Radioiodinated fatty acids for heart imaging: iodine monochloride addition compared with iodide replacement labeling.

Radioiodinated fatty acids have been proposed as agents for use in heart imaging. Previous studies in experimental animals and humans using 131I-oleic acid of low specific activity were marginally successful. Higher specific activity compounds offer potential improvement for use as imaging agents for normal myocardium. Methods for preparation of high specific activity, radioiodinated fatty acids by iodine monochloride addition to oleic, linoleic, and linolenic acids, and iodide replacement of terminal bromine in 6-bromohexanoic, 11-bromoundecanoic, and 16-bromo-9-hexadecenoic acids are presented and compared. Although both labeling procedures are suitable for use with 123I, the latter synthetic route gives labeled fatty-acid analog molecules and 16-iodo-9-hexadecenoic acid appears to show improved myocardial specificity in preliminary animal studies.