1. A system that facilitates cross-calibrating a nuclear scanner to a gamma counter, including: a nuclear scanner that scans a radioactive calibration phantom comprising a radioactive material to acquire scan data; a gamma counter that measures a radioactivity level of a sample of the radioactive material to acquire measurement data; a processor that executes computer-executable instructions stored in a memory, the instructions including: generating one or more cross-calibration factors from the scan data and the measurement data.