Performance of a SiPM based semi-monolithic scintillator PET detector

Zhang, Xianming; Wang, Xiaohui; Ren, Na; Kuang, Zhonghua; Deng, Xinhan; Fu, Xin; Wu, San; Sang, Ziru; Hu, Zhanli; Liang, Dong; Liu, Xin; Zheng, Hairong; Yang, Yongfeng

doi:10.1088/1361-6560/aa898a

Cited by 29 publications

(23 citation statements)

References 38 publications

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“…The measurements were performed using an experimental setup similar to the one shown in our previous publication . The semi‐monolithic detector was irradiated at a series of given (y, z) positions with a narrow gamma ray beam obtained with electronic collimation by using a 0.25 mm diameter 22 Na point source and a reference detector consisting of a single 1 × 1 × 20 mm 3 LYSO crystal and a 3 × 3 mm 2 SiPM pixel.…”

Section: Methodsmentioning

confidence: 99%

“…For PET detectors using the dual‐ended readout of pixelated crystal arrays, it was demonstrated by several works that a rough crystal surface provided better DOI resolution but inferior crystal identification and energy resolution. Monolithic scintillator PET detectors using polished crystal surface with black paint, white paint, no reflector, and with enhanced specular reflector (ESR) were measured in previous works . As compared to monolithic scintillator detector using more reflective white paint and the ESR reflector, detectors using black paint reduced the edge effect and improved the spatial and DOI resolution, but degraded the energy and timing resolution.…”

Section: Introductionmentioning

confidence: 99%

“…Later, the performance of a semi‐monolithic scintillator detector consisting of a single scintillator slab of 20 × 2 × 10 mm 3 and a multichannel photomultiplier tube was measured . In our previous work, the feasibility of semi‐monolithic scintillator detector was demonstrated by using a short semi‐monolithic detector consisting of 11 lutetium‐yttrium oxyorthosilicate (LYSO) slice of 1 mm thick single‐ended readout by a 4 × 4 silicon photomultiplier (SiPM) array. A longer rectangular semi‐monolithic scintillator detector has the advantage of significantly reducing the edge effect as compared to short semi‐monolithic and monolithic scintillator detectors.…”

Section: Introductionmentioning

confidence: 99%

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Performance of long rectangular semi‐monolithic scintillator PET detectors

et al. 2019

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Purpose: High-sensitivity and high-resolution depth-encoding positron emission tomography (PET) detectors are required to simultaneously improve the sensitivity and spatial resolution of a PET scanner so that the quantitative accuracy of PET studies can be improved. The semi-monolithic scintillator PET detector has the advantage of measuring the depth of interaction with single-ended readout as compared to the traditional pixelated scintillator detector, and significantly reducing the edge effect that deteriorates the spatial resolution at edges of the detector as compared to the monolithic scintillator detector if a long rectangular semi-monolithic detector is used. In this work, depth-encoding PET detector modules were built by using long rectangular semi-monolithic scintillators and single-ended readout by silicon photomultiplier (SiPM) arrays. The performance of the detector modules was measured. Methods: The rectangular semi-monolithic scintillator detector has an outside dimension of 11.6 9 37.6 9 10 mm 3 and consists of 11 polished lutetium-yttrium oxyorthosilicate (LYSO) slices measuring 1 9 37.6 9 10 mm 3 . The enhanced specular reflector (ESR) was glued on both crosssectional surfaces of each crystal slice. For the face opposite to the SiPM array and the two end faces of the detectors, surface treatments with and without black paint were implemented for performance comparison. The bottom face of the semi-monolithic detector was coupled to a 4 9 12 SiPM array that was grouped along rows and columns separately into 16 signals. The four row signals were used to identify the slices, and the 12 column signals were used to estimate the y (monolithic direction) and z (depth direction) interaction positions. The detector was irradiated at multiple positions with a collimated 511 keV gamma beam. The collimated beam was obtained with electronic collimation by using a 22 Na point source and a reference detector. The estimated width of the gamma beam is around 0.5 mm. The flood histogram for crystal slices was measured by using the center of gravity (COG) method. The COG method and the squared COG method were used for y position estimation. The standard deviation of the column signals, the ratio of maximum to the sum of the column signals, and the sum of squared column signals were used for z position estimation. Results: All slices were clearly resolved from the measured flood histograms for both detectors with different crystal surface treatments. The estimated y positions roughly linearly change with the true positions at the middle of the detector until~5 mm from both ends of the detector. The y and z spatial resolutions of the detectors were estimated for all middle positions located more than 5 mm from both ends of the detector. The squared COG method provides better y position resolution than the COG method. The three z estimation methods provide similar depth of interaction (DOI) resolution. Surface treatment with black paint significantly improves both y and z position resolution but degrades the energy an...

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Section: Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Performance of long rectangular semi‐monolithic scintillator PET detectors

et al. 2019

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“…The multiple scattering events were rejected using a method commonly used in calculating MAE of the position decoding of PET detectors. 29,43 Windows at 40% of the peak values of the event count distributions were applied. Only the events inside the windows were used in the MEA calculation.…”

Section: B2 Accuracy Of Doi Measurementmentioning

confidence: 99%

“…Moreover, their DOI capabilities are limited by the number of layers. Another method is to use the quasi-monolithic crystals [26][27][28][29] or the monolithic crystals [30][31][32][33] to construct the DOI detectors. That method is very attractive and promising because of the advantages in filling factor, cost, and the potential performance.…”

Section: Introductionmentioning

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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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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Timing evaluation of a PET detector block based on semi‐monolithic LYSO crystals

et al. 2021

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Purpose: Detectors for positron emission tomography (PET) typically use two types of scintillation crystals, pixelated or monolithic. A variant of these types of scintillators are the so-called semi-monolithic crystals. They consist of a monolithic crystal segmented in one direction in pieces called slabs. These scintillators have the potential to successfully combine the benefits of pixelated and monolithic configurations, providing good timing and spatial resolutions as well as the capacity to decode the depth of interaction (DOI) information. In this work, the timing performance of a detector based on semi-monolithic crystals was studied in depth. The energy response was also evaluated. Methods: The semi-monolithic detector consists of 1 × 24 LYSO slabs of 25.4 × 12 × 0.95 mm 3 each. The bottom surface of the slabs is coupled to an array of 8 × 8 silicon photomultipliers (SiPMs) of 3 × 3 mm 2 active area, 50 μm cell size and 3.2 mm pitch. The 64 output signals were independently readout by the TOFPET2 ASIC. In order to achieve the best coincidence time resolution (CTR), four different time walk corrections were tested. Additional work investigated the best method of combining the timestamps belonging to the same event.Results: The resolvability of the slabs in the measured flood maps improves with the thickness of a light guide placed in between the scintillators and photosensors. The energy resolution does not change significantly with values as good as 13.7%. Regarding the CTR, values of 335.8, 363, 369.8, and 402.5 ps have been obtained for the whole detector for no light guide, 0.5, 1.0, and 1.5 mm thickness light guide cases, respectively. These values further improve to 276.1, 302.6, 305.6 and 336.2 ps, respectively, when energy-weighted averaging of timestamps is applied. Conclusions: We have shown both an excellent timing resolution and good energy resolution for a PET detector based on semi-monolithic crystals. The use of light guides of different thicknesses does not significantly affect the energy resolution of the whole detector, but the timing capabilities slightly worsen with the increasing thickness of the light guide.

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Performance of a SiPM based semi-monolithic scintillator PET detector

Cited by 29 publications

References 38 publications

Performance of long rectangular semi‐monolithic scintillator PET detectors

Performance of long rectangular semi‐monolithic scintillator PET detectors

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

Timing evaluation of a PET detector block based on semi‐monolithic LYSO crystals

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