Local artificial body for radiation analysis and testing (LABRAT ^® ): additive manufacturing and dosimetric measurements of a heterogeneous mouse model phantom for pre-clinical radiation research

<i>Purpose</i>. This study presents a novel method for fabricating a heterogeneous, tissue-equivalent mouse phantom model using additive manufacturing, together with dosimetric verification for applications in dosimetry for pre-clinical radiation research.<i>Methods</i>. Local Artificial Body for Radiation Analysis and Testing (LABRAT^®) mouse phantoms were developed based on the Digimouse model. After 3D rendering, a mold-and-assemble method of additive manufacturing was done using 1:1.3 polyurethane-resin material for lung tissue, 1:1 resin-hardener mixture for soft tissue, and resin with 30% hydroxyapatite for bone. Three types of phantoms were developed: LABRAT A (full mouse), LABRAT B (with ionization chamber provision), and LABRAT C (with axial slices along the head, upper lung, lower lung, abdomen, and spine for film dosimetry). Ionization chamber measurements were performed on LABRAT B under total-body irradiation (TBI) (0.5-2.0 Gy) using 130 kVp, 5.0 mA x-rays at a 23 cm source-to-phantom distance on top of a 5 cm PMMA slab. Film calibration and 2.5 Gy TBI were also conducted on LABRAT C to obtain axial dose maps. Computed tomography (CT) images were obtained, and CT numbers of the phantoms were extracted using Slicer 5.4.0.<i>Results</i>. The fabrication method produced identical LABRAT^®phantoms suitable for pre-clinical dosimetry. In the open field plan, the measured dose for the LABRAT B phantom inside the acrylic mouse restrainer was observed to agree by up to ±2.6% of the prescribed dose. Film images revealed the corresponding dose maps in each axial slice, which show gradients corresponding to doses of 0 to 3 Gy. Mean CT numbers were -621 ± 119 HU (lung), 70 ± 40 HU (soft tissue), and 430 ± 138 HU (bone).<i>Conclusion</i>. A heterogeneous mouse phantom was successfully developed and validated for dose verification in pre-clinical irradiation. LABRAT^®materials demonstrated appropriate anatomical and radiological equivalence, with accurate dosimetric performance and good geometric agreement with the Digimouse model.