radiology:
The medical specialty that deals with the acquisition and interpretation of imaging studies of the human body using either
- external photon sources (X-rays, CT-scans)
- internal photon sources (nuclear medicine)
- magnetic resonance (MRI)
- Ultrasound
Also, the specialty that uses imaging guidance for the treatment of various medical conditions (interventional radiology).
nuclear medicine:
The medical specialty that uses 'open radiation sources' (radiation sources you cannot 'pick up with tweezers' because they are typically in some liquid solution) to acquire and interpret images of physiologic processes in the human body. Also, the medical specialty that uses open radioisotopes to treat disease (e.g. conditions of the thyroid, certain cancers)
radiation oncology:
The medical specialty that uses either external beam radiation (with photons, protons, neutrons, heavy ions) to treat predominantly malignant conditions. Also, the specialty that uses implantable 'closed radiation sources' (sources you can 'pick up with tweezers') to treat various forms of cancer. It is a patient care specialty that works in conjunction with surgeons and medical oncologists in the treatment of cancer.
