SPECT/CT imaging with 47Sc- and 177Lu-DOTANOC

In vivo experiments were approved by the local veterinarian department and conducted in accordance with the Swiss law of animal protection. Female, athymic nude mice (CD-1 nude) at the age of 5–6 weeks were obtained from Charles River Laboratories, Sulzfeld, Germany. AR42J cells (rat exocrine pancreatic tumor cells, European Collection of Cell Cultures ECACC, Salisbury, U.K.) were suspended in PBS (5 × 10⁶ cells in 100 μL) and subcutaneously inoculated on each shoulder. SPECT/CT experiments were performed about 2 weeks after tumor cell inoculation, when the tumor reached a size of about 400 mm³.

Imaging studies were performed using a small-animal SPECT camera (NanoSPECT/CT™, Mediso Medical Imaging Systems, Budapest, Hungary) as previously reported (Müller et al. 2014b). The energy peaks for the camera were set at 159.4 keV (± 10%) for the scans with ⁴⁷Sc and 56.1 keV (± 10%), 112.9 keV (± 10%) and 208.4 keV (± 10%) for the scans with ¹⁷⁷Lu. SPECT/CT scans were followed by CT scans. The images were acquired using Nucline Software (version 1.02, Bioscan Inc., Poway, California, US). The reconstruction was performed iteratively with HiSPECT software (version 1.4.3049, Scivis GmbH, Göttingen, Germany). SPECT and CT data were automatically co-registered and the fused datasets were analyzed with the VivoQuant post-processing software (version 2.50, inviCRO Imaging Services and Software, Boston, USA).

The mice were injected intravenously with ⁴⁷Sc-DOTANOC (12 MBq, 1.2 nmol, 100 μL) and ¹⁷⁷Lu-DOTANOC (40 MBq, 1.2 nmol, 100 μL), respectively. The in vivo SPECT/CT scans of 35 min duration were acquired 3 h after injection of ⁴⁷Sc-DOTANOC. During the scans, the mice were anesthetized by inhalation of a mixture of isoflurane and oxygen. Post-mortem scans of 1.3–3.5 h were performed 6 h after injection of ⁴⁷Sc- and ¹⁷⁷Lu-DOTANOC. The SPECT acquisitions were performed in such a manner to obtain the same total number of counts for each scan.