Study and optimization of positioning algorithms for monolithic PET detectors blocks

Acilu, P. Garcia de; Sarasola, I.; Canadas, M.; Cuerdo, R.; Mendes, P. Rato; Romero, L.; Willmott, C.

doi:10.1088/1748-0221/7/06/c06010

Cited by 13 publications

(4 citation statements)

References 12 publications

(20 reference statements)

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“…Different approaches have been proposed to extract DOI information from a monolithic crystal by using neural networks [18], [19]. Despite the good results reported, the need of intensive calibration makes them difficult to implement in a real system.…”

Section: Doi Computation Using Light-spot Statisticsmentioning

confidence: 99%

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A CMOS Digital SiPM With Focal-Plane Light-Spot Statistics for DOI Computation

et al. 2017

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Silicon photomultipliers can be used to infer the depth-of-interaction (DOI) in scintillator crystals. DOI can help to improve the quality of the positron emission tomography images affected by the parallax error. This paper contemplates the computation of DOI based on the standard deviation of the light distribution. The simulations have been carried out by GAMOS. The design of the proposed digital silicon photomultiplier (d-SiPM) with focal plane detection of the center of mass position and dispersion of the scintillation light is presented. The d-SiPM shares the same off-chip time-to-digital converter such that each pixel can be individually connected to it. A miniature d-SiPM 8×8 single-photon avalanche-diode (SPAD) array has been fabricated as a proof of concept. The SPADs along each row and column are connected through an OR combination technique. It has 256×256µm 2 without peripherals circuits and pads. The fill factor is about 11%. The average dark count rate of the mini d-SiPM is of 240kHz. The average photon detection efficiency is 5% at 480nm wavelength, room temperature and 0.9V excess voltage. The dynamic range is of 96dB. The sensor array features a time resolution of 212ps. The photon-timing SNR is 81dB. The focal plane statistics of the lightspot has been proved as well by measurements. Index Terms-single photon avalanche diode (SPAD), digital silicon photomultiplier (d-SiPM), time-of-flight (ToF), focal-plane processing, scintillation light spot dispersion

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Section: Doi Computation Using Light-spot Statisticsmentioning

confidence: 99%

“…1-bottom inset). It has been an important research line in PET imaging in the last years [17], [18], [19], [20] and [21]. Pixelated crystals can help reducing these errors, but they are usually much more expensive than single crystals.…”

Section: Introductionmentioning

confidence: 99%

A CMOS Digital SiPM With Focal-Plane Light-Spot Statistics for DOI Computation

et al. 2017

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“…Detectors for application in whole-body clinical PET systems, on the other hand, are usually optimized for detection efficiency, time resolution, and energy resolution, at the expense of spatial resolution (Surti et al 2007, Lois et al 2010, Jakoby et al 2009. Detectors that utilize monolithic scintillators on multi-channel light sensors are capable of high spatial resolution without compromising on the energy performance (Bruyndonckx et al 2004, Maas et al 2006, van der Laan et al 2007, Llosá et al 2010, van Dam et al 2011a, de Acilu et al 2012, Sarasola et al 2011, Miyaoka et al 2008. Moreover, monolithic scintillator detectors intrinsically provide DOI information (van Dam et al 2011b, Carles et al 2012), are relatively uncomplicated to assemble, and can offer an excellent coincidence resolving time (Seifert et al 2012a, van Dam et al 2013.…”

Section: Introductionmentioning

confidence: 99%

First characterization of a digital SiPM based time-of-flight PET detector with 1 mm spatial resolution

Seifert¹,

Lei²,

Dam³

et al. 2013

Phys. Med. Biol.

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Monolithic scintillator detectors can offer a combination of spatial resolution, energy resolution, timing performance, depth-of-interaction information, and detection efficiency that make this type of detector a promising candidate for application in clinical, time-of-flight (TOF) positron emission tomography (PET). In such detectors the scintillation light is distributed over a relatively large number of photosensor pixels and the light intensity per pixel can be relatively low. Therefore, monolithic scintillator detectors are expected to benefit from the low readout noise offered by a novel photosensor called the digital silicon photomultiplier (dSiPM). Here, we present a first experimental characterization of a TOF PET detector comprising a 24 × 24 × 10 mm(3) LSO:Ce,0.2%Ca scintillator read out by a dSiPM array (DPC-6400-44-22) developed by Philips Digital Photon Counting. A spatial resolution of ~1 mm full-width-at-half-maximum (FWHM) averaged over the entire crystal was obtained (varying from just below 1 mm FWHM in the detector center to ~1.2 mm FWHM close to the edges). Furthermore, the bias in the position estimation at the crystal edges that is typically found in monolithic scintillators is well below 1 mm even in the corners of the crystal.

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“…Later, the same group used the categorical-average-patternnearest-neighbours method (van Dam et al 2011), improving the spatial resolution and reducing the required calibration data acquisition. As part of pattern recognition methods, artificial neural networks (ANN) have also been used for small animal PET scanners (Bruyndonckx et al 2004) and brain PET scanners (de Acilu et al 2012).…”

Section: Introductionmentioning

confidence: 99%

Simulation study of PET detector limitations using continuous crystals

et al. 2015

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Continuous crystals can potentially obtain better intrinsic detector spatial resolution compared to pixelated crystals, additionally providing depth of interaction (DoI) information from the light distribution. To achieve high performance sophisticated interaction position estimation algorithms are required. There are a number of algorithms in the literature applied to different crystal dimensions and different photodetectors. However, the different crystal properties and photodetector array geometries have an impact on the algorithm performance. In this work we analysed, through Monte Carlo simulations, different combinations of realistic crystals and photodetector parameters to better understand their influence on the interaction position estimation accuracy, with special emphasis on the DoI. We used an interaction position estimation based on an analytical model for the present work. Different photodetector granulation schemes were investigated. The impact of the number of crystal faces readout by photodetectors was studied by simulating scenarios with one and two photodetectors. In addition, crystals with different levels of reflection and aspect ratios (AR) were analysed. Results showed that the impact of photodetector granularity is mainly shown near the edges and specially in the corners of the crystal. The resulting intrinsic spatial resolution near the centre with a 12 × 12 × 10 mm(3) LYSO crystal was 0.7-0.9 mm, while the average spatial resolution calculated on the entire crystal was 0.77 ± 0.18 mm for all the simulated geometries with one and two photodetectors. Having front and back photodetectors reduced the DoI bias (Euclidean distance between estimated DoI and real DoI) and improved the transversal resolution near the corners. In scenarios with one photodetector, small AR resulted in DoI inaccuracies for absorbed events at the entrance of the crystal. These inaccuracies were slightly reduced either by increasing the AR or reducing the amount of reflected light, and highly mitigated using two photodetectors. Using one photodetector, we obtained a piecewise DoI error model with a DoI resolution of 0.4-0.9 mm for a 1.2 AR crystal, and we observed that including a second photodetector or reducing the amount of reflections reduced the DoI bias but did not significantly improve the DoI resolution. Translating the piecewise DoI error model obtained in this study to image reconstruction we obtained a spatial resolution variability of 0.39 mm using 85% of the FoV, compared to 2.59 mm and 1.87 mm without DoI correction or with a dual layer system, respectively.

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Study and optimization of positioning algorithms for monolithic PET detectors blocks

Cited by 13 publications

References 12 publications

A CMOS Digital SiPM With Focal-Plane Light-Spot Statistics for DOI Computation

A CMOS Digital SiPM With Focal-Plane Light-Spot Statistics for DOI Computation

First characterization of a digital SiPM based time-of-flight PET detector with 1 mm spatial resolution

Simulation study of PET detector limitations using continuous crystals

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