Development of broad-band high-reflectivity multilayer film for positron emission tomography system

Xu, Jianbin; Sun, Quanquan; Wu, Zhihao; Li, Guo; Xie, Siwei; Huang, Qiu; Peng, Qiyu

doi:10.1088/1748-0221/13/09/p09016

Cited by 13 publications

(4 citation statements)

References 35 publications

(35 reference statements)

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“…The high-performance reflectors with light-sharing windows can be "printed" on a scintillator directly with high precision, instead of manually gluing reflective materials on the scintillator. 44 A limit of the four-crystals-to-one-SiPM coupling technology developed in this study is that the four C-type crystals on the corners have no DOI capability, as shown in Figs. 1(c In this study, we adapted the method of homogeneous radiation to establish the transfer functions to convert the measured spot shifts into the DOI measurements.…”

Section: Discussionmentioning

confidence: 98%

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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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Section: Discussionmentioning

confidence: 98%

“…The advanced multilayer dielectric coating technologies is a promising solution to that issue. The high‐performance reflectors with light‐sharing windows can be “printed” on a scintillator directly with high precision, instead of manually gluing reflective materials on the scintillator …”

Section: Discussionmentioning

confidence: 99%

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

et al. 2019

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“…There have been studies on various coating methods for scintillators to make the most of the emitted scintillation photons. However, most methods, such as distributed Bragg reflectors, metal coating, modified photonic crystal structures, and a high reflective film method, require special processing for scintillators, causing increased costs for implementation (Xu et al 2018, Gramuglia et al 2021. Furthermore, these methods have mostly focused on maximizing scintillation light collection without considering Cerenkov photons.…”

Section: Additional Discussionmentioning

confidence: 99%

Colored reflectors to improve coincidence timing resolution of BGO-based time-of-flight PET detectors

Lee,

Cherry,

Kwon

2023

Phys. Med. Biol.

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Time-of-flight (TOF) positron emission tomography (PET) detectors improve the signal-to-noise ratio of PET images by limiting the position of the generation of two 511-keV gamma-rays in space using the arrival time difference between the two photons. Unfortunately, bismuth germanate (BGO), widely used in conventional PET detectors, was limited as a TOF PET scintillator due to the relatively slow decay time of the scintillation photons. However, prompt Cerenkov light in BGO has been identified in addition to scintillation photons. Using Cerenkov photons for timing has significantly improved the coincidence timing resolution (CTR) of BGO. Based on this, further research on improving the CTR for a BGO-based TOF PET system is being actively conducted.Wrapping materials for BGO pixels have primarily employed white reflectors to most efficiently collect scintillation light. White reflectors have customarily been used as reflectors for BGO pixels even after Cerenkov light began to be utilized for timing calculations in pixel-level experiments. However, when the arrival-time differences of the two 511-keV annihilations photons were measured with pure Cerenkov radiators, painting the lateral sides of the radiators black can improve CTR by suppressing the reflection of Cerenkov photons. The use of BGO for TOF PET detectors requires simultaneously minimizing scintillation loss for good energy information and suppressing reflected Cerenkov photons for better timing performance. Thus, reflectors for BGO pixels should be optimized for better timing and energy performance.In this study, colored polytetrafluoroethylene (PTFE) tapes with discontinuous reflectance values at specific wavelengths were applied as a BGO reflector. We hypothesized that CTR could be enhanced by selectively suppressing reflected Cerenkov photons with an optimum colored reflector on the BGO pixel while minimizing scintillation photon loss. CTRs were investigated utilizing white and three colors (yellow, red, and green) PTFE tapes as a reflector. In addition, black-painted PTFE tape and enhanced specular reflector (ESR) film were investigated as reference reflector materials. When 3 × 3 × 20 mm3 BGO pixels were wrapped with the yellow PTFE reflector, the CTR was significantly improved to 365±5 ps from 403±14 ps measured with the conventional white PTFE reflector. Adequate energy information was still obtained with only 4.1% degradation in light collection compared to the white reflector. Colored reflectors show the possibility to further improve CTR for BGO pixels with optimum reflectance design. 

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“…4.1(b). Various photonic structures have been reported with ODB's [40,41,42] defined as those spectral regions for which > 90% for all angles. Here we we adopt the same criterium.…”

Section: Chirped-type Bragg Mirrorsmentioning

confidence: 99%

Optimization of wide-band quasi-omnidirectional 1-D photonic structures

Castillo-Gallardo,

Puente-Díaz,

Ariza-Flores

et al. 2021

Preprint

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We have designed, optimized, fabricated and characterized highly reflective quasi-omnidirectional (angular range of 0 − 60 • ) multilayered structures with a wide spectral range. Two techniques, chirping (a continuous change in thicknesses) and stacking of Bragg-type sub-structures, have been used to enhance the reflectance with minimum thickness for a given pair of refractive indices. Numerical calculations were carried out employing the transfer matrix method and we optimized the design parameters to obtain maximal reflectance averaged over different spectral ranges for all angles. We fabricated some of the optimized structures with porous silicon dielectric multilayers with low refractive contrast and compared their measured optical properties with the calculations. Two chirped structures with thicknesses 21.6 m and 60.4 m, resulting in quasi omnidirectional mirrors with bandwidths of 360 nm and 1800 nm, centered at 1160 nm and 1925 nm respectively have been shown. In addition, we fabricated a stacked sub-Bragg mirror structure with a quasi omnidirectional bandwidth of 1800 nm (centered at 1850 nm) and a thickness of 41.5 m, which is almost two third (in thickness) of the chirped structure. Thus, our techniques allowed us to obtain relatively thin quasi-omnidirectional mirrors with wide bands over different wavelength ranges. Our analysis techniques can be used for the optimization of the reflectance not only in multilayered PS systems with different refractive index contrasts but also for systems with other types of materials with low refractive index contrast. The present study could also be useful for obtaining omnidirectional dielectric mirrors in large spectral regions using different materials, flat focusing reflectors, thermal regulators, or, if defects are included, as filters or remote chemical/biosensors with a wide angular independent response.

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Development of broad-band high-reflectivity multilayer film for positron emission tomography system

Cited by 13 publications

References 35 publications

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

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

Colored reflectors to improve coincidence timing resolution of BGO-based time-of-flight PET detectors

Optimization of wide-band quasi-omnidirectional 1-D photonic structures

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