Zusammenfassung
Einleitung: Es sollte eine neue Oberflächen-Laserscanner-Technik zur Patientenregistrierung für navigationsunterstützte Eingriffe experimentell und klinisch evaluiert werden.
Methodik: An einem anatomischen Schädelmodell wurden konventionelle radioopake Klebemarker in asymmetrischen Positionen befestigt und mittels 16-Zeilen-Multidetektor-Computertomographie (CT, Somatom Sensation 16, Siemens) gescannt. Die Registrierung erfolgte standardisiert sowohl mit dem Oberflächen-Laserscanner-System „z-touch®” (BrainLAB) als auch durch Anfahren der Standardmarker. Beide Verfahren wurden jeweils 25-mal durchgeführt und jeweils der mittlere Fehlerindex („root mean square error”, RMSE) sowie die Abweichung vom vordefinierten Zielpunkt dokumentiert. Bei 12 Patienten wurde die neue Laserscanner-Registrierung in Kombination mit dem Navigationssystem „VectorVision®” bei operativen Eingriffen am Gesichtsschädel eingesetzt. Basierend auf den Datensätzen einer hochauflösenden Mehrzeilen-CT erfolgte die intraoperative Registrierung mit dem neuen handgeführten Laserscanner. Mittels des Fehlerindex (RMSE) konnte die relative Genauigkeit der Registrierung erfasst werden. Die intraoperative Messgenauigkeit wurde in der axialen, sagittalen und koronaren Ebene anhand von eindeutigen anatomischen Landmarken überprüft und dokumentiert.
Ergebnisse: In den experimentellen Messdaten fanden sich signifikante Unterschiede bei den mittleren Fehlerindexwerten (Laserscan: 1,3 (0,14) mm versus Marker: 0,38 (0,01) mm, p < 0,005) und den Zielpunktabweichungen (Laserscan: 2,08 (0,49) mm vs. Marker: 0,99 (0,15) mm, p < 0,005). Die Korrelationsanalyse zeigte einen linearen Zusammenhang zwischen dem mittleren Fehlerindex (RMSE) und der Zielpunktabweichung bei Laserscanner- (r = 0,96) und Markertechnik (0,95). Unter Verwendung einer dosisreduzierten hochauflösenden Mehrzeilen-CT-Technik und der Oberflächen-Laserscanner-Technik ergab sich bei klinischer Anwendung ein mittlerer Fehlerindex (RMSE) von 1,21 (0,34) mm. Die intraoperative Genauigkeit, evaluiert an standardisierten anatomischen Punkten ergab Abweichungen von 1,8 (0,5) mm.
Schlussfolgerung: Die neue Laserscanner-Technik ermöglicht einen schnellen Abgleich der Schichtbilddaten mit der individuellen Morphologie, hierdurch ist eine vereinfachte und erweiterte klinische Nutzung der chirurgischen Navigation möglich.
Abstract
Introduction: Recent innovations in laser scanning technology provide a potentially useful tool for three-dimensional surface registration for image-guided surgery. The purpose of this study is to evaluate the clinical reliability of this technique in oral and maxillofacial surgical procedures using image-guided navigation.
Methods: In an experimental step, a stable anthropomorphic skull model with prelabeled markers was scanned and registered with laser surface scanning (z-touch®, BrainLAB) and marker- based algorithms. The registration protocol was then repeated 25-times. Root mean square error (RMSE) and target difference values were compared for their suitability for this application. Twelve patients with different indications for oral and maxillofacial surgery were planned for image-guided surgery using a passive infrared surgical navigation system (VectorVision®, BrainLAB). Preoperative computed tomography (CT) scans were carried out with newest 16-line multisclice CT-scanner (Siemens Somatom Sensation 16). The new markerless laser surface scanning technique was applied in all intraoperative patient registrations. Registration error was noted. The clinical application accuracy was determined for anatomical landmark localization deviation.
Results: In the experimental protocol a mean registration error (RMSE) or target difference of 1.3 (0.14) or 2.08 (0.49) mm for laser scanning and 0.38 (0.01) or 0.99 (0.15) mm for marker registration was found. The differences for RMSE and target localization were statistically significant (p < 0.005). Furthermore, a strong correlation between RMSE and target difference was found for laser scanning (r = 0.96) and marker registration (r = 0.95). During various clinical procedures involving oral and maxillofacial surgery, the overall error of the registration procedure determined as RMSE was 1.21 (0.34) mm. Intraoperatively, the mean clinical application accuracy was found to be 1.8 (0.5) mm.
Conclusion: Three-dimensional laser surface scanning technique may be a interesting and useful approach to register the patient for image-guided procedures, particularly during oral and craniomaxillofacial surgery.
Schlüsselwörter
3D-Oberflächenlaserscanner - Registrierung - bilddatengestützte Navigation - Mund-, Kiefer- und Gesichtschirurgie
Key words
3D-laser surface scanner - registration - image-guided navigation - craniomaxillofacial surgery
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Priv.-Doz. Dr. med. Dr. med. dent. Jürgen Hoffmann
Klinik und Poliklinik für Mund-, Kiefer- und Gesichtschirurgie, Universitätsklinikum Tübingen
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72076 Tübingen
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