TINA manual landmarking tool: software for the precise digitization of 3D landmarks

Background: Interest in the placing of landmarks and subsequent morphometric analyses of shape for 3D data has increased with the increasing accessibility of computed tomography (CT) scanners. However, current computer programs for this task suffer from various practical drawbacks. We present here a free software tool that overcomes many of these problems. Results: The TINA Manual Landmarking Tool was developed for the digitization of 3D data sets. It enables the generation of a modifiable 3D volume rendering display plus matching orthogonal 2D cross-sections from DICOM files. The object can be rotated and axes defined and fixed. Predefined lists of landmarks can be loaded and the landmarks identified within any of the representations. Output files are stored in various established formats, depending on the preferred evaluation software. Conclusions: The software tool presented here provides several options facilitating the placing of landmarks on 3D objects, including volume rendering from DICOM files, definition and fixation of meaningful axes, easy import, placement, control, and export of landmarks, and handling of large datasets. The TINA Manual Landmark Tool runs under Linux and can be obtained for free from http://www.tina-vision.net/tarballs/

Quantitative shape analysis with weighted covariance estimates for increased statistical efficiency

BACKGROUND: The introduction and statistical formalisation of landmark-based methods for analysing biological shape has made a major impact on comparative morphometric analyses. However, a satisfactory solution for including information from 2D/3D shapes represented by ‘semi-landmarks’ alongside well-defined landmarks into the analyses is still missing. Also, there has not been an integration of a statistical treatment of measurement error in the current approaches. RESULTS: We propose a procedure based upon the description of landmarks with measurement covariance, which extends statistical linear modelling processes to semi-landmarks for further analysis. Our formulation is based upon a self consistent approach to the construction of likelihood-based parameter estimation and includes corrections for parameter bias, induced by the degrees of freedom within the linear model. The method has been implemented and tested on measurements from 2D fly wing, 2D mouse mandible and 3D mouse skull data. We use these data to explore possible advantages and disadvantages over the use of standard Procrustes/PCA analysis via a combination of Monte-Carlo studies and quantitative statistical tests. In the process we show how appropriate weighting provides not only greater stability but also more efficient use of the available landmark data. The set of new landmarks generated in our procedure (‘ghost points’) can then be used in any further downstream statistical analysis. CONCLUSIONS: Our approach provides a consistent way of including different forms of landmarks into an analysis and reduces instabilities due to poorly defined points. Our results suggest that the method has the potential to be utilised for the analysis of 2D/3D data, and in particular, for the inclusion of information from surfaces represented by multiple landmark points

Learning to recognise talking faces

An approach for person identification is described based on spatio-temporal analysis of the talking face. A person is represented by a parametric model of the visible speech articulators and their temporal characteristics during speech production. The model consists of shape parameters, representing the lip contour and intensity parameters representing the grey level distribution in the mouth region. The model is used to track lips in image sequences where the model parameters are recovered from the tracking results. While some of these parameters relate to speech information, others are intuitively related to different persons and we show that models based on these features enable successful person identification. We model the shape and intensity parameters as mixtures of Gaussians and their temporal dependencies by Hidden Markov Models. Identifying a talking person is performed by estimating the likelihood of each model for having generated the observed sequence of features and the model with the highest likelihood is chosen as the identified person

Statistical lip modelling for visual speech recognition

We describe a speechreading (lipreading) system purely based on visual features extracted from grey level image sequences of the speakers lips. Active shape models are used to track the lip contours while visual speech information is extracted from the shape of the contours. The distribution and temporal dependencies of the shape features are modelled by continuous density Hidden Markov Models. Experiments are reported for speaker independent recognition tests of isolated digits. The analysis of individual feature components suggests that speech relevant information is embedded in a low dimensional space and fairly robust to inter- and intra- speaker variability

Automatic Identification of Morphometric Landmarks in Digital Images

We present an automated system for the analysis of edge based structure for use in morphomet-ric studies. The current work takes a grey level image of a Drosophila wing as input and extracts the coordinates of 15 landmarks. The proposed method extracts the ridges (linear features such as wing veins) using the knowledge of their known grey level profile and the noise character

Active Shape Models for Visual Speech Feature Extraction

Most approaches for lip modelling are based on heuristic constraints imposed by the user. We describe the use of Active Shape Models for extracting visual speech features for use by automatic speechreading systems, where the deformation of the lip model as well as image search is based on a priori knowledge learned from a training set. We demonstrate the robustness and accuracy of the technique for locating and tracking lips on a database consisting of a broad variety of talkers and lighting conditions

Visual Speech Recognition using Active Shape Models and Hidden Markov Models

This paper describes a novel approach for visual speech recognition. The shape of the mouth is modelled by an Active Shape Model which is derived from the statistics of a training set and used to locate, track and parameterise the speaker�s lip movements. The extracted parameters representing the lip shape are modelled as continuous probability distributions and their temporal dependencies are modelled by Hidden Markov Models. We present recognition tests performed on a database of a broad variety of speakers and illumination conditions. The system achieved an accuracy of 85.42 % for a speaker independent recognition task of the first four digits using lip shape information only