Michaela Benz

Reliability of a Method for Computing Facial Symmetry Plane and Degree of Asymmetry Based on 3D-data.

Objective:The objective of this study was to analyze the reliability of a landmark-independent method for determining the facial symmetry plane and degree of asymmetry based on three-dimensional data from the facial surface from two sets of recordings, one performed consecutively and one performed on different days.Materials and Methods:We used an optical 3D-sensor to obtain the facial data of one male subject in two sets of ten measurements: the first taken consecutively and the second on different days. The symmetry plane and degree of asymmetry were calculated for each of the resulting twenty sets of data. One set of data was analyzed ten times for control purposes. The calculation of the mean deviation angle between the symmetry planes served as a measure of the reproducibility of these results.Results:Although the mean angular deviations of the computed symmetry planes, 0.134° (for ten consecutively captured images) and 0.177° (for the ten images captured on different days), were each significantly higher than the mean angular deviation (0.028°) calculated from ten analyses of a single image, they can still be regarded as very small. There were no significant differences in the degree of asymmetry among the three measurement sets. The standard deviations revealed low values.Conclusions:This method can be used to compute with high reliability the symmetry planes and degree of asymmetry of facial 3D-data. The color-coded visualization of asymmetrical facial regions makes it possible for this analytical procedure to capture the asymmetries of facial soft tissue with substantially greater precision than 2-dimensional en face images.ZusammenfassungZielsetzung:Ziel der vorliegenden Untersuchung war es, die Reliabilität einer landmarkenunabhängigen Methode zur Berechnung der Gesichtssymmetrieebene und des Asymmetriegrades bei aufeinanderfolgenden beziehungsweise an verschiedenen Tagen durchgeführten 3-D-Aufnahmen zu analysieren.Material und Methodik:Die 3-D-Gesichtsdaten eines männlichen Probanden wurden mit einem optischen Sensor erfasst. Es wurden zehn Aufnahmen direkt nacheinander sowie an verschiedenen Tagen durchgeführt, für welche jeweils die Symmetrieebene und der Asymmetriegrad berechnet wurden. Zusätzlich wurde eine Aufnahme zehnmal ausgewertet. Die Berechnung der mittleren Winkelabweichung zwischen den Symmetrieebenen diente als Maß für die Reproduzierbarkeit der Methode.Ergebnisse:Die mittlere Winkelabweichung der berechneten Symmetrieebenen war mit 0,134° (zehn Aufnahmen nacheinander) und 0,177° (zehn Aufnahmen an verschiedenen Tagen) zwar signifikant höher als bei zehnmaliger Auswertung derselben Aufnahme (0,028°), ist jedoch als sehr gering zu bewerten. Bezüglich des Asymmetriegrades gab es keine statistisch signifikanten Unterschiede zwischen den drei Auswerteserien, die jeweiligen Standardabweichungen waren gering.Schlussfolgerungen:Mit Hilfe der vorgestellten Methode können reproduzierbar die Symmetrieebene sowie der Asymmetriegrad anhand von 3-D-Gesichtsdaten bestimmt werden. Durch die farbkodierte Visualisierung von asymmetrischen Gesichtsbereichen ermöglicht dieses Analyseverfahren eine wesentlich präzisere Diagnostik von Asymmetrien der Gesichtsweichteile als zweidimensionale En-face-Aufnahmen.

Validation of in vivo assessment of facial soft-tissue volume changes and clinical application in midfacial distraction: a technical report.

&NA; The purpose of this study was to validate the assessment of visible volume changes of the facial soft tissue with an optical three‐dimensional sensor and to introduce new parameters for the evaluation of the soft‐tissue shape achieved from three‐dimensional data of selected cases of midfacial distraction. Images of a truncated cone of known volume were assessed repeatedly with an optical three‐dimensional sensor based on phase‐measuring triangulation to calculate the volume. Two cubic centimeters of anesthetic solution was injected into the right malar region of 10 volunteers who gave their informed consent. Three‐dimensional images were assessed before and immediately after the injections for the assessment of the visible volume change. In five patients who underwent midfacial distraction after a high quadrangular Le Fort I osteotomy, three‐dimensional scans were acquired before and 6 and 24 months after the operation. The visible soft‐tissue volume change in the malar‐midfacial area and the mean distance of the accommodation vector that transformed the preoperative into the postoperative surface were calculated. The volume of the truncated cone was 235.26 ± 1.01 cc, revealing a measurement uncertainty of 0.4 percent. The injections of anesthetic solution into the malar area resulted in an average visible volume change of 2.06 ± 0.06 cc. The measurement uncertainty was 3 percent. In the five patients, the average distance of maxillary advancement was 6.7 ± 2.3 mm after 6 months and 5.4 ± 3.0 mm after 2 years. It was accompanied by a mean visible volume increase of 8.92 ± 5.95 cc on the right side and 9.54 ± 4.39 cc on the left side after 6 months and 3.54 ± 3.70 cc and 4.80 ± 3.47 cc, respectively, after 2 years. The mean distance of the accommodation vector was 4.41 ± 1.94 mm on the right side and 4.74 ± 1.32 mm on the left side after 6 months and 1.62 ± 1.96 mm and 2.16 ± 1.52 mm, respectively, after 2 years. The assessment of visible volume changes by optical three‐dimensional images can be carried out with considerable accuracy. The determination of volume changes and accompanying accommodation vectors completes the cephalometric analysis during the follow‐up of patients undergoing midfacial distraction. The new parameters will help to assess normative soft‐tissue data on the basis of three‐dimensional imaging with a view to an improved three‐dimensional prediction of the operative outcome of orthognathic surgery. (Plast. Reconstr. Surg. 112: 367, 2003.)

Influence of Early Hard Palate Closure in Unilateral and Bilateral Cleft Lip and Palate on Maxillary Transverse Growth During the First Four Years of Age

OBJECTIVE To evaluate and compare the effects of early primary closure of the hard palate on the anterior and posterior width of the maxillary arch in children with bilateral (BCLP) and unilateral (UCLP) cleft lip and palate during the first 4 years of life. DESIGN A retrospective, mixed-longitudinal study. SETTING Cleft Palate Center of the University of Erlangen-Nuremberg. SUBJECTS AND METHODS The present investigation analyzes longitudinally 42 children with UCLP and 8 children with BCLP between 1996 and 2000 with early simultaneous primary closure of lip and hard palate (4 to 5 months). Palatal arch width was measured on dental casts with a computer-controlled three-dimensional digitizing system, and their growth velocities were calculated from consecutive periods (mean follow-up 39 months). Differences in growth velocities were compared with those of 25 children with UCLP and 15 children with BCLP with delayed closure of hard palate (12 to 14 months). RESULTS AND CONCLUSIONS There was no significant difference in terms of anterior and posterior maxillary width between early and delayed closure of hard palate within the first 4 years of life.

AUTOMATIC COARSE REGISTRATION OF 3D SURFACE DATA IN ORAL AND MAXILLOFACIAL SURGERY

M. BENZ, N. SCHÖN, E. NKENKE, F. W. NEUKAM, F. VOGT, G. HÄUSLER Chair for Optics, Institute for Optics, Information and Photonics, University of Erlangen-Nuremberg, Staudtstr. 7/B2, 91058 Erlangen, Germany Department of Oral and Maxillofacial Surgery, University Erlangen-Nuremberg, Glückstr. 11, 91054 Erlangen, Germany Chair for Pattern Recognition, University Erlangen-Nuremberg, Martensstr. 3, 91058 Erlangen, Germany

Automated classification of bone marrow cells in microscopic images for diagnosis of leukemia: a comparison of two classification schemes with respect to the segmentation quality

The morphological analysis of bone marrow smears is fundamental for the diagnosis of leukemia. Currently, the counting and classification of the different types of bone marrow cells is done manually with the use of bright field microscope. This is a time consuming, partly subjective and tedious process. Furthermore, repeated examinations of a slide yield intra- and inter-observer variances. For this reason an automation of morphological bone marrow analysis is pursued. This analysis comprises several steps: image acquisition and smear detection, cell localization and segmentation, feature extraction and cell classification. The automated classification of bone marrow cells is depending on the automated cell segmentation and the choice of adequate features extracted from different parts of the cell. In this work we focus on the evaluation of support vector machines (SVMs) and random forests (RFs) for the differentiation of bone marrow cells in 16 different classes, including immature and abnormal cell classes. Data sets of different segmentation quality are used to test the two approaches. Automated solutions for the morphological analysis for bone marrow smears could use such a classifier to pre-classify bone marrow cells and thereby shortening the examination duration.

Computer-Assisted Diagnosis in Colposcopy: Results of a Preliminary Experiment?

Purpose: Diagnosis of cervical intraepithelial neoplasia (CIN) is currently based on the histological result of an aiming biopsy. This preliminary study investigated whether diagnostics for CIN can potentially be improved using semiautomatic colposcopic image analysis. Methods: 198 women with unremarkable or abnormal smears underwent colposcopy examinations. 375 regions of interest (ROIs) were manually marked on digital screen shots of the streaming documentation, which we provided during our colposcopic examinations (39 normal findings, 41 CIN I, and 118 CIN II–III). These ROIs were classified into two groups (211 regions with normal findings and CIN I, and 164 regions with CIN II–III). We developed a prototypical computer-assisted diagnostic (CAD) device based on image-processing methods to automatically characterize the color, texture, and granulation of the ROIs. Results: Using n-fold cross-validation, the CAD system achieved a maximum diagnostic accuracy of 80% (sensitivity 85% and specificity 75%) corresponding to a correct assignment of abnormal or unremarkable findings. Conclusions: The CAD system may be able to play a supportive role in the further diagnosis of CIN, potentially paving the way for new and enhanced developments in colposcopy-based diagnosis.

Informationsoptimierte Merkmale zur Grobregistrierung von Freiform-Flächen

Immer mehr computergestutzte medizinische Verfahren nutzen dreidimensionale Flachen bei der Planung und Durchfuhrung chirurgischer Eingriffe, der Analyse anatomischer Strukturen und der Diagnose. In vielen dieser Anwendungen ist ein wichtiger Verarbeitungsschritt die gegenseitige Ausrichtung (Registrierung) verschiedener Flachendatensatze (Ansichten) eines Objektes. Kleine Abweichungen zwischen den Datensatzen konnen durch Optimierungsverfahren minimiert werden (Feinregistrierung), z.B. durch Varianten des sog. ICP-Algorithmus. Die vorausgehende grobe Ausrichtung der Daten (Grobregistrierung) muss aber bisher oft noch manuell durchgefuhrt werden und erfordert Zeit und Aufmerksamkeit, was den praktischen Einsatz entsprechender Systeme deutlich einschrankt. Diesem Problem wollen wir uns mit der vorliegenden Arbeit zuwenden. Es wird eine Methode zur Berechnung robuster Merkmale vorgestellt, die es ermoglicht, Flachenpunkte mit hohem Informationsgehalt lokal zuverlassig zu charakterisieren und so deren effiziente Zuordnung zu ermoglichen.

Stitching Pathological Tissue Images using DOP Feature Tracking

This contribution introduces an approach for stitching multiple images of a histological slide to a panorama image using Differences of Paraboloids (DOP). DOP provides a novel method for the detection, description and matching of features of two overlapping images. In our context of manual whole-slide imaging (WSI), DOP extracts essential keypoints of an image and describes them with feature vectors considering the keypoint’s neighborhood. The DOP feature vector of the current image is then matched against the feature vectors of all previous images. With matching correspondences, a feature based image registration is generated that estimates the translation between two overlapping images. Likewise, all images are aligned to form a whole-slide panorama. Our results reveal a superior stitching quality employing the presented DOP approach in comparison to the well-known SIFT and SURF. Our evaluation is based on the homogeneity at the artifically created edges in the panorama due to the stitching. The DOP offers a convincing solution to stitch pathological tissue.

Weichgewebemodellierung durch Flächeninterpolation heterogen verteilter Messdaten

In vielen Operationssituationen muss der Chirurg trotz Weichgewebeschwellung im Eingriffsgebiet eine Pradiktion des postoperativen Zustands treffen. Zur Unterstutzung des Arztes kann die Schwellung anhand des Volumens zwischen den Gewebeflachen von Haut und Knochen quantifiziert werden. In diesem Beitrag wird eine Methode vorgestellt, die mittels Gewebekonturen aus 2D-Ultraschallbildern intraoperativ eine Weichgewebemodellierung durchfuhrt. Dies geschieht anhand einer analytischen Flachenbeschreibung der heterogen verteilten, fehlerbehafteten Messdaten. Die verwendeten Methoden basieren einerseits auf Interpolation mit radialen Basisfunktionen kombiniert mit Glattungsmasnahmen, andererseits werden Approximationsmethoden mit Polynomen und radialen Basisfunktionen untersucht. Die aus Haut- und Knochenkonturen gewonnenen Ergebnisse der Interpolation werden denen der Approximationen gegenubergestellt.

Automatische Segmentierung der Gewebegrenzen in 2D-Ultraschalldaten aus der Mund-, Kiefer- und Gesichtschirurgie

Es soll ein Modell der Gewebeschwellung bei Operationen im Gesichtsbereich erstellt werden. Zur Berechnung des Modells werden zunachst Daten mit einem optischen 3D-Sensor, sowie einem Ultraschallsensor akquiriert. Fur den Modellierungsprozess ist es notwendig, die Haut- und die Knochengrenze aus den zweidimensionalen Ultraschallschnittbildern zu segmentieren. Die vorliegende Arbeit stellt ein vollautomatisches und robustes Verfahren zur Segmentierung der Konturen von Haut und Knochen vor.