Radiation dosimetry (Physics)

Undoped and dysprosium doped lithium borate glass system with empirical formula (70–x) B2O3 – 30 Li2O – (x) Dy2O3 (x=0.1,0.3,0.5,0.7,1.0 mol%) were prepared using the melt-quenching technique. The dosimetric measurements were performed by irradiating the samples to 6 MV photon beam using linear accelerator (LINAC) over a dose range of 0.5–5.0 Gy. The glass series of dysprosium doped lithium borate glass produced the best thermoluminescence (TL) glow curve with the highest intensity peak from sample with 1.0 mol% Dy2O3 concentration. Minimum detectable dose was detected at 2.24 mGy, good linearity of regression coefficient, high reproducibility and high sensitivity compared to the undoped glass are from 1.0 mol% dysprosium doped lithium borate glass. The results indicated that the series of dysprosium doped lithium glasses have a great potential to be considered as a thermoluminescence dosimetry (TLD).

Nanocrystalline samples of Mn-doped CaF2 were synthesized by chemical coprecipitation method. The
impurity concentration was varied in the range of 0.5e4.0 mol%. The structure of the synthesized material
was confirmed using powder XRD analysis. TEM images of the nanoparticles show their size
occurring mostly in the range of 35e40 nm, with clusters of some impurity phases formed on annealing
of the material at higher temperatures. Detailed studies on TL showed that the structures of glow curves
depend on Mn concentrations and annealing temperatures. Optimization of the concentration and
annealing temperature showed that the sample (doped with 3.0 mol% and annealed at 673 K) has almost
a single dosimetric glow peak appearing at around 492 K. EPR and PL spectra were further studied to
understand the reasons for changes in the glow curve structures. All detailed studies on TL, PL and EPR
showed that the changes in glow curve structures are caused not only by the stress connected with the
difference in ionic radii of host Ca2þ and the guest impurity Mn3þ/Mn2þ, but are also governed by other
reasons, like diffusion of atmospheric oxygen and formation of impurity aggregates, such as, MnO2,
Mn3O4, etc. This is true not only for nanocrystalline CaF2:Mn but could also be so for the bulk CaF2:Mn
(TLD-400) and would thus help in understanding complex glow curve structure, high fading and the loss
of reusability on annealing beyond 673 K.

The aim of radiation therapy treatment planning is to achieve an optimal balance between delivering a high dose to target volume and a low dose to healthy tissues. The integral dose, conformity and homogeneity indexes, hence, are the important guidance for predicting the radiation effects and choosing the optimal treatment plan. The goal of this study is to compare and investigate the aforementioned parameters in 3DCRT vs. IMRT plan. In order to evaluate dosimetric parameters, data from five patients with prostate cancer, planned by IMRT and 3DCRT were obtained. Prescribed doses for IMRT procedure and 3DCRT were 80Gy and 70 Gy, respectively. Also, the target coverage was achieved with 95% of the prescribed dose to 95% of the PTV in 3DCRT and 95% of the prescribed dose to 98% of the PTV in IMRT method. A total of thirty IMRT and 3DCRT plans were performed for evaluation of dosimetric parameters (for each patient both treatment plans, step and shoot IMRT and 3DCRT with 6, 10 and 18MV energies) were done. The integral dose was calculated as the mean- dose times the volume of the structure. The mean integral dose (ID) received by rectum for 3DCRT was almost 1.01% greater than IMRT while in bladder mean value of ID for IMRT was approximately 1.68% higher than 3DCRT. For PTV in IMRT the ID of target volume had the biggest value (1.14%) compared to that of 3DCRT. Dose conformity in PTV volume in S.A.S and 3DCRT was almost equal. The same outcome was achieved in homogeneity index. The results of this study shows that IMRT method leads to adequate target dose coverage while the prescribed dose for this modality is higher than 3DCRT. IMRT has the ability of increasing the maximum dose to tumor region and improves conformity and homogeneity indexes in target volume and also reduces dose to OAR.

In modern CT, CTDI100 measurements would underestimate accumulated dose at the gantry center. AAPM TG 111 report proposed improved metrics for CT dosimetry, mainly for helical and wide beam width scanning. In this study, a methodology to assess CT dose, inspired on TG 111, was applied. Dosimeters were firstly calibrated in lab in beams like those utilized clinically. Using a reference 0.6cc Farmer chamber, two CT " pencil " chambers were calibrated in PKL by substitution method. Results showed differences ≤ 2% in the calibration coefficients, for three col-limation apertures. A small 0.6cc chamber was calibrated in air kerma with this setup, without any collimator. After this, in a private Brazilian hospital, the small chamber was applied in dosimetry tests of a CT scanner, according to TG 111, determining Dose profiles and Equilibrium dose free-in-air (Deq,air) for some protocols and pitch values. Results showed that Deq,air increased when reducing pitch and Equilibrium dose-pitch product free in air (p.Deq,air) remain constant. In measurements with a 450mm CT phantom, differences between Planar Average Equilibrium Dose (Deq,p) and CTDIvol ranged between 30-37%. This occurs because CTDIvol cannot include dose profile "tail" contribution, caused by scattering in phantom, especially for wide beam widths. Campelo, et. al. ● Braz. J. Rad. Sci. ● 2016 2

2nd Luminescence in Archaeology International Symposium (L.A.I.S. 2012)
Free downloaded excellent articles in luminescence from www.maajournal.com

The 2nd Luminescence in Archaeology International Symposium was hosted by the Group of
Applied Geochemistry & Luminescence on Cultural Heritage at IST/ITN, now the Campus Tecnológico
e Nuclear of Instituto Superior Técnico, Universidade de Lisboa, from the 5th to the 7th of September, 2012. Many thanks are due to all committee members, webmaster and administrative
staff.
L.A.I.S. 2012 Lisbon continued the series of symposia initiated in L.A.I.S. 2009 Delphi. 48 oral and poster presentations by 45 participants from Asia, Africa, North and South America, and across
Europe, represents moderate growth and contributes to the establishment of a fully international conference series, which will continue in L.A.I.S. 2015 Paris.
This special issue MAA 13.3 contains 16 papers: I would like to thank the colleagues who enabled double peer review of each submitted paper. These focus on the testing and development of diverse methodologies for the retrospective evaluation of absorbed dose and dose rate, in the challenging materials and environments encountered in cultural heritage contexts ranging from the art historic
to the Palaeolithic. They represent a valuable union of evidence and ideas aligned with the focus of the L.A.I.S. series of symposia: presentation and exploration of the potentialities and limitations
of luminescence and related analyses, for materials and questions of archaeological and cultural heritage significance.

Christopher I. Burbidge
Guest Editor
President of the Organizing Committee LAIS2012.
C2TN, IST, UL,
Campus Tecnológico e Nuclear,
2695-066 Bobadela-LRS, Portugal.
6th of January, 2014

Este trabajo describe las características termoluminiscentes de arena proveniente de las playas de Coveñas para su uso como dosímetro en dosis terapéuticas. Las muestras seleccionadas, tratadas térmicamente a 400◦C por una hora, fueron irradiadas a diferentes dosis usando una unidad de 60Co Theratron 780C en aire a temperatura ambiente. La lectura se realizó en un Harshaw TLD 4500. Las principales propiedades dosimétricas del material (curva de brillo, reproducibilidad de la respuesta, reutilización, linealidad y decaimiento térmico) han sido estudiadas en detalle. La curva de brillo de las muestras de arena presenta un pico TL alrededor de los 145◦C. Los resultados muestran que el material tiene una respuesta lineal con la dosis desde 50 cGy hasta 1000 cGy. Las muestras de arena estudiadas se pueden utilizar como dosímetros termoluminiscentes para aplicaciones en diferentes áreas. La importancia de este trabajo radica en que la arena es una sustancia natural disponible en grandes cantidades, tiene bajo costo y puede usarse en física clínica para evaluar la dosis recibida por el paciente durante el tratamiento médico.