Optimization of design parameters of a prototype CCD-based lens-coupled imaging system for the detection of beta particles in a microfluidic chip

Microfluidic chips are an emerging technology that facilitates the study of molecular processes in nano-liter levels in a finely controlled manner. A prototype imaging system capable of detecting and quantifying very small amounts of beta particles in a microfluidic chip, utilizing a scintillator, an optical lens, and a Charge Coupled Device (CCD), was developed and proof of concept was previously demonstrated [1]. In this study, we optimized the system design parameters, such as CCD binning and types of scintillators, and evaluated the system performance for spatial resolution and minimum detectable activity. Pixel binning of the CCD during readout process improved the signal-to-noise ratio with no spatial resolution degradation in beta particle imaging of
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F, up to a binning of 3x3 in our study, which was equivalent to 44 μm x 44 μm pixels in an object plane with a magnification of 0.5. The full width at half maximum (FWHM) of line sources with a finite width of 115 μm were measured to be 493 μm with a plastic scintillator and 289 μm with a CsI(Tl) scintillator. The minimum detectable activities were measured to be 360 pCi/mm
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with a plastic scintillator and 40 pCi/mm
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with a CsI(Tl) scintillator for a 5-min acquisition.