Comparison between Pixelated Scintillators: CsI(Tl), LaCl 3(Ce) and LYSO(Ce) when coupled to a Silicon Photomultipliers Array

Jeong, Manhee; Van, Benjamin; Wells, Byron T.; D’Aries, Lawrence J.; Hammig, Mark D.

doi:10.1016/j.nima.2018.03.024

Cited by 22 publications

(7 citation statements)

References 33 publications

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“… 12 for a 10 × 10 × 10 mm 2 crystal and by Jeong, M. et al . 14 for 50.8 × 50.8 × 10 mm 2 crystals are in good agreement with our predictions, the latter in spite of using a pixelated crystal array and a different photodetector.…”

Section: Discussionsupporting

confidence: 89%

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Understanding the intrinsic radioactivity energy spectrum from 176Lu in LYSO/LSO scintillation crystals

Alva‐Sánchez

Zepeda-Barrios

Díaz-Martínez

et al. 2018

Sci Rep

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Lutetium oxyorthosilicate (LSO) or lutetium yttrium oxyorthosilicate (LYSO) are the scintillator materials most widely used today in PET detectors due to their convenient physical properties for the detection of 511 keV annihilation photons. Natural lutetium contains 2.6% of 176Lu which decays beta to excited states of 176Hf producing a constant background signal. Although previous works have studied the background activity from LSO/LYSO, the shape of the spectrum, resulting from β-particle and γ radiation self-detection, has not been fully explained. The present work examines the contribution of the different β-particle and γ-ray interactions to provide a fuller comprehension of this background spectrum and to explain the differences observed when using crystals of different sizes. To this purpose we have shifted the continuous β-particle energy spectrum of 176Lu from zero to the corresponding energy value for all combinations of the isomeric transitions of 176Hf (γ-rays/internal conversion). The area of each shifted β-spectrum was normalized to reflect the probability of occurrence. To account for the probability of the γ-rays escaping from the crystal, Monte Carlo simulations using PENELOPE were performed in which point-like sources of monoenergetic photons were generated, inside LYSO square base prisms (all 1 cm thick) of different sizes: 1.0 cm to 5.74 cm. The analytic distributions were convolved using a varying Gaussian function to account for the measured energy resolution. The calculated spectra were compared to those obtained experimentally using monolithic crystals of the same dimensions coupled to SiPM arrays. Our results are in very good agreement with the experiment, and even explain the differences observed due to crystal size. This work may prove useful to calibrate and assess detector performance, and to measure energy resolution at different energy values.

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Section: Discussionsupporting

confidence: 89%

“…More recently, Jeong, M. et al . 14 published the energy spectrum from two pixelated LYSO crystal sizes (50.8 × 50.8 × 5 mm 3 and 50.8 × 50.8 × 10 mm 3 ), but did not dwell upon the clearly visible differences in the relative intensities of the broad peaks.…”

Section: Introductionmentioning

confidence: 99%

Understanding the intrinsic radioactivity energy spectrum from 176Lu in LYSO/LSO scintillation crystals

Alva‐Sánchez

Zepeda-Barrios

Díaz-Martínez

et al. 2018

Sci Rep

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“…Using the background radiation as a "field-flood" source for detector calibration and attenuation correction requires a complete characterization and understanding of the 176 Lu intrinsic energy spectrum in singles and coincidence mode. In singles mode, this intrinsic energy spectrum has been previously reported [17][18][19][20][21]. In 2010, Goertzen et al [22] developed a method for estimating the energy spectrum of coincidence events in a PET system and compared it with measurements and Monte Carlo simulations using GATE (Geant4 Application for Tomographic Emission) [23].…”

Section: Introductionmentioning

confidence: 97%

Coincidence energy spectra due to the intrinsic radioactivity of LYSO scintillation crystals

Enriquez-Mier-y-Teran¹,

Ortega-Galindo²,

Murrieta-Rodríguez³

et al. 2020

EJNMMI Phys

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Background: Lutetium oxyorthosilicate or lutetium yttrium oxyorthosilicate (LYSO) scintillation crystals used in most current PET scanner detectors contain 176 Lu, which decays by beta emission to excited states of 176 Hf accompanied by the emission of prompt gamma rays or internal conversion electrons. This intrinsic radioactivity can be self-detected in singles mode as a constant background signal that has an energy spectrum whose structure has been explained previously. In this work, we studied the energy spectrum due to the intrinsic radioactivity of LYSO scintillation crystals of two opposing detectors working in coincidence mode. The investigation included experimental data, Monte Carlo simulations and an analytical model. Results: The structure of the energy spectrum was completely understood and is the result of the self-detection of beta particles from 176 Lu in one crystal and the detection of one or more prompt gamma rays detected in coincidence by the opposing crystal. The most probable coincidence detection involves the gamma rays of 202 and 307 keV, which result in two narrow photopeaks, superimposed on a continuous energy distribution due to the beta particle energy deposition. The relative intensities of the gamma ray peaks depend on crystal size and detector separation distance, as is explained by the analytical model and verified through the Monte Carlo simulations and experiments. Conclusions: The analytical model used in this work accurately explains the general features of the coincidence energy spectrum due to the presence of 176 Lu in the scintillation crystals, as observed experimentally and with Monte Carlo simulations. This work will be useful to those research studies aimed at using the intrinsic radioactivity of LYSO crystals for transmission scans and detector calibration in coincidence mode.

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“…Note, however, that the maximum end-point energy at 1190 keV (the Q-value of the decay 176 Lu to 176 Hf) remains unchained and is an important landmark. The peak shifting as a result of filtering (finite energy resolution) is important, can be observed in background energy spectra published by other research groups, 14,24,57,58 has led to detector miscalibration in the past, and needs to be taken into account if a correct detector energy assessment is to be attained using the intrinsic background radiation.…”

Section: D Filtering Of Energy Spectramentioning

confidence: 99%

Energy spectra due to the intrinsic radiation of LYSO/LSO scintillators for a wide range of crystal sizes

Domínguez-Jiménez

Alva‐Sánchez

2021

Medical Physics

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Most detectors in current positron emission tomography (PET) scanners and prototypes use lutetium oxyorthosilicate (LSO) or lutetium yttrium oxyorthosilicate (LYSO) scintillators. The aim of this work is to provide a complete set of background energy spectra, due to the scintillator intrinsic radioactivity, for a wide range of crystal sizes. Methods: An analytical model, developed and validated in a previous work, was used to obtain the background energy spectra of square base cuboids of different dimensions. The model uses the photon absorption probabilities of the three gamma rays (88, 202, and 307 keV) emitted following the beta decay of 176 Lu to 176 Hf excited states. These probabilities were obtained for each crystal size considered in this work from Monte Carlo simulations using the PENELOPE code. The probabilities are then used to normalize and shift the beta spectrum to the corresponding energy value of the simultaneous detection of one, two, or three gamma rays in the scintillator. The simulated cuboids had side lengths of 5, 10, 20, 30, 40, 50, and 60 mm and crystal thickness T = 2.5, 5, 10, 15, and 20 mm. From these results a complete set of energy spectra, including intermediate dimensions, were obtained. In addition, LYSO and LSO were compared in terms of their analytical background energy spectra for two crystal sizes. The analytical spectra were convolved using a variable Gaussian kernel to account for the energy resolution of a typical detector. A parameterization of the photon absorption probabilities for each gamma ray energy as a function of the cuboid volume to surface area ratio was obtained. Results: A data set of L(Y)SO background energy spectra was obtained and is available for the reader as 2D histograms. The model accurately predicts the structure of the energy spectra including the relative peak and valley intensities. The data allow visualizing how the structure evolves with increasing crystal length and thickness. Lutetium yttrium oxyorthosilicate and LSO present very similar background energy spectra for the range of sizes studied in this work and therefore the data generated can be confidently used for both scintillator materials. The filtered spectra showed a variable shift in the main peaks, depending on crystal size, alerting that to achieve a correct detector calibration using the background spectrum is not straight forward and requires precise data analysis and measurements. In addition, we found that square base L(Y)SO cuboids with same volume to surface area ratio have background spectra with the same structure. Conclusions: We present the energy spectra of L(Y)SO crystal of different sizes which will be very useful for industry and research groups developing and simulating detectors for positron imaging applications in terms of calibration, quality assurance, crystal maps, detector fine gain tuning, background reduction and other applications using the long-lived 176 Lu source. We analyzed the data produced in this work and found that crystal cuboids with equal volume to su...

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Comparison between Pixelated Scintillators: CsI(Tl), LaCl 3(Ce) and LYSO(Ce) when coupled to a Silicon Photomultipliers Array

Cited by 22 publications

References 33 publications

Understanding the intrinsic radioactivity energy spectrum from 176Lu in LYSO/LSO scintillation crystals

Understanding the intrinsic radioactivity energy spectrum from 176Lu in LYSO/LSO scintillation crystals

Coincidence energy spectra due to the intrinsic radioactivity of LYSO scintillation crystals

Energy spectra due to the intrinsic radiation of LYSO/LSO scintillators for a wide range of crystal sizes

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