Ferrous Xylenol Gel measurements for 6 and 10 MV photons in small field sizes

Abstract

The Fricke dosimeter is a ferrous sulfate aqueous solution that, when irradiated, oxidizes the Fe 2+ ions to Fe 3+ . This new concentration, generally determined through spectrophotometry, is directly proportional to the ionizing radiation absorbed energy. The Fricke Xylenol Gel dosimeter (FXG) was developed through the incorporation of swine skin gelatin and xylenol orange. These modifications provided better signal stability and sensitivity for lower absorbed dose measurements, such as those used in radiotherapy. In this work FXG samples were irradiated with absorbed doses of 2 Gy, from 6 MV and 10 MV photons, using small field sizes geometry for dosimetric parameters determination. All the FXG dosimeter readings were accomplished with our specially developed spectrophotometer, using a narrow light beam at the wavelength of 585 nm, where the highest absorbance sensitivity occurs. From our results, we can confirm not only that the FXG dosimetric system (FXG plus a high lateral spatial resolution spectrophotometer) can be used for general dosimetry, but as well for small field size dosimetry of interest in radiosurgery.

Evaluation of MRI-based MAGIC polymer gel dosimeter in small photon fields

“…The difference between measurements and calculations is reduced by increasing ield sizes due to decreasing of lateral electronic disequilibrium. The same result has been reported by Oliveira and Calcina for The Fricke Xylenol Gel dosimeter (FXG) compared with other dosimeters in small photon ields (5,18) .…”

“…To improve accuracy of treatment planning systems (TPS), determining of exact dosimetry is essential (3) . The dosimetric parameters required for commissioning and quality assurance of treatment planning systems include output factor (OF), off-axis ratio (OAR), and percentage depth dose (PDD) (4,5) . According to existence of lateral electronic disequilibrium and the sharp dose gradients in small ield sizes, measurement of OFs, OARs and PDDs are dif icult (4) .…”

Fricke dosimeter gel measurements of the profiles of shielded fields

“…Therefore, an accurate and precise dosimetry is necessary so that the prescribed absorbed dose can be administrated to the patient. The Fricke Xylenol Gel (FXG) dosimetry has shown interesting results applied to radiotherapy through dosimetric parameters studies, as measures of small irradiation fields, and a good agreement for these fields in comparison to other dosimeters such as ionization chamber, film and TLD Oliveira et al, 2007).…”

Determination of diffusion coefficient in Fricke Xylenol gel dosimeter after electron beam bombardment

“…The FXG dosimeter was developed through the incorporation of swine skin gelatin and xylenol orange [1,2]. These modifications provided better signal stability and sensitivity for lower absorbed dose measurements, such as those used in radiotherapy.…”

“…These modifications provided better signal stability and sensitivity for lower absorbed dose measurements, such as those used in radiotherapy. This dosimeter presents suitable characteristics for radiotherapy measurements as: low cost of its components, broad linear dependence on the absorbed dose up to 30 Gy for photons [2] and electrons [3], effective atomic number of 7.75 and density of 1.05 g/cm 3 near to 7.64 and 1.04 g/cm 3 , for soft tissue. The absorbance measurements were accomplished with a UV-visible spectrophotometer at the wavelength of 585 nm, where the FXG spectrum has its highest absorbance peak.…”