National Electrical Manufacturers Association NU Research Articles

Performance evaluation of a small-animal PET scanner with 213 mm axis using NEMA NU 4-2008.

Long-axis positron emission tomography (PET) has emerged as one of the recent research directions in PET due to its ability to significantly enhance sensitivity and counting performance for low-dose imaging, rapid imaging, and whole-body dynamicimaging. The PET system presented in this study is a long-axis animal PET based on lutetium-yttrium orthosilicate and silicon photomultiplier, designed for whole-body imaging in rats. It features a diameter of 143 mm and an axial length of 213.3 mm. This study evaluated the performance of this PET system in accordance with the National Electrical Manufacturers Association (NEMA) NU 4-2008standards. The performance evaluation was conducted according to the NEMA NU 4-2008 standards in terms of spatial resolution, sensitivity, counting rate performance, scatter fraction (SF) and image quality. In addition, a rat imaging study was conducted to assess the imaging capability of this PETsystem. The average energy resolution of the PET system was 12.87%, the average coincidence timing resolution was 751 ps. The FWHM of spatial resolution reconstructed by filtered back projection and 3D-OSEM-PSF algorithm at 5 mm radial offset from the axial center were 1.65 and 0.88 mm. The peak absolute sensitivity measured by a point source at the center of the field of view was evaluated as 6.71% (361-661keV) and 10.31% (250-750 keV). For the mouse-like phantom, the SF was 11.0% and the peak noise equivalent counting rate (NECR) was 1193 kcps at 94.2 MBq (2.54 mCi). For the rat-like phantom, the SF was 26.8% and the NECR was 682.5 kcps at 78.6 MBq (2.12 mCi). The performance measurement results demonstrate that this PET system exhibits high sensitivity and count rate performance, making it potential for high-quality whole-body dynamic imaging ofrats.

Performance evaluation of the 3D-ring cadmium–zinc–telluride (CZT) StarGuide system according to the NEMA NU 1-2018 standard

BackgroundThe application of semi-conductor detectors such as cadmium–zinc–telluride (CZT) in nuclear medicine improves extrinsic energy resolution and count sensitivity due to the direct conversion of gamma photons into electric signals. A 3D-ring pixelated CZT system named StarGuide was recently developed and implemented by GE HealthCare for SPECT acquisition. The system consists of 12 detector columns with seven modules of 16 × 16 CZT pixelated crystals, each with an integrated parallel-hole tungsten collimator. The axial coverage is 27.5 cm. The detector thickness is 7.25 mm, which allows acquisitions in the energy range [40–279] keV. Since there is currently no performance characterization specific to 3D-ring CZT SPECT systems, the National Electrical Manufacturers Association (NEMA) NU 1-2018 clinical standard can be tailored to these cameras. The aim of this study was to evaluate the performance of the SPECT/CT StarGuide system according to the NEMA NU 1-2018 clinical standard specifically adapted to characterize the new 3D-ring CZT.ResultsDue to the integrated collimator, the system geometry and the pixelated nature of the detector, some NEMA tests have been adapted to the features of the system. The extrinsic measured energy resolution was about 5–6% for the tested isotopes (99mTc, 123I and 57Co); the maximum count rate was 760 kcps and the observed count rate at 20% loss was 917 kcps. The system spatial resolution in air extrapolated at 10 cm with 99mTc was 7.2 mm, while the SPECT spatial resolutions with scatter were 4.2, 3.7 and 3.6 mm in a central, radial and tangential direction respectively. Single head sensitivity value for 99mTc was 97 cps/MBq; with 12 detector columns, the system volumetric sensitivity reached 520 kcps MBq−1 cc−1.ConclusionsThe performance tests of the StarGuide can be performed according to the NEMA NU 1-2018 standard with some adaptations. The system has shown promising results, particularly in terms of energy resolution, spatial resolution and volumetric sensitivity, potentially leading to higher quality clinical images.

Monte Carlo simulation of two Siemens Biograph PET/CT system using GATE: Image quality performance

The utilization of Monte Carlo simulation is a highly effective method in advancing research within the field of nuclear medicine. An important software tool for simulating and modeling cutting-edge systems for Positron Emission Tomography (PET) is the Geant4 Application for Tomographic Emission (GATE). This research specifically concentrates on two Siemens PET scanners: the Siemens Biograph True point (True V) and Siemens Biograph mcT 20 excel. Our primary objective was to validate the GATE V8.2 simulation in accordance with the NEMA (National Electrical Manufacturers Association) NU 2-2018 protocol, using a parallel computing platform on a local cluster of computers. This cluster was managed by the open-source package TORQUE version 6.1.0, which is based on the original wrapper PBS.The results of this validation process for the Siemens Biograph True point (True V) scanner were highly promising. The scatter fraction (SF), peak noise equivalent count rate (NECR), and sensitivity all demonstrated a remarkable level of agreement, with deviations within 10.02%, 5.4%, and 1.57%, respectively. Additionally, the spatial resolution was found to deviate by less than 0.59 mm. Image evaluations demonstrate high-quality results for both Siemens Biograph True point (True V) and Siemens Biograph mcT 20 excel scanners, validating the GATE simulation. The study on acquisition time provides insights into optimizing computing simulation time.This research demonstrates the effectiveness of Monte Carlo simulation, facilitated by GATE, in accurately modeling advanced PET systems. The validation results affirm the reliability of GATE V8.2 in accordance with NEMA standards for the Siemens Biograph True point (True V) scanner. The high-quality images obtained from GATE-validated scanners underscore the potential of this simulation approach in advancing nuclear medicine research. Additionally, the study on acquisition time provides valuable considerations for optimizing simulation efficiency.

Performance Evaluation of the uMI Panorama PET/CT System in Accordance with the National Electrical Manufacturers Association NU 2-2018 Standard.

The uMI Panorama is a novel PET/CT system using silicon photomultiplier and application-specific integrated circuit technologies and providing exceptional spatial and time-of-flight (TOF) resolutions. The objective of this study was to assess the physical performance of the uMI Panorama in accordance with the National Electrical Manufacturers Association (NEMA) NU 2-2018 standard. Methods: Spatial resolution, sensitivity, count rate performance, accuracy, image quality, and TOF resolution were evaluated in accordance with the guidelines outlined in the NEMA NU 2-2018 standard. Energy resolution was determined using the same dataset acquired for the count rate performance evaluation. Images from a Hoffman brain phantom, a mini-Derenzo phantom, and 3 patient studies were evaluated to demonstrate system performance. Results: The transaxial spatial resolution at full width at half maximum was measured as 2.88 mm with a 1-cm offset from the center axial field of view. The sensitivity at the center axial field of view was 20.1 kcps/MBq. At an activity concentration of 73.0 kBq/mL, the peak noise-equivalent count rate (NECR) reached 576 kcps with a scatter fraction of approximately 33.2%. For activity concentrations at or below the peak NECR, the maximum relative count rate error among all slices remained consistently below 3%. When assessed using the NEMA image quality phantom, overall image contrast recovery ranged from 63.2% to 88.4%, whereas background variability ranged from 4.2% to 1.1%. TOF resolution was 189 ps at 5.3 kBq/mL and was consistently lower than 200 ps for activity concentrations at or below the peak NECR. The patient studies demonstrated that scans at 2 min/bed produced images characterized by low noise and high contrast. Clear delineation of nuclei, spinal cords, and other substructures of the brain was observed in the brain PET images. Conclusion: uMI Panorama, the world's first commercial PET system with sub-200-ps TOF resolution, demonstrated fine spatial and fast TOF resolutions, robust count rate performance, and high quantification accuracy across a wide range of activity levels. This advanced technology offers enhanced diagnostic capability for detecting small and low-contrast lesions while showing promising potential under high-count-rate imaging scenarios.

SAFIR-I: first NEMA NU 4-2008-based performance characterization

BackgroundSmall Animal Fast Insert for MRI detector I (SAFIR-I) is a novel Positron Emission Tomography insert for a 7T\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$7\\,\\hbox {T}$$\\end{document} Bruker BioSpec 70/30 Ultra Shield Refrigerated Magnetic Resonance Imaging (MRI) system. It facilitates truly simultaneous quantitative imaging in mice and rats at injected activities as high as 500MBq\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$500\\,\\hbox {MBq}$$\\end{document}. Exploitation of the resulting high count rates enables quick image formation at few seconds per frame. In this investigation, key performance parameters of SAFIR-I have been determined according to the evaluations outlined in the National Electrical Manufacturers Association (NEMA) Standards Publication NU 4-2008 (NEMA-NU4) protocol.ResultsUsing an energy window of 391 to 601keV\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$601\\,\\hbox {keV}$$\\end{document} and a Coincidence Timing Window of 500ps\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$500\\,\\hbox {ps}$$\\end{document}, the following performance was observed: The average spatial resolution at 5mm\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$5\\,\\hbox {mm}$$\\end{document} radial offset (Full Width at Half Maximum) is 2.54mm\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$2.54\\,\\hbox {mm}$$\\end{document} when using Filtered Backprojection, 3D Reprojection reconstruction. For the mouse- and rat-like phantoms, the maximal Noise-Equivalent Count Rates (NECRs) are 1368kcps\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$1368\\,\\hbox {kcps}$$\\end{document} at the highest tested average effective concentration of 14.7MBqcc-1\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$14.7\\,\\hbox {MBq}\\,\\hbox {cc}^{-1}$$\\end{document}, and 713kcps\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$713\\,\\hbox {kcps}$$\\end{document} at the highest tested average effective concentration of 1.72MBqcc-1\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$1.72\\,\\hbox {MBq}\\,\\hbox {cc}^{-1}$$\\end{document}, respectively. The NECR peak is not yet reached for either of these cases. The peak sensitivity is 1.46%\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$1.46\\,\\%$$\\end{document}. The Image Quality phantom uniformity standard deviation is 4.8%\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$4.8\\,\\%$$\\end{document}. The Recovery Coefficient for the 5mm\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$5\\,\\hbox {mm}$$\\end{document} rod is (1.08±0.10)\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$(1.08 \\pm 0.10)$$\\end{document}. The Spill-Over Ratios are (0.22±0.03)\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$(0.22 \\pm 0.03)$$\\end{document} and (0.22±0.02)\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$(0.22 \\pm 0.02)$$\\end{document}, for the water- and air-filled cylinder, respectively. An accuracy of 4.3%\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$4.3\\,\\%$$\\end{document} was achieved for the quantitative calibration of reconstructed voxel values.ConclusionsThe measured performance parameters indicate that the various design goals have been achieved. SAFIR-I offers excellent performance, especially at the high activities it was designed for. This facilitates planned experiments with fast tracer kinetics in small animals. Ways to potentially improve performance can still be explored. Simultaneously, further performance gains can be expected for a forthcoming insert featuring 2.7 times longer axial coverage named Small Animal Fast Insert for MRI detector II (SAFIR-II).

Performance Characteristics of a New-Generation Digital Bismuth Germanium Oxide PET/CT System, Omni Legend 32, According to NEMA NU 2-2018 Standards.

The Omni Legend 32 PET/CT system features silicon photomultiplier (SiPM)-based detectors with bismuth germanium oxide crystals and a 32-cm axial field of view (FOV). The present study aimed to determine the performance characteristics of the Omni Legend 32 PET/CT system according to National Electrical Manufacturers Association (NEMA) NU 2-2018 standards. Methods: The PET component of this system comprises 22 detector modules; each module contains 24 detector blocks with 72 bismuth germanium oxide crystals with a volume of 4.1 × 4.1 × 30 mm coupled to 18 SiPM devices with a 6 × 6 mm area, resulting in an axial FOV of 32 cm. The spatial resolution, sensitivity, count rate performance, and image quality delivered by PET were evaluated using the NEMA NU 2-2018 standard. PET images of 2 patients were evaluated to get a visual first impression of the Omni Legend 32 PET/CT system together with Precision DL. Results: The average spatial resolution at 1, 10, and 20 cm from the central axis was 4.3, 5.3, and 6.2 mm, respectively, for filtered backprojection and 3.7, 4.3, and 5.1 mm, respectively, for ordered-subset expectation maximization. The NEMA sensitivity was 47.30 and 47.05 cps/kBq at the axial center of the FOV and at a 10-cm radial offset, respectively. The scatter fraction, count rate accuracy, and peak noise-equivalent count rates were 35.4%, 1.7%, and 501.7 kcps, respectively, at 15.7 kBq/mL. Contrast recovery for the NEMA body phantom from the smallest to the largest sphere ranged from 61.3% to 93.0%, with a background variability of 5.4%-11.7% and a lung error of 5.1% for Q.Clear (β-value, 50). Good patient image quality was obtained with the Omni Legend 32. Conclusion: The Omni Legend 32 has class-leading sensitivity and count rates within the category of whole-body PET systems while maintaining spatial resolution broadly comparable to that of other current SiPM-based PET/CT systems. This combination of properties results in a very good image quality.

Submillimeter-Resolution PET for High-Sensitivity Mouse Brain Imaging.

PET is a powerful molecular imaging technique that can provide functional information on living objects. However, the spatial resolution of PET imaging has been limited to around 1 mm, which makes it difficult to visualize mouse brain function in detail. Here, we report an ultrahigh-resolution small-animal PET scanner we developed that can provide a resolution approaching 0.6 mm to visualize mouse brain function with unprecedented detail. Methods: The ultrahigh-resolution small-animal PET scanner has an inner diameter of 52.5 mm and axial coverage of 51.5 mm. The scanner consists of 4 rings, each of which has 16 depth-of-interaction detectors. Each depth-of-interaction detector consists of a 3-layer staggered lutetium yttrium orthosilicate crystal array with a pitch of 1 mm and a 4 × 4 silicon photomultiplier array. The physical performance was evaluated in accordance with the National Electrical Manufacturers Association NU4 protocol. Spatial resolution was evaluated with phantoms of various resolutions. In vivo glucose metabolism imaging of the mouse brain was performed. Results: Peak absolute sensitivity was 2.84% with an energy window of 400-600 keV. The 0.55-mm rod structure of a resolution phantom was resolved using an iterative algorithm. In vivo mouse brain imaging with 18F-FDG clearly identified the cortex, thalamus, and hypothalamus, which were barely distinguishable in a commercial preclinical PET scanner that we used for comparison. Conclusion: The ultrahigh-resolution small-animal PET scanner is a promising molecular imaging tool for neuroscience research using rodent models.

Simulation study of a brain PET scanner using TOF-DOI detectors equipped with first interaction position detection

Objective. The aim of this study is to evaluate the performance characteristics of a brain positron emission tomography (PET) scanner composed of four-layer independent read-out time-of-flight depth-of-interaction (TOF-DOI) detectors capable of first interaction position (FIP) detection, using Geant4 application for tomographic emission(GATE). This includes the spatial resolution, sensitivity, count rate capability, and reconstructed image quality. Approach. The proposed TOF-DOI PET detector comprises four layers of a 50 × 50 cerium-doped lutetium–yttrium oxyorthosilicate (LYSO:Ce) scintillator array with 1 mm pitch size, coupled to a 16 × 16 multi-pixel photon counter array with 3.0 mm × 3.0 mm photosensitive segments. Along the direction distant from the center field-of-view (FOV), the scintillator thickness of the four layers is 2.5, 3, 4, and 6 mm. The four layers were simulated with a 150 ps coincidence time resolution and the independent readout make the FIP detection capable. The spatial resolution and imaging performance were compared among the true-FIP, winner-takes-all (WTA) and front-layer FIP (FL-FIP) methods (FL-FIP selects the interaction position located on the front-most interaction layer in all the interaction layers). The National Electrical Manufacturers Association NU 2-2018 procedure was referred and modified to evaluate the performance of proposed scanner. Main results. In detector evaluation, the intrinsic spatial resolutions were 0.52 and 0.76 mm full width at half-maximum (FWHM) at 0° and 30° incident γ-rays in the first layer pair, respectively. The reconstructed spatial resolution by the filter backprojection (FBP) achieved sub-millimeter FWHM on average over the whole FOV. The maximum true count rate was 207.6 kcps at 15 kBq ml−1 and the noise equivalent count rate (NECR_2R) was 54.7 kcps at 6.0 kBq ml−1. Total sensitivity was 45.2 cps kBq−1 and 48.4 cps kBq−1 at the center and 10 cm off-center FOV, respectively. The TOF and DOI reconstructions significantly improved the image quality in the phantom studies. Moreover, the FL-FIP outperformed the conventional WTA method in terms of the spatial resolution and image quality. Significance. The proposed brain PET scanner could achieve sub-millimeter spatial resolution and high image quality with TOF and DOI reconstruction, which is meaningful to the clinical oncology research. Meanwhile, the comparison among the three positioning methods indicated that the FL-FIP decreased the image degradation caused by Compton scatter more than WTA.

Evaluation of the performance of a high-resolution time-of-flight PET system dedicated to the head and breast according to NEMA NU 2-2012 standard

BackgroundThis study evaluated the physical performance of a positron emission tomography (PET) system dedicated to the head and breast according to the National Electrical Manufacturers Association (NEMA) NU2-2012 standard.MethodsThe spatial resolution, sensitivity, scatter fraction, count rate characteristics, corrections for count losses and randoms, and image quality of the system were determined. All measurements were performed according to the NEMA NU2-2012 acquisition protocols, but image quality was assessed using a brain-sized phantom. Furthermore, scans of the three-dimensional (3D) Hoffmann brain phantom and mini-Derenzo phantom were acquired to allow visual evaluation of the imaging performance for small structures.ResultsThe tangential, radial, and axial full width at half maximum (FWHM) at a 10-mm offset in half the axial field of view were measured as 2.3, 2.5, and 2.9 mm, respectively. The average system sensitivity at the center of the field of view and at a 10-cm radial offset was 7.18 and 8.65 cps/kBq, respectively. The peak noise-equivalent counting rate was 35.2 kcps at 4.8 kBq/ml. The corresponding scatter fraction at the peak noise-equivalent counting rate was 46.8%. The peak true rate and scatter fraction at 8.6 kBq/ml were 127.8 kcps and 54.3%, respectively. The percent contrast value for a 10-mm sphere was approximately 50%. On the 3D Hoffman brain phantom image, the structures of the thin layers composing the phantom were visualized on the sagittal and coronal images. On the mini-Derenzo phantom, each of the 1.6-mm rods was clearly visualized.ConclusionTaken together, these results indicate that the head- and breast-dedicated PET system has high resolution and is well suited for clinical PET imaging.

Performance Evaluation of a PET of 7T Bruker Micro-PET/MR Based on NEMA NU 4-2008 Standards

Purpose: This study aimed to measure the performance evaluation of the Bruker sequential micro-positron emission tomography/magnetic resonance imaging (PET/MRI) scanner by following National Electrical Manufacturers Association (NEMA) NU 4-2008 standards’ protocol. The system consists of a high-performance silicon photomultiplier (SiPM) advanced technology detector and a continuous lutetium-yttrium oxyorthosilicate (LYSO) crystal. Methods: A 22Na (sodium-22) point source was utilized to assess the spatial resolution and system sensitivity, and the Micro-PET scatter phantom measurements were conducted to measure count rate measurements and scatter fractions (SF). A mouse-like Micro-PET image quality (IQ) phantom was utilized as a model to analyze the uniformity, recovery coefficient (RC), and spillover ratio (SOR). A small animal PET/MRI imaging study was performed in a rat. Results: We calculated the spatial resolutions of filtered back-projection (FBP), and used 3D-MLEM to reconstruct PET images at the axial center and ¼ of the axial field of view (FOV) in axial, radial, and tangential directions. The best observed spatial resolutions in both reconstructed images were obtained in the tangential direction, and the values were 0.80 mm in 3D-MLEM and 0.94 mm in FBP. The peak noise equivalent count rate (NECR) in the 358–664 keV energy window was 477.30 kcps at 95.83 MBq and 774.45 kcps at 103.6 MBq for rat and mouse-sized scatter phantoms, respectively. The rat and mouse-sized phantoms scatter fractions (SF) were 14.2% and 6.9%, respectively. Conclusions: According to our results, the performance characteristics of the scanner are high sensitivity, good spatial resolution, low scatter fraction, and good IQ, indicating that it is suitable for preclinical imaging studies.

Technical Note: Performance evaluation of a small‐animal PET/CT system based on NEMA NU 4–2008 standards

The MetisTM PET/CT is a self-developed, silicon photomultiplier (SiPM) detector-based, rodent PET/CT system. The objective of this study was to evaluate the performance of the system using the National Electrical Manufacturers Association (NEMA) NU 4-2008 standard protocol. Energy resolution, spatial resolution, sensitivity, scatter fraction (SF), noise-equivalent count rate (NECR), and image quality (IQ) characteristics were measured. A micro Derenzo phantom experiment was performed to evaluate the spatial resolution using three-dimensional ordered-subsets expectation maximization (3D-OSEM) and maximum likelihood expectation maximization (MLEM) reconstructed images. In addition, the CT imaging agent Ioverol 350 was mixed with fluorine-18 (18 F)-fluorodeoxyglucose (FDG) and then injected into the micro Derenzo phantom to evaluate the PET/CT imaging. In vivo PET/CT imaging studies were also conducted in a healthy mouse and rat using 18 F-FDG. The mean energy resolution of the system was 15.3%. The tangential resolution was 0.82mm full-width half-maximum (FWHM) at the center of the field of the view (FOV), and the radial and axial resolution were generally lower than 2.0mm FWHM. The spatial resolution was significantly improved when using 3D-OSEM, especially the axial FWHM could be improved by up to about 57%. The system absolute sensitivity was 7.7% and 6.8% for an energy window of 200-750 and 350-750keV respectively. The scatter fraction was 8.2% and 12.1% for the mouse- and rat-like phantom respectively. The peak NECR was 1343.72kcps at 69MBq and 640.32kcps at 53MBq for the mouse- and rat-like phantom respectively. The 1-mm fillable rod in the IQ phantom can be clearly observed. We can identify the 0.6-mm aperture of the micro Derenzo phantom image clearly using 3D-OSEM (10 subsets, 5 iterations). We also performed the fusion of the PET and CT images of the mouse and the brain imaging of the rat. The results show that the system has the characteristics of high-resolution, high-sensitivity, and excellent IQ and is suitable for rodent imaging-based research.

Performance Characteristics of the Biograph Vision Quadra PET/CT System with a Long Axial Field of View Using the NEMA NU 2-2018 Standard.

Our purpose was to evaluate the performance of the Biograph Vision Quadra PET/CT system. This new system is based on the Biograph Vision 600, using the same silicon photomultiplier-based detectors with 3.2 × 3.2 × 20 mm lutetium-oxoorthosilicate crystals. The 32 detector rings of the Quadra provide a 4-fold larger axial field of view (AFOV) of 106 cm, enabling imaging of major organs in 1 bed position. Methods: The physical performance of the scanner was evaluated according to the National Electrical Manufacturers Association NU 2-2018 standard, with additional experiments to characterize energy resolution. Image quality was assessed with foreground-to-background ratios of 4:1 and 8:1. Additionally, a clinical 18F-FDG PET study was reconstructed with varying frame durations. In all experiments, data were acquired using the maximum ring distance of 322 crystals (MRD 322), whereas image reconstructions could be performed with a maximum ring distance of only 85 crystals (MRD 85). Results: The spatial resolution at full width at half maximum in the radial, tangential, and axial directions was 3.3, 3.4, and 3.8 mm, respectively. The sensitivity was 83 cps/kBq for MRD 85 and 176 cps/kBq for MRD 322. The noise-equivalent count rates (NECRs) at peak were 1,613 kcps for MRD 85 and 2,956 kcps for MRD 322, both at 27.49 kBq/mL. The respective scatter fractions at peak NECR equaled 36% and 37%. The time-of-flight resolution at peak NECR was 228 ps for MRD 85 and 230 ps for MRD 322. Image contrast recovery ranged from 69.6% to 86.9% for 4:1 contrast ratios and from 77.7% to 92.6% for 8:1 contrast ratios reconstructed using point-spread function time of flight with 8 iterations and 5 subsets. Thirty-second frames provided readable lesion detectability and acceptable noise levels in clinical images. Conclusion: The Biograph Vision Quadra PET/CT device has spatial and time resolution similar to those of the Biograph Vision 600 but exhibits improved sensitivity and NECR because of its extended AFOV. The reported spatial resolution, time resolution, and sensitivity make it a competitive new device in the class of PET scanners with an extended AFOV.

Performance characteristic evaluation of a bismuth germanate-based high-sensitivity 5-ring discovery image quality positron emission tomography/computed tomography system as per National Electrical Manufacturers Association NU 2-2012.

National Electrical Manufacturers Association (NEMA) provides guidelines to assess the performance of Positron Emission Tomography (PET). A PET/CT scanner, Discovery IQ, GE Medical systems, Milwaukee, USA was installed in our department which has high a sensitivity PET component. We have performed the NEMA NU-2 2012 quality control tests to evaluate this system on site before clinical use. Performance measurements of the PET scanner were made using the NEMA NU2-2012 procedures for spatial resolution, scatter fraction, sensitivity, count rate loss and random coincidence estimation, Noise Equivalent Count Rate (NECR) and image quality. As per NU2 2012, spatial resolution was measured at 1 cm, 10 cm and 20 cm vertically from the centre and at each of these points resolution was measured at tangential, radial and axial directions. Sensitivity was measured at centre and 10 cm off center vertically from the center. The system sensitivity is reported as an average of the two measured values. Scatter fraction and NECR measurements, Image quality test was also performed. The tangential, radial and axial FWHM were 4.99 mm, 4.20 mm and 4.79 mm at 1 cm off centre, 5.49 mm, 4.69 mm and 4.81 mm at 10 cm off centre and 7.99 mm, 5.07 mm and 4.95 mm at 20 cm off centre respectively. The absolute sensitivity of this scanner was found to be 20.1 cps/kBq. The scatter fraction calculated from the decay method was 37.94% and NECR was 125 kcps. The peak NECR was achieved at activity concentration of 8.7 KBq/ml and the count loss below the peak NECR was found to be 0.68%. Image quality test for, contrast recovery, background variability and lung error residual mean met all specifications. Overall PET performance of Discovery IQ whole-body scanner was satisfactory and the scanner met all the performance specifications required by NEMA 2012.

High-Throughput PET/CT Imaging Using a Multiple-Mouse Imaging System.

A considerable limitation of current small-animal PET/CT imaging is the low throughput of acquisitions. Consequently, to sufficiently power a study, high costs accumulate. Together with a commercial scanner manufacturer, we developed a 4-bed mouse “hotel” to simultaneously image up to 4 mice, thereby reducing costs and maximizing the efficiency of radiotracer use when compared with scans performed with a single mouse bed. Methods: For physiologic evaluation of the mouse hotel, temperature and anesthesia were tested for uniformity in conjunction with 18F-FDG PET/CT imaging of mini image-quality phantoms designed to fit the new imaging system. After reconstruction, National Electrical Manufacturers Association NU-4 tests examined uniformity, recovery coefficients, and spillover ratios. To evaluate the mouse hotel under standard in vivo imaging conditions, 4 mice were simultaneously scanned by dynamic 18F-FDG PET/CT over 60 min, and quantified images were compared with those acquired using a single mouse bed. Results: The mouse hotel maintained a constant temperature of 36.8°C ± 0.4°C, with anesthesia distributed evenly to each nose cone (2.9 ± 0.1 L/min). The National Electrical Manufacturers Association tests revealed values within tolerable limits for uniformity, for recovery coefficients in rods larger than 2 mm, and for spillover ratios in the nonradioactive water- and air-filled chambers. There was low variability in radiotracer uptake in all major organs for the mouse hotel versus the single mouse bed. Conclusion: Analysis of images acquired using the mouse hotel confirmed its utility to increase the throughput of small-animal PET imaging without considerable loss of image quality or quantitative precision. In comparison to a single mouse bed, the cost and time associated with each scan were substantially reduced.

Performance evaluation of the 5‐Ring GE Discovery MI PET/CT system using the national electrical manufacturers association NU 2‐2012 Standard

PET performance was evaluated at three different institutions. Spatial resolution, sensitivity, counting rate performance, accuracy, and image quality were measured in accordance with National Electrical Manufacturers Association NU 2-2012 standards. The mean energy resolution, mean timing resolution, and PET/CT subsystem alignment were also measured. Phantoms were used to determine the effects of varying acquisition time and reconstruction parameters on image quality. Retrospective patient scans were reconstructed with various scan durations to evaluate the impact on image quality. Results from all three institutions were similar. Radial/tangential/axial full width at half maximum spatial resolution measurements using the filtered back projection algorithm were 4.3/4.3/5.0mm, 5.5/4.6/6.5mm, and 7.4/5.0/6.6mm at 1, 10, and 20cm from the center of the FOV, respectively. Measured sensitivity at the center of the FOV (20.84cps/kBq) was significantly higher than systems with reduced axial FOV. The peak noise-equivalent counting rate was 266.3kcps at 20.8kBq/ml, with a corresponding scatter fraction of 40.2%. The correction accuracy for count losses up to the peak noise-equivalent counting rate was 3.6%. For the 10-, 13-, 17-, 22-, 28-, and 37-mm spheres, contrast recoveries in the image quality phantom were measured to be 46.2%, 54.3%, 66.1%, 71.1%, 85.3%, and 89.3%, respectively. The mean energy and timing resolution were 9.55% and 381.7ps, respectively. Phantom and patient images demonstrated excellent image quality, even at short acquisition times or low injected activity. Compared to other PET/CT models, the extended axial FOV improved the overall PET performance of the 5-ring GE Discovery MI scanner. This system offers the potential to reduce scan times or injected activities through increased sensitivity.

NEMA NU 4-2008 and in vivo imaging performance of RAYCAN trans-PET/CT X5 small animal imaging system

The RAYCAN Trans-PET/CT X5 is a preclinical positron emission tomography and computed tomography (PET/CT) system intended for in vivo imaging of rats and mice, featuring all-digital readout electronics for PET data acquisition.The National Electrical Manufacturers Association (NEMA) NU 4-2008 performance evaluation was conducted on the RAYCAN Trans-PET/CT X5 in addition to assessing in vivo imaging performance of the system on live animals. The performance characteristics of the system were evaluated, including system spatial resolution, count rate performance, sensitivity and image quality. The system imaging performance is assessed in dynamic in vivo PET imaging.The system resolution defined as full width half maximum (FWHM) was 2.07 mm, 2.11 mm and 1.31 mm for the tangential, radial and axial resolution, respectively, at the center of the field of view. The peak noise equivalent count rate (NECR) values measured were 61 kcps at 0.19 MBq ml−1 for the rat size phantom and 126 kcps at 1.53 MBq ml−1 for the mouse size phantom. Scatter fractions were 24% and 14% for the rat and mouse phantom. The measured peak sensitivity of the system was 1.70%. Image quality in static imaging was deemed sufficient based on the image quality phantom study, with average activity concentration of 155 ± 8.6 kBq ml−1 and image uniformity of 5.57% when using two-dimensional filtered backprojection algorithm (2D-FBP). Rods in the image quality phantom were visualized easily up to 2 mm in size. In dynamic in vivo PET imaging, time-activity-curves from several regions were successfully measured, characterizing the radioactivity distribution in myocardial blood pool, liver, left ventricle and the lung.In conclusion, the RAYCAN Trans-PET/CT X5 system can be considered a suitable option for basic imaging needs in preclinical imaging.

NEMA NU-4 performance evaluation of a non-human primate animal PET

The Eplus-260 primate PET is an animal PET imaging system developed by the Institute of High Energy Physics, Chinese Academy of Sciences, which is designed to image non-human primates, especially the brain of large non-human primates. The system consists of 48 block detectors arranged in two 24-sided rings with a ring diameter of 263 mm and an axial extent of 64 mm. Each block detector is composed of a 16 × 16 cerium-doped lutetium–yttrium orthosilicate crystal array with a pixel size of 1.9 × 1.9 × 10 mm3. This article presents a performance evaluation of the PET scanner according to the National Electrical Manufacturers Association NU-4 2008 standards. All measurements were made for an energy window of 360–660 keV and a coincidence timing window of 2 ns. In terms of the FWHM, the FBP reconstructed spatial resolution results in all three directions at the radial position of 5 mm were better than or approached to 2 mm, and remained below 3.0 mm within the central 5 cm diameter of the FOV. The peak absolute sensitivity of the scanner was measured 1.80%. For a monkey-sized phantom, the scatter fraction was 34.2% and the peak noise equivalent count rate (NECR) was 26.5 kcps at 64.3 kBq/cc. The overall imaging capabilities of the scanner were also assessed using in vivo imaging study of a rhesus macaque. The performance measurements demonstrate that the Eplus-260 primate PET scanner has the potential ability to obtain good quality and high-contrast images for non-human primates, especially the brain of large non-human primates and could be considered as one technologically advanced dedicated non-human primate PET scanner available today.

Precise System Models using Crystal Penetration Error Compensation for Iterative Image Reconstruction of Preclinical Quad-Head PET

A-PET is a quad-head PET scanner developed for use in small-animal imaging. The dimensions of its volumetric field of view (FOV) are 46.1 × 46.1 × 46.1 mm3 and the gap between the detector modules has been minimized in order to provide a highly sensitive system. However, such a small FOV together with the quad-head geometry causes image quality degradation. The main factor related to image degradation for the quad-head PET is the mispositioning of events caused by the penetration effect in the detector. In this paper, we propose a precise method for modelling the system at the high spatial resolution of the A-PET using a LOR (line of response) based ML-EM (maximum likelihood expectation maximization) that allows for penetration effects. The proposed system model provides the detection probability of every possible ray-path via crystal sampling methods. For the ray-path sampling, the sub-LORs are defined by connecting the sampling points of the crystal pair. We incorporate the detection probability of each sub-LOR into the model by calculating the penetration effect. For comparison, we used a standard LOR-based model and a Monte Carlo-based modeling approach, and evaluated the reconstructed images using both the National Electrical Manufacturers Association NU 4–2008 standards and the Geant4 Application for Tomographic Emission simulation toolkit (GATE). An average full width at half maximum (FWHM) at different locations of 1.77 mm and 1.79 mm are obtained using the proposed system model and standard LOR system model, which does not include penetration effects, respectively. The standard deviation of the uniform region in the NEMA image quality phantom is 2.14% for the proposed method and 14.3% for the LOR system model, indicating that the proposed model out-performs the standard LOR-based model.

NEMA NU-4 Performance Evaluation of the IRIS PET/CT Preclinical Scanner

This paper presents the performance assessment study of the PET component of the IRIS PET/CT according to the National Electrical Manufacturers Association NU 4–2008 standard. The IRIS PET/CT is a high-resolution integrated system for PET and CT imaging of small animals. We evaluated the performance of the PET system, carrying out the following measures: spatial resolution, sensitivity, counting rate capabilities, and image quality parameters. Furthermore, two examples of in vivo experiments are shown. The average energy resolution for a whole module is 14% at 511 keV. The maximum absolute sensitivity for a point source at the center of the field-of-view is 8.0 ± 1.1% for 250–750 keV energy window and 6.6 ± 1.0% for 350–750 keV. The scatter fraction for mouse-like and rat-like phantoms are 15.6% (250–750 keV) and 22.4% (350–750 keV), respectively. Recovery coefficients were measured with the image-quality phantom, providing good results with an image uniformity of 7%. The imaging performance of the IRIS PET are confirmed in the animal experiments. With the IRIS PET/CT, it was possible to derive the time activity curve for various regions of interest with time frame duration down to 5 s, thus enabling the possibility to derive the tracer input function.

Performance evaluation of a LYSO-based PET scanner for monitoring of dose delivery in hadrontherapy

The DoPET scanner is a compact positron emission tomography (PET) device. It has been developed for monitoring the range of charged particles during therapy with hadron beams. Previous works have focused on the development and upgrade of the device and on data analysis. In this paper, a full performance characterization of the DoPET system in terms of the energy resolution, spatial resolution, sensitivity, uniformity, and noise equivalent count rate is reported. All measurements refer to an adapted version of the National Electrical Manufacturers Association (NEMA) NU 4 - 2008 protocol, which was written originally for small animal PET systems. Since DoPET is a dual head planar system, it requires a modified characterisation procedure with respect to those described for ring geometries as in the NEMA NU 4 - 2008 protocol. The presented procedure may be of interest for any other PET system with a similar geometry as DoPET.