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Könik A, Auer B, De Beenhouwer J, Kalluri K, Zeraatkar N, Furenlid LR, King MA. Primary, scatter, and penetration characterizations of parallel-hole and pinhole collimators for I-123 SPECT. Phys Med Biol 2019; 64:245001. [PMID: 31746783 DOI: 10.1088/1361-6560/ab58fe] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
Multi-pinhole (MPH) collimators are known to provide better trade-off between sensitivity and resolution for preclinical, as well as for smaller regions in clinical SPECT imaging compared to conventional collimators. In addition to this geometric advantage, MPH plates typically offer better stopping power for penetration than the conventional collimators, which is especially relevant for I-123 imaging. The I-123 emits a series of high-energy (>300 keV, ~2.5% abundance) gamma photons in addition to the primary emission (159 keV, 83% abundance). Despite their low abundance, high-energy photons penetrate through a low-energy parallel-hole (LEHR) collimator much more readily than the 159 keV photons, resulting in large downscatter in the photopeak window. In this work, we investigate the primary, scatter, and penetration characteristics of a single pinhole collimator that is commonly used for I-123 thyroid imaging and our two MPH collimators designed for I-123 DaTscan imaging for Parkinson's Disease, in comparison to three different parallel-hole collimators through a series of experiments and Monte Carlo simulations. The simulations of a point source and a digital human phantom with DaTscan activity distribution showed that our MPH collimators provide superior count performance in terms of high primary counts, low penetration, and low scatter counts compared to the parallel-hole and single pinhole collimators. For example, total scatter, multiple scatter, and collimator penetration events for the LEHR were 2.5, 7.6 and 14 times more than that of MPH within the 15% photopeak window. The total scatter fraction for LEHR was 56% where the largest contribution came from the high-energy scatter from the back compartments (31%). For the same energy window, the total scatter for MPH was 21% with only 1% scatter from the back compartments. We therefore anticipate that using MPH collimators, higher quality reconstructions can be obtained in a substantially shorter acquisition time for I-123 DaTscan and thyroid imaging.
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Affiliation(s)
- Arda Könik
- Department of Imaging, Dana Farber Cancer Institute, Boston, MA 02215, United States of America
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Sakai M, Yamaguchi M, Nagao Y, Kawachi N, Kikuchi M, Torikai K, Kamiya T, Takeda S, Watanabe S, Takahashi T, Arakawa K, Nakano T. In vivo simultaneous imaging with 99mTc and 18F using a Compton camera. Phys Med Biol 2018; 63:205006. [PMID: 30222127 DOI: 10.1088/1361-6560/aae1d1] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
We have been developing a medical imaging technique using a Compton camera. This study evaluates the feasibility of clear imaging with 99mTc and 18F simultaneously, and demonstrates in vivo imaging with 99mTc and/or 18F. We used a Compton camera with silicon and cadmium telluride (Si/CdTe) semiconductors. We estimated the imaging performance of the Compton camera for 141 keV and 511 keV gamma rays from 99mTc and 22Na, respectively. Next, we simultaneously imaged 99mTc and 18F point sources to evaluate the cross-talk artifacts produced by a higher energy gamma-ray background. Then, in the in vivo experiments, three rats were injected with 99mTc-dimercaptosuccinic acid and/or 18F-fluorodeoxyglucose and imaged. The Compton images were compared with PET images. The rats were euthanized, and the activities in their organs were measured using a well counter. The energy resolution and spatial resolution were measured for the sources. No apparent cross-talk artifacts were observed in the practical-activity ratio (99mTc:18F = 1:16). We succeeded in imaging the distributions of 99mTc and 18F simultaneously, and the results were consistent with the PET images and well counter measurements. Our Si/CdTe Compton camera can thus work as a multi-tracer imager, covering various SPECT and PET probes, with less cross-talk artifacts in comparison to the conventional Anger cameras using a collimator. Our findings suggest the possibility of human trials.
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Affiliation(s)
- Makoto Sakai
- Gunma University Heavy Ion Medical Center, Graduate School of Medicine, Gunma University, 3-39-22 Showa-machi, Maebashi, Gunma, Japan. Author to whom any correspondence should be addressed
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Moslemi V, Ashoor M. Design and performance evaluation of a new high energy parallel hole collimator for radioiodine planar imaging by gamma cameras: Monte Carlo simulation study. Ann Nucl Med 2017; 31:324-334. [PMID: 28275975 DOI: 10.1007/s12149-017-1160-9] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/16/2017] [Accepted: 02/16/2017] [Indexed: 11/27/2022]
Abstract
OBJECTIVE In addition to the trade-off between resolution and sensitivity which is a common problem among all types of parallel hole collimators (PCs), obtained images by high energy PCs (HEPCs) suffer from hole-pattern artifact (HPA) due to further septa thickness. In this study, a new design on the collimator has been proposed to improve the trade-off between resolution and sensitivity and to eliminate the HPA. METHODS A novel PC, namely high energy extended PC (HEEPC), is proposed and is compared to HEPCs. In the new PC, trapezoidal denticles were added upon the septa in the detector side. The performance of the HEEPCs were evaluated and compared to that of HEPCs using a Monte Carlo-N-particle version5 (MCNP5) simulation. The point spread functions (PSF) of HEPCs and HEEPCs were obtained as well as the various parameters such as resolution, sensitivity, scattering, and penetration ratios, and the HPA of the collimators was assessed. Furthermore, a Picker phantom study was performed to examine the effects of the collimators on the quality of planar images. RESULTS It was found that the HEEPCD with an identical resolution to that of HEPCC increased sensitivity by 34.7%, and it improved the trade-off between resolution and sensitivity as well as to eliminate the HPA. In the picker phantom study, the HEEPCD indicated the hot and cold lesions with the higher contrast, lower noise, and higher contrast to noise ratio (CNR). CONCLUSION Since the HEEPCs modify the shaping of PSFs, they are able to improve the trade-off between the resolution and sensitivity; consequently, planar images can be achieved with higher contrast resolutions. Furthermore, because the HEEPCS reduce the HPA and produce images with a higher CNR, compared to HEPCs, the obtained images by HEEPCs have a higher quality, which can help physicians to provide better diagnosis.
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Affiliation(s)
- Vahid Moslemi
- Nuclear Science and Technology Research Institute, AEOI, P.O. Box: 113653486, Tehran, Iran.
| | - Mansour Ashoor
- Nuclear Science and Technology Research Institute, AEOI, P.O. Box: 113653486, Tehran, Iran
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van der Have F, Ivashchenko O, Goorden MC, Ramakers RM, Beekman FJ. High-resolution clustered pinhole 131Iodine SPECT imaging in mice. Nucl Med Biol 2016; 43:506-11. [DOI: 10.1016/j.nucmedbio.2016.05.015] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/05/2016] [Revised: 05/12/2016] [Accepted: 05/28/2016] [Indexed: 11/25/2022]
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Kojima A, Gotoh K, Shimamoto M, Hasegawa K, Okada S. Iodine-131 imaging using 284 keV photons with a small animal CZT-SPECT system dedicated to low-medium-energy photon detection. Ann Nucl Med 2015; 30:169-75. [DOI: 10.1007/s12149-015-1028-9] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2015] [Accepted: 09/11/2015] [Indexed: 01/28/2023]
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Van Audenhaege K, Van Holen R, Vandenberghe S, Vanhove C, Metzler SD, Moore SC. Review of SPECT collimator selection, optimization, and fabrication for clinical and preclinical imaging. Med Phys 2015; 42:4796-813. [PMID: 26233207 PMCID: PMC5148182 DOI: 10.1118/1.4927061] [Citation(s) in RCA: 81] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2015] [Revised: 07/07/2015] [Accepted: 07/08/2015] [Indexed: 01/23/2023] Open
Abstract
In single photon emission computed tomography, the choice of the collimator has a major impact on the sensitivity and resolution of the system. Traditional parallel-hole and fan-beam collimators used in clinical practice, for example, have a relatively poor sensitivity and subcentimeter spatial resolution, while in small-animal imaging, pinhole collimators are used to obtain submillimeter resolution and multiple pinholes are often combined to increase sensitivity. This paper reviews methods for production, sensitivity maximization, and task-based optimization of collimation for both clinical and preclinical imaging applications. New opportunities for improved collimation are now arising primarily because of (i) new collimator-production techniques and (ii) detectors with improved intrinsic spatial resolution that have recently become available. These new technologies are expected to impact the design of collimators in the future. The authors also discuss concepts like septal penetration, high-resolution applications, multiplexing, sampling completeness, and adaptive systems, and the authors conclude with an example of an optimization study for a parallel-hole, fan-beam, cone-beam, and multiple-pinhole collimator for different applications.
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Affiliation(s)
- Karen Van Audenhaege
- Department of Electronics and Information Systems, MEDISIP-IBiTech, Ghent University-iMinds Medical IT, De Pintelaan 185 block B/5, Ghent B-9000, Belgium
| | - Roel Van Holen
- Department of Electronics and Information Systems, MEDISIP-IBiTech, Ghent University-iMinds Medical IT, De Pintelaan 185 block B/5, Ghent B-9000, Belgium
| | - Stefaan Vandenberghe
- Department of Electronics and Information Systems, MEDISIP-IBiTech, Ghent University-iMinds Medical IT, De Pintelaan 185 block B/5, Ghent B-9000, Belgium
| | - Christian Vanhove
- Department of Electronics and Information Systems, MEDISIP-IBiTech, Ghent University-iMinds Medical IT, De Pintelaan 185 block B/5, Ghent B-9000, Belgium
| | - Scott D Metzler
- Department of Radiology, University of Pennsylvania, Philadelphia, Pennsylvania 19104
| | - Stephen C Moore
- Division of Nuclear Medicine, Department of Radiology, Brigham and Women's Hospital and Harvard Medical School, 75 Francis Street, Boston, Massachusetts 02115
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Roshan HR, Azarm A, Mahmoudian B, Islamian JP. Advances in SPECT for Optimizing the Liver Tumors Radioembolization Using Yttrium-90 Microspheres. World J Nucl Med 2015; 14:75-80. [PMID: 26097416 PMCID: PMC4455176 DOI: 10.4103/1450-1147.157120] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/04/2022] Open
Abstract
Radioembolization (RE) with Yttrium-90 ((90)Y) microspheres is an effective treatment for unresectable liver tumors. The activity of the microspheres to be administered should be calculated based on the type of microspheres. Technetium-99m macroaggregated albumin ((99m)Tc-MAA) single photon emission computed tomography/computed tomography (SPECT/CT) is a reliable assessment before RE to ensure the safe delivery of microspheres into the target. (90)Y bremsstrahlung SPECT imaging as a posttherapeutic assessment approach enables the reliable determination of absorbed dose, which is indispensable for the verification of treatment efficacy. This article intends to provide a review of the methods of optimizing (90)Y bremsstrahlung SPECT imaging to improve the treatment efficacy of liver tumor RE using (90)Y microspheres.
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Affiliation(s)
- Hoda Rezaei Roshan
- Department of Medical Physics, Nuclear Medicine Unit, Faculty of Medicine, Tabriz University of Medical Sciences, Tabriz, Iran
| | - Ahmadreza Azarm
- Department of Medical Physics, Nuclear Medicine Unit, Faculty of Medicine, Tabriz University of Medical Sciences, Tabriz, Iran
| | - Babak Mahmoudian
- Department of Radiology, Nuclear Medicine Unit, Faculty of Medicine, Tabriz University of Medical Sciences, Tabriz, Iran
| | - Jalil Pirayesh Islamian
- Department of Medical Physics, Nuclear Medicine Unit, Faculty of Medicine, Tabriz University of Medical Sciences, Tabriz, Iran
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Walrand S, Hesse M, Wojcik R, Lhommel R, Jamar F. Optimal design of anger camera for bremsstrahlung imaging: monte carlo evaluation. Front Oncol 2014; 4:149. [PMID: 24982849 PMCID: PMC4056384 DOI: 10.3389/fonc.2014.00149] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/28/2014] [Accepted: 05/29/2014] [Indexed: 11/29/2022] Open
Abstract
A conventional Anger camera is not adapted to bremsstrahlung imaging and, as a result, even using a reduced energy acquisition window, geometric x-rays represent <15% of the recorded events. This increases noise, limits the contrast, and reduces the quantification accuracy. Monte Carlo (MC) simulations of energy spectra showed that a camera based on a 30-mm-thick BGO crystal and equipped with a high energy pinhole collimator is well-adapted to bremsstrahlung imaging. The total scatter contamination is reduced by a factor 10 versus a conventional NaI camera equipped with a high energy parallel hole collimator enabling acquisition using an extended energy window ranging from 50 to 350 keV. By using the recorded event energy in the reconstruction method, shorter acquisition time and reduced orbit range will be usable allowing the design of a simplified mobile gantry. This is more convenient for use in a busy catheterization room. After injecting a safe activity, a fast single photon emission computed tomography could be performed without moving the catheter tip in order to assess the liver dosimetry and estimate the additional safe activity that could still be injected. Further long running time MC simulations of realistic acquisitions will allow assessing the quantification capability of such system. Simultaneously, a dedicated bremsstrahlung prototype camera reusing PMT–BGO blocks coming from a retired PET system is currently under design for further evaluation.
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Affiliation(s)
- Stephan Walrand
- Department of Nuclear Medicine, Molecular Imaging, Radiotherapy and Oncology Unit (MIRO), IECR, Université Catholique de Louvain , Brussels , Belgium
| | - Michel Hesse
- Department of Nuclear Medicine, Molecular Imaging, Radiotherapy and Oncology Unit (MIRO), IECR, Université Catholique de Louvain , Brussels , Belgium
| | | | - Renaud Lhommel
- Department of Nuclear Medicine, Molecular Imaging, Radiotherapy and Oncology Unit (MIRO), IECR, Université Catholique de Louvain , Brussels , Belgium
| | - François Jamar
- Department of Nuclear Medicine, Molecular Imaging, Radiotherapy and Oncology Unit (MIRO), IECR, Université Catholique de Louvain , Brussels , Belgium
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Capote RM, Matela N, Conceição RC, Almeida P. Optimization of convergent collimators for pixelated SPECT systems. Med Phys 2014; 40:062501. [PMID: 23718606 DOI: 10.1118/1.4804053] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022] Open
Abstract
PURPOSE The optimization of the collimator design is essential to obtain the best possible sensitivity in single photon emission computed tomography imaging. The aim of this work is to present a methodology for maximizing the sensitivity of convergent collimators, specifically designed to match the pitch of pixelated detectors, for a fixed spatial resolution value and to present some initial results using this approach. METHODS Given the matched constraint, the optimal collimator design cannot be simply found by allowing the highest level of septal penetration and spatial resolution consistent with the imposed restrictions, as it is done for the optimization of conventional collimators. Therefore, an algorithm that interactively calculates the collimator dimensions, with the maximum sensitivity, which respect the imposed restrictions was developed and used to optimize cone and fan beam collimators with tapered square-shaped holes for low (60-300 keV) and high energy radiation (300-511 keV). The optimal collimator dimensions were locally calculated based on the premise that each hole and septa of the convergent collimator should locally resemble an appropriate optimal matched parallel collimator. RESULTS The optimal collimator dimensions, calculated for subcentimeter resolutions (3 and 7.5 mm), common pixel sizes (1.6, 2.1, and 2.5 mm), and acceptable septal penetration at 140 keV, were approximately constant throughout the collimator, despite their different hole incidence angles. By using these input parameters and a less strict septal penetration value of 5%, the optimal collimator dimensions and the corresponding mass per detector area were calculated for 511 keV. It is shown that a low value of focal distance leads to improvements in the average sensitivity at a fixed source-collimator distance and resolution. The optimal cone beam performance outperformed that of other optimal collimation geometries (fan and parallel beam) in imaging objects close to the collimator surface. CONCLUSIONS These results demonstrate the potential of this kind of optimal convergent collimators for the use in small field of view imaging applications.
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Affiliation(s)
- Ricardo M Capote
- Universidade de Lisboa, Faculdade de Ciências, Instituto de Biofísica e Engenharia Biomédica, Campo Grande, 1749-016 Lisboa, Portugal.
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