Two-step radiosynthesis of [18F]FE-β-CIT and [18F]PR04.MZ

Open-source flow setup for rapid and efficient [18 F]fluoride drying for automation of PET tracer syntheses

One of the key strategies for radiochemical research facilities is the automation of synthesis processes. Unnecessary manual operations increase the radiation exposure of personnel, while simultaneously threatening the reliability of syntheses. We have previously reported an affordable open-source system comprising 3D-printed continuous flow reactors, a custom syringe pump, and a pressure regulator that can be used to perform radiofluorinations. In this paper, we address additional essential processes that are needed for radiotracer development and synthesis, with the aim of making laboratory work safer and research more efficient. We have designed and evaluated a fully automated system for rapidly and effectively processing and drying aqueous [18 F]fluoride that can be directly connected to the cyclotron. This process relies on triflyl fluoride gas generation and allows nucleophilic [18 F]fluoride to be prepared safely in a hotcell within 10 min and an activity recovery of 91.7 ± 1.6% (n = 5). Owing to the need for convenient radiofluorinated prosthetic ligands, we have adapted our continuous flow system to produce [18 F]fluoroethyl tosylate (FEOTs) and [18 F]fluoroethyl triflate (FEOTf), prosthetic groups that are widely used for late-stage fluoroethylation of PET tracers. The processes as well as the radiolabeling of different groups are compared and comprehensively discussed. Having a method providing [18 F]fluoroethyl tosylate (FEOTs) as well as [18 F]fluoroethyl triflate (FEOTf) quickly and highly efficiently is beneficial for radiochemical research.

Fluorine-18 labelled building blocks for PET tracer synthesis

This review presents a comprehensive overview of the synthesis and application of fluorine-18 labelled building blocks since 2010.

2-[18F]Fluoroethyl tosylate – a versatile tool for building18F-based radiotracers for positron emission tomography

The review highlights the role of 2-[¹⁸F]fluoroethyltosylate ([¹⁸F]FETs) in PET radiotracer design since it is a preferred labeling reagent according to its high reactivity to phenolic, amine, thiophenolic and carboxylic functions.

Positron emission tomography and pharmacokinetics of 2-[18F]-fluoroethyl choline for metabolic studies in breast cancer xenografts

BACKGROUND

Breast carcinomas (BC) can have abnormal choline (Cho) metabolism. Earlier studies indicated that Cho uptake can differ between different subtypes of BC. The purpose of this study was to investigate uptake of 2-[(18)F]-fluoroethyl-choline ([(18)F]FECh) in three different patient-derived breast cancer xenografts (BCXs) using dynamic positron emission tomography (dPET).

MATERIAL AND METHODS

Nine athymic nude mice bearing bilateral MAS98.12 (basal-like), HBCx34 or MAS98.06 (both luminal B) BCXs were subjected to a 90-minute dPET scan following a bolus injection of 10 MBq of [(18)F]FECh. A Patlak Plot analysis and a well-established two-tissue compartment model were fitted to the uptake curves of the whole tumors, providing estimates of transfer rates between the vascular, non-metabolized and metabolized compartments. Patlak slope KP and intercept V, the rate constants k₁, k₂, k₃, the intravascular fraction vb and MR[(18)F]FECh were estimated. Additionally, analyses of terminal blood samples and tumor cell suspension incubated with [(18)F]FECh were performed.

RESULTS

[(18)F]FECh uptake in all BCXs was similar to surrounding normal tissue, thus creating no image contrast. The average liver uptake was 10 times higher than the tumor uptake. The uptake in MAS98.12 was higher than in the other two BCXs during the whole course of the acquisition, and was significantly higher than in HBCx34 at 10-30 minutes after injection. No significant differences were found for k1, MR[(18)F]FECh and intravascular fraction vb. Patlak slope KP, k₂ and k₃ were significantly lower for the MAS98.12 xenograft, in line with in vitro results. KP was correlated with both MR[(18)F]FECh and k₃.

CONCLUSIONS

dPET demonstrated that different subtypes of breast cancer have different uptake of [(18)F]FECh. Differences in rate constants and KP were in line with in vitro uptake in cell suspensions and earlier spectroscopy and gene expression analysis.

18F-labelled intermediates for radiosynthesis by modular build-up reactions: newer developments

This brief review gives an overview of newer developments in (18)F-chemistry with the focus on small (18)F-labelled molecules as intermediates for modular build-up syntheses. The short half-life (<2 h) of the radionuclide requires efficient syntheses of these intermediates considering that multistep syntheses are often time consuming and characterized by a loss of yield in each reaction step. Recent examples of improved synthesis of (18)F-labelled intermediates show new possibilities for no-carrier-added ring-fluorinated arenes, novel intermediates for tri[(18)F]fluoromethylation reactions, and (18)F-fluorovinylation methods.