Absorbed dose measurements from a 90 Y radionuclide liquid solution using LiF:Mg,Cu,P thermoluminescent dosimeters

• Published in: Physica medica 2020-01, Vol.69, p.127
• Main Authors: D'Arienzo, Marco, Pimpinella, Maria, De Coste, Vanessa, Capogni, Marco, Ferrari, Paolo, Mariotti, Francesca, Iaccarino, Giuseppe, Ungania, Sara, Strigari, Lidia
• Format: Article
• Language: English
• ISSN: 1724-191X

In the last few years there has been an increasing interest in the measurement of the absorbed dose from radionuclides, with special attention devoted to molecular radiotherapy treatments. In particular, the determination of the absorbed dose from beta emitting radionuclides in liquid solution poses a number of issues when dose measurements are performed using thermoluminescent dosimeters (TLD). Finite volume effect, i.e. the exclusion of radioactivity from the volume occupied by the TLD is one of these. Furthermore, TLDs need to be encapsulated into some kind of waterproof envelope that unavoidably contributes to beta particle attenuation during the measurement. The purpose of this study is twofold: I) to measure the absorbed dose to water, D , using LiF:Mg,Cu,P chips inside a PMMA cylindrical phantom filled with a homogenous YCl aqueous solution II) to assess the uncertainty budget related to D measurements. To this purpose, six cylindrical PMMA phantoms were manufactured at ENEA. Each phantom can host a waterproof PMMA stick containing 3 TLD chips encapsulated by a polystyrene envelope. The cylindrical phantoms were manufactured so that the radioactive liquid environment surrounds the whole stick. Finally, D measurements were compared with Monte Carlo (MC) calculations. The measurement of absorbed dose to water from YCl radionuclide solution using LiF:Mg,Cu,P TLDs turned out to be a viable technique, provided that all necessary correction factors are applied. Using this method, a relative combined standard uncertainty in the range 3.1-3.7% was obtained on each D measurement. The major source of uncertainty was shown to be TLDs calibration, with associated uncertainties in the range 0.7-2.2%. Comparison of measured and MC-calculated absorbed dose per emitted beta particle provided good results, with the two quantities being in the ratio 1.08.