Use of the FBX dosimeter for the quality assurance of⁶⁰Co and high energy teletherapy machines by mail

Abstract

The mncentrations of the solutes in the standard mx dosimeter were changed in order to reduce the rate of Ihermal oxidation of fermus ions in the solution. ?he modified solution contained lo-' mol dm-3 ferrous ions, lo-' mol dmw3 knzoic acid and 5 x mol d r c 3 xylenol orange in 0.04 mol dm-3 aqueous aerated sulphuric acid. The rates of thermal axidation of fermus ions do not differ significantly when the solution is stored either in glass or polypropylene mntainem. The error due U) the post-imdiation delay in dose estimation depends on the dose and a dose of about 5 Gy is most suitable. When Ihe solution is stored up to about one month More irradiation and about one month after irradiation, the error in dose estimation is less than f2%. The blank and the irradiated solutions should be stored in similar containem 0031-9155/92/112095+OBE07.50 @ 1992 IO€' Publishing U d

Characterisation of a Ferrous Agarose Xylenol ( FAX ) gel for radiotherapy dose measurement

“…The samples irradiated at higher doses oxidize at a slower rate compared to the samples given low doses Since more ferrous are converted to ferric at higher doses, the amount of ferrous ions that remain in the gel is less and this leads to a slower oxidation 24 . Our results show that the effect of auto-oxidation was much less than 2% per day; hence, this had no significant effect on the readout values as the time between irradiation and readout was within 3 hours.…”

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

“…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.…”

FBX aqueous chemical dosimeter for measurement of virtual wedge profiles

“…This change in color is measured spectrophotometrically at about 540 nm as an estimate of the ferric ion yield. This system has been studied for various applications in radiotherapy such as percentage depth dose measurements, machine output calibrations, (3)(4)(5) brachytherapy source calibration, and in vivo dosimetry. (6,7) One of the important properties of this dosimeter is its energy-independent response for X-rays and gamma rays from 33 keV to 1250 keV.…”