What is the difference between nuclear medicine and radiation oncology?

NM-diagnosis: Nuclear medicine uses small amounts of radioactive materials to do imaging (mostly), (and sometimes treat patients). Radiation oncology usually uses external beam radiation to treat patients (usually cancer patients). Radiation oncology is not used for diagnosis.

Radiation Oncology : Radiation oncology is a field of medicine that is for treatment of cancer and rarely benign disease with x-rays generated from a machine or by prescribing radio pharmaceuticals (radioactive drugs). Nuclear medicine is a field of medicine that uses radioactive compounds to diagnose disease. This field of medicine can be used in cancer, heart disease, rheumatology, and even bleeding.

Not exactly: Nuclear medicine uses isotopes mainly for functional diagnoses of disorders of gall bladder, heart, brain, lungs, thyroid,bones, kidneys and bladder. Nuclear medicine has a few therapeutic uses including thyroid ablation and therapy for prostate bone metastases. Radiotherapy can involve radiation therapy with xray and proton beams, not considered part of nuclear medicine.