Epäsuoramuunnosdetektorit

Epäsuoramuunnosdetektorit, often translated as indirect conversion detectors, are a type of sensor used in digital radiography and other imaging modalities. Unlike direct conversion detectors, which convert X-ray photons directly into an electrical signal, indirect conversion detectors employ a two-step process. First, the incoming X-ray photons are absorbed by a scintillator material, such as cesium iodide (CsI) or gadolinium oxysulfide (Gd2O2S). This scintillator then emits visible light photons. These light photons are subsequently detected by a photodetector array, typically composed of amorphous silicon (a-Si) photodiodes or complementary metal-oxide-semiconductor (CMOS) active pixel sensors. The electrical charge generated by the photodiodes is then read out and processed to form the digital image.

The advantage of indirect conversion lies in the ability to use well-established and cost-effective photodetector technologies. The light conversion step can also offer some degree of signal amplification due to the nature of scintillation. However, this process can also lead to a loss of spatial resolution compared to direct conversion methods, as the emitted light photons can scatter before reaching the photodetector. This scattering, along with the inherent properties of the scintillator and photodetector, contributes to the overall modulation transfer function (MTF) of the detector system. Despite this, indirect conversion detectors are widely used due to their maturity, robustness, and acceptable performance for many diagnostic imaging applications.