A theoretical and experimental study of the spatial spread of electron dose distributions for pencil and broad electron beams in various media is presented. We discuss in detail two methods for measurement of electron beam kinetic energies, describe our technique for the measurement of the optical density versus dose relationship for radiographic films, and present the experimental set-up for the measurement of the spatial spread of electron dose distributions for pencil and broad electron beams. / The Fermi-Eyges theory for the small angle multiple Coulomb scattering describes the spatial electron distribution in scattering media. The spatial spread of a pencil electron beam in a phantom as predicted by the Fermi-Eyges theory is an increasing function of depth in phantom irrespective of the depth. Our experiments, on the other hand, show that the spatial spread indeed increases with depth until depths close to 2/3 of the practical electron range, but at larger depths the spatial spread saturates, then decreases and vanishes at depths greater than the range of electrons in the material. To describe the observed saturation and the decrease of the spatial spread at depths beyond 2/3 of the practical electron range we introduce an electron absorption term containing four empirical parameters into the original Fermi differential equation and show that its solution describes the experimental results obtained for pencil electron beams of various energies in polystyrene, cork and aluminum phantoms. We also compare with experimental results the spatial electron dose distributions predicted by the Fermi-Eyges theory and the modified Fermi-Eyges theory for collimated broad electron beams.

The block effect in Positron Emission Tomography (PET) is the degradation in spatial resolution that is seen when there are more scintillation crystals than photomultiplier tubes in a detector. / We measured the block effect in detectors from three PET scanners: the Siemens-CTI HR+, the GE Advance, and the Siemens-CTI HI-REZ. In the CTI HR+ the block effect was 0.7 mm in the central crystals, and negligible for the edge crystals. In the GE Advance the block effect was 0.6 mm for the central crystals, and 0.5 mm for the edge crystals. In the CTI HI-REZ detector the block effect varied from 0.5 mm to 2.1 mm depending on the crystal location. / The effect of changing the depth of the first point of gamma-ray interaction in the block detectors was examined. The gamma-ray interaction depth was varied, and the event position in the crystal identification image was examined. If the events were positioned inconsistently with gamma-ray interaction depth, this might be a cause of the block effect. / In the CTI HR+ detector and the CTI HI-REZ detector, the positioning of events in the crystal identification image was dependent both on the crystal depth of the first point of interaction and the crystal location. In the GE Advance block detector the positioning of events in the crystal identification image was consistent for varying gamma-ray interaction depth, and crystal position. / In crystals where the positioning of events is not consistent with interaction depth, the block effect is larger. In the GE Advance block detector, another cause of the block effect may exist.

The purpose of this thesis project was to assess the value of chest radiographs as a screening tool for the diagnosis of diffuse idiopathic skeletal hyperostosis (DISH). Two "gold standard" physicians identified 45 DISH patients and 106 control patients (45 with thoracic spondylosis, 45 with "normal" spines, and 16 with ankylosing spondylitis). The chest x-rays on the 151 subjects were randomized and read independently using an ordinal diagnostic certainty scale by two "test" radiologists, experienced in reading bone radiographs. The average results for the two test radiologists were: sensitivity = 77%; specificity = 97%; positive predictive value = 91%; and, negative predictive value = 91%. The area under the receiver operating characteristic curves was 0.975 and 0.976 for the radiologists, respectively, suggesting that inter-rater reliability was very high. A second reading showed that the intra-rater reliability was exceptional (weighted kappa of 0.90 and 0.96 for the two "test" radiologists). DISH patients whose chest x-rays were read as not demonstrating DISH had significantly less extensive disease. We conclude that chest x-rays are a reliable and valid screening tool for the diagnosis of DISH.

A commercial electron dose calculation software (Eclipse TM) implementation based on the Macro Monte Carlo algorithm has been introduced. Eclipse™ initial configurations were performed for all available electron beam energies 6, 9, 12, 16, and 20 MeV. We evaluated the electron Monte Carlo (eMC) module of the Eclipse™ using a verification data set comprised of depth dose curves, profiles, Relative Output Factors (ROF), and 2-0 dose distributions in the transverse plane in a homogeneous phantom. The verification data set was comprised of measurements performed for combinations of 6, 9, 12, 16, and 20 MeV beam energies with five standard field sizes and thirteen irregularly shaped fields under three phantom setups. The phantom setups were normal beam incidence at source-to-surface distance (SSO) = 100cm, normal incidence with extended SSO=11 Ocm, and oblique incidence with extended SSO=11 Ocm. Calculations were performed in a digital phantom with the maximum number of particles accepted by Eclipse ™ with a grid spacing that was no larger than approximately one-tenth the distal falloff distance of the electron depth dose curve from 80% to 20% of the maximum dose. Overall, the agreement between the calculated dose distributions and measured on es was good for fields larger than 2 cm to better than 3% dose difference and 3 mm distance-to-agreement.

It is standard practice in radiation therapy to have two independent calculations for the number of monitor units used in patient treatment plans. The relationship between monitor units and absorbed dose to water is sophisticated for MLC-based IMRT. Verification measurements of absorbed dose to water with ionization chambers in MLC-based IMRT fields remains uncertain and the accuracy of computer modeling is limited by the physics assumptions used. In this thesis, point dose measurements from three cylindrical ionization chambers of different collecting volumes are evaluated against the CORVUS (NOMOS Corporation, Cranberry, PA) finite-size pencil beam algorithm and the PEREGRINE (NOMOS Corporation, Cranberry, PA) Monte Carlo calculation engine. After establishing the characteristics of the chambers and treatment planning system under various beam geometries, dynamic and step and shoot MLC deliveries were evaluated. Between detectors, the smallest volume chamber measured the greatest dose. Compared to measurements, CORVUS and PEREGRINE both underestimated the dose in IMRT fields by approximately 5%. On average PEREGRINE yielded better agreement than CORVUS by 2%.

Thesis (Ph.D.)--University of California, San Francisco with the University of California, Berkeley, 2009. / Source: Dissertation Abstracts International, Volume: 70-10, Section: B, page: 6384. Advisers: David Saloner; Mohammad R.K. Mofrad.

This dissertation examines the history of modern Japan via a study of rentogen, or X-rays, in medical practice. Conventional milestones in Japan’s encounters with nuclear science all date from 1945: the atomic bombings of Hiroshima and Nagasaki that same year, the Bikini Atoll fallout incident in 1954, the construction of nuclear power plants from the late 1950s onwards, and most recently, the Fukushima Daiichi meltdown in 2011. All these events produced hibakusha – the Japanese term for survivors of nuclear-related accidents, or people suffering the effects of exposure to ionising radiation. In contrast, this project locates the first hibakusha in an earlier period, revealing a history of radiation exposure in Japan before the atomic bombings. It reaches into the late nineteenth and early twentieth centuries to find Japanese bodies exposed through the development of radiology. In modern Japan, as in Western Europe and America, X-rays constituted the first source of ionizing radiation that produced victims of burns, cancers, and deaths. This study highlights the political, social and cultural impact of modern Western medicine on Japanese society from the Meiji period onwards, showing how electric-powered machines and Western expertise came to define medical practice in the emergent field of radiology. / East Asian Languages and Civilizations

Background. Standard traditional parameters relied on for estimating the risk of disease recurrence after curative radiotherapy in prostate cancer are stage, Gleason score and PSA. Objectives. To elucidate the prognostic role of biomarkers: P-53, MIB-1, MVD, Bax and BCL2 in prostate cancer. Method. Cox proportional hazard model was used to estimate the risk of disease progression associated with these biomarkers and develop models based on traditional parameters only or incorporating biomarkers. Models were compared for their predictive potential using Akaike information criteria and concordance index. Results. Statistically significant associations were found between all biomarkers and risk of progression. MVD, Bax and Bax/BCL2 were independent predictors of outcome. Models incorporating biomarkers were superior to the traditional one in identifying patients at risk of local progression. Conclusions. Biomarkers may be useful in forecasting the risk of local recurrence following radiotherapy in prostate cancer patients. The results require validation in a separate cohort.

Problem. After two years of operation a review of the Rapid Palliative Radiotherapy Program revealed that only 17 family physicians in Eastern Ontario had used the program. Methods of investigation. This thesis consists of: (1) A systematic literature review of the relative effectiveness of a single fraction of radiotherapy to relieve painful bone metastases and (2) A survey of family physicians to assess their awareness of the Rapid Palliative Radiotherapy Program. Results. A single fraction of radiotherapy is of comparable effectiveness to multiple fraction radiotherapy treatment schedules in relieving painful metastatic bone disease (Odds Ratio: 1.13, 95% CI = 0.96 to 1.34). Only 18% of survey responders were aware of the RPRP. Conclusion. Improving family physician awareness of the Rapid Palliative Radiotherapy Program is the first step to improving utilization of the program and access for patients with painful metastatic bone disease to a proven, effective analgesic treatment.

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