In 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. The 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. To 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.

Porphyrins and ⁶⁴ Cu have emerged as a novel synergic option for applications in PET molecular imaging.

Peptides containing the RGD sequence have high affinity for αvβ3 integrin receptors overexpressed in tumor cells. The objective of this research was to determine the biodistribution and estimate the radiation dose from ⁶⁸Ga-DOTA-E-[c(RGDfK)]2 using whole-body (WB) PET scans in humans. Methods: Five healthy volunteers (2 women, 3 men, 37.2±15.6 y, 28-65 y, 79.2±21.0 Kg, 64-115 Kg) were included. After I.V. injection of the tracer (198.3 ± 3.3 MBq), 3 successive WB (vertex to mid-thigh) PET/CT scans at 3 time points (30, 60 and 120 min) were obtained on a Siemens Biograph 16 PET/CT. Subjects did not void the bladder until the entire series of images was completed. 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. Results: The highest uptake was in the urinary bladder, followed by the liver, kidneys, and spleen, in descending order. The critical organ was urinary bladder wall. The mean effective doses (all subjects, men and women) were 34.1±4.9 μSv/MBq, 31.0±2.4 μSv/MBq, and 20.9±5.2 μSv/MBq for the no bladder voiding, 2.5- and 1-h bladder-voiding models, respectively. Conclusion: Of particular interest in this research was the visualization of the choroid plexus and ventricular system, not previously reported in humans for any RGD radiopeptide. Measured absorbed doses and effective doses are comparable to other previously reported RGD-based radiopharmaceuticals labeled with ⁶⁸Ga and ¹⁸F. Therefore, ⁶⁸Ga-DOTA-E-[c(RGDfK)]2 can safely be used for imaging integrin αvβ3 expression.