OSL and TL response characterization of LiF:MG,Ti microdosimeters to be applied to VMAT quality assurance.

This paper aims to evaluate the feasibility of applying LiF:Mg,Ti microdosimeters as a new method of dosimetry to volumetric-modulated arc therapy (VMAT) RapidArc. The response of microdosimeters presented a maximum variation of ±3.18% and ±0.510% using optically stimulated luminescence (OSL) and thermoluminescence (TL) techniques, respectively. Although studies were conducted on LiF:Mg,Ti microdosimeters previously, the microdosimeters in this study showed precision and high potential of application in VMAT dosimetry and in the verification of treatment planning using the VMAT technique.

Dose-response and intrinsic efficiency of thermoluminescent dosimeters in a 15 MV clinical photon beam in a liquid water phantom.

This paper compares the performance of CaSO4:Dy and LiF dosimeters irradiated with a 15 MV photon beam of a clinical linear accelerator to 0.1-10 Gy in a liquid water. The dose-response curves are linear up to 5 Gy. The average TL sensitivity of CaSO4:Dy is 26 and 287 times higher than the sensitivities of LiF:Mg,Ti and microLiF:Mg,Ti, respectively. CaSO4:Dy has an intrinsic efficiency 71% and 94% higher than the intrinsic efficiencies of LiF:Mg,Ti and microLiF:Mg,Ti, respectively.

Brazilian gamma-neutron dosemeter: response to 241AmBe and 252Cf neutron sources.

With the aim of improving the monitoring of workers potentially exposed to neutron radiation in Brazil, the IPEN/CNEN-SP in association with PRO-RAD designed and developed a passive individual gamma-neutron mixed-field dosemeter calibrated to be used to (241)AmBe sources. To verify the dosimetry system response to different neutron spectra, prototypes were irradiated with a (252)Cf source and evaluated using the dose-calculation algorithm developed for (241)AmBe sources.

Gamma/neutron dose evaluation using Fricke gel and alanine gel dosimeters to be applied in boron neutron capture therapy.

Gel dosimetry has been studied mainly for medical applications. The radiation induced ferric ions concentration can be measured by different techniques to be related with the absorbed dose. Aiming to assess gamma/thermal neutrons dose from research reactors, Fricke gel and alanine gel solutions produced at IPEN using 300 bloom gelatin were mixed with Na(2)B(4)O(7) salt, and the mixtures were irradiated at the beam hole #3 of the IEA-R1 research reactor, (BH#3) adapted to BNCT studies, and the dose-response was evaluated using spectrophotometry technique.

Electron dose radiation response of dyed PMMA detectors developed at IPEN.

Dyed polymethylmethacrylate (PMMA) detectors using yellow, red, blue and green colouring compounds, commercially available in Brazil, were originally developed and characterised using the optical absorption (OA) technique for gamma radiation, with the aim of obtaining a sensitive, useful, practical and cheap dosemeter for use in the quality control of industrial gamma radiation processing. In this work these detectors were evaluated for electron OA response, for use in the quality control of electron accelerator radiation processing. The studied parameters were the absorption spectra, dose-rate dependence between 2.66 and 45.22 kGy s(-1); dose response between 1.2 and 110 kGy; and energy dependence of response between 0.8 and 1.5 MeV electron energy.

PTTL method applied to UV radiation detection during refractive surgery using excimer laser.

The method of phototransferred thermoluminescence (PTTL), using CaSO(4):Dy pellets produced at IPEN as sensitive material, was used to detect the spread laser radiation inside the surgery room during refractive surgical procedures using ArF excimer lasers. The purpose of this work was to study the viability of performing the ultraviolet radiation (UVR) exposure detection of patients and the hospital's surgical staff during a refractive surgery. The CaSO(4):Dy pellets were positioned at different distances from the laser source inside the surgery room: patient's ( congruent with 0.15 m), surgeon's ( congruent with 0.5 m) and nurse's ( congruent with 1.0 m) foreheads, lateral ( congruent with 1.5 m) and back ( congruent with 4.0 m) walls. The measurements of PTTL were carried out at two different conditions: five surgeries, each one taking approximately 10 min, and during a period of 4 h (cumulative), when several operations were performed. The detectors positioned as far as 4.0 m from the UV laser source were sensitised, making the UVR detection feasible at large source-detector distances. The absorbed energy was detected in the range from 40 microJ to 30 mJ during a surgery. This result indicates that the method studied can be used to detect the spread UVR.

A comparative study based on dosimetric properties of different sugars.

Measurements of free radical densities in sugar by electron spin resonance (ESR) constitute a useful method for determining the dose received in the case of accidental irradiation because this material retains its radiation history. The aim of this work is to establish methods for practical dose assessment of people involved in ionising irradiation accidents, using two types of sugar: sucrose and dextrose. In this regard, practical considerations of sample preparation, grain size, ESR spectrum and spurious mechanical-induced ESR signal are discussed. Also presented are results for signal reproducibility, radiation response, signal stability and low-dose values. Studies on irradiated samples were carried out to explain the complex spectra derived from different paramagnetic species.

(HP)Ge Measurement of spectra for diagnostic X-ray beams.

The X-ray spectra applied in diagnostic radiology to the energy range between 50 and 125 kVp, were experimentally determined using a high-purity germanium detector, (HP)Ge, coupled to a multichannel analyser. A simple stripping procedure was implemented, according to that described by Seelentag and Panzer, to correct the pulse height distribution and then to determine the photon spectra. The measurements were performed for those conditions where the X-ray beam is transmitted through Pb filters 0.2-0.7 mm thick. It was necessary to estimate the effective dose in the same way that it is done for radiology diagnosis room shielding projects. The spectra were also determined to the X-ray qualities recommended by the IEC for primary diagnostic X-ray and for X-ray beams attenuated by aluminium filters 2.5-42.5 mm thick. The spectra obtained were compared with data derived from the literature presenting good agreement.

Studies of UV induced phototransferred thermoluminescence in CaSO4:Dy pellets.

The ultraviolet (UV) radiation response of the CaSO4:Dy pellets produced at IPEN/SP was studied using phototransferred thermoluminescence (PTTL). The PTTL characteristics of three different types of CaSO4:Dy pellets were investigated. The main parameters studied were: thermal treatments, post UV exposure storage time, PTTL response as a function of gamma dose, exposure time, radiant energy response and lower detection limits.

TL response study of the CaSO4:Dy pellets with graphite for dosimetry in beta radiation and low-energy photons fields.

The CaSO4:Dy is a good thermoluminescent dosimeter because of its high sensitivity and low cost. With graphite in the pellets it is possible to reduce the energy dependence. The sensitivity and energy dependence of the different thicknesses of CaSO4:Dy pellets was studied with different amounts of graphite. The results have shown the optimal quantity of the graphite and the appropriate thickness of the pellets that can be used in dosimetry of beta field, photons or both simultaneously.

Induced effects in ionization chamber cables by photon and electron irradiation.

Photon and electron irradiation effects in cables and connectors of ionization chambers were investigated under different experimental conditions by means of measurements of the chamber response to a 90Sr standard check source and by measurements of radiation-induced leakage current. Correction factors for irradiation effects on cables and connectors were obtained as a function of the radiation energy, cable length, and absorbed dose dependences.

Absorbed dose dependence of the correction factors for ionization chamber cable irradiation effects.

A simple method was developed, for possible use by hospital physicists, to evaluate the irradiation effects on cables and connectors during large-radiation-field dosimetry with ionization chambers and to determine correction factors for the used system or geometry. This method was based on the absorbed dose dependence of the correction factor.

Measurement of the exposure rate due to low energy x-rays emitted from video display terminals.

Thermoluminescent dosimeters of CaSO4:Dy have been used to measure the low energy x-rays emitted from Video Display Terminals (VDTs). For each terminal, three points were measured with five dosimeters at each point. The points were at distances of 5 and 50 cm in front of the screen and at 65 cm with an angle of approximately 50 degrees. The last two positions approximate to positions of the lenses of the eye and the gonads respectively. A survey of 50 VDTs at a distance of 5 cm from the screen resulted in exposure rates nearly fifteen times below the exposure rate of 0.5 mR h-1 (0.129 microC kg-1h-1) which is the limit recommended by the International Atomic Energy Agency (IAEA), Safety Series No. 9 (1967) Basic Safety Standards for Radiation Protection.