Сторінки трудової та громадської діяльності Олександра Гіталова в документах держархіву кіровоградської області

(uk) У статті аналізуються матеріали Держархіву Кіровоградської області за другу пол. 40-х – 80-і рр. ХХ ст., які розкривають життєвий шлях бригадира тракторної бригади колгоспу с. Комишуватого Новоукраїнського району на Кіровоградщині, двічі Героя Соціалістичної Праці Олександра Гіталова. Подано огляд особового фонду механізатора. Наведено приклади з документів виконкому облради, обласних управління сільського господарства та телерадіокомітету, Новоукраїнського райвиконкому та ін.(en) The materials of a record office of Kirovograd region for the second half of the 40 s. – 80 s. of 20th century, which expose the life of a brigadier of a tractor brigade of collective farm of Komyshuvate villarde, Novoukrainka district, Kirovograd region, twice hero of social labour of Alexander Gitalov, are analised in the article. The review of the mechanization expert’s personal fund is suggesten. The examples of the documents of executive committee, regional management of agriculture and TVradiocompany and others are given

Calculation of scatter in cone beam CT : Steps towards a virtual tomograph

Scattered photons—shortly scatter—are generated by interaction processes when photon beams interact with matter. In diagnostic radiology, they deteriorate image quality since they add an undesirable signal that lowers the contrast in projection radiography and causes cupping and streak artefacts in computed tomography (CT). Scatter is one of the most detrimental factors in cone beam CT owing to irradiation geometries using wide beams. It cannot be fully eliminated, nevertheless its amount can be lowered via scatter reduction techniques (air gaps, antiscatter grids, collimators) and its effect on medical images can be suppressed via scatter correction algorithms. Aim: Develop a tool—a virtual tomograph—that simulates projections and performs image reconstructions similarly to a real CT scanner. Use this tool to evaluate the effect of scatter on projections and reconstructed images in cone beam CT. Propose improvements in CT scanner design and image reconstruction algorithms. Methods: A software toolkit (CTmod) based on the application development framework ROOT was written to simulate primary and scatter projections using analytic and Monte Carlo methods, respectively. It was used to calculate the amount of scatter in cone beam CT for anthropomorphic voxel phantoms and water cylinders. Configurations with and without bowtie filters, antiscatter grids, and beam hardening corrections were investigated. Filtered back-projection was used to reconstruct images. Automatic threshold segmentation of volumetric CT data of anthropomorphic phantoms with known tissue compositions was tested to evaluate its usability in an iterative image reconstruction algorithm capable of performing scatter correction. Results: It was found that computer speed was the limiting factor for the deployment of this method in clinical CT scanners. It took several hours to calculate a single projection depending on the complexity of the geometry, number of simulated detector elements, and statistical precision. Data calculated using the CTmod code confirmed the already known facts that the amount of scatter is almost linearly proportional to the beam width, the scatter-to-primary ratio (SPR) can be larger than 1 for body-size objects, and bowtie filters can decrease the SPR in certain regions of projections. Ideal antiscatter grids significantly lowered the amount of scatter. The beneficial effect of classical antiscatter grids in cone beam CT with flat panel imagers was not confirmed by other researchers nevertheless new grid designs are still being tested. A simple formula estimating the effect of scatter on the quality of reconstructed images was suggested and tested. Conclusions: It was shown that computer simulations could calculate the amount of scatter in diagnostic radiology. The Monte Carlo method was too slow for a routine use in contemporary clinical practice nevertheless it could be used to optimize CT scanner design and, with some enhancements, it could become a part of an image reconstruction algorithm that performs scatter correction

Calculation of scatter in cone beam CT : Steps towards a virtual tomograph

Scattered photons—shortly scatter—are generated by interaction processes when photon beams interact with matter. In diagnostic radiology, they deteriorate image quality since they add an undesirable signal that lowers the contrast in projection radiography and causes cupping and streak artefacts in computed tomography (CT). Scatter is one of the most detrimental factors in cone beam CT owing to irradiation geometries using wide beams. It cannot be fully eliminated, nevertheless its amount can be lowered via scatter reduction techniques (air gaps, antiscatter grids, collimators) and its effect on medical images can be suppressed via scatter correction algorithms. Aim: Develop a tool—a virtual tomograph—that simulates projections and performs image reconstructions similarly to a real CT scanner. Use this tool to evaluate the effect of scatter on projections and reconstructed images in cone beam CT. Propose improvements in CT scanner design and image reconstruction algorithms. Methods: A software toolkit (CTmod) based on the application development framework ROOT was written to simulate primary and scatter projections using analytic and Monte Carlo methods, respectively. It was used to calculate the amount of scatter in cone beam CT for anthropomorphic voxel phantoms and water cylinders. Configurations with and without bowtie filters, antiscatter grids, and beam hardening corrections were investigated. Filtered back-projection was used to reconstruct images. Automatic threshold segmentation of volumetric CT data of anthropomorphic phantoms with known tissue compositions was tested to evaluate its usability in an iterative image reconstruction algorithm capable of performing scatter correction. Results: It was found that computer speed was the limiting factor for the deployment of this method in clinical CT scanners. It took several hours to calculate a single projection depending on the complexity of the geometry, number of simulated detector elements, and statistical precision. Data calculated using the CTmod code confirmed the already known facts that the amount of scatter is almost linearly proportional to the beam width, the scatter-to-primary ratio (SPR) can be larger than 1 for body-size objects, and bowtie filters can decrease the SPR in certain regions of projections. Ideal antiscatter grids significantly lowered the amount of scatter. The beneficial effect of classical antiscatter grids in cone beam CT with flat panel imagers was not confirmed by other researchers nevertheless new grid designs are still being tested. A simple formula estimating the effect of scatter on the quality of reconstructed images was suggested and tested. Conclusions: It was shown that computer simulations could calculate the amount of scatter in diagnostic radiology. The Monte Carlo method was too slow for a routine use in contemporary clinical practice nevertheless it could be used to optimize CT scanner design and, with some enhancements, it could become a part of an image reconstruction algorithm that performs scatter correction

Analysis of the tandem calibration method for kerma area meters vis Monte Carlo simulations

The IAEA recommends that uncertainties of dosimetric measurements in diagnostic radiology for risk assessment and quality assurance should be less than 7% on the confidence level of 95%. This accuracy is difficult to achieve with kerma area product (KAP) meters currently used in clinics. The reasons range from the high energy dependence of KAP meters to the wide variety of configurations in which KAP meters are used and calibrated. The tandem calibration method introduced by Pöyry, Komppa and Kosunen in 2005 has the potential to make the calibration procedure simpler and more accurate compared to the traditional beam-area method. In this method, two positions of the reference KAP meter are of interest: (a) a position close to the field KAP meter and (b) a position 20 cm above the couch. In the close position, the distance between the two KAP meters should be at least 30 cm to reduce the effect of back scatter. For the other position, which is recommended for the beam-area calibration method, the distance of 70 cm between the KAP meters was used in this study. The aim of this work was to complement existing experimental data comparing the two configurations with Monte Carlo (MC) simulations. In a geometry consisting of a simplified model of the VacuTec 70157 type KAP meter, the MCNP code was used to simulate the kerma area product, PKA, for the two (close and distant) reference planes. It was found that PKA values for the tube voltage of 40 kV were about 2.5% lower for the distant plane than for the close one. For higher tube voltages, the difference was smaller. The difference was mainly caused by attenuation of the X ray beam in air. Since the problem with high uncertainties in PKA measurements is also caused by the current design of X ray machines, possible solutions are discussed

Steps towards a virtual tomograph

ii To the people of the Earth. Some time ago a group of hyper-intelligent pan dimensional beings decided to finally answer the great question of Life, The Universe and Everything. To this end they built an incredibly powerful computer, Deep Thought. After the great computer programme had run (a very quick seven and a half million years) the answer was announced. The Ultimate answer to Life, the Universe and Everything is (You’re not going to like it) Is... 4

CTmod : a toolkit for Monte Carlo simulation of projections including scatter in computed tomography

The CTmod toolkit is a set of C++ class libraries based on the CERN’s application development framework ROOT. It uses the Monte Carlo method to simulate energy imparted to a CT-scanner detector array. Photons with a given angle–energy distribution are emitted from the X-ray tube approximated by a point source, transported through a phantom, and their contribution to the energy imparted per unit surface area of each detector element is scored. Alternatively, the scored quantity may be the fluence, energy fluence, plane fluence, plane energy fluence, or kerma to air in the center of each detector element. Phantoms are constructed from homogenous solids or voxel arrays via overlapping. Implemented photon interactions (photoelectric effect, coherent scattering, and incoherent scattering) are restricted to the energy range from 10 to 200 keV. Variance reduction techniques include the collision density estimator and survival biasing combined with the Russian roulette. The toolkit has been used to estimate the amount of scatter in cone beam computed tomography and planar radiography.Original Publication:Alexandr Malusek, Michael Sandborg and Gudrun Alm Carlsson, CTmod: a toolkit for Monte Carlo simulation of projections including scatter in computed tomography, 2008, Computer Methods and Programs in Biomedicine, (90), 2, 167-178.http://dx.doi.org/10.1016/j.cmpb.2007.12.005Copyright: Elsevier Science B.V., Amsterdam.http://www.elsevier.com

ACCURATE KAP METER CALIBRATION AS A PREREQUISITE FOR OPTIMISATION IN PROJECTION RADIOGRAPHY

Modern X-ray units register the air kerma–area product, PKA, with a built-in KAP meter. Some KAP meters show an energydependent bias comparable with the maximum uncertainty articulated by the IEC (25 %), adversely affecting dose-optimisation processes. To correct for the bias, a reference KAP meter calibrated at a standards laboratory and two calibration methods described here can be used to achieve an uncertainty of &lt;7 % as recommended by IAEA. A computational model of the reference KAP meter is used to calculate beam quality correction factors for transfer of the calibration coefficient at the standards laboratory, Q0, to any beam quality, Q, in the clinic. Alternatively, beam quality corrections are measured with an energy-independent dosemeter via a reference beam quality in the clinic, Q1, to beam quality, Q. Biases up to 35 % of built-in KAP meter readings were noted. Energy-dependent calibration factors are needed for unbiased PKA. Accurate KAP meter calibration as a prerequisite for optimisation in projection radiography.Funding agencies: Swedish Radiation Safety Authority, SSM [SSM 2014-1204]</p

CTmod : Mathematical Foundations

CTmod is a set of C++ class libraries primarily designed for the simulation of energy imparted to a CT-scanner detector array using the Monte Carlo method. This report describes mathematical methods and formulas that are used in the code. It is a supplement to the article “CTmod - a toolkit for Monte Carlo simulation of projections including scatter in computed tomography” by A. Malusek, M. Sandborg, and G. Alm Carlsson. In this report, random variables are denoted by a hat. For instance ˆx is a random variable and x is its sample. Points in space are denoted by bold capital letters, e.g. P. Directions are denoted by bold small letters, e.g. u. Inconsistencies in the current notation will be corrected in the next update of this report

Validation of the CTmod toolkit

This report is a supplement to the article “CTmod—a toolkit for Monte Carlo simulation of projections including scatter in computed tomography” by A. Malusek, M. Sandborg, and G. Alm Carlsson. It describes methods that were used to validate the CTmod toolkit. Here, we adopt the terminology used in and: Verification is a process of determining whether or not the software is coded correctly and conforms to the specified requirements. Validation is a process of evaluating software to ensure compliance with physical applicability to the process being modelled. Validation of a code would consist of comparing it with known analytical solutions or against an already validated computer code, or could include benchmarking the code against relevant experimental data. CTmod is a toolkit implemented as a C++ class libray. A user is supposed to write a main program which uses classes from the toolkit. The main program is then compiled to create an executable. In this report, we tested two executables (ctmod1 and ctmod2) created this way. In chapter 2, scatter-to-primary ratios of air collision kerma calculated using ctmod1 are compared to data published in literature. In chapter 3, primary and scatter projections calculated using ctmod2 are compared to data calculated using the MCNP5 code. Though not related to the validation, we also report speeds of ctmod1 and ctmod2 as these were often requested from us

Проблеми війського будівництва 1917 - 1918 рр. в оцінках провідників Української революції

У статті зроблена спроба проаналізувати погляди учасників революційних подій на проблеми військового будівництва за доби Центральної Ради та Української держави П. Скоропадського