Determination of human absorbed dose of ²⁰¹Tl(III)-DTPA-HIgG based on biodistribution data in rats

To estimate the absorbed dose in normal organs and inflammated tissue following i.v. administration of [²⁰¹Tl](III)-DTPA-HIgG by using biodistribution data in inflammation-bearing rats was attempted. The percentages of injected dose per gram of each organ were calculated. The medical internal radiation dose formulation was applied to calculate the absorbed dose for various organs. The inflammated tissue to blood activity concentration ratios were about 19 and 23.3 at 24 and 28 h post-injection, respectively. A 185-MBq injection of ²⁰¹Tl-DTPA-HIgG into the human body, might result in an estimated absorbed dose of 14.4 mGy for the total body and the highest absorbed dose was in the kidney with 1195 (mGy) and second to the Spleen were the liver, the lungs and the adrenals, which received 250.5 (mGy), 58.64 (mGy) and 56.44 (mGy), respectively. Biodistribution of [²⁰¹Tl](III)-DTPA-HIgG demonstrated significant inflammated tissue uptake and low muscle and blood uptake, allowing for imaging of inflammated tissues.