Skip to main content

Table 1 Summary of heavy metal stains used to enhance soft tissue contrast in CT. Asterisks indicate the most commonly used stains

From: X-ray computed tomography in life sciences

Heavy metalStaining solutionBinds toStaining considerations
Iodine * [38]Iodine potassium iodide in water, ethanol or methanol. Various concentrationsNon-specific staining. Preferentially binds to lipids and glycogen.
Good for muscle fibres, nerve myelin sheath, connective tissues and the eye lens
• Rapid and deep tissue penetration
• Particularly suited to larger specimen (> 2 mm)
• An effective stain for flower parts, allowing counting of pollen ovules [39]
• Has been used to study water transport in plants [35]
Tungsten and Molybdenum* [40]Phosphotungstic acid
Phosphomolibdic acid
Proteins including fibrin and collagen. Suited to connective tissues• Moderate tissue penetration rate and depth
• Can provide more detailed visualisation compared with iodine-based stains
• Phosphotungstic acid also effective in plants [41]
Osmium* [42]Osmium tetroxide, as used in electron microscopyLipids including those in cell membranes, some proteins and nucleic acids• Tissue penetration is slow and can be limited (not suited to samples requiring a penetration depth greater than 1–2 mm)
• Highly toxic, requiring special safety considerations
Indium [43]Gallocyanin-chromalumCell nuclei. Can show cell density and individual cells• A histology stain
• Low contrast overall
Iodine, aluminium and iron [44]Verhoff’s StainArterial walls of the vascular network• A trichrome histology stain