Intraoperative Computed Tomography Guided Neuronavigation: Concepts, Efficiency, and Work

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1 Computer Aided Surgery ISSN: (Print) (Online) Journal homepage: Intraoperative Computed Tomography Guided Neuronavigation: Concepts, Efficiency, and Work Flow C. Matula, K. Rössler, M. Reddy, E. Schindler & W. T. Koos To cite this article: C. Matula, K. Rössler, M. Reddy, E. Schindler & W. T. Koos (1998) Intraoperative Computed Tomography Guided Neuronavigation: Concepts, Efficiency, and Work Flow, Computer Aided Surgery, 3:4, , DOI: / To link to this article: Informa UK Ltd All rights reserved: reproduction in whole or part not permitted Published online: 06 Jan Submit your article to this journal Article views: 167 Citing articles: 32 View citing articles Full Terms & Conditions of access and use can be found at

2 COmplltW Aided SUTT 3: (1 998) Intraoperative Computed Tomography Guided Neuronavigation: Concepts, Efficiency, and Work Flow C. Matula, M.D., K. Rossler, M.D., M. Reddy, M.D., E. Schindler, M.D., and W.T. Koos M.D. Neurosurgical Department (C.M., K R., M.R., W: T.K) and Neuroradiological Department (E.S.), University of Vienna, Vienna, Azlsh-ia ABSTRACT Image-guided surgery is currently considered to be of undisputed value in microsurgical and endoscopical neurosurgery, but one of its major drawbacks is the degradation of accuracy during frameless stereotactic neuronavigation due to brain and/or lesion shift. A computed tomography (CT) scanner system (Philips Tomoscan M) developed for the operating room was connected to a pointer device navigation system for image-guided surgery (Philips EasyGuide system) in order to provide an integrated solution to this problem, and the advantages of this combination were evaluated in 20 cases (15 microsurgical and 5 endoscopic). The integration of the scanner into the operating room setup was successful in all procedures. The patients were positioned on a specially developed scanner table, which permitted movement to a scanning position then back to the operating position at any time during surgery. Contrast-enhanced preoperative CCTs performed following positioning and draping were of high quality in all cases, because a radiolucent head fixation technique was used. The accuracy achieved with this combination was significantly better (1.6: ). The overall concept is one of working in a closed system where everything is done in the same room, and the efficiency of this is clearly proven in different ways. The most important fact is the time saved in the overall treatment process (about 55 h for one operating room over a 6-month period). The combination of an intraoperative CCT scanner with the pointer device neuronavigation system permits not only the intraoperative control of resection of brain tumors, but also (in about 20% of cases) the identification of otherwise invisible residual tumor tissue by intraoperative update of the neuronavigation data set. Additionally, an image update solves the problem of intraoperative brain and/or tumor shifts during image-guided resection. Having the option of making an intraoperative quality check at any time leads to significantly increased efficiency, improves the operating work flow because of the closed-system concept, and offers an integrated solution for improved patient work flow and clinical outcome. Comp Aid Surg 3: (1998) Wiley-Liss, hc. Kq wordc intraoperative CT, neuronavigation, concepts, efficiency, work flow INTRODUCTION With the help of a navigation system an old situation and not just guidance based on the expedream of every neurosurgeon comes true. For the rience and imagination of the ~urgeon.l.~-~j~ Imfirst time it is possible to have a direct, reliable age-guided surgery is today more than just a headconnection between the preoperative computed to- line or the playground of some computer mography (CT) scans and the actual intraoperative enthusiasts among the younger generation of neu- Address correspondence/reprint requests to: Dr. C. Matula, Neurosurgical Department, University of Vienna, AKH, Wmingergiirtel 18-20, A-1090 Vienna, Austria. Christian.Matula@univie.ac.at Wiley-Liss, Inc.

3 Matuha ct al.: Iniraopcrativc CT Guided Neuronuvigation 175 rosurgeons. Preoperative surgical planning using a computer workstation, as well as intraoperative guidance using a navigation system, has now become a fixed, integrated component of practically routine surgical procedures in every neurosurgical field, regardless of whether it is a so-called open microsurgical procedure or a neuroendoscopic operation within the brain.2v7-9 However, a major problem remains in the form of degradation of accuracy during frameless stereotactic neuronavigation due to brain and/or lesion shift.12-l4j6 To solve this problem, an intraoperative CT system was developed that can be connected to a navigation system to overcome the difficulty of working with preoperative images alone.5,6joj* This amazing technical development enables the surgeon to work within a closed intraoperative network based on an intraoperative CT navigation system; the surgeon is a fixed, integrated part of that network. The aim of this article is to demonstrate our concept of intraoperative CT guided navigation in microsurgery and neuroendoscopy, to prove its efficiency, and to explore the impact of such a system on work flow and patient care. MATERIAL AND METHODS Navigation System The system used for intraoperative navigation consists of a workstation, a camera unit, and a pointer device (EasyGuide Neuro, Philips Medical Systems). The pointer, equipped with three LCD diodes, is connected to the computer workstation by a cable. The light emitted by the diodes is recorded by an operating table mounted camera unit, which is also connected to the workstation by a cable. On the basis of the position of the LCD diodes, the computer calculates the exact three-dimensional (3-D) location, direction, and rotation of the tip of the pointer device and transfers these data to the scans stored in the computer. Intraoperative Computer Tomography The system is a mobile computer tomograph specially developed for application during operations (Tomoscan M, Philips Medical Systems). It consists of a mobile gantry and a mobile table for the patient, which is directly docked to the gantry. In addition, there is a separate workstation which is also mobile. This mobility enables the system to be moved wherever it is needed (e.g., to the operating room, intensive care station, trauma station, etc.). General Concepts Our concept is to perform the operation on the patient on the original CT table of the scanner. The whole procedure is therefore performed in the same operating room without moving the patient out for scanning. Anesthesia is also performed on the CT table, which carries all life-support systems. The gantry is the central element in the operating room and is fixed; the patient is moved into the system for scanning, then moved further through the gantry either for microsurgery or endoscopy. A complete scan series is performed before, after, and during surgery whenever necessary either with or without contrast medium. After the patient is positioned on the table using a simple head rest or a radiolucent head clamp, markers are applied to the patient s scalp. The patient is then moved into the scanning position and the initial preop scans are done. The data from these preop scans are transferred by cable through a Dicom3 connection into the workstation of the navigation system, and the operation is planned based on that information. Intraoperative CT Guided Neuronavigation in Microsurgery The situation during a typical microsurgical procedure is shown in Figure 1. The schematic illustration shows the positioning of the patient on the table as it is moved through the gantry. The surgeon is in front of the patient s head and the gantry, the nurse is beside the surgeon, and the anesthesiologist and his equipment are behind the gantry. The neuroradiologist is in the same room sitting at the workstation of the mobile CT. Figure 2 shows the actual situation in the operating room with the neurosurgeon working under the microscope. Notice how the positions correspond to the statements above and the schematic drawing. The neuronavigation system is directly beside him, allowing a clear view of the monitor of the unit. If necessary, the patient can be moved from the operating position into the scanning position, during which he remains covered with sterile drapes. Intraoperative CT Guided Neuronavigation in Neuroendoscopy As previously described, the patient can also be positioned on the original CT table in neuroendoscopic cases. Figure 3 shows the positioning of the patient, the neurosurgeon, the nurse, and the anesthesiologist. Notice the positioning of the navigation system and the endoscopic tower to give the surgeon a clear view of both monitors (Fig. 4).

4 176 Matuha et al.: Intraopwative CT &Lied Neumnavigation Fig. 1. system. Schematic drawing of positioning in the operating room when performing a microsurgical procedure within a closed After positioning the patient for surgery and fixing markers on the head, the preop scan is done. The scans are then transferred into the workstation of the navigation system. The key point is the special adaptor on the endoscope; with the LED markers on it, the scope becomes part of the system. The preop scans done on the positioned patient show a big monocystic lesion in the right hemisphere [Fig. 5(a)]. Based on that information, the neurosurgeon can be guided directly to the point of interest. On the left lower comer the endoscopic image appears as a picture in picture [Fig. 5(b)]. There are absolutely no anatomical landmarks that can be used for guidance. On the monitor of the navigation system, the exact positioning of the tip of the scope can be seen. Once the region of interest has been reached, more material can then be resected under direct visual control. RESULTS In the last 2 years more than 300 operations have been performed with the help of a navigation system. Extensive experience was thereby accumulated, leading the way to further developments, many of which have already been presented at meetings and/or published. During this period we have been able to work with the intraoperative CT unit described above. This report concerns the first 20 patients who were treated using both systems together in one unit. Installation and application was successfully performed in all cases without any technical problems. We had 5 neuroendoscopic cases and 15 microsurgical operations, including malignant and nonmalignant tumors of the brain and skull base. The transfer from the scanning position into the operating position was uncomplicated and successfully accomplished in all cases. The patients were draped in a special one-way material, and there were no cases of infection in the series. The combination, or rather the connection of the CT with the navigation system, ran smoothly. For calibration references we used small titanium screws that were inserted into the calvarian bone before the intraoperative scans were performed, and they were removed afterward. The recalibration was uneventful in all cases and had an accuracy of less than 2 mm (random mean square error). Efficiency The definition of efficiency is generally not easy; the question of efficiency is totally different de-

5 M a d et al.: Intraoperative CT Guided Neuronavigation 177 Fig. 2. The situation in the operating room. Intraoperative CT guided neuronavigation during a microsurgical procedure. pending on whether one is discussing the situation in the microsurgical or the endoscopic cases. In the microsurgical group (15 patients), it is our belief that neurosurgical efficiency should be defined as the percentage of cases in which the surgeon had to revise the initial result according to an intraoperative CT. Based on this definition, this situation occurred in about 20% (four patients) of our cases. In the endoscopic group (five patients), the definition of efficiency is different and involved three questions. The first question was in what percentage of patients could the target of interest be found. This was possible in all cases. The second question concerned the percentage of getting a conclusive histological staging. That was also possible in every case. All the cases were patients with monocystic intraparenchymatous tumors, so the third question concerned the percentage of patients in which the size of the cystic mass lesion could be reduced. That was also achieved in all cases by inserting a catheter connected to a subcutaneous reservoir under direct visual control. Work Flow What impact does such an integrated system have on work flow? This question can be answered from different viewpoints. A key factor is that everything happens in one room; the patient is placed on the CT table and operated on it and, as described above, the data transfer runs in a closed network consisting of the intraoperative CT, the navigation system, and the surgeon (Fig. 6). This is completely different than the former situation, an open system, where the information came from outside. It should be clear that this work flow affects many other individuals (e.g., the anesthesiologist and the neuroradiologist) as well, but discussing this and its relation to intraoperative CT guided neuronavigation would exceed the limits of this article. The general work flow starts at the moment the patient enters the hospital and continues until he or she leaves. This time span can be divided into four main periods: the preparation process (i.e., the time required to prepare the treatment); the treatment process (i.e., the operation); the quality process (including all the procedures necessary for quality control); and the release process, which comprises the time until the patient is discharged from the hospital. Comparing the group of patients treated with both intraoperative CT and neuronavigation with a comparable group having similiar pathology but who were treated without neuronavigation, the total elapsed time was about 20% shorter. Based on these findings, a single operating room saves 55 h

6 178 Ma& et al.: Intraoperative CT Guided Neutvnavigation Fig. 3. system. Schematic drawing of positioning in the operating room when performing an endoscopic procedure within a closed using the combined method over a period of 6 months. DISCUSSION In microsurgery and neuroendoscopy the advantages of using a navigation system are clear and undisputed as was demonstrated in a wide range of procedure^.'.^.^ The main problem is the fact that the navigation is based on preoperative scans, and actual intraoperative changes resulting from any loss of mass cannot be realized on the monitor of the navigation system. This may lead to navigation on the wrong track, which could result in a disaster if the surgeon is inexperienced ~10~*2~15 One solution might be the use of an intraoperative CT with the capability to update the reference scans intraoperatively when nece~sary.~-6j~j~ This would make it possible to visualize the real time situation and, of course, to work with that new situation. We must also consider the control mechanism of such a system. Intraoperative complications (e.g., bleedings, displacement of catheters, etc.) can be detected very early and corrected as soon as possible before surgery is completed. For the first time the surgeon is able to work in a closed network concerned partly with obtaining images (through the mobile CT) and partly with processing images (through the navigation system) so that the surgeon can integrate this information directly into his or her work. The transfer of information is carried out immediately, which is much faster than in a common open system.3.4 The random mean square error (i.e., the measurable accuracy) is much better (1.6: ) than that obtained with conventional approaches (3.2: ). Aside from the invaluable fact that any residual tumor can be precisely identified (in about 20% of cases in our series) and that possible complications can be visualized immediately (about 10% of our cases required emergency CT after a tumor operation), working in a closed system offers a significant savings of time. The total operating time is longer (about 30 min), but the total time of treatment is reduced by roughly 55 h over a 6-month period in one operating room. All this is combined with a clear improvement in comfort for the patient. The benefit of intraoperative CT in neurosurgery is clearly its ability to provide intraoperative updates for neuronavigation. It helps to eliminate, or at least to minimize, the problem of brain shift

7 Mat& et al.: Intraoperative CT Guided Neuronuvigation 179 Fig. 4. The situation in the operating room. Intraoperative CT guided neuronavigation during an endoscopic procedure. for neuronavigation and offers the possibility of intraoperative resection control, especially of brain tumors. In addition, the intraoperative CT offers the possibility of CT guided interventions (e.g., biopsies, catheter placements, or cyst aspirations). The monitoring of potential intraoperative complications is another major benefit, as is the possibility of having a neuroradiological verification of surgical results. The advantages of the combined application of intraoperative CT and neuronavigation are the realization of neuronavigation without preoperative images and the possibility of recalibration with intraoperative images at any time during ~urgery.5-6.8,9.~~.~6 Based on our results, there is a proven superiority in registration accuracy as compared to navigation using preoperative images. The detection, localization, and resection of residual tumor is another major advantage as is the intraoperative determination of tumor margins to achieve complete resection of intracerebral tumors. The accurate intraoperative correlation between instrument position and anatomical structures is sometimes amazing and is a good example of the high technical standards of current developments. However, the greatest advantage of using this combined system is the increase in the accuracy, safety, and precision of neurosurgical procedures. CONCLUSION Although there is an open discussion regarding the problems of using an intraoperative CT unit (e.g., merits of a radiolucent head-clamp, compatibility to other systems etc.), the application of a combination of such systems seems to be an absolute imperative, not only for a successful operation (quality check, recalibration) but also in the total treatment procedure (work flow, quality contro1).3.6, Saving time in the actual surgical treatment optimizes not only the clinical work flow (e.g., by eliminating patient transfer and transportation time) but also influences the overall long-term economy of effort by providing significantly increased efficiency. Intraoperative CT guided navigation should be used in the context of a closed system as described in this article. Having the option of making an intraoperative quality check at any time leads to a significant increase in the efficiency of the surgical treatment and improves the work flow in many directions. Based on our experience, integrated intraoperative CT guided neuronavigation is the solution for optimal patient treatment and clinical outcome.

8 180 Matula et al.: Intraoperative CT Guided Neuronuvigation Fig. 5. a: Preoperative scans taken in the OR on the positioned patient presenting the basis for intraoperative neuronavigation during an endoscopic procedure. b: View on the monitor of the workstation of the navigation system and as a picture in picture showing the endoscopic view from inside the cyst.

9 Marub et al.: Zntraoperative CT aided Neuronuvigation 181 Fig. 6. The closed surgical network. ACKNOWLEDGMENTS We would like to thank Mrs. Dobsak, Mr. Steinhauser, and Mr. Jager for their excellent help in preparing the figures and the manuscript. We are also very grateful to our neuroradiological partners Drs. K. Heimberger and H. Goerzer and to the neuroradiological staff for their help in making this work possible. REFERENCES Apuzzo MLJ (1996) The Richard Schneider Lecture: New dimension of neurosurgery in the realm of high technology-possibilities, practicalities, realities. Neurosurgery 38: Koos WT, Matula C, Rossler K, Schindler E, Heimberger K (1998) Case study: Palliative resection of a glioblastoma using intraoperative CT-guided navigation. Med Mundi 42: Koos WT, Roessler K, Matula C, Czech T, Schindler E (1997) Combination of intraoperative computed tomography (CCT) and image-guided neurosurgery. In Centennial Perspective: 1 1 th International Congress of Neurological Surgery. Bologna, Italy: Monduzzi Editore, pp Koos WT, Roessler K, Matula C, Czech T, Schindler E (1997) Combination of intraoperative computed to mography (CCT) and image-guided neurosurgery. Clin Neurol Neurosurg 99(Suppl 1 ): Lunsford LD, Parrish R, Albright L (1984) Intraoperative imaging with a therapeutic computed tomographic scanner. Neurosurgery Lunsford LD, Kondziolka D, Bissonette DJ (1996) Intraoperative imaging of the brain. Stereotact Funct Neurosurg Matula C, Koos WT, Rossler K, Schindler E, Heimberger K (1997) Case study: Cerebral biopsy using neuroendoscopy with CT-guided navigated neuroendoscopy. Med Mundi 42: Matula C, Roessler K, Reinprecht A, Koos WT (1997) Navigated neuroendoscopy. In Centennial Perspective: 1 lth International Congress of Neurological Surgery. Bologna, Italy: Monduzzi Editore, pp Matula C. Roessler K, Reinprecht A, Koos WT (1997) Navigated neuroendoscopy. Clin Neurol Neurosurg 99(Suppl 1):40. Okudera H, Kyoshima K, Kobayashi S, Sugita K (1994) Intraoperative CT scan findings during resection of glial tumors. Neurol Res 16: Okudera H, Kobayashi S. Kyoshima K, Tokushige K, Sugita K (1994) New radiolucent head fixation made of engineering plastics for intraoperative CT scanning. Acta Neurochir Wien 127:

10 182 Matula et al.: Intraoperative CT Guided Neuronavigation Roessler K, Dietrich W, Aichholzer M, Czech T, Matula C, Heimberger K, Goerzer H, Koos WT (1997) High application flexibility and intra-operative CCT update provided by a pointer device neuronavigation system. In Centennial Perspective: 1 lth International Congress of Neurological Surgery. Bologna, Italy: Monduzzi Editore, pp Roessler K, Ungersbtick K, Dietrich W, Aichholzer M, Hittmeir K, Matula C, Czech T, Koos WT (1997) Frameless stereotactic guided neurosurgery: Clinical experiences with an infrared based pointer device navigation system. Acta Neurochir Roessler K, Czech T, Ungersboeck K, Dietrich W, Aichholzer M, Nasel C, Hainfellner JR, Matula C, Koos WT (1997) Frameless stereotactic directed tissue sampling during glioma surgery improves appropriate tumor grading. Stereotact Funct Neurosurg 67:36. Rossler K, Ungersbijck K, Aichholzer M, Matula C, Koos WT (1996) Image guided neurosurgery: Frameless stereotactic guided resection of brain tumors. J Neurol Oncol 2:Suppl. 98. Rossler K, Ungersbtick K, Aichholzer M, Matula C, Koos WT (1996) Frameless stereotactic guided surgery: Clinical experiences comparing a LED based navigation system with a stereotactic guided microscope. Acta Neurochir 138:628. Watanabe E, Watanabe T, Manaka S, Mayanagi Y, Takakura K (1987) Three-dimensional digitizer (Neumnavigator): New equipment for computed tomography guided stereotaxic surgery. Surg Neurol27: