Evaluation of a 25&amp;#x2013;511keV list mode readout system for a large field-of-view gamma camera

Villena, Jose L.; Tapias, G.; Lage, Eduardo; Kreuger, R.; Beekman, Freek J.

doi:10.1109/nssmic.2010.5874166

Cited by 5 publications

(6 citation statements)

References 9 publications

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“…Prior to testing the thick scintillator designs we present, the simulation model was validated by comparing its results with experimental data previously collected. 29 Accordingly, we reproduced the same detector geometry consisting of a 9.5 mm thick crystal, a 16 mm thick light guide, and the 3-inch round PMT configuration described earlier. Such a setup was exclusively used for validation purposes.…”

Section: Validation Of Simulation Modelmentioning

confidence: 99%

“…The data acquisition followed the same procedure as reported in the previous section. For validation purposes, the detector performance was evaluated by using the same offline processing that was also applied to the experimental data, 29 consisting of a centroid estimation algorithm based on thresholding. The ɣ interaction positions were reconstructed via Anger Logic estimation, and the Line Response Functions (LRFs) were fitted with a Gaussian function.…”

Section: Validation Of Simulation Modelmentioning

confidence: 99%

“…and 16 mm thick light guide (lg) read out by the 3-inch round PMTs setup. 29 Equivalent images (not shown) were obtained with a horizontal line source. PMT, photomultiplier tube.…”

Section: Maximum Likelihood Estimation and System Matrixmentioning

confidence: 99%

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NaI gamma camera performance for high energies: Effects of crystal thickness, photomultiplier tube geometry and light guide thickness

Cosmi,

Wang,

Goorden

et al. 2024

Medical Physics

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BackgroundGamma camera imaging, including single photon emission computed tomography (SPECT), is crucial for research, diagnostics, and radionuclide therapy. Gamma cameras are predominantly based on arrays of photon multipliers tubes (PMTs) that read out NaI(Tl) scintillation crystals. In this way, standard gamma cameras can localize ɣ‐rays with energies typically ranging from 30 to 360 keV. In the last decade, there has been an increasing interest towards gamma imaging outside this conventional clinical energy range, for example, for theragnostic applications and preclinical multi‐isotope positron emission tomography (PET) and PET‐SPECT. However, standard gamma cameras are typically equipped with 9.5 mm thick NaI(Tl) crystals which can result in limited sensitivity for these higher energies.PurposeHere we investigate to what extent thicker scintillators can improve the photopeak sensitivity for higher energy isotopes while attempting to maintain spatial resolution.MethodsUsing Monte Carlo simulations, we analyzed multiple PMT‐based configurations of gamma detectors with monolithic NaI (Tl) crystals of 20 and 40 mm thickness. Optimized light guide thickness together with 2‐inch round, 3‐inch round, 60 × 60 mm2 square, and 76 × 76 mm2 square PMTs were tested. For each setup, we assessed photopeak sensitivity, energy resolution, spatial, and depth‐of‐interaction (DoI) resolution for conventional (140 keV) and high (511 keV) energy ɣ using a maximum‐likelihood algorithm. These metrics were compared to those of a “standard” 9.5 mm‐thick crystal detector with 3‐inch round PMTs.ResultsEstimated photopeak sensitivities for 511 keV were 27% and 53% for 20 and 40 mm thick scintillators, which is respectively, 2.2 and 4.4 times higher than for 9.5 mm thickness. In most cases, energy resolution benefits from using square PMTs instead of round ones, regardless of their size. Lateral and DoI spatial resolution are best for smaller PMTs (2‐inch round and 60 × 60 mm2 square) which outperform the more cost‐effective larger PMT setups (3‐inch round and 76 × 76 mm2 square), while PMT layout and shape have negligible (< 10%) effect on resolution. Best spatial resolution was obtained with 60 × 60 mm2 PMTs; for 140 keV, lateral resolution was 3.5 mm irrespective of scintillator thickness, improving to 2.8 and 2.9 mm for 511 keV with 20 and 40 mm thick crystals, respectively. Using the 3‐inch round PMTs, lateral resolutions of 4.5 and 3.9 mm for 140 keV and of 3.5 and 3.7 mm for 511 keV were obtained with 20 and 40 mm thick crystals respectively, indicating a moderate performance degradation compared to the 3.5 and 2.9 mm resolution obtained by the standard detector for 140 and 511 keV. Additionally, DoI resolution for 511 keV was 7.0 and 5.6 mm with 20 and 40 mm crystals using 60 × 60 mm2 square PMTs, while with 3‐inch round PMTs 12.1 and 5.9 mm were obtained.ConclusionDepending on PMT size and shape, the use of thicker scintillator crystals can substantially improve detector sensitivity at high gamma energies, while spatial resolution is slightly improved or mildly degraded compared to standard crystals.

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Section: Validation Of Simulation Modelmentioning

confidence: 99%

Section: Validation Of Simulation Modelmentioning

confidence: 99%

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NaI gamma camera performance for high energies: Effects of crystal thickness, photomultiplier tube geometry and light guide thickness

Cosmi,

Wang,

Goorden

et al. 2024

Medical Physics

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“…The interaction position and energy for each event are both estimated with Anger logic (centroid of gravity) and ML: the result of the former is the start location of the search in the latter. To improve Anger estimation, a threshold is applied to each PMT output followed by a linearity correction [31].…”

Section: Position and Energy Estimationmentioning

confidence: 99%

Experimental Validation of a Gamma Detector With a Novel Light-Guide-PMT Geometry to Reduce Dead Edge Effects

Wang

Kreuger

Huizenga

et al. 2020

IEEE Trans. Radiat. Plasma Med. Sci.

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Photomultiplier tube (PMT)-based scintillation cameras are predominant in molecular imaging but have the drawback that position estimation is severely degraded near the edges (dead edge effect). This leads to sensitivity losses and can cause severe problems in applications like molecular breast imaging and in certain SPECT devices. Using smaller light sensors or semiconductor detectors can solve this issue but leads to increased costs. Here we present a gamma detector based on standard PMTs with a novel light-guide-PMT geometry that strongly reduces dead edges. In our design, a monolithic NaI(Tl) scintillator is read out by square PMTs placed in a staggered arrangement. At the edge of the scintillator we inserted additional light-guides to emulate half-size PMTs. Detector performance was assessed for 99m Tc imaging; an average spatial resolution of 3.6 mm was measured over the whole detector, degrading to 4.0 mm within 30 mm to the critical edge. The dead edge of the scintillator is <3 mm. Since a 12-mm seal was used, the overall dead edge is <15 mm, which is a significant improvement over conventional Anger cameras (∼40-mm dead edge). Therefore, the presented geometry can be useful in creating economical gamma detectors with reduced dead edges.

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“…The threshold in our case is set as 3% of the total summed PMT output at every detection. We apply a linearity correction as is commonly done for Anger cameras in the same way as described in [42] with linearity correction map obtained from the PRF data.…”

Section: Data Processingmentioning

confidence: 99%

Novel light-guide-PMT geometries to reduce dead edges of a scintillation camera

et al. 2018

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Evaluation of a 25–511keV list mode readout system for a large field-of-view gamma camera

Cited by 5 publications

References 9 publications

NaI gamma camera performance for high energies: Effects of crystal thickness, photomultiplier tube geometry and light guide thickness

NaI gamma camera performance for high energies: Effects of crystal thickness, photomultiplier tube geometry and light guide thickness

Experimental Validation of a Gamma Detector With a Novel Light-Guide-PMT Geometry to Reduce Dead Edge Effects

Novel light-guide-PMT geometries to reduce dead edges of a scintillation camera

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