Performance assessment of CsI(Tl) screens on various substrates for X-ray imaging

TL;DR

This study evaluates how different substrates affect the optical and imaging performance of CsI(Tl) screens used in X-ray imaging, highlighting the influence of substrate choice on resolution, noise, and brightness.

Contribution

It systematically compares four substrates for CsI(Tl) screens, revealing how substrate optical properties impact imaging performance and enabling tailored screen design.

Findings

Graphite substrate yields higher resolution and better noise characteristics.

FOP substrate produces bright images with low noise but lower resolution.

Silica substrates result in low MTF but high NNPS, affecting image quality.

Abstract

Thallium-doped cesium iodide (CsI(Tl)) screens are widely used in X-ray imaging devices because of the columnar structure of CsI(Tl) layer, but few reports focus on the optical role of the substrate in the screen system. In this paper, four substrates including fused silica (SiO2), silver-film coated SiO2, graphite (C) and fiber optic plate (FOP) are used to fabricate CsI(Tl) screens by thermal evaporation. Their imaging performance is evaluated by relative light output (RLO), modulation transfer function (MTF), normalized noise power spectrum (NNPS) and noise equivalent quanta (NEQ). The results reveal that although CsI(Tl) film on graphite plate yields images with the lowest light output, it presents relatively higher spatial resolution and better signal-to-noise characteristics. However, films on SiO2 plate obtain low MTF but high NNPS curves, whether or not coated with silver film. Furthermore, scintillation screens on FOP have bright images with low NNPS and high NEQ, but have the lowest MTF. By controlling the substrate optical features, CsI(Tl) films can be tailed to suit a given application.