BIOLOGICAL AND IMAGING CHARACTERISTICS AND RADIATION-DOSE RATES ASSOCIATED WITH THE USE OF TC-99M-LABELED IMIDODIPHOSPHATE IN THE HORSE

The biological and imaging characteristics of technetium-99m imidodiph osphate (Tc99m-IDP) were measured in 4 horses once and in 1 horse twic e, All computational results are expressed with 95.5% (mean +/- 2 SD) confidence limits. The clearance half-time of the radiopharmaceutical from the blood was 29.6 +/- 2.3 min. The percentage of the administere d dose circulating in the whole-blood volume at 4 h was 3.9 +/- 0.8%. The Tc99m-IDP radioactivity confined to the plasma fraction of the who le blood at 4 h was 85.3 +/- 1.6%. At 8 h, approximately 45 +/- 16% of the dose administered had been excreted via the urine, The mean effec tive halftime of tile urine activity concentration was 1.1 +/- 0.3 h. The ratios of bone-to-soft tissue activities increased with time posti njection. Urinary radioactivity concentration measurements and radiati on dose rate measurements immediately behind the elbows were analysed and it was determined that 24 h is an appropriate radioisolation time for mature horses administered 3.7 GBq (100 mCi) Tc99m-IDP.