What is molecular imaging?

Molecular imaging, like other nuclear medicine procedures, is a medical imaging procedure that uses physiological (functional) characteristics of body organs and tissues with reference to certain radioisotopes.

How different is it from the diagnostic imaging that we are more familiar with?

  • The diagnostic imaging modalities used in radiology rely on machine-generated radiation to capture the anatomical structure of the body system i.e. the organs, organ systems, tissues and cells.

Read: Delivery of Cyclotron Machine at KUTRRH

Which radiotracers are used for PET Scan imaging?

  • Positron Emission Tomography (PET) requires the emission of positron particles that are generally acquired by neutron deficient radioisotopes like Fluoro18 (F18) and injected into the body in the form of 2-deoxy-2-(18F) Fluoro-D glucose

How are the radiotracers produced?

  • Production of the low molecular weight PET radioisotopes (C-11, N-13, O-15 and F-18) is by charged particle bombardment. Typically, the radioisotopes are produced in a cyclotron or other accelerators.
  • The charged particles that are used are usually the nuclei of very low weight isotopes: hydrogen, deuterium or helium.
  • The hydrogen nucleus is a single proton, the deuterium nucleus is one proton and one neutron and the helium nucleus is two protons and two neutrons.

What is a cyclotron what is its principle of operation?

  • These particles have short half-life hence always produced on a proximal site by a particle accelerator called cyclotron [1].
  • This is an electrically powered machine that produces charged particles in an ion chamber in a spiral path in the centre of the machine.
  • The particles are then focused onto a target or starting material and the bombardment of the desired radioisotope i.e. [18F]. The [18F] F-target is system is designed to produce {18F} fluoride ion from the interaction of the accelerated beam with the [18O] water target material.
  • Owing to its short half-life (109 min), the isotope is used as soon as possible after production [2].


Bernard Ochieng, MSc, PMP®- Senior Medical Nuclear Physicist

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