Proceedings.

Cover title: Peaceful uses of atomic energy.

Some aspects of dose measurement for accurate ion implantation /

Includes bibliographical references (p. 36).

Shieldose : a computer code for space-shielding radiation dose calculations /

Includes bibliographical references (p. 29).

Nuclear health and safety : radiation exposures for some cloud-sampling personnel need to be reexamined : report to the Chairman, Committee on Veterans Affairs, U.S. Senate /

"B-222195"--P. [1]

AVALIAÇÃO DA COMPRESSÃO DA IMAGEM DIGITAL DA TELERRADIOGRAFIA LATERAL NA REPRODUTIBILIDADE DA MARCAÇÃO DE PONTOS CEFALOMÉTRICOS

A imagem digital adquirida pelo sistema da placa de fósforo foto ativada é visualizada no monitor do computador em um formato denominado DICOM. Este formato ocupa muito espaço para armazenamento, o que dificulta o arquivamento e transmissão da imagem pela Internet. O objetivo deste estudo foi avaliar a influência da compressão JPEG, nos Fatores de Qualidade 100, 80 e 60 na reprodutibilidade da marcação de pontos cefalométricos em imagens de telerradiografias em norma lateral comparadas com o formato DICOM. A amostra consistiu de 120 imagens de telerradiografias em norma lateral obtidas a partir de 30 indivíduos, dos quais se obteve uma radiografia digital no formato DICOM. Essas imagens foram convertidas para o formato JPEG. Após o cegamento e randomização da amostra, três Ortodontistas calibrados marcaram a localização de 12 pontos cefalométricos em cada imagem utilizando o sistema de coordenadas X e Y. Esse procedimento foi repetido após 1 mês. A reprodutibilidade intra e inter observador foi calculada usando o teste de correlação intraclasse. Para comparação entre os grupos de compressão e DICOM na reprodutibilidade de marcação dos pontos utilizou se a Análise de Variância (ANOVA) a um critério para medidas repetidas. Os resultados mostraram que as marcações dos pontos cefalométricos foram bastante reprodutíveis, exceto para o ponto Órbita na coordenada X. Os diferentes formatos de arquivo mostraram estatisticamente iguais para cada ponto e eixo aferido. As compressões JPEG estudadas das imagens de telerradiografias em norma lateral não tiveram efeito na reprodutibilidade da marcação dos pontos cefalométricos testados.

AVALIAÇÃO DA REPRODUTIBILIDADE DE PONTOS CEFALOMÉTRICOS NAS TELERRADIOGRAFIAS DIGITAIS EM NORMA LATERAL NOS FORMATOS DICOM, TIFF E JPEG

A imagem radiográfica digital adquirida pelo sistema de placa de fósforo foto ativada é normalmente visualizada no monitor do computador no formato DICOM, caracterizado pela alta resolução das imagens. Como este formato ocupa muito espaço para armazenamento, as imagens digitais são submetidas a uma compressão, que otimiza a capacidade de espaço dos computadores e reduz o tempo de transmissão pela Internet. O objetivo desse estudo foi avaliar a influência da compressão TIFF e JPEG na reprodutibilidade intra e interexaminador da marcação de pontos cefalométricos em imagens de telerradiografias em norma lateral comparadas com o formato DICOM. A amostra consistiu de 90 imagens de telerradiografias obtidas a partir de 30 indivíduos, dos quais se obteve uma radiografia digital exibida no formato DICOM. Estas imagens foram convertidas para os formatos JPEG, com Fator de Qualidade 80 e TIFF. Após o cegamento e randomização da amostra, três ortodontistas calibrados marcaram a localização de 15 pontos cefalométricos em cada imagem utilizando o sistema de coordenadas x e y. Os resultados mostraram que as marcações dos pontos cefalométricos apresentaram concordância de reprodutibilidade tanto intra como interexaminador, exceto para os pontos Go, Po, Or, B e Pog . Os diferentes formatos de arquivo mostraram resultados estatisticamente semelhantes para cada ponto e eixo aferido. As compressões JPEG e TIFF estudadas não tiveram efeito, em imagens de telerradiografias em norma lateral, na reprodutibilidade intra e interexaminadores da marcação dos pontos cefalométricos testados.(AU)

A UTILIZAÇÃO DO LASER DE BAIXA INTENSIDADE NA MOVIMENTAÇÃO DENTÁRIA E NA SENSIBILIDADE DOLOROSA APÓS APLICAÇÃO DE FORÇA ORTODÔNTICA

O presente estudo objetivou avaliar a eficácia do Laser de Baixa Intensidade (LBI) na aceleração da movimentação dentária e na diminuição da dor frente à aplicação de força ortodôntica. A amostra foi composta por 19 pacientes, sendo doze do sexo feminino e sete do sexo masculino, com idade inicial média de 14,69 anos, todos com indicação para extrações de primeiros pré-molares. Destes, 66 caninos foram submetidos à retração inicial, sendo que 33 receberam aplicação de laser e 33 foram considerados controle. Utilizou-se o Laser de Baixa Intensidade de arseneto de gálio e alumínio, com comprimento de onda de 780nm, na dosimetria de 40mW;10J/cm2;10s/ponto, aplicado apenas uma vez ao mês em dez pontos, sendo cinco por vestibular e cinco por lingual/palatino. Modelos de gesso foram confeccionados durante todos os meses de retração dos caninos, que teve duração de quatro meses, sendo, posteriormente, digitalizados para se mensurar a quantidade de movimentação de um lado em relação ao outro, utilizando-se como referência as papilas incisivas. Para a avaliação da dor experimentada pelos pacientes, os mesmos foram orientados a preencher uma escala analógica visual (VAS) que variava de 0 a 10 , em que zero significava nenhuma dor e dez significava dor insuportável, nos intervalos de 12, 24, 48 e 72 horas após a aplicação da força ortodôntica. Foi mensurado o apinhamento de todas as hemiarcadas dos pacientes na fase inicial, medindo-se a distância entre os pontos de contato de cada dente. Para a verificação do padrão de normalidade, empregou-se o teste de Kolmogorov-Smirnov, sendo que para comparar o lado irradiado com o lado não irradiado foi utilizado o teste t pareado, exceto para a variável razão caninos/molares , analisada pelo teste não paramétrico de Wilcoxon (p<0,05). Os resultados mostraram que em relação ao apinhamento dentário, os lados irradiado e não irradiado apresentaram-se compatíveis. Além disso, não houve diferença estatisticamente significante entre a quantidade de retração dos caninos irradiados comparados aos não irradiados, o mesmo acontecendo com a sensibilidade dolorosa experimentada pelos pacientes. Concluiu-se assim que o LBI na dosimetria e forma como foi utilizado não foi eficiente na aceleração da movimentação dentária nem na redução da dor experimentada pelos pacientes frente às forças ortodônticas.

Antioxidants and protein oxidation

Proteins are susceptible to oxidation by reactive oxygen species, where the type of damage induced is characteristic of the denaturing species. The induction of protein carbonyls is a widely applied biomarker, arising from primary oxidative insult. However, when applied to complex biological and pathological conditions it can be subject to interference from lipid, carbohydrate and DNA oxidation products. More recently, interest has focused on the analysis of specific protein bound oxidised amino acids. Of the 22 amino acids, aromatic and sulphydryl containing residues have been regarded as being particularly susceptible to oxidative modification, with L-DOPA from tyrosine, ortho-tyrosine from phenylalanine; sulphoxides and disulphides from methionine and cysteine respectively; and kynurenines from tryptophan. Latterly, the identification of valine and leucine hydroxides, reduced from hydroperoxide intermediates, has been described and applied. In order to examine the nature of oxidative damage and protective efficacy of antioxidants the markers must be thoroughly evaluated for dosimetry in vitro following damage by specific radical species. Antioxidant protection against formation of the biomarker should be demonstrated in vitro. Quantification of biomarkers in proteins from normal subjects should be within the limits of detection of any analytical procedure. Further to this, the techniques for isolation and hydrolysis of specific proteins should demonstrate that in vitro oxidation is minimised. There is a need for the development of standards for quality assurance material to standardise procedures between laboratories. At present, antioxidant effects on protein oxidation in vivo are limited to animal studies, where dietary antioxidants have been reported to reduce dityrosine formation during rat exercise training. Two studies on humans have been reported last year. The further application of these methods to human studies is indicated, where the quality of the determinations will be enhanced through inter-laboratory validation.

Ultraviolet damage to the eye revisited:eye-sun protection factor (E-SPF®), a new ultraviolet protection label for eyewear

Ultraviolet (UV) radiation potentially damages the skin, the immune system, and structures of the eye. A useful UV sun protection for the skin has been established. Since a remarkable body of evidence shows an association between UV radiation and damage to structures of the eye, eye protection is important, but a reliable and practical tool to assess and compare the UV-protective properties of lenses has been lacking. Among the general lay public, misconceptions on eye-sun protection have been identified. For example, sun protection is mainly ascribed to sunglasses, but less so to clear lenses. Skin malignancies in the periorbital region are frequent, but usual topical skin protection does not include the lids. Recent research utilized exact dosimetry and demonstrated relevant differences in UV burden to the eye and skin at a given ambient irradiation. Chronic UV effects on the cornea and lens are cumulative, so effective UV protection of the eyes is important for all age groups and should be used systematically. Protection of children's eyes is especially important, because UV transmittance is higher at a very young age, allowing higher levels of UV radiation to reach the crystalline lens and even the retina. Sunglasses as well as clear lenses (plano and prescription) effectively reduce transmittance of UV radiation. However, an important share of the UV burden to the eye is explained by back reflection of radiation from lenses to the eye. UV radiation incident from an angle of 135°-150° behind a lens wearer is reflected from the back side of lenses. The usual antireflective coatings considerably increase reflection of UV radiation. To provide reliable labeling of the protective potential of lenses, an eye-sun protection factor (E-SPF®) has been developed. It integrates UV transmission as well as UV reflectance of lenses. The E-SPF® compares well with established skin-sun protection factors and provides clear messages to eye health care providers and to lay consumers. © 2014 Behar-Cohen et al, This work is published by Dove Medical Press Ltd.

Highly sensitive type IA fiber Bragg gratings as sensors in radiation environments

Type IA fiber gratings have unusual physical properties compared with other grating types. We compare with performance characteristics of Type IA and Type I Bragg gratings exposed to the effects of Co60 gamma-irradiation. A Bragg peak shift of 190 pm was observed for Type IA gratings written in Fibercore PS-1250/1500 photosensitive fiber at a radiation dose of 116 kGy. This is the largest wavelength shift recorded to date under radiation exposure. The Type IA and Type I gratings show different kinetics under radiation and during post-radiation annealing; this can be exploited for the design of a grating based dosimetry system. © 2012 SPIE.

Preparação e caracterização de biomateriais poliméricos para avaliação da viabilidade de uso como phantom biológico

The theoretical and experimental developments in the biomaterials area have been directly applied to different fields of Medicine (odontology, regenerative medicine and radiotherapy). These advances have focused both for diagnosing diseases such as for quantifying degrees of progression. From the perspective of these studies, biomaterials are being designed and manufactured for application in various areas of science, provided advances in diagnostic radiology, radiotherapy dosimetry and calibration of radiotherapy equipment. Develop a phantom from a biomaterial has become a great ally of medicine in the treat patients with oncological diseases, allowing better performance of the equipment in order to reduce damage to healthy tissue due to excessive exposure to radiation. This work used polymers: chitosan and gelatin, for making the polymeric structures and controlled for different types of production and processing, characterizing and evaluating the biopolymer by physical techniques (STL, SEM and DEI) and therefore analyze applicability as phantom mouse lung. It was possible to evaluate the morphology of biomaterials quantitatively by scanning electron microscopy associated with imaging technique. The relevance of this work focuses on developing a phantom from polymeric biomaterials that can act as phantom providing high image contrast when subjected to analysis. Thus, the choice of DEI technique is satisfactory since it is an imaging technique of X-ray high resolution. The images obtained by DEI have shown the details of the internal microstructure of the biomaterial produced which have ≈ 10 μm dimension. The phantoms had made density ranging from 0.08 a 0.13 g/cm3.

Radiation Dose to the Lens of the Eye from Computed Tomography Scans of the Head

While it is well known that exposure to radiation can result in cataract formation, questions still remain about the presence of a dose threshold in radiation cataractogenesis. Since the exposure history from diagnostic CT exams is well documented in a patient’s medical record, the population of patients chronically exposed to radiation from head CT exams may be an interesting area to explore for further research in this area. However, there are some challenges in estimating lens dose from head CT exams. An accurate lens dosimetry model would have to account for differences in imaging protocols, differences in head size, and the use of any dose reduction methods.

The overall objective of this dissertation was to develop a comprehensive method to estimate radiation dose to the lens of the eye for patients receiving CT scans of the head. This research is comprised of a physics component, in which a lens dosimetry model was derived for head CT, and a clinical component, which involved the application of that dosimetry model to patient data.

The physics component includes experiments related to the physical measurement of the radiation dose to the lens by various types of dosimeters placed within anthropomorphic phantoms. These dosimeters include high-sensitivity MOSFETs, TLDs, and radiochromic film. The six anthropomorphic phantoms used in these experiments range in age from newborn to adult.

First, the lens dose from five clinically relevant head CT protocols was measured in the anthropomorphic phantoms with MOSFET dosimeters on two state-of-the-art CT scanners. The volume CT dose index (CTDIvol), which is a standard CT output index, was compared to the measured lens doses. Phantom age-specific CTDIvol-to-lens dose conversion factors were derived using linear regression analysis. Since head size can vary among individuals of the same age, a method was derived to estimate the CTDIvol-to-lens dose conversion factor using the effective head diameter. These conversion factors were derived for each scanner individually, but also were derived with the combined data from the two scanners as a means to investigate the feasibility of a scanner-independent method. Using the scanner-independent method to derive the CTDIvol-to-lens dose conversion factor from the effective head diameter, most of the fitted lens dose values fell within 10-15% of the measured values from the phantom study, suggesting that this is a fairly accurate method of estimating lens dose from the CTDIvol with knowledge of the patient’s head size.

Second, the dose reduction potential of organ-based tube current modulation (OB-TCM) and its effect on the CTDIvol-to-lens dose estimation method was investigated. The lens dose was measured with MOSFET dosimeters placed within the same six anthropomorphic phantoms. The phantoms were scanned with the five clinical head CT protocols with OB-TCM enabled on the one scanner model at our institution equipped with this software. The average decrease in lens dose with OB-TCM ranged from 13.5 to 26.0%. Using the size-specific method to derive the CTDIvol-to-lens dose conversion factor from the effective head diameter for protocols with OB-TCM, the majority of the fitted lens dose values fell within 15-18% of the measured values from the phantom study.

Third, the effect of gantry angulation on lens dose was investigated by measuring the lens dose with TLDs placed within the six anthropomorphic phantoms. The 2-dimensional spatial distribution of dose within the areas of the phantoms containing the orbit was measured with radiochromic film. A method was derived to determine the CTDIvol-to-lens dose conversion factor based upon distance from the primary beam scan range to the lens. The average dose to the lens region decreased substantially for almost all the phantoms (ranging from 67 to 92%) when the orbit was exposed to scattered radiation compared to the primary beam. The effectiveness of this method to reduce lens dose is highly dependent upon the shape and size of the head, which influences whether or not the angled scan range coverage can include the entire brain volume and still avoid the orbit.

The clinical component of this dissertation involved performing retrospective patient studies in the pediatric and adult populations, and reconstructing the lens doses from head CT examinations with the methods derived in the physics component. The cumulative lens doses in the patients selected for the retrospective study ranged from 40 to 1020 mGy in the pediatric group, and 53 to 2900 mGy in the adult group.

This dissertation represents a comprehensive approach to lens of the eye dosimetry in CT imaging of the head. The collected data and derived formulas can be used in future studies on radiation-induced cataracts from repeated CT imaging of the head. Additionally, it can be used in the areas of personalized patient dose management, and protocol optimization and clinician training.

MRI-Guided Radiation Therapy: Investigating the Accuracy of Treatment Delivery

Purpose: To develop, evaluate and apply a novel high-resolution 3D remote dosimetry protocol for validation of MRI guided radiation therapy treatments (MRIdian® by ViewRay®). We demonstrate the first application of the protocol (including two small but required new correction terms) utilizing radiochromic 3D plastic PRESAGE® with optical-CT readout.

Methods: A detailed study of PRESAGE® dosimeters (2kg) was conducted to investigate the temporal and spatial stability of radiation induced optical density change (ΔOD) over 8 days. Temporal stability was investigated on 3 dosimeters irradiated with four equally-spaced square 6MV fields delivering doses between 10cGy and 300cGy. Doses were imaged (read-out) by optical-CT at multiple intervals. Spatial stability of ΔOD response was investigated on 3 other dosimeters irradiated uniformly with 15MV extended-SSD fields with doses of 15cGy, 30cGy and 60cGy. Temporal and spatial (radial) changes were investigated using CERR and MATLAB’s Curve Fitting Tool-box. A protocol was developed to extrapolate measured ΔOD readings at t=48hr (the typical shipment time in remote dosimetry) to time t=1hr.

Results: All dosimeters were observed to gradually darken with time (<5% per day). Consistent intra-batch sensitivity (0.0930±0.002 ΔOD/cm/Gy) and linearity (R2=0.9996) was observed at t=1hr. A small radial effect (<3%) was observed, attributed to curing thermodynamics during manufacture. The refined remote dosimetry protocol (including polynomial correction terms for temporal and spatial effects, CT and CR) was then applied to independent dosimeters irradiated with MR-IGRT treatments. Excellent line profile agreement and 3D-gamma results for 3%/3mm, 10% threshold were observed, with an average passing rate 96.5%± 3.43%.

Conclusion: A novel 3D remote dosimetry protocol is presented capable of validation of advanced radiation treatments (including MR-IGRT). The protocol uses 2kg radiochromic plastic dosimeters read-out by optical-CT within a week of treatment. The protocol requires small corrections for temporal and spatially-dependent behaviors observed between irradiation and readout.

Palaeoenvironment records of six sediment cores collected in the Gulf of Carpentaria

The Gulf of Carpentaria is an epicontinental sea (maximum depth 70 m) between Australia and New Guinea, bordered to the east by Torres Strait (currently 12 m deep) and to the west by the Arafura Sill (53 m below present sea level). Throughout the Quaternary, during times of low sea-level, the Gulf was separated from the open waters of the Indian and Pacific Oceans, forming Lake Carpentaria, an isolation basin, perched above contemporaneous sea-level with outlet channels to the Arafura Sea. A preliminary interpretation is presented of the palaeoenvironments recorded in six sediment cores collected by the IMAGES program in the Gulf of Carpentaria. The longest core (approx. 15 m) spans the past 130 ka and includes a record of sea-level/lake-level changes, with particular complexity between 80 and 40 ka when sea-level repeatedly breached and withdrew from Gulf/Lake Carpentaria. Evidence from biotic remains (foraminifers, ostracods, pollen), sedimentology and geochemistry clearly identifies a final marine transgression at about 9.7 ka (radiocarbon years). Before this transgression, Lake Carpentaria was surrounded by grassland, was near full, and may have had a surface area approaching 600 km-300 km and a depth of about 15 m. The earlier rise in sea-level which accompanied the Marine Isotopic Stage 6/5 transgression at about 130 ka is constrained by sedimentological and biotic evidence and dated by optical- and thermoluminescence and amino acid racemisation methods.

Synthese, Charakterisierung und koordinationschemische Untersuchung neuer Ferrocen-basierter Mono- und Diphosphidoliganden

Die vorliegende Dissertation beschäftigt sich mit der Synthese der außerordentlich unterentwickelten Substanzklasse der sekundären Disphosphinoferrocene sowie der Auslotung ihrer koordinationschemischen Eigenschaften, speziell gegenüber den Übergangsmetallen Zirkonium und Nickel und dem Alkalimetall Lithium.