Design considerations of phoswich detectors for high resolution positron emission tomography

Eriksson, Lars; Melcher, Charles L.; Eriksson, M.; Grazioso, R.; Aykac, M.

doi:10.1109/nssmic.2007.4436682

Cited by 8 publications

(9 citation statements)

References 8 publications

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“…Phoswich designs typically use scintillators with a factor of two difference in decay constant (Eriksson et al 2009), which alone would cause a ~40% increase in timing uncertainty for the layer with the longer decay time, in addition to degradations caused by slowing the signal rise time and a reduction in light collection—both of which are an unavoidable consequence of the stacked crystal geometry. This work suggests that the best TOF-DOI capability is achieved when the change in DOI signal shape is small, preserving the fast non-DOI signal shape.…”

Section: Discussionmentioning

confidence: 99%

Characterization of stacked-crystal PET detector designs for measurement of both TOF and DOI

2015

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A PET detector with good timing resolution and two-level depth-of-interaction (DOI) discrimination can be constructed using a single-ended readout of scintillator stacks of Lanthanum Bromide (LaBr3), with various Cerium dopant concentrations, including pure Cerium Bromide (CeBr3). The stacked crystal geometry creates a unique signal shape for interactions occurring in each layer, which can be used to identify the DOI, while retaining the inherently good timing properties of LaBr3 and CeBr3. In this work, single pixel elements are used to optimize the choice of scintillator, coupling of layers, and type of photodetector, evaluating the performance using a fast, single-channel photomultiplier tube (PMT) and a single 4×4 mm2 silicon photomultiplier (SiPM). We also introduce a method to quantify and evaluate the DOI discrimination accuracy. From signal shape measurements using fast waveform sampling, we found that in addition to differences in signal rise times, between crystal layers, there were also differences in the signal fall times. A DOI accuracy of 98% was achieved using our classification method for a stacked crystal pair, consisting of a 15-mm long LaBr3(Ce:20%) crystal on top of a 15-mm long CeBr3 crystal, readout using a PMT. A DOI accuracy of 95% was measured with a stack of two, identical, 12-mm long, CeBr3 crystals. The DOI accuracy of this crystal pair was reduced to 91% when using a SiPM for readout. For the stack of two, 12-mm long, CeBr3 crystals, a coincidence timing resolution (average of timing results from the top and bottom layer) of 199 ps was measured using a PMT, and this was improved to 153 ps when using a SiPM. These results show that with stacked LaBr3/CeBr3 scintillators and fast waveform sampling nearly perfect DOI accuracy can be achieved with excellent timing resolution—timing resolution that is only minimally degraded compared to results from a single CeBr3 crystal of comparable length to the stacked crystals. The interface in the stacked crystal geometry itself plays a major role in creating the differences in signal shape and this can be used to construct stacked DOI detectors using the same scintillator type, thereby simplifying and broadening the application of this technique.

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Section: Discussionmentioning

confidence: 99%

Characterization of stacked-crystal PET detector designs for measurement of both TOF and DOI

2015

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“…Figure 4 shows the in-line transmittance of the bilayer structure ceramics. 36 Owing to the empty 4f level of Ce 4+ , the absorption of scintillation light from the Pr: LuAG layer has little contribution in the Ce 4+ ions enriched Ce:LuAG layer. The absorption bands deriving from Ce 3+ 4f-5d 1,2 and Pr 3+ 4f-5d 1 transitions are clear in the curves of the bilayer ceramics.…”

Section: Resultsmentioning

confidence: 99%

A kind of bilayer structure ceramic scintillators designed for phoswich detectors

Chen

Ding

et al. 2017

J Am Ceram Soc

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The phoswich detectors can determine the location of nuclear interactions with the matrix and it is an effective approach to improve the spatial resolution at the edge of the field of view in positron emission tomography. In this study, we proposed a kind of bilayer structure garnet ceramic scintillators for phoswich detectors. Bilayer Pr:LuAG/Ce:LuAG ceramic scintillations with different thickness ratio were fabricated through solid‐state reaction and vacuum sintering without further cutting or stacking process. The phase, microstructure, fluorescence, and scintillation properties were characterized and studied. The decay time of the Pr:LuAG layer was about 21.8 ns while that of the Ce:LuAG layer was 58.6 ns. Different 5d‐4f emission bands of 290‐450 and 475‐700 nm were observed in the Pr:LuAG layer and Ce:LuAG layer, respectively. These two features meet the basic requirements of phoswich detectors. Separation of interactions with γ‐ray in different layers has achieved in the pulse height spectra. These properties reveal that this kind of multilayer structure garnet ceramic scintillators have potential application value in the field of phoswich detectors.

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“…Among the various methods proposed to encode DOI, notable approaches include dual-ended readout of the scintillator (Yang et al , 2008), and the phoswich detector composed of several layers of scintillators with different decay times (Jung et al , 2007; Eriksson et al , 2009). Other designs include multi-layer scintillator arrays with offset crystals (Ito et al , 2010), arrangements with light sharing between crystal layers (Nishikido et al , 2010), and monolithic detectors (Maas et al , 2009; Miyaoka et al , 2010).…”

Section: Introductionmentioning

confidence: 99%

Predicting the timing properties of phosphor-coated scintillators using Monte Carlo light transport simulation

et al. 2014

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Current developments in positron emission tomography (PET) focus on improving timing performance for scanners with time-of-flight (TOF) capability, and incorporating depth-of-interaction (DOI) information. Recent studies have shown that incorporating DOI correction in TOF detectors can improve timing resolution, and that DOI also becomes more important in long axial field-of-view scanners. We have previously reported the development of DOI-encoding detectors using phosphor-coated scintillation crystals; here we study the timing properties of those crystals to assess the feasibility of providing some level of DOI information without significantly degrading the timing performance. We used Monte Carlo simulations to provide a detailed understanding of light transport in phosphor-coated crystals which cannot be fully characterized experimentally. Our simulations used a custom reflectance model based on 3D crystal surface measurements. Lutetium oxyorthosilicate (LSO) crystals were simulated with a phosphor coating in contact with the scintillator surfaces and an external diffuse reflector (teflon). Light output, energy resolution, and pulse shape showed excellent agreement with experimental data obtained on 3 × 3 × 10 mm3 crystals coupled to a photomultiplier tube (PMT). Scintillator intrinsic timing resolution was simulated with head-on and side-on configurations, confirming the trends observed experimentally. These results indicate that the model may be used to predict timing properties in phosphor-coated crystals and guide the coating for optimal DOI resolution/timing performance trade-off for a given crystal geometry. Simulation data suggested that a time stamp generated from early photoelectrons minimizes degradation of the timing resolution, thus making this method potentially more useful for TOF-DOI detectors than our initial experiments suggested. Finally, this approach could easily be extended to the study of timing properties in other scintillation crystals, with a range of treatments and materials attached to the surface.

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Design considerations of phoswich detectors for high resolution positron emission tomography

Cited by 8 publications

References 8 publications

Characterization of stacked-crystal PET detector designs for measurement of both TOF and DOI

Characterization of stacked-crystal PET detector designs for measurement of both TOF and DOI

A kind of bilayer structure ceramic scintillators designed for phoswich detectors

Predicting the timing properties of phosphor-coated scintillators using Monte Carlo light transport simulation

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