Infra-red vascular angiography system

We claim:

1. An infra-red vascular angiography system comprising a readily displaceable camera including infra-red and visible range optical assemblies and infra-red and visible range detectors; the infra-red optical assembly being of high sensitivity for receiving and transmitting with minimal distortion an infra-red image of an object within an angular range of substantially .+-.45.degree. with respect to a line perpendicular to the object; the infra-red range detector detecting the infra-red image transmitted from said optical assembly, in an infra-red wavelength range substantially between 8 to 12 micrometers, and converting it into a first set of successive electric output signals; a first video imaging device coupled to said infra-red range detector for digitizing said first set of output signals and converting them into a first set of successive digitized video image frames or successive portions thereof; the visible range optical assembly receiving and transmitting a visible image in coordination with said infra-red optical assembly and having a field of view with respect to said object which covers at least that of said infra-red assembly; the visible range detector converting the transmitted visible image into a second set of successive electric output signals; a second video imaging device coupled to said visible range detector for digitizing said second set of successive electric output signals into a second set of successive digitized video image frames or successive portions thereof; an image processor coupled to said first and second imaging devices adapted to receive said first and second successive video frames or successive portions of video frames to process them and form first and second sets of enhanced video images; and a switching device coupled to said image processor, for routing either or both of said sets of enhanced video images to a display device coupled to said image processor, for enabling an operator to readily correlate the infra-red image with the visible image of said object.

2. A system according to claim 1, and furthermore provided with a displacing handle fitted to said camera, said switching device being carried by said handle and being actuatable for switching purposes upon sensing of a contact or absence of contact with said handle.

3. A system according to claim 2, wherein said switching device is in the form of a micro-switch.

4. A system according to claim 2, wherein said switching device is an optical switch.

5. A system according to claims 1 or 2, wherein said visible range detector, said second video imaging device and at least a portion of said visible range optical assembly are included in a video camera.

6. A system according to claim 5, wherein said video camera is a CCD camera.

7. A system according to claim 1, wherein said switching device is keyboard operated.

8. A system according to claim 1, wherein said switching device is vocally operated.

9. A system according to claim 1, wherein said optical assemblies are each provided with an auto-focussing assembly.

10. A system according to claim 9, wherein the automatic focussing assembly of the infra-red optical assembly is enslaved to the automatic focussing assembly of the visible range optical assembly.

11. A system according to claim 1, wherein said display device displays said sets of enhanced video images respectively as thermal and visible range display zones with said thermal range display zone being wholly located within the visible range display zone.

12. A system according to claim 11, wherein said thermal range display zone is delineated within the visible range display zone by markings.

13. A system according to claim 11, wherein said thermal range display zone and said visible range display zone maintain a substantially constant spatial relationship with respect to each other independent of a location of the camera.

14. A system according to claim 13, wherein the thermal range display zone and the visible range display zone have a common center.

15. A system according to claim 1, wherein said optical assemblies have optical components in common.

16. A system according to claim 15, wherein a beam splitter assembly is included among said optical components and is adapted to receive radiation comprising infra-red and visible range constituents; the beam splitter being adapted to separate said received radiation into an infra-red constituent directed to the infra-red assembly, and a visible range constituent directed to the visible range assembly.

17. A system according to claim 1, further comprising a filter for filtering out radiation wavelength ranges other than predetermined visible and infra-red wavelength ranges.

18. A system according to claim 1 wherein the infra-red optical assembly comprises an infra-red lens which is adapted to be spaced from the object in a range of substantially 0.30 m to 100 m and wherein there is furthermore provided a first auto-focussing assembly for enhancing the infra-red image transmitted to said infra-red range detector.

19. A system according to claim 18, wherein said visible range optical assembly furthermore comprises a second auto-focussing assembly.

20. A system according to claim 19, wherein said first auto-focussing assembly is enslaved to the second.

21. A system according to claim 1 and furthermore comprising an auxiliary portable probe for viewing and transmitting an infra-red image of a region of said object closely adjacent said probe and comprising a housing; at least a further infra-red lens forming a window in said housing and adapted to be juxtaposed with respect to said region; an optical fiber assembly having a first end portion located within said housing remote from said window and having a second and opposite end portion juxtaposed with respect to said infra-red range detector; and an optical system located in said housing and adapted to project an infra-red image transmitted by said window onto said first end portion of said optical fiber assembly.

22. A system according to claim 21, wherein said auxiliary portable probe is in the form of an elongated, substantially cylindrical probe comprising a tubular housing having at its front end an infra-red window.

23. A system according to claim 21, wherein said auxiliary portable probe further comprises a lens system which serves for focussing of the image onto a bundle of optical fibers protruding from the housing.

24. A system according to claim 23, wherein the opposite end portion of the bundle is secured to a coupling unit which is provided with means facilitating readily and releasably coupling to an appropriate location in a camera housing.

25. A system according to claim 21, wherein said infra-red image has a plurality of picture elements transmitted, each, via a distinct fiber of said bundle.

26. A system according to claim 21, wherein the auxiliary probe is provided with several infra-red windows enabling a surgeon to view images from various directions.

27. A system according to claim 23, wherein the probe is provided with a scanner assembly so as to facilitate a projection of discrete image signals onto a relatively limited number of optical fibers, thereby reducing a size of the bundle of optical fibers.

28. A system according to claim 21, wherein the probe is further provided with an automatic focussing mechanism.

29. A system according to claim 1, wherein said defective cell compensator incorporates art Extending Soble Filter technique.

30. A system according to claim 1, and furthermore comprising a defective cell compensator for assigning a compensated value to at least one picture element originating from a defective cell included in said infra-red range detector; the compensated value being determined on a basis of at least one picture element value originating from a non defective cell in the proximity of the defective cell.

31. A system according to claim 30, wherein said defective cell compensator incorporates a bi-linear transformation technique.

32. A system according to claim 1, wherein said infra-red optical assembly includes a lens of 500 mm focal length and made on either ZnS or Ge.

33. A system according to claim 1, wherein said infra-red detector means comprises a linear or bi-dimensional detector array of infra-red cells.

34. A system according to claim 33, wherein each individual detector cell is made of MCT alloy.

35. A system according to claim 1, and furthermore comprising a console member and a readily displaceable camera assembly member; said camera assembly member including at least said infra-red and visible range optical assemblies and infra-red range detector; and wherein said console member includes at least said image processor; and said first and second video imaging devices and a cooling unit, adapted to continuously maintain the infra-red range detector at an essentially fixed temperature, located in one or other of said member; the system further including a mechanical coupler for coupling said console member to said camera assembly member and an electrical and/or optical coupler for coupling together constituent components in said member.

36. A system according to claim 35, wherein the console and the camera assembly are fitted each with means for transportation and are mechanically coupled to each other in the form of a detachable coupling whereby the camera assembly is transportable independent of said console.

37. A system according to claim 35, wherein said cooling unit is a closed loop cooling unit located in said camera assembly.

38. A system according to claim 1, and furthermore comprising a video recorder adapted to receive and record said first and second sets of enhanced video frames.

39. An infra-red vascular angiography system comprising a readily displaceable infra-red camera comprising a camera housing and including an infra-red optical assembly of high sensitivity for receiving and transmitting with minimal distortion an infra-red image of an object within an angular range of substantially .+-.45.degree. with respect to a normal to the object; an infra-red range detector for detecting the infra-red image transmitted from said optical assembly, in an infra-red wavelength range substantially between 8 to 12 micrometers, and converting it into successive electric output signals; a video imaging device coupled to said infra-red range detector for digitizing said output signals and converting them into successive digitized video image flames or successive portions thereof; an image processor coupled to said imaging device for receiving the successive video frames or successive portions of video frames to process them and form enhanced video images and a display device coupled to said image processor;

the system further comprising an auxiliary portable probe for viewing and transmitting an infra-red image of a region of said object closely adjacent said probe wherein said probe comprises a housing; at least a further infra-red lens forming a window in said housing and adapted to be juxtaposed with respect to said region; an optical fiber assembly having a first end portion located within said housing remote from said window and having a second and opposite end portion juxtaposed with respect to said infra-red range detector; and an optical system located in said housing and adapted to project an infra-red image transmitted by said window onto said first end portion of said optical fiber assembly.

40. A system according to claim 39, wherein said auxiliary portable probe is in the form of an elongated, substantially cylindrical probe comprising a tubular housing having at its front end an infra-red window.

41. A system according to claim 39, wherein said auxiliary portable probe further comprises a lens system which serves for focussing of the image onto a bundle of optical fibers protruding from the housing.

42. A system according to claim 41, wherein the probe is provided with a scanner assembly for projecting discrete image signals onto a relatively limited number of optical fibers, thereby reducing a size of the bundle of optical fibers.

43. A system according to claim 41, wherein the opposite end portion of the bundle is secured to a coupling unit which is provided with means for readily and releasably coupling the bundle to an appropriate location in said camera housing.

44. A system according to claim 39, wherein said infra-red image has a plurality of picture elements transmitted, each, via a distinct fiber of said bundle.

45. A system according to claim 39, wherein the auxiliary probe is provided with several infra-red windows enabling a surgeon to view images from various directions.

46. A system according to claim 39, wherein the probe is further provided with an automatic focussing mechanism.

47. An infra-red vascular angiography system comprising a readily displaceable infra-red camera including an infra-red optical assembly of high sensitivity for receiving and transmitting with minimal distortion an infra-red image of an object within an angular range of substantially .+-.45.degree. with respect to a normal to the object; an infra-red range detector for detecting the infra-red image transmitted from said optical assembly, in an infra-red wavelength range substantially between 8 to 12 micrometers, and converting it into successive electric output signals; video imaging device coupled to said infra-red range detector for digitizing said output signals and converting them into successive digitized video image frames or successive portions thereof; an image processor coupled to said imaging device for receiving the successive video frames or successive portions of video frames to process them and form enhanced video images and a display device coupled to said image processor;

the infra-red optical assembly comprising an infra-red lens which is adapted to be spaced from the object in a range of substantially 0.30 m to 1.00 m and wherein there is furthermore provided an automatic focussing assembly for enhancing the infra-red image transmitted to said infra-red range detector.

48. An infra-red vascular angiography system comprising a readily displaceable infra-red camera including an infra-red optical assembly of high sensitivity for receiving and transmitting with minimal distortion an infra-red image of an object within an angular range of substantially .+-.45.degree. with respect to a normal to the object; an infra-red range detector for detecting the infra-red image transmitted from said optical assembly, in an infra-red wavelength range substantially between 8 to 12 micrometers, and converting it into successive electric output signals; a video imaging device coupled to said infra-red range detector for digitizing said output signals and converting them into successive digitized video image frames or successive portions thereof; art image processor coupled to said imaging device adapting to receive the successive video frames or successive portions of video frames to process them and form enhanced video images and a display device coupled to said image processor;

said image processor incorporating a defective cell compensator for assigning a compensated value to at least one picture element originating from a defective cell included in said infra-red range detector; said compensated value being determined on a basis of at least one picture element value originating from a non defective cell located in proximity to the defective cell.

49. A system according to claim 48, wherein said defective cell compensator means operates on the basis of the Extending Soble Filter technique.

50. A system according to claim 48, said defective cell compensator means incorporating the bi-linear transformation technique.

51. An infra-red vascular angiography system comprising a readily displaceable infra-red camera including an infra-red optical assembly of high sensitivity for receiving and transmitting with minimal distortion an infra-red image of an object within an angular range of substantially .+-.45.degree. with respect to a normal to the object; an infra-red range detector for detecting the infra-red image transmitted from said optical assembly, in an infra-red wavelength range substantially between 8 to 12 micrometers, and converting it into successive electric output signals; a video imaging device coupled to said infra-red range detector for digitizing said output signals and converting them into successive digitized video image frames or successive portions thereof; an image processor coupled to said imaging device for receiving the successive video frames or successive portions of video frames to process them and form enhanced video images and a display device coupled to said image processor;

and furthermore comprising a console member and a readily displaceable camera assembly member; said camera assembly member including at least said infra-red range assembly and infra-red range detector; and wherein said console member includes at least said image processor; and said video imaging device and a cooling unit, adapted to continuously maintain the infra-red range detector at an essentially fixed temperature, located in one of said members; the system further including a mechanical coupler for coupling said console member to said camera assembly member and an electrical and/or optical coupler for coupling together constituent components in said member.

52. A system according to claim 51 wherein said cooling unit is a closed loop cooling unit located in said camera assembly.

53. A system according to claim 52, wherein the console members and the camera assembly member are fitted each with means for transportation and are mechanically coupled to each other by a detachable coupling wherein the camera assembly member is transportable independent of said console member.

Description Submit all comments and votes

FIELD OF THE INVENTION

This invention relates to an infra-red vascular angiography system and in particular, but not exclusively, to an infra-red vascular angiography system for use in cardiovascular surgery.

BACKGROUND OF THE INVENTION

The use of vascular angiography systems, particularly in cardiovascular surgery, has long been known, particularly in connection with preoperative mapping of the cardiovascular system to be operated upon for the purpose of surgical grafting or the like, and also in connection with ascertaining, after grafting, the effectiveness of the grafting, both as regards the subsequent free flow of blood through the graft to the revascularized conduit and the absence of leakage, or kindred defects.

To this end, both ultrasonic and X-ray angiography have been employed but in both cases considerable disadvantages arise, such as for example the undesirable contact between the ultrasonic probe and the exposed blood vessels, the necessity to inject into the blood vessels a suitable toxic contrast medium, and the inherent risk associated with the use of X-ray radiation.

It is as a consequence of these and other disadvantages that there has been proposed to use a cardiovascular angiographic system which is based on the thermographic technique and which involves obtaining infra-red thermal images of the relevant cardiovascular region prior to, during and subsequent to surgery. The relevant information which can be derived from such infra-red imaging arises in view of the fact that a temperature difference is established between the fluid (either cardioplegia or blood) flowing in the relevant blood vessels and the surrounding region. Thus, for example, such temperature differences can arise as a result of the initiation of fluid flow through a graft or the perfusion of blood into the surrounding tissue.

Proposals for the use of such infra-red coronary angiography have appeared in the professional literature and in this connection attention is particularly directed to the paper by Friedrich W. Mohr et al in The Annals of Thoracic Surgery, 1989; 47:441-9, entitled "Thermal Coronary Angiography: A Method for Assessing Graft Patency and Coronary Anatomy in Coronary By-pass Surgery". A proposal for a system for carrying out such angiography and clearly derived from the Mohr paper is to be found in U.S. Pat. No. 4,995,398.

These proposals have not, however, led to a practical system and have all been characterized by serious limitations which, in use, renders it impossible or difficult to employ them for real time infra-red imaging.

It is therefore an object of the present invention to provide a new and improved infra-red vascular angiography system particularly for use in cardiovascular surgery, in which the above-referred-to disadvantages are substantially reduced or overcome.

BRIEF SUMMARY OF THE INVENTION

According to the present invention there is provided an infra-red vascular angiography system comprising a readily displaceable infra-red camera including an infra-red optical assembly of high sensitivity capable of receiving and transmitting with minimal distortion an infra-red image of an object within an angular range of substantially .+-.45.degree. with respect to a line perpendicular to the object; infra-red detector means for detecting the infra-red image transmitted from said optical assembly and converting it into successive electric output signals; video imaging means coupled to said detector means for digitizing said output signals and converting them into successive digitized video image frames or successive portions thereof; image processor coupled to said imaging means adapted to receive the successive video frames or portions thereof so as to process them so as to form enhanced video images and display means coupled to said image processor.

Preferably, the infra-red optical assembly comprises an infra-red lens which is adapted to be spaced from the object in a range of substantially 0.30 m to 100 m, there being furthermore provided an automatic focussing assembly for continuously maintaining in focus the infra-red image transmitted to the infra-red detector.

In accordance with a preferred embodiment of the present invention, there is furthermore provided an auxiliary portable probe for viewing and transmitting an infra-red image of a region of said object closely adjacent said probe and comprising, a housing: at least a further infra-red lens forming a window in said housing and adapted to be juxtaposed with respect to said region; a thermal fiber assembly, a first end of which is located within said housing remote from said window and a second and opposite end of which is juxtaposed with respect to said infra-red lens of said camera; and an optical system located in said housing and adapted to project an infra-red image transmitted by said window onto said first end portion of said thermal fiber assembly.

With such a system, it is possible to obtain effective real time imaging of the cardiovascular zone subject to surgery so as to have, on the one hand, an accurate presurgical mapping of the zone (thereby enabling the surgeon to determine the spot wherein anastomoses is required) and, on the other hand, to enable the surgeon to obtain in real time a clear picture of the effectiveness of the grafting which is being carried out.

Preferably, the console and the camera assembly are independently displaceable and are provided with mechanical coupling means for coupling the members together.

The camera assembly, which can be of compact construction, can be readily displaced into position during surgery whilst the console can be distanced from the operating site so as not to be in the way during surgery.

A serious problem exists for the surgeon to correlate the infra-red image observed on the member screen and relating to the region of the patient being imaged and the visible image of the same region as observed directly by the surgeon. This problem is compounded by the fact that infra-red image is intrinsically of a vague and unclear nature (even after it has been enhanced by exploiting image processing techniques) and the fact that the infra-red image necessarily includes components which, whilst emitting energy in the infra-red range, are not of interest and which, of course, cannot be seen in the corresponding visible image. It will therefore be readily appreciated that the surgeon is likely to encounter difficulties in accurately correlating the region currently being imaged with the thermal image thereof being viewed on the monitor.

It is therefore proposed to incorporate in the camera a video camera (e.g. CCD camera), thereby providing the surgeon and the assisting staff with a clear and wide video image of the precise area currently being imaged.

The incorporation of the video camera in the camera allows for two alternating display modes: a first visible display mode in which can be seen the visible image seen by the video camera (for a given field of view) and a second thermal display mode presenting a thermal image for the same field of view.

The two display modes can be alternately switched into view. When the visible display mode is operational, then the visible region being displayed can have delineated thereon, by means of suitable highlighted markings, e.g. dashed lines, the position of the corresponding thermal display zone.

Alternatively, both display modes can be simultaneously viewed, either on a split screen or with the second thermal display mode being confined to a desired limited zone within the field of view displayed by the first visible display mode.

There is thus provided in accordance with another aspect of the invention an infra-red vascular angiography system comprising a readily displaceable camera including infra-red and visible range optical assemblies and detector means; the infra-red optical assembly being of high sensitivity and being capable of receiving and transmitting with minimal distortion an infra-red image of an object within an angular range of substantially .+-.45.degree. with respect to a line perpendicular to the object; the infra-red detector means being capable of detecting the infra-red image transmitted from said optical assembly and converting it into a first set of successive electric output signals; first video imaging means coupled to said detector means for digitizing said first set of output signals and converting them into a first set of successive digitized video image frames or portions thereof; the visible range optical assembly being capable of receiving and transmitting a visible image in coordination with said infra-red optical assembly and having a field of view with respect to said object which covers at least that of said infra-red assembly; the visible range detector means being capable of converting the transmitted visible image into a second set of successive electric output signals; a second video imaging means coupled to said visible range detection means for digitizing said further set of successive electric output signals into a second set of successive digitized video image frames or successive portions thereof; an image processor coupled to said first and second imaging means adapted to receive said first and second successive video frames or portions thereof so as to process them so as to form first and second sets of enhanced video images; and switching means coupled to said image processor, the latter being adapted to route either or both of said sets of enhanced video images to a display means coupled to said image processor responsive to said switching means.

Preferably, the lines of sight (LOS) of the infra-red and visible range optical assemblies coincide, in which case, of course, the respective fields of view (FOV) have a common center.

With such a system, the displaceable camera can be provided with a displacing handle carrying switching means electrically associated with the image processor means and being actuatable for switching purposes upon sensing of a contact or lack of contact with the handle. Thus, for example, when the surgeon grips the handle and displaces the camera so as to direct it onto the region of interest, the contacting of the handle automatically switches the image processor so that the visible image appears on the display means. The surgeon is thus directly guided into correctly positioning the camera. Once this has been achieved, the release of contact with the handle automatically switches the image processor so that the thermal image appears on the display means. In this way it is ensured that the visible and thermal images are wholly coordinated. Where the optical assembly provides for coincided lines of sight, the displayed visible and infra-red images always maintain a mutually coordinated spatial relationship, regardless of the position of the camera head.

Preferably, the visible range detector means, said second video imaging means and at least a portion of said visible range optical assembly are included in a video camera.

The optical assemblies can have optical components in common and among these is included a beam splitter assembly adapted to receive radiation comprising infra-red and visible range constituents; the beam splitter being adapted to separate said received radiation into an infra-red constituent directed to the infra-red assembly, and a visible range constituent directed to the visible range assembly.

In accordance with a preferred embodiment, the system comprises separate camera and console assemblies, with only the essential optical assemblies and detector means being incorporated in the camera assembly whilst the remaining, relatively bulky, components of the system being accommodated in the console assembly. The assemblies are electrically coupled together. In this way, only the relatively compact camera assembly needs to be positioned in the operating region, whilst the remaining console assembly can be located in a region where it does not interfere with the movement of the operating personnel. Preferably, the camera assembly is provided with an independent closed loop cooling system.

Preferably, the infra-red detector means is adapted to detect infra-red images at infra-red wavelength range of the order of 8 to 12 micrometers.

In accordance with a further embodiment of the invention, the image processor means includes defective cell compensator means arranged to assign compensated value to a picture element originating from a defective cell forming part of the infra-red detector means; the assigned compensated value being determined on the basis of at least one picture element value originating from a fault free cell in the proximity of the defective cell.

BRIEF SUMMARY OF THE DRAWINGS

For a better understanding of the present invention and to show how the same may be carried out in practice, reference will now be made to the accompanying drawings in which:

FIG. 1 is a perspective view of a first embodiment of an infra-red vascular angiography system in accordance with the present invention;

FIG. 2 is a view of the camera head shown in FIG. 1, on an enlarged scale;

FIG. 3 is a perspective view of a second embodiment of an infra-red vascular angiography system in accordance with the present invention;

FIG. 4a is a side elevation of the system shown in FIG. 3.

FIG. 4b is a side elevation of a base portion of a camera head assembly forming part of the system shown in FIG. 4a when detached from the remainder of the system;

FIG. 5 is a schematic block diagram of a camera head forming part of the embodiment shown in FIG. 3;

FIG. 6 is a schematic side elevation of a console cabinet forming part of the embodiment shown in FIG. 3, with the constituent components thereof shown in block form.

FIG. 7 is a schematic block diagram of the camera head and electronic module components utilized in the system according to the first embodiment of the invention;

FIG. 8 is a view on an enlarged scale of a beam splitter assembly incorporated in the camera head as shown in FIG. 5;

FIG. 9 is a longitudinally-sectioned view of a first form of auxiliary portable probe for use with the system in accordance with the invention;

FIG. 10 is a cross-sectional view of a coupling unit for coupling to a camera bead the probe shown in FIG. 9;

FIG. 11 is a longitudinally-cross-sectioned view of a second form of auxiliary portable probe for use with the system in accordance with the invention;

FIG. 12 is an illustration of the system in operation during cardiovascular surgery; and

FIG. 13 is a schematic block diagram of image processor components and VCR and monitor devices associated therewith, forming part of the system shown in FIG. 3.

DETAILED DESCRIPTION OF SPECIFIC EMBODIMENTS

As seen in FIG. 1 of the drawings, the infra-red imaging system according to a first embodiment of the invention (referred to herein as "first embodiment of the system") comprises a thermal camera head 1 which is mounted on one end of a support arm 2 which is pivotally coupled at an opposite end thereof to a support post 3 which, in its turn, is telescopically supported within a guide sleeve 4. The guide sleeve 4 is mounted on a console cabinet 5 which is supported by legs 6 fitted with castors 7. As can be seen, the head 1 is coupled to the arm 2 so as to be pivotally rotatable with respect there to, whilst the arm 2 is, in its turn, composed of arm components 2a and 2b which are pivotally coupled together. Bearing this in mind and bearing in mind the pivotal coupling of the arm component 2a to the post 3, and the fact that the post 3 is telescopically displaceable with respect to the sleeve 4, it will be readily seen that the position of the head 1 can be readily adjusted in any required direction whilst the system, as a whole, can be readily displaced into and out of an operational position. Furthermore, it will be noted that the head is supported with respect to the console 5 in a counterbalanced position so that once the head has been placed in any required operational position, it will remain stable in that position until it is displaced into another position.

The console cabinet 5 contains, on the one hand, an electronic control module 8 for the camera head 1 and, on the other hand, high pressurized nitrogen gas containers 9, the control module 8 and the containers being coupled to the camera head 1 via appropriate coupling conduits 10.

The camera head 1 is provided with a manual adjusting handle 11 which also supports a control keypad by means of which the operation of the system can be controlled.

A monitor 12 is mounted on a suitable positioning bracket 13 which is itself mounted in a swingable manner on the support post 3. This monitor is designed to be observed by the operating surgeon and his assistant. An additional monitor 14 is supported by the console cabinet 5 and is directed to observers other than the direct operating staff. A video tape recorder 15 is supported by the console cabinet 5 for preparing a hard copy and record of the observed infra-red image.

As seen in FIG. 1, the camera head 1 has formed in its lower surface a central port 16 through which infra-red radiation can pass to an infra-red camera lens, a first auxiliary port 17 through which a marker beam can be projected for purposes to be explained below, and a second auxiliary port 18 designed to communicate with a microphone.

The basic construction of the remote camera head 1 will now be described with reference to FIG. 2 of the drawings. As seen in this figure, the remote camera head I comprises an outer casing 21, essential camera components 22 and an optical marker assembly 23. The easing also includes a microphone 24 for use in picking up for recording, etc. the surgeon's instructions, comments or the like. The optical marker assembly 23 is coupled by means of an optical fiber bundle 25 to a light source (not shown), whilst the camera components 22 are electrically coupled via an electric cable 26 with the electronic camera control. module 8 located in the console cabinet 5.

Whilst in the first embodiment described with reference to FIGS. 1 and 2 of the drawings the described arid illustrated system involves a camera head assembly mounted on a console so as essentially to form an integral part thereof, in the embodiment shown in FIGS. 3, 4a, and 4b of the drawings the system comprises two sep