Medical Imaging

• Technetium-99m is a radioactive isotope that is used in medical diagnosis and is suitable because of its short half life
• Iodine-123 is a radioactive isotope used in nuclear imaging and is suitable for medical use as it has a short half life
• Nitrogen-13 is used in PET scans and is suitable for medical use as it has a short half life
• Radioactive isotopes used as a medical tracer must have a short half-life but a long decay time this is because the tracer must be able to be detected after a few hours but shouldn't leave the patient as a radioactive source when dismissed.
• The isotope should be chemically identical to the substance consumed/injected so that the body does not detect it as a foreign substance and the isotope can travel through the body easily
• The radioactive isotope must decay into a stable daughter nuclei for it to be used as a medical tracer. This is so that it will not continue to decay inside the patient for longer than necessary.
• How a PET scan works is that a beta-plus emitting tracer is injected into the patient. The positrons emitted annihilates itself with an electron and releases energy in the form of two gamma photons. These gamma photons are detected by a gamma detector.
• Iodine is a contrast material
• Contrast materials increase the difference between tissues, making them easier to see on X-rays or ultrasound images
• Technetium-99m emits gamma photons