During the last decades radiotherapy has made major improvements in accuracy and individualization of the treatment techniques. In this project the thickness of a tungsten filter has been optimized using both simulations and experiments in order to further reduce the uncertainty in the dose given to the patient. With the filter, a dosage with less uncertainty can be obtained and less electrons will strike the patient which means less skin damage. In the simulations a program called PENELOPE, has been used which uses Monte Carlo methods for electron and photons transports. The experiment has been done on real Linear Accelerators.

An inspection system was required in order to eliminate the difficulties which appear during the inspection of the vehicles according to specific criteria at Turkish Custom Border in a short time and effectively. In this thesis, we performed experiments on such a system to obtain the overall performance of its inspection quality. We firstly give with reasons, why the source of beam is selected as X-ray source. The subsystems of the main system are the accelerator subsystem and detector subsystem. Their structures and working principles are studied in detail by comparing them with their alternatives. Series of experiments are carried out to verify the general performance of system in terms of radiation security and quality of images produced by the system. These experiments were classified as general scan experiment, inspection performance experiment, image quality indicator experiment, radiation safety experiment and general performance experiment. The container inspection system studied and experimented in this thesis is now used effectively in Turkish Customs Boarder, Edirne Kapikule and Edirne ipsala.

Accurate measures of both clinical image quality and patient radiation risk are needed for successful optimisation of medical imaging with ionising radiation. Optimisation in diagnostic radiology means finding the image acquisition technique that maximises the perceived information content and minimises the radiation risk or keeps it at a reasonably low level. The assessment of image quality depends on the diagnostic task and may in addition to system and quantum noise also be hampered by overlying projected anatomy. The main objective of this thesis is to develop methods for assessment of image quality in simulations of projection radiography. In this thesis, image quality is quantified by modelling the whole x‐ray imaging system including the x‐ray tube, patient, anti‐scatter device, image detector and the observer. This is accomplished by using Monte Carlo (MC) simulation methods that allow simultaneous estimates of measures of image quality and patient dose. Measures of image quality include the signal‐to‐noise‐ratio, SNR, of pathologic lesions and radiation risk is estimated by using organ doses to calculate the effective dose. Based on high‐resolution anthropomorphic phantoms, synthetic radiographs were calculated and used for assessing image quality with model‐observers (Laguerre‐Gauss (LG) Hotelling observer) that mimic real, human observers. Breast and particularly chest imaging were selected as study cases as these are particularly challenging for the radiologists. In chest imaging the optimal tube voltage in detecting lung lesions was investigated in terms of their SNR and the contrast of the lesions relative to the ribs. It was found that the choice of tube voltage depends on whether SNR of the lesion or the interfering projected anatomy (i.e. the ribs) is most important for detection. The Laguerre‐Gauss (LG) Hotelling observer is influenced by the projected anatomical background and includes this into its figure‐of‐merit, SNRhot,LG. The LG‐observer was found to be a better model of the radiologist than the ideal observer that only includes the quantum noise in its analysis. The measures of image quality derived from our model are found to correlate relatively well with the radiologist’s assessment of image quality. Therefore MC simulations can be a valuable and an efficient tool in the search for dose‐efficient imaging systems and image acquisition schemes.

In dieser Arbeit wird die Signalanalyse eines Ortsdosisleistungsmessgerät mit organischem Szintillatoren der Arbeitsgruppe Strahlungsphysik optimiert, damit die Signalanalyse die Anforderungen der PTB im Hinblick auf eine Baumusterprüfung erfüllt. Dafür wird der Mittellungszeitraum der Dosisleistung dynamisch an die Zählrate angepasst, um einen Kompromiss zwischen schneller Ansprechzeit und geringer statistischer Messunsicherheit der gemessenen Dosisleistungen zu erreichen. Bei hohen Zählraten wird die Datenmenge begrenzt, damit die CPU nicht mit der Auswertung der Einzelereignisse überlastet wird. Weiterhin wird für 2 Prototypen des Dosimeters eine Energiekalibrierung und Wichtung gefunden. Als zusätzliches Feature ist eine Fourier-Transformation implementiert, mit der die Frequenz von gepulster Strahlung bestimmt wird.:Inhaltsverzeichnis 1 Motivation 1 2 Physikalischer Hintergrund 3 2.1 Dosis 3 2.2 Kernreaktionen 3 2.3 Wechselwirkung zwischen Strahlung und Materie 4 2.4 Detektoren 6 3 Material und Methoden 9 3.1 Aufbau und Funktionsweise 9 3.2 Funktionsprüfung 13 3.3 Kalibrierung 15 3.4 Anforderungen der PTB 18 3.5 Überlastungsschutz 19 3.6 Fourier-Transformation 20 4 Messungen 23 4.1 Messung mit dem Pulsgenerator 23 4.2 Messungen mit dem NaI-Szintillator 25 4.3 Messungen mit organischem Szintillator 27 5 Zusammenfassung 41 6 Anhang 43 6.1 Beobachtete Röntgen und γ-Linien 43 6.2 Pulsladungshistogramme 44 Abbildungsverzeichnis 53 Tabellenverzeichnis 55 Literatur 57 / In this thesis, the signal analysis of a local dose rate measurement device is improved for a type examination at the PTB. For this the averaging time of the dose rate measurement is dynamically optimized to archive a trade-off between a short reaction time and low statistical uncertainty of the measured dose rate in order to fulfil the expectations of the PTB and an overload protection is added to ensure a swift analysis of the incoming events even at high count rates. Furthermore, an energy calibration and weight is determined for two prototypes of the dose rate measurement device. As an additional feature a Fourier transformation is implemented to determine the frequency of pulsed radiation fields.:Inhaltsverzeichnis 1 Motivation 1 2 Physikalischer Hintergrund 3 2.1 Dosis 3 2.2 Kernreaktionen 3 2.3 Wechselwirkung zwischen Strahlung und Materie 4 2.4 Detektoren 6 3 Material und Methoden 9 3.1 Aufbau und Funktionsweise 9 3.2 Funktionsprüfung 13 3.3 Kalibrierung 15 3.4 Anforderungen der PTB 18 3.5 Überlastungsschutz 19 3.6 Fourier-Transformation 20 4 Messungen 23 4.1 Messung mit dem Pulsgenerator 23 4.2 Messungen mit dem NaI-Szintillator 25 4.3 Messungen mit organischem Szintillator 27 5 Zusammenfassung 41 6 Anhang 43 6.1 Beobachtete Röntgen und γ-Linien 43 6.2 Pulsladungshistogramme 44 Abbildungsverzeichnis 53 Tabellenverzeichnis 55 Literatur 57

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Scattered x-radiation levels associated with various diagnostic procedures were measured with ionization chamber instruments in the small and large animal radiology facilities at the Ontario Veterinary College of the University of Guelph. The occupational radiation exposures incurred by veterinary radiography personnel were monitored using McMaster University's Panasonic UD-702E TLD system. The stray radiation levels and the dosimetric information are compared and discussed. An optimum protocol for radiological health protection surveillance is described. / Thesis / Master of Science (MSc)

Thesis (Ph.D.); Submitted to North Carolina State Univ., Raleigh, NC (US); 6 Apr 2005. / Published through the Information Bridge: DOE Scientific and Technical Information. "UCRL-TH-211400" Dashdorj, D. 04/06/2005. Report is also available in paper and microfiche from NTIS.

Thesis (Ph.D.); Submitted to the University of California Berkeley, Berkeley, CA (US); 1 Jun 2004. / Published through the Information Bridge: DOE Scientific and Technical Information. "LBNL--56278" Burke, Jason Timothy. USDOE Director. Office of Science. Office of High Energy and Nuclear Physics. Division of Nuclear Physics (US) 06/01/2004. Report is also available in paper and microfiche from NTIS.

Doctoral Dissertation, Ph.D., University of California, Berkeley, Berkeley, California, USA. / Published through the Information Bridge: DOE Scientific and Technical Information. "LBNL--56749" Folden III, Charles Marvin. USDOE Director. Office of Science. Office of Nuclear Physics 11/04/2004. Report is also available in paper and microfiche from NTIS.

Thesis (Ph.D.); Submitted to Univ. of California, Berkeley, CA (US); 1 Jun 2003. / Published through the Information Bridge: DOE Scientific and Technical Information. "LBNL--54350" Scielzo, Nicholas David. USDOE Director. Office of Science. Nuclear Physics (US) 06/01/2003. Report is also available in paper and microfiche from NTIS.