in and out of the tunnel 24.

The controls for the MRI scanner are located in operator room 20 and have been omitted because they are known and, in themselves, do not form part of the present invention.

The MRI scanner described above is of standard configuration and is commercially available from several manufacturers.

The viewing system according to the present invention comprises a projector 12 supported on a stand 14 in the operator room 20. It is a commercially standard projector but the focusing lens has been removed and a different focussing lens is placed in the scan room 10. The lens is shown by the reference numeral 18 and is supported on the stand 19. The focal length of the lens 18 will depend on the geometry of the scan room but should be such as to focus the projected image within a viewing head unit 28, as described below. It is necessary to separate the projector 12 from the lens 18 by a relatively large distance in order to provide a small image on a viewing head unit 28, which will be described in detail below. Obviously, it is possible to place the lens 18 and stand 19 within the operator room if necessary but that has the disadvantage of requiring the projector 12 to be spaced at a distance from the window 16 which will mean that the projector will get in the operator's way during operation of the MRI scanner.

To undertake an MRI scan, a patient lies on the patient station 26 with his/her head below the viewing head unit 28, which is supported by an arm 30; the arm is secured to the patient station and will be moved with the patient into the tunnel 24.

The arm 30 can be secured to the patient station 26 on a slide so that it can be moved axially along the patient station 26; in this way, the patient can lie down and the arm and head unit 28, 30 can be slid into position over the head of the patient. Alternatively, if the patient does not wish to use the viewing system, it can be remain spaced away from the patient's head during the scanning operation.

The tunnel has a head room of approximately 43cm above the patient station 26 and a length of 1.67m long. Accordingly, a patient can feel, at best, uneasy being within such a confined space for the duration of the scan and, at worst, can suffer from claustrophobia and refuse to have the scan done. Since MRI scanners cost in excess of $1 million and operating costs exceed $1,000 per hour, a patient's refusal of a scan can be expensive and wasteful of resources. According to the present invention, the formation of a virtual image beyond the tunnel reduces the feeling of claustrophobia and is much more acceptable to patients. This is shown in Figure 6, which shows a patient ready to be pushed into the tunnel 24 of an MRI scanner. The image 40 as seen by the patient has been superimposed on the picture to illustrate its position and its effect of reducing claustrophobia for the patient by virtue of the patient perceiving that the image is spaced further away than the screen 34.

Referring back to Figure 1, the head unit and arm 28, 30 and the lens and stand 18, 19 can all be made of non-metallic materials and accordingly there is no need to provide expensive shielding, which would be necessary if they were made of metallic parts. Obviously, the projector 18 will include metallic parts but it is located in the operator room 20 behind partition and window 15, 16, and so is shielded. Accordingly, there is no need to seek the permission of the manufacturer of the scanning equipment for the inclusion of the head unit 28, arm 30, lens 18 or stand 19 in the scanner room. Because there is no need to shield the components, they can be manufactured relatively cheaply compared to electronic components, such as LCD screens, which are suggested by the prior art and which must be shielded in use. In addition, the system does not use expensive bundles of optical fibres to transfer an image from the operator room 20 to the patient in the scan room 10, and the use of optical fibres also requires that the fibres are passed through the screening wall 15.

The head unit 28 will be described in further detail by reference to Figures 2 and 3, which show the head unit 28 supported on the arm 30 within the tunnel 24; the patient will be supported on the patient station or patient table 26 with his/her head at position 42. The head unit 28 includes a mirror 32, which is fixed to the arm 30 at an angle of 45° to the tunnel axis and a carriage 31 that can be moved vertically up and down a slide 33, e.g. by means of a pre-tensioned linear bearing that supports the weight of the head unit 28, while allowing the head unit to be moved vertically when force is applied to it, e.g. by the patient's or operator's hands. The carriage 31 consists of side walls 29 whose inside surfaces are blackened. The top surface of the carriage is formed as a back-projection screen 34 and the bottom surface is a goggle-shaped lens 36 that fits over the patient's face. The lens 36 is of spherical section, has a focal length of 147 mm and is 140 mm wide at its widest point. Figure 3 shows the carriage 31 having been moved upwardly on slide 33 from the position shown in Figure 2 to accommodate a patient with a larger head. The length of the slide 33 is about 80 mm. In one embodiment, the lens 36 can be moved relative to the screen 34 to accommodate the eyesight of different patients.

In use, the projected light from the lens 18 (shown schematically by arrow A) is reflected by the mirror 32 onto the screen 34. The image is focused on the screen 34 and is smaller than the size of the screen so that the edge of the screen is not seen by the patient.

The movement of the carriage 31 up and down the slide can take the image on the screen 34 out of focus. Likewise, the placing of the head unit 28 at different distances from the projector lens 18 can take the image on the screen 34 out of focus. Therefore a focussing mechanism is provided to ensure that the projected image is focussed on the screen 34. Preferably the focussing is achieved by moving the projector backwards and forwards on the stand 14 and preferably the projector 12 is mounted on rails (not shown) for that purpose and can be driven along the rails by a motor (again not shown). The distance travelled by the projector to bring the image into focus is relatively small, that is to say, if the head unit is moved to increase the light path to the screen 34 by a certain distance (x), the distance that the projector needs to be moved to bring the image into focus is smaller than x. Therefore, the movement of the projector will generally not interfere with the actions of the operator. According to one embodiment, a sensor could be included within the operator room for detecting the degree of focus and providing a feedback to the projector to drive backwards and forwards along the track to bring the image in focus on the screen 34. Any other automatic focusing arrangement could alternatively be used. Obviously, the focussing can also be achieved manually once the patient has been put into the scan position.

The lens 36 is such as to produce a virtual image 40 of the screen (see Figure 6). This virtual image appears to the patient to be located above the top of the tunnel 24, preferably at least 30cm, e.g. at least 40 cm, away from the patient. The optimum distance is approximately 40 to 100cm away from the patient's eyes, but an image at infinity is also acceptable.

Although the lenses 18 and 36 are shown as simple lenses, they can be lens systems made up of two or more individual lenses.

The creation of a virtual image 40 that appears to the patient to be spaced above the roof of the tunnel 24 provides an illusion of space and helps overcome feelings of claustrophobia. The creation of the virtual image is achieved by means of the single lens 36 extending across both of the patient's eyes. However, other arrangements for creating a virtual image that is perceived by the patient to be beyond the roof of the tunnel are also within the scope of the present invention. The optics can be such that a classical virtual image is created beyond the wall of the scanner roof. Alternatively there are various optical techniques that can fool the brain into thinking that an image is spaced far away; an example of such a technique is binocular disparity, as described at page 326 of "Digital Video: An Introduction to MPEG-2" by BG Haskell, A Puri and A.N. Netravali,, published by Chapman + Hall 1997. . Indeed, the use of the single lens 36 covering both eyes can be envisaged as a pair of prisms and small lenses (one prism and lens for each eye) being placed in front of the two eyes which gives an illusion to the patient that the image on the screen 34 is in fact further away than it is. Instead of the single lens 36, a pair of prisms and small lenses can be used to give the same effect. Thus, the virtual image 40 observed by the patient to be beyond the walls of the tunnel (as shown in Figure 6) can be a virtual image created optically or an image perceived by the brain of the patient to be so located.

In the arrangement of Figures 2 and 3, the focal length of the lens 36 is 147 mm and, at its widest, it has a width of 140mm. In this context, the "width" is the dimension of the lens that extends across the patient's face. It is preferred that the focal length is greater than the width since that reduces the cost of the lens. The distance between the lens 36 and the bed 26 is 177 mm in Figure 2 and 257 mm in Figure 3. The mirror 32 has a width of 98 mm and the screen 34 has a width of 160 mm so that the area of the screen is substantially larger than that of the mirror , e.g. at least twice the area and so the first image on the screen will be located on part only of the screen. The parts of the screen that do not carry the image will appear dark to the patient and so the patient will not be able to see anything in a region bordering the image, which increases the sense of space that the patient enjoys since he/she will not be able to see the scanner tunnel in his/her main field of view. The image on the screen will typically be 59 x

44mm.

The dimensions in the Figure 2 and 3 arrangement are as follows: a) between the patient table 26 and the tunnel wall 24 is typically about 430 mm b) the distance between the patient table 26 and lens 36 can vary between 177 mm

(Fig. 2) and 257 mm (Fig. 3) c) distance between the lens 36 and the screen is 118 mm d) the vertical height of the mirror is 45mm e) the clearance between the top of the head unit 28 and the tunnel wall 24 is about 10 mm.

Figures 4 and 5 show the arm 30 and the head unit 28 with the carriage 31 in its lower and upper positions (respectively).

Figures 4 and 5 also show a pair of blinkers 50 that block light coming in from the side. The blinkers 50 may be rigid or semi-rigid, in which case they can be used to raise or lower the carriage 31 on the slide 29. Sound can be piped into the MRI scanner using existing techniques.

The video system can be used to feed readable information or instructions to the patient, which is especially useful when the patient is deaf. Thus, for example, when scanning a heart, the patient must hold his/her breath for certain intervals during the scan and instructions to start and stop holding of breath can be provided in visual form on the screen.

Usually, the image projected will be entertainment to keep the patient from becoming bored and fidgeting.

A substantial advantage of the system of the present invention is that it can be retrofitted to existing MRI scanners since the only modification that is required to the scanner is to attach the head unit and arm 28, 30 to the patient station.

Claims

1 A system for enabling a person to view images when in a restricted environment, e.g. when undergoing medical treatment, exploration or diagnosis in a restricted environment such as an MRI scanner, the system having a location for the person, e.g. a patient station, wherein the system comprises: (a) an imaging arrangement for forming a first focussed image, the imaging arrangement comprising : a projector for projecting an image; a lens system arranged to receive light from the projector and to focus it to form the first focussed image; and a reflector arranged to deflect light from the lens towards the optics.; and (b) optics; wherein the optics are capable of being arranged between the first image and the said location to receive light from the first focussed image and are such as to form a second image, which is a virtual image, that is perceived by a person in the location of the person to be beyond the first image.

2 A system as claimed in claim 1, which further includes a screen placed at the location of the first image, the screen preferably being larger than the first image.

3 A system as claimed in claim 1 or claim 2, wherein the optics and, when provided, the screen are moveable relative to the reflector.

4 A system as claimed in and one of claims 1 to 3, wherein the optics are such that the accommodation and convergence of the eyes of a person at the location agree when looking at the second image via the optics. 5 A system as claimed in any one of claims 1 to 4, wherein the projector is movably mounted, e.g. on rails, whereby the projector can be moved towards and away from the lens system to focus the first image.

6 A system as claimed in claim 5, which includes an autofocus system that senses the state of focus of the first image and a drive mechanism for moving the projector to focus the first image.

7 An installation, e.g. a medical installation, comprising: a location for holding a person; a wall facing a patient when present at the patient station a viewing system as claimed in any one of claims 1 to 6, wherein the optics are arranged between the patient station and the wall and the optics are such as to form a virtual image that appears to a person in the location to be behind the wall.

8 An installation as claimed in claim 7, which includes a transparent shielded window in a wall and wherein the projector is located on one side of the wall and the reflector, the optics, and the person location are located on the opposed side of the wall, the lens system optionally also being provided on the opposed side of the wall.

9 A method of providing an image to a person in a confined space between him/her and a wall, e.g. to a patient undergoing medical or diagnostic treatment or exploration in a confined space between a patient station and a wall, wherein the method comprises: projecting an image towards the space and focusing the projected light to form a first image, which is a real image, in the said space; forming light from the first image into a second image visible by the person, the second image being a virtual image located beyond the wall as perceived by the person. 10 A system for enabling a person to view images when in a restricted environment, e.g. when undergoing medical treatment, exploration or diagnosis in a restricted environment such as an MRI scanner, the system having a location for the person, e.g. a patient station, wherein the system comprises: a screen; an imaging arrangement for forming a first focussed image on the screen; and optics for observing the image on the screen; wherein the optics are capable of being arranged between the screen and the said location to receive light from the first focussed image on the screen and are such as to form a second image, which is a virtual image, that is perceived by a person in the location of the person to be beyond the screen.