309 research outputs found
Global Ultrasound Elastography Using Convolutional Neural Network
Displacement estimation is very important in ultrasound elastography and
failing to estimate displacement correctly results in failure in generating
strain images. As conventional ultrasound elastography techniques suffer from
decorrelation noise, they are prone to fail in estimating displacement between
echo signals obtained during tissue distortions. This study proposes a novel
elastography technique which addresses the decorrelation in estimating
displacement field. We call our method GLUENet (GLobal Ultrasound Elastography
Network) which uses deep Convolutional Neural Network (CNN) to get a coarse
time-delay estimation between two ultrasound images. This displacement is later
used for formulating a nonlinear cost function which incorporates similarity of
RF data intensity and prior information of estimated displacement. By
optimizing this cost function, we calculate the finer displacement by
exploiting all the information of all the samples of RF data simultaneously.
The Contrast to Noise Ratio (CNR) and Signal to Noise Ratio (SNR) of the strain
images from our technique is very much close to that of strain images from
GLUE. While most elastography algorithms are sensitive to parameter tuning, our
robust algorithm is substantially less sensitive to parameter tuning.Comment: 4 pages, 4 figures; added acknowledgment section, submission type
late
Real-time quantitative sonoelastography in an ultrasound research system
Quantitative Sono-Elastographie ist eine neue Technologie für die Ultraschall Bildgebung,
die Radiologen maligne Tumoren ohne Risiko der strahlungsinduzierten Krebs
(d.h. Mammographie) zu erfassen können. Aufgrund gefunden Rechenkomplexität
in der aktuellen Algorithmen, Implementierung von Echtzeit-Anwendungen, die Prüfungsverfahren
profitieren wurde jedoch noch nicht berichtet. Zusätzlich, aktuelle
Schätzer für die Darstellung eine Elastizität Bilder vorhanden Artefakte der hohen
Schätzung Varianz, die die Techniker in die Gegenwart steifer Massen irreführen könnten
und zwar, falsch-positive Diagnose zu erzeugen.
In dieser Arbeit wird eine GPU-basierte Elastographie-System entwickelt und an
einem Forschungsultraschallgeräten implementiert. Quantitative Elastizität in Echtzeit
bei 2 FPS mit einer Verbesserung Rechenzeitfaktor aus 26 wird gezeigt. Validierung der
Systemgenauigkeit Anzeige wurde, auf Gelatinebasis Gewebe Phantome durchgeführt.,
waren niedrige Vorspannung der Elastizitätswerte berichtet wurde (4,7 %) bei geringe
Anregungsfrequenzen nachahmt. Ausserdem wird eine neue Elastizität Schätzer auf
quantitative Sono-Elastographie basiert eingeführt. Ein lineares Problem wurde entlang
der seitlichen Abmessung modelliert und eine Regularisierung Methode wurde
implementieren. Elastizität Bilder mit niedriger Vorspannung wurde darstellen (1,48
%) sowie seine Leistung in einer Brust kalibrierte Phantom mit verbesserter CNR (47,3
dB) im Vergleich mit anderen Schätzer ausgewertet sowie die Verringerung Seiten Artefakte
bereits erwähnt in der Literatur (PD: 22,7 dB, 1DH 28,7 dB) gefunden. Diese
zwei Beitrag profitieren, die Umsetzung und Entwicklung weiterer Elastographie Techniken,
die eine verbesserte Qualität der Elastizität Bilder liefern könnten und somit
eine verbesserte Genauigkeit der Diagnose.Quantitative sonoelastography is an alternative technology for ultrasound imaging
that helps radiologist to diagnose malignant tumors with no risk of radiation-induced
cancer (i.e. mammography). However, due to the high computational complexity
found in the current algorithms, implementation of real-time systems that could benefit
examination procedures has not been yet reported. Additionally, elasticity maps
depicted from current estimators feature artifacts of high estimation variance that
could mislead the technician into the presence of stiffer masses, generating false positive
diagnosis.
In this thesis, a GPU-based elastography system was designed and implemented on
a research ultrasound equipment, displaying quantitative elasticity in real-time at 2
FPS with an improvement computational time factor of 26. Validation of the system
accuracy was conducted on gelatin-based tissue mimicking phantoms, where low bias
of elasticity values were reported (4.7%) at low excitation frequencies. Additionally,
a new elasticity estimator based on quantitative sonoelastography was developed. A
linear problem was modeled from the acquired sonolastography data along the lateral
dimension and a regularization method was implemented. The resulting elasticity
images presented low bias (1.48%), enhanced CNR and reduced lateral artifacts when
evaluating the algorithm’s performance in a breast calibrated phantom and comparing
it with other estimators found in the literature. These two contribution benefit the
implementation and development of further elastography techniques that could provide
enhanced quality of elasticity images and thus, improved accuracy of diagnosis.Tesi
Fast Approximate Time-Delay Estimation in Ultrasound Elastography Using Principal Component Analysis
Time delay estimation (TDE) is a critical and challenging step in all
ultrasound elastography methods. A growing number of TDE techniques require an
approximate but robust and fast method to initialize solving for TDE. Herein,
we present a fast method for calculating an approximate TDE between two radio
frequency (RF) frames of ultrasound. Although this approximate TDE can be
useful for several algorithms, we focus on GLobal Ultrasound Elastography
(GLUE), which currently relies on Dynamic Programming (DP) to provide this
approximate TDE. We exploit Principal Component Analysis (PCA) to find the
general modes of deformation in quasi-static elastography, and therefore call
our method PCA-GLUE. PCA-GLUE is a data-driven approach that learns a set of
TDE principal components from a training database in real experiments. In the
test phase, TDE is approximated as a weighted sum of these principal
components. Our algorithm robustly estimates the weights from sparse feature
matches, then passes the resulting displacement field to GLUE as initial
estimates to perform a more accurate displacement estimation. PCA-GLUE is more
than ten times faster than DP in estimation of the initial displacement field
and yields similar results.Comment: Accepted to be Published in 2019, 41th Annual International
Conference of the IEEE Engineering in Medicine and Biology Society (EMBC),
Berlin, German
Exploiting Mechanics-Based Priors for Lateral Displacement Estimation in Ultrasound Elastography
Tracking the displacement between the pre- and post-deformed radio-frequency
(RF) frames is a pivotal step of ultrasound elastography, which depicts tissue
mechanical properties to identify pathologies. Due to ultrasound's poor ability
to capture information pertaining to the lateral direction, the existing
displacement estimation techniques fail to generate an accurate lateral
displacement or strain map. The attempts made in the literature to mitigate
this well-known issue suffer from one of the following limitations: 1) Sampling
size is substantially increased, rendering the method computationally and
memory expensive. 2) The lateral displacement estimation entirely depends on
the axial one, ignoring data fidelity and creating large errors. This paper
proposes exploiting the effective Poisson's ratio (EPR)-based mechanical
correspondence between the axial and lateral strains along with the RF data
fidelity and displacement continuity to improve the lateral displacement and
strain estimation accuracies. We call our techniques MechSOUL
(Mechanically-constrained Second-Order Ultrasound eLastography) and L1-MechSOUL
(L1-norm-based MechSOUL), which optimize L2- and L1-norm-based penalty
functions, respectively. Extensive validation experiments with simulated,
phantom, and in vivo datasets demonstrate that MechSOUL and L1-MechSOUL's
lateral strain and EPR estimation abilities are substantially superior to those
of the recently-published elastography techniques. We have published the MATLAB
codes of MechSOUL and L1-MechSOUL at http://code.sonography.ai.Comment: Link to the Supplemental Video:
https://drive.google.com/file/d/1uOmt-T4i9MwR98jUoMsu-eOhQ2mgjrBd/view?usp=sharin
Infusing known operators in convolutional neural networks for lateral strain imaging in ultrasound elastography
Convolutional Neural Networks (CNN) have been employed for displacement
estimation in ultrasound elastography (USE). High-quality axial strains
(derivative of the axial displacement in the axial direction) can be estimated
by the proposed networks. In contrast to axial strain, lateral strain, which is
highly required in Poisson's ratio imaging and elasticity reconstruction, has a
poor quality. The main causes include low sampling frequency, limited motion,
and lack of phase information in the lateral direction. Recently, physically
inspired constraint in unsupervised regularized elastography (PICTURE) has been
proposed. This method took into account the range of the feasible lateral
strain defined by the rules of physics of motion and employed a regularization
strategy to improve the lateral strains. Despite the substantial improvement,
the regularization was only applied during the training; hence it did not
guarantee during the test that the lateral strain is within the feasible range.
Furthermore, only the feasible range was employed, other constraints such as
incompressibility were not investigated. In this paper, we address these two
issues and propose kPICTURE in which two iterative algorithms were infused into
the network architecture in the form of known operators to ensure the lateral
strain is within the feasible range and impose incompressibility during the
test phase.Comment: Accepted in MICCAI 202
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