SU‐F‐T‐660: Evaluating the Benefit of Using Dual‐Function Fiducial Markers for In‐Situ Delivery of Radiosenistizing Gold Nanoparticles During Image‐Guided Radiotherapy

Abstract

Purpose:Dual‐function fiducials loaded with radiosensitizers, like gold nanoparticles (GNP), offer an innovative approach for ensuring geometric accuracy during image‐guided radiotherapy (IGRT) and significantly increasing therapeutic efficacy due to controlled in‐situ release of the radiosensitizers. This study retrospectively investigates the dosimetric benefit of using up to two such dual‐function fiducial markers instead of traditional single function fiducials during IGRT.Methods:A computational code was developed to investigate the dosimetric benefit for 10 real patient tumor volumes of up to 6.5 cm diameter. The intra‐tumoral space‐time biodistribution of the GNP was modeled as in previous studies based on Fick's second law. The corresponding dose‐enhancement for each tumor voxel due to the GNP was also calculated for clinical 6MV beam configurations. Various loading concentrations (25–50 mg/g) were studied, as a function of GNP size, to determine potential for clinically significant dose enhancement. The time between initial implantation of dual‐function fiducials to the beginning of radiotherapy was assumed to be 14 days as typical for many clinics.Results:A single dual‐function fiducial could achieve at least a DEF of 1.2 for patients with tumors less than 1.4 cm diameter after 14 days. Replacing two single function fiducials with dual‐function ones at the same locations achieved at least the required minimal DEF for tumors that are 2 cm diameter in 3 patients. The results also revealed dosimetrically better fiducial locations which could enable significant DEF when using one or two dual function fiducials. 2 nm sizes showed the most feasibility.Conclusion:The results highlight the potential of tumor sub‐volume radiation boosting using GNP released from fiducials, and the ability to customize the DEF throughout the tumor by using two dual‐function fiducials, varying the initial concentration and nanoparticle size. The results demonstrate potential for employing dual‐function fiducials in the development of GNP‐aided radiotherapy.