Calibración de polvo TLD-100 para energías de $^{60}$Co, $^{137}$Cs, $^{192}$Ir y RX de 250, 50 kVp en dosis absorbida en agua con fines de control de calidad dosimétrico para braquiterapia de alta tasa de dosis

S.P. Loaiza Calderón, J.T. Álvarez Romero

Abstract


To help solve the traceability and quality control dosimetric problems for the users of $^{192}$Ir sources in the Mexican Republic, the Secondary Standard Dosimetric Laboratory at ININ to calibrated a batch of powder TLD-100 (LiF:Mg,Ti) in terms of absorbed dose to water D$_{w}$ for the following radiation sources: $^{60}$Co, $^{137}$Cs and RX 250 and 50 kVp. Later on, the calibration is interpolated to obtain the $^{192}$Ir. The calibration radiation field is carried out with the following protocols: For the $^{60}$Co, OIEA TRS 398 protocol employing a secondary standard Farmer chamber PTW N30013, calibrated on D$_{w}$ at the NRC (Canada). For $^{137}$Cs the AAPM TG 43 protocol is used, in terms of air kerma strength S$_{k}$ determined by the air kerma K$_{a}$ measured with a secondary standard chamber type thimble NE2611 traceable to the NIST (USA). For Rays X 250 and 50 kVp, the protocol AAPM TG 61 using a tertiary standard Farmer chamber PTW 30001, with traceability to the LCIE (France) on air kerma K$_{a}$. The calibration curves are built for the TLD response R$_{TLD}$ vs D$_{w}$, they are fitted by means of a least squares fit technique with a second degree polynomial that corrects the supralinearity response. The curves are validated by the lack of fit test, and the Anderson Darling normality test. Later on, the sensibility factors are interpolated for the sources of $^{192}$Ir: MicroSelectron and VariSource. Two capsules are sent to two hospitals to verify a nominal D$_{w }$= 2 Gy, in the first one an underestimate of the D$_{w}$ is obtained, and in other one an overestimation is presented. Finally, the expanded uncertainty associated to D$_{W}$ and the F$_{s}$ are calculated.

Keywords


TL Dosimetry; TLD-100; Brachytherapy; HDR; absorbed dose to water; Ir

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REVISTA MEXICANA DE FÍSICA, year 67, issue 2, March-April 2021. Bimonthly Journal published by Sociedad Mexicana de Física, A. C. Departamento de Física, 2º Piso, Facultad de Ciencias, Universidad Nacional Autónoma de México, Ciudad Universitaria, Alcaldía Coyacán, C.P. 04510 , Ciudad de México. Apartado Postal 70-348. Tel. (+52)55-5622-4946, https://rmf.smf.mx/ojs/rmf, e-mail: rmf@ciencias.unam.mx. Chief Editor: José Alejandro Ayala Mercado. INDAUTOR Certificate of Reserve: 04-2019-080216404400-203, ISSN: 2683-2224 (on line), 0035-001X (print), both granted by Instituto Nacional del Derecho de Autor. Responsible for the last update of this issue, Technical Staff of Sociedad Mexicana de Física, A. C., Fís. Efraín Garrido Román, 2º. Piso, Facultad de Ciencias, Universidad Nacional Autónoma de México, Ciudad Universitaria, Alcaldía Coyacán, C.P. 04510 , Ciudad de México. Date of last modification, March 1st., 2021.

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