Search results for "Physics::Medical Physics"
showing 10 items of 188 documents
Monte Carlo Application in Brachytherapy Dosimetry
2009
This paper devoted to Monte-Carlo Applications in BT Dosimetry is organized in four parts: 1. Motivation of the use of Monte Carlo in brachytherapy 2. The use of Monte Carlo to obtain dose distribution around brachytherapy sources 3. Experimental dosimetry versus Monte Carlo 4. Others Monte Carlo applications in brachytherapy
Improving light propagation Monte Carlo simulations with accurate 3D modeling of skin tissue
2008
In this paper, we present a 3D light propagation model to simulate multispectral reflectance images of large skin surface areas. In particular, we aim to simulate more accurately the effects of various physiological properties of the skin in the case of subcutaneous vein imaging compared to existing models. Our method combines a Monte Carlo light propagation model, a realistic three-dimensional model of the skin using parametric surfaces and a vision system for data acquisition. We describe our model in detail, present results from the Monte Carlo modeling and compare our results with those obtained with a well established Monte Carlo model and with real skin reflectance images.
Mammographic images segmentation based on chaotic map clustering algorithm
2013
Background: This work investigates the applicability of a novel clustering approach to the segmentation of mammographic digital images. The chaotic map clustering algorithm is used to group together similar subsets of image pixels resulting in a medically meaningful partition of the mammography. Methods: The image is divided into pixels subsets characterized by a set of conveniently chosen features and each of the corresponding points in the feature space is associated to a map. A mutual coupling strength between the maps depending on the associated distance between feature space points is subsequently introduced. On the system of maps, the simulated evolution through chaotic dynamics leads…
Nanorod orientation control by swift heavy ion irradiation
2022
Highly energetic ions have been previously used to modify the shape of metal nanoparticles embedded in an insulating matrix. In this work, we demonstrate that under suitable conditions, energetic ions can be used not only for shape modification but also for manipulation of nanorod orientation. This observation is made by imaging the same nanorod before and after swift heavy ion irradiation using a transmission electron microscope. Atomistic simulations reveal a complex mechanism of nanorod re-orientation by an incremental change in its shape from a rod to a spheroid and further back into a rod aligned with the beam. Highly energetic ions have been previously used to modify the shape of meta…
Continuous-Variable Tomography of Solitary Electrons
2019
A method for characterising the wave-function of freely-propagating particles would provide a useful tool for developing quantum-information technologies with single electronic excitations. Previous continuous-variable quantum tomography techniques developed to analyse electronic excitations in the energy-time domain have been limited to energies close to the Fermi level. We show that a wide-band tomography of single-particle distributions is possible using energy-time filtering and that the Wigner representation of the mixed-state density matrix can be reconstructed for solitary electrons emitted by an on-demand single-electron source. These are highly localised distributions, isolated fro…
Self-similar focusing with generalized devil's lenses
2011
[EN] We introduce the generalized devil's lenses (GDLs) as a new family of diffractive kinoform lenses whose structure is based on the generalized Cantor set. The focusing properties of different members of this family are analyzed. It is shown that under plane wave illumination the GDLs give a single main focus surrounded by many subsidiary foci. It is shown that the total number of subsidiary foci is higher than the number of foci corresponding to conventional devil's lenses; however, the self-similar behavior of the axial irradiance is preserved to some extent. (C) 2011 Optical Society of America
Fourier optical approach to the extraction of morphological parameters from the diffraction pattern of biological cells.
1978
A new procedure for fast quantitative extraction of cell parameters from diffraction patterns was deduced from model calculations and applied to cervical gynecological material. Based on radial scans of the diffraction pattern, the technique permits simultaneous determination of the nuclear and cytoplasmic diameters by Fourier analysis of the radial scanning signals after compensation for the intensity falloff by an amplification proportional to the third power of the radial position in the diffraction plane. Illustrative examples of measurements on exfoliated cells of different types are presented.
Shear banding mechanism of plastic deformation in LiF irradiated with swift heavy ions
2012
The effect of ion irradiation on the behavior of plastic deformation at micro- and nanoindentation on (001) face of LiF has been investigated. The irradiation was performed using heavy ions (U, Au, Ti and S) with energy in the range from 3 MeV to 2 GeV at fluences up to 5x1013 ions/cm2. In non-irradiated LiF, the indentation produces dislocation gliding on the {110} planes along the and directions. At high fluence irradiation, the resource of the dislocation slip along the preferable directions becomes exhausted due to immobilization of dislocations by radiation defects and their aggregates. The present study demonstrates the change of the mechanism of plastic deformation from homogenous di…
Monte Carlo simulation of energy absorbed in phenolic ESR dosimeters added with gadolinium exposed to thermal, epithermal and fast neutrons
2017
Abstract In this work analyses of the energy released per unit mass in phenolic compound exposed to neutron beams were performed with the aim of predicting the increase in dose achievable by addition of gadolinium (Gd) inside the pellets. In particular, Monte Carlo (MC) simulations were carried out for IRGANOX® 1076 phenolic compound irradiated with neutron beams with different energy spectra at various depths inside a water phantom. The addition of gadolinium increases sensitivity of phenolic ESR (electron spin resonance) dosimeters to neutrons thanks to the high gadolinium cross section for neutron capture and to the large number of secondary particles (mainly Auger and internal conversio…
Compressive sensing for direct time of flight estimation in ultrasound-based NDT
2017
This paper presents an approach for estimation of ultrasonic time-of-flight (TOF) within a Non Destructive Testing (NDT) and Structural Health Monitoring (SHM) context. The presented method leverages recent advances in the field of Compressive Sensing (CS), which makes use of sparsity in a transform domain of a signal in order to reduce the number of samples required to store it. CS achieves this through a two key ideas: random matrix projections, and l1-penalised linear regression. In this case, sparsity arises from the observation that in a pulse-echo ultrasound test, the number of echoes is relatively small compared to the number of measurement points in a waveform. This sparsity is evid…