Dosimetry of Copper-64-Labeled Monoclonal Antibody 1A3 as Determined by PET Imaging of the Torso

• Published in: The Journal of nuclear medicine (1978) Vol. 36; no. 12; pp. 2363 - 2371
• Main Authors: Cutler, P. Duffy, Schwarz, Sally W, Anderson, Carolyn J, Connett, Judith M, Welch, Michael J, Philpott, Gordon W, Siegel, Barry A
• Format: Journal Article
• Language: English
• Published: Reston, VA Soc Nuclear Med 01.12.1995; Society of Nuclear Medicine
• Subjects: Animals; Antibodies, Monoclonal - pharmacokinetics; Biological and medical sciences; Colorectal Neoplasms - diagnostic imaging; Copper Radioisotopes - pharmacokinetics; Humans; Investigative techniques, diagnostic techniques (general aspects); Medical sciences; Miscellaneous. Technology; Radiation Dosage; Radioimmunodetection; Radioimmunotherapy; Radionuclide investigations; Rats; Tissue Distribution; Tomography, Emission-Computed; Radionuclide study; Human; Rectal disease; Carcinoma; Exploration; Malignant tumor; Monoclonal antibody; Colonic disease; Extrapolation; Immunotherapy; Rectum; Digestive diseases; Intestinal disease; Whole body; Colon; Dosimetry; Pharmacokinetics; Positron; Emission tomography
• ISSN: 0161-5505; 1535-5667

We present biodistribution and dosimetry results for 64Cu-benzyl-TETA-MAb 1A3 from 15 human subjects injected with this tracer as determined by serial PET imaging of the torso. PET imaging was used to quantify in vivo tracer biodistribution at two time points after injection. Absorbed dosimetry calculated using MIRD-11 and the updated MIRDOSE3 was compared with estimates obtained using rat biodistribution data. By measuring activity concentrations in the torso, and extrapolating for the whole body using standard organ and tissue volumes, we were able to account for 93% of the injected radiopharmaceutical over a range of imaging times from 0 to 36 hr postinjection. Based on PET imaging and the MIRD-11 schema, the liver and spleen are the critical organs with average absorbed doses of 0.12 and 0.10 mGy/MBq (0.44 and 0.39 rad/mCi). The revised MIRDOSE3 scheme yields similar values for these and other organs but also results in a dose of 0.14 mGy/MBq (0.53 rad/mCi) to the heart wall. In the rat, the large intestine is the critical organ at 0.14 mGy/MBq (0.52 rad/mCi), while liver and kidneys each receive 0.11 mGy/MBq (0.41 rad/mCi). Some disparities in absorbed doses determined by these methods are evident but are a result of dissimilar biodistributions in rats and humans. For most organs, rat extrapolated values are higher than the human measurements with PET. This study shows that torso PET imaging can quantitatively measure the whole-body biodistribution of a radiopharmaceutical as long as it has relatively slow pharmacokinetics.