Calibração das câmaras de ionização para feixes de tomografia computadorizada no Brasil: a realidade atual

Abstract

OBJECTIVE: The aim of this study was to establish a calibration methodology specific for pencil ionization chambers used in computed tomography dosimetric procedures, in compliance with the most recent recommendations. The study was developed at the Calibration Laboratory of the Instituto de Pesquisas Energéticas e Nucleares. MATERIALS E METHODS: An industrial X-ray equipment, several types of ionization chambers, a mobile collimator (diaphragm type), and several high purity aluminum filters were utilized in this study. RESULTS: Diagnostic radiology standard irradiation fields were established according to IEC 61267 standard, and an adequate calibration procedure for pencil ionization chambers was elaborated. CONCLUSION: The appropriate calibration of pencil ionization chambers is already a reality in Brazil. The calibration procedure was defined on the basis of international standards and on a comparative study using two different methodologies.

Estimativa dos valores de MSAD em procedimentos de tomografia computadorizada utilizando filmes radiocrômicos

“…For the calibration, radiochromic film strips were inserted into the chamber cap (16) and positioned inside the phantom bores, reproducing exactly the position of the 10X5-3CT 100 mm pencil-type ionization chamber (Radcal Corporation) calibrated according to the established procedures (21) . The obtained results were compared with the purpose of obtaining the respective calibration coefficients.…”

Câmara de ionização de placas paralelas para radiação-X de radiografia convencional e mamografia

“…Plane-parallel ionization chambers for low-energy X-radiation and beta-radiation (13) , high-energy electrons (14)(15)(16) , computed tomography (17,18) , radioprotection (19) , extrapolation chambers for X-radiation and beta-radiation of dermatologic and ophthalmologic applications utilized in brachytherapy (20,21) have been constructed by Instituto de Pesquisas Energéticas e Nucleares.…”

Estudo teórico experimental da resposta radiométrica de câmaras de ionização utilizadas em dosimetria em feixes de raios X para diagnóstico radiológico

“…para realizar calibração de instrumentos com radiação gama e X, e calibração de monitores de contaminação alfa e/ou beta [18] . O procedimento de calibração deve ser meticuloso e reprodutível, para tanto o LCI utiliza qualidades recomendadas pela norma 61267 da Comissão Eletrotécnica Internacional (IEC) seguindo a Qualidade de Radiação de Referência (RQR) [75,76,77] . As tabelas 5 e 6 apresentam as características dos RQRs utilizados no Laboratório.…”

“…intensidade da radiação X. [75,76] Figura 7: C.I. monitora posicionada na saida do feixe do equipamento emissor de raios X, no LCI.…”