Full text
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| Author(s): |
Josilene Cerqueira Santos
Total Authors: 1
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| Document type: | Master's Dissertation |
| Press: | São Paulo. |
| Institution: | Universidade de São Paulo (USP). Instituto de Física (IF/SBI) |
| Defense date: | 2013-08-07 |
| Examining board members: |
Paulo Roberto Costa;
Marcelo Baptista de Freitas;
Nora Lia Maidana
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| Advisor: | Paulo Roberto Costa |
| Abstract | |
The maintenance of dose levels below the limits required by national and international standards are essential in all applications of ionizing radiation. The dose constrains levels in Brazil are established in terms of the quantity ambient dose equivalent, H*(10), while the radiation levels in radiometric surveys are calculated by means of measurements with ion chambers using the quantity air-kerma converted to ambient dose equivalent by a constant factor. The present work aims the experimental study of the relationship between the air kerma and the operational quantity ambient dose equivalent, by measuring X-ray beams transmitted through materials used in dedicated chest radiographic facility. An experimental methodology, based on spectroscopic techniques was developed for the X-ray spectra measurements. With the results, estimates of ambient dose equivalent quantity through conversion factors between this quantity and the air-kerma, become more realistic by taking into account the spectral changes resulting from the attenuation of primary beams by anthropomorphic phantoms and different attenuating materials. The maximum difference founded between these coefficients and the one adopted in Brazil by ANVISA (1.14 Sv I Gy) was 53.52%, which indicates underestimation of the value. The spectral behavior of the X-ray beam transmitted by primary barriers and attenuators present in radiological procedures presented influences on results related to radiometric surveys and procedure calculations barriers. (AU) | |
| FAPESP's process: | 11/04721-9 - Experimental approach for the relation between air-kerma and ambient equivalent dose for shielding calculation of primary barriers of X-ray imaging facilities |
| Grantee: | Josilene Cerqueira Santos |
| Support Opportunities: | Scholarships in Brazil - Master |