Fabricating high-resolution and high-sensitivity scintillator arrays using Laser Induced Optical Barriers

Sabet, Hamid; Kudrolli, Haris; Singh, Bipin; Nagarkar, Vivek V.

doi:10.1109/nssmic.2012.6551932

Cited by 29 publications

(26 citation statements)

References 3 publications

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“…This barrier thickness is based on experimental observations of barrier thicknesses between approximately 20 and 50 μm in LYSO:Ce that was previously reported (Sabet et al 2012a). The size depends on the laser parameters and delivery optics used during the process, as well as on the crystal material.…”

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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Section: Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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

2017

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“…LYSO:Ce has a monoclinic structure and presents anisotropy in many of its properties [15], [16]. The anisotropy in constant of thermal expansion (CTE) may lead to non-uniform crystal fabrication quality as well as cracking issues [13], [17]. The anisotropy in refractive index (LYSO:Ce has 3 refractive indices) will change the laser focus depth depending on the crystal orientation.…”

Section: Scintillator Processing Using Liobmentioning

confidence: 99%

Light Spread Manipulation in Scintillators Using Laser Induced Optical Barriers

Blackberg

Moebius

Fakhri

et al. 2018

IEEE Trans. Nucl. Sci.

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“…[15][16][17][18] It should be noted that, as opposed to the previously mentioned ablation technique, with the internally focused laser beam, the material is not cut but rather the properties of the material bulk are locally altered. While all the previously reported work are based on utilizing a pulsed laser system with short pulse duration focused inside the scintillation crystal, they differ in the choice of laser system, pulse duration, repetition rate, etc.…”

Section: Introductionmentioning

confidence: 99%

Novel laser-processed CsI:Tl detector for SPECT

et al. 2016

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Purpose: The aim of this work is to demonstrate the feasibility of a novel technique for fabrication of high spatial resolution CsI:Tl scintillation detectors for single photon emission computed tomography systems. Methods: The scintillators are fabricated using laser-induced optical barriers technique to create optical microstructures (or optical barriers) inside the CsI:Tl crystal bulk. The laser-processed CsI:Tl crystals are 3, 5, and 10 mm in thickness. In this work, the authors focus on the simplest pattern of optical barriers in that the barriers are created in the crystal bulk to form pixel-like patterns resembling mechanically pixelated scintillators. The monolithic CsI:Tl scintillator samples are fabricated with optical barrier patterns with 1.0 × 1.0 mm 2 and 0.625 × 0.625 mm 2 pixels. Experiments were conducted to characterize the fabricated arrays in terms of pixel separation and energy resolution. A 4 × 4 array of multipixel photon counter was used to collect the scintillation light in all the experiments. Results: The process yield for fabricating the CsI:Tl arrays is 100% with processing time under 50 min. From the flood maps of the fabricated detectors exposed to 122 keV gammas, peak-to-valley (P/V ) ratios of greater than 2.3 are calculated. The P/V values suggest that regardless of the crystal thickness, the pixels can be resolved. Conclusions:The results suggest that optical barriers can be considered as a robust alternative to mechanically pixelated arrays and can provide high spatial resolution while maintaining the sensitivity in a high-throughput and cost-effective manner. C 2016 American Association of Physicists in Medicine. [http://dx

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Fabricating high-resolution and high-sensitivity scintillator arrays using Laser Induced Optical Barriers

Cited by 29 publications

References 3 publications

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

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

Light Spread Manipulation in Scintillators Using Laser Induced Optical Barriers

Novel laser-processed CsI:Tl detector for SPECT

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