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Acknowledgements: The authors express their gratitude to Samuel R Rod, PhD (Bristlecone Corporation), for his time and the use of the equipment described in this project, and to Mr Frank Allen for his assistance in preparing and running the experimental phase of this project.
Support: Salary support for the research fellow on this project was provided in part by the Dutch Surgical Society (CCN), the Foundation "De Drie Lichten" and "Michael van Vloten", both located in The Netherlands. Additional funding was provided by a grant from the Jewish Hospital Foundation, Louisville, KY, USA. The remainder of this study was funded by the Division of Plastic and Reconstructive Surgery, University of Louisville.
Keywords: Three-Dimensional Imaging; 3D; Medical Imaging; Microsurgery; TOMS; Video; Telesurgery.
A Three-dimensional On-screen Microsurgical System (TOMS) was used and contrasted with conventional operative microvascular surgery in the laboratory setting. The surgeon's comfort, his ability to instruct microsurgical technique, pertinent technological performance, and the procedure itself were evaluated using a standardized questionnaire.
Based on data collected in this study, we conclude that divorcing the surgeon's eyes from the microscope eyepieces using the TOMS may make prolonged microvascular procedures less physically demanding and may increase the comfort level of both the surgeon and his assistant although refinements to the technology are required.
Technological advances have provided higher magnifications, well lit operating fields, and remote zoom and focus capabilities, which have greatly improved the ease with which the microsurgeon does his work. In spite of these advances, microsurgery continues to be physically demanding largely due to the fact that the surgeon must perform precise and minute manipulations while his eyes are fixed to the eyepieces of the operating microscope. This necessary marriage between surgeon and microscope has several disadvantages:
The purpose of this study was to investigate the feasibility of introducing an alternative to the conventional microscope used in microsurgery to address the disadvantages listed above. Instead of the surgeon and his assistant viewing surgery through the microscope eyepieces, a microscope system in which the eyepieces were replaced with cameras was introduced and tested. The system consisted of a video-microscope, which projected a magnified stereoscopic 3D image onto one or more video monitors. This setup is called Three-dimensional On-screen Microsurgery System (TOMS). In the present study we applied and evaluated TOMS in a standardized microsurgical procedure in a teaching laboratory environment.
The specific aims of this study were:
The equipment used for TOMS consisted of the following items:
The two cameras were connected to the camera controller which served as the interface to the image processor. The processor then sequentially output the right and left eyepiece camera images alternating at 120 cycles per second. This alternating signal was output to both the monitor and the emitter which synchronized the right and left output with the opening and closing of the right and left lenses of the shutter glasses. Thus, the right lens (right eye) was open to see only the output from the right eyepiece, and the left lens (left eye) only saw the output from the left eyepiece. This reproduced the stereoscopy viewed through a conventional binocular microscope.
Study Design
Twelve surgeons and residents trained in microsurgical procedures performed end-to-end anastomoses on rat femoral arteries in our microsurgery teaching laboratory. Male Sprague-Dawley rats weighing 250-300 grams were anaesthetized with intraperitoneal pentobarbital (50 mg/kg) and both femoral arteries (diameter 1 - 1.3 mm) were dissected free through standard groin incisions in preparation for end-to-end anastomoses. Each vessel was divided perpendicular to its long axis and reanastomosed using standard microsurgical techniques (2). In all animals, one side was operated with the conventional operating microscope, after which the contralateral side was operated using TOMS (figure 2).
Evaluation I - Acceptability
To evaluate the technical proficiency achieved using each technique, patency assessment of both sides was made using standard evaluations (2). Time to anastomotic completion was monitored but this data was discarded because of frequent interruptions required in early procedures for technological adjustments. A new medical technology questionnaire was used to collect qualitative acceptability data. The questionnaire consisted of 30 questions, addressing six different categories: (1) ease of operation; (2) surgeon comfort; (3) educational issues; (4) technological aspects; (5) overall impression of the surgeon; and (6) surgeon demographics (table 1).
The responses to the questionnaire resulted in a qualitative assessment of the surgeons' impressions of this concept and technique. All of the questions, except for the demographics, were scored as follows:
In interpreting the responses, the lower the score the higher the acceptance of TOMS as a new medical technology. Correspondingly, a 'neutral' score of two for all questions indicated no perceived advantages of the TOMS versus conventional microsurgery. Finally, higher scores were interpreted as perceived disadvantages to the TOMS.
Evaluation II - Feasibility
The feasibility of the TOMS system was assessed using a previously developed tool, the Feasibility Evaluation Assessment Tool (FEAT - table 3). This tool was selected because it provides an objective measurement of the application's pragmatism with specific reference to patient benefit. FEAT consists of three steps that clinicians should use when considering the implementation of a new medical technology. Step 1 identifies the medical task and the current status of this task; Step 2 assesses the clinical impact that the application will provide the patient with respect to quality of life and survival; and Step 3 provides a numerical rating of the application, scoring safety and clinical efficiency as a means of measuring the quality of the new technology.
In the comments section of the acceptability survey, there were both positive and negative statements. The technological category contained the only negative criticisms. These included all surgeons finding that the resolution of the monitor was inadequate, the illumination was poor, and the depth and width of the operative field were reduced. Positive comments from the other categories included notes about improved comfort during the operation, less fatigue, enhanced educational potential, and the possibility of the operating room personnel viewing and thus showing more interest in the procedure.
FEASIBILITY
The TOMS system was assessed using the FEAT algorithm. Step 1 identified that this application facilitates a method for performing microsurgery, and that this procedure is typically performed by using a microscope or occasionally loupes. Step 2 yielded the conclusion that in the clinical setting TOMS would not in any way decrease a patient's quality of life, and that it would not be detrimental to a patient's survival providing that the technique was used in the successful performance of the procedure. Since neither of the answers to the questions in Step 2 were negative, the assessment continued to Step 3. This final step assessed the safety and clinical efficiency qualities of TOMS. A neutral score was awarded for clinical efficiency because the equipment was considered to be as safe as the conventional microsurgery method. The accuracy of this system was rated -5 because the system was not quite as good as that witnessed through the microscope eyepieces. The rational for this rating is that there were some minimal reflections and resolution difficulties. The speed by which this procedure could be performed was rated +5 because there was improved comfort which resulted in slightly faster anastomoses (when uninterrupted by required technology adjustments). The ease of use of this system was rated a +15 because it was considerably more comfortable to perform the procedure than it is to perform conventional microsurgery using a microscope. This is because those tested found it far more comfortable to look at the monitor in a horizontal manner than having to look down the microscope eyepieces. The cost of using TOMS was rated -2 because the 3D microsurgery equipment added approximately 20% to the cost of conventional methods.
The long hours of intensive work looking through an operating microscope have always been accepted as the price paid for working in this surgical subspecialty. Looking through microscope eyepieces, while performing a complex microsurgical reconstruction for hours sitting or standing relatively motionless often in uncomfortable positions, is not uncommon. It is not unreasonable to see how years of performing surgery under these strenuous, physically demanding conditions could lead microsurgeons to prematurely retire from active practice, and in doing so, deprive the field of what could be their most fruitful years.
Recently, Serletti et al. compared the operating microscope and loupes for free microvascular tissue transfer. They studied the use of loupes in situations where awkward viewing angles were difficult to achieve comfortably with an operating microscope. Using loupe magnification, the position of the surgeon and his overall comfort were improved. This offered the advantage of improving operating field access and visualization (3). In another recent report, Shenaq et al. described loupe magnification as an alternative to the operating microscope in free-tissue transfer. Its use was advocated on the grounds of cost-effectiveness, portability, efficiency, and operator freedom (1).
The use of loupe magnification echoes the major benefit that TOMS was shown to have in this study: providing more freedom from the microscope and thus more comfort for the surgeon. In spite of the increased comfort achieved when using loupes, a major drawback is their limited magnification. This is particularly true when the vessels to be repaired are smaller than 1.5 mm. Furthermore, loupes do not meet the needs of multiperson surgical training and education.
The use of video technology in many surgical specialties is now considered routine. Preoperatively, video imaging may provide the surgeon with help in diagnosis and surgical planning (e.g., three-dimensional tomographic imaging). Intraoperatively, video permits operations such as endoscopic and laparoscopic surgery typically using 2D imaging (4-9). Development of stereoscopic three-dimensional display technologies capable of providing a clear and accurate sense of depth perception has been a critical requirement for the rapidly evolving field of minimally invasive surgery (7,10).
As an alternative to the operating microscope, advances in video technology can now permit the surgeon to view a (micro)surgical field on a video monitor in three dimensions without the necessity of physically looking through the microscope eyepieces. The conventional microscope magnifies the operative field and brings it mechanically and stereoscopically into the surgeon's view. TOMS also magnifies the operative field, but instead of having to look through eyepieces the surgeon views it in three-dimensions on a monitor. The fact that it is not necessary for the surgeon to be physically attached to the equipment (through the microscope eyepieces) accounts for the positive impression TOMS received in our study.
In conclusion, in the present study, we evaluated the use of Three-dimensional On-Screen Microsurgery and found that this technique provides several advantages over conventional microsurgical technique. This may directly impact the quality of care delivered to patients based on technical assistance, ease of operation, surgeon's fatigue, and continuation of practice by senior surgeons with a wealth of experience.
However, our evaluation of the technology of the equipment showed less than optimal image resolution, loss of illumination, inadequate parfocal capability, and loss of depth and width of field compared to the conventional microsurgical techniques. An earlier review (11) of these technological hurdles from this study's preliminary data has helped guide refinements of TOMS.
We are currently using TOMS in both the laboratory and clinical settings and are continuing to characterize the technological deficiencies of this prototype equipment. Once these deficiencies are resolved, TOMS will be ready for widespread implementation, and will positively affect the way microsurgery is performed today.