Surgery – Endoscope – With camera or solid state imager
Reexamination Certificate
1999-05-05
2003-04-15
Mulcahy, John M. (Department: 3739)
Surgery
Endoscope
With camera or solid state imager
C348S051000, C600S166000
Reexamination Certificate
active
06547720
ABSTRACT:
This invention is concerned with the field of three-dimensional imaging and in particular with the provision of a natural three-dimensional image of an operative site via, inter alia, an endoscope, thereby improving the eye-hand co-ordination of a surgeon, whilst he/she carries out such a surgical procedure.
BACKGROUND
The field of Minimally Invasive Endoscopic Surgery (MIES) has, for a period in excess of 10 years, been dependent on the use of small diameter viewing devices, collectively known as endoscopes. Some of these are flexible and a majority rigid in construction. A typical working length of the insertion portion of such an instrument would be in excess of 30 cm. The diameter of this part of the instrument will typically vary from 10 mm to as low as 1 mm or less. Small diameter optics or a coherent fibre-optic bundle transfers an image of the operative site, via the distal tip of the insertion portion located inside the patient, to an external CCD camera. The image acquired in this way is displayed on a conventional television monitor placed at a comfortable viewing distance from the surgeon.
We are used to viewing live imagery on a television screen from a distance of between 6 to 12 feet. Such a screen is of considerable size and typically provides a convenient viewing window, at such a distance. Conventional television quality is sufficient to provide the definition required within this window for such passive viewing.
It has been accepted for some considerable time that a conventional two-dimensional (flat) image is a poor substitute for the natural binocular vision enjoyed by a surgeon, when carrying out an open surgical procedure. Nevertheless, the benefits to the patient, in terms of reduced trauma and scarring, and the reduced cost to the hospital, in terms of the patient's stay, have fuelled considerable growth in the MIES market, with one type of relatively simple procedure, the laparoscopic cholesystectomy, being carried out routinely, today, in this manner. Unfortunately, the handicap imposed on the surgeon's dexterity (eye-hand co-ordination) by the impaired vision provided through a conventional video image has been a brake on the migration of this technique to a variety of more complex procedures. Accordingly, the need to provide a better solution and, in particular, a three-dimensional image of the operative site has been an accepted goal, for a number of years. However, a variety of commercial attempts to address the problem, have met with poor acceptance by the surgical profession, and it has been the recognition of this reality that has provided the incentive to analyse why such first generation three-dimensional visualisation systems failed. As a result of this analysis, a second generation three-dimensional endoscopic visualisation system has been developed and this is the subject of the current invention.
In order that the scale of the problem and, thus, the significance of the improvement provided by the current invention may be fully appreciated, a summary of the analysis of the shortcomings of a typical first generation three-dimensional endoscopic system is provided here.
A typical configuration of a first generation 3D endoscopic visualisation system might include.
A TV monitor with a picture diagonal of between 14″ and 20″
b) An endoscope which provides two points of view, effectively spaced a fraction of a millimetre apart at the distal tip. This may be described as a stereo-endoscope, although conventional systems have been used to achieve this to a small degree.
c) Special glasses which, when worn by the user, allow sequential viewing, respectively by left and right eye, of the two alternative perspective views of the scene, displayed sequentially on the monitor.
In use, the preferred working distance of the distal tip would be between 30 and 90 mm from the subject matter of interest, and the preferred viewing distance of the monitor would be at a conventional 2 to 3 metres from the observer. A substantial 3D effect would be observed, but, after some time, the observer would begin to feel uncomfortable and, in some cases, would suffer severe nausea. Eyestrain and headaches would be commonplace. In addition, the improvement in eye-hand co-ordination was not always as great as was expected.
In order to analyse the reasons for the effects described, it is useful to compare the nature of the binocular imagery provided to the observer by such a first generation system with that which would be experienced in a direct vision situation, and, in particular, when such a situation involves the manipulation of surgical instruments.
Historically there have been a number of factors which have created problems. These included:
1) The image acquisition geometry of the stereo-endoscope failed to adequately match the observer's viewing geometry;
2) The left and right eye images were displayed field sequentially, and not simultaneously as would be the case for natural vision;
3) The stereo-monitor displayed an image intended to aid eye-hand co-ordination, but this was not presented at a viewing distance, typically arm's length, where we would normally expect to find an object which we are manipulating;
4) The brightness of the image displayed was compromised, as a result of the field sequential display process.
It is a tenet of the current invention that the optimal solution for providing a more natural three-dimensional image, suitable for effective eye-hand co-ordination, will include the avoidance or substantial reduction of all of the above issues.
On an individual basis, some of the above problems are addressed within the prior art. For instance, in U.S. Pat. No. 5,712,732 (Street) apparatus is described in which two two-dimensional perspective images, provided by conventional liquid crystal display (LCD) panels, are combined with the aid of a semi-transparent mirror, so that each eye of the observer sees a different perspective, but in the same location. This causes the brain to fuse these perspectives into one three-dimensional image. Observer tracking ensures that each eye only sees the image intended for it. The principal purpose of the aforementioned invention is to avoid the need for the observer to wear special spectacles. Furthermore, it is normal for direct view LCD's to be provided with a polarising layer on the side viewed by the observer. The direction of polarisation of this sheet of material is normally set at 45° to the vertical. The use of a polarising element in front of each of two displays positioned mirror-symmetrically, either side of a semi-transparent mirror, is well known from the prior art. One such reference may be found on pages 365-366 of “Three-Dimensional Imaging Techniques” by Okoshi and published in 1976 by Academic Press Inc. By using suitably polarised spectacles, the viewer may therefore observe a stereoscopic or three-dimensional image. In both of these examples the observer is provided with left and right eye images, simultaneously. In International Patent Application PCT/GB97/00766 (Street) the problem of barrel distortion, encountered when using wide angle optics, is identified as causing undesirable (for instance vertical) disparity errors in a twin axis stereo-endoscope. The inventive step of PCT/GB97/00766 is to compensate for this problem by matching the distortions of both optical channels so that this effect is minimised.
SUMMARY OF THE INVENTION
It is an object of the current invention to provide a vision system which enables an observer to relate to an object field through a three-dimensional image scaled in proportion to said object field, so as to provide an environment for comfortable eye-hand co-ordination. More specifically, the invention is intended to provide a generalised method for improving eye-hand co-ordination, during videoscopic surgery.
It is a further object of the invention to provide the three-dimensional image substantially free from binocular disparity between corresponding points which would not be observed were the object field to be viewed direc
Birch & Stewart Kolasch & Birch, LLP
Mulcahy John M.
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