Why is Tc-99m ideal for radionuclide imaging? Technetium-99m (Tc-99m) is ideal for radionuclide imaging because it has a combination of physical and radiological properties that optimise image quality while minimising radiation dose. It emits a single gamma photon of 140…
What is radioactive activity and how is it measured? Radioactive activity is the rate at which unstable nuclei in a sample undergo radioactive decay. It represents the number of nuclear disintegrations occurring per unit time. The SI unit of activity…
What is effective half-life? Effective half-life is the time required for the activity of a radionuclide within the body to fall to half its initial value, taking into account both radioactive decay and biological clearance. It represents the combined effect…
What is biological half-life? Biological half-life is the time required for half of a substance to be eliminated from the body due to biological processes such as metabolism and excretion. Unlike physical half-life, which depends on nuclear decay, biological half-life…
What is physical half-life? Physical half-life is the time required for half of the radioactive nuclei in a sample to undergo decay. It is a fixed property of a given radionuclide and does not depend on external conditions such as…
Why does PET not require a collimator? PET does not require a physical collimator because it uses electronic collimation through coincidence detection. When a positron annihilates with an electron, it produces two 511 keV photons that travel in nearly opposite…
What is coincidence detection in PET? Coincidence detection is the method by which PET scanners identify and record pairs of gamma photons produced during positron annihilation. When two 511 keV photons are detected simultaneously (within a very short time window)…
What happens during positron annihilation? Positron annihilation occurs when a positron (the antimatter counterpart of an electron) encounters an electron. The two particles destroy each other, and their mass is converted into energy in the form of two gamma photons,…
What is isomeric transition? Isomeric transition is a type of radioactive decay in which an excited nucleus releases excess energy without changing its number of protons or neutrons. The nucleus remains the same element and isotope but moves from a…
What is electron capture? Electron capture is a type of radioactive decay in which a proton inside an unstable nucleus captures an inner-shell electron (usually from the K shell) and is converted into a neutron. As a result, the atomic…
