Browsing by Author "Bosi, SG"

Now showing 1 - 3 of 3
  • No Thumbnail Available
    Item
    Dosimetry aspects of a non-diffusing genipin-gelatin gel
    (Pergamon-Elsevier Science Ltd, 2013-02-01) Davies, JB; Bosi, SG; Baldock, C
    Genipin-gelatin gel shows promise as a stable, three-dimensional dosimeter for use in quality assurance for radiotherapy treatments. Genipin creates cross-links in gelatin, forming a blue colour that bleaches quantitatively upon irradiation. A formulation suitable for dosimetry was investigated by varying the concentrations of genipin, gelatin and sulphuric acid and determining the dose sensitivity. An important parameter of the gel preparation that affects dose sensitivity is the temperature at which the cross-linking reaction takes place. The most suitable formulation for dose measurements in 1 cm pathlength cuvettes was found to be made from 50 mu M genipin, 4% w/w gelatin and 100 mM sulphuric acid in the final gel. An evaluation of the diffusion coefficient of chromophores in this gel dosimeter demonstrated that this genipin-gelatin gel is a non-diffusing dosimeter. This dosimeter was also evaluated for stability, dose sensitivity, irradiation and measurement temperature dependence and dose rate dependence. No appreciable dependence on dose rate in the range 0.4-40 Gy min(-1) was found. No appreciable dependence on measurement temperature between 15 and 23 degrees C was found. A slight dependence on irradiation temperature was found and this was used to determine the product of the molar linear absorption coefficient and the radiation chemical yield. Finally, the dosimeter measurement uncertainty was evaluated and this was used to determine the dose resolution. Although the focus of this work is on a genipin-gelatin gel dosimeter, the measurement and calibration techniques presented may be applied to any gel dosimetry system measured spectrophotometrically. © 2013, Elsevier Ltd.
  • No Thumbnail Available
    Item
    A genipin-gelatin gel dosimeter for radiation processing
    (Pergamon Elsevier Science Ltd, 2012-08-01) Davies, JB; Bosi, SG; Baldock, C
    Genipin, a fruit extract from Gardenia jasminoides Ellis, forms cross-links in solutions of gelatin, to form a blue hydrogel that bleaches quantitatively upon irradiation and the colour change can be measured with a spectrophotometer. With the addition of sulphuric acid this dosimeter is sufficiently sensitive for quality assurance of radiotherapy level dosimetry. Without sulphuric acid the gel has a reduced sensitivity and responds linearly with dose between 100 and 1000 Gy, making it potentially useful as a dosimeter for radiation processing applications such as the phytosanitary irradiation treatment of food. We investigated the dose response characteristics of this new formulation and found that the darker gels are more sensitive to dose and have a reduced uncertainty. © 2012, Elsevier Ltd.
  • No Thumbnail Available
    Item
    Radiological characterization and water equivalency of genipin gel for x-ray and electron beam dosimetry
    (IOP Publishing, 2011-08-07) Gorjiara, T; Hill, R; Kuncic, Z; Bosi, SG; Davies, JB; Baldock, C
    The genipin radiochromic gel offers enormous potential as a three-dimensional dosimeter in advanced radiotherapy techniques. We have used several methods (including Monte Carlo simulation), to investigate the water equivalency of genipin gel by characterizing its radiological properties, including mass and electron densities, photon interaction cross sections, mass energy absorption coefficient, effective atomic number, collisional, radiative and total mass stopping powers and electron mass scattering power. Depth doses were also calculated for clinical kilovoltage and megavoltage x-ray beams as well as megavoltage electron beams. The mass density, electron density and effective atomic number of genipin were found to differ from water by less than 2%. For energies below 150 keV, photoelectric absorption cross sections are more than 3% higher than water due to the strong dependence on atomic number. Compton scattering and pair production interaction cross sections for genipin gel differ fromwater by less than 1%. The mass energy absorption coefficient is approximately 3%higher thanwater for energies<60 keVdue to the dominance of photoelectric absorption in this energy range. The electron mass stopping power and mass scattering power differ from water by approximately 0.3%. X-ray depth dose curves for genipin gel agree to within 1% with those for water. Our results demonstrate that genipin gel can be considered water equivalent for kilovoltage and megavoltage x-ray beam dosimetry. For megavoltage electron beam dosimetry, however, our results suggest that a correction factor may be needed to convert measured dose in genipin gel to that ofwater, since differences in some radiological properties of up to 3% compared to water are observed. Our results indicate that genipin gel exhibits greater water equivalency than polymer gels and PRESAGE formulations. © 2011 IOP Publishing LTD.