| J Nucl Med 1998 Nov;39(11):1958-1964 |
Human biodistribution and dosimetry of the PET perfusion agent
copper-62-PTSM.
Wallhaus TR, Lacy J, Whang J, Green MA, Nickles RJ, Stone CK.
Copper-62-pyruvaldehyde bis(N4-methyl)thiosemicarbazone (PTSM) has been proposed as a
generator-produced radiopharmaceutical for perfusion imaging using PET. Several clinical
studies have demonstrated the ability of 62Cu-PTSM to quantitate myocardial and cerebral
perfusion in humans. Because 62Cu-PTSM is generator-produced, it can be provided to
clinical centers without cyclotron availability and, therefore, represents a
cost-effective, practical PET perfusion tracer for clinical applications. To assess the
safety, time-dependent biodistribution, and whole-body and organ-specific absorbed
radiation dose estimates of this tracer, a Phase I study of 62Cu-PTSM was performed using
whole-body imaging with PET in 10 healthy volunteers and with the radiopharmaceutical
delivered by a compact modular generator unit. METHODS: Five male and five female subjects
underwent a series of clinical tests and head-to-midthigh, whole-body PET scans at three
time points over 1 hr after intravenous injection of 62Cu-PTSM. Before injection of the
tracer, PET transmission scans were performed and used to correct the emission data for
attenuation. Final image data were expressed in units of mCi/cc. Using standard organ
weights, the percent injected dose per organ was calculated. Biodistribution data were
obtained at three different time points and from these data biological half-lives in
different organs were determined for calculation of radiation absorbed dose estimates.
RESULTS: The liver was seen as the critical organ receiving a dose of 0.0886 rad/mCi. This
organ defined the maximum single injected dose at 56 mCi using the limit of 5 rads to a
critical organ per study per year. The whole-body dose is 0.0111 rad/mCi, resulting in a
0.622 rad exposure with a maximum single injection dose. Only trace levels of activity
were found in the urine, which suggests low levels of urinary excretion and bladder
exposure. No significant clinical, electrocardiographic or laboratory abnormalities were
seen after the injection of 62Cu-PTSM. CONCLUSION: Copper-62-PTSM is a clinically safe
radiopharmaceutical with favorable dosimetry for human studies at injected doses
significantly above those projected for use in clinical studies.
