Vainikinių arterijų tyrimas daugiapjūviu kompiuteriniu tomografu (DKT) į klinikinę praktiką įdiegtas nesenai. Tai neinvazyvus tyrimo metodas, kurį galima atlikti ir ambulatoriniams pacientams. Tačiau greta savo privulumų, jis turi ir trūkumų – dėl nuolatinio vainikinių arterijų judėjimo širdies ciklo metu gali atsirasti liekamųjų judesio artefaktų atkuriant vaizdus. Jų tikimybė priklauso ne tik nuo aparato, kuriuo atliekamas tyrimas, techninių charakteristikų, bet ir nuo širdies veiklos ypatumų. Yra atlikta nemažai tyrimų, įvertinančių vainikinių arterijų vaizdų kokybės priklausomybę nuo širdies susitraukimų dažnio, jo variabilumo, kitų faktorių. Kairiosios Hiso pluošto kojytės blokados, sąlygojančios nesinchronišką skilvelių susitraukimą ir atsipalaidavimą, įtaka vaizdų kokybei tyrinėta mažai. Šiame tyrime buvo palyginta vaizdų kokybė tarp pacientų, kuriems nustatyta visiška kairiosios Hiso pluošto kojytės blokada ir nėra laidžiosios sistemos sutrikimų, grupių. Analizuota vainikinių arterijų įvertinimo visuose širdies ciklo rekonstrukciniuose intervaluose įtaka vaizdų kokybės vidurkiui. Nustatyta, kokia yra DKT tyrimo diagnostinė vertė identifikuojant hemodinamiškai reikšmingas vainikinių arterijų stenozes. Kadangi DKT tyrimas susijęs su jonizuojančia spinduliuote, įvertinti rentgeno vamzdžio srovės stiprumo moduliavimo ypatumai. Taip pat nustatyta širdies susitraukimų dažnio, jo variabilumo įtaka vaizdų kokybei, esant visiškai kairiosios Hiso pluošto kojytės blokadai. / Multislice computed tomography (MSCT) coronary angiography is one of the latest usage area of the computed tomography technology. It s a non-invasive diagnostic tool, wich can be performed in ambulant patients. MSCT coronary angiography beside it's advantages has some drawbacks. The main drawbacks are lower spatial resolution and residual motion artifacts in MSCT images. Therefore quality of coronary images and diagnostic value of MSCT angiography differs, depending on patient's clinical characteristics, especially on heart contraction features during scanning. Asynchronic contraction and relaxation of the right and left ventricles, caused of bundle branch block can also influence image quality of MSCT coronary angiography. To date, there are only few studies, conducted to analyse diagnostic performance of MSCT coronary angiography in patients with left bundle branch block. Although influence of heart rate, heart rate variability and the other factors (for example, age, sex, body mass index) on MSCT image quality are quite well investigated. Thus, the present study were designed to investigate the influence of complete left bundle branch block on image quality of MSCT coronary angiography more detail in comparison with control patients group without electrical conduction disturbances, reveal the diagnostic value of MSCT angiography to identify hemodinamicaly significant coronary stenosis.

Thesis problem: Cone beam computed tomography (CBCT) can provide images with identical information and considerable dose reduction compared with reasonably low costs compared to multislice computed tomography (MSCT) especially where multiple follow up imaging studies are needed. The purpose of this study was to evaluate the diagnostic usefulness of CBCT, using i-CAT®'s software, for detection of the anatomical landmarks of the external, middle and inner ear to answer this question whether MSCT Can be replaced by dental CBCT for evaluation of the temporal bone. Material and methods: Cone beam computed tomography (CBCT) images of 63 subjects made with the same machine, with unknown clinical histories and no evidence of pathosis on CBCT images, were evaluated by two oral and maxillofacial radiologists retrospectively. Seven anatomical points (scutum, oval window, incudomalleolar joint, the tympanic/horizontal and mastoid/vertical segments of the facial nerve, anterior and posterior crura of stapes) of the right and left temporal bone (total of 120 temporal bones) were evaluated. The results were provided as percentage of the points identified by each radiologist. The intra and inter observer agreement were calculated using kappa statistic. Results: The scutum, the tympanic/horizontal segment of the facial nerve canal and the oval window of the right and left temporal bone of 63 cases (total 126 temporal bones) were visualized by the first observer as well-defined structures in 100%, 96.03% and 100% of the cases, respectively. The tympanic/horizontal segment of the facial nerve canal was visualized as a poorly-defined structure in 2.38 % and could not be identified in 1.59% of the cases. The anterior and posterior crura of stapes, the mastoid/vertical segments of the facial nerve canal and the incudomalleolar joint were visualized as well-defined structures in 24.60%, 53.17%, 99.21% and 57.94% of the cases, as poorly defined structures in 32.54%, 41.27%, 0.79% and 39.68% of the cases respectively. The anterior and posterior crura of stapes, the mastoid/vertical segments of the facial nerve canal and the incudomalleolar joint could not be identified in 42.86%, 5.56%, 0% and 2.38% of the cases respectively. The intra- and inter-observer agreement ranged from strong for tympanic/horizontal and mastoid/vertical segments of the facial nerve canal to poor for the anterior and posterior crura of stapes and also the incudomalleolar joint. Conclusion: The i-CAT CBCT machine is a promising replacement for MSCT in evaluation of the temporal bone where there is no need for evaluation of the anterior and posterior crura of stapes and the incudomalleolar joint which are the smallest anatomical structures in the temporal bone. Other CBCT machines with higher contrast to noise ratio should be evaluated for detection of those anatomical structures since CBCT can reduce the patient dose substantially where multiple follow up CT studied are needed. Key words: Computed tomography; cone beam CT; multislice helical CT; middle ear; inner ear; temporal bone.

This report introduces the multislice method for modeling the interaction between an electron and the atoms in the specimen (electron-specimen interaction). The multislice method is an approximation to the full quantum mechanical model for this interaction. After introducing the theory, we discuss how the multislice method is implemented and integrated into TEM-simulator, a software for simulation of Transmission Electron Microscope (TEM) images.

<p>Kompjuterizovana tomografija (CT) je jedan od najznačajnijh dijagnostičkih modaliteta, čija upotreba raste iz decenije u deceniju. U ukupnom broju radiolo&scaron;kih pregleda CT je zastupljena sa 5-10%, ali je njen doprinos ukupnoj dozi za populaciju veći od 50%. Osnovni pokazatelji kvaliteta slike i doza, kao i prateći radijacioni rizik zavise od primenjene radiografske tehnike odnosno CT pregleda. U smislu&nbsp; dobre radiolo&scaron;ke prakse i u skladu sa osnovnim principima za&scaron;tite od zračenja, poželjna je primena najniže moguće doze za pacijenta uz održavanje kvaliteta slike i dijagnostičke informacije. Cilj istraživanja jeste definisanje optimalnog protokola pregleda vi&scaron;eslojnom CT za dijagnozu pojedinih regija tela, kao i da se utvrde doze i radijacioni rizik za pacijente pre i nakon optimizacije protokola. Analizom je obuhvaćeno ukupno 437 pacijenata, koji su podeljeni u grupe prema regijama tela koje su snimane: I&ndash;nekontrastni CT glave, II-CT glave sa i.v. kontrastom, III-CT grudnog ko&scaron;a, IV-CT abdomena i karlice i V-CT angio (CT angiografija aortoilijačnog segmenta i donjih ekstremiteta). Studija je izvedena u 2 faze: u I fazi je kori&scaron;ćen standardni protokol za regiju tela koja se snimala, a u II fazi CT pregledi su izvedeni po modifikovanom protokolu (promenom parametra vrednosti mAs), uz minimalne zahteve u pogledu kvaliteta slike.Na osnovu dozimetrijskih&nbsp; pokazatelja procenjena je efektivna doza i radijacioni rizik za pacijente u obe faze. U studiji su kori&scaron;ćene smernice iz Vodiča EUR 16262&nbsp; EN, u kojima su definisani parametri za procenu kvaliteta slike da bi se analizirali različiti anatomski preseci određenih regija tela koji su se snimali. Kvalitet slike za svakog pacijenta je ocenjen pomoću trostepene skale vizualizacije za svaki parametar anatomske regije: 0-detalji su vidljivi, 1-detalji se prikazuju, 2-detalji se jasno prikazuju. Kori&scaron;ćena je subjektivna metoda gde su dva iskusna radiologa vr&scaron;ili interpretaciju slike. Konačna ocena kvaliteta slike svakog pregleda odgovara zbiru svih parametara procenjenih po trostepenoj skali&nbsp; vizualizacije. Zatim je za potrebe izračunavanja veličine FOM (figure of merit) izračunata vrednost indeksa ocene kvaliteta slike (zbir svih&nbsp; ocena parametra/brojem parametara). Vrednost FOM je izračunata kao količnik indeksa ocene kvaliteta slike i efektivne doza po pacijentu. Prosečna vrednost FOM za svaku grupu ispitanika nam je poslužila kao relativni pokazatelj za upoređivanje između neoptimizovane i optimizovane grupe ispitanika za isti tip pregleda. Poređenjem vrednosti efektivne doze u prvoj i drugoj fazi istraživanja kvantifikovano je smanjenje radijacionog opterećenja za pacijente nakon optimizacije protokola. Rezultati su pokazali da je optimalnim izborom protokola u&nbsp;&nbsp; smislu parametara ekspozicije (smanjenjem vrednosti mAs) moguće značajno smanjiti dozu zračenja kod pregleda glave za 7,5%, kod pregleda glave sa angiografijom za 7%, kod pregleda grudnog ko&scaron;a za 40%, kod pregleda abdomena i karlice za 25%. Grupa CT angio&nbsp; nije mogla da bude optimizovana, jer aparat nije prihvatao promenu kvaliteta slike kod zadatih parametara optimizacije. Primenom standardnih protokola postiže se kvalitet slike bolji nego &scaron;to je neophodno, a samim tim i veća doza zračenja nego &scaron;to je potrebno. Optimalnim izborom protokola u smislu parametara ekspozicije moguće je značajno smanjiti dozu zračenja, uz održavanje kvaliteta slike koji je dovoljan za adekvatnu radiolo&scaron;ku interpretaciju slike.</p> / <p>Computed&nbsp; tomography (CT) is one of the most significant diagnostic methods whose application has been increasing from decade to decade.&nbsp; Among the total number of radiological examinations CT accounts for 5-10%, however, its contribution in the whole dosage for the population is greater than 50%. Main indicator of the quality of images and dosages as well as the accompanying irradiation risk depend on applied radiographic technique that is CT examination. In the sense of good radiological practice and in accordance with basic principles of protection from irradiation, the application of the lowest possible dosage for a patient together with preserving the quality of image and diagnostic information are mostly welcomed. The goal of the research is to define the optimum examination protocol by multislice CT in diagnostics of certain body regions as well as to determine dosages and irradiation risk for patients both before and after protocol optimization. The analysis has included 437 patients divided into groups according to body regions which have been scanned: I-unenhanced head CT, II contrast enhanced head CT, III&ndash;chest CT, IV&ndash;abdomen and pelvis CT and&nbsp; V&ndash;angio CT (CT angiography of aortoiliac segment and lower extremities). The study has been conducted in 2 phases: in the first phase standard protocol for the scanned body region has been applied, and in the second phase CT examinations have been carried out according to the modified&nbsp; protocol&nbsp; (by change of parameters of values mAs)&nbsp; with minimum&nbsp; requirements&nbsp; regarding&nbsp; the&nbsp; image&nbsp; quality. On&nbsp; the&nbsp; basis&nbsp; of&nbsp; dosimetric&nbsp; indicators&nbsp; the&nbsp; efficient&nbsp; dosage&nbsp; and&nbsp; irradiation&nbsp; risk&nbsp; for&nbsp; the patients in both phases have been assessed. In the study the guidelines form the Guide EUR&nbsp; 16262&nbsp; EN&nbsp; have&nbsp; been&nbsp; observed&nbsp; where&nbsp; parameters for&nbsp; the&nbsp; assessment&nbsp; of&nbsp; image quality&nbsp; have&nbsp; been&nbsp; defined&nbsp; in&nbsp; order&nbsp; to&nbsp; analyze&nbsp; different&nbsp; anatomic&nbsp; cross sections of certain body&nbsp; regions.&nbsp; Image quality&nbsp; for&nbsp; each&nbsp; patient&nbsp; was&nbsp; assessed&nbsp; by&nbsp; three-level visualization&nbsp; scale&nbsp; for&nbsp; each&nbsp; parameter&nbsp; of&nbsp; anatomic&nbsp; region:&nbsp; 0&ndash;details&nbsp; are&nbsp; visible, 1&ndash;details are&nbsp; presented,&nbsp; 2&ndash;details are clearly&nbsp; presented.&nbsp; A&nbsp; subjective&nbsp; method&nbsp; was applied&nbsp; where&nbsp; two&nbsp; experienced&nbsp; radiologists performed&nbsp; the&nbsp; image interpretation. Final assessment&nbsp; of&nbsp; image quality&nbsp; of&nbsp; every&nbsp; examination corresponds&nbsp; to&nbsp; the&nbsp; sum&nbsp; of&nbsp; all parameters&nbsp; according&nbsp; to&nbsp; three-level&nbsp; visualization&nbsp; scale. Further,&nbsp; for&nbsp; the&nbsp; need&nbsp; of calculation of the size of FOM (figure of merit) the value of the index of assessment of the&nbsp; image&nbsp; quality&nbsp; (sum of all assessments of parameters/number of&nbsp; parameters) has been&nbsp; calculated.&nbsp; The&nbsp; value of&nbsp; FOM&nbsp; has&nbsp; been&nbsp; calculated as a quotient&nbsp; of&nbsp; the&nbsp; image quality assessment index and effective dosage per patient.&nbsp; The average value of FOM for&nbsp; every&nbsp; group&nbsp; of&nbsp; patients&nbsp; has&nbsp; offered us a&nbsp; relative&nbsp; indicator for&nbsp; comparison of&nbsp; non-optimum&nbsp; and optimum group of&nbsp; patients&nbsp; for&nbsp; the&nbsp; same&nbsp; type&nbsp; of&nbsp; examinations.&nbsp; By comparison of values of effective dosage in the first and second phase of the research a decrease in irradiation load for patients after protocol optimization was quantified. The results have&nbsp; shown&nbsp; that&nbsp; by&nbsp; optimum&nbsp; protocol&nbsp; selection&nbsp; in&nbsp; the&nbsp; sense&nbsp; of&nbsp; exposition parameters (by&nbsp; reduction of&nbsp; values of&nbsp; mAs) it is&nbsp; possible to reduce significantly&nbsp; the irradiation dosage at&nbsp; unenhanced head CT examination for 7,5%, at contrast enhanced head CT examination for 7%, at chest CT examination for 40%, at abdomen&nbsp; and pelvis CT examination for 25%. The group CT angio could not be optimized since the device&nbsp; did&nbsp; not&nbsp; accept&nbsp; the&nbsp; change in image quality at set&nbsp; optimization parameters. By application&nbsp; of&nbsp; standard&nbsp; protocols the image quality&nbsp; better&nbsp; than required&nbsp; was&nbsp; achieved and along with this, a higher irradiation dosage occurred than required. By selection of protocol in the sense&nbsp; of&nbsp; exposition parameters it is possible to reduce irradiation dosage significantly along with preserving image quality which is&nbsp; sufficient for adequate radiological image interpretation.</p>

In this thesis, two selected topics in magnetism are studied using theoretical modelling and computational methods. The first of these is the magnetocrystalline anisotropy energy (MAE) of transition metal based magnets. In particular, ways of finding 3d transition metal based materials with large MAE are considered. This is motivated by the need for new permanent magnet materials, not containing rare-earth elements, but is also of interest for other technological applications, where the MAE is a key quantity. The mechanisms of the MAE in the relevant materials are reviewed and approaches to increasing this quantity are discussed. Computational methods, largely based on density functional theory (DFT), are applied to guide the search for relevant materials. The computational work suggests that the MAE of Fe1-xCox alloys can be significantly enhanced by introducing a tetragonality with interstitial B or C impurities. This is also experimentally corroborated. Alloying is considered as a method of tuning the electronic structure around the Fermi energy and thus also the MAE, for example in the tetragonal compound (Fe1-xCox)2B. Additionally, it is shown that small amounts (2.5-5 at.%) of various 5d dopants on the Fe/Co-site can enhance the MAE of this material with as much as 70%. The magnetic properties of several technologically interesting, chemically ordered, L10 structured binary compounds, tetragonal Fe5Si1-xPxB2 and Hexagonal Laves phase Fe2Ta1-xWx are also investigated. The second topic studied is that of magnetic effects on the elastic scattering of fast electrons, in the context of transmission electron microscopy (TEM). A multislice solution is implemented for a paraxial version of the Pauli equation. Simulations require the magnetic fields in the sample as input. A realistic description of magnetism in a solid, for this purpose, is derived in a scheme starting from a DFT calculation of the spin density or density matrix. Calculations are performed for electron vortex beams passing through magnetic solids and a magnetic signal, defined as a difference in intensity for opposite orbital angular momentum beams, integrated over a disk in the diffraction plane, is observed. For nanometer sized electron vortex beams carrying orbital angular momentum of a few tens of ħ, a relative magnetic signal of order 10-3 is found. This is considered realistic to be observed in experiments. In addition to electron vortex beams, spin polarised and phase aberrated electron beams are considered and also for these a magnetic signal, albeit weaker than that of the vortex beams, can be obtained. / <p>Felaktigt ISBN i den tryckta versionen: 9789155497149</p><p></p>

Le but de notre travail a été d’évaluer l’effet de la réduction de la dose d’irradiation en TDM multibarrette quant à la performance diagnostique, la confiance de l’observateur dans le diagnostic proposé, la capacité à suggérer un diagnostic alternatif dans quelques pathologies courantes et/ou caractérisées par des situations de faibles contrastes entre les structures anatomiques normales ou pathologiques. Nous avons donc comparé ces paramètres entre des TDM à doses réduites et à doses standard telles que couramment rapportées dans la littérature dans les circonstances suivantes :<p><p>•\ / Doctorat en sciences médicales / info:eu-repo/semantics/nonPublished

Die Magnetresonanztomographie (MRT), die Mehrschicht-Spiral-Computertomographie (MSCT) und die Elektronenstrahl-Computertomographie (EBCT) sind nichtinvasive diagnostische Verfahren, welche die bisherige kardiale Bildgebung zumindest in Teilbereichen ersetzen oder ergänzen können. MR-Perfusions- und MR-Funktionsuntersuchungen konnten in der vorgelegten Arbeit direkte Parameter der myokardialen Vitalität regional erfassen. Die Signalintensitäten im Blut und im Herzmuskel dienten zur quantitativen Bestimmung der Myokardperfusion. Die Ortsauflösung ermöglichte eine Differenzierung der subendo- und der subepikardialen Durchblutung. Zusätzliche Streßuntersuchungen steigerten die Sensitivität des Verfahrens. Relativ geringgradige Koronarstenosen ließen sich durch vornehmlich subendokardial lokalisierte Perfusionsdefekte nachweisen. MR-Tagging- Funktionsanalysen konnten durch ein artifizielles Markierungsgitter zwischen endokardial lokalisiertem Narbengewebe und epikardial liegendem vitalem Gewebe differenzieren. Die Dehnungen, Stauchungen und Rotationen des Myokardverbandes wurden registriert und ausgewertet. Die MSCT und die EBCT wurden als Röntgenverfahren für die nichtinvasive Koronarangiographie verglichen. Bei der Definition der Gefäßkonturschärfe über die Anstiegssteilheit der CT-Dichtewerte zeigte sich eine bessere Abbildungsqualität der MSCT gegenüber der EBCT. Die Bestimmung der Segmenterkennbarkeit zeigte, dass mit der MSCT signifikant mehr erkannt werden konnten. Die vorgestellten kardialen MR- und CT-Untersuchungen konnten aus Gründen der Reproduzierbarkeit sowie aufgrund des Strahlenschutzes nur tierexperimentell durchgeführt werden. Die Validität der unterschiedlichen Tiermodelle ist in vorausgegangenen Studien belegt worden. Die in der Literatur verfügbaren Ergebnisse am Menschen bestätigen in vieler Weise die vorgelegten Daten. / Magnetic resonance imaging (MRI), multislice spiral computed tomography (MSCT), and electron-beam computed tomography (EBCT) are noninvasive imaging modalities that may supplement or in part even replace established diagnostic procedures for assessment of the heart. MRI perfusion and functional studies were shown to enable determination of direct parameters of regional myocardial vitality. The signal intensities of blood and myocardium served to quantify myocardial perfusion. The spatial resolution allowed for differentiating subendocardial and subepicardial perfusion. Additional stress tests improved the sensitivity of the procedure. Relatively low-grade coronary artery stenoses were identified by the presence of perfusion gaps primarily in subendocardial location. Functional analysis by means of MRI tagging using an artificial grid allowed for differentiating endocardial scar tissue from epicardial vital tissue. Extension, compression, and rotation of the myocardial complex were recorded and analyzed. MSCT and EBCT were compared as radiographic procedures for noninvasive coronary angiography. MSCT was found to be superior to EBCT in terms of image quality defined as vascular contour sharpness determined as the steepness of the increase in CT densities. Assessment of segment identification showed that significantly more segments were visualized by MSCT. The cardiac MRI and CT studies presented here could only be performed in animals because of the radiation exposure involved and to ensure reproducibility of the results. The validity of the different animal models used has been demonstrated in preceding studies. The results of the present animal experiments are in agreement with many of the human data published in the literature.