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
Osianderstraße 2-8
72076 Tübingen
Phone: 0 70 71/2 98 57 85
Fax: 07 07 1/29 59 18
Email: juergen.hoffmann@uni-tuebingen.de