Marcelo B. Freitas

OSL and TL techniques combined in a beryllium oxide detector to evaluate simultaneously accumulated and single doses.

Optically stimulated luminescence (OSL) and thermoluminescence (TL) are similar techniques widely used in radiation dosimetry. The main difference between these techniques is the stimulus to induce luminescence emission: TL technique uses thermal stimulation, whereas OSL uses optical stimulation. One of the main intrinsic characteristics of the OSL technique is the possibility of reading several times the dosimetric materials with a negligible loss of signal. In the case of BeO, recent studies have shown that TL stimulation up to 250°C does not affect its OSL signal. Taking the advantages of dosimetric characteristics of BeO combined with both techniques, in this study, we demonstrated the possibility of measuring accumulated and single doses in the same BeO-based detector in order to use it to improve individual monitoring of radiation workers exposed to X-ray or gamma-ray fields. Single doses were measured using TL technique by heating the detector up to 250°C, whereas accumulated doses were estimated using OSL technique in the same detector in a relatively short time of optical stimulation. The detectors were exposed to two energies: 28keV X-rays and 1.25MeV Co-60 gamma rays. The doses estimated by OSL and TL of BeO (Thermalox 995) were compared with those obtained with LiF (TLD-100) and recorded with a calibrated ionization chamber. The results indicate that combined OSL and TL signals of BeO detectors can provide additional information of accumulated dose, with additional exploration of the advantages of both techniques, such as speed in readouts with OSL, and double-check the doses using TL and OSL intensities from BeO.

CHARACTERIZATION AND PERFORMANCE TESTS OF A NEW OSL/TL PERSONAL DOSEMETER FOR INDIVIDUAL MONITORING

&NA; We propose a personal dosemeter based on the combination of thermoluminescence (TL) and optically stimulated luminescence (OSL) detectors employing the advantages of both techniques. The new OSL/TL dosemeter using a badge manufactured in a 3D printer was tested for assessment of photon doses in simulated and actual situations of exposure. Additionally, Brazilian national performance tests adapted to the new dosemeter were run as well as the performance tests of international standards on the passive dosimetry systems. The results showed the advantages of combined OSL and TL techniques when using the three different configurations of detector combination, Al2O3/BeO, BeO/CaSO4 and Al2O3/LiF. The dosemeter allowed corrections for radiation energy without the necessity of attenuation filters, the evaluation of single and accumulated doses and the triple check of the dose values. Further, the performance tests were consistent with national and international requirements, showing the viability of application of the new dosemeter to the assessment of equivalent doses.

Abstract 1811: Cancer/testis antigens: Comprehensive expression analysis and correlation with survival in glioblastoma.

Glioblastoma (GBM) is a highly invasive and aggressive tumor which confers a dismal prognosis despite advances of current therapy. Cancer vaccines have been utilized as treatment of other tumors and might be an option for brain tumors. Cancer/testis (CTA) genes represent promising targets for immunotherapeutic approaches. They are expressed in tumors and expression in normal tissues is exclusively or preferentially restricted to testis. The expression of 31 CTA genes was investigated in 48 glioblastomas and 5 normal brain samples using RT-PCR. A tissue microarray was made and expression of a CTA was detected by immunohistochemical staining. Among the genes with no expression in normal brain CTA1 (57%), CTA2 (54%), CTA3 (44%) and CTA4 (15%) were the most expressed in glioblastomas. At least one of these four selected CTA genes was found expressed in 86% of the GBM cases. Coexpression of two, three and four CTA genes occurred in 25%, 17% and 5% of the examined GBM cases, respectively. CTA4 protein expression was identified in 13% (12/92) of GBM and was negative in all anaplastic astrocytomas (0/15), diffuse astrocytomas (0/48), pilocytic astrocytomas (0/38) and normal brain samples (0/40) evaluated. We found that CTA2-positive GBMs and tumors expressing 3-4 CTA genes presented a significantly better outcome (P = 0.032; hazards ratio = 0.53; 95% CI; 0.28 to 1.0 and P = 0.017, hazards ratio = 0.36; 95% CI, 0.17 to 0.74; respectively). Furthermore, multivariate survival analysis revealed that coexpression of 3-4 CTA genes (P = 0.044, hazards ratio = 0.3, 95%CI = 0.093-0.963), radiotherapy (P = 0.010, hazards ratio = 0.16, 95%CI = 0.04-0.65) and chemotherapy (P = 0.001, hazards ratio = 0.10, 95% CI = 0.03-0.41) remained as independent predictors of overall survival. In conclusion, CTAs are potential targets for immunotherapy in patients with GBM, 86% of the cases examined expressed at least one of four selected CTA genes. The presence of 3-4 CTA genes was associated with better survival, suggesting that these genes might elicit an immune response against GBM. Supported by FAPESP(Grant 2010/20218-2 and 2011/15118-1). Citation Format: Marcelo Freitas, Thais P. Biassi, Suzana M.F Malheiros, Joao N. Stavale, Fernando T. Zamuner, Maria D.F.S Begnami, Fernando A. Soares, Andre L. Vettore. Cancer/testis antigens: Comprehensive expression analysis and correlation with survival in glioblastoma. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 1811. doi:10.1158/1538-7445.AM2013-1811