Direct Conversion Flat Panel Detector Utilizing TlBr Film for X-ray Imaging

The direct conversion Flat Panel Detectors (FPDs) have garnered extensive attention in X-ray imaging due to its enhanced image quality. In this study, a novel direct conversion FPD using Thallium Bromide (TlBr) film is developed and characterized. TlBr film, with a thickness of $25 \mu \mathrm{m}$ and sensitive area of $29.61 \times 39.48 \mathrm{~mm}^{2}$, was deposited using the evaporation method. A pixelated sensor matrix, featuring $168 \times 126$ pixels with a pixel size of $235 \times 235 \mu^{2}$, was developed using Low-Temperature Polysilicon Thin-Film Transistor (LTPS TFT) technology. Spatial resolution was evaluated using the slanted edge method with the TlBr layer biased at 1.00 V, capturing 100 frames for each experiment. The X-ray tube was operated at a voltage range of 25.0 kV to 35.0 kV with a constant current of 2.00 mA. The imaging performance of the TlBr FPD was assessed by imaging an anchovy object with a TlBr bias voltage of 0.75 V, capturing 1000 frames. The X-ray tube was operated at 23.0 kV with a current of 0.75 mA. The spatial resolution, determined from the Line Spread Function (LSF) profile, ranged from 222 to $280 \mu \mathrm{m}$ Full Width at Half Maximum (FWHM), constrained by the pixel size. In the X-ray imaging demonstration, the shape and structure of the anchovy were distinctly discerned. TlBr FPDs hold promising potential as room temperature X-ray imagers for both industrial and medical applications.