Take prostate cancer cells and inject them subcutaneously into an anesthetized, immunocompromised nude mouse.
The lack of an immune response allows the injected cells to survive and multiply, forming a tumor.
The tumor cells overexpress a prostate-specific membrane antigen or PSMA, a cell-surface protein.
Take PSMA-specific antibodies conjugated to a radiotracer and inject them intravenously into the tail of the tumor-bearing mouse.
Antibodies reach the tumor cells and bind to PSMA, labeling the tumor.
Place the anesthetized mouse in a positron-emission tomography or PET scanner and obtain a scan.
The produced image shows the distribution of the radiotracer, highlighting areas of high antibody uptake, which correspond to the tumor location.