New breakthrough expands possibilities for PET imaging

Imagine being able to watch organs and tissues work in real time. That's the power of Positron Emission Tomography, or PET imaging, a technology that gives physicians and researchers a window into cellular processes.

In research recently published in Science, Virginia Tech chemist Wei Liu and his graduate student Chao Wang have found a new way to tag molecules to aid in PET scans - leading to improved processes, better imaging, and possibly more effective treatments.

PET imaging is a crucial resource in the medical field. It allows doctors and scientists to visualize how organs and tissues are functioning at a cellular level. It can help diagnose and monitor diseases such as cancer, evaluate brain disorders such as epilepsy, and even assess heart conditions.

PET imaging relies on radioactive atoms called radioisotopes. Chemists attach these to specific molecules based on the organ or tissue being studied. Inside the body, the molecule, called a PET tracer, travels to its target and lights up on the scan.

PET tracers rely on two main radioisotopes: carbon-11 and fluorine-18. Carbon-11 works well but decays in just 20 minutes, limiting its use. Fluorine-18 lasts two hours, making it more practical, but attaching it to key molecules has been a major challenge.

Liu and his team, working with collaborator Victor Pike of the National Institute of Mental Health, solved this problem by creating a way to add fluorine-18 to trifluoromethyl groups, a part of a molecule found in many Food and Drug Administration-approved drugs.

Trifluoromethyl groups are widely used in pharmaceutical design because they can improve drug stability, potency, and bioavailability, but they have been notoriously difficult to label with fluorine-18.

Using copper as a bridge, the team transferred fluorine-18 into these groups, making it possible to tag parts of molecules that were previously out of reach. The method works with complex drug-like structures and can even be adapted for carbon-11, giving researchers new flexibility in PET tracer design.

This breakthrough dramatically expands the range of molecules that can be imaged in the body. Many diseases and biological processes have no PET tracers today simply because the chemistry wasn't possible - until now.

With this new method for attaching fluorine-18 - and even carbon-11 - researchers may soon image previously inaccessible targets.

This can potentially revolutionize how the entire path and field develop tracer molecules for imaging important targets."

Wei Liu, chemist, Virginia Tech 

By unlocking new ways to label molecules, Liu's work could lead to earlier diagnoses and more targeted treatments for diseases that remain difficult to detect.