Low-afterglow CsI:Tl microcolumnar films for small animal high-speed microCT

Abstract

Dedicated high-speed microCT systems are being developed for noninvasive screening of small animals. Such systems require scintillators with high spatial resolution, high light yield, and minimal persistence to ensure ghost free imaging. Unfortunately, the afterglow associated with conventional CsI:Tl microcolumnar films used in current high-speed systems introduces image lag, leading to substantial artifacts in reconstructed images, especially when the detector is operated at several hundreds of frames per second. At RMD, we have discovered that the addition of a second dopant, Eu 2+ , to CsI:Tl crystals suppresses the afterglow by as much as a factor of 40 at 2 ms after a short excitation pulse of 20 ns, and by as much as a factor of 15 at 2 ms after a long excitation pulse of 100 ms. Our observations, supported by theoretical modeling, indicate that Eu 2+ ions introduce deep electron traps that alter the decay kinetics of the material, making it suitable for many high-speed imaging applications. Here we report on the fabrication and characterization of CsI:Tl,Eu microcolumnar films to determine if the remarkable afterglow properties of CsI:Tl,Eu crystals are preserved in the CsI:Tl,Eu microcolumnar films. Preliminary results indicate that the codoped microcolumnar films show a factor of 3.5 improvement in the afterglow compared to the standard CsI:Tl films.

Scintillation and Dosimetric Properties of Ce:CsCl Transparent Ceramics

“…The afterglow levels of the current samples were higher than those of common scintillators such as Tl:CsI crystal. (22) Figure 8 shows the TSL glow curves of Ce:CsCl transparent ceramic samples measured after X-ray irradiation (~100 mGy). All the samples showed a major glow peak at around 100 ℃.…”

Temperature Dependent Operation of PSAPD-Based Compact Gamma Camera for SPECT Imaging

“…Scintillation crystals with smaller segmentation sizes would in principle produce a more accurate measurement of the intrinsic PSAPD noise and spatial resolution; however, it is difficult to fabricate a scintillation crystal with smaller segmentation (< 400 μm) [24]. …”

High-speed detector for time-resolved diffraction studies

“…Besides, unlike the powdered Gd 2 O 2 S screen used by Matsuo [6], our detector is based on a 7 cm × 7 cm film of a high-resolution, low-afterglow, bright microcolumnar CsI:Tl,Sm scintillator coupled to a fiberoptic taper, resulting in the higher sensitivity needed for time-resolved experiments. Co-doped CsI:Tl,Sm is a newly developed scintillator from RMD that reduces the afterglow and hysteresis associated with conventional CsI:Tl by several orders of magnitude [8]–[10] without sacrificing its excellent scintillation properties, thereby making it a material well suited for high-speed, high-resolution imaging [11],[12]. The microcolumnar nature of the screen suppresses lateral light spread in the scintillator, resulting in a high spatial resolution, even when the scintillator is thick to increase absorption of the incident X-ray flux, offering the flexibility to tailor the scintillator thickness for a particular X-ray energy.…”

“…The microcolumnar nature of the screen suppresses lateral light spread in the scintillator, resulting in a high spatial resolution, even when the scintillator is thick to increase absorption of the incident X-ray flux, offering the flexibility to tailor the scintillator thickness for a particular X-ray energy. For example, using a 150 µm thick CsI:Tl,Sm film stopping over 99% of the 12 keV X-rays used in our experiments, we had earlier demonstrated over 16 lp/mm of spatial resolution [11],[12] and over 275 fps imaging of small-angle X-ray scattering at a synchrotron beamline [13]. In this paper, we have demonstrated the suitability of CsI:Tl,Sm for up to 2,000 fps imaging, which is also the frame rate of interest for our time-resolved scattering experiments.…”