Entropy as a measure of the performance of phosphor materials used in medical imaging radiation detectors |
| |
Authors: | D Cavouras I Kandarakis T Maris GS Panayiotakis CD Nomicos |
| |
Institution: | (1) Department of Medical Instrumentation Technology, TEI of Athens, Ag. Spyridonos Street, Aigaleo. 12210 Athens, Greece, GR;(2) Department of Radiology, University Hospital, Medical School, University of Crete, Heraklion, Greece, GR;(3) Department of Medical Physics, Medical School, University of Patras, 26500 Patras, Greece, GR;(4) Department of Electronics, TEI of Athens, Ag. Spyridonos Street, Aigaleo, 12210 Athens, Greece, GR |
| |
Abstract: | In information theory, entropy expresses the information gain obtained after detection of a signal concerning the state of
a parameter of interest. In this study, entropy has been expressed in terms of physical quantities (emitted optical fluence
and MTF) related to the imaging performance of phosphor materials, which are employed in medical imaging radiation detectors.
Four phosphor materials, used in the form of laboratory-prepared fluorescent layers (screens), were compared on the basis
of their entropy performance. Measurements were performed using 30- and 80-kVp X-ray beams often employed in X-ray imaging.
Results showed that phosphor materials with high density and effective atomic number exhibit high entropy performance, especially
at the higher X-ray tube voltage of 80 kVp. Entropy values are also affected by the type of activator, which determines the
intrinsic X-ray-to-light conversion efficiency, and the spectrum of emitted light. The proximity of the incident X-ray quanta
energy to the energy of the K-shell threshold for photoelectric absorption is an additional important factor which increases
entropy. This effect was more apparent in the performance of yttrium-based phosphors at the lower voltage of 30 kVp.
Received: 7 January 2000 / Accepted: 28 March 2000 / Published online: 23 August 2000 |
| |
Keywords: | PACS: 78 65 42 80 |
本文献已被 SpringerLink 等数据库收录! |
|