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X-ray imaging with amorphous selenium: X-ray to charge conversion gain and avalanche multiplication gain
Dylan C Hunt1, Sean S Kirby, J A Rowlands
1Sunnybrook & Women's College Health Science Centre, Imaging Research, Department of Medical Biophysics, University of Toronto, Toronto, Ontario M4N3M5, Canada.
Medical Physics
|December 5, 2002
Summary
Direct conversion fluoroscopy using amorphous selenium (a-Se) can achieve higher gain. Increasing electric field significantly boosts conversion gain and avalanche multiplication, overcoming detector noise for optimal imaging.
Area of Science:
- Medical Imaging
- Materials Science
Background:
- Fluoroscopy requires sensitive detectors for high-quality imaging at low doses.
- Current flat panel detectors exhibit noise limitations at fluoroscopic exposure rates.
- Direct and indirect imaging methods are hindered by noise, preventing optimal image quality.
Purpose of the Study:
- To investigate the gain of amorphous selenium (a-Se) direct conversion detectors.
- To determine if increasing the applied electric field can overcome detector noise limitations.
- To assess the potential for quantum noise-limited operation in fluoroscopy.
Main Methods:
- Investigated conversion gain and avalanche multiplication in a-Se.
- Varied the applied electric field from 10 to 100 V/microm.
- Analyzed performance at fluoroscopic exposure rates (0.1-10 microR/frame).
Main Results:
- Conversion gain increased by a factor of 4 with electric field enhancement (10 to 100 V/microm).
- Avalanche multiplication provided additional signal gain up to a factor of 25.
- Achieved sufficient signal increase to overcome flat panel detector noise.
Conclusions:
- Increased electric field in a-Se detectors significantly enhances conversion gain.
- Avalanche multiplication further boosts signal, enabling quantum noise-limited fluoroscopy.
- This approach overcomes limitations of current flat panel detectors for improved fluoroscopic imaging.