Detective quantum efficiency of a direct-detection active matrix flat panel imager at megavoltage energies

• Published in: Medical physics (Lancaster) 2001-07, Vol.28 (7), p.1364-1372
• Main Authors: Lachaine, M., Fourkal, E., Fallone, B. G.
• Format: Article
• Language: English
• Subjects: AMFPI; amorphous selenium; amorphous semiconductors; biomedical equipment; cascade analysis; Copper; diagnostic radiography; Display and recording equipment, oscilloscopes, TV cameras, etc; DQE; Electrons; elemental semiconductors; Energy efficiency; Energy use; flat panel displays; Image Interpretation, Computer-Assisted - instrumentation; Image Interpretation, Computer-Assisted - methods; Image sensors; Medical imaging; Models, Theoretical; Modulation transfer functions; Monte Carlo Method; Non‐ionizing radiation equipment and techniques; photoconducting materials; Photons; Physicists; portal imaging; Quantum measurement theory; Quantum noise; Quantum Theory; Selenium; semiconductor counters; Solid‐state detectors; X‐ and γ‐ray sources, mirrors, gratings, and detectors; X‐ray detection; X‐ray imaging
• ISSN: 0094-2405; 2473-4209
• DOI: 10.1118/1.1380213

The use of an amorphous selenium (a-Se) based direct-detection active matrix flat-panel imager (AMFPI) is studied for megavoltage imaging. The detector consists of a 1.2 mm copper front plate and 200 μm a-Se layer, and has a 85 μm pixel pitch. The Modulation Transfer Function (MTF), Noise Power Spectrum (NPS), and Detective Quantum Efficiency (DQE) are measured for 6 and 15 MV photon beams. A theoretical expression for the DQE is derived using a recently developed formalism for nonelementary cascade stages. A comparison of theory with experiment is good for the 6 and 15 MV beams. The model is used to explore the DQE for more typical pixel sizes. The results indicate that with proper modifications, such as a larger a-Se thickness, a direct flat-panel AMFPI is a very promising detector for megavoltage imaging.