TY - JOUR T1 - <strong>Adsorption of In-111 solution on phantom walls: Effect of concentration and pH</strong> JF - Journal of Nuclear Medicine JO - J Nucl Med SP - 4121 LP - 4121 VL - 63 IS - supplement 2 AU - Takumi Inagaki AU - Hiroshi Yamaguchi AU - Yuki Asano AU - Katsuhiko Kato Y1 - 2022/06/01 UR - http://jnm.snmjournals.org/content/63/supplement_2/4121.abstract N2 - 4121 Introduction: We previously reported the gradual adsorption of radiopharmaceuticals containing 111In on phantom walls. This adsorption may interfere with analyses using phantoms. Therefore, it is necessary to evaluate how the degree of adsorption changes depending on the properties of the solution such as the chemical form of the radiopharmaceuticals, concentration, and pH. In the present study, changes in adsorption of radiopharmaceuticals on phantom walls were investigated by varying the concentration and pH of radiopharmaceuticals containing 111In.Methods: We used 80 mL acrylic phantoms and 111In-pentetreotide, 111In-DTPA, and 111InCl3 as radiopharmaceuticals. First, three phantoms were filled with 111In-pentetreotide at concentrations of 40 kBq/mL, 100 kBq/mL, and 160 kBq/mL, respectively, with a liquid volume of 50 mL. In the same way, phantoms of 111In-DTPA and 111InCl3 were also prepared. Next, three phantoms were made acidic (pH5.0), neutral (pH7.0), and alkaline (pH8.0) by adding acetate buffer, phosphate buffer, and Tris-HCl buffer, respectively, and 111In-pentetreotide was added to the phantoms with a liquid volume of 50 mL. Similarly, phantoms of 111In-DTPA and 111InCl3 were also prepared. Planar imaging was performed on the 1st, 3rd, and 7th day of phantom preparation. Furthermore, planar imaging was also performed on the 13th day of phantom preparation after the phantom was washed with water and the radiopharmaceuticals were removed from the phantom. The total counts of adsorption sites were calculated by setting the region of interest on the planar images of the phantom with and without the solution. The adsorption rate was calculated as the total counts of the phantom without the radiopharmaceuticals against the total counts of the phantom with the radiopharmaceuticals.Results: No adsorption was observed on the planar images of phantoms with varying concentrations and pH on the 1st, 3rd and 7th day of phantom preparation. In the phantoms with the radiopharmaceuticals removed, 111InCl3 was adsorbed the most and 111In-DTPA adsorption could not be confirmed. This is because 111In-DTPA is a chelate complex and can prevent adsorption. For 111InCl3 and 111In-pentetreotide, the counts of adsorption sites increased with increasing concentration. The adsorption rate of 111InCl3 was the lowest under neutral conditions, which indicates that the adsorption of 111InCl3 can be suppressed by making the solution neutral. 111In-pentetreotide adsorption rate was the highest under neutral conditions. The adsorption rate varied depending on the radiopharmaceuticals and pH.Conclusions: The higher the concentration of radiopharmaceuticals, the more easily they are adsorbed, and the pH of the solution causes a change in adsorption. ER -