Abstract
BackgroundIn recent years, Copper-64 (T1/2 = 12.7 h) in the chemical form of copper dichloride ([64Cu]CuCl2) has been identified as a potential agent for PET imaging and radionuclide therapy targeting the human copper transporter 1, which is overexpressed in a variety of cancer cells. Limited human biodistribution and radiation dosimetry data is available for this tracer. The aim of this research was to determine the biodistribution and estimate the radiation dosimetry of [64Cu]CuCl2, using whole-body (WB) PET scans in healthy volunteers. Six healthy volunteers were included in this study (3 women and 3 men, mean age ± SD, 54.3 ± 8.6 years; mean weight ± SD, 77.2 ± 12.4 kg). After intravenous injection of the tracer (4.0 MBq/kg), three consecutive WB emission scans were acquired at 5, 30, and 60 min after injection. Additional scans were acquired at 5, 9, and 24 h post-injection. Low-dose CT scan without contrast was used for anatomic localization and attenuation correction. OLINDA/EXM software was used to calculate human radiation doses using the reference adult model.ResultsThe highest uptake was in the liver, followed by lower and upper large intestine walls, and pancreas, in descending order. Urinary excretion was negligible. The critical organ was liver with a mean absorbed dose of 310 ± 67 μGy/MBq for men and 421 ± 56 μGy/MBq for women, while the mean WB effective doses were 51.2 ± 3.0 and 61.8 ± 5.2 μSv/MBq for men and women, respectively.ConclusionsTo the best of our knowledge, this is the first report on biodistribution and radiation dosimetry of [64Cu]CuCl2 in healthy volunteers. Measured absorbed doses and effective doses are higher than previously reported doses estimated with biodistribution data from patients with prostate cancer, a difference that could be explained not just due to altered biodistribution in cancer patients compared to healthy volunteers but most likely due to the differences in the analysis technique and assumptions in the dose calculation.
Highlights
In recent years, Copper-64 (T1/2 = 12.7 h) in the chemical form of copper dichloride ([64Cu]Copper dichloride (CuCl2)) has been identified as a potential agent for PET imaging and radionuclide therapy targeting the human copper transporter 1, which is overexpressed in a variety of cancer cells
The aim of the current research is to estimate the human radiation dosimetry of [64Cu]CuCl2, using biodistribution data obtained from serial WB PET/CT scans in healthy volunteers
Given the injected activity and the apparent molar activity of the [64Cu]CuCl2 used in this research, the administered copper was in trace amount, on the order of nanomoles, which fall well below the known toxicity limit for copper ions
Summary
The aim of this research was to determine the biodistribution and estimate the radiation dosimetry of [64Cu]CuCl2, using whole-body (WB) PET scans in healthy volunteers. Capasso et al obtained human biodistribution data from patients with prostate cancer and estimated radiation doses, but the main purpose of Capasso’s research was not to perform the dosimetry but to investigate the role of [64Cu]CuCl2 PET/CT in staging of prostate cancer [8]. The dosimetric calculations were performed with limited data points, which limit the confidence in the data curve-fitting for determining the time-integrated activity coefficients in source organs They included seven patients acquiring emission scans of abdomen and pelvis at 10 min for all patients, while whole-body (WB) PET/CT scans at 1, 3, and 24 h were acquired in only two patients. To the best of our knowledge, there are not any reports on radiation dosimetry estimates based on normal biodistribution data from healthy volunteers
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