Light Decay Time/Gain Shift in a LaBr/sub 3/: Ce/LYSO:Ce Phoswich Detector

Green, M.V.; Seidel, Jürgen; Xi, Wenze; Choyke, Peter L.

doi:10.1109/nssmic.2006.354269

Cited by 3 publications

(2 citation statements)

References 5 publications

(5 reference statements)

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“…Green et al [7] looked at phoswich combinations of LaBr 3 :Ce and LYSO:Ce and found that the LaBr 3 :Ce crystal could not be identified due to the interaction between the two crystals. The LaBr 3 :Ce crystal used in their study was Saint Gobain, BrilLanCe 380 with 5% Ce with a fast rise time (< 1 ns) and a ~ 16 ns principal decay time.…”

Section: Introductionmentioning

confidence: 99%

Wavelength Shifting Phoswich Detectors for Superior Depth-of-Interaction Resolution

Melcher¹,

Eriksson²

2012

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BACKGROUNDIn order to simultaneously achieve both high spatial resolution and high sensitivity in small Positron Emission Tomography (PET) systems, scintillation detectors must be long in the radial direction as well as able to provide depth-ofinteraction (DOI) information. DOI information is typically provided by constructing detectors from two or more layers of scintillators that are identifiable due to their different decay times. This approach has worked well in tomographs such as the High Resolution Research Tomograph (HRRT, CTI PET Systems, Inc.) in which the emission and excitation bands of the scintillator layers do not overlap each other. However, many potentially important pairs of scintillator crystals exist in which the emission of one crystal is, in fact, absorbed and re-emitted by the second crystal, thus impacting the pulse shape discrimination process used to identify the scintillator layers. These potentially useful pairs of scintillators are unlikely to be implemented in phoswich detectors without a comprehensive understanding of the complex emission that results when one crystal's light is absorbed by the second crystal and then reemitted. Our objective has been to develop a fundamental understanding of the optical phenomena that occur in phoswich detectors and to exploit these phenomena to achieve improved spatial resolution in small high sensitivity PET scanners.Luminescence phenomena in phoswich detectors include both radioluminescence, i.e. light emission that is excited by gamma rays, and photoluminescence, i.e. the light emission that occurs when light from one crystal is absorbed and re-emitted by the second crystal. Since the shape of the light pulse that ultimately reaches the photosensor is affected by both of these phenomena, a clear understanding their characteristics is important for optimization of the pulse-shape-discrimination process. Our goal is use measured decay times, rise times, emission spectra, and excitation spectra as inputs for simulations of the convolved scintillation light pulse, and to benchmark the simulations to measurements of real phoswich configurations. The results then guide the selection of combinations of scintillators as well as to provide new techniques for extracting the maximum DOI information from thick detectors.We have assembled and characterized various sets of scintillators that are candidates for high resolution and high sensitivity PET. Some crystals have been grown in our own laboratory while others have been obtained commercially. We are focused on high density and high atomic number compounds that are doped with fast and efficient luminescent activators such as Ce and Pr. We have also investigated the use of wavelength shifters, bandpass filters, and wavelength shifting reflectors in order to optimize the identification of the crystal layers. The scintillators are characterized by means of both radioluminescence and photoluminescence techniques. The time-correlated single photon counting technique is used to measure rise times and decay tim...

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Section: Introductionmentioning

confidence: 99%

Wavelength Shifting Phoswich Detectors for Superior Depth-of-Interaction Resolution

Melcher¹,

Eriksson²

2012

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“…Green et al (7) looked at phoswich combinations between LaBr3 and LYSO and found that the LaBr3 crystal could not be identified due to the interaction between the two crystals. The LaBr3 crystal used in his study was St Gobain, BrilLanCe 380 with 5% Ce with a fast rise time (< 1ns) and a ~ 16 ns principal decay time.…”

mentioning

confidence: 99%

Design considerations of phoswich detectors for high resolution positron emission tomography

Eriksson

Melcher

Eriksson

et al. 2007

2007 IEEE Nuclear Science Symposium Conference Record

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A way to improve the spatial resolution in positron emission tomography (PET) is to determine the depth-ofinteraction (DOI) in the detector. A way to achieve this is to use the phoswich approach, a detector with two or more layers of different scintillators. The layer identification is done by using differences in scintillation decay time and pulse shape discrimination techniques. The advantages of the concept have been demonstrated in the HRRT high resolution PET system using a LSO/LYSO combination giving a high spatial resolution uniformity of around 2.5 mm within a larger part of the imaged volume. A phoswich combination that lately has received attention is LuAP/LSO or LuYAP/LSO. The suggestions come from the Crystal Clear Collaboration and there is a patent application for its use in PET. This particular combination of phoswich has, however, a complication since both LuAP and LuYAP emits in the excitation band of LSO, thus limiting the functionality. In the present paper we have looked into this and suggested different ways to overcome these drawbacks L. Eriksson, R. Grazioso and M. Aykac are with

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Design Considerations of Phoswich Detectors for High Resolution Positron Emission Tomography

Eriksson

Melcher

Eriksson

et al. 2009

IEEE Trans. Nucl. Sci.

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Light Decay Time/Gain Shift in a LaBr/sub 3/: Ce/LYSO:Ce Phoswich Detector

Cited by 3 publications

References 5 publications

Wavelength Shifting Phoswich Detectors for Superior Depth-of-Interaction Resolution

Wavelength Shifting Phoswich Detectors for Superior Depth-of-Interaction Resolution

Design considerations of phoswich detectors for high resolution positron emission tomography

Design Considerations of Phoswich Detectors for High Resolution Positron Emission Tomography

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