Radioisotopes such as technetium-99m are used in imaging and therapy.
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Medical isotopes are radionuclides used in diagnostic imaging and therapy. Technetium-99m, with a half-life of about 6 hours, emits gamma rays that gamma cameras detect, and it is the most widely used diagnostic isotope. Fluorine-18 emits positrons used in PET scans, iodine-131 treats thyroid disorders by destroying overactive or cancerous tissue, and cobalt-60 provides gamma rays for radiotherapy. Short half-lives limit the radiation dose to patients while still allowing imaging. Isotopes are produced in reactors or cyclotrons and must be delivered quickly.
Key ideas: Tc-99m (half-life 6 hours, gamma emitter 140 keV) is used in about 80 percent of nuclear imaging; F-18 (110 minutes, positron emitter) for PET scans as fluorodeoxyglucose; I-131 (8 days) treats thyroid; Co-60 (5.3 years) for external radiotherapy; Ga-68, Lu-177 for targeted therapy. Short half-life reduces patient dose but requires nearby production, e.g. Mo-99 generators.
Common mistakes and connections: Mistake: choosing long half-life isotopes for diagnostics; they would deliver prolonged dose. Therapy uses beta or alpha emitters to damage nearby tissue while imaging uses gamma. Activity A equals lambda times N, and decay constant lambda equals ln2 over half-life. Links to radioactive decay and radiation safety.
Technetium-99m has a half-life of about 6 hours, so it gives enough gamma rays for imaging yet decays quickly, limiting the patient's dose. The interactive lesson shows this as a live animation or chart.
Technetium-99m is used in tens of millions of diagnostic procedures every year.
Radioisotopes such as technetium-99m are used in imaging and therapy.
Medical Isotopes is a intermediate topic in Biochemistry, Environment & Industry. It builds on the vocabulary of beginner topics in this area.
Study these earlier topics in Biochemistry, Environment & Industry first: Nuclear Power, Nuclear Waste, Radiation Safety.
The next topics in Biochemistry, Environment & Industry are Industrial Chemistry and Petroleum Refining.
Yes. The interactive lesson includes a self-check question on Medical Isotopes, and the Biochemistry, Environment & Industry quiz draws on every topic in this area.
Medical Isotopes is topic 94 of 127 in Biochemistry, Environment & Industry.
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