22 research outputs found
Analytical Estimation of Beamforming Speed-of-Sound Using Transmission Geometry
Most ultrasound imaging techniques necessitate the fundamental step of
converting temporal signals received from transducer elements into a spatial
echogenecity map. This beamforming (BF) step requires the knowledge of
speed-of-sound (SoS) value in the imaged medium. An incorrect assumption of BF
SoS leads to aberration artifacts, not only deteriorating the quality and
resolution of conventional brightness mode (B-mode) images, hence limiting
their clinical usability, but also impairing other ultrasound modalities such
as elastography and spatial SoS reconstructions, which rely on faithfully
beamformed images as their input. In this work, we propose an analytical method
for estimating BF SoS. We show that pixel-wise relative shifts between frames
beamformed with an assumed SoS is a function of geometric disparities of the
transmission paths and the error in such SoS assumption. Using this relation,
we devise an analytical model, the closed form solution of which yields the
difference between the assumed and the true SoS in the medium. Based on this,
we correct the BF SoS, which can also be applied iteratively. Both in
simulations and experiments, lateral B-mode resolution is shown to be improved
by 25% compared to that with an initial SoS assumption error of 3.3%
(50 m/s), while localization artifacts from beamforming are also corrected.
After 5 iterations, our method achieves BF SoS errors of under 0.6 m/s in
simulations and under 1 m/s in experimental phantom data. Residual time-delay
errors in beamforming 32 numerical phantoms are shown to reduce down to 0.07
s, with average improvements of up to 21 folds compared to initial
inaccurate assumptions. We additionally show the utility of the proposed method
in imaging local SoS maps, where using our correction method reduces
reconstruction root-mean-square errors substantially, down to their lower-bound
with actual BF SoS
Learning the Imaging Model of Speed-of-Sound Reconstruction via a Convolutional Formulation
Speed-of-sound (SoS) is an emerging ultrasound contrast modality, where
pulse-echo techniques using conventional transducers offer multiple benefits.
For estimating tissue SoS distributions, spatial domain reconstruction from
relative speckle shifts between different beamforming sequences is a promising
approach. This operates based on a forward model that relates the sought local
values of SoS to observed speckle shifts, for which the associated image
reconstruction inverse problem is solved. The reconstruction accuracy thus
highly depends on the hand-crafted forward imaging model. In this work, we
propose to learn the SoS imaging model based on data. We introduce a
convolutional formulation of the pulse-echo SoS imaging problem such that the
entire field-of-view requires a single unified kernel, the learning of which is
then tractable and robust. We present least-squares estimation of such
convolutional kernel, which can further be constrained and regularized for
numerical stability. In experiments, we show that a forward model learned from
k-Wave simulations improves the median contrast of SoS reconstructions by 63%,
compared to a conventional hand-crafted line-based wave-path model. This
simulation-learned model generalizes successfully to acquired phantom data,
nearly doubling the SoS contrast compared to the conventional hand-crafted
alternative. We demonstrate equipment-specific and small-data regime
feasibility by learning a forward model from a single phantom image, where our
learned model quadruples the SoS contrast compared to the conventional
hand-crafted model. On in-vivo data, the simulation- and phantom-learned models
respectively exhibit impressive 7 and 10 folds contrast improvements over the
conventional model
Reduced order design space analysis of for ramjet engines with data mining techniques
info:eu-repo/semantics/publishe
Platelet-rich plasma decreases fibroblastic activity and woven bone formation with no significant immunohistochemical effect on long-bone healing: An experimental animal study with radiological outcomes
Purpose: This study aimed to analyze the immunohistochemical effect of platelet-rich plasma (PRP) on healing of long-bone fractures in terms of bone morphogenetic protein-2 (BMP-2), vascular endothelial growth factor (VEGF), the Ki-67 proliferation index, and radiological and histological analyses.
Methods: Sixteen adult rabbits, whose right femoral diaphysis was fractured and fixed with Kirschner wires, were randomly divided into two groups, control and PRP (groups A and B, respectively). PRP was given to group B at 1 week postoperatively, and all animals were euthanized after 12 weeks. Radiographic evaluations were performed periodically. Cortical callus formation, chondroid and woven bone area percentages, osteoblastic and fibroblastic activities, and mature bone formation were examined. The depths of BMP-2 and VEGF staining were measured. The Ki-67 proliferation index was also calculated.
Results: The mean radiological union score of group B was significantly higher than that of group A. There were also statistically significant differences between groups A and B in terms of cortical callus formation, woven bone area percentage, fibroblast proliferation, and mature bone formation. Group B had significantly more cortical callus and mature bone formation with less woven bone and fibroblast proliferation. Immunohistochemical analysis revealed no statistically significant difference between the groups in terms of BMP-2 and VEGF staining and the Ki-67 index.
Conclusions: PRP had no effect on BMP-2 or VEGF levels with no increase in the Ki-67 proliferation index, although its application had a positive effect on bone healing by increasing callus and mature bone formation with decreased woven bone and fibroblast proliferation
Visual clarity of irrigants used during flexible ureterorenoscopy: an in vitro comparison
WOS:000615231400016PubMed: 33552578Introduction Saline solution is the standard irrigant used during ureteroscopy. However, there is an opinion that water has better visual clarity. We aimed to compare the visual clarities of saline, water, and 5% mannitol as an irrigant during ureteroscopy. Material and methods An in vitro model consisting of an irrigant-filled container and a fiberoptic flexible ureteroscope was designed. A 1951 USAF Resolution Test Target and color checker within irrigants were used to evaluate the clarity of vision. The visual clarity was compared for 0.9% saline, distilled water and 5% mannitol solution with screen resolution and color contrast. The tests were repeated after adding human blood (2/400 ml) and contrast (20/400 ml) to the irrigants. Results There was no significant difference in resolution values of three plain irrigants at a distance of 10 mm. However, when blood was added to the irrigants, a better resolution of 29.3% for water and 20.6% for mannitol was achieved compared to saline. At 20 mm of distance, it was observed that the difference was more pronounced in irrigants with blood. Water and mannitol had 55.6% and 37.1% better resolution than saline, respectively. in the color reproduction test, there was no significant difference in the three plain irrigants, however, water had better color contrast compared to the others. Conclusions Water and 5% mannitol did not provide a significant image clarity advantage compared to saline. However, when blood was added to the irrigants, water provided significantly better visual clarity compared to saline. The use of water during various clinical scenarios in flexible ureteroscopy should be further investigated
The Role of Apelin 13 in Progression of Chronic Kidney Disease
Introduction. Apelin is an adipokine secreted by the adipose tissue and by the endothelial cells in various parts of the body. Apelin is also expressed by the glomerular arteriolar rectus and glomerular capillary cells. We evaluated the relationship between the initial serum levels of apelin 13 with the trend of glomerular filtration rate (GFR) during a 1-year follow-up of patients with chronic kidney disease (CKD)
Fulvestrant efficacy in artificial menopausal hormone receptor positive and HER 2 negative metastatic breast cancer patients under 50 years old.
Triglyceride Response to Oral Glucose Load: Is it Exaggerated in Metabolic Syndrome?
Objective: Metabolic syndrome (MetS) is a cluster of cardiometabolic risk factors related to insulin resistance. Data show that triglyceride (TG) levels following an oral glucose tolerance test (OGTT) are higher among obese and insulin-resistant cases associated with metabolic risk factors. In this study, we aimed to assess whether an exaggerated TG response was present in cases with MetS who had undergone OGTT