TY - JOUR
T1 - Adsorption of metallic radionuclides on plastic phantom walls
AU - Park, Mi Ae
AU - Mahmood, Ashfaq
AU - Zimmerman, Robert E.
AU - Limpa-Amara, Naengnoi
AU - Makrigiorgos, G. Mike
AU - Moore, Stephen C.
N1 - Funding Information:
This work was supported in part by the National Institutes of Health under Grant Nos. R01-EB001989, R01-CA119334, and S10-RR017224.
PY - 2008
Y1 - 2008
N2 - Metal radionuclide solutions at neutral pH adhere to plastic containers. Adsorption of radionuclides on the walls of phantoms leads to a nonuniform activity distribution, which could adversely affect imaging studies, as well as phantom-based validations of absorbed dose calculations used in radioimmunotherapy, requiring accurate knowledge of the underlying activity distribution. In the work reported here, the authors determined the degree of metal chelation required to minimize metallic radionuclide oxide formation and adsorption on phantom walls in order to yield more reliable experimental data for validating image-based dosimetry. Using hollow spherical plastic phantoms, the authors evaluated three different radionuclides, I-131, In-111, and Y-90, in solutions containing three different concentrations of the chelator, ethylenediaminetetraacetate (EDTA). Adsorption to plastic walls was determined using μSPECT imaging and/or by counting aliquots of solutions. Reconstructed images and measurements of I-131 activity showed that it was uniformly distributed within all spheres; however, images of In-111 in 0.25-μM EDTA indicated that the activity concentration near the wall was much higher than that in the middle of the sphere. The decrease in activity concentration near the center of the spheres was ∼47%. Y-90 in 0.25-μM EDTA behaved similarly; the activity concentration of Y-90 decreased by 46%. For an In-111 or Y-90 radioactivity concentration of 0.74 MBq/mL, a 2.5-μM EDTA solution was required to achieve a uniform distribution, suggesting that, under our experimental conditions, ∼700 EDTA molecules were required for each radiometal atom to prevent precipitation and adsorption on poly(methylmethacrylate). For certain radiometals, e.g., In-111 or Y-90, adequate chelation is essential to achieve uniform activity concentration values and homogeneous distribution within the phantom compartments.
AB - Metal radionuclide solutions at neutral pH adhere to plastic containers. Adsorption of radionuclides on the walls of phantoms leads to a nonuniform activity distribution, which could adversely affect imaging studies, as well as phantom-based validations of absorbed dose calculations used in radioimmunotherapy, requiring accurate knowledge of the underlying activity distribution. In the work reported here, the authors determined the degree of metal chelation required to minimize metallic radionuclide oxide formation and adsorption on phantom walls in order to yield more reliable experimental data for validating image-based dosimetry. Using hollow spherical plastic phantoms, the authors evaluated three different radionuclides, I-131, In-111, and Y-90, in solutions containing three different concentrations of the chelator, ethylenediaminetetraacetate (EDTA). Adsorption to plastic walls was determined using μSPECT imaging and/or by counting aliquots of solutions. Reconstructed images and measurements of I-131 activity showed that it was uniformly distributed within all spheres; however, images of In-111 in 0.25-μM EDTA indicated that the activity concentration near the wall was much higher than that in the middle of the sphere. The decrease in activity concentration near the center of the spheres was ∼47%. Y-90 in 0.25-μM EDTA behaved similarly; the activity concentration of Y-90 decreased by 46%. For an In-111 or Y-90 radioactivity concentration of 0.74 MBq/mL, a 2.5-μM EDTA solution was required to achieve a uniform distribution, suggesting that, under our experimental conditions, ∼700 EDTA molecules were required for each radiometal atom to prevent precipitation and adsorption on poly(methylmethacrylate). For certain radiometals, e.g., In-111 or Y-90, adequate chelation is essential to achieve uniform activity concentration values and homogeneous distribution within the phantom compartments.
KW - Internal dosimetry
KW - Plastic phantom
KW - Radioactivity distribution
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U2 - 10.1118/1.2871191
DO - 10.1118/1.2871191
M3 - Article
C2 - 18491554
AN - SCOPUS:41449088548
SN - 0094-2405
VL - 35
SP - 1606
EP - 1610
JO - Medical physics
JF - Medical physics
IS - 4
ER -