SHARP-AMFPI DETECTOR RESEARCH

 

In radiography, the ultimate goal is to produce high quality images for diagnosis while minimizing patient exposure to harmful ionizing radiation. AMFPIs (Active Matrix Flat Panel Imagers) are x-ray detectors that have high image quality and can produce real time readouts, however their performance struggles at low radiation dose. This is because electronic noise overcomes the desired signal in amplitude. In order to overcome this issue, Stony Brook professor Dr. Wei Zhao, developed the Scintillating High-gain Avalanche Rushing Photoconductor-AMFPI (SHARP-AMPFI). This device introduces a scintillator to convert x-rays into optical photons. These optical photons then interact with electron hole pairs within a layer of amorphous selenium (a-Se) in an electric field and causes them to separate. The freed charges then continue to collide with other electron hole pairs to create others, increasing exponentially. The increased amount of charges present amplifies the signal and is used to create the image at the detector. This provides nearly noiseless signal gain to overcome electronic noise. The typical device is presented in the image above.

While the initial prototype is a very promising device and has potential application in clinical devices, it has a few issues that need to be addressed before it is ready for actual clinical use. Namely, a suitable hole blocking layer to prevent undesirable electrical effects and increasing the detector’s sensitivity to green light. My current projects are investigating potential solutions to these shortcomings.