No description available.

La radiochirurgie par Gamma Knife constitue une modalité thérapeutique reconnue de certaines affections cérébrales. Le traitement se base sur l’administration d’un rayonnement focalisé au niveau d’une cible intracrânienne. L’efficacité de ce traitement repose sur la délivrance d’une dose d’irradiation efficace au sein d’un volume-cible associé à la délivrance d’une dose d’irradiation négligeable à l’extérieur de ce même volume-cible. En pratique, la dose d’irradiation administrée à l’intérieur du volume-cible n’est pas distribuée de manière homogène, et la dose d’irradiation reçue par les tissus situés en-dehors du volume-cible n’est pas nécessairement faible. Notre travail est basé sur l’hypothèse que l’imperfection de la distribution de la dose d’irradiation au sein du volume-cible et en-dehors de celui-ci peut être responsable des échecs et des complications rencontrées en radiochirurgie. Dans deux modèles cliniques de traitement radiochirurgical, le schwannome vestibulaire et la névralgie du trijumeau, nous avons montré qu’il existait une relation entre les paramètres de distribution de dose d’irradiation et certains résultats du traitement radiochirurgical par Gamma Knife de ces pathologies. Nous avons développé deux modèles expérimentaux d’irradiation radiochirurgicale de rats, l’un ciblé sur le striatum et l’autre sur le nerf trijumeau, permettant d’analyser les conséquences histologiques des variations de la distribution de dose à l’intérieur du volume-cible ainsi qu’à distance de celui-ci. Nous avons démontré que la réponse radiobiologique des tissus irradiés était fortement dépendante de ce paramètre dosimétrique, et que ce dernier constituait une donnée de la planification chirurgicale aussi importante que la dose de prescription. Nous avons corrélé ces résultats avec certaines observations réalisées dans d’autres indications de traitement radiochirurgical ainsi que dans l’analyse histologique de tumeurs traitées par Gamma Knife. Ces études mettent en évidence le rôle important joué par l’optimalisation de la distribution de la dose d’irradiation dans l’amélioration des résultats cliniques du traitement radiochirurgical. Les valeurs optimales de la distribution de dose dans les différentes indications de traitement radiochirurgical doivent être recherchées, et les différentes méthodes mises à notre disposition lors de la planification dosimétrique pour améliorer la distribution de dose doivent être utilisées avec discernement pour obtenir la dosimétrie radiochirurgicale la plus parfaite possible.

During the nineteenth and the twentieth centuries, the world has moved from a manufacturing to service-based economy, where the twentieth first century, will be the” century of services”, and will transform into the century of “international services” (Clark and Rajaratnam, 1999).

No description available.

No description available.

A radiocirurgia estereotáxica é um procedimento que trata principalmente lesões intracranianas para destruir células tumorais inacessíveis cirurgicamente. O Gamma Knife® é uma unidade de radiocirurgia estereotáxica que trata lesões exclusivamente cerebrais com feixes de 60Co de forma não-invasiva. De forma a garantir a acurácia na entrega da dose, esse tipo de equipamento necessita de detectores adequados para determinar a dose a ser entregue com exatidão. O protocolo da IAEA, TRS 483, é um guia padronizado para procedimentos dosimétricos e indicação de detectores relativos à dosimetria de referência de campos pequenos usados em feixes de radioterapia. Este trabalho seguiu as recomendações do TRS 483 na dosimetria do Gamma Knife® e foram realizadas medições utilizando duas câmaras de ionização, Exradin A16 e PTW Pinpoint 3D 31016, a alanina como detector de referência e os objetos simuladores indicados pela Elekta, fabricante do Gamma Knife®, sendo um de ABS e outro de Solid Water®. Um objeto simulador de acrílico foi construído, com as mesmas dimensões dos indicados pela Elekta, e implementado na dosimetria de equipamentos Gamma Knife®. A calibração das câmaras de ionização utilizadas foi realizada em um laboratório padrão primário e o coeficiente de calibração obtido foi utilizado no cálculo da dose absorvida na água dessas câmaras. Os estudos e testes dosimétricos realizados com o objeto simulador construído demonstraram resultados próximos aos simuladores existentes. Todos os fatores de correção indicados pelo TRS 483 foram considerados para o cálculo da dose absorvida. Foi constatado que o novo objeto simulador pode ser utilizado na dosimetria de Gamma Knife® e também para calibração de câmaras de ionização de volume pequeno, garantindo uma configuração de dosimetria e calibração similares e proporcionando ao usuário uma calibração próxima à configuração da dosimetria clínica. O projeto e a execução do objeto simulador utilizado neste trabalho visa contribuir para o TRS 483, de forma que seja utilizado na aplicação da dosimetria de Gamma Knife® e na calibração de câmaras de ionização de volume pequeno. / Stereotactic radiosurgery is a procedure that primarily treats intracranial lesions to destroy tumor cells that are inaccessible surgically. Gamma Knife® is a stereotactic radiosurgery unit that treats exclusively cerebral lesions using 60Co beams non-invasively. In order to ensure accurate dose delivery, this type of equipment requires adequate detectors to determine the dose is delivered accurately. The IAEA TRS 483 protocol is a standardized guide for dosimetric procedures and indication of detectors for reference dosimetry of small fields used in radiotherapy beams. Following TRS 483 recommendations in Gamma Knife® dosimetry, the measurements performed in this work used two ionization chambers; Exradin A16 and PTW Pinpoint 3D 31016, alanine as reference detector and phantoms indicated by Elekta, Gamma Knife\'s® manufacturer, which are made of ABS and Solid Water®. An acrylic phantom was built with the same dimensions as those indicated by Elekta, and implemented for the Gamma Knife® dosimetry. The calibration of the ionization chambers used was performed in a primary standard laboratory and the calibration coefficient obtained was used to calculate the absorbed dose in the water for these chambers. The dosimetry and tests performed with the acrylic phantom showed results close to the existing phantoms. All the correction factors indicated by TRS 483 were considered for the absorbed dose to water calculation. The new phantom can be used in Gamma Knife® dosimetry and also for calibration of small volume ionization chambers, assuring a similar dosimetry and calibration configuration and providing a calibration close to the clinical dosimetry configuration for the user. The design and implementation of the simulator object used in this work aims to contribute to the TRS 483, for the use in Gamma Knife® dosimetry and in the calibration of small volume ionization chambers.

A radiocirurgia estereotáxica é um procedimento que trata principalmente lesões intracranianas para destruir células tumorais inacessíveis cirurgicamente. O Gamma Knife® é uma unidade de radiocirurgia estereotáxica que trata lesões exclusivamente cerebrais com feixes de 60Co de forma não-invasiva. De forma a garantir a acurácia na entrega da dose, esse tipo de equipamento necessita de detectores adequados para determinar a dose a ser entregue com exatidão. O protocolo da IAEA, TRS 483, é um guia padronizado para procedimentos dosimétricos e indicação de detectores relativos à dosimetria de referência de campos pequenos usados em feixes de radioterapia. Este trabalho seguiu as recomendações do TRS 483 na dosimetria do Gamma Knife® e foram realizadas medições utilizando duas câmaras de ionização, Exradin A16 e PTW Pinpoint 3D 31016, a alanina como detector de referência e os objetos simuladores indicados pela Elekta, fabricante do Gamma Knife®, sendo um de ABS e outro de Solid Water®. Um objeto simulador de acrílico foi construído, com as mesmas dimensões dos indicados pela Elekta, e implementado na dosimetria de equipamentos Gamma Knife®. A calibração das câmaras de ionização utilizadas foi realizada em um laboratório padrão primário e o coeficiente de calibração obtido foi utilizado no cálculo da dose absorvida na água dessas câmaras. Os estudos e testes dosimétricos realizados com o objeto simulador construído demonstraram resultados próximos aos simuladores existentes. Todos os fatores de correção indicados pelo TRS 483 foram considerados para o cálculo da dose absorvida. Foi constatado que o novo objeto simulador pode ser utilizado na dosimetria de Gamma Knife® e também para calibração de câmaras de ionização de volume pequeno, garantindo uma configuração de dosimetria e calibração similares e proporcionando ao usuário uma calibração próxima à configuração da dosimetria clínica. O projeto e a execução do objeto simulador utilizado neste trabalho visa contribuir para o TRS 483, de forma que seja utilizado na aplicação da dosimetria de Gamma Knife® e na calibração de câmaras de ionização de volume pequeno. / Stereotactic radiosurgery is a procedure that primarily treats intracranial lesions to destroy tumor cells that are inaccessible surgically. Gamma Knife® is a stereotactic radiosurgery unit that treats exclusively cerebral lesions using 60Co beams non-invasively. In order to ensure accurate dose delivery, this type of equipment requires adequate detectors to determine the dose is delivered accurately. The IAEA TRS 483 protocol is a standardized guide for dosimetric procedures and indication of detectors for reference dosimetry of small fields used in radiotherapy beams. Following TRS 483 recommendations in Gamma Knife® dosimetry, the measurements performed in this work used two ionization chambers; Exradin A16 and PTW Pinpoint 3D 31016, alanine as reference detector and phantoms indicated by Elekta, Gamma Knife\'s® manufacturer, which are made of ABS and Solid Water®. An acrylic phantom was built with the same dimensions as those indicated by Elekta, and implemented for the Gamma Knife® dosimetry. The calibration of the ionization chambers used was performed in a primary standard laboratory and the calibration coefficient obtained was used to calculate the absorbed dose in the water for these chambers. The dosimetry and tests performed with the acrylic phantom showed results close to the existing phantoms. All the correction factors indicated by TRS 483 were considered for the absorbed dose to water calculation. The new phantom can be used in Gamma Knife® dosimetry and also for calibration of small volume ionization chambers, assuring a similar dosimetry and calibration configuration and providing a calibration close to the clinical dosimetry configuration for the user. The design and implementation of the simulator object used in this work aims to contribute to the TRS 483, for the use in Gamma Knife® dosimetry and in the calibration of small volume ionization chambers.

The interest in environmental issues is increasing and for this reason, assessing the potential environmental impacts of a product or system is of interest. A methodology developed for this particular purpose is the life cycle assessment, also known as LCA. It is not purely of interest these aspects are investigated though, as increasing requirements on organizations also matter. The purpose of this thesis was to investigate the feasibility to implement the methodology of LCA in the aspect of complex medical devices. To do this, the framework for the methodology has been reviewed and a case study performed. The case study comprised of conducting an LCA study on the radiosurgery device Leksell Gamma Knife® IconTM.  The outcome of the investigation showed that conducting an LCA study means a wide range of aspects need to be considered and specified to a high degree. A particular issue was the data requirements, as obtaining data meeting several objectives was challenging. The modeling was also identified as a difficulty. Tools such as software and databases with predefined processes were used, though as complex medical devices can use materials not common in other fields, a lack of appropriate predefined processes hinders the feasibility. The conducted case study was able to attain valuable insights even though the study did not comply with the standards providing the framework, the ISO 14040 series. To conduct a compliant LCA study for complex medical devices, extensive resources would be required as well as the involvement of relevant parties along the supply chain. It is seen improbable to achieve a compliant study the first time a particular type of complex medical device is investigated. However, it is believed the feasibility would increase as studies are repeated, as the data quality is likely to increase. Advancements of the tools, as well as ongoing research on the environmental impacts of more materials, are other factors thought to increase the feasibility of conducting LCA studies on complex medical devices in the future. / Intresset för miljöfrågor ökar och därav finns det ett intresse att undersöka vad den potentiella miljöpåverkan är för en produkt eller ett system. En metodologi utvecklad för detta specifika syfte är livscykelanalys som även kallas LCA. Det är inte enbart utav intresse som aspekterna utreds, de ökande krav som ställs på olika aktörer spelar också roll. Syftet med detta examensarbete var att undersöka genomförbarheten av livscykelanalyser med avseende på komplexa medicintekniska produkter. Detta gjordes genom att granska regelverken för LCA samt genomförandet av en fallstudie, vilken utgjordes av en livscykelanalys på strålkniven Leksell Gamma Knife® IconTM. Resultaten av undersökningen visade att genomförandet av en livscykelanalys innebär att ett stort spann av aspekter måste beaktas och specificeras i hög grad. Ett särskilt problem var kraven på data då det var utmanande att samla in data som skulle möta flera behov. En annan identifierad svårighet var modelleringen. Verktyg användes i form av mjukvara och databaser med fördefinierade processer men då komplexa medicintekniska produkter kan bestå av material som inte är vanliga inom andra områden, var bristen på passande fördefinierade processer ett hinder för genomförbarheten. Den genomförda fallstudien gav värdefulla resultat trots att den inte var utförd helt enligt standarderna i ISO 14040 serien. För att en LCA studie för komplexa medicintekniska produkter skall möta dessa krav krävs omfattande resurser och att flera berörda parter längs försörjningskedjan involveras. Det ses därför som osannolikt att en studie som genomförs för första gången på en viss typ av komplex medicinteknisk produkt kan leva upp till regelverket. Dock så förmodas genomförbarheten öka i takt med att studier upprepas, då kvaliteten på data tros öka. Utveckling av verktygen samt pågående forskning om miljöpåverkan från olika material är andra faktorer som anses öka genomförbarheten av livscykelanalyser på komplexa medicintekniska produkter i framtiden.

<p>A method to establish the boundaries of the sensitive volume for a chosen detector to within 50µm (as specified by Elekta Instuments AB) was investigated and is presented in this project. The detector studied was fixed to a positioning system with possibility to move with sub micrometer increments, and scanned in a narrow photon field. The detectors used for the experiment were silicon diodes and a pair of diamond detectors. The silicon diodes showed great promise for future study; two radiotherapy silicon diodes and one electrical component silicon diode were used. The electrical component silicon diode produced a surprisingly sharp dose profile compared with the medical silicon diodes. The diamond detectors gave no stable results at all.</p><p>As a radiation source 60Co proved most feasible, but a diagnostic x-ray source was also tested as well as a 99mTc source. These radiation sources were also examined with a modified Penelope code, i.e. Monte Carlo simulations. What became very obvious with the Monte Carlo simulations was the importance of the line up, which was never satisfactory.</p><p>To limit the sensitive volume of these detectors to within the desired boundaries showed great difficulty and was not achieved in this project.</p>

A method to establish the boundaries of the sensitive volume for a chosen detector to within 50µm (as specified by Elekta Instuments AB) was investigated and is presented in this project. The detector studied was fixed to a positioning system with possibility to move with sub micrometer increments, and scanned in a narrow photon field. The detectors used for the experiment were silicon diodes and a pair of diamond detectors. The silicon diodes showed great promise for future study; two radiotherapy silicon diodes and one electrical component silicon diode were used. The electrical component silicon diode produced a surprisingly sharp dose profile compared with the medical silicon diodes. The diamond detectors gave no stable results at all. As a radiation source 60Co proved most feasible, but a diagnostic x-ray source was also tested as well as a 99mTc source. These radiation sources were also examined with a modified Penelope code, i.e. Monte Carlo simulations. What became very obvious with the Monte Carlo simulations was the importance of the line up, which was never satisfactory. To limit the sensitive volume of these detectors to within the desired boundaries showed great difficulty and was not achieved in this project.