Certain amino acids and chelating agents known to increase the velocity of sound in solution were assayed for median lethal dose (LD50). An estimation of each agent's ability to enhance ultrasonic image luminance in vivo was based on its ability to increase sound velocity in solution and on its LD50. The ability of the compound to increase sonogram screen luminance was tested by the infusion of each agent into a mouse being scanned, and concurrent screen luminance measurement with a photometer. The compounds were then ranked in order of their effect on the onset time for a statistically significant increase of image luminance over corresponding saline control values. The most rapid onset of increased luminance was found with the infusion of the amino acid 1-lysine hydrochloride, and the chelating agent calcium disodium edetate. The estimated rankings for these and most other compounds tested compared favorably with the observed results.
