Sodium Doped Cesium Iodide Research Articles

Effect of Ba co-doping on the X-ray induced afterglow of CsI(Na) crystal

Sodium-doped cesium iodide (CsI(Na)) is one of the highly effective scintillators that has been widely studied and used for several decades due to good performance. In this work, the effect of Ba co-doping on the afterglow in CsI(Na) crystal was investigated to evaluate its feasibility for applications in Computed Tomography (CT) imaging and radiation detection. We used a two-zone Bridgman furnace to grow the CsI(Na) single crystals co-doped with various concentrations of Ba. The single-doped and Ba co-doped CsI(Na) crystals demonstrate the emission at around 400 nm associated with Na-related luminescence. The scintillation performance of the grown single crystal was studied by irradiating the samples under a 137Cs gamma source. The single-doped and Ba co-doped CsI(Na) crystals exhibit a scintillation light yield ranging from 33,000 to 44,000 ph/MeV. The reduction of afterglow observed in Ba co-doped CsI(Na) crystals is associated with electron scavenging from the traps. To summarize, the Ba co-doped CsI(Na) crystal is a promising candidate for X-ray and CT imaging.

Performance assessment of the ALBIRA II pre-clinical SPECT S102 system for 99mTc imaging.

The performance characteristics of the SPECT sub-system S102 of the ALBIRA II PET/SPECT/CT are analyzed for the 80mm field of view (FOV) to evaluate the potential in-vivo imaging in rats, based on measurements of the system response for the commonly used Technetium-99m (99mTc) in small animal imaging. The ALBIRA II tri-modal µPET/SPECT/CT pre-clinical system (Bruker BioSpin, Ettlingen, Germany) was used. The SPECT modality is made up of two opposite gamma cameras (Version S102) with Sodium doped Cesium Iodide (CsI(Na)) single continuous crystal detectors coupled to position-sensitive photomultipliers (PSPMTs). Imaging was performed with the NEMA NU-4 image quality phantom (Data Spectrum Corporation, Durham, USA). Measurements were performed with a starting activity concentration of 4.76MBq/mL 99mTc. An energy window of 20% at 140keV was selected in this study. The system offers a 20mm, 40mm, 60mm and an 80mm field of view (FOV) and in this study the 80mm FOV was used for all the acquisitions. The data were reconstructed with an ordered subset expectation maximization (OSEM) algorithm. Sensitivity, spatial resolution, count rate linearity, convergence of the algorithm and the recovery coefficients (RC) were analyzed. All analyses were performed with PMOD and MATLAB software. The sensitivities measured at the center of the 80mm FOV with the point source were 23.1 ± 0.3 cps/MBq (single pinhole SPH) and 105.6 ± 5.5 cps/MBq (multi pinhole MPH). The values for the axial, tangential and radial full width at half maximum (FWHM) were 2.51, 2.54, and 2.55mm with SPH and 2.35, 2.44 and 2.32mm with MPH, respectively. The corresponding RC values for the 5mm, 4mm, 3mm and 2mm rods were 0.60 ± 0.28, 0.61 ± 0.24, 0.29 ± 0.11 and 0.20 ± 0.06 with SPH and 0.56 ± 0.20, 0.50 ± 0.18, 0.38 ± 0.09 and 0.23 ± 0.06 with MPH. To obtain quantitative imaging data, the image reconstructions should be performed with 12 iterations. The ALBIRA II preclinical SPECT sub-system S102 has a favorable sensitivity and spatial resolution for the 80mm FOV setting for both the SPH and MPH configurations and is a valuable tool for small animal imaging.

Fabrication of columnar CsI and CsI:Na scintillation films deposited by vacuum thermal evaporation at high deposition rates

Alkali halides have been increasingly used as scintillators and sensors in imaging and experimental particle physics applications. The luminescence efficiency of alkali halides is an important aspect of their application in imaging studies and related fields. Therefore, we investigate the optical, scintillation, and hygroscopic properties of cesium iodide (CsI) and sodium-doped CsI (CsI:Na) films grown via vacuum deposition at high deposition rates ∼90 nm/s. The film deposited on a protective layer (such as: SiO2, Al, or parylene-N) exhibits the desired properties of having a columnar structure, high moisture resistance, and high luminescence. Our process quickly yields high-quality CsI and CsI:Na films with thicknesses greater than 100 μm that exhibit the desired columnar structure and luminescence effect.

Detector Performance Characterization for High Sensitivity Single-Photon Imaging

We are developing detectors for an un-collimated scanner for very high sensitivity single-photon imaging. The scanner consists of two large, thin, closely spaced, pixelated scintillation detectors of either thallium-doped sodium iodide (NaI(Tl)), sodium-doped cesium iodide (CsI(Na)), or bismuth germanate (BGO). The scintillator arrays are interchangeable to optimize performance for a wide range of isotope energies and imaging subjects. For each scintillator, flood histograms were obtained utilizing test gamma sources: <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">109</sup> Cd, <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">241</sup> Am, <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">57</sup> Co, <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">133</sup> Ba, <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">137</sup> Cs, <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">22</sup> Na, and beta source <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">32</sup> Si. Using a 3 mm thick 21 ×41 NaI(Tl) pixelated array ( 2 mm ×2 mm pixels on a 2.2 mm pitch), read out by two adjacent Hamamatasu H8500 multi-channel photomultiplier tubes (MCPMTs), the energy resolution for <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">57</sup> Co was 12.2% over the center of the MCPMTs and 45.3% for pixels over the gap, with flood histogram peak-to-valley ratios > 6.1 for the center of the MCPMTs and > 4.2 for the gap between the two MCPMTs. The NaI(Tl) detector consistently produced peak-to-valley ratios of > 1.6 in the center of the MCPMTs for all radioisotopes studied. CsI(Na) and BGO detectors had flood histograms of similar quality to NaI(Tl) at intermediate to high-energies, allowing for optimal imaging across a wide energy range. The measured sensitivity for point sources placed 10 mm from the detector approached 35% for low-energy isotopes and all scintillator materials, which results in an expected system sensitivity (two opposing detectors) of ~ 70% for these isotopes. The 5 mm thick BGO arrays had the greatest efficiency for high-energy isotopes due to the increased stopping power of this material. The measured spatial resolution for <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">99m</sup> Tc for the CsI(Na) detector (1.6 mm pitch) was 7.5 mm FWHM at the aluminum entrance window (1.5 mm from scintillator face), decreasing to 15 mm at a distance of 5 mm from the scintillator face. The NaI(Tl) detector showed similar spatial resolution. This spatial resolution is sufficient for imaging well-localized radiotracer distributions in thin objects, and the very high sensitivity can be used for fast dynamic imaging, or imaging using very low injected doses.

A compact Compton camera using scintillators for the investigation of nuclear materials

Through its ability to reconstruct high energy (up to several MeV) radiation distributions without using thick mechanical collimation, the Compton camera has been used in many studies like astrophysics, industrial survey, homeland security and medical purposes. Whereas the performance of mechanical collimation decreases with radiation energy, the Compton camera is effective for detecting higher energy radiation. Even though scintillation detectors show high efficiencies, high timing resolution and usability without a cooling device, the bulky size of conventional photomultiplier tubes limits the scope of their applications to gamma-ray imaging. In order to overcome the limitation we constructed a Compton camera, which combined sodium doped cesium iodide (CsI(Na)) scintillators with position sensitive photomultiplier tubes (PSPMTs), which had multiple anodes connected to custom made circuits. The whole size of each detector is only about 5 cm×5 cm×6 cm, and therefore, it can be carried in hand for investigation of nuclear materials at seaports, airports or nuclear power plants. The intrinsic imaging efficiency and angular resolution of the compact Compton camera were 1.7293×10 −4 and 17.1° for a 356 keV source and 4.5254×10 −5 and 12.8° for a 662 keV source.