Tomographic images of biological materials, for example, phantoms of Polyethylene, Polycarbonate, Nylon and Plexiglas with 10 mm diameter with internal bores of 2 to 5 mm diameter and length containing Intralipid-10% solution in various concentrations are obtained. The concentration is defined as the percentage of the volume of the Intralipd-10% against that of water, and the region of interest. In addition to these, the phantoms are filled with few other soft materials (external shell with internal soft material) and the images are obtained. The data acquisition and image reconstruction procedures of the laser CT system are similar to those of X-ray CT. The images are acceptably distinct. Based on experimental observation of the images, the present system can reconstruct images of small objects and soft materials in the trans-illumination mode. In addition, we have studied partially the dynamical properties of the embedded biological soft tissue of a snail.
μ-tomographic images are obtained for few soft materials with multi-structure, cylinder with holes of different diameter and biological soft tissue. 2D images are obtained in the transmission mode. 3D images are reconstructed with the use of the 2D slices for visualization of the internal structure. In addition, we used few simple geometrical approximations, for example, total geometrical efficiency, solid angle contribution and gradient. We obtained a series of images in the region 24-27 keV. 3D visualization of the materials is processed and analyzed the results. The present study is also focused on few geometrical considerations in order to design the collimators in front of the fluorescent source to improve the geometrical efficiency.
Fluorescent x-ray CT (FXCT) with synchrotron radiation (SR) is being developed to detect the very low concentration of specific elements. The endogenous iodine of the human thyroid and the non-radioactive iodine labeled BMIPP in myocardium were imaged by FXCT. FXCT system consists of a silicon (111) double crystal monochromator, an x-ray slit, a scanning table for object positioning, a fluorescent x-ray detector, and a transmission x-ray detector. Monochromatic x-ray with 37 keV energy was collimated into a pencil beam (from 1 mm to 0.025 mm). FXCT clearly imaged endogenous iodine of thyroid and iodine labeled BMIPP in myocardium, whereas transmission x-ray CT could not demonstrate iodine. The distribution of iodine was heterogeneous within thyroid cancer, and its concentration was lower than that of normal thyroid. Distribution of BMIPP in normal rat myocardium was almost homogeneous; however, reduced uptake was slightly shown in ischemic region. FXCT is a highly sensitive imaging modality to detect very low concentration of specific element and will be applied to reveal endogenous iodine distribution in thyroid and to use tracer study with various kinds of labeled material.
An image intensifier based computed tomography scanner and a tube source of x-rays are used to obtain the images of small objects, plastics, wood and soft materials in order to know the interior properties of the material. A new method is developed to estimate the degree of monochromacy, total solid angle, efficiency and geometrical effects of the measuring system and the way to produce monoenergetic radiation. The flux emitted by the x-ray tube is filtered using the appropriate filters at the chosen optimum energy and reasonable monochromacy is achieved and the images are acceptably distinct. Much attention has been focused on the imaging of small objects of weakly attenuating materials at optimum value. At optimum value it is possible to calculate the three-dimensional representation of inner and outer surfaces of the object. The image contrast between soft materials could be significantly enhanced by optimal selection of the energy of the x-rays by Monte Carlo methods. The imaging system is compact, reasonably economic, has a good contrast resolution, simple operation and routine availability and explores the use of optimizing tomography for various applications.
Compton scattering is a potential tool for the determination of bone mineral content or tissue density for dose planning purposes, and requires knowledge of the energy distribution of the X-rays through biological materials of medical interest in the X-ray and (gamma) -ray region. The energy distribution is utilized in a number of ways in diagnostic radiology, for example, in determining primary photon spectra, electron densities in separate volumes, and in tomography and imaging. The choice of the X-ray energy is more related to X-ray absorption, where as that of the scattering angle is more related to geometry. The evaluation of all the contributions are mandatory in Compton profile measurements and is important in X-ray imaging systems in order to achieve good results. In view of this, Compton profile cross-sections for few biological materials are estimated at nineteen K(alpha) X-ray energies and 60 keV (Am-241) photons. Energy broadening, geometrical broadening from 1 to 180 degree(s), FWHM of J(Pz) and FWHM of Compton energy broadening has been evaluated at various incident photon energies. These values are estimated around the centroid of the Compton profile with an energy interval of 0.1 keV and 1.0 keV for 60 keV photons. The interaction cross sections for the above materials are estimated using fractions-by-weight of the constituent elements. Input data for these tables are purely theoretical.
Elastic and inelastic scattering cross-sections for low, medium and high Z atoms are measured in vacuum using an x- ray tube with a secondary targets as an excitation source. Monoenergetic K(alpha) radiation emitted from the secondary target is used to excite the sample. Monoenergetic radiation emitted from the secondary target is used to excite the sample. Monoenergetic radiation is also produced using two secondary targets coupled to an x-ray tube and the radiation from the second target of the system is used to excite the sample. Elastic and inelastic scattering of K(alpha) X-ray line energies of the secondary target by the sample are recorded with Hp Ge and Si(Li) detectors. Using this system the degree of monochromaticity of the secondary emission and the geometrical effects of the measuring system is estimated. The efficiency is large because the secondary target acts as a converter. Experimental results based on this system will be presented and compared with theoretical estimates. The importance of the dat and the potential use of the system for few applications in the field of medicine and archaeometry will also be presented.
Images of small plastic and food materials are obtained using a tomographic device based on image intensifier at optimum energy. The flux emitted by the x-ray tube is filtered using appropriate filters at the chosen optimum energy and reasonable monochromacy is achieved and the images are acceptably distinct.
KEYWORDS: Scattering, X-ray imaging, X-rays, Signal attenuation, Medical imaging, Monte Carlo methods, Tomography, Compton scattering, Rayleigh scattering, Bone
Photon interaction cross sections for a few biological materials are calculated at 60 keV using non-relativistic form factors and the incoherent scattering function approximation. Compton, Rayleigh and total scattering cross sections were estimated in the momentum transfer region 0 to 5Ao-1 for simulation and compilation purposes. Rayleigh scattering cross sections for water are estimated using the molecular form factors of Morin at low photon energies. Computed tomographic images of a few soft materials are obtained using a tomographic system based on an image intensifier. It consists of a charged coupled device camera and an acquisition board. The charge coupled device and the acquisition board allows image processing, filtration and restoration. A reconstruction program, written in PASCAL is able to give the reconstruction matrix of the linear attenuation coefficients, and simulates the matrix and the related tomography. X-ray imaging is a well established technique of detecting strongly attenuating materials as distinguished from weakly attenuating materials. The image contrast between the weakly attenuating materials can be enhanced by optimum selection of the X-ray energy and improving the spatial resolution.
Various apparatus for x and (gamma) -ray computed tomography (CT) have been constructed by us during the last 20 years, with the aim of producing simple and low-cost systems for nondestructive testing. The first one was constructed in 1980 and used an Am241 radioactive source emitting 59.6 keV (gamma) -rays and a single NaI(Tl)-x ray detector. Successively, the radioactive source was substituted during the years by x-ray tubes, and the single detector by multi- detection system such as arrays of detectors and image intensifiers. The last CT-scanner employs a 160 kV x-ray tube and a 6' X 6' image intensifier coupled through a lens to a cooled CCD-camera. At the same time, also (gamma) CT-scanners were constructed for large size and/or high-density samples. These are based on Ir192 or Cs137 radioactive sources coupled to a single NaI(Tl)(gamma) -ray detector. The characteristics and properties of the CT-scanners based on the use of x-ray tubes, emitting x-rays in the energy range 20 - 100 keV, and on (gamma) emitting radioisotopes (Ir192 and Cs137) have been studied and will be described in this paper. Various types of objects have been studied: test objects and common objects such as tree trunks, wood fragments, nuts, ceramic samples, insulators and, etc. Samples have been imaged, after using iodine compounds as tracers.
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