Production of radiometals in liquid targets

Sergio J C Do Carmo,Francisco Alves,Peter J H Scott

doi:10.1186/s41181-019-0088-x

Abstract

Over the last several years, the use of radiometals has gained increasing relevance in supporting the continuous development of new, complementary and more specific biological targeting agents. Radiopharmaceuticals labelled with radiometals from elements such as Tc, Zr, Y, Ga and Cu received increasing attention as they find application in both diagnostic SPECT and PET imaging techniques and radiotherapeutic purposes. Such interest stems from the wide variety of radionuclides available with distinct and complementary nuclear decay characteristics to choose from with unequalled specificity, but can also be explained by growing demand in targeted radionuclide therapy. As a result, as routine supply of these radiometals becomes mandatory, studies describing their production processes have expanded rapidly. Although most radiometals are traditionally provided by the irradiation of solid targets in specialized cyclotrons, recently developed techniques for producing radiometals through the irradiation of liquid targets have received growing attention due to compatibility with commonly available small medical cyclotrons, promising characteristics and encouraging results. Irradiating liquid targets to produce radiometals appears as a fast, reliable, convenient and cost-efficient alternative to the conventional solid target techniques, characterized by complex and time-consuming pre- and post-irradiation target handling. Production of radiometals in liquid targets incorporated to complete manufacturing processes for daily routine is already recognized as a viable alternative and complementary supply methodology to existing solid target based infrastructures to satisfy growing clinical demands. For instance, several sites already use the approach to produce 68Ga-radiopharmaceuticals for clinical use. This review article covers the production of common radiometals with clinical potential through the irradiation liquid targets. A comparison with the traditional solid target irradiation methods is presented when relevant.

Highlights

Over the last several years, interest in biomedically useful molecular probes labelled with radionuclides other than common positron emitters like 11C, 13N, 15O and 18F has increased significantly (Reichert et al 1999; McQuade et al 2003)
The development of new tracers based on common radionuclides such as 11C and 18F will continue to play a significant role in future developments in Positron Emission Tomography (PET) radiochemistry, there is a growing demand and great potential for developing more specific targeted agents for which these more traditional position emitters are inadequate (McQuade et al 2003; Nedrow et al 2011)
As other radionuclides are required to enlarge the spectrum of biological processes that can be studied (Pagani et al 1997), radiolabelling with nonconventional radionuclides has become mandatory to support and answer the continuous development of novel molecular probes for Single Photon Emission Computed Tomography (SPECT) and PET diagnostic imaging techniques and for radiotherapeutic applications (Cutler et al 2013)

Summary

Introduction

Over the last several years, interest in biomedically useful molecular probes labelled with radionuclides other than common positron emitters like 11C, 13N, 15O and 18F has increased significantly (Reichert et al 1999; McQuade et al 2003). Despite such success, even more widespread use of 68Ga has been limited because of the relatively low activity levels delivered by 68Ge/68Ga generators (≤3.7 GBq) and the associated long down-time between elutions (≤4 h); at least until a few years ago with the introduction of the cyclotron-production of 68Ga in liquid targets as explained later. As these latter routes are dated with respect to recent developments on the production of radiometals in liquid targets, such reviews describe mostly applications of the solid target technique

References energy of target nuclide Irradiation

Findings

Conclusion