What does Particle, alpha mean in medical term?

Particle, alpha means: Indoor radon gas can pose a risk to lung tissue because of inhaled alpha particles that irradiate it.
(in Medical Dictionary)

What else does Particle, alpha mean?

The radioactive source of the alpha particles is not far away. Alpha particles cannot travel through paper, clothing or the protective layer of skin cells. Alpha particles aren’t considered to be an external exposure risk because they cannot penetrate the human skin. Alpha particles cannot penetrate human skin so they are not considered an “external exposure hazard.” If they’re present in sufficient quantities, however, the alpha particles can pose an internal health risk.
(in Medical Dictionary)

Particle, Alpha: Small mass made up of 2 protons + 2 neutrons.
(in Medical Dictionary)