Análisis de las dosis relativa entregada por el scanner GE de 16 canales v/s la dosis absoluta medida en vivo con cámaras de ionización en fantomas de 16 y 32 cm de diámetro
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Fecha
2016
Profesor/a Guía
Facultad/escuela
Idioma
es
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Editor
Universidad Andrés Bello
Nombre de Curso
Licencia CC
Licencia CC
Resumen
La tomografía computada (TC) es un método imagenológico cuyo uso ha ido en aumento desde sus inicios hasta la actualidad. Con el desarrollo de nueva tecnología, la calidad de imagen en TC ha ido mejorando, sin embargo, la dosis de radiación ionizante que entrega ésta técnica también ha ido en aumento. En un comienzo, los únicos indicadores de la dosis de radiación que emitía la TC eran los parámetros de kV y mAs. A partir del año 1981 se introduce el concepto de CTDI (CT dose index), expresado en mGy. El CTDI se mide en dos fantomas especificados por la FDA (Food and Drug Administration), los que consisten en 2 cilindros de polimetilmetacrilato, de 16 y 32 cm de diámetro, éstos se sitúan en el centro del tomógrafo para realizar las mediciones. Para poder medir la dosis de radiación se utiliza una cámara de ionización tipo lápiz de 100 mm de largo. Otro parámetro que es utilizado para medir dosis en TC es el DLP, que corresponde al producto entre el CTDIvol y la longitud de exploración en cm. Sin embargo, en base a revisión bibliográfica, en esta investigación se piensa que existe un margen de error entre la dosis relativa entregada por el TC y la dosis absoluta medida en vivo con cámaras de ionización en fantomas. Como no se conoce la exactitud porcentual de éste margen de error, el objetivo de este trabajo es el poderlo determinar a través de mediciones en vivo. Las mediciones son realizadas en base a un protocolo de cerebro y pelvis para los fantomas de 16 cm y 32 cm, respectivamente; a su vez se varían los parámetros de kV, mA y tipo de adquisición, con el fin de poder calcular el valor CTDIVOL en cada una de ellas. Por último, se comparan los valores obtenidos en las mediciones en vivo, con los valores de dosis relativa que entrega el scanner a través del parámetro CTDI y DLP, para corroborar la veracidad del factor CTDI, a lo que se agrega la determinación de la dosis efectiva en los protocolos de cerebro y pelvis.
Computed tomography (CT) is an imaging method whose use has been increasing since its inception to the present, occupying a significant percentage within the medical examinations using ionizing radiation. With the development of new technology, the CT image quality has been improving, however, the dose of ionizing radiation delivered this technique has also been increasing. At first, the only indicators of radiation dose CT were emitting parameters kV and mAs. From 1981 the concept of CTDI (CT dose index) is introduced, expressed in mGy, this concept is beginning to be used as a measure of the benchmark dose is receiving the patient in a given CT study. The CTDI is measured at two phantoms specified by the FDA, the two cylinders consisting of polymethylmethacrylate, 16 and 32 cm in diameter and 14 cm high, are situated at the center of the scanner to perform the measurements. To measure the dose of radiation, a pencil type ionization chamber 100 mm long is used. Another parameter that is used to measure the dose in CT is DLP, corresponding to the product between CTDIVOL and the scanning length in cm. However, based on literature review, this research it is thought that there is a margin of error between the relative dose delivered by the TC and the absolute dose measurement in vivo ionization chambers in phantoms. As the percentage accuracy of this margin of error is not known, the aim of this work is to determine through measurements in vivo. Measurements are performed based on a protocol for brain and pelvis phantoms 16 cm and 32 cm, respectively; turn parameters kV, mA and acquisition rate, in order to calculate the value CTDIVOL each are varied. Finally, the values obtained in measurements Live values relative dose delivered by the scanner through CTDI and DLP parameter to corroborate the veracity of CTDI factor to determine what dose is added compared protocols effective in brain and pelvis.
Computed tomography (CT) is an imaging method whose use has been increasing since its inception to the present, occupying a significant percentage within the medical examinations using ionizing radiation. With the development of new technology, the CT image quality has been improving, however, the dose of ionizing radiation delivered this technique has also been increasing. At first, the only indicators of radiation dose CT were emitting parameters kV and mAs. From 1981 the concept of CTDI (CT dose index) is introduced, expressed in mGy, this concept is beginning to be used as a measure of the benchmark dose is receiving the patient in a given CT study. The CTDI is measured at two phantoms specified by the FDA, the two cylinders consisting of polymethylmethacrylate, 16 and 32 cm in diameter and 14 cm high, are situated at the center of the scanner to perform the measurements. To measure the dose of radiation, a pencil type ionization chamber 100 mm long is used. Another parameter that is used to measure the dose in CT is DLP, corresponding to the product between CTDIVOL and the scanning length in cm. However, based on literature review, this research it is thought that there is a margin of error between the relative dose delivered by the TC and the absolute dose measurement in vivo ionization chambers in phantoms. As the percentage accuracy of this margin of error is not known, the aim of this work is to determine through measurements in vivo. Measurements are performed based on a protocol for brain and pelvis phantoms 16 cm and 32 cm, respectively; turn parameters kV, mA and acquisition rate, in order to calculate the value CTDIVOL each are varied. Finally, the values obtained in measurements Live values relative dose delivered by the scanner through CTDI and DLP parameter to corroborate the veracity of CTDI factor to determine what dose is added compared protocols effective in brain and pelvis.
Notas
Tesis (Tecnólogo Médico, mención en imagenología y física médica)
Palabras clave
Tomografía Computarizada, Computed Tomography dose index (CTDI), Dose-Length Product (DLP)