Development of Ultrafast Laser-based Micro-ct System for Small Animal Imaging

We investigated performance of ultrafast (30 fs –200 fs) laser-based x-ray source as an alternative to a microfocal x-ray tube used in micro-CT systems. A number of solid targets including Ge, Mo, Rh, Ag, Sn, Ba, La, Nd with matching filters was used. We optimized conditions for x-rays generation, measured x-ray spectra and obtained images of small animals using various characteristic x-ray lines and various imaging geometries. X-ray spectra produced by ultrafast laser are advantageous for micro-CT imaging because most of the emission is in narrow characteristic lines. The spectra can be rapidly changed, via target change, and easily matched to the imaging task. X-ray fluence can exceed fluence produced by conventional microfocal tube. Effective x-ray focal spot size is about 5 μm. Good quality projection images of small animals were obtained: (a) in a single energy absorption mode with single x-ray line matching animal thickness and density, and (b) in the dual-energy absorption mode with two x-ray lines bracketing absorption energy of the I-based and Ba-based contrast agent, respectively, and (c) in the in line phase-contrast enhancing geometry using single x-ray line matching animal thickness and density. We conclude that the ultrafast laser-based, compact, x-ray source is a promising alternative to a microfocal x-ray tube in micro-CT systems. Its utilization might result in faster scans with lower radiation dose, and with better spatial and contrast resolution. In addition, it might allow practical implementation of dual-energy and phase-contrast imaging micro-CT that not possible with conventional micro-CT.