scispace - formally typeset
Search or ask a question

Showing papers by "Charles L. Melcher published in 2004"


Journal ArticleDOI
TL;DR: In this paper, the luminescence and nuclear spectroscopic properties of the new cerium-doped rare-earth scintillator lutetium-yttrium oxyorthosilicate (Lu/sub 0.6/Y/sub 1.4/Si/ sub 0.5/:Ce, LYSO) were investigated and compared to those of both recent and older LSO crystals.
Abstract: The luminescence and nuclear spectroscopic properties of the new cerium-doped rare-earth scintillator lutetium-yttrium oxyorthosilicate (Lu/sub 0.6/Y/sub 1.4/Si/sub 0.5/: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.

186 citations


Journal ArticleDOI
TL;DR: Fifth-generation PET scanners should be a fully 3D system with no septa, a 25–30 cm axial field-of-view, and a spatial resolution approaching the limits set by the physics of positron emission.
Abstract: Since the ECAT 2, the first commercial positron emission tomograph developed by EG&G ORTEC, four generations of scanners can be identified. The first such scanners were based on sodium iodide (NaI(Tl)) scintillators, although as early as 1978 the transition to bismuth germanate (BGO) detectors had begun. By 1981, second-generation PET scanners with up to four rings of BGO detectors were available commercially. The BGO block detector appeared in 1985, initiating the third generation of PET scanners with the potential to increase the axial coverage in a cost-effective manner. As with the second generation, the third generation of PET scanners incorporated lead septa to collimate the annihilation photons within transverse planes, thereby reducing the acquisition of scattered and random coincidences and limiting detector dead time. The fourth generation of PET scanners offered up to 15 cm axial coverage and incorporated retractable septa that permitted both 2D and 3D acquisition within the same scanner. Therefore, fifth-generation scanner should be a fully 3D system with no septa, a 25–30 cm axial field-of-view, and a spatial resolution approaching the limits set by the physics of positron emission. Rather than using septa, limitation of randoms and scatter should be achieved directly at the detector by using a scintillator with high-light output, good energy resolution, and a fast scintillation decay time. The fast decay time will ensure low deadtime. The recent development of lutetium oxyorthosilicate (LSO), a scintillator with the required properties, suggests that a fifth generation of positron emission tomographs can now be attained.

26 citations


Proceedings ArticleDOI
16 Oct 2004
TL;DR: In this article, the results from experiments performed on Lu/sub 2/SiO/sub 5/Ce (LSO:Ce) samples were coupled to an XP2020Q photomultiplier and to large area avalanche photodiodes and measured as a function of gamma-ray energy.
Abstract: This work presents the results from experiments performed on Lu/sub 2/SiO/sub 5/:Ce (LSO:Ce). It looks for potential correlations of light yield non-proportionality and other scintillation properties including intrinsic energy resolution with thermoluminescence properties. Samples were chosen from various crystal batches that were known to have significantly different properties. Single crystal LSO:Ce samples were coupled to an XP2020Q photomultiplier and to large area avalanche photodiodes and measured as a function of gamma-ray energy between 14.7 and 1770 keV at room temperature and also near liquid nitrogen temperature. In order to explain the experimental results obtained from spectrometric methods, the properties of the samples were further studied using thermoluminescence techniques within the temperature range from 250 to 600 K. The relationships between data obtained from these two types of experiments are reported.

3 citations