X-ray detectors used in medicine have a glass core that makes them fragile, heavy, and unwieldy. The future is looking lighter for X-ray detectors thanks to researchers at Holst Centre in The Netherlands, imec in Belgium, and Philips who have been working on a medical quality detector that uses a plastic substrate.
The device provides dynamic, high-contrast images at 25 frames per second and a 200 pixels per inch resolution. The plate itself is 160 x 120 pixels in size, but could be made bigger for clinical applications.
Some details on the development of the new detector, according to the announcement:
In 2012, the team demonstrated the world’s first complete X-ray detector produced on a thin plastic substrate. An indirect flat panel detector (FPD), it combined a standard scintillator with a novel organic photodiode layer and organic thin-film transistor (TFT) backplane. By using solution-processed organic semiconductor rather than the usual amorphous silicon, the team reduced process temperatures to be compatible with plastic film substrates. They also eliminated a number of costly lithography steps, opening the door to lower production costs.
Now, the same team has delivered a major breakthrough in device performance. It has reduced the photodiode leakage current (the output from the photodiodes at zero light) by a factor of 10,000, down to 10-7 mA/cm2, bringing it well within the requirements for medical detectors. This improves the signal-to-noise ratio, and hence image quality at low radiation dose. At the same time, oxide transistors are used instead of organic transistors. The charge carrier mobility in the metal-oxide TFTs is 10-50 times higher than with amorphous silicon and organic transistors, enabling faster image acquisition.