62,138 research outputs found
Learning Generalized Non-Rigid Multimodal Biomedical Image Registration from Generic Point Set Data
Free Point Transformer (FPT) has been proposed as a data-driven, non-rigid
point set registration approach using deep neural networks. As FPT does not
assume constraints based on point vicinity or correspondence, it may be trained
simply and in a flexible manner by minimizing an unsupervised loss based on the
Chamfer Distance. This makes FPT amenable to real-world medical imaging
applications where ground-truth deformations may be infeasible to obtain, or in
scenarios where only a varying degree of completeness in the point sets to be
aligned is available. To test the limit of the correspondence finding ability
of FPT and its dependency on training data sets, this work explores the
generalizability of the FPT from well-curated non-medical data sets to medical
imaging data sets. First, we train FPT on the ModelNet40 dataset to demonstrate
its effectiveness and the superior registration performance of FPT over
iterative and learning-based point set registration methods. Second, we
demonstrate superior performance in rigid and non-rigid registration and
robustness to missing data. Last, we highlight the interesting generalizability
of the ModelNet-trained FPT by registering reconstructed freehand ultrasound
scans of the spine and generic spine models without additional training,
whereby the average difference to the ground truth curvatures is 1.3 degrees,
across 13 patients.Comment: Accepted to ASMUS 2022 Workshop at MICCA
On a registration-based approach to sensor network localization
We consider a registration-based approach for localizing sensor networks from
range measurements. This is based on the assumption that one can find
overlapping cliques spanning the network. That is, for each sensor, one can
identify geometric neighbors for which all inter-sensor ranges are known. Such
cliques can be efficiently localized using multidimensional scaling. However,
since each clique is localized in some local coordinate system, we are required
to register them in a global coordinate system. In other words, our approach is
based on transforming the localization problem into a problem of registration.
In this context, the main contributions are as follows. First, we describe an
efficient method for partitioning the network into overlapping cliques. Second,
we study the problem of registering the localized cliques, and formulate a
necessary rigidity condition for uniquely recovering the global sensor
coordinates. In particular, we present a method for efficiently testing
rigidity, and a proposal for augmenting the partitioned network to enforce
rigidity. A recently proposed semidefinite relaxation of global registration is
used for registering the cliques. We present simulation results on random and
structured sensor networks to demonstrate that the proposed method compares
favourably with state-of-the-art methods in terms of run-time, accuracy, and
scalability
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