Properties of LYSO and recent LSO scintillators for phoswich PET detectors

Dept. of Nucl. Med. & Radiobiol., Univ. de Sherbrooke, Que., Canada
IEEE Transactions on Nuclear Science (Impact Factor: 1.46). 07/2004; DOI: 10.1109/TNS.2004.829781
Source: IEEE Xplore

ABSTRACT The luminescence and nuclear spectroscopic properties of the new cerium-doped rare-earth scintillator lutetium-yttrium oxyorthosilicate (Lu0.6Y1.4Si0.5:Ce, LYSO) were investigated and compared to those of both recent and older LSO crystals. UV-excited luminescent spectra outline important similarities between LYSO and LSO scintillators. The two distinct Ce1 and Ce2 luminescence mechanisms previously identified in LSO are also present in LYSO scintillators. The energy and timing resolutions were measured using avalanche photodiode (APD) and photomultiplier tube (PMT) readouts. The dependence of energy resolution on gamma-ray energy was also assessed to unveil the crystal intrinsic resolution parameters. In spite of significant progress in light output and luminescence properties, the energy resolution of these scintillators appears to still suffer from an excess variance in the number of scintillation photons. Pulse-shape discrimination between LYSO and LSO scintillators has been successfully achieved in phoswich assemblies, confirming LYSO, with a sufficient amount of yttrium to modify the decay time, to be a potential candidate for depth-of-interaction determination in multicrystal PET detectors.

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Available from: Catherine Michelle Pepin, Mar 11, 2014
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    • "atomic number, density, light yield), the light propagation inside crystals impacts a number of performance parameters including energy resolution and time resolution (Cherry et al 1995, Huber et al 1999, Moses and Derenzo 1999, Moses and Ullisch 2006, Peng and Levin 2010). In particular, surface treatment and reflectors affect the processes of both reflection and refraction of light photons at internal interfaces, and consequently impact the efficiency of light collection (Barton et al 1999, Saoudi et al Q2 2000, Pepin et al 2004, Heinrichs et al 2002, Dhanasopon et al 2005, Vandenbroucke and Levin 2008, Janecek and Moses 2010). Moreover, different light transport processes also result in different temporal responses and time resolution, which is critical for a time of-flight (ToF) PET when using fast scintillation crystal materials and novel photodetector technologies (Moses and Ullisch 2006, Spanoudaki and Levin 2011). "
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    ABSTRACT: Scintillation crystal design is a critical component in positron emission tomography system development, which impacts a number of performance parameters including energy resolution, time resolution and spatial resolution. Our work aims to develop a generalized simulation tool to model the light transport inside scintillation crystals with good accuracy, taking into account surface treatments, reflectors, temporal dependence of scintillation decay, and comprehensive experimental validations. The simulation has been validated against both direct analytical calculation and experimental measurements. In this work, the studies were performed for a lutetium-yttrium oxyorthosilicate crystal of 3×3×20 mm3 dimension coupled to a Hamamatsu silicon photomultiplier, with respect to light output, rise-time slope, energy resolution and time resolution. Four crystal surface treatment and reflector configurations were investigated: GroundMetal, GroundPaint, PolishMetal and PolishPaint. The experiments were performed to validate the Monte Carlo simulation results. The results indicate that the best time resolution (0.96±0.05 ns) and good energy resolution (10.6±0.4%) could be produced by using a polished surface with specular reflector, while the configuration of a polished surface with diffusive reflector produces the best energy resolution (10.2±0.9%). The results indicate that a polished surface with diffusive reflector achieves the best energy resolution (10.2±0.9%) for 511 keV high energy photons, and a polished surface with specular reflector achieves the best time resolution (0.96±0.05 ns) measured against a Hamamatsu fast photomultiplier tube. The ground surface treatment is not recommended for its inferior performance in terms of energy and time resolution. Possible explanations and future improvements to be made to the developed simulation tool are discussed.
    Physics in Medicine and Biology 03/2013; 58(7):2143-2161. DOI:10.1088/0031-9155/58/7/2143 · 2.92 Impact Factor
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    • "The better in proportionality of LYSO:Ce is one of the important reasons behind its energy resolution. It appears so far, that all silicate scintillators (LSO, YSO, GSO or LGSO) exhibit large non-proportionality in the light yield [7] [11] [12] [13]. The non-proportionality characteristics of the studied crystals should be reflected in their intrinsic resolutions, as it is known that the non-proportionality in the light yield is a fundamental limitation to the intrinsic energy resolution [14] [15]. "
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    ABSTRACT: The scintillation response of the new Ce-doped lutetium-yttrium oxyorthosilicate (Lu1.95Y0.05SiO5:Ce, LYSO:Ce) crystal was investigated and compared to that of Ce-doped lutetium oxyorthosilicate (Lu2SiO5:Ce, LSO:Ce) crystal. The light yield and energy resolution were measured using photomultiplier tube (XP5200B PMT) readout. For 662 keV γ-rays (137Cs source), the LYSO:Ce showed the light yield of 39,900 ph/MeV, which is higher than that of 35,900 ph/MeV obtained for LSO:Ce:Ce. The energy resolution of 8.2% obtained with LYSO:Ce is better than that of 10.6% obtained with LSO:Ce. The non-proportionality of the light yield and energy resolution versus γ-ray energy were measured and the intrinsic resolution of the crystals was calculated. Over the energy range from 16.6 keV to 1274.5 keV, the non-proportionality of about 35 % for LYSO:Ce is better than that of about 42% for LSO:Ce. The photofraction was determined for both crystals and compared with the cross-sections ratio calculated using WinXCOM program.
    Procedia Engineering 11/2011; 32:765-771. DOI:10.1016/j.proeng.2012.02.010
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    • "shows the typical UV-excited luminescence spectra of one LYSO sample [10] [19] [20]. The other sample has similar result. "
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    ABSTRACT: Cerium doped lutetium oxyorthosilicate scintillators, such as LYSO, which possess high stopping power, high light output and fast decay time, are promising candidates for use in positron emission tomography. In this paper, the luminescence and nuclear spectroscopic properties of two LYSO samples, used in the NN-PET detectors, are studied. UV-excited emission spectra show that maximum emission spectral values are within the range of 400-425 nm, which is well compatible with spectral response of PMT H7546B. The decay time, energy resolution, light output and energy spectra related to coincidence time window were investigated. The decay times of the two LYSO samples are 34.16plusmn1.43ns, 34.26plusmn1.95ns, respectively. The energy resolution and the light output, relative to Nal(Tl), are 10.25%plusmn0.06%, 10.17%plusmn0.10% and 75.3plusmn5.7, 76.1plusmn5.8 respectively when detected with PMT XP2262B. The energy spectra change obviously with coincidence time window and coincidence energy resolution is 14% when obtained using coincidence detector based on LYSO and H7546B.
    Proceedings of the 2nd International Conference on BioMedical Engineering and Informatics, BMEI 2009, October 17-19, 2009, Tianjin, China; 01/2009
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