Scintillator-based Photon Counting Detector: Is it feasible?

Blackberg, Lisa; Moebius, Michael; Moghadam, Narjes; Ozsahin, Dilber Uzun; Mazur, Eric; Fakhri, Georges El; Sabet, Hamid

doi:10.1109/nssmic.2016.8069382

Cited by 5 publications

(13 citation statements)

References 16 publications

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“…In Ref. [18] and Fig. 2a we show that by changing the laser pulse duration the roughness of the interface between the optical barriers and the crystal bulk can be altered.…”

Section: Scintillator Processing Using Liobmentioning

confidence: 81%

Light Spread Manipulation in Scintillators Using Laser Induced Optical Barriers

Blackberg

Moebius

Fakhri

et al. 2018

IEEE Trans. Nucl. Sci.

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“…In Ref. [18] and Fig. 2a we show that by changing the laser pulse duration the roughness of the interface between the optical barriers and the crystal bulk can be altered.…”

Section: Scintillator Processing Using Liobmentioning

confidence: 81%

Light Spread Manipulation in Scintillators Using Laser Induced Optical Barriers

Blackberg

Moebius

Fakhri

et al. 2018

IEEE Trans. Nucl. Sci.

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“…Furthermore, we have shown that the roughness of the interface between the barriers and the unmodified crystal can be controlled to some extent by varying laser parameters (Bläckberg et al 2016a). However, to this date, and to the best of our knowledge, no one has been able to show exactly how different laser parameters are linked to the optical barrier properties.…”

Section: Methodsmentioning

confidence: 99%

“…This is especially a complex task given the large laser parameter space in combination with difficulties to use standard methods to measure the barrier properties in thick crystals. In this work we chose a range of RI values and interface roughness values that are possible to achieve based on our prior experimental results (Sabet et al 2014, Bläckberg et al 2016a) and the literature. Given that the RI and the interface roughness are two distinct parameters and not necessarily correlated, all combinations of the two parameters were studied.…”

Section: Methodsmentioning

confidence: 99%

“…These techniques have found their way in a variety of medical imaging applications including Positron Emission Tomography (PET) (Moriya et al 2010, Sabet et al 2012a, Hunter et al 2015, Sabet et al 2016a, Uchida et al 2016, Bläckberg et al 2016b), Single Photon Emission Computed Tomography (SPECT) (Sabet et al 2016b), and Computed Tomography (CT) (Bläckberg et al 2016a). In LIOB a high power pulsed laser is tightly focused inside the bulk of a scintillator crystal, causing a local modification of the crystal structure.…”

Section: Introductionmentioning

confidence: 99%

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Simulation study of light transport in laser-processed LYSO:Ce detectors with single-side readout

2017

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A tightly focused pulsed laser beam can locally modify the crystal structure inside the bulk of a scintillator. The result is incorporation of so-called optical barriers with a refractive index different from that of the crystal bulk, that can be used to redirect the scintillation light and control the light spread in the detector. We here systematically study the scintillation light transport in detectors fabricated using the Laser Induced Optical Barrier technique, and objectively compare their potential performance characteristics with those of the two mainstream detector types: monolithic and mechanically pixelated arrays. Among countless optical barrier patterns, we explore barriers arranged in a pixel-like pattern extending all-the-way or half-way through a 20 mm thick LYSO:Ce crystal. We analyze the performance of the detectors coupled to MPPC arrays, in terms of light response functions, flood maps, line profiles, and light collection efficiency. Our results show that laser-processed detectors with both barrier patterns constitute a new detector category with a behavior between that of the two standard detector types. Results show that when the barrier-crystal interface is smooth, no DOI information can be obtained regardless of barrier refractive index (RI). However, with a rough barrier-crystal interface we can extract multiple levels of DOI. Lower barrier RI results in larger light confinement, leading to better transverse resolution. Furthermore we see that the laser-processed crystals have the potential to increase the light collection efficiency, which could lead to improved energy resolution and potentially better timing resolution due to higher signals. For a laser-processed detector with smooth barrier-crystal interfaces the light collection efficiency is simulated to >42%, and for rough interfaces >73%. The corresponding numbers for a monolithic crystal is 39% with polished surfaces, and 71% with rough surfaces, and for a mechanically pixelated array 35% with polished pixel surfaces and 59% with rough surfaces.

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“…The bottleneck for development of a ScPCD for CT has been the need for very fine pixelation, which has not been possible using standard mechanical array fabrication techniques. While conventional microcolumnar and some recent high resolution scintillator developments [29][30][31][32] have not been shown capable of high rate CT applications, there are other recent enabling technologies for fine-pitch scintillator array fabrication using laser beams that have shown promise [33][34][35][36][37][38][39].…”

Section: Introductionmentioning

confidence: 99%

Exploring light confinement in laser-processed LYSO:Ce for photon counting CT application

et al. 2019

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With the goal of developing a low-cost scintillator-based photon counting detector (PCD) with high dose efficiency suitable for CT, the light transport characteristics in LYSO:Ce detectors containing Laser Induced Optical Barriers (LIOB) are simulated. Light confinement and light collection efficiencies (LCE) are studied for a variety of optical barrier patterns and properties (refractive index (RI) and barrier/crystal interface roughness). Up to 80% confinement is achievable with a simple pixel pattern with one barrier wall separating each pixel coupled one-toone to a photodetector (PD) pixel. Confinement is heavily dependent on barrier properties, and rough interfaces and higher RI results in increased cross-talk. Three approaches to enhance performance beyond the basic pattern are explored: 1) Multiple barrier walls separating each crystal pixel. 2) Introduction of long and short range confinement by having multiple crystal pixels per PD pixel. 3) Combination of LIOB and Laser Ablation. 1) Is effective for rough interfaces where confinement can be increased by up to 24% for double compared to single walls. 2) Results in high confinement in the pixel centered on the PD pixel, but lower confinement closer to the PD edge. This feature may be explored to achieve spatial resolution beyond the PD pixel size using light sharing based positioning algorithms. 3) Can increase confinement for smooth interfaces using a smooth ablation in the bottom part of the crystal. A general trend across all configurations is a trade-off between light confinement and LCE. The LCE attainable is found comparable to that for mechanically pixelated arrays. While the confinement achievable with LIOB is always lower compared to a mechanically pixelated array, the former may offer a high level of flexibility in terms of detector design. This, in combination with the possibility to fabricate sub-mm pixels in a cost-effective manner, makes LIOB a promising technology for scintillator-based PCDs.

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Scintillator-based Photon Counting Detector: Is it feasible?

Cited by 5 publications

References 16 publications

Light Spread Manipulation in Scintillators Using Laser Induced Optical Barriers

Light Spread Manipulation in Scintillators Using Laser Induced Optical Barriers

Simulation study of light transport in laser-processed LYSO:Ce detectors with single-side readout

Exploring light confinement in laser-processed LYSO:Ce for photon counting CT application

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