G. Strauß

Acquisition of process descriptions from surgical interventions

The recording and analysis of process descriptions from running surgical interventions is a very new and promising field named Surgical Workflows. Surgical Workflows fulfill two major objectives: they form the base of scientific evaluation and rapid prototyping of surgical assist systems, and they pave the road for the entering of workflow management systems into the operating room for intraoperative support of the surgeon. In this paper we describe how process descriptions from surgical interventions can be obtained for Surgical Process Modelling (SPM) as a specific domain of Business Process Modelling (BPM). After the introduction into the field of Surgical Workflows and the motivation of the research efforts, we deal with theoretical considerations about surgical interventions and the identification of classifications. Based on that, we propose the extendable structure for computational data acquisition support and conclude with use cases. The presented approach was applied to more than 200 surgical interventions of 10 different intervention types from otorhinolaryngology, neurosurgery, heart surgery, eye surgery, and interventional radiology, and it represents an ongoing project.

Interactive visualization for neck-dissection planning

In this paper, we present visualization techniques for neck dissection planning. These interventions are carried out to remove lymph node metastasis in the neck region. 3d visualization is intended to explore and to quantify anatomic and pathologic structures and thus support decisions concerning the surgical strategy. For this purpose we developed and combined visualization and interaction techniques such as cutaway views, silhouettes and colorcoded distances. In addition, a standardized procedure for processing and visualization of the patient data is presented.

Clinical Results in MR-Guided Therapy for Malignant Gliomas

The prognostic impact of the extent of tumour resection in surgery of malignant glioma patients remains controversial. We report the results of cumulative survival of malignant glioma patients operated with MR-guidance. Patients with complete tumour removal were compared with a population of patients with incomplete tumour removal. A 0.5 T scanner was used to criticize the extent of resection during surgery. In total no significant difference could be found, however there is a tendency that complete tumour removal seems to be associated with a slightly increased median survival time.

Assessment of technical needs for surgical equipment by surgical process models

Abstract The presented approach introduces a method for estimating the potential benefit of a surgical assist system prior to its actual development or clinical use. The central research question is: What minimal requirements must a future system meet so that its use would be more advantageous than a conventional or already existent method or system, and how can these requirements be obtained from routine clinical data? Forty-three cases of lumbar discectomies were analyzed with regard to activities related to bone ablation in order to predict the temporal requirements for an alternative strategy of using a surgical assist system for bone ablation. The study recorded and analyzed surgical process models (SPM), which are progression models with detailed and exact-to-the-second representations of surgical work steps, as a sensible means for the detailed quantification of the temporal needs of the system. The presented methods can be used for a systematic analysis of such requirements. Implementation of these methods will prove very useful in the future from a medical, technical, and administrative point of view. Manufacturers can use this analytical procedure to derive parameters for their systems that indicate success criteria. Additionally, hospitals can decide, before making actual capital expenditure decisions, if the system of interest is superior to the conventional strategy and therefore worth the investment.

Untersuchungen zur Effizienz eines Navigationssystems für die HNO-Chirurgie: Auswertungen von 300 Patienten

PROBLEM The aim of this study is to proof the clinical efficiency by using a modern navigation system for Functional Endoscopic Sinus Surgery (FESS). MATERIAL AND METHODS An optical navigation system was used in clinical routine of 300 patients. Two groups with 150 patients each were examined. Group A was treated with navigation assistance (Karl Storz Navigation Panel Unit NPU), Group B was treated without navigation by conventional FESS. Examination period was limited to 12 months. Median follow-up is 22 and 26 weeks. Perioperative, intraoperative and postoperative parameters were recorded by workflow-analysis, clinical and radiological findings and standardized questionnary. RESULTS Application of the navigation system needs 1.1 min additional perioperative time in average. Intraoperative time reduction by the navigation system was about 10 min per case (Group A 32.6 (SD 11.2) min, Gruppe B 42.7 (SD 9.5) min). Specific information by the navigation system was evaluated in all surgical areas as usefull and additional to a-priori-knowledge. Postoperatively patients from group A (10/89) show lower rate of re-polyposis then in group B (24/71). Fenestration of the sphenoid sinus were sufficient by CT-evaluation in 100% (group A) and 23% (group B). CONCLUSIONS The advantages of the examined navigation system in comparison to the gold standard of FESS are proven. Navigation assistance led to an reduced intraoperative time consumption, increased postoperative results and lowered the workload of the surgeons.

[Improvement of registration accuracy for navigated-control drill in mastoidectomy (autopilot)].

BACKGROUND The goal of this study is the improvement of the surgical accuracy of a navigate-controlled drill for mastoidectomy in a lab test. METHODS For lab tests an artificial model of the temporal bone with color-coded injury identification of the facial nerve (solution of 0.5 mm) was used. Two different registration methods were examined: (group 1) navigation bow with 4 integrated markers at the upper jaw; (group 2) landmark registration with 4 titanium micro screws. An optical navigation system was used. The targets were illustrated by 3 titanium screws within the range of the planum mastoideum. The accuracy of the navigate-controlled drill in drilling the planned cavity were evaluated at 20 temporal bone models. The measurement of the registration accuracy was evaluated by deviation between the target screw and the calculated position in the navigation system. The evaluation of the resulted cavities was done by 5 senior surgeons with the help of the microscope. RESULTS The registration accuracy shows a maximum deviation between the real position and the calculated position of 1,73 MM in group of 1 and 0.93 MM in group 2. In group 1 the nerve was hurt in 5/20 cases and a maximum deviation of - 1.5 mm (Std 0.25 mm) (drilled beyond the nerve) was measured. In group 2 the nerve was not hurt, a maximum deviation of 0.5 mm (too early stopped before the nerve) was measured. CONCLUSIONS Significantly better results of the registration and drilling accuracy show up in group group 2. Thus the preconditions for clinical use are fulfilled.

Computerassistierte Chirurgie an der Rhinobasis

The procedure of instrument navigation has been an established one since its introduction in ENT by Schloendorff. It facilitates better intraoperative orientation. The opto-electric and electromagnetic procedures are sophisticated principles of intraoperative position recognition. It can be assumed that up to 30% of all ENT hospitals in Germany have access to navigation systems. These systems are used almost exclusively for functional endoscopic sinus surgery (FESS). The impact of instrument navigation is estimated by surgeons predominantly positively. A navigation system enables a saving of up to 10% in terms of operating time. Extended approaches in the frontal skull base appear to benefit from the use of navigation support to a high degree. However, scientific data are still lacking. The current boundaries of simple instrument navigation in the frontal skull base are set by the attainable accuracy of approx. 2 mm and the relatively simple representation of the information in planar sectional views. Instrument navigation should be used in the frontal skull base as frequently as possible, even in less complex procedures. Only in this way can familiarity with the system be achieved.

QR-Code Patienten-Tracking: eine kostengünstige Möglichkeit zur Verbesserung der Patientensicherheit

BACKGROUND Hospitals are implementing a risk management system to avoid patient or surgery mix-ups. The trend is to use preoperative checklists. This work deals specifically with a type of patient identification, which is realized by storing patient data on a patient-fixed medium. MATERIAL AND METHODS In 127 ENT surgeries data relevant for patient identification were encrypted in a 2D-QR-Code. The code, as a separate document coming with the patient chart or as a patient wristband, has been decrypted in the OR and the patient data were presented visible for all persons. The decoding time, the compliance of the patient data, as well as the duration of the patient identification was compared with the traditional patient identification by inspection of the patient chart. RESULTS A total of 125 QR codes were read. The time for the decrypting of QR-Code was 5.6 s, the time for the screen view for patient identification was 7.9 s, and for a comparison group of 75 operations traditional patient identification was 27.3 s. Overall, there were 6 relevant information errors in the two parts of the experiment. This represents a ratio of 0.6% for 8 relevant classes per each encrypted QR code. CONCLUSION This work allows a cost effective way to technically support patient identification based on electronic patient data. It was shown that the use in the clinical routine is possible. The disadvantage is a potential misinformation from incorrect or missing information in the HIS, or due to changes of the data after the code was created. The QR-code-based patient tracking is seen as a useful complement to the already widely used identification wristband.

Dreidimensionale Bildprozessierung in der HNO-Onkologie zur präoperativen Planung und Evaluierung

There are a lot of diagnostic possibilities for the preoperative planning in head and neck surgery. So far, no study was performed to evaluate if there is an advantage of three-dimensional visualization compared to conventional computed tomography yet. Additionally, there are no specifications for such a visualization prior surgery in head and neck surgery. This work describes different possibilities for segmentation and three-dimensional visualization for preoperative planning in head and neck surgery and tumor volumetry compared to conventional computed tomography. We describe new techniques and specifications for three-dimensional visualization.

Teleteaching in der HNO-Heilkunde

The transmission of scientific seminars into the Internet represents a new application of modern technologies for teleteaching.We digitally recorded 74 seminars and discussions during the 8th annual meeting of the German Society of Skull Base Surgery with five cameras and eight microphones, and transformed the data live with the real-Producer using a video card.This transferred data stream was sent via ISDN (128 kbit/s) to a real-server at the university, which was used for distribution in the net.The seminars could be called up in the display format of 320×240 pixels with a delay of 3 min (minimum: 30 s, as a function of the connection of the user) at each computer with Internet entrance. Altogether,we registered 3,284 accesses to the presentations following the congress until June 2002. The quality of picture transmission (24-36 kbit/s) and the quality of tone (audio stream: 5 kbit/s) were sufficient to understand the contents of the slide, video or computer presentation.The transmission of scientific meetings into the Internet can increase, with a justifiable technical expenditure, their efficiency by the ubiquitous availability of the information and the extension of the audience.ZusammenfassungDie Übertragung wissenschaftlicher Vorträge in das Internet stellt eine neue Anwendung moderner Informationstechnologien für das Teleteaching dar.Wir zeichneten 74 Vorträge und Diskussionen während der 8. Jahrestagung der Deutschen Gesellschaft für Schädelbasischirurgie digital mit 5 Kameras und 8 Mikrofonen auf und encodierten die Daten live mit dem real-Producer® unter Nutzung einer Videokarte.Diese übertrug den Datenstrom über eine ISDN-Leitung mit einer Kanalbündelung (128 kbit/s) zu einem real-Server® im Universitätsrechenzentrum, der für die Weiterverteilung genutzt wurde.Die Vorträge konnten im Bildformat 320×240 Pixel mit einer Verzögerung von durchschnittlich 3 min (Minimum: 30 s, in Abhängigkeit von der Verbindung des Nutzers) an jedem Rechner mit Internet-Zugang abgerufen werden.Wir registrierten im Anschluss an den Kongress bis zum Juni 2002 3.284 Zugriffe auf Beiträge dieser Veranstaltung in der Datenbank.Die Bild-Übertragungsqualität (24–36 kbit/s) und die Tonqualität (Audio-Stream: ab 5 kbit/s) waren ausreichend, um die Inhalte der Dia-, Video- und Computerpräsentationen zu erfassen.Die Übertragung wissenschaftlicher Veranstaltungen in das Internet kann deren Effizienz durch die ubiquitäre Verfügbarkeit der Informationen und die Erweiterung des Auditoriums bei einem vertretbaren technischen Aufwand steigern.AbstractThe transmission of scientific seminars into the Internet represents a new application of modern technologies for teleteaching.We digitally recorded 74 seminars and discussions during the 8th annual meeting of the German Society of Skull Base Surgery with five cameras and eight microphones, and transformed the data live with the real-Producer using a video card.This transferred data stream was sent via ISDN (128 kbit/s) to a real-server at the university, which was used for distribution in the net.The seminars could be called up in the display format of 320×240 pixels with a delay of 3 min (minimum: 30 s, as a function of the connection of the user) at each computer with Internet entrance. Altogether,we registered 3,284 accesses to the presentations following the congress until June 2002. The quality of picture transmission (24–36 kbit/s) and the quality of tone (audio stream: 5 kbit/s) were sufficient to understand the contents of the slide, video or computer presentation.The transmission of scientific meetings into the Internet can increase, with a justifiable technical expenditure, their efficiency by the ubiquitous availability of the information and the extension of the audience.