Nuclear Medicine Flashcards
What are radiopharmaceuticals?
Radiopharmaceuticals portray physiology, biochemistry or pathology in the body without causing any physiological effect.
Why are radiopharmaceuticals referred to as radiotracers?
They are referred to as radiotiacers because they are given in subpharmacological doses that “trace” a particular physiological or pathological process in the body.
What do most radiophamaceuticals consist of?
Most radiopharmaceuticals are a combination of a radioactive molecule, a radionuclide, that permits external detection and a biologically active molecule or drug that acts as a carrier and determines localisation and bio-distribution.
How are certain radiotracers (e.g radioiodine) a little different to this general structure?
For a few radiotracers (e.g., radioiodine, gallium, and thallium), the radioactive atoms themselves confer the desired localisation properties.
If different types of atoms are called elements, what are different types of nuclei known as?
. Different types of nuclei are termed nuclides
How are elements and nuclides characterised?
An element is characterised by its atomic number (Z)—that is, the number of protons in the nucleus. The atomic number specifies the position of the element in the periodic table
A nuclide is characterised by its atomic number and mass number (A)—that is, protons plus neutrons in the nucleus.
What is meant by the term isotopes?
Nuclides with the same number of protons; and belong to the same element
What is meant by the term radionuclides?
Unstable nuclides; try to become stable by emitting electromagnetic radiation or charged particles during radioactive decay.
What is meant by radioactivity?
Radioactivity is the spontaneous emission of radiation given off by radionuclides.
Certain characteristics are desirable for clinically useful radiopharmaceuticals. Elaborate in regards to the radionuclide
Radionuclide decay should result in gamma emissions of suitable energy (100-200 keV is ideal for gamma cameras and 511 keV for positron emission tomography [PET]) and sufficient abundance (percent likelihood of emissions per decay) for external detection. It should not contain particulate radiation (e.g., beta emissions), which increases patient radiation dose, although beta emissions are suitable for therapeutic radiopharmaceuticals. The effective half-life should be long enough for only the intended application, usually a few hours.
The radionuclide should be carrier free; that is, it is not contaminated by either stable radionuclides or other radionuclides of the same element. Carrier material can negatively influence biodistribution and labelling efficiency. It should have high specific activity; that is, radioactivity per unit weight (mCi/mg). A carrier-free radionuclide has the highest specific activity. Technetium-99m most closely matches these desirable features for the gamma camera and fiuorine-18 for PET
Certain characteristics are desirable for clinically useful radiopharmaceuticals. Elaborate in regards to the pharmaceutical component
The pharmaceutical component should be free of any toxicity or physiological effects. The radiopharmaceutical should not disassociate in vitro or in vivo and should be readily available or easily compounded. The radiopharmaceutical should rapidly and specifically localise according to the intended application. Background clearance should be rapid, leading to good target-to-background ratios.
Should naturally occurring radionuclides or artificially produced nuclides be utilised?
Naturally occurring radionuclides (e.g., uranium, actinium, thorium, radium, and radon) are heavy, toxic elements with very long half-lives (>1000 years). They have no clinical role in diagnostic nuclear medicine. Radionuclides commonly used clinically are artificially produced.
What are the two most common ways the radionuclides are commonly produced?
Radionuclides commonly used clinically are artificially produced by nuclear fission or through the bombardment of stable materials by neutrons or charged particles.
Nuclear medicine involves the administration of radio- pharmaceuticals to patients for diagnostic and therapeutic purposes. How does diagnostic imaging and the therapeutic purposes differ in their intentions
For diagnostic imaging, radiation emitted from these radiopharmaceuticals must be detected by external detectors to determine its in vivo distribution. For therapeutic nuclear medicine, some of the emitted radiation must be absorbed by targeted tissues to achieve the desired effect.
All matter consists of atoms that contain a nucleus and orbiting electrons. What does the nucleus consist of?
The nucleus consists of two kinds of atomic particles called protons and neutrons, collectively known as nucleons
