Use of the FBX dosemeter for the calibration of cobalt-60 and high-energy teletherapy machines

Abstract

The doses from the cobalt-60 teletherapy machines were measured using the FBX and secondary-standard dosemeters of Farmer-Baldwin type. The FBX dosemeter contained 0.20 mM ferrous ammonium sulphate, 5.0 mM benzoic acid and 0.20 mM xylenol orange in 0.05 N sulphuric acid. The values were compared with the values from a Fricke dosemeter and a graphite chamber used as primary standards. The values of the FBX, Fricke and graphite chambers agreed. There were, however wide differences among the different secondary-standard dosemeters themselves and with the FBX dosemeter. The FBX dosemeter was used for the measurement of central axis depth dose distributions for 5, 8, 10, 20 and 30 MeV electron and 42 MV x-ray beams.

Dosimetric proprieties of FBX dosimeter for high energy photon and electron beams

“…The correlation coefficient R 2 was 0.9996 which showed an excellent linear fit for the dose range of interest. The linear interval tested is consistent with the results cited in the literature [4,11] and is adequate for radiotherapy purposes. The radiation chemical yield G(Fe +3 ) value, which is a product of this slope and the molar extinction coefficient, ε, was evaluated and found to be 55.96 (± 0.40) × 10 −7 mol J −1 .…”

“…The FBX aqueous chemical dosimetry system that was developed for low level dose measurements by Gupta and co-workers [1][2][3] has found many applications in radiotherapy owing to its improved sensitivity at low doses as compared to Fricke system. It has been found useful for depth dose measurements, output calibration [4] quality assurance in external beam therapy [5], brachytherapy source calibration [6], in vivo dose measurements [7], and for measurement of virtual wedge profiles [8]. In this system absorbed doses are measured in terms of the oxidation yield of ferric ions produced by irradiation.…”

Fricke gel dosimeter with improved sensitivity for low‐dose‐level measurements

“…The study about dose response of benzoic Fricke gel was initiated using the composition reported originally by Gupta et al: 9 , 15 0.2 mM ferrous ammonium sulfate, 0.05 mM sulfuric acid, 0.2 mM Xylenol orange, 5 mM benzoic acid. The chemical composition of sensitive material was modified in the first instance, using suggestions provided in literature, mainly by Gupta et al 15 , 30 , 34 , 35 Also, suggestions by other authors were taken into account regarding the preparation process, 3 , 6 as well as cooling and storage procedures. (3,6,13) The formulation of benzoic Fricke gel is going to be used in the present study as the base for characterization of dosimetry performance of the $\mu \text{CT}$ facility.…”

“…The aim of this work is to develop, characterize, and execute preliminary implementation of a dosimetric radiation detector with high enough sensitivity capable of performing reliable absorbed‐dose distribution measurements for low‐dose level, as required by radiological procedures 3 , 30 . The study begins with a pre‐established composition of FXG for the measurement of radiation dose levels typically used for therapeutic purposes (i.e., relative high doses) 3 , 11 , 18 , 19 .…”

FBX aqueous chemical dosimeter for measurement of virtual wedge profiles

“…The FBX dosimeter solution was prepared following the method described by Gupta et al (3) to achieve the following composition: $0.2\hspace{0.17em}\text{mol}{\mathrm{normalm}}^{-3}$ ferrous ammonium sulfate, $5.0\hspace{0.17em}\text{mol}{\mathrm{normalm}}^{-3}$ benzoic acid, and $0.20\hspace{0.17em}\text{mol}{\mathrm{normalm}}^{-3}$ xylenol orange in $40.0\hspace{0.17em}\text{mol}{\mathrm{normalm}}^{-3}$ sulfuric acid. All chemicals came from E. Merck (Darmstadt, Germany), except for the xylenol orange, which came from Loba Chemie (Vienna, Austria).…”