The reasoning
- Radiopharmaceutical = radionuclide (emits detectable radiation) + pharmaceutical (determines biodistribution).
- Ideal diagnostic radionuclide: pure gamma emitter (no particulate dose), energy 100–200 keV (camera‑efficient, penetrates tissue), half‑life matched to the study (hours), easy chemistry, cheap and available.
- Gamma camera: collimator (lead, accepts parallel photons) → NaI(Tl) scintillation crystal → photomultiplier tubes → position and energy logic.
- Planar (2D, overlapping), SPECT (rotating heads, tomographic, better contrast/localisation), SPECT‑CT (attenuation correction + anatomy).