Evaluation of dose dependent structural changes in 3D brain micro-vasculature in response to heavy particle radiation exposure

Space radiation with high energy particles (cosmic rays) presents a significant hazard to spaceflight crews. Recent reviews of the health risk to astronauts from ionizing radiation concluded that there is a need to establish a level of risk which may indicate the possible performance decrements and decreased latency of late dysfunction syndromes of the brain. A hierarchical imaging approach developed at ETH Zürich and PSI, which relies on synchrotron based X-ray Tomographic Microscopy (SRXTM), was used to visualize and analyze 3D vascular structures down to the capillary level. Various morphological parameters, such as overall vessel volume, thickness and spacing, are extracted to characterize the vascular structure within a region of interest. Three weeks after irradiation a first quantification of the effect of high energy particles on the vasculature was done on a set of 14 animals, all the same age. The animals were irradiated head-only with 1Gy, 2Gy and 4Gy of 600Mev/n ⁵⁶Fe heavy particles simulating the space radiation environment. We found that with increasing dose the diameter of vessels and the overall vessel volume are decreased whereas the vessel spacing is increased. As these parameters reflect blood flow in three-dimensional space they can be used as indicators for the degree of vascular efficiency which is thought to have an impact on the function and development of the central nervous system.