TFT/CCD/CMOS TEST QUESTIONS AND ANSWERS

them to electrical charges for storage and readout. Describe the 3 layers of a flat panel detector. - Answer- First layer - the x-ray converter Second layer - The TFT array Third layer - Glass substrate What is another name for the X-ray converter? - Answer- The absorber The choice of x-ray absorption material determines whether the detector is a ________or _______ conversion system? - Answer- Direct or Indirect Describe the Direct conversion system with TFT plates - Answer- 1 step process. X-ray photons are absorbed by the coating material and immediately converted directly into an electrical signal. What is the radiation-conversion material or photoconductor, typically made of with direct conversion systems? - Answer- Typically made of Amorphous selenium (a-Se). This is the material that absorbs and converts x-rays into electrons, which are stored in the TFT detectors. What absorbs x-rays and produces electrical charges? - Answer- A photoconductor More than ___ million pixels can be read and converted to a composite digital image in less than ___ second with direct TFT plates? - Answer- 1 million in 1 second Describe the Indirect conversion system with TFT plates - Answer- 2 step process. X-ray photons are converted to light, then the light photons are converted to an electrical signal. In which layer are the x-rays converted into light? - Answer- The phosphor or scintillation layer Is the scintillation layer structured or unstructured? - Answer- It can be either structured or unstructured What are the two types of phosphor structures? - Answer- Turbid (unstructured or random) and Needle/Columnar (structured) What are turbid phosphor composed of? - Answer- Gadolinium Oxysulfide (Gd2O2S)