RESUMEN
PURPOSE: This study explores the possibility of using lead to cover part of the radiation therapy facility maze walls in order to absorb low energy photons and reduce the total dose at the maze entrance of radiation therapy rooms. METHODS: Experiments and Monte Carlo simulations were utilized to establish the possibility of using high-Z materials to cover the concrete walls of the maze in order to reduce the dose of the scatteredphotons at the maze entrance. The dose of the backscatteredphotons from a concrete wall was measured for various scattering angles. The dose was also calculated by the FLUKA and EGSnrc Monte Carlo codes. The FLUKA code was also used to simulate an existing radiotherapy room to study the effect of multiple scattering when adding lead to cover the concrete walls of the maze. Monoenergetic photons were used to represent the main components of the x ray spectrum up to 10 MV. RESULTS: It was observed that when the concrete wall was covered with just 2 mm of lead, the measured dose rate at all backscattering angles was reduced by 20% for photons of energy comparable to Co-60 emissions and 70% for Cs-137 emissions. The simulations with FLUKA and EGS showed that the reduction in the dose was potentially even higher when lead was added. One explanation for the reduction is the increased absorption of backscatteredphotons due to the photoelectric interaction in lead. The results also showed that adding 2 mm lead to the concrete walls and floor of the maze reduced the dose at the maze entrance by up to 90%. CONCLUSIONS: This novel proposal of covering part or the entire maze walls with a few millimeters of lead would have a direct implication for the design of radiation therapy facilities and would assist in upgrading the design of some mazes, especially those in facilities with limited space where the maze length cannot be extended to sufficiently reduce the dose.
Asunto(s)
Materiales de Construcción , Arquitectura y Construcción de Instituciones de Salud , Plomo , Fotones/uso terapéutico , Dosis de Radiación , Radioterapia de Alta Energía/instrumentación , Dispersión de Radiación , Método de Montecarlo , Protección RadiológicaRESUMEN
PURPOSE: This study explores the possibility of using lead to cover part of the radiation therapy facility maze walls in order to absorb low energy photons and reduce the total dose at the maze entrance of radiation therapy rooms. METHODS: Experiments and Monte Carlo simulations were utilized to establish the possibility of using high-Z materials to cover the concrete walls of the maze in order to reduce the dose of the scattered photons at the maze entrance. The dose of the backscattered photons from a concrete wall was measured for various scattering angles. The dose was also calculated by the FLUKA and EGSnrc Monte Carlo codes. The FLUKA code was also used to simulate an existing radiotherapy room to study the effect of multiple scattering when adding lead to cover the concrete walls of the maze. Monoenergetic photons were used to represent the main components of the x ray spectrum up to 10 MV. RESULTS: It was observed that when the concrete wall was covered with just 2 mm of lead, the measured dose rate at all backscattering angles was reduced by 20% for photons of energy comparable to Co-60 emissions and 70% for Cs-137 emissions. The simulations with FLUKA and EGS showed that the reduction in the dose was potentially even higher when lead was added. One explanation for the reduction is the increased absorption of backscattered photons due to the photoelectric interaction in lead. The results also showed that adding 2 mm lead to the concrete walls and floor of the maze reduced the dose at the maze entrance by up to 90%. CONCLUSIONS: This novel proposal of covering part or the entire maze walls with a few millimeters of lead would have a direct implication for the design of radiation therapy facilities and would assist in upgrading the design of some mazes, especially those in facilities with limited space where the maze length cannot be extended to sufficiently reduce the dose.
Asunto(s)
Plomo , Fotones , Protección Radiológica/instrumentación , Radioterapia de Alta Energía/instrumentación , Dispersión de Radiación , Simulación por Computador , Arquitectura y Construcción de Instituciones de Salud , Ambiente de Instituciones de Salud , Modelos Teóricos , Método de Montecarlo , Exposición Profesional/prevención & control , Dosis de Radiación , Exposición a la Radiación/prevención & control , Protección Radiológica/métodos , Radioterapia de Alta Energía/métodos , Programas InformáticosRESUMEN
At the end of the 1980's and at the beginning of the 1990's, free fat autografts were abandoned because of the poor long-term results. Two theories supported by hystological studies (the host replacement theory or the cell survival theory) have now been proposed to explain survival of fat tissue. They demonstrate that, when harvested by a correct technique, fat tissue presents the ideal characteristics to be grafted, providing a good soft-tissue substitute with a minimum follow-up of four years up to 6 years. The authors present a multiple stage lipofilling technique in 99 cases of facial rejuvenation by means of lipolayering. Injections are performed every 20 days and fat is stored fat at -30 degrees C with good aesthetic results and minimal morbidity with clinical follow-up at 4 and 6 years. Histological examination of fat stored for 20 days and for 8 months was also performed in 10 patients. Microscopic and ultrastructural examination demonstrated that stored adipocytes retain their anatomical features and, when injected in multiple stages, are adequate to obtain good clinical results. Our histological study combined with the clinical outcomes, suggests the advantage of several stage injection of stored fat (-30 degrees C).
Asunto(s)
Tejido Adiposo/trasplante , Criopreservación/métodos , Ritidoplastia/métodos , Envejecimiento de la Piel , Adipocitos/patología , Adipocitos/ultraestructura , Tejido Adiposo/patología , Tejido Adiposo/ultraestructura , Adulto , Biopsia , Femenino , Estudios de Seguimiento , Humanos , Inyecciones Subcutáneas , Masculino , Persona de Mediana Edad , Cuidados Posoperatorios/métodos , Envejecimiento de la Piel/patología , Cuidados de la Piel/métodos , Factores de Tiempo , Resultado del TratamientoRESUMEN
The study involved 18 children aged 7 to 13 years, who all benefited from early reimplantation and appropriate immobilisation. Radicular treatment appeared to have little influence and adverse results, especially early rhizalysis, were common (50% versus 30% of good results). In the event of failure, dento-facial orthopedic treatment, where indicated, may provide a cosmetically acceptable solution.