Modern radiotherapy methods require sophisticated treatment planning and radiation dose delivery ... more Modern radiotherapy methods require sophisticated treatment planning and radiation dose delivery routines, which in turn demand stringent quality assurance. This paper describes recent advances in three-dimensional optical computed tomography (OCT) readout for radiation dosimetry in which a tissue-equivalent radiochromic gels is used to achieve sub-millimetre spatial resolution for (512)3 voxel arrays in readout times of about half an hour.
Nuclear Instruments & Methods in Physics Research Section B-beam Interactions With Materials and Atoms, 2000
In almost every single application of ionising radiation, the accurate determination of absorbed ... more In almost every single application of ionising radiation, the accurate determination of absorbed radiation energy is of great importance. Radiation sensitive gels were ®rst proposed for non-destructive and non-invasive measurements of the spatial distribution of radiation absorbed dose in 1984 [1]. Two dierent systems were developed but neither of these systems is widely used in practice due to some technical drawbacks. To overcome the problems associated with previous systems a gelatin gel of dierent composition has been devised and characterised for radiation dosimetry. This system is based on the changes in the optical properties of a transparent gel medium when it is exposed to ionising radiation. The detection material was carefully investigated and the role of each constituent of this system has been studied in order to determine the optimum composition. Gel with this formula has a linear dose response in the range 0.1±30 Gy, this range can be altered to suit other applications by changing the concentration of the active chemicals. The gel sensitivity, de®ned as the change in optical density per unit radiation dose, was found to be 70 Â 10 À3 cm À1 Gy À1 and the system stability was studied for both pre-and post-irradiation eects. This new formulation allows a convenient, rapid and economic readout method using an optical tomography system operating at visible wavelengths. Ó
Nuclear Instruments & Methods in Physics Research Section B-beam Interactions With Materials and Atoms, 2000
In almost every single application of ionising radiation, the accurate determination of absorbed ... more In almost every single application of ionising radiation, the accurate determination of absorbed radiation energy is of great importance. Radiation sensitive gels were first proposed for non-destructive and non-invasive measurements of the spatial distribution of radiation absorbed dose in 1984 [1]. Two different systems were developed but neither of these systems is widely used in practice due to some technical drawbacks. To overcome the problems associated with previous systems a gelatin gel of different composition has been devised and characterised for radiation dosimetry. This system is based on the changes in the optical properties of a transparent gel medium when it is exposed to ionising radiation. The detection material was carefully investigated and the role of each constituent of this system has been studied in order to determine the optimum composition. Gel with this formula has a linear dose response in the range 0.1-30 Gy, this range can be altered to suit other applications by changing the concentration of the active chemicals. The gel sensitivity, defined as the change in optical density per unit radiation dose, was found to be 70×10 -3 cm -1 Gy -1 and the system stability was studied for both pre- and post-irradiation effects. This new formulation allows a convenient, rapid and economic readout method using an optical tomography system operating at visible wavelengths.
Accurate determination of the spatial distribution of the absorbed dose of ionising radiation pla... more Accurate determination of the spatial distribution of the absorbed dose of ionising radiation plays an important role in radiotherapy, industrial radiation processing and many other applications. Computer calculations have frequently been used to estimate three-dimensional (3D) dose distributions in complex geometries and it becomes important to validate these by accurate 3D measurements. For this purpose we have been investigating the use of gelatin gels loaded with a modified Fricke solution which are pale orange in appearance and which, upon irradiation, become increasingly purple when viewed in normal light. This ferrous sulphate xylenol orange in gelatin gel (FXG) system displays very good properties, such as sensitivity, linearity and dynamic range, that make it suitable for 3D dosimetry applications. A high-speed optical tomography readout technique has been developed enabling two-dimensional projections of optical absorption data to be recorded rapidly. From these data the 3D absorbed dose distribution can quickly be derived with minimal degradation due to ion diffusion.
Nuclear Instruments & Methods in Physics Research Section A-accelerators Spectrometers Detectors and Associated Equipment, 1999
... We are grateful for helpful discussions and advice on optical techniques from Dr. Dmitrii Sty... more ... We are grateful for helpful discussions and advice on optical techniques from Dr. Dmitrii Styrkas. References. 1 JC Gore, YS Kang and RJ Schulz. Phys. Med. ... Med. Biol., 35 (1990), p. 1623. 3 MJ Maryanski, RJ Schulz, GS Ibbott, JC Gatenby, J. Xie, D. Horton and JC Gore. Phys. ...
Nuclear Instruments & Methods in Physics Research Section A-accelerators Spectrometers Detectors and Associated Equipment, 2007
The gel dosimetry method was found to be capable of addressing complicated issues related to dose... more The gel dosimetry method was found to be capable of addressing complicated issues related to dose measurements particularly in modern sophisticated radiotherapy applications. The Ferrous-sulphate Xylenol-orange and Gelatin (FXG) radiochromic gel dosemeter is one of the systems used for such applications. Some chemical dosemeters show different responses for low-and medium-energy X-rays in comparison with high-energy g-photons. The energy and dose rate dependence of the FXG dose response was examined. In addition to the detector response, other important dosimetric properties of the system were investigated for different X-ray beam qualities with tube voltages in the range 100-300 kV. An orthovoltage X-ray therapy unit was used to irradiate standard sized samples of FXG from different batches for radiation doses in the range 0-20 Gy. r
Different gel dosimetry techniques have been proposed as methods for three dimensional dose distr... more Different gel dosimetry techniques have been proposed as methods for three dimensional dose distribution measurements. Gel dosimeters were proposed for radiotherapy dosimetry at which the calibration of any dose-measuring technique is the main requirement for its proper practical application. The standardisation of the technique requires the establishment of a method for the calibration of each type of these gel materials. The aim of this study is to determine the chemical yield for the radiochromic "Ferrous-sulphate and Xelenol-orange Gelatin" (FXG) gel. Using standard absorbed dose to water protocol, the radiation field is calibrated first; then a standard Fricke solution dosimeter is calibrated. The obtained chemical yield for Fricke is G(Fe3+) = 1.68×106 [mol. J-1]. Finally, FXG dosimeter was calibrated against the standard Fricke solution before calculating the system chemical yield and comparing its value with Fricke system. The results show that square.G (FXG) = 6093.1 [m2. J-1] = 19.5×square.G (Fricke). Compared with the Fricke system, the FXG dosimeter has much higher sensitivity. Additionally, the overall accuracy and reproducibility of the gel detector was also comparable to those reported for Fricke solution. However, the FXG dosimeter properties could be improved further through the establishment of a defined manufacturing procedures and calibration method; as well as precise selection of sensitive materials and radiation effects evaluation techniques.
Environmental effects on the optical properties of a sensitive radiochromic gel dosemeter; in par... more Environmental effects on the optical properties of a sensitive radiochromic gel dosemeter; in particular storage, irradiation and measurements temperature were studied. Knowledge of light temperature and other ambient effects help to optimise working conditions and minimize errors. A ferrous-sulphate dosemeter with xylenol orange ion indicator incorporated in a gelatin gel matrix (FXG) was prepared under normal working conditions, and the samples were then kept in closed storage area at different temperature ranging from 5 °C up to the gel melting temperature about 35 °C . The samples optical absorbance was then measured quantitatively using double beam spectrophotometry. There is a small and steady increase in the absorbance 0.3×10 -3 / °C with increasing temperature until about 30 °C when we observe a big jump in the gel absorbance. Finally, additional important behaviour of FXG material was noticed, that is the changes occurred under the influence of rising temperature are reversible which is different from the permanent radiation caused changes.
Modern radiotherapy methods require sophisticated treatment planning and radiation dose delivery ... more Modern radiotherapy methods require sophisticated treatment planning and radiation dose delivery routines, which in turn demand stringent quality assurance. This paper describes recent advances in three-dimensional optical computed tomography (OCT) readout for radiation dosimetry in which a tissue-equivalent radiochromic gels is used to achieve sub-millimetre spatial resolution for (512)3 voxel arrays in readout times of about half an hour.
Nuclear Instruments & Methods in Physics Research Section B-beam Interactions With Materials and Atoms, 2000
In almost every single application of ionising radiation, the accurate determination of absorbed ... more In almost every single application of ionising radiation, the accurate determination of absorbed radiation energy is of great importance. Radiation sensitive gels were ®rst proposed for non-destructive and non-invasive measurements of the spatial distribution of radiation absorbed dose in 1984 [1]. Two dierent systems were developed but neither of these systems is widely used in practice due to some technical drawbacks. To overcome the problems associated with previous systems a gelatin gel of dierent composition has been devised and characterised for radiation dosimetry. This system is based on the changes in the optical properties of a transparent gel medium when it is exposed to ionising radiation. The detection material was carefully investigated and the role of each constituent of this system has been studied in order to determine the optimum composition. Gel with this formula has a linear dose response in the range 0.1±30 Gy, this range can be altered to suit other applications by changing the concentration of the active chemicals. The gel sensitivity, de®ned as the change in optical density per unit radiation dose, was found to be 70 Â 10 À3 cm À1 Gy À1 and the system stability was studied for both pre-and post-irradiation eects. This new formulation allows a convenient, rapid and economic readout method using an optical tomography system operating at visible wavelengths. Ó
Nuclear Instruments & Methods in Physics Research Section B-beam Interactions With Materials and Atoms, 2000
In almost every single application of ionising radiation, the accurate determination of absorbed ... more In almost every single application of ionising radiation, the accurate determination of absorbed radiation energy is of great importance. Radiation sensitive gels were first proposed for non-destructive and non-invasive measurements of the spatial distribution of radiation absorbed dose in 1984 [1]. Two different systems were developed but neither of these systems is widely used in practice due to some technical drawbacks. To overcome the problems associated with previous systems a gelatin gel of different composition has been devised and characterised for radiation dosimetry. This system is based on the changes in the optical properties of a transparent gel medium when it is exposed to ionising radiation. The detection material was carefully investigated and the role of each constituent of this system has been studied in order to determine the optimum composition. Gel with this formula has a linear dose response in the range 0.1-30 Gy, this range can be altered to suit other applications by changing the concentration of the active chemicals. The gel sensitivity, defined as the change in optical density per unit radiation dose, was found to be 70×10 -3 cm -1 Gy -1 and the system stability was studied for both pre- and post-irradiation effects. This new formulation allows a convenient, rapid and economic readout method using an optical tomography system operating at visible wavelengths.
Accurate determination of the spatial distribution of the absorbed dose of ionising radiation pla... more Accurate determination of the spatial distribution of the absorbed dose of ionising radiation plays an important role in radiotherapy, industrial radiation processing and many other applications. Computer calculations have frequently been used to estimate three-dimensional (3D) dose distributions in complex geometries and it becomes important to validate these by accurate 3D measurements. For this purpose we have been investigating the use of gelatin gels loaded with a modified Fricke solution which are pale orange in appearance and which, upon irradiation, become increasingly purple when viewed in normal light. This ferrous sulphate xylenol orange in gelatin gel (FXG) system displays very good properties, such as sensitivity, linearity and dynamic range, that make it suitable for 3D dosimetry applications. A high-speed optical tomography readout technique has been developed enabling two-dimensional projections of optical absorption data to be recorded rapidly. From these data the 3D absorbed dose distribution can quickly be derived with minimal degradation due to ion diffusion.
Nuclear Instruments & Methods in Physics Research Section A-accelerators Spectrometers Detectors and Associated Equipment, 1999
... We are grateful for helpful discussions and advice on optical techniques from Dr. Dmitrii Sty... more ... We are grateful for helpful discussions and advice on optical techniques from Dr. Dmitrii Styrkas. References. 1 JC Gore, YS Kang and RJ Schulz. Phys. Med. ... Med. Biol., 35 (1990), p. 1623. 3 MJ Maryanski, RJ Schulz, GS Ibbott, JC Gatenby, J. Xie, D. Horton and JC Gore. Phys. ...
Nuclear Instruments & Methods in Physics Research Section A-accelerators Spectrometers Detectors and Associated Equipment, 2007
The gel dosimetry method was found to be capable of addressing complicated issues related to dose... more The gel dosimetry method was found to be capable of addressing complicated issues related to dose measurements particularly in modern sophisticated radiotherapy applications. The Ferrous-sulphate Xylenol-orange and Gelatin (FXG) radiochromic gel dosemeter is one of the systems used for such applications. Some chemical dosemeters show different responses for low-and medium-energy X-rays in comparison with high-energy g-photons. The energy and dose rate dependence of the FXG dose response was examined. In addition to the detector response, other important dosimetric properties of the system were investigated for different X-ray beam qualities with tube voltages in the range 100-300 kV. An orthovoltage X-ray therapy unit was used to irradiate standard sized samples of FXG from different batches for radiation doses in the range 0-20 Gy. r
Different gel dosimetry techniques have been proposed as methods for three dimensional dose distr... more Different gel dosimetry techniques have been proposed as methods for three dimensional dose distribution measurements. Gel dosimeters were proposed for radiotherapy dosimetry at which the calibration of any dose-measuring technique is the main requirement for its proper practical application. The standardisation of the technique requires the establishment of a method for the calibration of each type of these gel materials. The aim of this study is to determine the chemical yield for the radiochromic "Ferrous-sulphate and Xelenol-orange Gelatin" (FXG) gel. Using standard absorbed dose to water protocol, the radiation field is calibrated first; then a standard Fricke solution dosimeter is calibrated. The obtained chemical yield for Fricke is G(Fe3+) = 1.68×106 [mol. J-1]. Finally, FXG dosimeter was calibrated against the standard Fricke solution before calculating the system chemical yield and comparing its value with Fricke system. The results show that square.G (FXG) = 6093.1 [m2. J-1] = 19.5×square.G (Fricke). Compared with the Fricke system, the FXG dosimeter has much higher sensitivity. Additionally, the overall accuracy and reproducibility of the gel detector was also comparable to those reported for Fricke solution. However, the FXG dosimeter properties could be improved further through the establishment of a defined manufacturing procedures and calibration method; as well as precise selection of sensitive materials and radiation effects evaluation techniques.
Environmental effects on the optical properties of a sensitive radiochromic gel dosemeter; in par... more Environmental effects on the optical properties of a sensitive radiochromic gel dosemeter; in particular storage, irradiation and measurements temperature were studied. Knowledge of light temperature and other ambient effects help to optimise working conditions and minimize errors. A ferrous-sulphate dosemeter with xylenol orange ion indicator incorporated in a gelatin gel matrix (FXG) was prepared under normal working conditions, and the samples were then kept in closed storage area at different temperature ranging from 5 °C up to the gel melting temperature about 35 °C . The samples optical absorbance was then measured quantitatively using double beam spectrophotometry. There is a small and steady increase in the absorbance 0.3×10 -3 / °C with increasing temperature until about 30 °C when we observe a big jump in the gel absorbance. Finally, additional important behaviour of FXG material was noticed, that is the changes occurred under the influence of rising temperature are reversible which is different from the permanent radiation caused changes.
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