“…These metallic contrasting agents were developed for earlier imaging techniques, such as osmium tetroxide for electron transmission microscopy (Carson and Hladik, ) and Lugol's iodine (I 2 KI) for radiography and microdissection (Wallingford, ; Bock and Shear, ). However, osmium tetroxide is highly toxic, has a low penetration rate (Aoyagi et al, ), and is, therefore, used primarily for CT scanning of small objects, whereas Lugol's iodine is much less toxic, diffuses into tissues much more quickly than PMA or PTA, and has, therefore, been used preferentially for larger samples (Degenhardt et al, ; Pauwels et al, ; Descamps et al, ; Gignac et al, ). In general, higher concentrations of Lugol's iodine penetrate tissues more quickly (Gignac and Kley, ; Gignac et al, ), but they cause greater tissue shrinkage and distortion (Degenhardt et al, ; Pauwels et al, ; Vickerton et al, ; Wong et al, ; Buytaert et al, ; Descamps et al, ; Schmidbaur et al, ).…”