Figure 1. Synchrotron X-ray transections.

Irradiation parameters and tissular effects. (a,b) 3D Microbeam interlacement; transparent arrows denote the trajectory of each microbeam (MB). Numbers represent the sequence of their delivery. The interlaced volume (transection) is shown in red. (c) X-ray image of a GAERS brain with two rows of 5 implanted electrodes. Transections are indicated by red bars. (d) The scan of a Gafchromic™ film shows 4 microbeams, interlaced to create a 200 μm wide, octahedral irradiated transection. (e) Radiation dose deposition profile for the 4 transections. Estimated peak dose in the transection 820 Gy, entrance dose of a single microbeam 800 Gy. (f) Gadolinium contrasted T₁ MR image of a rat after 4 transections. (g–t) Horizontal brain sections 2 months post-irradiation, haematoxylin & eosin (g), myelin stain (h); scale: 2 mm, white/grey matter limit is represented as a dashed line. Microphotographs of cortical transections (i,k) show a tissue gap (i), and myelin loss (k), while the path of a single microbeam in the contralateral hemisphere shows only loss of cell nuclei (j,l; scale: 200 μm). Immunolabelling of brain vasculature (RECA and Type IV Collagen, m,n) and neurons (NeuN, o,p) in transected (m,o) and contralateral (n,p) hemispheres (scale: 50 μm). Ultrastructural changes, as described in the text, within (q,s) and between transections (r,t). Within transection (q) extracellular space is filled with extra cellular matrix (ecm) secreted by fibroblasts (fib) and phagocytosis of dead cells by microglial cells (mic) are observed. Capillaries were intact (s) and the junctions (j) of endothelial cells (end) are closed but some vacuoles can be observed (j). Extracellular matrix and collagen fibrils (col) are observed around the capillary. Between transections (r,t), the endothelial cells of the capillaries were not damaged (r), nor the surrounding tissue, including synapses (syn) and axons (ax) (t). (TEM, magnification 12,000).