Dynamic Characteristics of⁵⁶Fe-Particle Radiation-Induced Alterations in the Rat Brain: Magnetic Resonance Imaging and Histological Assessments

Abstract

56Fe-particle radiation-induced brain disturbances are a major health concern for astronauts during long-term space travel. The present study investigated temporal modifications within the brain after 56Fe-particle exposure using in vivo magnetic resonance imaging (MRI) correlated to histology. Male Sprague-Dawley rats were exposed to brain-only 56Fe-particle radiation. MRI including T2-weighted, diffusion-weighted, pre/postcontrast enhanced T1-weighted imaging was performed 0.25-18 months after exposure. T2 relaxation times and the apparent diffusion coefficient were quantified within the hippocampus, entorhinal cortex, retrosplenial cortex and thalamus, and correlative histopathology was then performed at each time. In the absence of visible lesions on MR images, the apparent diffusion coefficient and T2 relaxation times revealed 56Fe-particle-induced dynamic changes in all ROIs over the 18-month time course. The patterns of MR changes were spatially similar within the different regions. The temporal alterations in the apparent diffusion coefficient corresponded to the glial cell changes within the brain. Quantitative MRI provides a non-invasive approach to monitor spatio-temporal brain alterations after 56Fe-particle irradiation. The apparent diffusion coefficient appears to be a sensitive metric to reveal ongoing tissue modifications involving multiple cellular components in vivo.

Brain microstructural correlates of visuospatial choice reaction time in children

“…Lower MD has been related to higher cell density in tumours (Chenevert et al, 2006;Gibbs et al, 2009). Moreover, a recent study in rats found that over an 18-month period after radiation treatment temporal changes in ADC were negatively correlated with changes in glial cell staining in the hippocampus (Huang et al, 2010). Although MD does not measure cell density directly, these findings suggest that differences in neuronal and glial cell densities may contribute to the observed neostriatal effects in the present study.…”

Accelerated hematopoietic toxicity by high energy56Fe radiation

“…beams were horizontal. The proton and 56 Fe dosimetry was calculated at the NSRL and has been described in detail earlier (Tucker JD et al 2004, Huang L et al 2010, Peng Y et al 2009, Obenaus A et al 2008). To ensure constant LET values, mice were exposed at the entrance plateau region of the Bragg curve of the beam and beam uniformity (±2%) across the exposure field was calculated by densitometric analysis of exposure images obtained from NSRL Physics laboratory and analyzed using ImageJ v1.45g software.…”

Protective effects of blueberry- and strawberry diets on neuronal stress following exposure to 56Fe particles

“…Studies have also shown that exposing young animals to HZE particle radiation results in "accelerated aging" (Joseph et al, 1992;Poulose et al, 2011), a process where young animals exhibit behavioral and molecular changes similar to that of aged animals. Most of the studies support the role of OS and inflammation as mediators of the deficits observed in neuronal and cognitive functioning following exposure to HZE radiation; however, recent studies conclude that HZE radiation not only causes OS and inflammation, but also alters protective signaling, thereby unleashing a cascade of detrimental signals which ultimately leads to the death of neurons (Cherry et al, 2012;Huang et al, 2010).…”