Efficient system modeling for a small animal PET scanner with tapered DOI detectors

Zhang, Mengxi; Zhou, Jian; Yang, Yongfeng; Rodríguez‐Villafuerte, M.; Qi, Jinyi

doi:10.1088/0031-9155/61/2/461

Cited by 9 publications

(8 citation statements)

References 28 publications

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“…To reduce the data size with DOIs, a virtual ring detector geometry has been utilized, in which the lines of response (LORs) of DOI bins are projected onto the front DOI bins (Yamaya et al 2002, Yamaya et al 2008). Zhang et al developed a small animal PET scanner with three DOI layers and successfully utilized a virtual detector containing gaps representing the unmeasured area between the two detector panels (Zhang et al 2015). Here, the optimal resolution of virtual detector was slightly higher than the half of real crystal size.…”

Section: Introductionmentioning

confidence: 99%

A novel depth-of-interaction rebinning strategy for ultrahigh resolution PET

et al. 2018

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Small animal positron emission tomography (PET) imaging often requires high resolution (∼few hundred microns) to enable accurate quantitation in small structures such as animal brains. Recently, we have developed a prototype ultrahigh resolution depth-of-interaction (DOI) PET system that uses CdZnTe detectors with a detector pixel size of 350 μm and eight DOI layers with a 250 μm depth resolution. Due to the large number of line-of-response (LOR) combinations of DOIs, the system matrix for reconstruction is 64 times larger than that without DOI. While a high resolution virtual ring geometry can be employed to simplify the system matrix and create a sinogram, the LORs in such a sinogram tend to be sparse and irregular, leading to potential degradation of the reconstructed image quality. In this paper, we propose a novel high resolution sinogram rebinning method in which a uniform sub-sampling DOI strategy is employed. However, even with the high resolution rebinning strategy, the reconstructed image tends to be very noisy due to insufficient photon counts in many high resolution sinogram pixels. To reduce noise effects, we developed a penalized maximum likelihood reconstruction framework with the Poisson log-likelihood and a non-convex total variation penalty. Here, an ordered subsets separable quadratic surrogate and alternating direction method of multipliers are utilized to solve the optimization. To evaluate the performance of the proposed sub-sampling method and the penalized maximum likelihood reconstruction technique, we perform simulations and preliminary point source experiments. By comparing the reconstructed images and profiles based on sinograms without DOI, with rebinned DOI and with sub-sampled DOI, we demonstrate that the proposed method with sub-sampled DOIs can significantly improve the image quality with lower dose and yield a high resolution of <300 μm.

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Section: Introductionmentioning

confidence: 99%

A novel depth-of-interaction rebinning strategy for ultrahigh resolution PET

et al. 2018

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“…Although the Prism‐PET 1.5 mm (with 2 mm DOI resolution) uses larger crystal elements, it provided better spatial resolution than the Prism‐PET 1 mm (with 4 mm DOI resolution) especially for regions near the edge of the transaxial FOV, suggesting that accurate DOI localization is indispensable for compact and conformal PET scanners to achieve uniform high spatial resolution. One important consideration is that the number of LORs increases quadratically with the number of DOI layers which may lead to higher computational costs for DOI‐based image reconstruction 94,95 . One solution is to perform DOI‐rebinning in list‐mode followed by a conventional non‐DOI image reconstruction.…”

Section: Discussionmentioning

confidence: 99%

“…One important consideration is that the number of LORs increases quadratically with the number of DOI layers which may lead to higher computational costs for DOI-based image reconstruction. 94,95 One solution is to perform DOI-rebinning in list-mode followed by a conventional non-DOI image reconstruction. Thus, although continuous DOI was simulated for the Prism-PET scanners, the image reconstruction time remained similar to that of non-DOI scanners.…”

Section: Discussionmentioning

confidence: 99%

High‐resolution and high‐sensitivity PET for quantitative molecular imaging of the monoaminergic nuclei: A GATE simulation study

et al. 2022

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Purpose Quantitative in vivo molecular imaging of fine brain structures requires high‐spatial resolution and high‐sensitivity. Positron emission tomography (PET) is an attractive candidate to introduce molecular imaging into standard clinical care due to its highly targeted and versatile imaging capabilities based on the radiotracer being used. However, PET suffers from relatively poor spatial resolution compared to other clinical imaging modalities, which limits its ability to accurately quantify radiotracer uptake in brain regions and nuclei smaller than 3 mm in diameter. Here we introduce a new practical and cost‐effective high‐resolution and high‐sensitivity brain‐dedicated PET scanner, using our depth‐encoding Prism‐PET detector modules arranged in a conformal decagon geometry, to substantially reduce the partial volume effect and enable accurate radiotracer uptake quantification in small subcortical nuclei. Methods Two Prism‐PET brain scanner setups were proposed based on our 4‐to‐1 and 9‐to‐1 coupling of scintillators to readout pixels using 1.5×1.5×20$1.5 \times 1.5 \times 20$ mm3 and 0.987×0.987×20$0.987 \times 0.987 \times 20$ mm3 crystal columns, respectively. Monte Carlo simulations of our Prism‐PET scanners, Siemens Biograph Vision, and United Imaging EXPLORER were performed using Geant4 application for tomographic emission (GATE). National Electrical Manufacturers Association (NEMA) standard was followed for the evaluation of spatial resolution, sensitivity, and count‐rate performance. An ultra‐micro hot spot phantom was simulated for assessing image quality. A modified Zubal brain phantom was utilized for radiotracer imaging simulations of 5‐HT1A receptors, which are abundant in the raphe nuclei (RN), and norepinephrine transporters, which are highly concentrated in the bilateral locus coeruleus (LC). Results The Prism‐PET brain scanner with 1.5 mm crystals is superior to that with 1 mm crystals as the former offers better depth‐of‐interaction (DOI) resolution, which is key to realizing compact and conformal PET scanner geometries. We achieved uniform 1.3 mm full‐width‐at‐half‐maximum (FWHM) spatial resolutions across the entire transaxial field‐of‐view (FOV), a NEMA sensitivity of 52.1 kcps/MBq, and a peak noise equivalent count rate (NECR) of 957.8 kcps at 25.2 kBq/mL using 450–650 keV energy window. Hot spot phantom results demonstrate that our scanner can resolve regions as small as 1.35 mm in diameter at both center and 10 cm away from the center of the transaixal FOV. Both 5‐HT1A receptor and norepinephrine transporter brain simulations prove that our Prism‐PET scanner enables accurate quantification of radiotracer uptake in small brain regions, with a 1.8‐fold and 2.6‐fold improvement in the dorsal RN as well as a 3.2‐fold and 4.4‐fold improvement in the bilateral LC compared to the Biograph Vision and EXPLORER, respectively. Conclusions Based on our simulation results, the proposed high‐resolution and high‐sensitivity Prism‐PET brain scanner is a promising cost‐effective candidate ...

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“…Furthermore, using cuboidal detectors with smaller ring diameters results in gaps between detector modules, causing a reduction in both count rate and sensitivity. To address this challenge, trapezoidal pixelated crystals have been introduced, effectively lling these gaps with sensitive materials [9][10][11][12].…”

Section: Introductionmentioning

confidence: 99%

Comparing Pixelated and Slat-Based Monolithic Tapered MicroPET Scanners in Single-Layer and Phoswich Configurations

Sadremomtaz,

Taherparvar,

saber

2023

Preprint

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As technology advances, there is a growing demand for enhancing the performance of small animal PET scanners. In pursuit of this objective, innovative designs, including tapered pixelated and pseudo-monolithic configurations, have been introduced. This research explores and compares tapered pixelated microPET systems and tapered pseudo-monolithic systems, both in single-layer and phoswich configurations. The pseudo-monolithic detectors were simulated with different slat sizes and orientations, along y and z direction. The focus was on critical parameters, including sensitivity, noise equivalent count rate, scatter fraction, and energy resolution, to assess these systems. The findings emphasize the advantages of phoswich systems in respect to their single-layer counterparts. For pseudo-monolithic systems, while the configuration with slats oriented in the z-direction demonstrate substantial improvements in system performance, the alternative pseudo-monolithic design with slats oriented in the y-direction yielded lower performance, indicating that the orientation of slats in pseudo-monolithic scanners can notably impact system performance.

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Efficient system modeling for a small animal PET scanner with tapered DOI detectors

Cited by 9 publications

References 28 publications

A novel depth-of-interaction rebinning strategy for ultrahigh resolution PET

A novel depth-of-interaction rebinning strategy for ultrahigh resolution PET

High‐resolution and high‐sensitivity PET for quantitative molecular imaging of the monoaminergic nuclei: A GATE simulation study

Comparing Pixelated and Slat-Based Monolithic Tapered MicroPET Scanners in Single-Layer and Phoswich Configurations

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