[en] A benchmark set of measured beta particle spectra for a standardised ⁶⁰Co hot particle source is presented. The spectra were obtained for conditions similar to those encountered in practical applications. The measured spectra were compared with Monte Carlo calculations using the MCNP code. These comparisons provided information to guide the selection of the optimal set-up parameters of the code. Important differences were observed in the MCNP calculated spectra when ITS and the default indexing style algorithm were used. Overall the calculations using the default mode of MCNP version 4B provide the best agreement with the measured electron spectra. (author)

[en] Comparative measurements of the beta-particle depth dose distribution for a planar ¹⁴⁷Pm source were determined using an extrapolation chamber (ECH), radiochromic dye films (RDF) and ⁷LiF ultra thin thermoluminescence dosemeters (utTLD). The absolute dose estimates provided by the ECH are in excellent agreement with respect to those obtained from RDF dosemeters. In general the agreement between the ECH and the RDF were within 10%. The depth doses initially obtained using ⁷LiF utTLD dosemeters assuming the dosemeter centre as the effective point of measurement exhibited an overestimation from 18% for the first 10 mg.cm^-2 up to 60% at 30 mg.cm^-2 with respect to the ECH measurements. However in this assumption the utTLD estimations neglected the dose gradient inside the dosemeter. In order to take this into account the observed relation between the dose rate measured for each utTLD disc and its corresponding mass thickness was used to calculate the dose rate at the disc surface. A significant improvement in terms of agreement with the absolute measurements was achieved using this approach. The much higher sensitivity of utTLDs compared with ECH and RDF make this technique particularly useful for absorbed dose measurements for low activity beta particle sources. (author)

[en] In this work we compare the Monte Carlo (MCNP4B) calculated beta-gamma depth-dose profile for a liquid ¹⁵³Sm beta-gamma source used in radiation synovectomy with the experimental depth-dose distribution obtained using radiochromic dye film dosimetry. The calculated and experimental depth-dose distribution shows a very good agreement (within 5%) in the region where the dose deposition is dominated by the beta particle component (first 800 μm depth on tissue-equivalent material). The agreement worsens, reaching a maximum deviation of 15%, at depths close to the maximum range of the beta particles. Finally the agreement improves for the region where the gamma component accounts for one-third of the total absorbed dose (depths >1 mm ). The possible contributions to these differences are discussed, as well as their relevance for the application of ¹⁵³Sm in the treatment of rheumatoid arthritis. (author)

[en] The present study attempts to compare several possible measurement techniques and MCNP Monte Carlo calculations of beta/gamma doses from test 'bench-mark' ⁶⁰Co hot particle sources. Depth-dose distributions have been obtained by ionometric measurements using ionisation extrapolation chamber (ECH) and densitometric measurements using radiation induced colour changes in radiochromic dye films (RDF). The ECH provides absorbed dose information averaged over specific areas dictated by the measuring electrode diameter (1 mm, 3 mm, 1 cm and 3 cm). The RDF displays full two-dimensional dose distributions in a single measurement with a high spatial resolution down to 25 μm. In general there was good agreement between the two measurement techniques for the doses measured close to the surface after correction due to the non-linear response of the ionisation response relative to electrode separation (mainly due to the spatially non-uniform radiation field). However the agreement is markedly worse at greater depths where the dose is dominated by the gamma ray component. The measurements and MCNP4B calculations agree within a few per cent for the surface dose rate and to within γ30% at 30 mg.cm^-2. The reasons for these differences are discussed. (author)

[en] Measurements of absorbed dose at 5 cm depth in a 30 x 30 x 30 cm³ water phantom have been performed using three independent dosimetric techniques: Fricke, alanine and radiochromic dye film (GafChromic HD-810). The measurements were carried out in the secondary standard dosimetry laboratory at ININ Mexico using a collimated ⁶⁰Co gamma source with a radiation field of 10 x 10 cm² at the phantom front surface. The source to phantom distance was set at 100 cm. The reference absorbed dose at 5 cm depth in the water phantom was obtained using a 0.6 cm³ ionisation chamber. The absorbed dose to water for the test dosimetry techniques was around 100 Gy. The deviations of the dose obtained from these dosimetry techniques were within 4%. The reasons for these deviations are discussed. (author)

[en] The thermoluminescence (TL) properties of amorphous aluminum oxide thin films subjected to ultraviolet (UV) irradiation are reported. Aluminum oxide thin films were prepared by laser ablation from an α-Al₂O₃ target using Nd:YAG laser with emission at the fundamental line. Compositional, structural and morphological properties of the obtained thin films as a function of the growth conditions have been studied. Experimental results show that amorphous aluminum oxide thin films with atomic concentrations of aluminum and oxygen close to those of stoichiometric Al₂O₃ and with splashed particles on its surface were obtained. The TL response as a function of the growth parameters has been investigated in order to improve such response. Thermoluminescence glow curves exhibited one peak centered at 174 deg. C. The results presented in this work, shows that it is possible to obtain materials in thin film form with thickness as low as 150 nm, which exhibits TL response to UV irradiation. These results suggest that aluminum oxide thin films are suitable for detection and monitoring of UV light

[en] The main thermoluminescence properties of amorphous aluminum oxide thin films prepared by pulsed laser deposition with thickness as low as 300 nm are presented. The obtained thin films were irradiated with UV (254 nm) and beta-particle radiation (⁹⁰Sr-⁹⁰Y). Thermoluminescence glow curves exhibited two peaks centered at 95 deg. C and 162 deg. C for UV irradiation. For beta-particle irradiation the thermoluminescence glow curve shows only the presence of the high temperature peak. The 162 deg. C peak shows good stability and 10% fading in the first 4 days after irradiation. A linear relationship between absorbed dose and the thermoluminescence response up to 20 Gy was observed for beta-particle irradiation. The thermoluminescence parameters obtained showed a second-order kinetics and an activation energy of 1.2 eV for the 162 deg. C peak. These properties make aluminum oxide thin films potentially attractive as an ultra-thin dosimeter for UV and beta-particle radiation

[en] The Final Aperture Superposition Technique (FAST) is described and applied to accurate, near instantaneous calculation of the relative output factor (ROF) and central axis percentage depth dose curve (PDD) for clinical electron beams used in radiotherapy. FAST is based on precalculation of dose at select points for the two extreme situations of a fully open final aperture and a final aperture with no opening (fully shielded). This technique is different than conventional superposition of dose deposition kernels: The precalculated dose is differential in position of the electron or photon at the downstream surface of the insert. The calculation for a particular aperture (x-ray jaws or MLC, insert in electron applicator) is done with superposition of the precalculated dose data, using the open field data over the open part of the aperture and the fully shielded data over the remainder. The calculation takes explicit account of all interactions in the shielded region of the aperture except the collimator effect: Particles that pass from the open part into the shielded part, or visa versa. For the clinical demonstration, FAST was compared to full Monte Carlo simulation of 10x10,2.5x2.5, and 2x8 cm² inserts. Dose was calculated to 0.5% precision in 0.4x0.4x0.2 cm³ voxels, spaced at 0.2 cm depth intervals along the central axis, using detailed Monte Carlo simulation of the treatment head of a commercial linear accelerator for six different electron beams with energies of 6-21 MeV. Each simulation took several hours on a personal computer with a 1.7 Mhz processor. The calculation for the individual inserts, done with superposition, was completed in under a second on the same PC. Since simulations for the pre calculation are only performed once, higher precision and resolution can be obtained without increasing the calculation time for individual inserts. Fully shielded contributions were largest for small fields and high beam energy, at the surface, reaching a maximum of 5.6% at 21 MeV. Contributions from the collimator effect were largest for the large field size, high beam energy, and shallow depths, reaching a maximum of 4.7% at 21 MeV. Both shielding contributions and the collimator effect need to be taken into account to achieve an accuracy of 2%. FAST takes explicit account of the shielding contributions. With the collimator effect set to that of the largest field in the FAST calculation, the difference in dose on the central axis (product of ROF and PDD) between FAST and full simulation was generally under 2%. The maximum difference of 2.5% exceeded the statistical precision of the calculation by four standard deviations. This occurred at 18 MeV for the 2.5x2.5 cm² field. The differences are due to the method used to account for the collimator effect

[en] Biotin (cis-tetrahydro-2-oxothieno[3,4-d]imidazoline-4-valeric acid) is a 244 Da vitamin found in low concentration in blood and tissue (vitamin H). The aim of this work was to synthesize ¹⁶⁶Dy/¹⁶⁶Ho-DTPA-bisBiotin to evaluate its potential as a new radiopharmaceutical for targeted radiotherapy. Dysprosium-166/ holmium-166 chloride was obtained by neutron irradiation of 20 mg of enriched Dy₂O₃ (¹⁶⁴Dy, 99 %, from Oak Ridge NL) in a Triga Mark III reactor at a flux in the central thimble of 3.10¹³ n. cm^-2 s^-1 for 20 h. Following irradiation, the target was allowed to decay for 2 days, then 100 μL of 12 N chloride acid were added and stirred for 1 min. To this solution was added 500 μL of injectable water and the whole was also stirred for 2 min. The average radioactive concentration was 332 MBq/ml. The biotin used in this investigation was covalently conjugated to diethylenetriamine pentaacetic acid (DTPA) through the use of the cyclic anhydride and lysine conjugate to biotin (biocytin) to produce DTPA-α,ω-bis(biocytin amide)(DTPA-bisBiotin). Sterile and apyrogenic V-vial was prepared to contain 2.0 mg (1.9 x 10^-3 mmol) of the DTPA-bisbiotin compound in 1.0 ml of 0.05 M bicarbonate buffer (pH 8.0) and then 20 μL of ¹⁶⁶Dy2Cl3 solution were added to the preparation. Thin Layer Chromatography aluminum cellulose sheets were utilised as the stationary phase and a ternary mixture of methanol:water:ammonium hydroxide (20:40:2) as the mobile phase. ¹⁶⁶Dy/¹⁶⁶Ho-DTPA-bisBiotin travelled with the solvent front R_f 0.9-1.0 and the Dy⁺³/Ho⁺³ species remained at the origin (R_f = 0). The biological integrity of labelled biotin was achieved evaluating its avidity for avidin in an agarose column. Stability studies against dilution were carried out by diluting the radiocomplex solution with saline and with human serum at 310 K. After 10 min and 24 h the radiochemical purity of each ¹⁶⁶Dy/¹⁶⁶Ho complex solution was determined by TLC. The complex ¹⁶⁶Dy/¹⁶⁶Ho-DTPA-bisBiotin was obtained with 99% radiochemical purity. In vitro studies demonstrated that the complex is stable after dilution in saline and in human serum. Avidity of labelled biotin for avidin was not affected by the labelling procedure. This radiocomplex could work as a stable in vivo generator system for targeted radiotherapy