Nuclear Medicine Notation and Glossary

Notation

• Recall notation pertaining to elements from Chemistry/Table of Elements.
  • General language is described as ${}_{\text{Z}}^{\text{A}}\text{X}$, e.g. ${}_2^4\text{He}$
• Radionuclide production shorthand notation: ${}^{18}\text{O}(p,n){}^{18}\text{F}$
  • ${}^{18}\text{O}$ is the “target”/starting material, e.g. U-235
  • First position within parentheses is the bombarding particle (either a neutron or proton), which in this example is a proton ($p$)
  • Second position within parentheses is the emitted particle(s), which in this example is a neutron designated by $n$
  • ${}^{18}\text{F}$ is the initial radionuclide (could decay to a secondary radionuclide)

Glossary

• Specific Activity
  • the radioactivity per mass of the compound, e.g. Millicuries per gram (mCi/mg)
  • enables us to do tracer imaging without having a physiologic response in the body
• Carrier or Carrier-Free
  • Carrier has a stable isotope mixed in with the decaying isotope
  • Carrier Free means that the starting target material can be separated completely from the product material and you have no stable atoms that are the same element as what we’re trying to radiolabel.
• Byproduct Material
  • Encompasses accelerator products

Nuclear Fission

• ${}_{92}^{235}\text{U}+{}_0^1\text{n}\to {}_{92}^{236}\text{U}\to {}_{42}^{99}\text{Mo}+{}_{50}^{133}\text{Sn}+4{}_0^1\text{n}$
• See Reactor-Produced Isotopes. In this context, it is the most abundant way that we get molybdenum, which is the parent of Technetium. This is a predominant way that we procure Technetium-99 for our Technetium labellings.
• Uranium-235 can be subject to a lot of regulations by the State Department and other countries. There is only one that is the Missouri University of Research Reactor in the United States and the rest of these are outside the country.

Neutron Bombardment

• Here, you are starting with a target other than Uranium-235 that doesn’t undergo nuclear fission. And you’re reaching a neutron flux adding a neutron increasing the mass of the product, but not necessarily changing the product for separation.

Scintigraphy

• Scintigraphy
  • All nuclear imaging systems utilize scintillation detectors
  • These detectors consist of a scintillator crystal coupled to a photodetector
  • The scintillation crystal converts gamma radiation into visible light, which is detected and converted into an electric signal
  • 
• Image quality largely determined by the signal-to-noise ratio
• The greater the sensitivity of a system, the higher the counts, the higher the signal to noise ratio
• CZT crystals have negligible decay time (near instantaneous) and highest output compared to other scintigraphy cyrstals.