Simulation of Gaussian energy broadening in gamma response of a LYSO array detector using a semi-empirical method

Taheri, Ali; Askari, Mojtaba; Sasanpour, Mohammad Taghan

doi:10.1140/epjp/i2017-11646-x

Cited by 11 publications

(6 citation statements)

References 9 publications

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“… 11 , for example, observed the typical broad spectrum from an LSO crystal with three main peaks and suggested that these probably resulted from the simultaneous detection of the β-particle plus 88 keV γ-ray, β-particle plus 202 keV γ-ray and β-particle plus 307 keV γ-ray, respectively, but did not deepen into the relative intensities of the peaks. This was also pointed out in other works for LYSO crystals 12 , 13 . More recently, Jeong, M. et al .…”

Section: Introductionsupporting

confidence: 79%

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: Introductionsupporting

confidence: 79%

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: 98%

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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“…However, the Monte Carlo simulation used in this study cannot directly take into account the uncertainty factors. Hence, a special treatment, referred to as Gaussian energy broadening (GEB) treatment as a Gaussian kernel, was used to better simulate the detector system [22]. The treatment broadens the energy peaks by sampling from the following Gaussian function:…”

Section: Monte Carlo Simulationmentioning

confidence: 99%

“…The FHWM is defined as the energy-dependent non-linear response in this code and the expressions of the FHWM are shown below. The parameters a, b, and c were derived from experiments with the standard gamma sources ( 137 Cs, 22 Na, and 133 Ba). The experiment was performed at a controlled temperature with the air temperature set to 18 • C. Temperature is one of the important SiPM characterization factors because it has significant temperature dependency.…”

Section: Monte Carlo Simulationmentioning

confidence: 99%

Discrete Convolution-Based Energy Spectrum Configuring Method for the Analysis of the Intrinsic Radiation of 176Lu

Choi

et al. 2021

Sensors

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There has been considerable interest in inorganic scintillators based on lutetium due to their favorable physical properties. Despite their advantages, lutetium-based scintillators could face issues because of the natural occurring radioisotope of 176Lu that is contained in natural lutetium. In order to mitigate its potential shortcomings, previous works have studied to understand the energy spectrum of the intrinsic radiation of 176Lu (IRL). However, few studies have focused on the various principal types of photon interactions with matter; in other words, only the full-energy peak according to the photoelectric effect or internal conversion have been considered for understanding the energy spectrum of IRL. Thus, the approach we have used in this study considers other principal types of photon interactions by convoluting each energy spectrum with combinations for generating the spectrum of the intrinsic radiation of 176Lu. From the results, we confirm that the method provides good agreement with the experiment. A significant contribution of this study is the provision of a new approach to process energy spectra induced by mutually independent radiation interactions as a single spectrum.

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Simulation of Gaussian energy broadening in gamma response of a LYSO array detector using a semi-empirical method

Cited by 11 publications

References 9 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

Discrete Convolution-Based Energy Spectrum Configuring Method for the Analysis of the Intrinsic Radiation of 176Lu

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