Design study of a PET detector with 0.5 mm crystal pitch for high-resolution preclinical imaging

Zhang, Xi; Yu, Hongsen; Xie, Qiangqiang; Xie, Siwei; Ye, Baihezi; Guo, Minghao; Zhao, Zhixiang; Huang, Qiu; Xu, Jianfeng; Peng, Qiyu

doi:10.1088/1361-6560/ac0b82

Cited by 10 publications

(7 citation statements)

References 32 publications

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“…All crystals could be clearly distinguished, as the size of the LYSO array was about 1 mm smaller than that of the SiPM array on each side, and a DOI resolution ∼2.0 mm was achieved. Zhang et al 40 optimized a high-resolution PET detector with a LYSO crystal of 0.5 × 0.5 × 6.25 mm 3 size and performed initial image studies with a prototype PET scanner consisting of 12 optimized detectors. However, for all the prototype small animal PET scanners developed so far with spatial resolution approaching 0.5 mm, the sensitivity was still much lower than current commercial small animal PET scanners.Lai et al 41 performed Monte Carlo simulations to design small animal PET scanners that can achieve ∼0.5 mm spatial resolution and high sensitivity with different scanner geometries and crystal lengths.…”

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Ultra‐high‐resolution depth‐encoding small animal PET detectors: Using GAGG and LYSO crystal arrays

et al. 2022

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Purpose Small animal positron emission tomography (PET) scanners are widely used in current biomedical research. The study aimed to develop high‐efficiency and ultra‐high‐resolution detectors that could be used to develop a small animal PET scanner with high sensitivity and spatial resolution approaching to its physical limit. Methods Four crystal arrays were fabricated and measured in this study. Crystal arrays 1 and 2 consisted of 38 × 38 gadolinium aluminum gallium garnet (GAGG) and lutetium–yttrium oxyorthosilicate (LYSO) crystals of 0.4 × 0.4 × 20 mm3 size. Crystal array 3 consisted of 16 × 16 GAGG crystals of 0.3 × 0.3 × 20 mm3 size, and crystal array 4 consisted of 24 × 24 LYSO crystals 0.3 × 0.3 × 20 mm3 in size. The crystal arrays were dual‐ended readouts using 8 × 8 silicon photomultiplier (SiPM) arrays of 2 × 2 mm2 pixel area. The SiPM array was readout using a signal multiplexing circuit to convert the 64 output signals into four position‐encoding signals. The performances of the four detectors in terms of flood histogram, energy resolution, depth of interaction (DOI) resolution, and timing resolution were measured. Results The GAGG detectors provided better flood histograms, ∼30% higher photopeak amplitude, ∼20% higher energy resolution, ∼12% worse DOI resolution, and ∼15% worse timing resolution compared with LYSO detectors of the same crystal size. These four detectors provided DOI resolutions of <2 mm, energy resolutions of <22%, and timing resolutions of <1.6 ns. All crystals of 0.4 × 0.4 × 20 mm3 and 0.3 × 0.3 × 20 mm3 could be clearly resolved if the crystal array was 1 mm smaller in the four sides than that in the SiPM array. Conclusions High DOI resolution PET detectors were developed using both GAGG and LYSO arrays with crystal sizes of 0.3 and 0.4 mm, respectively, and a length of 20 mm. The detectors can be used in the future to develop small animal PET scanners, especially dedicated mouse imaging PET scanners, which can simultaneously achieve high sensitivity and ultra‐high spatial resolution.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Ultra‐high‐resolution depth‐encoding small animal PET detectors: Using GAGG and LYSO crystal arrays

et al. 2022

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“…where S in,i is the energy signal read from the ith SiPM and N th is the preset threshold. Flood histograms calculated using threshold values ranging from 1% to 3.5% were assessed to determine the best threshold value [44].…”

Section: Discussionmentioning

confidence: 99%

“…When the threshold was set higher than 2%, the peak-to-valley ratio remained almost constant for both layers. Based on our previous experience [44], the optimal threshold was 2%, because higher thresholds cause distortion of the signal and decoding specks. The average peak-to-valley ratios at a threshold value of 2% for top and bottom crystals were 3.56 and 4.73, respectively.…”

Section: Flood Histograms Of Toray Reflectorsmentioning

confidence: 99%

Development and Evaluation of a Dual-Layer-Offset PET Detector Constructed with Different Reflectors

et al. 2022

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Dual-layer-offset or multi-layer-offset design of a PET detector can improve spatial resolution while maintaining high sensitivity. In this study, three dual-layer-offset LYSO detectors with three different reflectors (ESR, Toray, and BaSO4) were developed. The top layer consisted of a 17 × 17 array of crystals 1 × 1 × 6.5 mm3 in size and the bottom layer consisted of an 18 × 18 array of crystals 1 × 1 × 9.5 mm3 in size. Neither light guides nor optical glue were used between the two layers of crystals. A custom-designed electronics system, composed of a 6 × 6 SiPM array, two FPC cables, and a custom-designed data processing module, was used to read out signals. An optimized interaction-decoding algorithm using the center of gravity to determine the position and threshold of analog signals for timing methods was applied to generate decoding flood histograms. The detector performances, in terms of peak to valley ratio of the flood histograms and energy resolutions, were calculated and compared. The dual-layer-offset PET detector constructed with BaSO4 reflectors performed much better than the other two reflectors in both crystal identification and energy resolution. The average peak-to-valley ratio and the energy resolution were approximately 7 and 11%, respectively. In addition, the crystals in the bottom layer showed better performance at crystal identification than those in the top layer. This study can act as a reference providing guidance in choosing scintillator reflectors for multi-layer dedicated DOI detectors designed for small-animal PET imaging.

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“…27 In this work, theoretical calculations and experimental measurements were performed to compare the quality of the flood histograms generated by the dual-ended readout PET detectors obtained with the AM and EWM methods. Metrics such as contrast 28 and peak-to-valley ratio (PVR) 29,30 of the one-dimensional (1D) profiles across flood histograms and ratio of the width of the flood histograms of individual crystals to the distance between the locations of neighboring crystals in the flood histogram 31,32 were considered to compare the quality of the obtained flood histograms between the above two methods.…”

Section: Introductionmentioning

confidence: 99%

Technical note: Comparison of arithmetic mean and energy‐weighted mean flood histogram generation methods for dual‐ended readout positron emission tomography detectors

et al. 2022

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Purpose Dual‐ended readout pixelated scintillator array detectors can provide a suitable crystal resolvability and satisfactory depth of interaction (DOI), energy, and timing resolutions. Usually, the flood histogram measured by one‐sided readout is depth dependent, and the flood histogram quality degrades as the distance between the interaction site and photodetector increases. Information measured by two photodetectors must be combined to obtain an improved flood histogram yielding a better PET scanner spatial resolution. Methods Two flood histogram generation algorithms for dual‐ended readout of pixelated scintillator array detectors were compared by theoretical calculations and experimental measurements. The first algorithm is the arithmetic mean (AM) algorithm, which assigns the same weight to the flood histograms measured by photodetectors 1 and 2. The second algorithm is the energy‐weighted mean (EWM) algorithm, which assigns each flood histogram a certain weight proportional to the energy measured by the photodetector. Theoretical equations were derived to determine the quality of the flood histograms obtained with these two algorithms. Experimental measurements were performed with an 18 × 18 lutetium–yttrium oxyorthosilicate (LYSO) array with a crystal size of 0.62 × 0.62 × 20 mm3 read out by two multi‐anode photomultiplier tubes at both ends. Flood histograms of the whole array and five specific depths were compared between the above two algorithms. Results The theoretical results indicated that the flood histograms obtained with the EWM method matched those obtained with the AM method at the middle detector depth and were better at other detector depths when the distance (S) between the locations of the same crystal in the flood histograms measured by photodetectors 1 and 2 reached 0. The advantage of the EWM method decreased with increasing S value since the crystal position in the flood histogram obtained with the EWM method varies with the depth when S does not equal 0. The advantage of the EWM method decreased with increasing S value. The experimental results generally agreed with the theoretical predictions. Compared to the AM method, the EWM method provided a similar flood histogram at a depth of 10 mm but generated a better flood histogram at depths of 2 and 18 mm. Although an inverse correlation between Q (a quality factor representing the advantage of the EWM method) and S was observed, the variation in Q given the same S value was high. The average Q value at the same S still agreed with the theoretical predictions. Conclusions Theoretical equations were derived, and experimental measurements were performed to compare two flood histogram generation algorithms for dual‐ended readout PET detectors. The results indicated that the EWM method based on inverse variance weighting theory could provide better flood histograms than those provided by the AM method.

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Design study of a PET detector with 0.5 mm crystal pitch for high-resolution preclinical imaging

Cited by 10 publications

References 32 publications

Ultra‐high‐resolution depth‐encoding small animal PET detectors: Using GAGG and LYSO crystal arrays

Ultra‐high‐resolution depth‐encoding small animal PET detectors: Using GAGG and LYSO crystal arrays

Development and Evaluation of a Dual-Layer-Offset PET Detector Constructed with Different Reflectors

Technical note: Comparison of arithmetic mean and energy‐weighted mean flood histogram generation methods for dual‐ended readout positron emission tomography detectors

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