[en] The present invention concerns a detector for tomography by Compton scattering at 90⁰. The difference between this detector and those currently used previously lies in the fact that the collection aperture of the radiation at normal angle to the incident beam is large and can reach 180⁰ and even more. This fact allows to collect an important part of the scattered radiation. A good image quality is obtained with low radiation doses delivered to the body as compared to previous techniques. This detector can be operated in analogical mode which presents the advantage to be faster and easier to realize

[en] The principles of operation of the Anger Gamma Camera and its main applications are reviewed. New developments at Elscint include the removal of Compton scattered events from the image and attenuation correction in Single Photon Emission Tomography (SPECT) using external sources. The Positron Emission Tomography (PET) method and its current implementation on Gamma Cameras is also discussed. (author)

[en] Experimental study of the Compton scattering on protons by nearly polarized photons in the kinematical range of E_γ=0,6-0,9 GeV and angles from 90 to 120 degrees has been performed for the first time. Results obtained on the cross-section asymmetry Σ are compared with the various model predictions. 12 refs

[en] A calculational model to predict the backscattered field based on Compton scattering is described, and the model is verified by measurements of simple phantoms. The phantoms tested - cylinders of polymethylmethacrylate (PMM) with air gaps and aluminium rods placed internally - are irradiated on a scanning assembly, built to simulate a first generation CT scanner with a transmission and a scatter detector (the SCAT-CAT). After verification of the model for the scattered field calculations, a method of extracting information from the scattered field is developed, based on ratios of scatter signals from non-uniform to uniform phantoms. This method is demonstrated for predicted data of a simulated phantom and for measured data of the same and two additional phantoms. The method is very sensitive to air gaps in the phantoms because of the relative electron density of air with respect to PMM; it is not as sensitive to aluminium rods for the same reason. Various methods of applying the scattered field information to produce an image representing a simulated phantom are considered, and a preferred method chosen to reconstruct scattered field data into an image for the three phantoms studied. (author)

[en] An inversion of Radon transform for N-dimensional space in terms of spherical harmonics and orthogonal polynomials have been presented. Partial solution for N=3 leads to a new method for reconstruction of electronic densities from Compton profiles. This technique, based on the expansion of experimental spectra and densities into Jacobi polynomials is compared with other reconstruction methods. (author). 7 refs

[en] we are living an exciting 'neuroimaging era'.The combined (sometimes simultaneous) use of brain structures that can be imaged for morphology, function, and misfolded proteins gives the clinicians a formidable mean to understand pathophysiology of a disease at the individual level thus going toward a true tailored medicine, at least from a diagnostic point of view. As a counterpart, these tools tremendously increase health care costs and must be regulated by national health system agencies in order to be used where and when necessary. Also, more funds are needed to speed up research and favor scientific achievements, as the only way to improve the quality of life of our patients.

[en] Compton imaging devices employ electronic collimation to determine the direction of photons coming from a radio-tracer labeled organ. They therefore not subject to the limiting constraint imposed by mechanical collimators, for which sensitivity and spatial resolution are inversely coupled. As a result,the sensitivity can be dramatically increased for a comparable resolution. Furthermore, their performance improve rapidly with increasing photon energy, making possible to achieve spectacular gains over conventional mechanical collimation. simulations predict a great improvement over existing devices. A first prototype has been built, and images have been reconstructed. The results prove the feasibility of this technique nad its implementation using silicon detectors as electronic collimators. (Author) 5 refs

[en] Looking for the development of the non-destructive technique and its application for industrial purposes, the Nuclear Instrumentation Laboratory of COPPE/UFRJ has built up prototypes of a tomographic system based on the Compton Effect. This paper reports an optimization of the first prototype, in what concernes the physical mounting as well as the algorithm developed to analyse the experimental data, whose main advantage is the possibility of calculating densities at any point of the object under investigation, without interference of precedent analysis. Simulated tests with standard objects irradiations confirm theoretical estimations. (Author)

[en] To evaluate, on a retrospective basis, the anatomic characteristics of the arterial supply to the sinoatrial node (SAN) in the Korean population using an ECG-gated multi-detector CT (MDCT). The electrocardiographic-gated MDCTs of 500 patients (258 men and 242 women; age range, 17-83 years; mean age, 58.6 ± 12.04 years) were analyzed retrospectively. In each case, the SAN artery (arteries) was named according to a special nomenclature with regard to origin, course, and termination. A total of 516 SAN arteries were visualized in 496 patients. The SAN was supplied by a single artery in 476 (96.4%) cases and by 2 arteries in 18 (3.6%) cases. The SAN originated from the right coronary artery in 265 (53.4%) cases and from the left circumflex in 213 (43%) cases. This study can provide basic data on variations of the SAN artery in the Korean population.

[en] Electronically collimated Compton Cameras have been tested in Single Photon Emission Tomography (SPECT) systems instead of mechanically collimated gamma detectors in order to improve their limited sensitivity. One of the main factors that contribute to the worsening of the angular resolution and thus to the deterioration of the system spatial resolution is Doppler broadening. Double differential Klein-Nishina equation is used to consider the random movement of electron inside the crystal. It is important to perform this analysis for each particular material because is difficult to infer one simple Doppler broadening dependency of the atomic number Z. In high Z materials the internal electrons are strongly linked to the nucleus and therefore there can be found high momentums, but they represent just a small portion of the electrons that suffers Compton scattering. This work estimates the influence of the Doppler broadening in CdZnTe semiconductor for different incoming photon energies. For this means there are analyzed main Compton broadening processes in semiconductor Cd_0,8Zn_0,2Te with density ρ=5,85g/cm³. (Author)