Figure 3
Enhancing sample contrast with sample stains and inline phase contrast. (A–E) Rat spinal cord samples stained with different heavy atom X-ray contrast agents and reconstructed from 6,000 projections with minimal phase contrast (20 mm PD is the minimum practical distance between the sample centre and the lens mounted scintillator to avoid collision during rotation) including (A) no stain (B) gallocyanine chromalum (GC) (C) phosphotungstic acid (PTA) (D) osmium tetroxide (OsO4) and (E) 25% Lugol’s iodine (LI). LI staining enhances grey matter contrast (pink border), while osmium staining enhances white matter contrast. However, osmium cannot penetrate to the centre of tissue, forming a barrier ~1 mm from the tissue edge (yellow border). (F–O) An unstained and LI-stained sample imaged with 2,000 projections at minimal PD (20 mm), 40 mm, 80 mm, 160 mm and 320 mm propagation distances (PD). Increasing PD increases tissue contrast in both samples, revealing tissue features including fine-diameter vasculature. LI-stained samples additionally exhibited white/grey matter contrast so were deemed relatively superior.
