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Dr. Christopher Beverley Williams MA BM FRCPADDRESS: 11 Frognal Way, |
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EDUCATION QUALIFICATIONS: MEMBERSHIP OF MEDICAL SOCIETIES Worshipful Society of Apothecaries (Liveryman) 1958 PRESENT APPOINTMENTS CONSULTANT PHYSICIAN with a special interest in Gastrointestinal
Endoscopy:- HONORARY CONSULTANT PHYSICIAN EDITORIAL BOARDS Endoscopy SUMMARY Dr. Christopher Williams BM FRCP is Consultant Physician specialising in gastrointestinal endoscopy at St. Mark's Hospital for Intestinal and Colorectal Disorders, Harrow, London, where he has set up the Wolfson Unit for Endoscopy an academic Endoscopy facility, specialising in development of new approaches to teaching flexible endoscopy and improving colorectal cancer prevention. He also has attachments to The Hospitals for Sick Children and others. Since 1970 he has become experienced in most forms of GI endoscopy but particularly in colonoscopy and colonoscopic polypectomy (around 30,000 procedures), a field in which he has taught, published and lectured widely including the Quadrennial Review Lecture in "Polypectomy" at the 1990 World Congress of Gastroenterology. He has written numerous articles on colonoscopy, colonic neoplasia and related topics and is co-author or editor of five books relating to the colon and endoscopy. He has been a committee member and Endoscopy Vice-President of the British Society of Gastroenterology. Special interests include teaching and television teaching of colonoscopy, application of computers to endoscopy including teaching simulators and other innovatory high technology approaches. He has academic involvement in various studies relating to colonoscopic practice and colorectal cancer prevention. He is married to a Physician and has two children. Other interests include travel, skiing, scuba, good wine and food.
INTERNATIONAL ENDOSCOPY DEMONSTRATIONS & MASTERCLASSES Turin, Italy 1973 FILMS, VIDEOTAPES AND TEACHING MATERIALS 1973 "Colonoscopy - Principles and Technique" BOOKS: "COLORECTAL DISEASE - AN INTRODUCTION FOR PHYSICIANS AND SURGEONS".Editors: Thompson, J.P.S., Nicholls, R.J. and Williams, C.B. London; William Heinemann (1981) "PRACTICAL GASTROINTESTINAL ENDOSCOPY" Oxford, Blackwell
Scientific Publications "ANNUAL OF GASTROINTESTINAL ENDOSCOPY" INTERNATIONAL GUEST LECTURES: Over 250 guest lectures given in 50 countries around the world since 1970, PUBLICATIONS (relating to colonoscopy): 140 papers & book chapters. March 1998 (shortcv2.doc) |
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Lennart Wehlin-föreläsning
NEW APPROACHES TO COLONOSCOPY - DYNAMIC ANATOMY, MAGNETIC IMAGING AND COMPUTER SIMULATIONChristopher B WilliamsSt Mark’s Hospital for Colorectal Disorders, London, UK Dynamic anatomy During colonoscopy anatomical variations in length and fixation of the bowel result in amazingly variable (and at times painful) looping of the endoscope. These variations of the anatomy and fixations of the colon are determined at the foetal stage in utero when, at about 3 months after conception, the colon returns into the abdominal cavity from the umbilical hernia. At this stage it should, conventionally, become substantially fixed retroperitoneally, especially the descending colon, splenic flexure and ascending colon. Colonic anatomy and length have been studied by us during laparotomy in 229 Caucasian and Oriental patients, showing a range of colonic length between 70-160 cms (median 114 cms, with no differences between the Eastern and Western group) [1]. In Western colons however, the descending colon was significantly mobile in 8%, the splenic flexure in 20% and the transverse colon in 30%, Oriental colons were significantly less mobile. Barium enema measurements in 345 patients showed the female colon to be on average longer (125 cms vs. 120 cms), particularly in the transverse colon, which more frequently looped down to the pelvic brim [2]. A study of the barium enema films of patients found difficult to endoscope by an experienced endoscopist (CBW) showed positive correlation with a long and looping transverse colon as well as with sigmoid colon adhesions, explaining the significantly greater number of females (23%) than males (11%) who proved difficult to colonoscope [2]. Much of the skill of colonoscopy lies in controlling the looping configurations produced, dependent on the mobility and fixations of the colon, by the forces exerted during colonoscope insertion. These loops including the typical spiral or ‘N’ loop in the sigmoid colon, alpha loop, reversed splenic flexure loop and multiple looping in approximately equal numbers, as well as the more rare ‘gamma’ loop of the transverse colon. Examples of these loops, and the manoeuvres needed for their elimination, will be given in simple animated graphics format. Even skilled endoscopists know that they are disorientated for much of the time during a colonoscopy, unless the fixed anatomy of the ileal-caecal valve can be reached and correctly identified. It is possible, without due care, to mis-identify the mid-transverse colon or hepatic flexure as being caecum. Other clues as to location can be equally misleading, since the descending colon can show the triangular configuration usually associated with the transverse colon, blue extra-colonic coloration typical of the hepatic flexure can be seen in the splenic flexure or sigmoid, and estimation by distance of endoscope inserted is even more misleading. The result is that endoscopists learn their technique empirically by a combination of inexact judgements based on the responsiveness and feel of the instrument, with further feed-back based on the protests of the patient when looping occurs. Even when tip localisation has been correctly judged it can be very difficult to manage straightening of any loops that have formed, so that inappropriate manoeuvres and unnecessary pain may be caused. Worse still, incorrect preoperative information may be given to the surgeon about tumour localisation [3]. All these factors make colonoscopy often difficult to perform and even more difficult to teach to someone else. In spite of all these problems there has been a tendency to decry the use of x-ray imaging for colonoscopy [4], partly because of the expense and potential hazard of the technique, but mainly because few endoscopists have it available. Those endoscopists that do have fluoroscopy in their endoscopy facility however know the confidence in localisation and the added logic to loop-handling that it gives in difficult examinations, and its great value in teaching [5,6]. Even when it is available though, fluoroscopy has severe limitations as a technique. The small field size covers only a small part of the abdomen and the limited ‘window’ of view can give misleading assessment of complex loops, especially when the patient is in the conventional lateral position. The 2-dimensional radiological image also gives no clue as to the 3-dimensional configuration of shaft loops, and therefore no information as to which rotational manoeuvre may be helpful in straightening them. Because of the radiation hazard it is also not possible to use the fluoroscopic image to check for the effectiveness of assistant hand pressure when seeking to control loops.
3-D electronic imaging Because of these recurrent and unpredictable difficulties in performing colonoscopy, and regular problems in teaching it to others, two British groups produced a non-X-ray real-time method of endoscope imaging. Both groups considered different technical possibilities but independently arrived at the same conclusion, that induced electromagnetic field position-sensing is the preferred option. After preliminary laboratory experimentation both groups performed limited clinical trials in late 1992, with simultaneous publication shortly thereafter [7,8] and on-going co-operative prototype evaluation in clinical practice since then [9]. Commercial prototypes are about to be trialled by the Olympus Optical Corporation, and there is hope that the system will become generally available, at modest cost. The principle of electronic imaging is that a magnetic field induces a small electric current in a coil of wire exposed to it, the character of the induced current giving precise information as to the position of the coil in relation to the (electro-magnetic) source. In our systems three large ‘generator’ coils are placed below or adjacent to the patient and sequentially produce pulses of low strength (about 1x10-6 that of the energy of a MRI scan) electro-magnetic fields. Within the endoscope instrument channel is placed a catheter containing 15 sensor coils each 2 mm wide and at 12 cm intervals. Every 0.2 seconds the data from each of the 15 sensor coils, responding to the sequential electro-magnetic pulses from the 3 generator coils, are computed to give the exact position and orientation of each sensor. A smooth curve is fitted through these calculated position points by a computer graphics program incorporating the mechanical characteristics of the instrument tip and shaft. The 3-dimensional position information is rendered on the monitor screen using differential grey-scale shading, with those parts of the shaft closest to the generator coils rendered dark and distant parts light. Since the electronic imaging system gives no direct information about anatomic position or body characteristics it is necessary to register fixed anatomic points before starting, typically the right and left costal margins and anal region. This is easily done with an external sensor coil, which can be left attached to the patient to indicate changes of position. A similar external sensor coil can additionally be used to show the position of the assistant’s hand in relation to any loop that may have formed, or can be placed on the umbilicus of a protuberant abdomen to give additional information[10]. The screen information can be presented in A-P view, lateral view or a combination of both side by side. The image can equally be rotated continuously in any plane, giving a dramatic impression of the profoundly 3-D anatomy of some colons. The imaging records of about six colonoscopies can be stored on a single floppy disc or selected images can be output individually for teaching or documentation purposes. A facility is available for precise measurement of any sensor point , the system being accurate to within 1 mm in bench-top testing and 3 mm in clinical practice. Useful academic data can be acquired about the mobility of the colonoscope and, by implication, the colonic attachments within the abdominal cavity. The feasibility of showing on-screen the colonoscope configuration rotating in any direction gives a spectacular view of the 3-D looping of the instrument within the abdominal cavity, as well as the rapid and equally dramatic anatomic alterations that can be caused by withdrawal and rotational manoeuvres. In preliminary clinical assessment [10] using the electronic imager in 100 patients, an experienced endoscopist was randomly assigned to view or not to view the imager during procedures. The conclusion was that using the imager reduced the amount of looping and the number of straightening manoeuvres required, but did not significantly increase the speed of colonoscopy overall. It demonstrated that in over 40% of cases the endoscopist’s assessment of loop formation was inaccurate and that for 13% of the time assessment of tip location was also incorrect. In more extended evaluation by a range of different endoscopists the efficacy of the system in making rational use of assistant hand pressure is apparent. In some cases where looping has occurred it is obvious from the lateral projection view that all loops are retained within the posterior aspect of the abdomen, and therefore inaccessible to assistant hand pressure. When looping occurs in the anterior (3-D) plane, use of the mobile hand-held sensor coil allows very precise application of the assistant’s hand, and reduces the time that hand pressure is used. No systematic assessment of the effects on beginner or inexpert endoscopists has yet been undertaken, but it is likely that, after suitable initial explanation, availability of the electronic imaging system will accelerate the learning process and prevent some of the pitfalls or gross inaccuracies to which less expert endoscopists are especially prone.
Teaching colonoscopy - ‘virtual reality’ and computer simulation Since 1971 I have tried a variety of simple teaching models and devices, intended to allow practice of colonoscopy and the development of co-ordinated handskills, but without involving either patients or needing continuous expert supervision. A simple computer game approach proved enjoyable and was the basis for first attempts at formal computer simulation. The Mk 1 & 2 simulations were severely limited by the slow computational speeds then available on PCs, for no hospital can afford the supercomputer approach used for commercial aviation simulators. Our current prototype Mk 3 teaching simulator incorporates mathematical modelling of the flexible characteristics of the colonoscope with the elasticity and mesenteric fixations of the colon. It also has relatively advanced and realistic graphics and will have ‘feel’ given by computer-controlled force feedback motors responding to all the movements of the colonoscope shaft (in-out and rotational) as well as to movements of the angulation controls and accessories. Lip service has been paid for some years to the general concept of simulator teaching [11-15] but nothing significant has materialised till now. In part this has been due to complacency in the ‘most favoured’ endoscopic nations, as well as prejudice against anything which might threaten the private practice supremacy of the relatively few existing ‘experts’. Their level of ‘expertise’ is however open to question, since so many existing colonoscopists are essentially self-taught, and there has been no standardised or objective way of testing their skills. Furthermore there is quite extraordinary deprivation in most of the world in provision of endoscopy services. Whilst Japan has over 20 endoscopists per 100 thousand (105) population, the USA around 5 per 105 and continental Europe 3 per 105 , in stark comparison Columbia and India have only about 1.5 endoscopists per million (106), the Sudan 1 endoscopist per million and parts of Indonesia reportedly less than 1 endoscopist per 3 million population. Computer simulation holds the key to changing this inequity and also to upgrading the standards of existing endoscopists - rather than leaving them in isolation to pass on their bad habits to others. Simulation teaching will need to be carefully organised and backed by a programme of conventional hands-on teaching and exposure to the wealth of existing teaching materials. However the ‘virtual reality’ environment that simulation should provide will allow trainees (or experts) to be exposed repetitively to hundreds of different colonoscopic situations, and to develop the ‘tricks of the trade’ very quickly - perhaps in as little as a week or two of intensive training. We hope to trial the new prototype simulators in the UK during 1998, and then to start to establish a network of adequately equipped, staffed and funded regional endoscopy teaching centres.
Bibliography 1. SAUNDERS BP, MASAKI T, SAWADA T, HALLIGAN S, PHILLIPS RKS, MUTO T, WILLIAMS CB: A peroperative comparison of Western and Oriental colonic antomy and mesenteric attachments. Int J Colorectal Dis 1995, 10:216-221. 2. SAUNDERS BP, HALLIGAN S, JOBLING C, FUKUMOTO M, MOUSSA ME, WILLIAMS CB, BARTRAM CI: Can barium enema indicate when colonoscopy will be difficult? Clin Radiol 1995, 50:318-321. 3. HANCOCK JH, TALBOT RW: Accuracy of colonoscopy in the localisation of colorectal cancer. Int J Colorect Dis 1995, 10:140-141. 4. WAYE JD: Colonoscopy without fluoroscopy. Gastrointest Endosc 1990, 36:72-73. 5. ROGERS BHG: Colonoscopy with fluoroscopy. Gastrointest Endosc 1990, 36:71-72. 6. COTTON PB, WILLIAMS CB: Practical Gastrointestinal Endoscopy. Fourth Edition. Oxford: Blackwell Scientific 1996 7. BLADEN JS, ANDERSON AP, BELL GD, HEATLEY DJ: Non-radiological technique for three-dimensional imaging of endoscopes. Lancet 1993, 341:719-722. 8. WILLIAMS CB, GUY C, GILLIES DF, SAUNDERS BP: Electronic three-dimensional imaging of intestinal endoscopy. Lancet 1993, 341:724-725. 9. SAUNDERS BP, PHILLIPS RKS, WILLIAMS CB: Intraoperative measurement of colonic anatomy and attachments with relevance to colonoscopy. Br J Surg 1995, 82:1491-1493. 10. SAUNDERS BP, BELL GD, WILLIAMS CB, BLADEN JS, ANDERSON AP: First clinical results with a real-time electronic imager as an aid to colonoscopy. Gut 1995, 36:913-917. 11. BAILLIE J, JOWELL P, EVANGELOU H, BICKEL W, COTTON PB: Use of Computer Graphics Simulation for Teaching of Flexible Sigmoidoscopy. Endoscopy 1991, 23:126-129. 12. GILLIES DF, HARITSIS A, WILLIAMS CB: Computer simulation for teaching endoscopic procedures. Endoscopy 1992, 24 Suppl 2:544-548. 13. BRANDT LJ: Training in Gastrointestinal Endoscopy. Gastrointest Endosc 1992, 38:88-89. 14. REY J-F, ROMANCZK T: The development of experimental models in the teaching of endoscopy: an overview. Endoscopy 1995, 27:101-105. 15. NOAR MD: The next generation of endoscopy simulation: Minimally invasive surgical skills simulation. Endoscopy 1995, 27:81-85. |
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