Imaging and dosimetric characteristics of Cu.

In recent years the use of beta-emitting radiopharmaceuticals for cancer therapy has expanded rapidly following development of therapeutics for neuroendocrine tumors, prostate cancer, and other oncologic malignancies. One emerging beta-emitting radioisotope of interest for therapy is Cu (t: 2.6 d) due to its chemical equivalency with the widely-established positron-emitting isotope Cu (t: 12.7 h). In this work we evaluate both the imaging and dosimetric characteristics of Cu, as well as producing the first report of SPECT/CT imaging using Cu. To this end, Cu was produced by photon-induced reactions on isotopically-enriched Zn at the Low-Energy Accelerator Facility (LEAF) of Argonne National Laboratory, followed by bulk separation of metallic Zn by sublimation and radiochemical purification by column chromatography. Gamma spectrometry was performed by efficiency-calibrated high-purity germanium (HPGe) analysis to verify absolute activity calibration and establish radionuclidic purity. Absolute activity measurements corroborated manufacturer-recommended dose-calibrator settings and no radionuclidic impurities were observed. Using the Clinical Trials Network anthropomorphic chest phantom, SPECT/CT images were acquired. Medium energy (ME) SPECT collimation was found to provide the best image quality from the primary 185 keV gamma emission of Cu. Reconstructed images of Cu were similar in quality to images acquired using Lu. Recovery coefficients were calculated and compared against quantitative images of Tc, Lu, and Cu within the same anthropomorphic chest phantom. Production and clinical imaging of Cu appears feasible, and future studies investigating the therapeutic efficacy of Cu-based radiopharmaceuticals are warranted.