Unsupervised distribution-aware keypoints generation from 3D point clouds

Keypoints extraction from 3D objects is a fundamental task in point cloud processing. The ideal keypoints should be an ordered and well-aligned set of points that effectively reflect the shape and structure of the object. To this end, this paper proposes an unsupervised 3D point cloud keypoints generation network with the consideration of the probability distribution of keypoints and spatial distribution among keypoints. The network downsamples and groups the 3D point cloud, obtaining local features of the point cloud. The local features are leveraged to explicitly learn the mixture probability distribution of keypoint position. A composite loss function that comprehensively considers shape similarity, point importance, and geometric constraint is proposed to guide the network in generating keypoints with semantic consistency and regular spatial distribution. The experimental results and quantitative comparisons on the ShapeNet and KeypointNet datasets demonstrate that the proposed method achieves ordered, well-aligned, and robust keypoints generation for 3D point clouds. The source code of the proposed method is available at https://github.com/djzgroup/Keypoints.

Automatic and human level Graf's type identification for detecting developmental dysplasia of the hip

BACKGROUND

Developmental dysplasia of the hip (DDH) is a common congenital disorder that may lead to hip dislocation and requires surgical intervention if left untreated. Ultrasonography is the preferred method for DDH screening; however, the lack of experienced operators impedes its application in universal neonatal screening.

METHODS

We developed a deep neural network tool to automatically register the five keypoints that mark important anatomical structures of the hip and provide a reference for measuring alpha and beta angles following Graf's guidelines, which is an ultrasound classification system for DDH in infants. Two-dimensional (2D) ultrasonography images were obtained from 986 neonates aged 0-6 months. A total of 2406 images from 921 patients were labeled with ground truth keypoints by senior orthopedists.

RESULTS

Our model demonstrated precise keypoint localization. The mean absolute error was approximately 1 mm, and the derived alpha angle measurement had a correlation coefficient of R = 0.89 between the model and ground truth. The model achieved an area under the receiver operating characteristic curve of 0.937 and 0.974 for classifying alpha <60° (abnormal hip) and <50° (dysplastic hip), respectively. On average, the experts agreed with 96% of the inferenced images, and the model could generalize its prediction on newly collected images with a correlation coefficient higher than 0.85.

CONCLUSIONS

Precise localization and highly correlated performance metrics suggest that the model can be an efficient tool for assisting DDH diagnosis in clinical settings.

Performance of SURF and SIFT Keypoints for the Automated Differentiation of Abnormality in Chest Radiographs

In this work, automated abnormality detection using keypoint information from Speeded-Up Robust feature (SURF) and Scale Invariant Feature Transform (SIFT) descriptors in chest Radiographic (CR) images is investigated and compared. Computerized image analysis using artificial intelligence is crucial to detect subtle and non-specific alterations of Tuberculosis (TB). For this, the healthy and TB CRs are subjected to lung field segmentation. SURF and SIFT keypoints are extracted from the segmented lung images. Statistical features from keypoints, its scale and orientation are computed. Discrimination of TB from healthy is performed using SVM. Results show that the SURF and SIFT methods are able to extract local keypoint information in CRs. Linear SVM is found to perform better with precision of 88.9% and AUC of 91% in TB detection for combined features. Hence, the application of keypoint techniques is found to have clinical relevance in the automated screening of non-specific TB abnormalities using CRs.