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Contains fulltext : 88176.pdf (Publisher’s version ) (Open Access) In this study, first we propose a biplane strain imaging method using a commercial ultrasound system, yielding estimation of the strain in three orthogonal directions. Secondly, an animal model of a child's heart was introduced that is suitable to simulate congenital heart disease and was used to test the method in vivo. The proposed approach can serve as a framework to monitor the development of cardiac hypertrophy and fibrosis. A 2D strain estimation technique using radio frequency (RF) ultrasound data was applied. Biplane image acquisition was performed at a relatively low frame rate (

Item does not contain fulltext Much research is being conducted on position-sensitive scintillation detectors for medical imaging, particularly for emission tomography. Monte Carlo simulations play an essential role in many of these research activities. As the scintillation process, the transport of scintillation photons through the crystal(s), and the conversion of these photons into electronic signals each have a major influence on the detector performance; all of these processes may need to be incorporated in the model to obtain accurate results. In this work the optical and scintillation models of the GEANT4 simulation toolkit are validated by comparing simulations and measurements on monolithic scintillator detectors for high-resolution positron emission tomography (PET). We have furthermore made the GEANT4 optical models available within the user-friendly GATE simulation platform (as of version 3.0). It is shown how the necessary optical input parameters can be determined with sufficient accuracy. The results show that the optical physics models of GATE/GEANT4 enable accurate prediction of the spatial and energy resolution of monolithic scintillator PET detectors.

Contains fulltext : 88548.pdf (Publisher’s version ) (Closed access) Ultrasound strain imaging is used to measure local tissue deformations. Usually, only strains along the ultrasound beam are estimated, because those estimates are most precise, due to the availability of phase information. For estimating strain in other directions we propose to steer the ultrasound beam at an angle, which allows estimating different projections of the 2D strain tensor, while phase information remains available. This study investigates beam steering at maximally three different angles to determine the full 2D strain tensor. The method was tested on simulated and experimental data of an inclusion phantom and a vessel phantom. The combination of data from a non-steered acquisition and acquisitions at a large positive and an equally large but negative steering angle enabled the most precise estimation of the strain components. The method outperforms conventional methods that do not use beam steering.