Development and characterization of modular mouse phantoms for end-to-end testing and training in radiobiology experiments

Abstract

Objective. In radiation oncology, experiments are often carried out using mice as a model for in-vivo research studies. Due to recent technological advances in the development of high-precision small-animal irradiation facilities, the importance of quality assurance for both dosimetry and imaging is increasing. Additive manufacturing (AM) offers the possibility to produce complex models from a three-dimensional data set and to build cost-effective phantoms that can easily be adapted to different purposes. The aim of this work was therefore to develop detailed anatomical mouse models for quality assurance and end-to-end testing of small-animal irradiation and imaging by means of AM. 
Approach. Two mouse phantom concepts were designed, constructed, and examined for this purpose. The first model includes cavities corresponding to the most important organs. The final solid model was constructed using AM in two separate parts that can be attached with a plug connection after filling these cavities with tissue-equivalent mixtures. Moreover, different radiation dosimeters can be placed in the lower part of the model. For the second concept, AM was used for building modules like the phantom outer shell and bones, so that different mixtures can be used as a filling, without modifying the phantom structure. Main results. CT as well as Micro-CT scans of both concepts showed an excellent quality and adequate image contrast, with material attenuation properties close to those of mouse tissues, apart from the current bone surrogates. Radiation dose measurements with radiochromic films were, with some exceptions in areas with larges bone volumes, in agreement with calculations within less than ± 4 %. Significance. AM shows great potential for the development of mouse models that are inexpensive, easy to adapt, and accurate, thus enabling their use for quality assurance in small-animal radiotherapy and imaging. The introduction of such 3D-printable mouse phantoms in the workflow could also significantly reduce the use of living animals for optimization and testing of new imaging and irradiation protocols.