Abstract
BioXmark®(Nanovi A/S, Denmark) is a novel fiducial marker based on a liquid, iodine-basedand non-metallic formulation. BioXmark®has been clinically validated and reverse translated topreclinical models to improve cone-beam CT (CBCT) target delineation in small animal image-guidedradiotherapy (SAIGRT). However, in phantom image analysis andin vivoevaluation of radiobiologicalresponse after the injection of BioXmark®are yet to be reported. In phantom measurements wereperformed to compare CBCT imaging artefacts with solid fiducials and determine optimum imagingparameters for BioXmark®.In vivostability of BioXmark®was assessed over a 5-month period, andthe impact of BioXmark®onin vivotumour response from single-fraction and fractionated X-rayexposures was investigated in a subcutaneous syngeneic tumour model. BioXmark®was stable, welltolerated and detectable on CBCT at volumes≤10μL. Our data showed imaging artefacts reduced byup to 84% and 89% compared to polymer and gold fiducial markers, respectively. BioXmark®wasshown to have no significant impact on tumour growth in control animals, but changes were observedin irradiated animals injected with BioXmark®due to alterations in dose calculations induced by thesharp contrast enhancement. BioXmark®is superior to solid fiducials with reduced imaging artefactson CBCT. With minimal impact on the tumour growth delay, BioXmark®can be implemented inSAIGRT to improve target delineation and reduce set-up errors