259 research outputs found
Deep Coherence Learning: An Unsupervised Deep Beamformer for High Quality Single Plane Wave Imaging in Medical Ultrasound
Plane wave imaging (PWI) in medical ultrasound is becoming an important
reconstruction method with high frame rates and new clinical applications.
Recently, single PWI based on deep learning (DL) has been studied to overcome
lowered frame rates of traditional PWI with multiple PW transmissions. However,
due to the lack of appropriate ground truth images, DL-based PWI still remains
challenging for performance improvements. To address this issue, in this paper,
we propose a new unsupervised learning approach, i.e., deep coherence learning
(DCL)-based DL beamformer (DL-DCL), for high-quality single PWI. In DL-DCL, the
DL network is trained to predict highly correlated signals with a unique loss
function from a set of PW data, and the trained DL model encourages
high-quality PWI from low-quality single PW data. In addition, the DL-DCL
framework based on complex baseband signals enables a universal beamformer. To
assess the performance of DL-DCL, simulation, phantom and in vivo studies were
conducted with public datasets, and it was compared with traditional
beamformers (i.e., DAS with 75-PWs and DMAS with 1-PW) and other DL-based
methods (i.e., supervised learning approach with 1-PW and generative
adversarial network (GAN) with 1-PW). From the experiments, the proposed DL-DCL
showed comparable results with DMAS with 1-PW and DAS with 75-PWs in spatial
resolution, and it outperformed all comparison methods in contrast resolution.
These results demonstrated that the proposed unsupervised learning approach can
address the inherent limitations of traditional PWIs based on DL, and it also
showed great potential in clinical settings with minimal artifacts
A degree reduction method for an efficient QUBO formulation for the graph coloring problem
We introduce a new degree reduction method for homogeneous symmetric
polynomials on binary variables that generalizes the conventional degree
reduction methods on monomials introduced by Freedman and Ishikawa. We also
design an degree reduction algorithm for general polynomials on binary
variables, simulated on the graph coloring problem for random graphs, and
compared the results with the conventional methods. The simulated results show
that our new method produces reduced quadratic polynomials that contains less
variables than the reduced quadratic polynomials produced by the conventional
methods
TRAO Survey of Nearby Filamentary Molecular clouds, the Universal Nursery of Stars (TRAO FUNS) I. Dynamics and Chemistry of L1478 in the California Molecular Cloud
"TRAO FUNS" is a project to survey Gould Belt's clouds in molecular lines.
This paper presents its first results on the central region of the California
molecular cloud, L1478. We performed On-The-Fly mapping observations using the
Taedeok Radio Astronomy Observatory (TRAO) 14m single dish telescope equipped
with a 16 multi-beam array covering 1.0 square degree area of this region
using CO (1-0) mainly tracing low density cloud and about 460 square
arcminute area using NH (1-0) mainly tracing dense cores. CS (2-1)
and SO were also used simultaneously to map 440 square
arcminute area of this region. We identified 10 filaments by applying the
dendrogram technique to the CO data-cube and 8 dense NH
cores by using {\sc FellWalker}. Basic physical properties of filaments such as
mass, length, width, velocity field, and velocity dispersion are derived. It is
found that L1478 consists of several filaments with slightly different
velocities. Especially the filaments which are supercritical are found to
contain dense cores detected in NH. Comparison of non-thermal
velocity dispersions derived from CO and NH for the
filaments and dense cores indicates that some of dense cores share similar
kinematics with those of the surrounding filaments while several dense cores
have different kinematics with those of their filaments. This suggests that the
formation mechanism of dense cores and filaments can be different in individual
filaments depending on their morphologies and environments.Comment: 25 pages, 15 figures, accepted for publication in Ap
Deformable Graph Transformer
Transformer-based models have recently shown success in representation
learning on graph-structured data beyond natural language processing and
computer vision. However, the success is limited to small-scale graphs due to
the drawbacks of full dot-product attention on graphs such as the quadratic
complexity with respect to the number of nodes and message aggregation from
enormous irrelevant nodes. To address these issues, we propose Deformable Graph
Transformer (DGT) that performs sparse attention via dynamically sampled
relevant nodes for efficiently handling large-scale graphs with a linear
complexity in the number of nodes. Specifically, our framework first constructs
multiple node sequences with various criteria to consider both structural and
semantic proximity. Then, combining with our learnable Katz Positional
Encodings, the sparse attention is applied to the node sequences for learning
node representations with a significantly reduced computational cost. Extensive
experiments demonstrate that our DGT achieves state-of-the-art performance on 7
graph benchmark datasets with 2.5 - 449 times less computational cost compared
to transformer-based graph models with full attention.Comment: 16 pages, 3 figure
Arc-to-line frame registration method for ultrasound and photoacoustic image-guided intraoperative robot-assisted laparoscopic prostatectomy
Purpose: To achieve effective robot-assisted laparoscopic prostatectomy, the
integration of transrectal ultrasound (TRUS) imaging system which is the most
widely used imaging modelity in prostate imaging is essential. However, manual
manipulation of the ultrasound transducer during the procedure will
significantly interfere with the surgery. Therefore, we propose an image
co-registration algorithm based on a photoacoustic marker method, where the
ultrasound / photoacoustic (US/PA) images can be registered to the endoscopic
camera images to ultimately enable the TRUS transducer to automatically track
the surgical instrument Methods: An optimization-based algorithm is proposed to
co-register the images from the two different imaging modalities. The
principles of light propagation and an uncertainty in PM detection were assumed
in this algorithm to improve the stability and accuracy of the algorithm. The
algorithm is validated using the previously developed US/PA image-guided system
with a da Vinci surgical robot. Results: The target-registration-error (TRE) is
measured to evaluate the proposed algorithm. In both simulation and
experimental demonstration, the proposed algorithm achieved a sub-centimeter
accuracy which is acceptable in practical clinics. The result is also
comparable with our previous approach, and the proposed method can be
implemented with a normal white light stereo camera and doesn't require highly
accurate localization of the PM. Conclusion: The proposed frame registration
algorithm enabled a simple yet efficient integration of commercial US/PA
imaging system into laparoscopic surgical setting by leveraging the
characteristic properties of acoustic wave propagation and laser excitation,
contributing to automated US/PA image-guided surgical intervention
applications.Comment: 12 pages, 9 figure
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