Image sensors and optical devices
In indirect-conversion flat-panel detectors used for medical X-ray imaging, how are X-rays detected?
- AX-rays are focused with a lens onto silicon
- BA scintillator converts the X-rays into visible light, which is detected by photodiodes in the pixels
- CX-rays change the orientation of a magnetic material to record the image
Show answer and explanation
Answer: B. A scintillator converts the X-rays into visible light, which is detected by photodiodes in the pixels
Silicon photodiodes absorb hardly any of the penetrating X-rays, so in indirect conversion a scintillator such as cesium iodide converts the X-rays into visible light, which a large-area pixel array then detects. There is also a direct-conversion type that converts X-rays directly into charge using materials such as amorphous selenium.
- A. X-rays cannot be focused with ordinary lenses.
- B. Correct. A scintillator converts them to visible light for detection.
- C. It is not a magnetic recording method.