Light emission efficiency and imaging performance of Gd 2 O 2 S : Eu powder scintillator under x-ray radiography conditions

• Published in: Medical physics (Lancaster) Vol. 37; no. 7; pp. 3694 - 3703
• Main Authors: Michail, C. M., Fountos, G. P., Liaparinos, P. F., Kalyvas, N. E., Valais, I., Kandarakis, I. S., Panayiotakis, G. S.
• Format: Journal Article
• Language: English
• Published: American Association of Physicists in Medicine 01-07-2010
• Subjects: imaging performance; light emission efficiency; phosphor screens; radiation detectors; x-ray radiography; radiation detectors; x-ray radiography; phosphor screens; light emission efficiency; imaging performance
• ISSN: 0094-2405; 2473-4209
• DOI: 10.1118/1.3451113

Purpose:
To evaluate
Gd
2
O
2
S
:
Eu
powder phosphor as a radiographic image receptor and to compare it to phosphors often used in radiography.
Gd
2
O
2
S
:
Eu
is nonhygroscopic, emitting red light with decay time close to that of
Gd
2
O
2
S
:
Tb
.
Methods:
The light intensity emitted per unit of x-ray exposure rate (absolute luminescence efficiency) was measured for laboratory prepared screens with coating thicknesses of 33.1, 46.4, 63.1, 78.3, and
139.8

mg
/
cm
2
and tube voltages ranging from 50 to 140 kVp. Parameters related to image quality such as the modulation transfer function (MTF) and the detective quantum efficiency (DQE) were also experimentally examined. In addition, a previously validated Monte Carlo code was used to estimate intrinsic x-ray absorption and optical properties, as well as the MTF and the Swank factor
(
I
)
of the
Gd
2
O
2
S
:
Eu
scintillators.
Results:
Gd
2
O
2
S
:
Eu
light intensity was found higher than that of single CsI:Tl crystal for tube voltages up to 100 kVp. The MTF and the DQE were found to be comparable with those of
Gd
2
O
2
S
:
Tb
and CsI:Tl screens. MTF estimated by the Monte Carlo code was found very close to the experimental MTF values.
Gd
2
O
2
S
:
Eu
showed peak emission in the wavelength range 620–630 nm. Its emission spectrum was excellently matched to various optical detectors (photodiodes, photocathodes, CCDs, and CMOS) employed in flat panel detectors.
Conclusions:
Gd
2
O
2
S
:
Eu
is an efficient phosphor potentially well suited to radiography and especially to some digital detectors sensitive to red light.