Optically stimulated dosimeters for small field audits in radiotherapy

Dosimetry audits play a vital role in ensuring precision and accuracy in radiation therapy. Most existing protocols for these audits are designed for conventional radiation fields using luminescent radiation detectors. This study aims to broaden the application of optically stimulated luminescent dosimeters by developing an audit protocol that employs nanodots® for non-conventional and small photon fields. To achieve this, the audit focused on field sizes ranging from 1.0 cm × 1.0 cm–10.0 cm × 10.0 cm. Monte Carlo simulations analyzed the behavior of nanodots® by considering important factors such as material density, partial volume averaging effects, detector geometry, and detector positioning during irradiation. External radiotherapy centers volunteered to help validate this protocol by conducting experimental measurements. The results show that using nanodots® in non-conventional or small fields provides reliable measurements within 5 % for field sizes down to 1.0 × 1.0 cm. We do not recommend using fields smaller than 1.0 × 1.0 cm because various issues may compromise measurement reliability. Density and volume averaging effects as perturbation factors can lead to measurement deviations of up to 12 %. Significant deviations also occur with very slight displacements in detector positioning, reaching up to 31 % for a 2 mm displacement.