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Abstract: 127-1

127-1

Obtaining The Calibration Curve Of The X-Ray Generator PANTK/SEIFERT Model ISOVOLT 160 Kv Using The Maximum Energy Photon Search Technique

Authors:
Marcus Tadeu Tanuri de Figueiredo (CDTN - Centro de Desenvolvimento da Tecnologia Nuclear) ; Bruno Melo Mendes (CDTN - Centro de Desenvolvimento da Tecnologia Nuclear) ; Maria do Socorro Nogueira (CDTN - Centro de Desenvolvimento da Tecnologia Nuclear)

Abstract:

Obtaining The Calibration Curve Of The X-Ray Generator GE Model ISOVOLT 160 Kv Using The Maximum Energy Photon Search Technique.
MTT Figueiredo*, BM Mendes*, MS Nogueira*
*Centro de Desenvolvimento da Tecnologia Nuclear CDTN/CNEN

According to the principles of radiological protection, practices involving ionizing radiation must be planned and executed in a way that individual dose values, the number of exposed people, and the probability of accidental exposures are as low as reasonably achievable [1]. Therefore, it is necessary that reliable dosimetric quantity meters be used in the execution of radiation dosimetry. This reliability depends not only on the calibration of the meter but also on its performance under certain test conditions. The International Organization for Standardization (ISO) has established sets of reference X-ray beams for dosimeter calibration and testing[ 2] , whose implementation in metrology laboratories must meet specific technical requirements. The implementation of a reference X-ray beam is a procedure for adjusting the irradiation system to produce beams whose characterization parameters meet the requirements defined by the standardization body. One of the important characterization parameters of a characteristic X-ray beam is tube potential.[2] There is a technical difficulty in measuring high voltages, values in the tens or hundreds of kilovolts range[3]; generally, laboratories use the voltmeter from the irradiation systems, whose calibration was done by the manufacturer, and after some time of use, questions may arise about its validity. The updated ISO 4037-1 standard in 2019 does not recommend the use of high-resolution spectrometry systems as they are considered less accurate than voltage dividers.[2]
On the other hand, most calibration laboratories do not have technical support to perform measurements according to ISO 4037-1, with spectrometry being a reasonable resource for checking tube potential and approximating other beam characterization parameters to standard values, an indicator of the technical validity of this methodology. In this work, the maximum energy photon search technique was applied to the irradiation system of LCD/CDTN composed by the X-ray generator PANTAK/SEIFERT model ISOVOLT 160 kV.[4] Maximum energy photons were searched through corrected spectra from 19 spectra between 36 kV and 152 kV, and a calibration curve was obtained through linear regression. Beams with corrected voltage values were compared with uncorrected beams and indicated an approximation not only of expected maximum energy photons but also of beam characterization parameters (HVL, average energy, homogeneity coefficient)[5], demonstrating that despite not being a methodology recommended by ISO standard, it can be applied, with due care, when there are strong indications of discrepancies between values indicated by the equipment generator's voltmeter and expected values in the analysis of acquired spectra corrected, by reliable methodologies.

Keywords:
 Tube voltage, calibration , X Ray generator , Linear fit