Nuclear medicine

A radioactive tracer is introduced into the body — by injection, ingestion, or inhalation — and accumulates in target tissue because of its chemistry, not its radioactivity. A gamma camera or PET scanner then maps where the radiation escapes, revealing metabolic activity that a structural scan cannot. The same principle runs in reverse for therapy: an isotope chosen to linger in a tumor delivers a lethal dose locally. The hard part is supply — medical isotopes have half-lives measured in hours to days, so they must be made, purified, and shipped on a schedule that leaves no slack. Most of the global supply flows through a handful of research reactors, making the chain fragile.