A comparative investigation of Lu₂SiO₅:Ce and Gd₂O₂S:Eu powder scintillators for use in x-ray mammography detectors

Abstract

The dominant powder scintillator in most medical imaging modalities for decades has been Gd2O2S:Tb due to the very good intrinsic properties and overall efficiency. Apart from Gd2O2S:Tb, there are alternative powder phosphor scintillators such as Lu2SiO5:Ce and Gd2O2S:Eu that have been suggested for use in various medical imaging modalities. Gd2O2S:Eu emits red light and can be combined mainly with digital mammography detectors such as CCDs. Lu2SiO5:Ce emits blue light and can be combined with blue sensitivity films, photocathodes and some photodiodes. For the purposes of the present study, two scintillating screens, one from Lu2SiO5:Ce and the other from Gd2O2S:Eu powders, were prepared using the method of sedimentation. The screen coating thicknesses were 25.0 and 33.1 mg cm−2 respectively. The screens were investigated by evaluating the following parameters: the output signal, the modulation transfer function, the noise equivalent passband, the informational efficiency, the quantum detection efficiency and the zero-frequency detective quantum efficiency. Furthermore, the spectral compatibility of those materials with various optical detectors was determined. Results were compared to published data for the commercially employed ‘Kodak Min-R film-screen system’, based on a 31.7 mg cm−2 thick Gd2O2S:Tb phosphor. For Gd2O2S:Eu, MTF data were found comparable to those of Gd2O2S:Tb, while the MTF of Lu2SiO5:Ce was even higher resulting in better spatial resolution and image sharpness properties. On the other hand, Gd2O2S:Eu was found to exhibit higher output signal and zero-frequency detective quantum efficiency than Lu2SiO5:Ce.

Light emission efficiency and imaging performance of powder scintillator under x‐ray radiography conditions

“…The AE of CsI:Tl ͑corresponding to a single crystal͒ was measured in a previous study 44 under experimental conditions identical to those used for the screen measurements, i.e., using a light integration sphere which assures equal light collection efficiency for both cases. 30,45 The thickness of 1 mm assigned to this CsI:Tl crystal corresponds to an estimated coating thickness of 0.451 g / cm 2 . The estimated thickness was calculated by assuming a constant density of 4.51 g / cm 3 , which means a packing density of 100%.…”

“…The spectra of CsI:Tl and Gd 2 O 2 S : Tb were obtained from a previous study. 30 Table II shows data relevant to the spectral compatibility between the optical spectra emitted by Gd 2 O 2 S : Eu, CsI:Tl, and Gd 2 O 2 S : Tb screens and the sensitivity of various optical detectors used in general ͑conventional or digital͒ radiography, such as ͑a͒ Agfa Scopix LT 2B film, ͑b͒ CCD, ͑c͒ flat panel imagers of a-Si: H photodiodes, and ͑d͒ CMOS sensors. For wavelengths in the range from 400 to 675 nm, the spectral compatibility was assessed by evaluating the spectral matching factor.…”

X-ray imaging resolution of phosphor screens prepared with different grains size and shape of granular Lu2O3:Eu

“…In addition the Na 2 SiO 3 fill the voids between the grains. Subsequently, due to higher refractive index, compared with it of air, leads the emitting photons to refract with lower angle when they go through from one material to another (refractive index of Lu 2 O 3 =1.935, refractive index of Na 2 SiO 3 = 1.53) [22]. The sedimentation was achieved by using a mixture consisting of 1000 ml of deionized water, 20 ml of Na 2 SiO 3 , and the appropriate amount of phosphor powder in a glass tube of 110 cm height.…”

Electrospinning fabrication and luminescence properties of Lu2O2S:Eu3+fibers

“…Lu2O2S has been widely investigated as the host lattice material for three-dimensional plasma display panels, field emission displays, light-emitting diodes and other related applications due to its favorable chemical durability, thermal stability, outstanding optical, electronic properties and ability to be easily doped with lanthanide ions. [14][15][16][17] As is well known that, Eu 3+ ions are expected to possess a superior red color, and are considered as one of the most frequently useful red emitters in rare-earth ions doped materials due to the 5 D0-7 FJ (J = 1, 2, 3, 4) characteristic emissions in the orange-red region. [18][19][20][21] So, Eu 3+doped Lu2O2S has considered as one of the important red-emitting fluorescent materials.…”