Thesis (Ph. D.)--University of Texas at Austin, 2000. / Vita. Includes bibliographical references (leaves 263-280). Available also in a digital version from Dissertation Abstracts.

Os órgãos de saúde internacionais e nacionais, como o Ministério da Saúde na portaria 453/98 da Vigilância Sanitária, exigem que a Dose de Entrada na Pele seja avaliada para cada equipamento mamográfico através da leitura de um sistema câmara de ionização-eletrómetro corrigida pelo fator de retroespalhamento. Ao não existir menção explícita na portaría de valores utilizáveis para o fator de retroespalhamento, este trabalho visa à determinação experimental do fator de retroespalhamento, através da utilização dos dosímetros termoluminescentes TLD-100. No estudo são verificadas as dependências geométricas e espectrais do fator de retroespalhamento, assim como do valor da Dose de Entrada na Pele, e da Dose em Profundidade, correspondentes com as técnicas radiográficas empregadas nos exames mamográficos convencionais de rotina. Foram avaliados feixes na faixa de 0,35 mmAl até 0,43 mmAl, tensões do tubo de 25kV, 28kV, 30kV, e 32kV, assim como os três tamanhos de campo disponíveis no Mamógrafo Senographe DMR utilizado, e distancias focofilme iguais a 56cm, 61cm e 66cm. Os resultados obtidos foram comparados com publicações existentes, as quais apresentam resultados obtidos através de Simulação Monte Carlo, câmaras de ionização, e dosímetros TLD-100. Os resultados obtidos neste trabalho permitem estabelecer e discutir as dependências das grandezas dosimétricas estudadas com a Camada Semi-Redutora, tensão do tubo, combinação ânodo-filtro, tamanho de campo, distância foco-filme e espessura da mama. / National and international health organizations such as the Brazilian Ministry of Health, through its Secretary of Health Surveillance establishes in the publication Nº 453/98 that in all mammographic equipments must be evaluated the entrance-skin dose through the readings of an ionization chamber-electrometer system corrected by the backscatter factor, among others factors. Nevertheless, there is no explicit mention for useful values of backscatter factor in this document; the main aim of this work is the experimental determination of backscatter factor through the use of TLD-100 dosimeters. In this study, the geometric and spectral dependencies of the backscatter factor, entrance-skin dose and the in-depth dose were evaluated, corresponding to the most radiographic techniques employed in conventional mammographic procedures, i.e., beam qualities in the range of 0.35 mmAl to 0.43 mmAl, tube voltages from 25kV to 32kV, focus-film distances from 56cm to 66cm, and three field sizes were evaluated. Our results were compared with those previously published obtained through Monte Carlo simulation, ionization chambers and TLD dosimeters. The results obtained in this work allow studying the dependency of the mentioned dosimetric quantities with the half-value layer, tube voltage, anode-filter combination, field size, focusfilm distance and breasting thickness of the breast.

Class of 2012 Abstract / Specific Aims: The primary aim of this study was to determine the incidence of posaconazole and voriconazole concentration monitoring that occurs in transplant patients receiving antifungal prophylaxis therapy. The secondary aim was to determine whether voriconazole and posaconazole serum concentrations were used for dose adjustments. Methods: Patients status post either a liquid or solid organ transplant over the age of 1 year who received invasive fungal infection prophylaxis with either posaconazole or voriconazole between the dates of February 1, 2010 through January 31, 2011 while admitted to academic medical center were included in this descriptive retrospective study. This study has been approved by the Institutional Review Board. Data collected on each subject included demographic information, type of transplant, posaconazole or voriconazole concentrations, and duration and dosage adjustments. Main Results: 54 subjects were identified who received either voriconazole or posaconazole for fungal prophylaxis after transplant. For subjects who were prescribed posaconazole (N = 8), concentration monitoring was performed in 50% of subjects and 0% of posaconazole dose adjustments were based on concentrations. For subjects who were prescribed voriconazole, concentration monitoring and dose adjustments based on voriconazole concentrations were performed in 20% and 78% of subjects respectively. Adverse outcomes associated with the use of antifungal therapy were reported in 0% of the posaconazole therapy group and 17% of the voriconazole therapy group. Conclusions: Both posaconazole and voriconazole concentrations were obtained from patients who were receiving antifungal therapy for invasive fungal infection prophylaxis. Adjustments of prophylactic doses are not well characterized.

No / The aim of this research was to optimize x-ray image quality to dose ratios in the cardiac catheterization laboratory. This study examined independently the effects of peak x-ray tube voltage (kVp), copper (Cu), and gadolinium (Gd) x-ray beam filtration on the image quality to radiation dose balance for adult patient sizes. Methods: Image sequences of polymethyl methacrylate (PMMA) phantoms representing two adult patient sizes were captured using a modern flat panel detector based x-ray imaging system. Tin and copper test details were used to simulate iodine-based contrast medium and stents/guide wires respectively, which are used in clinical procedures. Noise measurement for a flat field image and test detail contrast were used to calculate the contrast to noise ratio (CNR). Entrance surface dose (ESD) and effective dose measurements were obtained to calculate the figure of merit (FOM), CNR2/dose. This FOM determined the dose efficiency of x-ray spectra investigated. Images were captured with 0.0, 0.1, 0.25, 0.4, and 0.9 mm Cu filtration and with a range of gadolinium oxysulphide (Gd2O2S) filtration. Results: Optimum x-ray spectra were the same for the tin and copper test details. Lower peak tube voltages were generally favored. For the 20 cm phantom, using 2 Lanex Fast Back Gd2O2S screens as x-ray filtration at 65 kVp provided the highest FOM considering ESD and effective dose. Considering ESD, this FOM was only marginally larger than that from using 0.4 mm Cu at 65 kVp. For the 30 cm phantom, using 0.25 mm copper filtration at 80 kVp was most optimal; considering effective dose the FOM was highest with no filtration at 65 kVp. Conclusions: These settings, adjusted for x-ray tube loading limits and clinically acceptable image quality, should provide a useful option for optimizing patient dose to image quality in cardiac x-ray imaging. The same optimal x-ray beam spectra were found for both the tin and copper details, suggesting that iodine contrast based imaging and visualization of interventional devices could potentially be optimized for dose using similar x-ray beam spectra.

For nearly forty years diethylstilbestrol (DES) was administered to pregnant women to maintain healthy pregnancies. During this time, it is estimated that several million men and women have been exposed to DES during sometime of their life. The most common period of exposure was during fetal development. Although rarely used for the maintenance of pregnancy now, its current medical use is restricted to certain clinical situations such as breast and prostate cancer therapies in adults. Thus, DES exposure spans the entire lifetime, from prenatal to geriatric age. Since the early 1950s, health risks were beginning to be associated with prenatal DES treatment. So far only reproductive problems such as infertility, neoplastic diseases of the cervix and vagina and testicular cancers have been well-documented in DES cases. Immunological abnormalities associated with DES are only now beginning to be recognized. Self-reported cases and questionnaire-based studies have revealed increased incidence of infections and autoimmune diseases in DES exposed people. Animal studies that have examined the immunological effects of DES treatment are largely restricted to one gender, or to one dose of DES or to the developmental period. This is an important issue since human exposure to DES occurred in both men and women, at all ages and, at a wide-range of doses. The purpose of these studies was to investigate the immunological consequences resulting from the exposure to DES. Since sensitivity can vary between genders, dose and at the time of exposure, it is critical to investigate the DES-induced immunological changes during all stages of life in both genders. To address these critical gaps in the literature, we examined the immunomodulatory effects of adult and prenatal exposure to DES in males and females. Our findings show that DES effects were evident in both the thymus and spleen. DES markedly affected the apoptosis of thymocytes and the ability of splenic lymphocytes to proliferate in response to stimulants and secrete vital cytokines such as interferon-gamma. Our notable findings were that in-utero exposure to DES resulted in profound alterations in lymphocyte functionality, which were noticed as late as one-year of age. This suggests that alterations to the in utero environment can have deleterious consequences that may be long lasting. These studies have profound implications to the humans and animals exposed to DES, and indirectly to a whole range of other estrogenic compounds. / Master of Science

Inom nuklearmedicin exponeras personal dagligen för joniserande strålning. Det kan vara både i form av en öppen strålkälla vid uppdrag av radiofarmaka och vid bildtagning där personalen hjälper och ger stöd till patienten som blivit injicerad. Vid uppdrag av radiofarmaka används strålskydd i form av sprutskydd och distansverktyg medan blyförkläde används vid kontakt med patienter. Dessa skydd är till för att minska skador som kan uppstå vid exponering. Den svenska strålsäkerhetsmyndigheten (SSM) har föreskrivit dosgränser som inte får överskridas för att minska risken för skador. Teknetium-99m (99mTc) är den vanligaste radionukliden inom den nuklearmedicinska verksamheten. Syftet med denna studie var att kartlägga strålningsexponeringen för personal som jobbar med 99mTc och på så sätt visa behovet av olika typer av strålskydd för att reducera stråldosen. I denna studie utfördes fingerdosmätningar vid uppdrag av 99mTc med hjälp av termoluminiscenta dosimetrar som placerades på de tre mest utsatta fingrarna, digitus I-III, bilateralt. Mätningarna genomfördes vid uppdrag utan strålskydd, med en pincett och med fullt strålskydd (sprutskydd samt två pincetter). Studien innefattar även stråldosmätningar med och utan blyförkläde för myokardscintigrafi, skelettscintigrafi och lungscintigrafi. Dessa mätningar utfördes med en direktavläsande personal electronic dosimeter (PED) där den effektiva dosen registrerades. Resultaten för fingerdosmätningarna visar en signifikant skillnad i stråldos beroende på om och vilket strålskydd som används. Högst dos fick de som drog upp helt utan strålskydd och vänster långfinger fick den högsta ekvivalenta dosen. För stråldosmätningarna med och utan blyförkläde utfördes ett Mann-Whitney U-test som visade ett p-värde på <0,05 vilket tyder på att det finns en statistisk signifikant skillnad. Högst effektiv dos uppmättes vid lungscintigrafi för personal som inte använde blyförkläde. / Personnel working with radiopharmaceuticals in the nuclear medicine department are exposed to radiation on the daily basis. The source of radiation can both be open as in the withdrawal procedure and external as when the patient has been injected and ready for imaging. There are different types of radiation protection depending on which task that is performed. Syringe shielding and distance tools are used during the withdrawal and lead aprons are used when positioning the patient under the camera. The Swedish radiation safety authority (SSM) prescribe dose limits to reduce any risk of injury connected to radiation. These limits must not be exceeded. Technetium-99m (99mTc) is the most common radiopharmaceutical in the nuclear medicine department. The purpose of this study was to study the radiation exposure to personnel working with 99mTc and evaluate the need for radiation protection to reduce the radiation dose. This study includes measurement of the equivalent dose to the three most exposed fingers, digitus I-III bilateral, during the withdrawal of 99mTc. Thermoluminiscent dosimeters was used to detect radiation and was placed on top of the finger. The measurements were performed without radiation shielding, with only one tweezer as distance tool and with full radiation shielding (syringe shielding and two tweezers as distance tools). It also includes measurement of the effective dose during myocardial scintigraphy, bone scan and lung scintigraphy with or without lead apron. For these measurements a personal electronic dosimeter was used to detect radiation. The result of the finger doses showed a significant difference in radiation dose depending on which protection was used. The highest dose was recovered from not using any protection at all and the highest equivalent dose was obtained by left middle finger. For the measurement regarding the effective dose with or without lead apron a Mann-Whitney U-test was performed and showed a p-value of <0,05 which indicates a statistical significant difference. The highest effective dose was recovered from lung scintigraphy when the personnel was not wearing a lead apron.

Submitted by Irene Nascimento (irene.kessia@ufpe.br) on 2017-03-21T19:51:42Z No. of bitstreams: 2 license_rdf: 1232 bytes, checksum: 66e71c371cc565284e70f40736c94386 (MD5) TESE FINAL versão digital.pdf: 2839254 bytes, checksum: 962b7ff83b975bcd276b612274de7368 (MD5) / Made available in DSpace on 2017-03-21T19:51:42Z (GMT). No. of bitstreams: 2 license_rdf: 1232 bytes, checksum: 66e71c371cc565284e70f40736c94386 (MD5) TESE FINAL versão digital.pdf: 2839254 bytes, checksum: 962b7ff83b975bcd276b612274de7368 (MD5) Previous issue date: 2016-08-15 / Facepe / Dentre os diversos procedimentos intervencionistas com fins terapêuticos, a quimioembolização hepática tem se destacado por ser de alta complexidade e resultar em altas doses de radiação aos pacientes e à equipe médica. Em alguns casos, o paciente requer várias sessões para tratar a mesma lesão, o que aumenta a probabilidade de ocorrência de lesões na pele e/ou efeitos estocásticos. Embora seja uma técnica altamente utilizada no Brasil, a quimioembolização não tem sido alvo de estudos dosimétricos. Este estudo apresenta os resultados da avaliação dosimétrica realizada na equipe médica e pacientes durante 109 procedimentos de quimioembolização hepática, realizados em seis serviços de hemodinâmica na cidade de Recife, Pernambuco. Os procedimentos foram realizados utilizando equipamentos de angiografia digital de diferentes fabricantes e tecnologias. A dosimetria dos pacientes foi caracterizada através das estimativas da máxima dose na pele (MDP), do produto kerma ar-área (PKA) e do kerma ar de referência (Ka,r). A MDP foi estimada a partir da utilização de filmes radiocrômicos do tipo Gafchromic XR RV3. Para avaliar o risco de efeitos estocásticos, foi estimada a dose absorvida em órgãos a partir de simulações Monte Carlo utilizando fantomas antropomórficos femininos e masculinos da serie FASH e MASH. Os resultados da dosimetria com filme radiocrômico mostraram valores da MDP variando de 180 a 5650 mGy; sendo que 40% dos pacientes apresentaram valores de dose na entrada da pele que ultrapassaram o limiar de dose para ocorrência de eritema transitório, que é de 2 Gy. O estudo das correlações entre a MDP, PKA e Ka,r mostrou que o Ka,r pode ser utilizado para avaliar a possibilidade de ocorrência de reações tissulares na pele dos pacientes submetidos a procedimentos de quimioembolização. Os resultados das simulações mostraram que alguns órgãos internos dos pacientes podem receber doses entre 500 mGy e 1 Gy. A dosimetria ocupacional foi realizada utilizando dosímetros termoluminescentes e dispositivos eletrônicos pessoais distribuídos em varias regiões do corpo dos profissionais. Os resultados mostraram que, com apenas uma quimioembolização por semana, o médico principal pode ultrapassar o limite anual de 20 mSv para o cristalino quando não são utilizados dispositivos de radioproteção como óculos ou telas de acrílico plumbíferos. O valor mais alto de equivalente de dose pessoal Hp(d) por procedimento medido no corpo do médico principal foi 5135,3 μSv no pé esquerdo. A ausência da cortina plumbífera durante a realização dos procedimentos é uma explicação para os valores altos registrados. Os valores médios de dose efetiva por procedimento para o médico principal, médico auxiliar e anestesista numa das instituições acompanhadas foram: 13 μSv, 6,1 μSv e 13,7 μSv, respectivamente. Estes resultados mostram que os níveis de exposição recebidos pelo anestesista em procedimentos de quimioembolização podem ser superiores aos do médico principal. Os resultados da dosimetria ocupacional com dosimetros eletrônicos mostraram que estes dispositivos podem ser utilizados de forma complementar na estimativa da dose ocupacional no cristalino em procedimentos de quimioembolização hepática. Nas seis instituições avaliadas observou-se uma alta variabilidade nos valores de dose no paciente e equipe médica, devido, principalmente, ao desempenho dos equipamentos, complexidade dos procedimentos, características físicas dos pacientes e experiência dos médicos. / Among interventional procedures, hepatic chemoembolization has been recognized as a complex procedure where high radiation doses to patients and medical staff are delivered. In some cases the patient has to endure several sessions to treat the same lesion, which increases even more the probability of skin injuries or stochastic effects. In Brazil, chemoembolization is widely used; however few dosimetric studies have been done so far. This study presents dosimetric results for medical staff and patients based on 109 hepatic chemoembolization procedures conducted in six hemodynamic departments in Recife, Pernambuco. The procedures were performed using digital angiography equipments from different manufacturers, using different technologies. Patient dosimetry comprised the measurement of the maximum skin dose (MSD), air kerma-area product (PKA) and reference air kerma (Ka,r). The MSD was measured using radiochromic films of type Gafchromic XR RV3. To assess the risk of stochastic effects, organ absorbed doses were calculated by Monte Carlo simulations using female and male anthropometric phantoms of the FASH and MASH series. MSDs between 180 and 5650 mGy were found based on the radiochromic film measurements. 40% of the patients monitored with radiochromic films received MSDs above the 2 Gy threshold for transient skin erythema. The findings of this study showed that the Ka,r can be used for risk estimates of tissue reactions in patients undergoing chemoembolization procedures. The Monte Carlo simulations showed that patients may receive organ doses between 500 mGy and 1 Gy. Occupational dosimetry was performed using thermoluminescent dosimeters and personal electronic devices distributed over various regions of the physician’s body. The results showed that the main operator could reach the annual limit of 20 mSv for the equivalent dose in the lens of the eyes with just one procedure per week if the radiation shields such as the ceiling suspended screen and goggles are not used. The highest values of personal dose equivalent Hp(d), measured in the body of the main operator was 5135.3 μSv in the left foot. Lack of table curtains explains the registered high values. Mean effective doses for the main operator, the auxiliary physician and the anesthesiologist in one of the institutions were 13 μSv, 6.1 μSv e 13.7 μSv, respectively. These results show that occupational doses received by the anesthesiologist in chemoembolization procedures may be higher than those received by the main operator. The results of the occupational dosimetry using electronic dosimeters showed that these devices can be used in a complementary way to estimate the occupational eye lens doses in hepatic chemoembolization procedures. High variability of radiation doses to patients and medical staff was observed among the six medical institutions, mainly because of the performance of X-ray equipments, complexity of the procedures, physical characteristics of the patients and the physician´s experience

Cette thèse a été réalisée dans le cadre de la dosimétrie des faisceaux de haute énergie délivrés au patient pendant un traitement de radiothérapie externe. L'objectif de ce travail est de vérifier que la distribution de dose 3D absorbée dans le patient est conforme au calcul réalisé sur le système de planification de traitement (TPS) à partir de l'imageur portal (en anglais : Electronic Portal Imaging Device, EPID). L'acquisition est réalisée en mode continu avec le détecteur aS-1200 au silicium amorphe embarqué sur la machine TrueBeam STx (VARIAN Medical system, Palo Alto, USA). Les faisceaux ont une énergie de 10 MeV et un débit de 600 UM.min-1. La distance source-détecteur (DSD) est de 150 cm. Après correction des pixels défectueux, une étape d'étalonnage permet de convertir leur signal en dose absorbée dans l'eau via une fonction de réponse. Des kernels de correction sont également utilisés pour prendre en compte la différence de matériaux entre l'EPID et l'eau et pour corriger la pénombre sur les profils de dose. Un premier modèle de calcul a permis ensuite de rétroprojeter la dose portale en milieu homogène en prenant en compte plusieurs phénomènes : les photons diffusés provenant du fantôme et rajoutant un excès de signal sur les images, l'atténuation des faisceaux, la diffusion dans le fantôme, l'effet de build-up et l'effet de durcissement du faisceau avec la profondeur. La dose reconstruite est comparée à celle calculée par le TPS avec une analyse gamma globale (3% du maximum de dose et 3 mm de DTA). L'algorithme a été testé sur un fantôme cylindrique homogène et sur un fantôme de pelvis à partir de champs modulés en intensité (RCMI) et à partir de champs d'arcthérapie volumique modulés, VMAT selon l'acronyme anglais Volumetric Modulated Arc Therapy. Le modèle a ensuite été affiné pour prendre en compte les hétérogénéités traversées dans le milieu au moyen des distances équivalentes eau dans une nouvelle approche de dosimétrie plus connue sous le terme de " in aqua vivo " (1). Il a été testé sur un fantôme thorax et, in vivo sur 10 patients traités pour une tumeur de la prostate à partir de champs VMAT. Pour finir, le modèle in aqua a été testé sur le fantôme thorax avant et après y avoir appliqué certaines modifications afin d'évaluer la possibilité de détection de sources d'erreurs pouvant influencer la bonne délivrance de la dose au patient.[...] / This thesis aims at the dosimetry of high energy photon beams delivered to the patient during an external radiation therapy treatment. The objective of this work is to use EPID the Electronic Portal Imaging Device (EPID) in order to verify that the 3D absorbed dose distribution in the patient is consistent with the calculation performed on the Treatment Planning System (TPS). The acquisition is carried out in continuous mode with the aS-1200 amorphous silicon detector embedded on the TrueBeam STx machine (VARIAN Medical system, Palo Alto, USA) for 10MV photons with a 600 UM.min-1 dose rate. The source-detector distance (SDD) is 150 cm. After correction of the defective pixels, a calibration step is performed to convert the signal into an absorbed dose in water via a response function. Correction kernels are also used to take into account the difference in materials between EPID and water and to correct penumbra. A first model of backprojection was performed to reconstruct the absorbed dose distribution in a homogeneous medium by taking into account several phenomena: the scattered photons coming from the phantom to the EPID, the attenuation of the beams, the diffusion into the phantom, the build-up, and the effect of beam hardening with depth. The reconstructed dose is compared to the one calculated by the TPS with global gamma analysis (3% as the maximum dose difference criteria and 3mm as the distance to agreement criteria). The algorithm was tested on a homogeneous cylindrical phantom and a pelvis phantom for Intensity-Modulated Radiation Therapy (IMRT) and (Volumetric Arc Therapy (VMAT) technics. The model was then refined to take into account the heterogeneities in the medium by using radiological distances in a new dosimetrical approach better known as "in aqua vivo" (1). It has been tested on a thorax phantom and, in vivo on 10 patients treated for a prostate tumor from VMAT fields. Finally, the in aqua model was tested on the thorax phantom before and after making some modifications to evaluate the possibility of detecting errors that could affect the correct delivery of the dose to the patient. [...]

IMRT uses non-uniform beam intensities within a radiation field to provide patient-specific dose shaping, resulting in a dose distribution that conforms tightly to the planning target volume (PTV). Unavoidable geometric uncertainty arising from patient repositioning and internal organ motion can lead to lower conformality index (CI), a decrease in tumor control probability (TCP) and an increase in normal tissue complication probability (NTCP). The CI of the IMRT plan depends heavily on steep dose gradients between the PTV and organ at risk (OAR). Geometric uncertainties reduce the planned dose gradients and result in a less steep or “blurred” dose gradient. The blurred dose gradients can be maximized by constraining the dose objective function in the static IMRT plan or by reducing geometric uncertainty during treatment with corrective verification imaging. Internal organ motion and setup error were evaluated simultaneously for 118 individual patients with implanted fiducials and MV electronic portal imaging (EPI). The Gaussian PDF is patient specific and group standard deviation (SD) should not be used for accurate treatment planning for individual patients. Frequent verification imaging should be employed in situations where geometric uncertainties are expected. The dose distribution including geometric uncertainties was determined from integration of the convolution of the static dose gradient with the PDF. Local maximum dose gradient (LMDG) was determined via optimization of dose objective function by manually adjusting DVH control points or selecting beam numbers and directions during IMRT treatment planning. EUDf is a useful QA parameter for interpreting the biological impact of geometric uncertainties on the static dose distribution. The EUDf has been used as the basis for the time-course NTCP evaluation in the thesis. Relative NTCP values are useful for comparative QA checking by normalizing known complications (e.g. reported in the RTOG studies) to specific DVH control points. For prostate cancer patients, rectal complications were evaluated from specific RTOG clinical trials and detailed evaluation of the treatment techniques. Treatment plans that did not meet DVH constraints represented additional complication risk. Geometric uncertainties improved or worsened rectal NTCP depending on individual internal organ motion within patient.

IMRT uses non-uniform beam intensities within a radiation field to provide patient-specific dose shaping, resulting in a dose distribution that conforms tightly to the planning target volume (PTV). Unavoidable geometric uncertainty arising from patient repositioning and internal organ motion can lead to lower conformality index (CI), a decrease in tumor control probability (TCP) and an increase in normal tissue complication probability (NTCP). The CI of the IMRT plan depends heavily on steep dose gradients between the PTV and organ at risk (OAR). Geometric uncertainties reduce the planned dose gradients and result in a less steep or “blurred” dose gradient. The blurred dose gradients can be maximized by constraining the dose objective function in the static IMRT plan or by reducing geometric uncertainty during treatment with corrective verification imaging. Internal organ motion and setup error were evaluated simultaneously for 118 individual patients with implanted fiducials and MV electronic portal imaging (EPI). The Gaussian PDF is patient specific and group standard deviation (SD) should not be used for accurate treatment planning for individual patients. Frequent verification imaging should be employed in situations where geometric uncertainties are expected. The dose distribution including geometric uncertainties was determined from integration of the convolution of the static dose gradient with the PDF. Local maximum dose gradient (LMDG) was determined via optimization of dose objective function by manually adjusting DVH control points or selecting beam numbers and directions during IMRT treatment planning. EUDf is a useful QA parameter for interpreting the biological impact of geometric uncertainties on the static dose distribution. The EUDf has been used as the basis for the time-course NTCP evaluation in the thesis. Relative NTCP values are useful for comparative QA checking by normalizing known complications (e.g. reported in the RTOG studies) to specific DVH control points. For prostate cancer patients, rectal complications were evaluated from specific RTOG clinical trials and detailed evaluation of the treatment techniques. Treatment plans that did not meet DVH constraints represented additional complication risk. Geometric uncertainties improved or worsened rectal NTCP depending on individual internal organ motion within patient.