267 research outputs found
Robust Kernel-based Feature Representation for 3D Point Cloud Analysis via Circular Graph Convolutional Network
Feature descriptors of point clouds are used in several applications, such as
registration and part segmentation of 3D point clouds. Learning discriminative
representations of local geometric features is unquestionably the most
important task for accurate point cloud analyses. However, it is challenging to
develop rotation or scale-invariant descriptors. Most previous studies have
either ignored rotations or empirically studied optimal scale parameters, which
hinders the applicability of the methods for real-world datasets. In this
paper, we present a new local feature description method that is robust to
rotation, density, and scale variations. Moreover, to improve representations
of the local descriptors, we propose a global aggregation method. First, we
place kernels aligned around each point in the normal direction. To avoid the
sign problem of the normal vector, we use a symmetric kernel point distribution
in the tangential plane. From each kernel point, we first projected the points
from the spatial space to the feature space, which is robust to multiple scales
and rotation, based on angles and distances. Subsequently, we perform graph
convolutions by considering local kernel point structures and long-range global
context, obtained by a global aggregation method. We experimented with our
proposed descriptors on benchmark datasets (i.e., ModelNet40 and ShapeNetPart)
to evaluate the performance of registration, classification, and part
segmentation on 3D point clouds. Our method showed superior performances when
compared to the state-of-the-art methods by reducing 70 of the rotation and
translation errors in the registration task. Our method also showed comparable
performance in the classification and part-segmentation tasks with simple and
low-dimensional architectures.Comment: 10 pages, 9 figure
Tooth Instance Segmentation from Cone-Beam CT Images through Point-based Detection and Gaussian Disentanglement
Individual tooth segmentation and identification from cone-beam computed
tomography images are preoperative prerequisites for orthodontic treatments.
Instance segmentation methods using convolutional neural networks have
demonstrated ground-breaking results on individual tooth segmentation tasks,
and are used in various medical imaging applications. While point-based
detection networks achieve superior results on dental images, it is still a
challenging task to distinguish adjacent teeth because of their similar
topologies and proximate nature. In this study, we propose a point-based tooth
localization network that effectively disentangles each individual tooth based
on a Gaussian disentanglement objective function. The proposed network first
performs heatmap regression accompanied by box regression for all the
anatomical teeth. A novel Gaussian disentanglement penalty is employed by
minimizing the sum of the pixel-wise multiplication of the heatmaps for all
adjacent teeth pairs. Subsequently, individual tooth segmentation is performed
by converting a pixel-wise labeling task to a distance map regression task to
minimize false positives in adjacent regions of the teeth. Experimental results
demonstrate that the proposed algorithm outperforms state-of-the-art approaches
by increasing the average precision of detection by 9.1%, which results in a
high performance in terms of individual tooth segmentation. The primary
significance of the proposed method is two-fold: 1) the introduction of a
point-based tooth detection framework that does not require additional
classification and 2) the design of a novel loss function that effectively
separates Gaussian distributions based on heatmap responses in the point-based
detection framework.Comment: 11 pages, 7 figure
Volumetric Lung Nodule Segmentation using Adaptive ROI with Multi-View Residual Learning
Accurate quantification of pulmonary nodules can greatly assist the early
diagnosis of lung cancer, which can enhance patient survival possibilities. A
number of nodule segmentation techniques have been proposed, however, all of
the existing techniques rely on radiologist 3-D volume of interest (VOI) input
or use the constant region of interest (ROI) and only investigate the presence
of nodule voxels within the given VOI. Such approaches restrain the solutions
to investigate the nodule presence outside the given VOI and also include the
redundant structures into VOI, which may lead to inaccurate nodule
segmentation. In this work, a novel semi-automated approach for 3-D
segmentation of nodule in volumetric computerized tomography (CT) lung scans
has been proposed. The proposed technique can be segregated into two stages, at
the first stage, it takes a 2-D ROI containing the nodule as input and it
performs patch-wise investigation along the axial axis with a novel adaptive
ROI strategy. The adaptive ROI algorithm enables the solution to dynamically
select the ROI for the surrounding slices to investigate the presence of nodule
using deep residual U-Net architecture. The first stage provides the initial
estimation of nodule which is further utilized to extract the VOI. At the
second stage, the extracted VOI is further investigated along the coronal and
sagittal axis with two different networks and finally, all the estimated masks
are fed into the consensus module to produce the final volumetric segmentation
of nodule. The proposed approach has been rigorously evaluated on the LIDC
dataset, which is the largest publicly available dataset. The result suggests
that the approach is significantly robust and accurate as compared to the
previous state of the art techniques.Comment: The manuscript is currently under review and copyright shall be
transferred to the publisher upon acceptanc
Parallelized Seeded Region Growing Using CUDA
This paper presents a novel method for parallelizing the seeded region growing (SRG) algorithm using Compute Unified Device Architecture (CUDA) technology, with intention to overcome the theoretical weakness of SRG algorithm of its computation time being directly proportional to the size of a segmented region. The segmentation performance of the proposed CUDA-based SRG is compared with SRG implementations on single-core CPUs, quad-core CPUs, and shader language programming, using synthetic datasets and 20 body CT scans. Based on the experimental results, the CUDA-based SRG outperforms the other three implementations, advocating that it can substantially assist the segmentation during massive CT screening tests
MEDS-Net: Self-Distilled Multi-Encoders Network with Bi-Direction Maximum Intensity projections for Lung Nodule Detection
In this study, we propose a lung nodule detection scheme which fully
incorporates the clinic workflow of radiologists. Particularly, we exploit
Bi-Directional Maximum intensity projection (MIP) images of various thicknesses
(i.e., 3, 5 and 10mm) along with a 3D patch of CT scan, consisting of 10
adjacent slices to feed into self-distillation-based Multi-Encoders Network
(MEDS-Net). The proposed architecture first condenses 3D patch input to three
channels by using a dense block which consists of dense units which effectively
examine the nodule presence from 2D axial slices. This condensed information,
along with the forward and backward MIP images, is fed to three different
encoders to learn the most meaningful representation, which is forwarded into
the decoded block at various levels. At the decoder block, we employ a
self-distillation mechanism by connecting the distillation block, which
contains five lung nodule detectors. It helps to expedite the convergence and
improves the learning ability of the proposed architecture. Finally, the
proposed scheme reduces the false positives by complementing the main detector
with auxiliary detectors. The proposed scheme has been rigorously evaluated on
888 scans of LUNA16 dataset and obtained a CPM score of 93.6\%. The results
demonstrate that incorporating of bi-direction MIP images enables MEDS-Net to
effectively distinguish nodules from surroundings which help to achieve the
sensitivity of 91.5% and 92.8% with false positives rate of 0.25 and 0.5 per
scan, respectively
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