Vienas iš esminių semantinio tinklo komponentų yra ontologijos. Ontologija yra tam tikros dalykinės srities sąvokų visumos specifikavimas išreikštu pavidalu. Semantiniai interneto portalai naudoja ontologijas kaip žinių bazę. Tačiau ontologijų kūrimas nėra toks paprastas, todėl reikia metodikos, kaip aprašyti dalykinę sritį ontologijų kalba, kad ji būtų realizuojama interneto portale, atitiktų vartotojų poreikius ir ontologijų kokybės kriterijus. Šio magistrinio darbo tikslas yra padidinti semantinių portalų kūrimo galimybes sudarant ir praktiškai išbandant metodiką, pagal kurią portalų kūrėjai galėtų kurti semantinius portalus, panaudodami dalykinės srities ontologiją. Darbe aprašyta ontologija grindžiamo portalo kūrimo metodika, kuri glaudžiai susijusi su dalykinės srities ontologijos sudarymo procesu; panaudotos ontologijos modelio saugojimo reliacinėje duomenų bazėje galimybės, atliktas ontologijos savybių rodiklių skaičiavimas. / Web portals collects the information scattered on the internet and organizes it for easy search and access. Current Web technologies employed to build up these portals present serious limitations regarding information search, access, extraction, interpretation and processing. The Semantic Web provides a common framework that allows data to be shared, reused and processed directly and indirectly by machines. To facilitate this process, OWL have been developed as standard formats for the sharing and integration of data in the form of rich conceptual schemas called ontologies. An ontology defines a common vocabulary for researchers who need to share information in a specific domain. There are several methods for facilitating development of ontologies. Although, neither describes how to build a Semantic Web portals step by step, using the latest Web portals development tools and technologies. The main goal of this work is to propose a development methodology for building Semantic Web portals from the scratch.

Šis darbas aprašo, atsižvelgiant į Lietuvos Respublikos teisės aktų reikalavimus ir vartotojų poreikius, sukurtą darbo laiko apskaitos žiniaraščio portalą ir su juo susijusią duomenų bazę, bei peržvelgia esančius analogiškus produktus. / Depending on the laws of the Republic of Lithuania requirements and the needs of users, the time sheets portal is made-up by this work and related database and the analogous products are reviewed.

Intensity modulated radiation therapy (IMRT) and volumetric modulated arc therapy (VMAT) have been introduced in radiation therapy to achieve highly conformal dose distributions around the tumour while minimizing dose to surrounding normal tissues. These techniques have increased the need for comprehensive quality assurance tests, to verify that customized patient treatment plans are accurately delivered during treatment. In vivo dose verification, performed during treatment delivery, confirms that the actual dose delivered is the same as the prescribed dose, helping to reduce treatment delivery errors. In vivo measurements may be accomplished using entrance or exit detectors. The objective of this project is to investigate a novel entrance detector designed for in vivo dose verification. This thesis is separated into three main investigations, focusing on a prototype entrance transmission detector (TRD) developed by IBA Dosimetry, Germany. First contaminant electrons generated by the TRD in a 6 MV photon beam were investigated using Monte Carlo (MC) simulation. This study demonstrates that modification of the contaminant electron model in the treatment planning system is required for accurate patient dose calculation in buildup regions when using the device. Second, the ability of the TRD to accurately measure dose from IMRT and VMAT was investigated by characterising the spatial resolution of the device. This was accomplished by measuring the point spread function with further validation provided by MC simulation. Comparisons of measured and calculated doses show that the spatial resolution of the TRD allows for measurement of clinical IMRT fields within acceptable tolerance. Finally, a new general research tool was developed to perform MC simulations for VMAT and IMRT treatments, simultaneously tracking dose deposition in both the patient CT geometry and an arbitrary planar detector system, generalized to handle either entrance or exit orientations. It was demonstrated that the tool accurately simulates dose to the patient CT and planar detector geometries. The tool has been made freely available to the medical physics research community to help advance the development of in vivo planar detectors. In conclusion, this thesis presents several investigations that improve the understanding of a novel entrance detector designed for patient in vivo dosimetry.

Radiation therapy is continuously increasing in complexity due to technological innovation in delivery techniques, necessitating thorough dosimetric verification. Comparing accurately predicted portal dose images to measured images obtained during patient treatment can determine if a particular treatment was delivered correctly. The goal of this thesis was to create a method to predict portal dose images that was versatile and accurate enough to use in a clinical setting. All measured images in this work were obtained with an amorphous silicon electronic portal imaging device (a-Si EPID), but the technique is applicable to any planar imager. A detailed, physics-motivated fluence model was developed to characterize fluence exiting the linear accelerator head. The model was further refined using results from Monte Carlo simulations and schematics of the linear accelerator. The fluence incident on the EPID was converted to a portal dose image through a superposition of Monte Carlo-generated, monoenergetic dose kernels specific to the a-Si EPID. Predictions of clinical IMRT fields with no patient present agreed with measured portal dose images within 3% and 3 mm. The dose kernels were applied ignoring the geometrically divergent nature of incident fluence on the EPID. A computational investigation into this parallel dose kernel assumption determined its validity under clinically relevant situations. Introducing a patient or phantom into the beam required the portal image prediction algorithm to account for patient scatter and attenuation. Primary fluence was calculated by attenuating raylines cast through the patient CT dataset, while scatter fluence was determined through the superposition of pre-calculated scatter fluence kernels. Total dose in the EPID was calculated by convolving the total predicted incident fluence with the EPID-specific dose kernels. The algorithm was tested on water slabs with square fields, agreeing with measurement within 3% and 3 mm. The method was then applied to five prostate and six head-and-neck IMRT treatment courses (~1900 clinical images). Deviations between the predicted and measured images were quantified. The portal dose image prediction model developed in this thesis work has been shown to be accurate, and it was demonstrated to be able to verify patients’ delivered radiation treatments.

In addition to the lonely battles fought by Bomber Command crews in the night skies over Germany from February 1942 to May 1945 there was an equally intense if much less bloody struggle in the halls of power between the Air Staff and the AOC Bomber Command, concerning the best employment of the strategic bomber forces. The argument of this study is that the Royal Air Force s contribution to the strategic air offensive was badly mismanaged: that Air Chief Marshal Sir Arthur Harris, Air Officer Commanding-in-Chief Bomber Command, from 22 February 1942 to the end of the war, by ignoring, or often over-riding the Air Staff, affected not only the course but also the duration of the Second World War. Most histories of the bomber war provide the result of the disagreements between the Chief of the Air Staff, Marshal of the Royal Air Force Sir Charles Portal and Harris, but rarely are the problems discussed in detail. This thesis examines the arguments that were raised by the various authorities, together with the refutations presented not only by the major participants, but also by the advisers to those authorities. The significant feature of the disagreements was that while Harris acted unilaterally, the Air Staff reached consensus decisions. Unfortunately, the decisions reached by the Air Staff on major issues were all too frequently either ignored or subverted by the AOC Bomber Command. One significant feature of the refutations presented to Harris was their dependence on the operational experience gained earlier in the bomber war by junior members of the Air Staff. For too long the direction of the war had been left in the hands of senior officers whose previous service had become irrelevant to war requirements in the 1940s. By 1942, comparatively junior officers were thus tendering advice to senior officers who, in the case of AOC Bomber Command, resented the authority which, Harris argued, had apparently been accorded these juniors. Harris was unable to accept that they were advisers and were never in a position to issue orders: orders could only come from Portal. Finally, this thesis provides an analysis of the strengths and weaknesses of the major participants and argues that, had the war been conducted as the Air Staff required, victory would have been achieved earlier than May 1945.

Öffentliche Bibliotheken stehen bei der Erfüllung ihres gesellschaftlichen Informationsund Bildungsauftrages in einer hochtechnisierten Wissensgesellschaft vor ganz neuen Herausforderungen. Die Bibliotheksentwicklungskonzeption (BEK) der Leipziger Städtischen Bibliotheken (LSB) ist Grundlage für Qualität und Quantität der Bibliotheksarbeit und reagiert in ihren regelmäßigen Fortschreibungen auf aktuelle Entwicklungen. Festgeschrieben sind darin auch der Ausbau der Online-Angebote und die Förderung des lebenslangen Lernens.

Am 9. Mai eröffnete Staatssekretär Dr. Knut Nevermann beim Sächsischen Bibliothekarstag in Schloss Forderglauchau das Bibliotheksportal Sachsen.

Intensity modulated radiation therapy (IMRT) and volumetric modulated arc therapy (VMAT) have been introduced in radiation therapy to achieve highly conformal dose distributions around the tumour while minimizing dose to surrounding normal tissues. These techniques have increased the need for comprehensive quality assurance tests, to verify that customized patient treatment plans are accurately delivered during treatment. In vivo dose verification, performed during treatment delivery, confirms that the actual dose delivered is the same as the prescribed dose, helping to reduce treatment delivery errors. In vivo measurements may be accomplished using entrance or exit detectors. The objective of this project is to investigate a novel entrance detector designed for in vivo dose verification. This thesis is separated into three main investigations, focusing on a prototype entrance transmission detector (TRD) developed by IBA Dosimetry, Germany. First contaminant electrons generated by the TRD in a 6 MV photon beam were investigated using Monte Carlo (MC) simulation. This study demonstrates that modification of the contaminant electron model in the treatment planning system is required for accurate patient dose calculation in buildup regions when using the device. Second, the ability of the TRD to accurately measure dose from IMRT and VMAT was investigated by characterising the spatial resolution of the device. This was accomplished by measuring the point spread function with further validation provided by MC simulation. Comparisons of measured and calculated doses show that the spatial resolution of the TRD allows for measurement of clinical IMRT fields within acceptable tolerance. Finally, a new general research tool was developed to perform MC simulations for VMAT and IMRT treatments, simultaneously tracking dose deposition in both the patient CT geometry and an arbitrary planar detector system, generalized to handle either entrance or exit orientations. It was demonstrated that the tool accurately simulates dose to the patient CT and planar detector geometries. The tool has been made freely available to the medical physics research community to help advance the development of in vivo planar detectors. In conclusion, this thesis presents several investigations that improve the understanding of a novel entrance detector designed for patient in vivo dosimetry.

Radiation therapy is continuously increasing in complexity due to technological innovation in delivery techniques, necessitating thorough dosimetric verification. Comparing accurately predicted portal dose images to measured images obtained during patient treatment can determine if a particular treatment was delivered correctly. The goal of this thesis was to create a method to predict portal dose images that was versatile and accurate enough to use in a clinical setting. All measured images in this work were obtained with an amorphous silicon electronic portal imaging device (a-Si EPID), but the technique is applicable to any planar imager. A detailed, physics-motivated fluence model was developed to characterize fluence exiting the linear accelerator head. The model was further refined using results from Monte Carlo simulations and schematics of the linear accelerator. The fluence incident on the EPID was converted to a portal dose image through a superposition of Monte Carlo-generated, monoenergetic dose kernels specific to the a-Si EPID. Predictions of clinical IMRT fields with no patient present agreed with measured portal dose images within 3% and 3 mm. The dose kernels were applied ignoring the geometrically divergent nature of incident fluence on the EPID. A computational investigation into this parallel dose kernel assumption determined its validity under clinically relevant situations. Introducing a patient or phantom into the beam required the portal image prediction algorithm to account for patient scatter and attenuation. Primary fluence was calculated by attenuating raylines cast through the patient CT dataset, while scatter fluence was determined through the superposition of pre-calculated scatter fluence kernels. Total dose in the EPID was calculated by convolving the total predicted incident fluence with the EPID-specific dose kernels. The algorithm was tested on water slabs with square fields, agreeing with measurement within 3% and 3 mm. The method was then applied to five prostate and six head-and-neck IMRT treatment courses (~1900 clinical images). Deviations between the predicted and measured images were quantified. The portal dose image prediction model developed in this thesis work has been shown to be accurate, and it was demonstrated to be able to verify patients’ delivered radiation treatments.

A technique for the in vivo dose verification of intensity modulated radiation therapy (IMRT) has been developed. An electronic portal image, calibrated in terms of absolute dose, is acquired for each radiation field following transmission through the patient at the time of treatment. For an IMRT field, the portal image signal is back-projected through a model of the patient in order to calculate the dose at the isocentric plane perpendicular to the beam central axis. The IMRT in vivo dose verification technique was adapted for volumetric modu- lated arc therapy (VMAT) treatments when a single dosimetric image is acquired over an arc. The patient dose along axis of gantry rotation can be directly related to the signal along the vertical axis of EPIs in integrated mode. In this novel VMAT in vivo dosimetry technique, the portal image signal is back-projected through a rotationally averaged model of the patient to calculate a 1D in vivo dose along the axis of gantry rotation. A research ethics board clinical study was approved and transmission portal images were acquired at regular intervals from human subjects. Portal image-derived isocenter point doses were in good agreement with treatment planning system (TPS) calculations for IMRT (mean difference δ=0.0%, standard deviation of the differences σ=4.3%) and VMAT (δ=1.1%, σ=1.7%). The one-dimensional (VMAT) and two-dimensional (IMRT) reconstructed doses were further analyzed by calculating mean dose differences and γ−evaluation pass-rates, which were also shown to be in good agreement with TPS calculations. The portal image-based in vivo dosimetry techniques were shown to be clinically feasible, with reconstruction times on the order of minutes for the first fraction and less than one minute for each fraction thereafter. / Graduate / 0760 / 0574 / 0760