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We propose a novel and efficient initialization method for generalized facial landmark localization with an unsupervised roll-angle estimation based on B-spline models. We first show that the roll angle is crucial for an accurate landmark localization. Therefore, we develop an unsupervised roll-angle estimation by adopting a joint 1 st -order B-spline model, which is robust to intensity variations and generic for application to various face detectors. The method consists of three steps. First, the scaled-normalized Laplacian of Gaussian operator is applied to a bounding box generated by a face detector for extracting facial feature segments. Second, a joint 1 st -order B-spline model is fitted to the extracted facial feature segments, using an iterative optimization method. Finally, the roll angle is estimated through the aligned segments. We evaluate four state-of-the-art landmark localization schemes with the proposed roll-angle estimation initialization in the benchmark dataset. The proposed method boosts the performance of landmark localization in general, especially for cases with large head pose. Moreover, the proposed unsupervised roll-angle estimation method outperforms the standard supervised methods, such as random forest and support vector regression by 41.6% and 47.2%, respectively.

Accurate segmentation of teeth in dental imaging is a principal element in computer-aided design (CAD) in modern dentistry. In this paper, we present a new framework based on deep learning models for segmenting tooth instances in 3D point cloud data of an intra-oral scan (IOS). At high level, the proposed framework, called Mask-MCNet, has analogy to the Mask R-CNN, which gives high performance on 2D images. However, the proposed framework is designed for the challenging task of instance segmentation of point cloud data from surface meshes. By employing the Monte Carlo Convolutional Network (MCCNet), the Mask-MCNet distributes the information from the processed 3D surface points into the entire void space (e.g. inside the objects). Consequently, the model is able to localize each object instance by predicting its 3D bounding box and simultaneously segmenting all the points inside each box. The experiments show that our Mask-MCNet outperforms state-of-the-art for IOS segmentation by achieving 98% IoU score.

The usage of three-dimensional ultrasound (3D US) during image-guided interventions for e.g. cardiac catheterization has increased recently. To accurately and consistently detect and track catheters or guidewires in the US image during the intervention, additional training of the sonographer or physician is needed. As a result, image-based catheter detection can be beneficial to the sonographer to interpret the position and orientation of a catheter in the 3D US volume. However, due to the limited spatial resolution of 3D cardiac US and complex anatomical structures inside the heart, image-based catheter detection is challenging. In this paper, we study 3D image features for image-based catheter detection using supervised learning methods. To better describe the catheter in 3D US, we extend the Frangi vesselness feature into a multi-scale Objectness feature and a Hessian element feature, which extract more discriminative information about catheter voxels in a 3D US volume. In addition, we introduce a multi-scale statistical 3D feature to enrich and enhance the information for voxel-based classification. Extensive experiments on several in-vitro and ex-vivo datasets show that our proposed features improve the precision to at least 69% when compared to the traditional multi-scale Frangi features (from 45% to 76% at a high recall rate 75%). As for clinical application, the high accuracy of voxel-based classification enables more robust catheter detection in complex anatomical structures.