This invention relates to photochromic filaments composed of the lithium salt of a conjugated, polymerizable polyacetylene having a carboxylic acid or carboxylate terminal group wherein the length to width ratio of said filaments is between about 5000:1 and about 5:1 and the average length of the filament is up to about 5 cm. The invention also pertains to the use of said salts in maximized radiation sensitivity for imaging, radiation dose measurement or mapping and detection of radiation fields.