Introduction:: Coherent X-ray scattering based imaging can discriminate between materials that would be indistinguishable in traditional, transmission-based x-ray images. However, low energy monochromatic x-ray scattering techniques lack the penetration power to scan thick targets, which presents issues for exploring novel in vivo applications, such as identifying abnormal protein aggregates in the brain or microcalcifications in the breast. Recently, our group developed a spectral small angle x-ray scattering technique (sSAXS) by combining a polychromatic x-ray source and a photon counting detector. In this study, we expand the potential of sSAXS for 2D and 3D imaging applications by performing scanning measurements using a LabView controlled sample stage.
Materials and Methods:: Our sSAXS imaging setup consists of a polychromatic x-ray pencil-beam, 80-by-80 pixel spectroscopic photon counting detector, and a LabView controlled 3-axis sample stage equipped with high-precision stepper motors. A well plate filled with four varying mixtures of caffeine and decaffeinated coffee powder (decaf) serves as the test object to showcase the imaging capability. We collected more than 400 scattering signals at an exposure time of 60 s per point and later quantified the scattering amount at each point by integrating the spectral peak at q=8.44 nm-1. The integral value at each point served as the contrast in the final reconstructed image.
Results, Conclusions, and Discussions:: Caffeine exhibited peaks at q=8.44 and 18.64 nm-1 and scattering contributions from the decaf filler were subtracted. The 2D spatial mapping captured the decrease in intensity at q=8.44 nm-1 for each decreasing caffeine concentration and correlated well with the true values for concentration (r2= 0.962).
We plan to expand our study to the 3D imaging of thicker objects using a LabView controlled 3-axis sample stage. Leveraging this sSAXS technique for medical imaging could facilitate the label-free imaging of materials in their native state for diagnostic applications.
