Positron emission tomography (PET) is one of the most powerful non-invasive diagnostic tools for tracing organ functioning. Quality control of the short-lived radiopharmaceuticals is challenging, not least because of the tough time limits, the radiation issue and the near nanomole radiotracer quantities.

This article presents a likewise rugged and versatile multichannel radio IC system that controls the production of the radionuclide [ ¹⁸ F]fluoride (precursor) and the two radiotracers synthesized from it, [ ¹⁸ F]fluorodeoxyglucose and [ ¹⁸ F]fluorocholine, in accordance with pharmacopoeial regulations.

Principles of Positron Emission Tomography (PET)

Radionuclides are unstable isotopes that have an excess of either neutrons or protons and, therefore, radioactively decay, resulting in the emission of gamma rays or subatomic particles. In proton-rich nuclides, a proton changes to a neutron, whereby a positron (antiparticle of the electron or an electron with a positive charge, also called B⁺ particle) is emitted together with a neutrino (ν) according to proton (p) → neutron (n) + positron (B⁺) + neutrino (ν).

Figure 1: Principle of positron emission tomography.

m_e ⁺ + m_e ^– → 2γ

Sophisticated scanners (detector) can detect such pairs of photons by coincidence detection. From the data collected, three-dimensional images of tissue structures are then calculated. The most commonly used short-lived, cyclotron-produced radionuclides in radiopharmacy are ¹¹C, ¹³N, ¹⁵O and ¹⁸F. Their respective half-lives are 20.38, 9.96, 2.03 and 109.7 min.