Exploring the possibility of radiography in emission mode at higher energies: Improving the visualization of the internal structure of paintings / Explorando las posibilidades de la radiografía en modo de emisión a altas energías: Cómo optimizar la visualización de la estructura interna en pinturas

Summary We demonstrated in previous investigations that the internal structure of paintings can be visualized with conventional radiography in transmission mode when paintings have the proper stratigraphy. Unfortunately, there are many paintings that do not result in useful images. This problem can be solved by using radiography in emission mode. With this technique, the painting is irradiated with high energetic X-rays originating from an X-ray tube operating at 100 keV - 320 keV while inside the painting low energetic signals such as photoelectrons or characteristic photons are being generated. These signals escape from the top 10 µm of the painting and are able to illuminate the imaging plate. However, this technique has also some disadvantages. One of them is that it is not able to visualize underlying paintings. In this study, we explored the possibility to enhance the information depth by increasing the energy of the photon source from 100 keV up to 1.3325 MeV (i.e., 60Co source). At the same time, we also studied how the contrast between pigments is generated in emission mode. For this, we used mathematical simulation of particle transport in matter to understand the relation between input particle (particle type such as photon, electron or positron and the energy of the particle), the material being irradiated (element from which it is composed, thickness and density) and the output signal (generated particle types and energy). Finally, we will show that it is possible to image paintings using a 192Ir and even a 60Co source.

Resumen En investigaciones previas se ha demostrado que la estructura interna de las pinturas se puede visualizar satisfactoriamente con la radiografía convencional en modo de transmisión, siempre y cuando dichas pinturas tengan la estratigrafía adecuada. Desafortunadamente, hay muchos casos en los que la aplicación de este método no resultan en imágenes útiles. Este problema puede ser resuelto usando la radiografía en modo de emisión. Con esta técnica, la pintura se irradia con rayos X de alta energía originados en un tubo de rayos X trabajando entre 100 keV y 320 keV. Esto genera señales de baja energía (fotoelectrones o fotones característicos) en el interior de la pintura que, al escapar de las 10 μm superiores, pueden iluminar una placa de imágenes. No obstante, su aplicación también implica ciertas desventajas. Una de ellas es la incapacidad de visualizar las pinturas subyacentes. En este estudio, exploramos la posibilidad de incrementar la información obtenida a mayores profundidades aumentando la energía de la fuente de fotones desde 100 keV hasta 1.3325 MeV (fuente de 60Co). También estudiamos el impacto de esta energía en el contraste obtenido entre los pigmentos. Para esto, utilizamos la simulación matemática del transporte de partículas en la materia para comprender la relación entre partículas de entrada (fotones, electrones o positrones y la energía de las partículas), el material que se irradia (elemento del que está compuesto, espesor) y la señal de salida (tipos de partículas generados y energía). Finalmente, mostraremos que es posible crear imágenes de pinturas usando una fuente 60Co.

Proficiency test for calibration of well-type chambers using two types of 192Ir sources / Ensayo de aptitud para la calibración de cámaras de pozo usando dos tipos de fuentes de 192Ir

The Secondary Standard Dosimetry Laboratory of Cuba has implemented the calibration methodology of well-type chambers using the high dose rate sources. The use of different source types, at the hospital site as a modification of the procedure using other source types in a permanent facility of the primary laboratory leads to the need to evaluate the performance of the secondary procedure for calibration. The present paper describes the proficiency test to Cuban laboratory by making a comparison of dosimetry standards used in Germany and Cuba.

El Laboratorio Secundario de Calibración Dosimétrica de Cuba ha implementado una metodología para calibrar cámaras de pozo utilizando fuentes de de altas tasas de dosis. El uso de diferentes tipos de fuentes, como parte de una modificación del procedimiento con otro tipo de fuente usada en una instalación permanente del laboratorio primario, provocó la necesidad de evaluar el desempeño del procedimiento secundario de calibración. El trabajo describe el ensayo de aptitud al laboratorio cubano mediante un ejercicio de comparación entre los patrones dosimétricos de Alemania y Cuba.

Braquiterapia endobrônquica com alta taxa de dose no tratamento paliativo do câncer do pulmão / High-dose-rate endobronchial brachytherapy for palliative treatment of lung cancer

Tumores localmente avançados como forma de apresentação inicial dos tumores localizados na árvore traqueobrônquica não são um fenômeno raro. Os sintomas resultantes dessas lesões são comuns de câncer do pulmão e têm um impacto negativo significativo na qualidade de vida dos pacientes portadores de neoplasias pulmonares. As opções terapêuticas são múltiplas, sendo no entanto dependentes de variáveis, como a terapêutica inicial utilizada, o local da recorrência, a sintomatologia e as condições clínicas dos pacientes. Os objetivos principais foram demonstrar as principais vantagens terapêuticas da braquiterapia endobrônquica com alta taxa de dose em tumores da árvore respiratória. No período de 1998 a 2009, 42 pacientes com neoplasia pulmonar foram tratados paliativamente com braquiterapia endobrónquica com alta taxa de dose, com um total de 110 inserções, no Instituto Nacional de Câncer, Rio de Janeiro. A regressão endoscópica completa do tumor foi observada em 75% dos pacientes. A regressão tumoral teve relação direta com a melhora dos sintomas, especialmente da dispnéia. A sobrevida global foi de 56%, em 15 meses de acompanhamento. Não houve nenhum caso de hemoptise volumosa ou fatal, fistulas ou abscessos. Desse modo, concluimos que a braquiterapia endobrônquica com alta taxa de dose, é um excelente método com tratamento paliativo para os pacientes portadores de neoplasias pulmonares obstrutivas.

Locally advanced tumors as the initial form of presentation of tumors in the tracheobronchial tree are not a rare event. Symptoms resulting from these tumors are common in lung cancer and have a significant negative impact on quality of life of patients with lung cancer. The therapeutic options are manifold, but being dependent on variables such as the initial therapy used, the site of recurrence, the symptoms and the clinical condition of patients. The main objectives were to demonstrate the main advantages of brachytherapy treatment with high dose rate in tumors of the respiratory tree. In the period 1998-2009, 42 patients with lung cancer were treated with brachytherapy palliatively with high dose rate, with a total of 110 insertions, at the National Cancer Institute, Rio de Janeiro. The endoscopic complete tumor regression was observed in 75% of patients. The tumor regression was directly related to improvement of symptoms, especially dyspnea. Overall survival was 56% in 15 months monitoring. There were no cases of massive or fatal hemoptysis, fistulae or abscess. Thus, we conclude thatbrachytherapy with high dose rate, is an excellent method to palliative treatment for patients with obstructive lung cancers.