Microfluidics is an emerging technology that is facilitating the study of molecular processes in nano-liter levels in a finely controlled manner. One of the research interests at UCLA is the development of a versatile, modular and automated microfluidic platform capable of synthesizing ¹⁸F-labeled small molecules and biomolecules for PET imaging on demand. Although there is active research, one of the obstacles hindering the development of microfluidic chips is the lack of dedicated imaging systems.

A prototype imaging system capable of detecting and quantifying the amount of beta particles in a microfluidic chip has been developed and proof of concept was demonstrated. The imaging system consists of a charge coupled device (CCD) optically coupled to a lens. The study focused on developing a system using indirect detection methods, which converts the energy of beta particles into visible light photons and then measures these photons with a CCD camera. In order to convert the beta particle energy into visible light photons, two approaches were investigated: (1) scintillation approach: conversion of beta particle energy into scintillation light using a scintillator and (2) Cerenkov radiation approach: conversion of beta particle energy into visible light from Cerenkov radiation. The system performance was investigated using each light-conversion method by measuring spatial resolution, calibration curve, and minimum detectable activity.

Preliminary experiments were conducted using Cerenkov radiation imaging to investigate radiochemical synthesis in a microfluidic chip with the special aim of uncovering the source of failures during the [¹⁸F]fluoride solution drying process. In a short time, the Cerenkov radiation imaging has helped pinpoint several sources of chip failure.

In conclusion, the developed beta imaging system in conjunction with the investigated indirect-detection methods provided a reliable quantitative imaging and measurement tool for microfluidic applications utilizing beta particles. Therefore, the technology will be of great interest to developers of novel microfluidic chips as well as users of these microfluidic devices.