Patient dose in diagnostic radiology is usually expressed in terms of organ dose and effective dose. The latter is used as a measure of the stochastic risk. Determinations of these doses are obtained by measurements (Thermoluminescent dosemeters) or by calculations (Monte Carlo simulation). Conversion factors for the calculation of effective dose from dose-area product (DAP) values are commonly used to determine radiation dose in conventional x-ray imaging to realize radiation risks for different investigations, and for different ages. The exposure can easily be estimated by converting the DAP into an effective dose. The aim of this study is to determine the conversion factor in procedures by computing the ratio between effective dose and DAP for fluoroscopic cardiac procedures in adults and for conventional lung and urography examinations in children. Thermoluminescent dosemeters (TLD) were placed in an anthropomorphic phantom (Alderson Rando phantom) and child phantom (one year old) in order to measure the organ dose and compute the effective dose. A DAP meter was used to measure dose-area product. MC calculations of radiation transport in mathematical anthropomorphic phantoms were used to obtain the effective dose for the same conditions with DAP as input data. The deviation between the measured and calculated data was less than 10 %. The conversion factor for cardiac procedures varies between 0.19 mSvGy-1 cm-2 and 0.18 mSvGy-1 cm-2, for TLD respective MC. For paediatric simulation of a one year old phantom the average conversion factor for urography was 1.34 mSvGy-1 cm-2 and 1,48 mSvGy-1cm-2 for TLD respective MC. This conversion factor will decrease to 1.07 mSvGy-1 cm-2 using the TLD method, if the new ICRP (ICRP Publication 103) weighting factors were used to calculate the effective dose. For lung investigations, the conversion factor for children was 1.75 mSvGy-1 cm-2 using TLD, while this value was 1.62 mSvGy-1 cm-2 using MC simulation. The conversion value increased to 2.02 mSvGy-1 cm-2 using ICRP’s new recommendation for tissue weighting factors and child phantom.

No description available.

No description available.

O objetivo principal deste estudo foi analisar, na Gerência de Aceleradores Cíclotron do IPEN, o controle das doses de radiação ionizante e sua distribuição, comparando seus valores com as exigências regulamentares. A análise do controle das taxas de dose por meio do monitoramento de área foi realizada a partir de dados obtidos durante as produções de Flúor-18 no período de janeiro de 2010 a dezembro de 2011, totalizando 1011 medidas em cada ponto monitorado. A análise das doses provenientes de exposições ocupacionais foi realizada por meio de consulta aos históricos de dose individual. Durante os anos de 2007 a 2011 foram analisados os registros individuais das doses efetivas, totalizando 91 registros e de 2009 a 2011 foram analisados os registros de dose equivalente (nas mãos), totalizando 49 registros. Os indivíduos ocupacionalmente expostos envolvidos no estudo foram classificados, de acordo com a tarefa, em três grupos: alvos, radioproteção e operação e manutenção. Os resultados obtidos dos níveis de exposição ocupacional da radiação foram analisados e comparados com os limites estabelecidos pela autoridade regulatória nacional e com as recomendações internacionais. Com base nos resultados registrados do monitoramento de área e das doses recebidas, os procedimentos de radioproteção aplicados na instalação durante o período estudado foram averiguados e sugestões de melhorias foram dadas sob o ponto de vista da proteção radiológica. / The main purpose of this study was to analyze, at the Gerência de Aceleradores Cíclotron (Management of Cyclotron Accelerators) at IPEN, the control of ionizing radiation doses and their distribution by comparing their values with regulatory requirements. The analysis of the dose rate for the area monitoring was carried out from the data obtained during the production of Fluorine-18 from January 2010 to December 2011, totalizing 1011 measurements at each monitored spot. The doses analysis was performed through consultation of the individual dose records. During the years 2007 to 2011 the records of individual effective doses were analyzed, adding up to 91 records; from 2009 to 2011 the records of equivalent dose (hands) were analyzed, totalizing 49 records. The occupationally exposed individuals involved in the study were classified in three groups according to their task: targets, radioprotection and operation and maintenance. The results of occupational exposure levels of radiation were analyzed and compared with values established in national standards and international recommendations. Based on the results of the area monitoring and the doses received and recorded, radiation protection procedures implemented at the facility during the study period were checked and suggestions for improvements were given from the point of view of radiological protection.

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.

No description available.

No description available.

Die Nephrotoxizität ist die wichtigste Nebenwirkung bei Applikation von Radioimmunkonjugaten zur Konditionierung des Knochenmarks bei der Leukämiebehandlung. Die Auswirkungen der Unsicherheiten bei der Dosisbestimmung der Niere, insbesondere durch individuelle Nierenmasse und regionale Aktivitätsunterschiede, wurden untersucht. Die biologische Strahlenwirkung wurde als Biologisch Effektive Dosis unter Berücksichtigung des Zeitverlaufs der Dosisapplikation quantifiziert. Berechnungen wurden neben 188Rhenium auch für andere therapierelevante Radionuklide durchgeführt.

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.

Die Nephrotoxizität ist die wichtigste Nebenwirkung bei Applikation von Radioimmunkonjugaten zur Konditionierung des Knochenmarks bei der Leukämiebehandlung. Die Auswirkungen der Unsicherheiten bei der Dosisbestimmung der Niere, insbesondere durch individuelle Nierenmasse und regionale Aktivitätsunterschiede, wurden untersucht. Die biologische Strahlenwirkung wurde als Biologisch Effektive Dosis unter Berücksichtigung des Zeitverlaufs der Dosisapplikation quantifiziert. Berechnungen wurden neben 188Rhenium auch für andere therapierelevante Radionuklide durchgeführt.