Continuous depth-of-interaction measurement in a single-layer pixelated crystal array using a single-ended readout

Ito, Mikiko; Lee, Min Sun; Lee, Jae Sung

doi:10.1088/0031-9155/58/5/1269

Cited by 65 publications

(48 citation statements)

References 46 publications

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“…In long axial field-of-view PET scanners or preclinical systems with tight bore diameters, detectors that encode depth-of-interaction (DOI) have also been developed to correct parallax errors. These detectors often use customized designs with very specific crystal surface treatments (Ito et al , 2013; Yang et al , 2006; Roncali et al , 2014b) that are optimized with simulations (Ito et al , 2010). To perform those simulations, optical models have been implemented in the widely distributed opensource software Geant4 (Agostinelli et al , 2003; Pizzichemi et al , 2012) and GATE (Jan et al , 2004; Cuplov et al , 2014), based on previous work done in DETECT2000 (Levin and Moisan, 1996).…”

Section: Introductionmentioning

confidence: 99%

An integrated model of scintillator-reflector properties for advanced simulations of optical transport

Roncali

Stockhoff

Cherry³

2017

Phys. Med. Biol.

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Accurately modeling the light transport in scintillation detectors is essential to design new detectors for nuclear medicine or high energy physics. Optical models implemented in software such as Geant4 and GATE suffer from important limitations that we addressed by implementing a new approach in which the crystal reflectance was computed from 3D surface measurements. The reflectance was saved in a look-up-table (LUT) then used in Monte Carlo simulation to determine the fate of optical photons. Our previous work using this approach demonstrated excellent agreement with experimental characterization of crystal light output in a limited configuration, i.e. when using no reflector. As scintillators are generally encapsulated in a reflector, it is essential to include the crystal-reflector interface in the LUT. Here we develop a new LUT computation and apply it to several reflector types. A second LUT that contains transmittance data is also saved to enable modeling of optical crosstalk. LUTs have been computed for rough and polished crystals coupled to a Lambertian (e.g. Teflon tape) or a specular reflector (e.g. ESR) using air or optical grease, and the light output was computed using custom Monte Carlo code. 3 × 3 × 20 mm3 lutetium oxyorthosilicate crystals were prepared using these combinations, and the light output was measured experimentally at different irradiation depths. For all reflector and surface finish combinations, the measured and simulated light output showed very good agreement. The behavior of optical photons at the interface crystal-reflector was studied using these simulations, and results highlighted the large difference in optical properties between rough and polished crystals, and Lambertian and specular reflectors. These simulations also showed how the travel path of individual scintillation photons was affected by the reflector and surface finish. The ultimate goal of this work is to implement this model in Geant4 and GATE, and provide a database of scintillators combined with a variety of reflectors.

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Section: Introductionmentioning

confidence: 99%

An integrated model of scintillator-reflector properties for advanced simulations of optical transport

Roncali

Stockhoff

Cherry³

2017

Phys. Med. Biol.

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“…Note that we choose the rectangular windows to validate the four‐crystals‐to‐one‐SiPM coupling technology, because they are simple and easy to fabricate with good precision. The four‐crystals‐to‐one‐SiPM coupling technology presented in this paper can be adapted in designs with different light‐sharing windows, including rectangular windows, triangular windows, and the combinations of windows with different shapes …”

Section: Discussionmentioning

confidence: 99%

“…The four-crystals-to-one-SiPM coupling technology presented in this paper can be adapted in designs with different light-sharing windows, including rectangular windows, triangular windows, and the combinations of windows with different shapes. [35][36][37][38][39][40] Generally, there are two major challenges in design and construct a high-performance DOI detector using the LSW method. The first one is to optimize the geometry and optical properties of the LSWs and reflectors.…”

Section: Discussionmentioning

confidence: 99%

“…Many LSWs, including rectangular windows, triangular windows, and the combinations of windows with different shapes, have been proposed. [35][36][37][38][39][40] Optical simulation studies have been conducted to compare the DOI performance of four different light-sharing configurations, including the single-rectangular-window configuration, the double-rectangular-window configuration, the single-triangular-window configuration, and the double-triangular-window configuration. 41 The effects of the two types of reflectors, including the diffuse reflector and the specular reflector, were also evaluated.…”

Section: Introductionmentioning

confidence: 99%

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A depth encoding PET detector using four‐crystals‐to‐one‐SiPM coupling and light‐sharing window method

et al. 2019

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Purpose Depth of interaction (DOI) decoding capability is of great importance for positron emission tomography (PET) requiring high resolution. In this study, we presented a novel low‐cost DOI detector design with four crystals coupling to one SiPM, based on the method of rectangular light‐sharing window (RLSW). A prototype detector was constructed, calibrated, and assessed using the methods of homogeneous radiation and flood map analysis. Methods The DOI detector was constructed with a 4 × 4 array of lutetium‐yttrium oxyorthosilicate (LYSO) crystals (2.95 mm × 2.95 mm × 20 mm3), barium sulfate (BaSO4) reflectors, and optical glues. A RLSW 7 mm in height was deployed in the BaSO4 reflectors. A non‐DOI detector with identical dimensions and without RLSW was also constructed for comparison. The light‐output surface of the detector was air‐coupled with a 4 × 4 array of SiPMs (3 mm × 3 mm2). The signals generated from the 16 SiPMs were read out by a custom‐designed electronic system, and the signals from four adjacent 3 mm SiPMs were summed into one signal to emulate a 2 × 2 array of 6 mm SiPMs. The RLSW caused the DOI‐related position shifts of the crystal spots in the flood map. A homogeneous radiation method was used to establish the transfer functions to convert the spot shifts measured from the flood map into DOI measurements. The accuracy of the DOI measurements was assessed with data acquired using the conventional collimated radiation method. Results All 16 crystals are distinctly separated from each other in the flood map. Twelve crystals, including four central crystals and eight edge crystals, have the DOI capability. The full width half maximum (FWHM) of the DOI measurements of the central crystals and the edge crystals are 3.06 ± 0.08 and 3.79 ± 0.15 mm, respectively, for the configuration with four crystals coupling to one SiPM. By contrast, the FWHMs (3.98 ± 0.16 and 5.12 ± 0.38 mm, respectively) are slightly worse for the configuration with one crystal coupling to one SiPM. The average and standard deviation (STD) of the FWHM energy resolutions of the DOI detector and non‐DOI detector were 10.2% ± 0.7% and 10.7% ± 1.7%, respectively. Their FWHM coincidence timing resolutions were 197.0 ± 9.6 and 206.4 ± 13.3 ps, respectively. The RLSW had no significant impact on the energy resolutions and timing resolutions of the DOI detector. Conclusions The novel four‐crystals‐to‐one‐SiPM coupling technology is a cost‐efficient approach to construct high‐performance detector modules with DOI capability. The methods of homogeneous radiation and flood map analysis are easy to perform and of good performance. Those methods can be adapted in the clinic PET scanners to enable the capability of DOI measurements.

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“…Many designs have an increased number of photosensors such as dual-ended readout (Kang, Ko, Rhee, Kim, Lee & Hong 2015), or multi-layered detectors (Yeom, Vinke & Levin 2014). Other methods do not use increased number of photodetectors such as using scintillation shape (rise or decay times) (Schmall, Surti & Karp 2015) (Roncali, Schmall, Viswanath, Berg & Cherry 2014) or light sharing (Van Dam, Borghi, Seifert & Schaart 2013) (Ito, Lee & Lee 2013) to give DOI information. However, many of these methods require active cooling or a significant increase in PET detector readout complexity to measure the light spread or scintillation shape accurately.…”

Section: Introductionmentioning

confidence: 99%

A multiplexed TOF and DOI capable PET detector using a binary position sensitive network

2016

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Time of flight (TOF) and depth of interaction (DOI) capabilities can significantly enhance the quality and uniformity of positron emission tomography (PET) images. Many proposed TOF/DOI PET detectors require complex readout systems using additional photosensors, active cooling, or waveform sampling. This work describes a high performance, low complexity, room temperature TOF/DOI PET module. The module uses multiplexed timing channels to significantly reduce the electronic readout complexity of the PET detector while maintaining excellent timing, energy, and position resolution. DOI was determined using a two layer light sharing scintillation crystal array with a novel binary position sensitive network. A 20mm effective thickness LYSO crystal array with four 3mm × 3mm silicon photomultipliers (SiPM) read out by a single timing channel, one energy channel and two position channels achieved a full width half maximum (FWHM) coincidence time resolution of 180 ± 2ps with 10mm of DOI resolution and 11% energy resolution. With sixteen 3mm × 3mm SiPMs read out by a single timing channel, one energy channel and four position channels a coincidence time resolution 204 ± 1ps was achieved with 10mm of DOI resolution and 15% energy resolution. The methods presented here could significantly simplify the construction of high performance TOF/DOI PET detectors.

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Continuous depth-of-interaction measurement in a single-layer pixelated crystal array using a single-ended readout

Cited by 65 publications

References 46 publications

An integrated model of scintillator-reflector properties for advanced simulations of optical transport

An integrated model of scintillator-reflector properties for advanced simulations of optical transport

A depth encoding PET detector using four‐crystals‐to‐one‐SiPM coupling and light‐sharing window method

A multiplexed TOF and DOI capable PET detector using a binary position sensitive network

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