Characterization of a Tl₂LaCl₅:Ce Crystal Coupled With a Silicon Photomultiplier for a Compact Single-Photon Emission Computed Tomography System

The novel Tl<sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub>LaCl<sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">5</sub>:Ce (TLC) crystal scintillator has a high density and effective Z number. Hence, a single-photon emission computed tomography (SPECT) detector equipped with the scintillator has excellent X-ray and γ-ray detection efficiency and a high light yield (LY). The feasibility of utilizing the TLC crystal coupled with a silicon photomultiplier (SiPM) was investigated for a compact SPECT detector. The TLC crystal (Ø 8 mm × 2 mm) coupled with a one-channel SiPM (6.07 × 6.07 mm<sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup>) was used. Electrical characteristics of the SiPM were used for optimizing the operating voltage and dynamic range. The γ-rays energy spectra of <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">241</sup>Am, and <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">152</sup>Eu were obtained. The SiPM outputs were digitized utilizing a data acquisition system. The breakdown voltage of the SiPM was measured to be 24.8 V. The operating voltage was fixed as 29.8 V by comparing energy resolutions for different operating voltages under 81 keV γ-ray excitation from a <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">133</sup>Ba radioactive source. The linearity of the SiPM was measured to be within 3.7% for up to 8,500 incident photons. Owing to the high LY of the TLC crystal and dynamic range of SiPM, the best energy resolution of the TLC crystal was achieved to be 8.7% full-width-half-maximum at 121.7 keV γ-ray at voltage of 29.8 V. The TLC crystal coupled with SiPM is expected to be utilized for development of compact SPECT detectors. It can replace conventional photomultiplier detectors and attain a good image quality, comparable to that of a solid-state detector in the SPECT system.