Experimental Validation of an Efficient Fan-Beam Calibration Procedure for &lt;formula formulatype="inline"&gt;&lt;tex Notation="TeX"&gt;$k$&lt;/tex&gt;&lt;/formula&gt;-Nearest Neighbor Position Estimation in Monolithic Scintillator Detectors

Borghi, G.; Tabacchini, Valerio; Seifert, Stefan; Schaart, Dennis R.

doi:10.1109/tns.2014.2375557

Cited by 43 publications

(58 citation statements)

References 31 publications

(55 reference statements)

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“…For example, our group has recently presented a detector based on a 32 mm × 32 mm × 22 mm LYSO:Ce crystal and a digital photon counter (DPC) array which achieved a x-y spatial resolution ~1.7 mm FWHM/~1.6 mm mean absolute error (MAE), a DOI resolution ~3.7 mm FWHM/~2.2 mm MAE, and a CRT of ~215 ps FWHM (Borghi et al 2016). Also, new methods have been proposed to increase the efficiency of the calibration procedures and of the time and position estimation algorithms (Borghi et al 2015), which had previously been considered a limitation for the practical application of this technology.…”

Section: G Borghi Et Almentioning

confidence: 99%

Sub-3 mm, near-200 ps TOF/DOI-PET imaging with monolithic scintillator detectors in a 70 cm diameter tomographic setup

et al. 2018

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Recently, a monolithic scintillator detector for time-of-flight (TOF)/depth-of-interaction (DOI) positron emission tomography (PET) was developed. It has a detector spatial resolution of ~1.7 mm full-width-at-half-maximum (FWHM), a coincidence resolving time (CRT) of ~215 ps FWHM, and ~4.7 mm FWHM DOI resolution. Here, we demonstrate, for the first time, the imaging performance of this detector in a 70 cm diameter PET geometry. We built a tomographic setup representative of a whole-body clinical scanner, comprising two coaxially rotating arms, each carrying a detector module, and a central, rotating phantom table. The fully automated setup sequentially acquires all possible lines of response (LORs) of a complete detector ring, using a step-and-shoot acquisition approach. The modules contained 2 × 2 detectors, each detector consisting of a 32 mm × 32 mm × 22 mm LYSO crystal and a digital silicon photomultiplier (dSiPM) array. The system spatial resolution was assessed using a Na-22 point source at different radial distances in the field-of-view (FOV). Using 2D filtered back projection (2D FBP, non-TOF), tangential and radial spatial resolutions of ~2.9 mm FWHM were obtained at the center of the FOV. The use of DOI information resulted in almost uniform spatial resolution throughout the FOV up to a radial distance of 25 cm, where the radial and tangential resolution are ~3.3 mm FWHM and ~4.7 mm FWHM, respectively, whereas without DOI the resolution deteriorates to ~9 mm FWHM. Additional measurements were performed with a Na-22 filled Derenzo-like phantom at different locations within the FOV. Images reconstructed with a TOF maximum-likelihood expectation-maximization (TOF ML-EM) algorithm show that the system is able to clearly resolve 3 mm diameter hot rods up to 25 cm radial distance. The excellent and uniform spatial resolution, combined with an energy resolution of 10.2% FWHM and a CRT of ~212 ps FWHM, indicates a great potential for monolithic scintillators as practical high-performance detectors in TOF/DOI-PET systems.

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Section: G Borghi Et Almentioning

confidence: 99%

Sub-3 mm, near-200 ps TOF/DOI-PET imaging with monolithic scintillator detectors in a 70 cm diameter tomographic setup

et al. 2018

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“…Several calibration methods have been proposed that are fast and easy to implement in a real system. Such methods are usually based on a scan of the module using a group of collimated beams, a fan beam irradiation, or a known event distribution in the module [ 24 , 41 , 42 ]. The natural radioactivity of the LYSO has been used to calibrate the DOI response in modules composed of pixellated scintillators with double side readout [ 43 , 44 ], and the same method was applied here to calibrate the DOI parameters.…”

Section: Methodsmentioning

confidence: 99%

Depth of interaction determination in monolithic scintillator with double side SiPM readout

et al. 2017

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BackgroundMonolithic scintillators read out by arrays of photodetectors represent a promising solution to obtain high spatial resolution and the depth of interaction (DOI) of the annihilation photon. We have recently investigated a detector geometry composed of a monolithic scintillator readout on two sides by silicon photomultiplier (SiPM) arrays, and we have proposed two parameters for the DOI determination: the difference in the number of triggered SiPMs on the two sides of the detector and the difference in the maximum collected signal on a single SiPM on each side. This work is focused on the DOI calibration and on the determination of the capability of our detector. For the DOI calibration, we studied a method which can be implemented also in detectors mounted in a full PET scanner. We used a PET detector module composed of a monolithic 20 × 20 × 10 mm3 LYSO scintillator crystal coupled on two opposite faces to two arrays of SiPMs. On each side, the scintillator was coupled to 6 × 6 SiPMs. In this paper, the two parameters previously proposed for the DOI determination were calibrated with two different methods. The first used a lateral scan of the detector with a collimated 511 keV pencil beam at steps of 0.5 mm to study the detector DOI capability, while the second used the background radiation of the 176Lu in the scintillator. The DOI determination capability was tested on different regions of the detector using each parameter and the combination of the two.ResultsWith both parameters for the DOI determination, in the lateral scan, the bias between the mean reconstructed DOI and the real beam position was lower than 0.3 mm, and the DOI distribution had a standard deviation of about 1.5 mm. When using the calibration with the radioactivity of the LYSO, the mean bias increased of about 0.2 mm but with no degradation of the standard deviation of the DOI distribution.ConclusionsThe two parameters allow to achieve a DOI resolution comparable with the state of the art, giving a continuous information about the three-dimensional interaction position of the scintillation. These results were obtained by using simple estimators and a detector scalable to a whole PET system. The DOI calibration obtained using lutetium natural radioactivity gives results comparable to the other standard method but appears more readily applicable to detectors mounted in a full PET scanner.

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“…Later, fanbeam collimators were proposed for calibration. The approach was tested through simulation and experiment for the kNNs algorithm [24], [32]. The positioning calibration of a fan-beam collimator is strictly 1-D.…”

Section: Introductionmentioning

confidence: 99%

Characterization and Simulation of an Adaptable Fan-Beam Collimator for Fast Calibration of Radiation Detectors for PET

Hetzel

Mueller

Grahe

et al. 2020

IEEE Trans. Radiat. Plasma Med. Sci.

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Monolithic scintillators for positron emission tomography systems perform best when calibrated individually. We present a fan-beam collimator with which a crystal can be calibrated within less than 1 h when suitable positioning algorithms are applied. The collimator is manufactured from lead, features an easily adaptable slit to tune the beam width and can be operated together with a coincidence detector to select a clean sample of 511-keV annihilation photons. We evaluated the performance of the collimator with a Geant4 simulation for slit widths of 0.25 mm, 0.4 mm, and 1 mm and validated the shape of the beam profile experimentally by step-wisely moving a detector into the beam. This shows a clear narrow and box-shaped beam profile even if the collimator is operated without the coincidence setup. In the latter configuration, the fraction of gammas in the beam region on a 50×50 mm 2 large detector is between 48% and 79% which is improved significantly to more than 94% by using only coincidence events. Analyzing the energy distribution shows that the fraction of 511-keV photons is increased from less than 50% to more than 96% by selecting coincidences.

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Experimental Validation of an Efficient Fan-Beam Calibration Procedure for <formula formulatype="inline"><tex Notation="TeX">$k$</tex></formula>-Nearest Neighbor Position Estimation in Monolithic Scintillator Detectors

Cited by 43 publications

References 31 publications

Sub-3 mm, near-200 ps TOF/DOI-PET imaging with monolithic scintillator detectors in a 70 cm diameter tomographic setup

Sub-3 mm, near-200 ps TOF/DOI-PET imaging with monolithic scintillator detectors in a 70 cm diameter tomographic setup

Depth of interaction determination in monolithic scintillator with double side SiPM readout

Characterization and Simulation of an Adaptable Fan-Beam Collimator for Fast Calibration of Radiation Detectors for PET

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