Monte-Carlo calculation of output correction factors for ionization chambers, solid-state detectors, and EBT3 film in small fields of high-energy photons.

High-energy accelerators are often used in oncological practice, but the information on the small-field dosimetry for the photon beams with nominal energy above 10 MV is limited. The goal of the present work was to determine the values of the output correction factor ( k Q clin , Q ref f clin , f ref $k_{{Q}_{{\rm{clin}}},{Q}_{{\rm{ref}}}}^{{f}_{{\rm{clin}}},{f}_{{\rm{ref}}}}$ ) for solid-state detectors (Diode E, PTW 60017; microDiamond, PTW 60019), EBT3 film, and ionization chambers (Semiflex, PTW 31010; Semiflex 3D, PTW 31021; PinPoint, PTW 31015; PinPoint 3D, PTW 31016) in the small fields formed by 10, 15, 18, and 20 MV photon beams. The output correction factors were calculated by Monte-Carlo method using EGSnrc toolkit for six field sizes (from 0.5 × 0.5 cm 2 $0.5 \times 0.5\ {\rm{cm}}^2$ to 10 × 10 cm 2 $10 \times 10\ {\rm{cm}}^2$ ) for isocentric and constant source-to-surface distance (SSD) techniques. The decrease in the field size led to an increase in k Q clin , Q ref f clin , f ref $k_{{Q}_{{\rm{clin}}},{Q}_{{\rm{ref}}}}^{{f}_{{\rm{clin}}},{f}_{{\rm{ref}}}}$ for ionization chambers, while for solid-state detectors and radiochromic film, k Q clin , Q ref f clin , f ref $k_{{Q}_{{\rm{clin}}},{Q}_{{\rm{ref}}}}^{{f}_{{\rm{clin}}},{f}_{{\rm{ref}}}}$ were less than unity at the smallest field size. A larger sensitive volume of ionization chamber corresponded to a stronger deviation of output correction factor from unity: 1.847 (125 mm3 PTW 31010) versus up to 1.183 (16 mm3 PTW 31016) at the smallest field of 10 MV beam. The calculated output correction factors were used to correct the output factors for PTW 60017, PTW 60019, and EBT3. The deviation of the corrected output factor from the results of Monte-Carlo simulation did not exceed 3% in the fields from 1.0 × 1.0 cm 2 $1.0 \times 1.0\ {\rm{cm}}^2$ to 4.0 × 4.0 cm 2 $4.0 \times 4.0\ {\rm{cm}}^2$ for 10 and 18 MV beams. Thus, Diode E, microDiamond, and EBT3 film can be recommended for small-field dosimetry of high-energy photons.

CPHR: 35 años al Servicio de la Protección Radiológica, la Salud y el Medio Ambiente / CPHR: 35 years at the Service of Radiological Protection, Health and the Environment

Resumen El Centro de Protección e Higiene de las Radiaciones fue fundado en 1985 para sustentar la aplicación segura de las tecnologías nucleares en Cuba. En la actualidad la institución es considerada como una referencia nacional y regional en materia de seguridad radiológica, gracias a una sólida estrategia institucional que aporta de manera sostenida soluciones a problemas prioritarios del país. Este trabajo presenta una reseña de los principales resultados del centro hasta la fecha.

Abstract The Center for Radiation Protection and Hygiene was founded in 1985 to support the safe application of nuclear technologies in Cuba. Nowdays, the institution is considered as a national and regional reference for radiation protection , thanks to the comprehensive institutional strategy that support the solutions of the problems with priority in the country. The paper presents the overview about the main results of the center up today.

PROFICIENCY TEST OF THE SSDL-ININ-MEXICO FOR THE CALIBRATION OF WELL-TYPE CHAMBERS WITH HDR 192IR SOURCES USING TWO DIFFERENT DOSIMETRY CODES OF PRACTICE FOR THE DETERMINATION OF REFERENCE AIR KERMA RATE KR.

The results of the comparison between SSDL-ININ and SSDL-CPHR (pilot laboratory) demonstrates the competence of the SSDL-ININ for the performance of the KR in 192Ir. The RININ/CHPR ratio for the calibration coefficients is 0.989 ± 0.005. The comparison uses three SI-HDR 1000-Plus as transfer chambers, series: A02423, A941755 and A973052. CPHR used a secondary standard PTW 3304 chamber, s/n 154, calibrated at PTB and ININ employed a secondary standard SI-90008 s/n A963391, calibrated at NPL. To determine KR, the SSDL-CPHR used the IAEA TEC-DOC-1274 and the SSDL-ININ used the IPEM (UK) code of practice. The latter uses a correction factor by source's geometry, ksg. The results show that both codes are equivalent; however, for the use of well chambers in the highlands or in locations with reduced atmospheric pressure, it is needed to apply an additional factor k'P, or, to design a well chamber with air-equivalent walls for the application of the conventional kPT.

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.