Flat panel X-ray imagers using amorphous silicon active matrix addressing have been introduced to the medical imaging market at sizes up to 40×40 cm and with up to 10 million pixels. Some new technology developments, which can further increase the performance of these devices, are described. High atomic number polycrystalline X-ray photoconductors can operate near the theoretical sensitivity and at reasonably low bias voltages. The higher sensitivity obtained in HgI2 allows single-photon detection, which opens up new imaging opportunities. Another approach to improve sensitivity is to integrate an amplifier at the pixel level, which requires laser-recrystallised polysilicon transistors. A pixel-level source follower amplifier is shown to have enough gain to overcome other noise sources. A three-dimensional device structure is needed to accommodate the pixel electronics, and so the sensor is deposited on top of the electronics, separated by a thick passivation layer. Future possible detector technologies based on printing and organic semiconductors are discussed.
Inspec keywords: X-ray imaging; photoconducting materials; mercury compounds; X-ray detection; biomedical imaging; semiconductor materials; silicon; thin film transistors
Other keywords:
Subjects: Image sensors; X-ray, gamma-ray instruments and techniques; Patient diagnostic methods and instrumentation; X-ray and gamma-ray equipment; Photoconduction and photovoltaic effects; photodielectric effects; X-ray techniques: radiography and computed tomography (biomedical imaging/measurement); Photoconducting materials and properties; X-rays and particle beams (medical uses)
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