Three-dimensional microtomographic imaging of human brain cortex
  This paper describes an x-ray microtomographic technique for imaging the three-dimensional structure of the human cerebral cortex. Neurons in the brain constitute a neural circuit as a three-dimensional network. The brain tissue is composed of light elements that give little contrast in a hard x-ray transmission image. The contrast was enhanced by staining neural cells with metal compounds. The obtained structure revealed the microarchitecture of the gray and white matter regions of the frontal cortex, which is responsible for the higher brain functions. 
Ryuta Mizutani, Akihisa Takeuchi, Kentaro Uesugi, Masami Ohyama,   Susumu Takekoshi, R. Yoshiyuki Osamura, Yoshio Suzuki
physics.bio-ph physics.med-ph q-bio.NC