Monte Carlo calculation of LiF:Mg,Cu,P thermoluminescent dosimeter correction factors for 18F, 131I and 90Y submersion dosimetry

Accurate measurement of absorbed dose from beta-emitting therapeutic radionuclides is important to ensure safe and effective delivery to patients. Thermoluminescent dosimeters (TLDs) are a commercially available option to measure dose, but several confounding factors complicate this process. To preserve their integrity during the measurement, it is necessary to enclose TLDs in a waterproof envelope, which unavoidably attenuates the beta particles. Additionally, the exclusion of radioactivity in the volume occupied by the TLD, the finite volume effect, further complicates the measurement. The purpose of this study is to calculate the correction factors to convert the TLD measured dose to the absorbed dose in water, D_w, for three common radionuclides and the LiF:Mg,Cu,P TLD (Thermo Fisher Scientific™, Waltham, MA). Correction factors were calculated for four different size LiF:Mg,Cu,P TLD dosimeters inside a PMMA cylindrical phantom with ⁹⁰YCl₃, C₆H₁₁¹⁸FO₅, and Na¹³¹I aqueous solutions. Specific correction factors are required to account for finite volume, energy, and geometry for each LiF:Mg,Cu,P TLD size, radionuclide, and phantom geometry combination. Additionally, for the PMMA phantom, specific material correction factors are also required to account for the additional materials inside the phantom. The absorbed dose calculations performed with LiF:Mg,Cu,P TLDs showed good agreement with Monte Carlo simulations. Overall, these findings contribute to improving the accuracy of absorbed dose measurements from beta-emitting radionuclides in liquid solutions using TLDs.