Acceleration-based Kalman tracking for super-resolution ultrasound imaging in vivo

Super-resolution ultrasound can image microvascular structure and flow at sub-wave-diffraction resolution based on localising and tracking microbubbles. Currently, tracking microbubbles accurately under limited imaging frame rates and high microbubble concentrations remains a challenge, especially under the effect of cardiac pulsatility and in highly curved vessels. In this study, an acceleration-incorporated microbubble motion model is introduced into a Kalman tracking framework. The tracking performance was evaluated using simulated microvasculature with different microbubble motion parameters, concentrations and acquisition frame rates, and in vivo human breast tumour ultrasound datasets. The simulation results show that the acceleration-based method outperformed the non-acceleration-based method at different levels of acceleration and acquisition frame rates and achieved significant improvement in true positive rate (up to 11.3%), false negative rate (up to 13.2%). The proposed method can also reduce errors in vasculature reconstruction via the acceleration-based nonlinear interpolation, compared with linear interpolation (up to 16.7 μm). The tracking results from temporally downsampled low frame rate in vivo datasets from human breast tumours show that the proposed method has better microbubble tracking performance than the baseline method, if using results from the initial high frame data as reference. Finally, the acceleration estimated from tracking results also provides a spatial speed gradient map that may contain extra valuable diagnostic information

Dynamic Soil-Structure Interaction in Low-Rise Buildings from Seismic Records

This case study involves analysis of seismic records observation at two adjacent buildings, similarly constructed except that one is fitted with the base isolation system, to investigate the nature of soil-structure interaction mechanism involved. Altogether 19 earthquake records with maximum acceleration of over 10 cm/s2 are selected for the analyses. The south face of the building site slopes downward at an angle of about 20 degrees, which may contribute to topographical effect in wave propagation through the ground. Effects of the surface irregularity to the observed records are also discussed based on the interrelation between peak values of acceleration, velocity, spectral ordinate at 5% damping and Fourier spectral amplitudes. Inertial and kinematic interaction effects are also discussed based on the ratio of spectral amplitudes. Correlation analysis is subsequently carried out by obtaining coherency function and phase spectra. Results from coherency, phase lag, acceleration time history in limited frequency bands, and trends in particle motion orbits indicate that the free field motion at filled ground close to the sloping ground is out of phase building foundation (1F) motion at lower frequencies

Non-Rigid Groupwise Registration for Motion Estimation and Compensation in Compressed Sensing Reconstruc- tion of Breath-Hold Cardiac Cine MRI

Purpose: Compressed sensing methods with motion estimation and compensation techniques have been proposed for the reconstruction of accelerated dynamic MRI. However, artifacts that naturally arise in compressed sensing reconstruction procedures hinder the estimation of motion from reconstructed images, especially at high acceleration factors. This work introduces a robust groupwise non-rigid motion estimation technique applied to the compressed sensing reconstruction of dynamic cardiac cine MRI sequences. Theory and Methods: A spatio-temporal regularized, groupwise, non-rigid registration method based on a B-splines deformation model and a least squares metric is used to estimate and to compensate the movement of the heart in breath-hold cine acquisitions and to obtain a quasi-static sequence with highly sparse representation in temporally transformed domains. Results: Short axis in vivo datasets are used for validation, both original multi-coil as well as DICOM data. Fully sampled data were retrospectively undersampled with various acceleration factors and reconstructions were compared with the two well-known methods k-t FOCUSS and MASTeR. The proposed method achieves higher signal to error ratio and structure similarity index for medium to high acceleration factors. Conclusions: Reconstruction methods based on groupwise registration show higher quality recon- structions for cardiac cine images than the pairwise counterparts tested

A Motion Planning Processor on Reconfigurable Hardware

Motion planning algorithms enable us to find feasible paths for moving objects. These algorithms utilize feasibility checks to differentiate valid paths from invalid ones. Unfortunately, the computationally expensive nature of such checks reduces the effectiveness of motion planning algorithms. However, by using hardware acceleration to speed up the feasibility checks, we can greatly enhance the performance of the motion planning algorithms. Of course, such acceleration is not limited to feasibility checks; other components of motion planning algorithms can also be accelerated using specially designed hardware. A Field Programmable Gate Array (FPGA) is a great platform to support such an acceleration. An FPGA is a collection of digital gates which can be reprogrammed at run time, i.e., it can be used as a CPU that reconfigures itself for a given task. In this paper, we study the feasibility of an FPGA based motion planning processor and evaluate its performance. In order to leverage its highly parallel nature and its modular structure, our processor utilizes the probabilistic roadmap method at its core. The modularity enables us to replace the feasibility criteria with other ones. The reconfigurability lets us run our processor in different roles, such as a motion planning co-processor, an autonomous motion planning processor or dedicated collision detection chip. Our experiments show that such a processor is not only feasible but also can greatly increase the performance of current algorithms

The identification of a distributed parameter model for a flexible structure

A computational method is developed for the estimation of parameters in a distributed model for a flexible structure. The structure we consider (part of the RPL experiment) consists of a cantilevered beam with a thruster and linear accelerometer at the free end. The thruster is fed by a pressurized hose whose horizontal motion effects the transverse vibration of the beam. The Euler-Bernoulli theory is used to model the vibration of the beam and treat the hose-thruster assembly as a lumped or point mass-dashpot-spring system at the tip. Using measurements of linear acceleration at the tip, it is estimated that the parameters (mass, stiffness, damping) and a Voight-Kelvin viscoelastic structural damping parameter for the beam using a least squares fit to the data. Spline based approximations to the hybrid (coupled ordinary and partial differential equations) system are considered; theoretical convergence results and numerical studies with both simulation and actual experimental data obtained from the structure are presented and discussed

Spectral Study of Soil-Pile-Structure Interaction Based on Observed Data

Spectral analysis and system identification algorithm are used to analyze a set of acceleration response records obtained from a shaking table test. The method is based on the linear discrete time systems theory, and the soil-pile system can be represented as a linear filter of a finite order with time-varying coefficients. The recorded ground motion at the pile tip is the input, and the motion at the different level along the pile and the structure is the output of the filter. Knowing the input and output, the time varying parameters of the filter can be determined by using the system identification method. Once the filter parameters are known, the transfer function, and the kinematic interaction between the soil-pile-structure can be determined

Cosmic Ray Acceleration at Relativistic Shock Waves with a "Realistic" Magnetic Field Structure

The process of cosmic ray first-order Fermi acceleration at relativistic shock waves is studied with the method of Monte Carlo simulations. The simulations are based on numerical integration of particle equations of motion in a turbulent magnetic field near the shock. In comparison to earlier studies, a few "realistic" features of the magnetic field structure are included. The upstream field consists of a mean field component inclined at some angle to the shock normal with finite-amplitude sinusoidal perturbations imposed upon it. The perturbations are assumed to be static in the local plasma rest frame. Their flat or Kolmogorov spectra are constructed with randomly drawn wave vectors from a wide range $(k_{min}, k_{max})$. The downstream field structure is derived from the upstream one as compressed at the shock. We present particle spectra and angular distributions obtained at mildly relativistic sub- and superluminal shocks and also parallel shocks. We show that particle spectra diverge from a simple power-law, the exact shape of the spectrum depends on both the amplitude of the magnetic field perturbations and the wave power spectrum. Features such as spectrum hardening before the cut-off at oblique subluminal shocks and formation of power-law tails at superluminal ones are presented and discussed. At parallel shocks, the presence of finite-amplitude magnetic field perturbations leads to the formation of locally oblique field configurations at the shock and the respective magnetic field compressions. This results in the modification of the particle acceleration process, introducing some features present in oblique shocks, e.g., particle reflections from the shock. We demonstrate for parallel shocks a (nonmonotonic) variation of the particle spectral index with the turbulence amplitude.Comment: revised version (37 pages, 13 figures

Reuse of sludge from water treatment plant as a construction material / Mohammad Fadzli Tajon Aros

Although earthquakes have never caused any structural damage to Peninsula Malaysia, the consequences of even a moderate level of ground motion may be enormous because of the high concentration of population and commercial activities taking place in structures that have not been designed for seismic loads in the area. In order to design the structure to withstand the seismic loading, the initial important soil dynamic terms need to be analyzed. They are including the acceleration, and response spectra of the soil. Earthquake ground motions are usually predicted in two stages. In the first stage, an attenuation relationship is used to relate the earthquake magnitude, depth of epicenter, and location of earthquake source and study areas by using essential relationship based on adjusted relationship that is commonly used for Peninsular Malaysia. Attenuation relationship for Perai due to Sumatran Earthquake on December 2004 was used to determine the Peak Ground Acceleration (PGA) at bedrock. The result then was applied together with the NERA software to determine the Spectrum Response and Peak Surface Acceleration for the soil surface (PSA). Data collection included the search for the earthquake history data, strong ground motion data and soil data from different site location