A method for daily setup and quality checks of LSO:Ce based time of flight positron emission tomographs

Rothfuss, H.; Martin, V.; Moor, Andrew; Young, John W.; Kolb, Johann; Eriksson, Lars

doi:10.1109/nssmic.2014.7430916

Cited by 7 publications

(7 citation statements)

References 5 publications

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“…Despite the drawbacks that in certain scenarios this intrinsic radioactivity might represent, several authors have proposed its use as a permanent built-in "field-flood" source [11]. Knoess et al [12] and Rothfuss et al [13] measured detector-block sensitivities and crystal energy spectra using the background radioactivity of LSO crystals, suggesting that this intrinsic background signal can be used for daily quality checks in LSO/LYSO-based PET scanners. Conti et al [14], using a conventional 68 Ge external source and the LSO intrinsic radiation, performed energy calibrations of a PET system, establishing that the positions of the 176 Lu peaks in the energy spectrum can be used for energy calibration without any external source and used in a daily quality control protocol of the scanner.…”

Section: Introductionmentioning

confidence: 99%

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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Section: Introductionmentioning

confidence: 99%

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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“…Additionally, by utilizing simulations based on the identified LYSO 'x' material composition, we can model the radiation transmission through a PET detector accurately. This modeling is instrumental in refining image attenuation correction techniques, as described in the works of Rothfuss et al (2014a) and Omidvari et al (2022).…”

Section: Discussionmentioning

confidence: 99%

“…Calibration of LYSO crystal alignment within the PET system and the alignment of the PET system with respect to a phantom, as elucidated by Wei et al (2016) and Wei et al (2018), relies exclusively on BG radiation measurements. Furthermore, the intrinsic radiation of LYSO has been proposed as a tool for calibrating parameters including depth of interaction (DOI) (Bircher and Shao 2012), flood map estimation, detector sensitivity (Chen et al 2021, Freire et al 2021, timing calibration, and synchronization (Rothfuss et al 2014a, Enríquez-Mier-y Terán et al 2020. Another approach to correctly update for energy calibration drifting via a linear shifting methodology has also been investigated to maintain detector uniformity response, (Conti et al 2010).…”

Section: Introductionmentioning

confidence: 99%

Determination of lutetium density in LYSO crystals: methodology and PET detector applications

Thien,

Nemallapudi

2024

Phys. Med. Biol.

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Objective: Lutetium yttrium oxyorthosilicate (LYSO) scintillation crystals are used in positron emission tomography (PET) due to their high gamma attenuation, fair energy resolution, and fast scintillation decay time. The enduring presence of the 176Lu isotope, characterized by a half-life of 37.9 billion years, imparts a consistent radiation background (BG) profile that depends on the geometry and composition attributes of the LYSO crystals.Approach: In this work, we proposed a methodology for estimating the composition of LYSO crystals in cases where the exact Lutetium composition remains unknown. The connection between BG spectrum intensity and intrinsic radioactivity enables precise estimation of Lutetium density in LYSO crystal samples. This methodology was initially applied to a well-characterized LYSO crystal sample, yielding results closely aligned with the known composition. The composition estimation approach was extended to several samples of undisclosed LYSO crystals, encompassing single crystal and crystal array configurations. Furthermore, we model the background spectrum observed in the LYSO-based detector and validate the observed spectra via simulations.Main results: The estimated Lutetium composition exhibited adequate consistency across different samples of the same LYSO material, with variations of less than 1%. The result of the proposed approach coupled with the simulation successfully models the background radiation spectra in various LYSO-based detector geometries.Significance: The implications of this work extend to the predictive assessment of system behaviors and the autonomous configuration parameters governing LYSO-based detectors.

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“…Furthermore, it enables the estimation of the attenuation image from the PET data, if the spatial distribution of the activity is wider than the TOF resolution of the scanner [2]. The use of TOF-PET data requires accurate alignment of the timing information, which is typically obtained by an additional acquisition of a known activity distribution [3], from background LSO radiation [4] or from the clinical data either iteratively [5] or using analytical consistency conditions [6]. This is becoming increasingly important with improving TOF resolutions of clinical TOF-PET scanners.…”

Section: Introductionmentioning

confidence: 99%

Estimation of Crystal Timing Properties and Efficiencies for the Improvement of (Joint) Maximum-Likelihood Reconstructions in TOF-PET

Rezaei

Schramm

Laere

2020

IEEE Trans. Med. Imaging

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With increasing improvements in the time of flight (TOF) resolution of positron emission tomography (PET) scanners, an accurate model of the TOF measurements is becoming increasingly important. This work considers two parameters of the TOF kernel; the relative positioning of the timing data-bins and the timing resolution along each line of response (LOR). Similar to an existing data-driven method, we assume that any shifts of data-bins along lines of response can be modelled as differences between crystal timing offsets. Inspired by this, timing resolutions of all LORs are modelled as the hypotenuse of timing resolutions of the crystal-pairs in coincidence. Furthermore, in order to mitigate the influence of potential inaccuracies of detector-pair sensitivities on crystal timing resolutions, relative LOR sensitivities are modelled as the product of efficiency factors for the two crystals in coincidence. We validate estimating maps of crystal timing offsets, timing resolutions and efficiencies from the emission data using noisy simulations of a brain phantom. Results are shown for phantom and patient data scanned on clinically available TOF-PET scanners. We find that the estimation of crystal timing resolutions is more sensitive to the data statistics than the estimation of crystal timing offsets. As a result, estimation of crystal timing properties could either be limited to high count emission data, or be obtained utilizing additional regularizations on the estimates. Using a more accurate model of the TOF acquisition, improvements are observed in standard activity reconstructions as well as joint reconstructions of activity and attenuation.

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A method for daily setup and quality checks of LSO:Ce based time of flight positron emission tomographs

Cited by 7 publications

References 5 publications

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

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

Determination of lutetium density in LYSO crystals: methodology and PET detector applications

Estimation of Crystal Timing Properties and Efficiencies for the Improvement of (Joint) Maximum-Likelihood Reconstructions in TOF-PET

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