'Direct DICOM slice landmarking' a novel research technique to quantify skeletal changes in orthognathic surgery

The limitations of the current methods of quantifying the surgical movements of facial bones inspired this study. The aim of this study was the assessment of the accuracy and reproducibility of directly landmarking of 3D DICOM images (Digital Imaging and Communications in Medicine) to quantify the changes in the jaw bones following surgery. The study was carried out on plastic skull to simulate the surgical movements of the jaw bones. Cone beam CT scans were taken at 3mm, 6mm, and 9mm maxillary advancement; together with a 2mm, 4mm, 6mm and 8mm “down graft” which in total generated 12 different positions of the maxilla for the analysis. The movements of the maxilla were calculated using two methods, the standard approach where distances between surface landmarks on the jaw bones were measured and the novel approach where measurements were taken directly from the internal structures of the corresponding 3D DICOME slices. A one sample t-test showed that there was no statistically significant difference between the two methods of measurements for the y and z directions, however, the x direction showed a significant difference. The mean difference between the two absolute measurements were 0.34±0.20mm, 0.22±0.16mm, 0.18±0.13mm in the y, z and x directions respectively. In conclusion, the direct landmarking of 3D DICOM image slices is a reliable, reproducible and informative method for assessment of the 3D skeletal changes. The method has a clear clinical application which includes the analysis of the jaw movements “orthognathic surgery” for the correction of facial deformities

Some forecast methods in regression models for categorical time series

We are dealing with the prediction of forthcoming outcomes of a categorical time series. We will assume that the evolution of the time series is driven by a covariate process and by former outcomes and that the covariate process itself obeys and autoregressive law. Two forecasting methods are presented. The first is based on an integral formula for the probabilities of forthcoming events and by a Monte Carlo evaluation of this integral. The second method makes use of an approximation formula for conditional expectations. The procedures proposed are illustrated by an application to data on forest damages. (orig.)Available from TIB Hannover: RR 6137(3) / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekSIGLEDEGerman

On the complexity of cutting-plane proofs

SIGLECopy held by FIZ Karlsruhe; available from UB/TIB Hannover / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekDEGerman

Results of the pilot study of a repeated measurements on clinical cases (Paired sample t-test).

<p>Results of the pilot study of a repeated measurements on clinical cases (Paired sample t-test).</p

The intra and inter examiner landmarking errors.

<p>The intra and inter examiner landmarking errors.</p

Bland-Altman plot showing the difference against mean in y (vertical) direction.

<p>Bland-Altman plot showing the difference against mean in y (vertical) direction.</p

Eight landmarks placed on the DICOM image slice and viewed in 3D: (A) Incisive foramen (IF). (B) Greater palatine right foramen (GPR). (C) Greater palatine left foramen (GPL). (D) Right Lingual foramen (RL). (E) Left Lingual foramen (LL). (F) Right mental foramen (RM). (G) Left Mental foramen (LM). (H) Lingual tubercle (LING).

<p>Eight landmarks placed on the DICOM image slice and viewed in 3D: (A) Incisive foramen (IF). (B) Greater palatine right foramen (GPR). (C) Greater palatine left foramen (GPL). (D) Right Lingual foramen (RL). (E) Left Lingual foramen (LL). (F) Right mental foramen (RM). (G) Left Mental foramen (LM). (H) Lingual tubercle (LING).</p

The differences between the two methods of measurements (Inter class correlation).

<p>The differences between the two methods of measurements (Inter class correlation).</p

Bland-Altman plot showing the difference against mean in z (sagittal) direction.

<p>Bland-Altman plot showing the difference against mean in z (sagittal) direction.</p

Voxel based registration, volume of interest selected on the anterior cranial base of the plastic skull.

<p>Voxel based registration, volume of interest selected on the anterior cranial base of the plastic skull.</p