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Evaluation of materials for ESR-dosimetry: Salts of formic and lactic acid as an example.Edén Strindberg, Jerker January 2008 (has links)
<p>The technique of ESR-dosimetry and strategies for investigation of new materials as in regard to their applicability as ESR-dosimeters for radiotherapy has been reviewed. As an example six salts of formic and lactic acid has been evaluated. The applicability of the dosimeter has been judged by evaluating the tissue equivalence, radical yield, radical stability, spectral suitability, optimal readout parameters, dose response and sensitivity of the dosimetric system. Dependence of material characteristics and influence parameters has been analysed.</p><p>The reviewed methods have been successfully used for evaluation of the new materials. Lithium formate has been shown to be a good candidate relative to the state of the art dosimeter of alanine. Using optimal readout parameters lithium formate has been shown to be nine times as sensitive but even at moderate settings lithium formate is more sensitive. The results for lithium formate are in accordance to those of previous studies. The signal intensity of sodium formate has also proved to be high but unfortunately the signal fades rapidly.</p><p>Two new methods have been proposed as synthesis of the reviewed methods. The first allows flexible, effective and objective baseline correction of the ESR-spectrum. The second deals with dose response measurement by linear regression of the entire spectrum and was found to be successful in separating the spectral peaks of the induced radicals from the background signal.</p>
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Evaluation of materials for ESR-dosimetry: Salts of formic and lactic acid as an example.Edén Strindberg, Jerker January 2008 (has links)
The technique of ESR-dosimetry and strategies for investigation of new materials as in regard to their applicability as ESR-dosimeters for radiotherapy has been reviewed. As an example six salts of formic and lactic acid has been evaluated. The applicability of the dosimeter has been judged by evaluating the tissue equivalence, radical yield, radical stability, spectral suitability, optimal readout parameters, dose response and sensitivity of the dosimetric system. Dependence of material characteristics and influence parameters has been analysed. The reviewed methods have been successfully used for evaluation of the new materials. Lithium formate has been shown to be a good candidate relative to the state of the art dosimeter of alanine. Using optimal readout parameters lithium formate has been shown to be nine times as sensitive but even at moderate settings lithium formate is more sensitive. The results for lithium formate are in accordance to those of previous studies. The signal intensity of sodium formate has also proved to be high but unfortunately the signal fades rapidly. Two new methods have been proposed as synthesis of the reviewed methods. The first allows flexible, effective and objective baseline correction of the ESR-spectrum. The second deals with dose response measurement by linear regression of the entire spectrum and was found to be successful in separating the spectral peaks of the induced radicals from the background signal.
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Dosimetria 3D de um tratamento simulado de próstata na presença de próteses femorais metálicas. / 3D dosimetry of a simulated prostate treatment in the presence femoral prostheses.Rojas, Diana Maritza Cuevas 24 January 2017 (has links)
Historicamente a radioterapia é divida em radioterapia externa, braquiterapia e radioisotopoterapia sistemática. As diferenças entre as três está no posicionamento da fonte de radiação com respeito ao corpo humano. Na radioterapia externa a fonte fica a uma certa distância do paciente, já no caso da braquiterapia as fontes podem ser inseridas dentro de cavidades do corpo ou implantadas diretamente nos tecidos. Na radioisotopoterapia sistemática isótopos radiativos são administrados por via oral ou venosa. Dessas três a radioterapia externa é a mais usada pois, ela permite realizar planejamentos de radioterapia em três dimensões (3D), partindo inicialmente de uma tomografia computadorizada da região do tumor. O planejamento baseado na tomografia computadorizada permite que a distribuição da radiação nos tecidos seja feito com mais precisão evitando assim, que os tecidos sadios sejam afetados. Nesse trabalho a radioterapia externa convencional, foi implementada e executada para um tratamento de próstata com implantes metálicos, usando 4 campos de irradiação (0, 90, 180, 270 graus) e uma dose total planejada de 70 Gy fracionada em 35 sessões, cada uma com 2 Gy. Em qualquer tipo de tratamento que envolva a radiação ionizante é exigido um controle de qualidade para assim, determinar se a dose inicialmente planejada será entregue ou não ao tumor. Idealmente deveria ser implementado um controle de qualidade em três dimensões mas, até o momento não há um dosímetro 3D consolidado na rotina clinica. No entanto, o uso de géis poliméricos associados à técnica de leitura de dose com imagem de ressonância magnética (IRM) possibilita a dosimetria tridimensional. Nesse contexto, é aplicada a dosimetria 3D usando para isso, o gel magic com formaldeído (magic-f). Além da dosimetria 3D, foram realizadas medidas de dose absorvida por meio de dosimetria pontual, para tal fim são utilizados dosímetros termoluminescentes e de alanina. Na avaliação da distribuição de dose feita pelo planejamento e a medida com o gel é usado a análise gama (3%/3mm), neste caso, a distribuição de dose medida concorda com a distribuição de dose planejada TPS. A análise gama apresenta um porcentagem de aprovação do 93%. Os valores de dose absorvida na interface osso-metal determinados pelos dosímetros TL apresentam um aumento de 1,73 Gy na região do osso sacro e outros aumentos entre o 0,16 e 0,33 Gy foram encontrados em regiões como a cabeça do fêmur e quadril. Esses aumentos na dose foram só para duas sessões com doses entregadas ao fantom de 2 Gy. De igual maneira para os dosímetros de alanina se encontro um aumento na dose de 1,22 e 2,42 Gy na região do osso sacro. O planejamento feito nesse caso foi de 6 Gy. Os resultados evidentemente mostram como as inomogeneidades de um material com número atómico alto, gera perturbações sobre as distribuições de dose inicialmente planejadas. / Historically, Radiotherapy is divided into external radiotherapy, brachytherapy and systemic radioisotopotherapy. The difference between the three lies in the position of the radiation source regarding the human body. In external radiotherapy the source is at a certain distances of patient, and in the case of brachytherapy, this source can be inserted into cavities of body or implanted directly in the tissues. In systemic radiotherapy radioisotopes are administered orally or intravenously. Of these three, external radiotherapy is the most used because it allows planning of radiotherapy in three dimensions (3D), starting from a CT scan of the tumor region. Computed tomography planning allows the distribution of radiation in the tissues to be more accurate thus avoiding, that healthy tissues are affected. In our case, conventional external radiotherapy was implemented and executed for a prostate treatment with metal implants, using 4 irradiation fields (0, 90, 180, 270 degrees) and a total planned dose of 70 Gy fractioned in 35 sessions each with 2 Gy. In any type of treatment involving ionizing radiation, quality control (QC) is required to determine if the dose initially planned is delivered or not to the tumor. Ideally, a quality control should be implemented in three dimensions but to date there is no consolidated 3D dosimeter system in the clinic routine. However, the used of polymeric gels associated with magnetic resonance image (IRM) allow three-tridimensional dosimetry. In this context, the 3D dosimetry is applied using the magic gel with formaldehyde (magic-f). In addition to 3D dosimetry, absorbed dose measurements were performed by means of a dose in a point, using thermoluminescent and alanine dosimeters. The comparison of dose distributions calculated by TPS and measured in the gel was made using by gamma analysis (3% / 3mm), in this case, the distribution of dose measurement agrees with the distributions expected by TPS. The analysis shows a percentage of approval of 93%. The absorbed dose values at the bone-metal interface determined by the TL dosimeters, presented a 1.73 Gy increase in the region of the sacral bone, and another increases between 0,16 and 0,33 Gy were found in the regions as the head of the femur and the hip. These dose increases were only for two sessions with doses delivered to the phanton of 2 Gy. Similarly for alanine dosimeters were found increases in the dose of 1.22 and 2.42 Gy in the region of sacral bone. The planning done in this case was 6 Gy. The results evidently show how the inomogeneities of a material with a high atomic number generate disturbances over the initially planned dose distributions.
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Dosimetria 3D de um tratamento simulado de próstata na presença de próteses femorais metálicas. / 3D dosimetry of a simulated prostate treatment in the presence femoral prostheses.Diana Maritza Cuevas Rojas 24 January 2017 (has links)
Historicamente a radioterapia é divida em radioterapia externa, braquiterapia e radioisotopoterapia sistemática. As diferenças entre as três está no posicionamento da fonte de radiação com respeito ao corpo humano. Na radioterapia externa a fonte fica a uma certa distância do paciente, já no caso da braquiterapia as fontes podem ser inseridas dentro de cavidades do corpo ou implantadas diretamente nos tecidos. Na radioisotopoterapia sistemática isótopos radiativos são administrados por via oral ou venosa. Dessas três a radioterapia externa é a mais usada pois, ela permite realizar planejamentos de radioterapia em três dimensões (3D), partindo inicialmente de uma tomografia computadorizada da região do tumor. O planejamento baseado na tomografia computadorizada permite que a distribuição da radiação nos tecidos seja feito com mais precisão evitando assim, que os tecidos sadios sejam afetados. Nesse trabalho a radioterapia externa convencional, foi implementada e executada para um tratamento de próstata com implantes metálicos, usando 4 campos de irradiação (0, 90, 180, 270 graus) e uma dose total planejada de 70 Gy fracionada em 35 sessões, cada uma com 2 Gy. Em qualquer tipo de tratamento que envolva a radiação ionizante é exigido um controle de qualidade para assim, determinar se a dose inicialmente planejada será entregue ou não ao tumor. Idealmente deveria ser implementado um controle de qualidade em três dimensões mas, até o momento não há um dosímetro 3D consolidado na rotina clinica. No entanto, o uso de géis poliméricos associados à técnica de leitura de dose com imagem de ressonância magnética (IRM) possibilita a dosimetria tridimensional. Nesse contexto, é aplicada a dosimetria 3D usando para isso, o gel magic com formaldeído (magic-f). Além da dosimetria 3D, foram realizadas medidas de dose absorvida por meio de dosimetria pontual, para tal fim são utilizados dosímetros termoluminescentes e de alanina. Na avaliação da distribuição de dose feita pelo planejamento e a medida com o gel é usado a análise gama (3%/3mm), neste caso, a distribuição de dose medida concorda com a distribuição de dose planejada TPS. A análise gama apresenta um porcentagem de aprovação do 93%. Os valores de dose absorvida na interface osso-metal determinados pelos dosímetros TL apresentam um aumento de 1,73 Gy na região do osso sacro e outros aumentos entre o 0,16 e 0,33 Gy foram encontrados em regiões como a cabeça do fêmur e quadril. Esses aumentos na dose foram só para duas sessões com doses entregadas ao fantom de 2 Gy. De igual maneira para os dosímetros de alanina se encontro um aumento na dose de 1,22 e 2,42 Gy na região do osso sacro. O planejamento feito nesse caso foi de 6 Gy. Os resultados evidentemente mostram como as inomogeneidades de um material com número atómico alto, gera perturbações sobre as distribuições de dose inicialmente planejadas. / Historically, Radiotherapy is divided into external radiotherapy, brachytherapy and systemic radioisotopotherapy. The difference between the three lies in the position of the radiation source regarding the human body. In external radiotherapy the source is at a certain distances of patient, and in the case of brachytherapy, this source can be inserted into cavities of body or implanted directly in the tissues. In systemic radiotherapy radioisotopes are administered orally or intravenously. Of these three, external radiotherapy is the most used because it allows planning of radiotherapy in three dimensions (3D), starting from a CT scan of the tumor region. Computed tomography planning allows the distribution of radiation in the tissues to be more accurate thus avoiding, that healthy tissues are affected. In our case, conventional external radiotherapy was implemented and executed for a prostate treatment with metal implants, using 4 irradiation fields (0, 90, 180, 270 degrees) and a total planned dose of 70 Gy fractioned in 35 sessions each with 2 Gy. In any type of treatment involving ionizing radiation, quality control (QC) is required to determine if the dose initially planned is delivered or not to the tumor. Ideally, a quality control should be implemented in three dimensions but to date there is no consolidated 3D dosimeter system in the clinic routine. However, the used of polymeric gels associated with magnetic resonance image (IRM) allow three-tridimensional dosimetry. In this context, the 3D dosimetry is applied using the magic gel with formaldehyde (magic-f). In addition to 3D dosimetry, absorbed dose measurements were performed by means of a dose in a point, using thermoluminescent and alanine dosimeters. The comparison of dose distributions calculated by TPS and measured in the gel was made using by gamma analysis (3% / 3mm), in this case, the distribution of dose measurement agrees with the distributions expected by TPS. The analysis shows a percentage of approval of 93%. The absorbed dose values at the bone-metal interface determined by the TL dosimeters, presented a 1.73 Gy increase in the region of the sacral bone, and another increases between 0,16 and 0,33 Gy were found in the regions as the head of the femur and the hip. These dose increases were only for two sessions with doses delivered to the phanton of 2 Gy. Similarly for alanine dosimeters were found increases in the dose of 1.22 and 2.42 Gy in the region of sacral bone. The planning done in this case was 6 Gy. The results evidently show how the inomogeneities of a material with a high atomic number generate disturbances over the initially planned dose distributions.
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