Monte Carlo Dose Simulation for In-Vivo X-Ray Nanoscopy

In-vivo x-ray microscopy (XRM) studies can help understanding the bone metabolism of living mice to investigate treatments for bone-related diseases like osteoporosis. To adhere to dose limits for living animals and avoid perturbing the cellular bone remodeling processes, knowledge of the tissue-dependent dose distribution during CT acquisition is required. In this work, a Monte Carlo (MC) simulation-based pipeline is presented, estimating the deposited energy in a realistic phantom of a mouse leg during an in-vivo acquisition. That phantom is created using a high-resolution ex-vivo XRM scan to follow the anatomy of a living animal as closely as possible. The simulation is calibrated on dosimeter measurements of the x-ray source to enforce realistic simulation conditions and avoid uncertainties due to an approximation of the present number of x-rays. Eventually, the presented simulation pipeline allows determining maximum exposure times during different scan protocols with the overall goal of in-vivo experiments with few-micrometer isotropic CT resolution.