We investigate the use of novel Ge-doped amorphous silica flat fibers as thermoluminescence dosimeters. The investigative irradiations were made using a Toshiba X-ray machine. Ge-doped fibers represent a viable system for use in diagnostic dosimetry. a b s t r a c tWe investigate the use of novel Ge-doped amorphous silica flat fibers as thermoluminescence dosimeters (TLDs) in verifying patient entrance surface-dose (ESD) in diagnostic examinations. Selected fibers with established dosimetric characteristics (including energy dependence, linearity, reproducibility, and fading) were loaded into plastic capsules in groups of six. The fibers have been calibrated against a parallel plate ionization chamber, use being made of x-rays generated at 70 kVp, accessing a Secondary Standards Dosimetry Laboratory (SSDL) facility. The fiber characterization measurements were made using a Toshiba X-ray machine operating within the nominal energies range 40 kVp to 150 kVp, for doses in the range 0.02 mGy up to 3 mGy. For doses from 2 mGy up to 150 mGy, the flat fibers exhibit linearity between TL yield and dose, reproducible to better than 3% standard deviation following repeat measurements (n ¼3). A marked energy-dependent response is observed for photons generated at potentials from 40 kVp to 150 kVp. From present results, it is concluded that Ge-doped fibers represent a viable system for use in diagnostic dosimetry, corrections being made for the various factors influencing TL yield.

The study focused on the measurement of percentage depth dose (PDD) in high energy photons and electrons by using the optically stimulated luminescent (OSL) dosimeters. The beam output calibration was performed on 6 MV photons and 6 MeV electrons and compared to that in the ionization chamber. The PDD was measured in 6 MV photons and 6 MeV electrons and the PDD curves were plotted by using the OSL dosimeters. The PDD curves were compared to that in other common dosimeters including ionization chamber, Gafchromic® EBT2 film dosimeter and the treatment planning software (TPS). The results showed that the beam output calibration measured by using the OSL dosimeters was in good agreement to the ionization chamber within 1.6 and 5.9% percentage of discrepancy for both 6 MV photons and 6 MeV electrons respectively. The measured PDD by using the OSL dosimeters were also in in good agreement to the ionization chamber, EBT2 film and TPS software within percentage 13.4 and 10.4% of discrepancies for 6 MV photons and 6 MeV electrons respectively. The overall results indicated the suitability of OSL dosimeters to be used for direct dosimetry measurements in high energy photons and electrons.

It is important to understand that the heel effect contributes higher dose to cathode bound. This study is to verify this effect and consequently utilized it to minimize the radiation dose to staff involved in fluoroscopy procedures especially those using mobile C-arm unit. Water phantom with size of 20 x 30 x 30 cm was used in this study. It was exposed to x-rays from a mobile C-arm unit with auto brightness control (ABC) function. An ion chamber and a solid state detector were used to measure the scattered radiation and primary beam profile. Based on the result it was clear that scattered radiation measured was highest on the cathode bound side. Hence personnel involves in fluoroscopy procedure should avoid or spend the least possible time within this cathode bound area in order to lessen the radiation risk.

The measurements of mass attenuation coefficients by using Compton scattering technique was carried out by using the Ludlum configuration. A 137Cs sealed sourced was used and attenuated at angles between 30 and 75° to provide scattered gamma energies between 337.72 and 564.09 keV. The mass attenuation coefficients of solid water and perspex were measured and compared to the calculated value of water by using XCOM. The results showed that the measured mass attenuation coefficients of solid water and Perspex® phantoms were in agreement to the values of water within 6.84 and 7.20% average percentage of discrepancies. The results indicated the suitability of the Ludlum configuration for the measurement of mass attenuation coefficients by using the Compton scattering method.

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