Which of the following is NOT a preferred radiopharmaceutical characteristic?

• A. Easy to make / cheap
• B. Photon energy (100-500 keV)
• C. Longer half life
• D. High patient dose

Answer: (D)

In radiopharmaceutical design, the goal is to obtain good diagnostic images while keeping the patient's radiation dose as low as reasonably achievable. The characteristic that most clearly undermines this goal is a high patient dose, because it directly raises risk without providing a corresponding imaging benefit.

Being easy to make and cheap supports broad use and accessibility, which is desirable for clinical practice. Photon energy in the 100–500 keV range aligns with the detectors used in common imaging systems (gamma cameras and related modalities), enabling good image quality without requiring excessive shielding or specialized equipment. A longer half-life isn’t inherently ideal because it prolongs radiation exposure, but in practice, it’s chosen to balance image timing with safety, so it’s not as clearly harmful as delivering a high dose.