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Régio Brambilla C, Scheins J, Tellmann L, Issa A, Herzog H, Shah NJ, Neuner I, Lerche CW. Impact of framing scheme optimization and smoking status on binding potential analysis in dynamic PET with [ 11C]ABP688. EJNMMI Res 2023; 13:11. [PMID: 36757553 PMCID: PMC9911569 DOI: 10.1186/s13550-023-00957-8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2022] [Accepted: 01/24/2023] [Indexed: 02/10/2023] Open
Abstract
BACKGROUND For positron emission tomography (PET) ligands, such as [11C]ABP688, to be able to provide more evidence about the glutamatergic hypothesis in schizophrenia (SZ), quantification bias during dynamic PET studies and its propagation into the estimated values of non-displaceable binding potential (BPND) must be addressed. This would enable more accurate quantification during bolus + infusion (BI) neuroreceptor studies and further our understanding of neurological diseases. Previous studies have shown BPND-related biases can often occur due to overestimated cerebellum activity (reference region). This work investigates whether an alternative framing scheme can minimize quantification biases propagated into BPND, whether confounders, such as smoking status, need to be controlled for during the study, and what the consequences for the data interpretation following analysis are. A group of healthy controls (HC) and a group of SZ patients (balanced and unbalanced number of smokers) were investigated with [11C]ABP688 and a BI protocol. Possible differences in BPND quantification as a function of smoking status were tested with constant 5 min ('Const 5 min') and constant true counts ('Const Trues') framing schemes. In order to find biomarkers for SZ, the differences in smoking effects were compared between groups. The normalized BPND and the balanced number of smokers and non-smokers for both framing schemes were evaluated. RESULTS When applying F-tests to the 'Const 5 min' framing scheme, effect sizes (η2p) and brain regions which showed significant effects fluctuated considerably with F = 50.106 ± 54.948 (9.389 to 112.607), P-values 0.005 to < 0.001 and η2p = 0.514 ± 0.282 (0.238 to 0.801). Conversely, when the 'Const Trues' framing scheme was applied, the results showed much smaller fluctuations with F = 78.038 ± 8.975 (86.450 to 68.590), P < 0.001 for all conditions and η2p = 0.730 ± 0.017 (0.742 to 0.710), and regions with significant effects were more robustly reproduced. Further, differences, which would indicate false positive identifications between HC and SZ groups in five brain regions when using the 'Const 5 min' framing scheme, were not observed with the 'Const Trues' framing. CONCLUSIONS Based on an [11C]ABP688 PET study in SZ patients, the results show that non-consistent BPND outcomes can be propagated by the framing scheme and that potential bias can be minimized using 'Const Trues' framing.
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Affiliation(s)
- Cláudia Régio Brambilla
- Institute of Neuroscience and Medicine, INM-4, Forschungszentrum Jülich GmbH, Jülich, Germany.
| | - Jürgen Scheins
- grid.8385.60000 0001 2297 375XInstitute of Neuroscience and Medicine, INM-4, Forschungszentrum Jülich GmbH, Jülich, Germany
| | - Lutz Tellmann
- grid.8385.60000 0001 2297 375XInstitute of Neuroscience and Medicine, INM-4, Forschungszentrum Jülich GmbH, Jülich, Germany
| | - Ahlam Issa
- grid.8385.60000 0001 2297 375XInstitute of Neuroscience and Medicine, INM-4, Forschungszentrum Jülich GmbH, Jülich, Germany
| | - Hans Herzog
- grid.8385.60000 0001 2297 375XInstitute of Neuroscience and Medicine, INM-4, Forschungszentrum Jülich GmbH, Jülich, Germany
| | - N. Jon Shah
- grid.8385.60000 0001 2297 375XInstitute of Neuroscience and Medicine, INM-4, Forschungszentrum Jülich GmbH, Jülich, Germany ,grid.8385.60000 0001 2297 375XInstitute of Neuroscience and Medicine, INM-11, Forschungszentrum Jülich GmbH, Jülich, Germany ,grid.1957.a0000 0001 0728 696XJARA – BRAIN – Translational Medicine, RWTH Aachen University, Aachen, Germany ,grid.1957.a0000 0001 0728 696XDepartment of Neurology, RWTH Aachen University, Aachen, Germany
| | - Irene Neuner
- grid.8385.60000 0001 2297 375XInstitute of Neuroscience and Medicine, INM-4, Forschungszentrum Jülich GmbH, Jülich, Germany ,grid.1957.a0000 0001 0728 696XDepartment of Psychiatry, Psychotherapy and Psychosomatics, RWTH Aachen University, Aachen, Germany ,grid.1957.a0000 0001 0728 696XJARA – BRAIN – Translational Medicine, RWTH Aachen University, Aachen, Germany
| | - Christoph W. Lerche
- grid.8385.60000 0001 2297 375XInstitute of Neuroscience and Medicine, INM-4, Forschungszentrum Jülich GmbH, Jülich, Germany
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Millardet M, Moussaoui S, Idier J, Mateus D, Conti M, Bailly C, Stute S, Carlier T. A Multiobjective Comparative Analysis of Reconstruction Algorithms in the Context of Low-Statistics 90Y-PET Imaging. IEEE TRANSACTIONS ON RADIATION AND PLASMA MEDICAL SCIENCES 2022. [DOI: 10.1109/trpms.2021.3126951] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Affiliation(s)
- Mael Millardet
- LS2N, CNRS UMR 6004, École centrale de Nantes, Nantes, France
| | - Said Moussaoui
- LS2N, CNRS UMR 6004, École centrale de Nantes, Nantes, France
| | - Jerome Idier
- LS2N, CNRS UMR 6004, École centrale de Nantes, Nantes, France
| | - Diana Mateus
- LS2N, CNRS UMR 6004, École centrale de Nantes, Nantes, France
| | - Maurizio Conti
- Physics Research Group, Siemens Medical Solution USA Inc., Knoxville, TN, USA
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Feng T, Yao S, Xi C, Zhao Y, Wang R, Wu S, Li C, Xu B. Deep learning-based image reconstruction for TOF PET with DIRECT data partitioning format. Phys Med Biol 2021; 66. [PMID: 34256356 DOI: 10.1088/1361-6560/ac13fe] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/26/2021] [Accepted: 07/13/2021] [Indexed: 11/12/2022]
Abstract
Conventional positron emission tomography (PET) image reconstruction is achieved by the statistical iterative method. Deep learning provides another opportunity for speeding up the image reconstruction process. However, conventional deep learning-based image reconstruction requires a fully connected network for learning the Radon transform. The use of fully connected networks greatly complicated the network and increased hardware cost. In this study, we proposed a novel deep learning-based image reconstruction method by utilizing the DIRECT data partitioning method. The U-net structure with only convolutional layers was used in our approach. Patch-based model training and testing were used to achieve 3D reconstructions within current hardware limitations. Time-of-flight (TOF)-histoimages were first generated from the listmode data to replace conventional sinograms. Different projection angles were used as different channels in the input. A total of 15 patient data were used in this study. For each patient, the dynamic whole-body scanning protocol was used to expand the training dataset and a total of 372 separate scans were included. The leave-one-patient-out validation method was used. Two separate studies were carried out. In the first study, the measured TOF-histoimages were directly used for model training and testing, to study the performance of the method in real-world applications. In the second study, TOF-histoimages were simulated from already reconstructed images to exclude the scatters, randoms, attenuation-activity mismatch effects. This study was used to evaluate the optimal performance when all other corrections are ideal. Volumes of interests were placed in the liver and lesion region to study image noise and lesion quantitations. The reconstructed images using the proposed deep learning method showed similar image quality when compared with the conventional expectation-maximization approach. A minimal difference was observed when the simulated TOF-histoimages were used as model input and testing, suggesting the deep learning model can indeed learn the reconstruction process. Some quantitative difference was observed when the measured TOF-histoimages were used. The two studies suggested that the major difference is caused by inaccurate corrections performed by the network itself, which indicated that physics-based corrections are still required for better quantitative performance. In conclusion, we have proposed a novel deep learning-based image reconstruction method for TOF PET. With the help of the DIRECT data partitioning method, no fully connected layers were used and 3D image reconstruction can be directly achieved within the limits of the current hardware.
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Affiliation(s)
- Tao Feng
- UIH America, Inc., Houston, TX, United States of America
| | - Shulin Yao
- PLA General Hospital, Beijing, People's Republic of China
| | - Chen Xi
- Shanghai United Imaging Healthcare, Shanghai, People's Republic of China
| | - Yizhang Zhao
- Shanghai United Imaging Healthcare, Shanghai, People's Republic of China
| | - Ruimin Wang
- PLA General Hospital, Beijing, People's Republic of China
| | - Shina Wu
- PLA General Hospital, Beijing, People's Republic of China
| | - Can Li
- PLA General Hospital, Beijing, People's Republic of China
| | - Baixuan Xu
- PLA General Hospital, Beijing, People's Republic of China
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España S, Sánchez-Parcerisa D, Ibáñez P, Sánchez-Tembleque V, Udías JM, Onecha VV, Gutierrez-Uzquiza A, Bäcker CM, Bäumer C, Herrmann K, Fragoso Costa P, Timmermann B, Fraile LM. Direct proton range verification using oxygen-18 enriched water as a contrast agent. Radiat Phys Chem Oxf Engl 1993 2021. [DOI: 10.1016/j.radphyschem.2021.109385] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022]
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Brambilla CR, Scheins J, Issa A, Tellmann L, Herzog H, Rota Kops E, Shah NJ, Neuner I, Lerche CW. Bias evaluation and reduction in 3D OP-OSEM reconstruction in dynamic equilibrium PET studies with 11C-labeled for binding potential analysis. PLoS One 2021; 16:e0245580. [PMID: 33481896 PMCID: PMC7822533 DOI: 10.1371/journal.pone.0245580] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/14/2020] [Accepted: 01/05/2021] [Indexed: 11/26/2022] Open
Abstract
Iterative image reconstruction is widely used in positron emission tomography. However, it is known to contribute to quantitation bias and is particularly pronounced during dynamic studies with 11C-labeled radiotracers where count rates become low towards the end of the acquisition. As the strength of the quantitation bias depends on the counts in the reconstructed frame, it can differ from frame to frame of the acquisition. This is especially relevant in the case of neuro-receptor studies with simultaneous PET/MR when a bolus-infusion protocol is applied to allow the comparison of pre- and post-task effects. Here, count dependent changes in quantitation bias may interfere with task changes. We evaluated the impact of different framing schemes on quantitation bias and its propagation into binding potential (BP) using a phantom decay study with 11C and 3D OP-OSEM. Further, we propose a framing scheme that keeps the true counts per frame constant over the acquisition time as constant framing schemes and conventional increasing framing schemes are unlikely to achieve stable bias values during the acquisition time range. For a constant framing scheme with 5 minutes frames, the BP bias was 7.13±2.01% (10.8% to 3.8%) compared to 5.63±2.85% (7.8% to 4.0%) for conventional increasing framing schemes. Using the proposed constant true counts framing scheme, a stabilization of the BP bias was achieved at 2.56±3.92% (3.5% to 1.7%). The change in BP bias was further studied by evaluating the linear slope during the acquisition time interval. The lowest slope values were observed in the constant true counts framing scheme. The constant true counts framing scheme was effective for BP bias stabilization at relevant activity and time ranges. The mean BP bias under these conditions was 2.56±3.92%, which represents the lower limit for the detection of changes in BP during equilibrium and is especially important in the case of cognitive tasks where the expected changes are low.
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Affiliation(s)
- Cláudia Régio Brambilla
- Institute of Neuroscience and Medicine, INM-4, Forschungszentrum Jülich GmbH, Jülich, Germany
- Department of Psychiatry, Psychotherapy and Psychosomatics, RWTH Aachen University, Aachen, Germany
- * E-mail:
| | - Jürgen Scheins
- Institute of Neuroscience and Medicine, INM-4, Forschungszentrum Jülich GmbH, Jülich, Germany
| | - Ahlam Issa
- Institute of Neuroscience and Medicine, INM-4, Forschungszentrum Jülich GmbH, Jülich, Germany
| | - Lutz Tellmann
- Institute of Neuroscience and Medicine, INM-4, Forschungszentrum Jülich GmbH, Jülich, Germany
| | - Hans Herzog
- Institute of Neuroscience and Medicine, INM-4, Forschungszentrum Jülich GmbH, Jülich, Germany
| | - Elena Rota Kops
- Institute of Neuroscience and Medicine, INM-4, Forschungszentrum Jülich GmbH, Jülich, Germany
| | - N. Jon Shah
- Institute of Neuroscience and Medicine, INM-4, Forschungszentrum Jülich GmbH, Jülich, Germany
- Institute of Neuroscience and Medicine, INM-11, Forschungszentrum Jülich GmbH, Jülich, Germany
- JARA–BRAIN–Translational Medicine, RWTH Aachen University, Aachen, Germany
- Department of Neurology, RWTH Aachen University, Aachen, Germany
| | - Irene Neuner
- Institute of Neuroscience and Medicine, INM-4, Forschungszentrum Jülich GmbH, Jülich, Germany
- Department of Psychiatry, Psychotherapy and Psychosomatics, RWTH Aachen University, Aachen, Germany
- JARA–BRAIN–Translational Medicine, RWTH Aachen University, Aachen, Germany
| | - Christoph W. Lerche
- Institute of Neuroscience and Medicine, INM-4, Forschungszentrum Jülich GmbH, Jülich, Germany
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Millardet M, Moussaoui S, Mateus D, Idier J, Carlier T. Local-Mean Preserving Post-Processing Step for Non-Negativity Enforcement in PET Imaging: Application to 90Y-PET. IEEE TRANSACTIONS ON MEDICAL IMAGING 2020; 39:3725-3736. [PMID: 32746117 DOI: 10.1109/tmi.2020.3003428] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
In a low-statistics PET imaging context, the positive bias in regions of low activity is a burning issue. To overcome this problem, algorithms without the built-in non-negativity constraint may be used. They allow negative voxels in the image to reduce, or even to cancel the bias. However, such algorithms increase the variance and are difficult to interpret since the resulting images contain negative activities, which do not hold a physical meaning when dealing with radioactive concentration. In this paper, a post-processing approach is proposed to remove these negative values while preserving the local mean activities. Its original idea is to transfer the value of each voxel with negative activity to its direct neighbors under the constraint of preserving the local means of the image. In that respect, the proposed approach is formalized as a linear programming problem with a specific symmetric structure, which makes it solvable in a very efficient way by a dual-simplex-like iterative algorithm. The relevance of the proposed approach is discussed on simulated and on experimental data. Acquired data from an yttrium-90 phantom show that on images produced by a non-constrained algorithm, a much lower variance in the cold area is obtained after the post-processing step, at the price of a slightly increased bias. More specifically, when compared with the classical OSEM algorithm, images are improved, both in terms of bias and of variance.
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Efthimiou N, Kratochwil N, Gundacker S, Polesel A, Salomoni M, Auffray E, Pizzichemi M. TOF-PET Image Reconstruction With Multiple Timing Kernels Applied on Cherenkov Radiation in BGO. IEEE TRANSACTIONS ON RADIATION AND PLASMA MEDICAL SCIENCES 2020; 5:703-711. [PMID: 34541434 PMCID: PMC8445518 DOI: 10.1109/trpms.2020.3048642] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
Today Time-of-Flight (TOF), in PET scanners, assumes a single, well-defined timing resolution for all events. However, recent BGO-Cherenkov detectors, combining prompt Cherenkov emission and the typical BGO scintillation, can sort events into multiple timing kernels, best described by the Gaussian mixture models. The number of Cherenkov photons detected per event impacts directly the detector time resolution and signal rise time, which can later be used to improve the coincidence timing resolution. This work presents a simulation toolkit which applies multiple timing spreads on the coincident events and an image reconstruction that incorporates this information. A full cylindrical BGO-Cherenkov PET model was compared, in terms of contrast recovery and contrast-to-noise ratio, against an LYSO model with a time resolution of 213 ps. Two reconstruction approaches for the mixture kernels were tested: 1) mixture Gaussian and 2) decomposed simple Gaussian kernels. The decomposed model used the exact mixture component applied during the simulation. Images reconstructed using mixture kernels provided similar mean value and less noise than the decomposed. However, typically, more iterations were needed. Similarly, the LYSO model, with a single TOF kernel, converged faster than the BGO-Cherenkov with multiple kernels. The results indicate that the model complexity slows down convergence. However, due to the higher sensitivity, the contrast-to-noise ratio was 26.4% better for the BGO model.
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Affiliation(s)
- Nikos Efthimiou
- Department Radiology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA 19104 USA
| | | | - Stefan Gundacker
- Department of Physics of Molecular Imaging Systems, Institute for Experimental Molecular Imaging, RWTH Aachen University, 52062 Aachen, Germany
| | - Andrea Polesel
- Physics Department, University of Milano-Bicocca, 20126 Milan, Italy
| | - Matteo Salomoni
- Physics Department, University of Milano-Bicocca, 20126 Milan, Italy
| | | | - Marco Pizzichemi
- Physics Department, University of Milano-Bicocca, 20126 Milan, Italy
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Gustafsson J, Rodeño E, Mínguez P. Feasibility and limitations of quantitative SPECT for 223Ra. Phys Med Biol 2020; 65:085012. [PMID: 32092708 DOI: 10.1088/1361-6560/ab7971] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
Abstract
The aim of this paper is to investigate the feasibility and limitations of activity-concentration estimation for 223Ra using SPECT. Phantom measurements are performed using spheres (volumes 5.5 mL to 26.4 mL, concentrations 1.6 kBq mL-1 to 4.5 kBq mL-1). Furthermore, SPECT projections are simulated using the SIMIND Monte Carlo program for two geometries, one similar to the physical phantom and the other being an anthropomorphic phantom with added lesions (volumes 34 mL to 100 mL, concentrations 0.5 kBq mL-1 to 4 kBq mL-1). Medium-energy and high-energy collimators, 60 projections with 55 s per projection and a 20% energy window at 82 keV are employed. For the Monte Carlo simulated images, Poisson-distributed noise is added in ten noise realizations. Reconstruction is performed (OS-EM, 40 iterations, 6 subsets) employing compensation for attenuation, scatter, and collimator-detector response. The estimated concentrations in the anthropomorphic phantom are also corrected using recovery coefficients. Errors for the largest sphere in the physical phantom range from -25% to -34% for the medium-energy collimator and larger deviations for smaller spheres. Corresponding results for the high-energy collimator are -15% to -31%. The corresponding Monte Carlo simulations show standard deviations of a few percentage points. For the anthropomorphic phantom, before application of recovery coefficients the bias ranges from -16% to -46% (medium-energy collimator) and -10% to -28% (high-energy collimator), with standard deviations of 2% to 14% and 1% to 16%. After the application of recovery coefficients, the biases range from -3% to -35% (medium energy collimator) and from 0% to -18%. The errors decrease with increasing concentrations. Activity-concentration estimation of 223Ra with SPECT is feasible, but problems with repeatability need to be further studied.
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Affiliation(s)
- Johan Gustafsson
- Medical Radiation Physics, Clinical Sciences Lund, Lund University, Lund, Sweden
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Kunnen B, Beijst C, Lam MGEH, Viergever MA, de Jong HWAM. Comparison of the Biograph Vision and Biograph mCT for quantitative 90Y PET/CT imaging for radioembolisation. EJNMMI Phys 2020; 7:14. [PMID: 32130554 PMCID: PMC7056802 DOI: 10.1186/s40658-020-0283-6] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/06/2020] [Accepted: 02/20/2020] [Indexed: 12/13/2022] Open
Abstract
BACKGROUND New digital PET scanners with improved time of flight timing and extended axial field of view such as the Siemens Biograph Vision have come on the market and are expected to replace current generation photomultiplier tube (PMT)-based systems such as the Siemens Biograph mCT. These replacements warrant a direct comparison between the systems, so that a smooth transition in clinical practice and research is guaranteed, especially when quantitative values are used for dosimetry-based treatment guidance. The new generation digital PET scanners offer increased sensitivity. This could particularly benefit 90Y imaging, which tends to be very noisy owing to the small positron branching ratio and high random fraction of 90Y. This study aims to determine the ideal reconstruction settings for the digital Vision for quantitative 90Y imaging and to evaluate the image quality and quantification of the digital Vision in comparison with its predecessor, the PMT-based mCT, for 90Y imaging in radioembolisation procedures. METHODS The NEMA image quality phantom was scanned to determine the ideal reconstruction settings for the Vision. In addition, an anthropomorphic phantom was scanned with both the Vision and the mCT, mimicking a radioembolisation patient with lung, liver, tumour, and extrahepatic deposition inserts. Image quantification of the anthropomorphic phantom was assessed by the lung shunt fraction, the tumour to non-tumour ratio, the parenchymal dose, and the contrast to noise ratio of extrahepatic depositions. RESULTS For the Vision, a reconstruction with 3 iterations, 5 subsets, and no post-reconstruction filter is recommended for quantitative 90Y imaging, based on the convergence of the recovery coefficient. Comparing both systems showed that the noise level of the Vision is significantly lower than that of the mCT (background variability of 14% for the Vision and 25% for the mCT at 2.5·103 MBq for the 37 mm sphere size). For quantitative 90Y measures, such as needed in radioembolisation, both systems perform similarly. CONCLUSIONS We recommend to reconstruct 90Y images acquired on the Vision with 3 iterations, 5 subsets, and no post-reconstruction filter for quantitative imaging. The Vision provides a reduced noise level, but similar quantitative accuracy as compared with its predecessor the mCT.
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Affiliation(s)
- Britt Kunnen
- Department of Radiology and Nuclear Medicine, UMC Utrecht, P.O. Box 85500, GA 3508, Utrecht, the Netherlands.
- Image Sciences Institute, UMC Utrecht & University Utrecht, Heidelberglaan 100, CX 3584, Utrecht, the Netherlands.
| | - Casper Beijst
- Department of Radiology and Nuclear Medicine, UMC Utrecht, P.O. Box 85500, GA 3508, Utrecht, the Netherlands
| | - Marnix G E H Lam
- Department of Radiology and Nuclear Medicine, UMC Utrecht, P.O. Box 85500, GA 3508, Utrecht, the Netherlands
| | - Max A Viergever
- Image Sciences Institute, UMC Utrecht & University Utrecht, Heidelberglaan 100, CX 3584, Utrecht, the Netherlands
| | - Hugo W A M de Jong
- Department of Radiology and Nuclear Medicine, UMC Utrecht, P.O. Box 85500, GA 3508, Utrecht, the Netherlands
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Hallen P, Schug D, Schulz V. Comments on the NEMA NU 4-2008 Standard on Performance Measurement of Small Animal Positron Emission Tomographs. EJNMMI Phys 2020; 7:12. [PMID: 32095909 PMCID: PMC7040118 DOI: 10.1186/s40658-020-0279-2] [Citation(s) in RCA: 18] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/25/2019] [Accepted: 02/04/2020] [Indexed: 11/12/2022] Open
Abstract
The National Electrical Manufacturers Association’s (NEMA) NU 4-2008 standard specifies methodology for evaluating the performance of small-animal PET scanners. The standard’s goal is to enable comparison of different PET scanners over a wide range of technologies and geometries used. In this work, we discuss if the NEMA standard meets these goals and we point out potential flaws and improvements to the standard.For the evaluation of spatial resolution, the NEMA standard mandates the use of filtered backprojection reconstruction. This reconstruction method can introduce star-like artifacts for detectors with an anisotropic spatial resolution, usually caused by parallax error. These artifacts can then cause a strong dependence of the resulting spatial resolution on the size of the projection window in image space, whose size is not fully specified in the NEMA standard. If the PET ring has detectors which are perpendicular to a Cartesian axis, then the resolution along this axis will typically improve with larger projection windows.We show that the standard’s equations for the estimation of the random rate for PET systems with intrinsic radioactivity are circular and not satisfiable. However, a modified version can still be used to determine an approximation of the random rates under the assumption of negligible random rates for small activities and a constant scatter fraction. We compare the resulting estimated random rates to random rates obtained using a delayed coincidence window and two methods based on the singles rates. While these methods give similar estimates, the estimation method based on the NEMA equations overestimates the random rates.In the NEMA standard’s protocol for the evaluation of the sensitivity, the standard specifies to axially step a point source through the scanner and to take a different scan for each source position. Later, in the data analysis section, the standard does not specify clearly how the different scans have to be incorporated into the analysis, which can lead to unclear interpretations of publicized results.The standard’s definition of the recovery coefficients in the image quality phantom includes the maximum activity in a region of interest, which causes a positive correlation of noise and recovery coefficients. This leads to an unintended trade-off between desired uniformity, which is negatively correlated with variance (i.e., noise), and recovery.With this work, we want to start a discussion on possible improvements in a next version of the NEMA NU-4 standard.
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Affiliation(s)
- Patrick Hallen
- Department of Physics of Molecular Imaging Systems, Institute for Experimental Molecular Imaging, RWTH Aachen University, Pauwelstraße 19, Aachen, 52074, Germany.
| | - David Schug
- Department of Physics of Molecular Imaging Systems, Institute for Experimental Molecular Imaging, RWTH Aachen University, Pauwelstraße 19, Aachen, 52074, Germany.,Hyperion Hybrid Imaging Systems GmbH, Pauwelstraße 19, Aachen, 52074, Germany
| | - Volkmar Schulz
- Department of Physics of Molecular Imaging Systems, Institute for Experimental Molecular Imaging, RWTH Aachen University, Pauwelstraße 19, Aachen, 52074, Germany.,Hyperion Hybrid Imaging Systems GmbH, Pauwelstraße 19, Aachen, 52074, Germany.,III. Physikalisches Institut B, RWTH Aachen University, Otto-Blumenthal-Straße, Aachen, 52074, Germany.,Fraunhofer Institute for Digital Medicine MEVIS, Forckenbeckstrasse 55, Aachen, 52074, Germany
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Bousse A, Courdurier M, Emond E, Thielemans K, Hutton BF, Irarrazaval P, Visvikis D. PET Reconstruction With Non-Negativity Constraint in Projection Space: Optimization Through Hypo-Convergence. IEEE TRANSACTIONS ON MEDICAL IMAGING 2020; 39:75-86. [PMID: 31170066 DOI: 10.1109/tmi.2019.2920109] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
Standard positron emission tomography (PET) reconstruction techniques are based on maximum-likelihood (ML) optimization methods, such as the maximum-likelihood expectation-maximization (MLEM) algorithm and its variations. Most methodologies rely on a positivity constraint on the activity distribution image. Although this constraint is meaningful from a physical point of view, it can be a source of bias for low-count/high-background PET, which can compromise accurate quantification. Existing methods that allow for negative values in the estimated image usually utilize a modified log-likelihood, and therefore break the data statistics. In this paper, we propose to incorporate the positivity constraint on the projections only, by approximating the (penalized) log-likelihood function by an adequate sequence of objective functions that are easily maximized without constraint. This sequence is constructed such that there is hypo-convergence (a type of convergence that allows the convergence of the maximizers under some conditions) to the original log-likelihood, hence allowing us to achieve maximization with positivity constraint on the projections using simple settings. A complete proof of convergence under weak assumptions is given. We provide results of experiments on simulated data where we compare our methodology with the alternative direction method of multipliers (ADMM) method, showing that our algorithm converges to a maximizer, which stays in the desired feasibility set, with faster convergence than ADMM. We also show that this approach reduces the bias, as compared with MLEM images, in necrotic tumors-which are characterized by cold regions surrounded by hot structures-while reconstructing similar activity values in hot regions.
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Scipioni M, Santarelli MF, Giorgetti A, Positano V, Landini L. Negative binomial maximum likelihood expectation maximization (NB-MLEM) algorithm for reconstruction of pre-corrected PET data. Comput Biol Med 2019; 115:103481. [PMID: 31627018 DOI: 10.1016/j.compbiomed.2019.103481] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/26/2019] [Revised: 10/01/2019] [Accepted: 10/01/2019] [Indexed: 10/25/2022]
Abstract
PURPOSE Positron emission tomography (PET) image reconstruction is usually performed using maximum likelihood (ML) iterative reconstruction methods, under the assumption of Poisson distributed data. Pre-correcting raw measured counts, this assumption is no longer realistic. The goal of this work is to develop a reconstruction algorithm based on the Negative Binomial (NB) distribution, which can generalize over the Poisson distribution in case of over-dispersion of raw data, that may occur if sinogram pre-correction is used. METHODS The mathematical derivation of a Negative Binomial Maximum Likelihood Expectation-Maximization (NB-MLEM) algorithm is presented. A simulation study to compare the performance of the proposed NB-MLEM algorithm with respect to a Poisson-based MLEM (P-MLEM) method was performed, in reconstructing PET data. The proposed NB-MLEM reconstruction was tested on a real phantom and human brain data. RESULTS For the property of NB distribution, it is a generalization of the conventional P-MLEM: for not over dispersed data, the proposed NB-MLEM algorithm behaves like the conventional P-MLEM; for over-dispersed PET data, the additional evaluation of the dispersion parameter after each reconstruction iteration leads to a more accurate final image with respect to P-MLEM. CONCLUSIONS A novel approach for PET image reconstruction from pre-corrected data has been developed, which exhibits a statistical behavior that deviates from the Poisson distribution. Simulation study and preliminary tests on real data showed how the NB-MLEM algorithm, being able to explain the over-dispersion of pre-corrected data, can outperform other algorithms that assume no over-dispersion of pre-corrected data, while still not accounting for the presence of negative data, such as P-MLEM.
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Affiliation(s)
- Michele Scipioni
- Dipartimento di Ingegneria dell'Informazione, University of Pisa, Pisa, Italy; CNR Institute of Clinical Physiology, Via Moruzzi,1, 56124, Pisa, Italy
| | - Maria Filomena Santarelli
- CNR Institute of Clinical Physiology, Via Moruzzi,1, 56124, Pisa, Italy; Fondazione Toscana "G. Monasterio", Via Moruzzi,1, 56124, Pisa, Italy.
| | - Assuero Giorgetti
- Fondazione Toscana "G. Monasterio", Via Moruzzi,1, 56124, Pisa, Italy
| | - Vincenzo Positano
- Fondazione Toscana "G. Monasterio", Via Moruzzi,1, 56124, Pisa, Italy
| | - Luigi Landini
- Dipartimento di Ingegneria dell'Informazione, University of Pisa, Pisa, Italy; Fondazione Toscana "G. Monasterio", Via Moruzzi,1, 56124, Pisa, Italy
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Rahmim A, Lodge MA, Karakatsanis NA, Panin VY, Zhou Y, McMillan A, Cho S, Zaidi H, Casey ME, Wahl RL. Dynamic whole-body PET imaging: principles, potentials and applications. Eur J Nucl Med Mol Imaging 2018; 46:501-518. [PMID: 30269154 DOI: 10.1007/s00259-018-4153-6] [Citation(s) in RCA: 108] [Impact Index Per Article: 18.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/26/2018] [Accepted: 08/28/2018] [Indexed: 02/07/2023]
Abstract
PURPOSE In this article, we discuss dynamic whole-body (DWB) positron emission tomography (PET) as an imaging tool with significant clinical potential, in relation to conventional standard uptake value (SUV) imaging. BACKGROUND DWB PET involves dynamic data acquisition over an extended axial range, capturing tracer kinetic information that is not available with conventional static acquisition protocols. The method can be performed within reasonable clinical imaging times, and enables generation of multiple types of PET images with complementary information in a single imaging session. Importantly, DWB PET can be used to produce multi-parametric images of (i) Patlak slope (influx rate) and (ii) intercept (referred to sometimes as "distribution volume"), while also providing (iii) a conventional 'SUV-equivalent' image for certain protocols. RESULTS We provide an overview of ongoing efforts (primarily focused on FDG PET) and discuss potential clinically relevant applications. CONCLUSION Overall, the framework of DWB imaging [applicable to both PET/CT(computed tomography) and PET/MRI (magnetic resonance imaging)] generates quantitative measures that may add significant value to conventional SUV image-derived measures, with limited pitfalls as we also discuss in this work.
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Affiliation(s)
- Arman Rahmim
- Department of Radiology and Radiological Science, Johns Hopkins University, JHOC Building Room 3245, 601 N. Caroline St, Baltimore, MD, 21287, USA. .,Departments of Radiology and Physics & Astronomy, University of British Columbia, Vancouver, BC, V5Z 1M9, Canada.
| | - Martin A Lodge
- Department of Radiology and Radiological Science, Johns Hopkins University, JHOC Building Room 3245, 601 N. Caroline St, Baltimore, MD, 21287, USA
| | | | | | - Yun Zhou
- Department of Radiology and Radiological Science, Johns Hopkins University, JHOC Building Room 3245, 601 N. Caroline St, Baltimore, MD, 21287, USA
| | - Alan McMillan
- Department of Radiology, University of Wisconsin, Madison, WI, 53705, USA
| | - Steve Cho
- Department of Radiology, University of Wisconsin, Madison, WI, 53705, USA
| | - Habib Zaidi
- Division of Nuclear Medicine and Molecular Imaging, Geneva University Hospital, CH-1211, Geneva, Switzerland
| | | | - Richard L Wahl
- Mallinckrodt Institute of Radiology, Washington University School of Medicine, St. Louis, MO, 63110, USA
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14
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Kunnen B, van der Velden S, Bastiaannet R, Lam MGEH, Viergever MA, de Jong HWAM. Radioembolization lung shunt estimation based on a 90
Y pretreatment procedure: A phantom study. Med Phys 2018; 45:4744-4753. [DOI: 10.1002/mp.13168] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/29/2018] [Revised: 08/20/2018] [Accepted: 08/28/2018] [Indexed: 12/15/2022] Open
Affiliation(s)
- Britt Kunnen
- Radiology and Nuclear Medicine; UMC Utrecht; P.O. Box 85500 3508 GA Utrecht The Netherlands
- Image Sciences Institute; UMC Utrecht; University Utrecht; Heidelberglaan 100 3584 CX Utrecht The Netherlands
| | - Sandra van der Velden
- Radiology and Nuclear Medicine; UMC Utrecht; P.O. Box 85500 3508 GA Utrecht The Netherlands
- Image Sciences Institute; UMC Utrecht; University Utrecht; Heidelberglaan 100 3584 CX Utrecht The Netherlands
| | - Remco Bastiaannet
- Radiology and Nuclear Medicine; UMC Utrecht; P.O. Box 85500 3508 GA Utrecht The Netherlands
- Image Sciences Institute; UMC Utrecht; University Utrecht; Heidelberglaan 100 3584 CX Utrecht The Netherlands
| | - Marnix G. E. H. Lam
- Radiology and Nuclear Medicine; UMC Utrecht; P.O. Box 85500 3508 GA Utrecht The Netherlands
| | - Max A. Viergever
- Image Sciences Institute; UMC Utrecht; University Utrecht; Heidelberglaan 100 3584 CX Utrecht The Netherlands
| | - Hugo W. A. M. de Jong
- Radiology and Nuclear Medicine; UMC Utrecht; P.O. Box 85500 3508 GA Utrecht The Netherlands
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Merlin T, Stute S, Benoit D, Bert J, Carlier T, Comtat C, Filipovic M, Lamare F, Visvikis D. CASToR: a generic data organization and processing code framework for multi-modal and multi-dimensional tomographic reconstruction. ACTA ACUST UNITED AC 2018; 63:185005. [DOI: 10.1088/1361-6560/aadac1] [Citation(s) in RCA: 54] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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Lim H, Dewaraja YK, Fessler JA. A PET reconstruction formulation that enforces non-negativity in projection space for bias reduction in Y-90 imaging. Phys Med Biol 2018; 63:035042. [PMID: 29327692 PMCID: PMC5854483 DOI: 10.1088/1361-6560/aaa71b] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Most existing PET image reconstruction methods impose a nonnegativity constraint in the image domain that is natural physically, but can lead to biased reconstructions. This bias is particularly problematic for Y-90 PET because of the low probability positron production and high random coincidence fraction. This paper investigates a new PET reconstruction formulation that enforces nonnegativity of the projections instead of the voxel values. This formulation allows some negative voxel values, thereby potentially reducing bias. Unlike the previously reported NEG-ML approach that modifies the Poisson log-likelihood to allow negative values, the new formulation retains the classical Poisson statistical model. To relax the non-negativity constraint embedded in the standard methods for PET reconstruction, we used an alternating direction method of multipliers (ADMM). Because choice of ADMM parameters can greatly influence convergence rate, we applied an automatic parameter selection method to improve the convergence speed. We investigated the methods using lung to liver slices of XCAT phantom. We simulated low true coincidence count-rates with high random fractions corresponding to the typical values from patient imaging in Y-90 microsphere radioembolization. We compared our new methods with standard reconstruction algorithms and NEG-ML and a regularized version thereof. Both our new method and NEG-ML allow more accurate quantification in all volumes of interest while yielding lower noise than the standard method. The performance of NEG-ML can degrade when its user-defined parameter is tuned poorly, while the proposed algorithm is robust to any count level without requiring parameter tuning.
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Affiliation(s)
- Hongki Lim
- Department of Electrical Engineering and Computer Science, University of Michigan, Ann Arbor, MI 48109, United States of America. Department of Radiology, University of Michigan, Ann Arbor, MI 48109, United States of America
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Rank CM, Heußer T, Wetscherek A, Freitag MT, Sedlaczek O, Schlemmer HP, Kachelrieß M. Respiratory motion compensation for simultaneous PET/MR based on highly undersampled MR data. Med Phys 2017; 43:6234. [PMID: 27908174 DOI: 10.1118/1.4966128] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022] Open
Abstract
PURPOSE Positron emission tomography (PET) of the thorax region is impaired by respiratory patient motion. To account for motion, the authors propose a new method for PET/magnetic resonance (MR) respiratory motion compensation (MoCo), which uses highly undersampled MR data with acquisition times as short as 1 min/bed. METHODS The proposed PET/MR MoCo method (4D jMoCo PET) uses radial MR data to estimate the respiratory patient motion employing MR joint motion estimation and image reconstruction with temporal median filtering. Resulting motion vector fields are incorporated into the system matrix of the PET reconstruction. The proposed approach is evaluated for the thorax region utilizing a PET/MR simulation with 1 min MR acquisition time and simultaneous PET/MR measurements of six patients with MR acquisition times of 1 and 5 min and radial undersampling factors of 11.2 and 2.2, respectively. Reconstruction results are compared to 3D PET, 4D gated PET and a standard MoCo method (4D sMoCo PET), which performs iterative image reconstruction and motion estimation sequentially. Quantitative analysis comprises the parameters SUVmean, SUVmax, full width at half-maximum/lesion volume, contrast and signal-to-noise ratio. RESULTS For simulated PET data, our quantitative analysis shows that the proposed 4D jMoCo PET approach with temporal filtering achieves the best quantification accuracy of all tested reconstruction methods with a mean absolute deviation of 2.3% when compared to the ground truth. For measured PET patient data, the mean absolute deviation of 4D jMoCo PET using a 1 min MR acquisition for motion estimation is 2.1% relative to the 5 min MR acquisition. This demonstrates a robust behavior even in case of strong undersampling at MR acquisition times as short as 1 min. In contrast, 4D sMoCo PET shows considerable reduction of quantification accuracy for the 1 min MR acquisition time. Relative to 3D PET, the proposed 4D jMoCo PET approach with temporal filtering yields an average increase of SUVmean, SUVmax, and contrast of 29.9% and 13.8% for simulated and measured PET data, respectively. CONCLUSIONS Employing artifact-robust motion estimation enables PET/MR respiratory MoCo with MR acquisition times as short as 1 min/bed improving PET image quality and quantification accuracy.
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Affiliation(s)
- Christopher M Rank
- Medical Physics in Radiology, German Cancer Research Center (DKFZ), Im Neuenheimer Feld 280, 69120 Heidelberg, Germany
| | - Thorsten Heußer
- Medical Physics in Radiology, German Cancer Research Center (DKFZ), Im Neuenheimer Feld 280, 69120 Heidelberg, Germany
| | - Andreas Wetscherek
- Medical Physics in Radiology, German Cancer Research Center (DKFZ), Im Neuenheimer Feld 280, 69120 Heidelberg, Germany and Joint Department of Physics, The Institute of Cancer Research and The Royal Marsden NHS Foundation Trust, 123 Old Brompton Road, London SW7 3RP, United Kingdom
| | - Martin T Freitag
- Radiology, German Cancer Research Center (DKFZ), Im Neuenheimer Feld 280, 69120 Heidelberg, Germany
| | - Oliver Sedlaczek
- Radiology, German Cancer Research Center (DKFZ), Im Neuenheimer Feld 280, 69120 Heidelberg, Germany
| | - Heinz-Peter Schlemmer
- Radiology, German Cancer Research Center (DKFZ), Im Neuenheimer Feld 280, 69120 Heidelberg, Germany
| | - Marc Kachelrieß
- Medical Physics in Radiology, German Cancer Research Center (DKFZ), Im Neuenheimer Feld 280, 69120 Heidelberg, Germany
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18
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Strydhorst J, Carlier T, Dieudonné A, Conti M, Buvat I. A gate evaluation of the sources of error in quantitative 90 Y PET. Med Phys 2017; 43:5320-5329. [PMID: 28105711 DOI: 10.1118/1.4961747] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/2016] [Revised: 07/28/2016] [Accepted: 08/13/2016] [Indexed: 01/08/2023] Open
Abstract
PURPOSE Accurate reconstruction of the dose delivered by 90 Y microspheres using a postembolization PET scan would permit the establishment of more accurate dose-response relationships for treatment of hepatocellular carcinoma with 90 Y. However, the quality of the PET data obtained is compromised by several factors, including poor count statistics and a very high random fraction. This work uses Monte Carlo simulations to investigate what impact factors other than low count statistics have on the quantification of90 Y PET. METHODS PET acquisitions of two phantoms-a NEMA PET phantom and the NEMA IEC PET body phantom-containing either 90 Y or 18 F were simulated using gate. Simulated projections were created with subsets of the simulation data allowing the contributions of random, scatter, and LSO background to be independently evaluated. The simulated projections were reconstructed using the commercial software for the simulated scanner, and the quantitative accuracy of the reconstruction and the contrast recovery of the reconstructed images were evaluated. RESULTS The quantitative accuracy of the 90 Y reconstructions were not strongly influenced by the high random fraction present in the projection data, and the activity concentration was recovered to within 5% of the known value. The contrast recovery measured for simulated 90 Y data was slightly poorer than that for simulated 18 F data with similar count statistics. However, the degradation was not strongly linked to any particular factor. Using a more restricted energy range to reduce the random fraction in the projections had no significant effect. CONCLUSIONS Simulations of 90 Y PET confirm that quantitative 90 Y is achievable with the same approach as that used for 18 F, and that there is likely very little margin for improvement by attempting to model aspects unique to 90 Y, such as the much higher random fraction or the presence of bremsstrahlung in the singles data.
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Affiliation(s)
- Jared Strydhorst
- IMIV, U1023 Inserm/CEA/Université Paris-Sud and ERL 9218 CNRS, Université Paris-Saclay, CEA/SHFJ, Orsay 91401, France
| | - Thomas Carlier
- Department of Nuclear Medicine, Centre Hospitalier Universitaire de Nantes and CRCNA, Inserm U892, Nantes 44000, France
| | - Arnaud Dieudonné
- Department of Nuclear Medicine, Hôpital Beaujon, HUPNVS, APHP and Inserm U1149, Clichy 92110, France
| | - Maurizio Conti
- Siemens Healthcare Molecular Imaging, Knoxville, Tennessee, 37932
| | - Irène Buvat
- IMIV, U1023 Inserm/CEA/Université Paris-Sud and ERL 9218 CNRS, Université Paris-Saclay, CEA/SHFJ, Orsay 91401, France
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19
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Slomka PJ, Alessio AM, Germano G. How to reconstruct dynamic cardiac PET data? J Nucl Cardiol 2017; 24:291-293. [PMID: 27473215 DOI: 10.1007/s12350-016-0608-y] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/11/2016] [Accepted: 07/11/2016] [Indexed: 10/21/2022]
Affiliation(s)
- Piotr J Slomka
- Department of Medicine, Cedars-Sinai Medical Center, Los Angeles, CA, USA.
- David Geffen School of Medicine, UCLA, Los Angeles, CA, USA.
| | - Adam M Alessio
- Department of Radiology, University of Washington, Seattle, WA, USA
| | - Guido Germano
- Department of Medicine, Cedars-Sinai Medical Center, Los Angeles, CA, USA
- David Geffen School of Medicine, UCLA, Los Angeles, CA, USA
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20
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Habert MO, Marie S, Bertin H, Reynal M, Martini JB, Diallo M, Kas A, Trébossen R. Optimization of brain PET imaging for a multicentre trial: the French CATI experience. EJNMMI Phys 2016; 3:6. [PMID: 27044410 PMCID: PMC4820434 DOI: 10.1186/s40658-016-0141-8] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/11/2015] [Accepted: 02/09/2016] [Indexed: 11/10/2022] Open
Abstract
Background CATI is a French initiative launched in 2010 to handle the neuroimaging of a large cohort of subjects recruited for an Alzheimer’s research program called MEMENTO. This paper presents our test protocol and results obtained for the 22 PET centres (overall 13 different scanners) involved in the MEMENTO cohort. We determined acquisition parameters using phantom experiments prior to patient studies, with the aim of optimizing PET quantitative values to the highest possible per site, while reducing, if possible, variability across centres. Methods Jaszczak’s and 3D-Hoffman’s phantom measurements were used to assess image spatial resolution (ISR), recovery coefficients (RC) in hot and cold spheres, and signal-to-noise ratio (SNR). For each centre, the optimal reconstruction parameters were chosen as those maximizing ISR and RC without a noticeable decrease in SNR. Point-spread-function (PSF) modelling reconstructions were discarded. The three figures of merit extracted from the images reconstructed with optimized parameters and routine schemes were compared, as were volumes of interest ratios extracted from Hoffman acquisitions. The net effect of the 3D-OSEM reconstruction parameter optimization was investigated on a subset of 18 scanners without PSF modelling reconstruction. Results Compared to the routine parameters of the 22 PET centres, average RC in the two smallest hot and cold spheres and average ISR remained stable or were improved with the optimized reconstruction, at the expense of slight SNR degradation, while the dispersion of values was reduced. For the subset of scanners without PSF modelling, the mean RC of the smallest hot sphere obtained with the optimized reconstruction was significantly higher than with routine reconstruction. The putamen and caudate-to-white matter ratios measured on 3D-Hoffman acquisitions of all centres were also significantly improved by the optimization, while the variance was reduced. Conclusions This study provides guidelines for optimizing quantitative results for multicentric PET neuroimaging trials.
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Affiliation(s)
- Marie-Odile Habert
- Sorbonne Universités, UPMC Univ Paris 06, CNRS, INSERM, Laboratoire d'Imagerie Biomédicale, F-75013, Paris, France. .,Centre pour l'Acquisition et le Traitement des Images (www.cati-neuroimaging.com), Paris, France. .,AP-HP, Hôpital Pitié-Salpêtrière, Département de Médecine Nucléaire, F-75013, Paris, France. .,Faculté de Médecine - Laboratoire d'Imagerie Biomédicale, 91 Boulevard de l'Hôpital, F-75013, Paris, France.
| | - Sullivan Marie
- Sorbonne Universités, UPMC Univ Paris 06, CNRS, INSERM, Laboratoire d'Imagerie Biomédicale, F-75013, Paris, France.,Centre pour l'Acquisition et le Traitement des Images (www.cati-neuroimaging.com), Paris, France
| | - Hugo Bertin
- Sorbonne Universités, UPMC Univ Paris 06, CNRS, INSERM, Laboratoire d'Imagerie Biomédicale, F-75013, Paris, France.,Centre pour l'Acquisition et le Traitement des Images (www.cati-neuroimaging.com), Paris, France
| | - Moana Reynal
- Sorbonne Universités, UPMC Univ Paris 06, CNRS, INSERM, Laboratoire d'Imagerie Biomédicale, F-75013, Paris, France.,Centre pour l'Acquisition et le Traitement des Images (www.cati-neuroimaging.com), Paris, France
| | - Jean-Baptiste Martini
- Sorbonne Universités, UPMC Univ Paris 06, CNRS, INSERM, Laboratoire d'Imagerie Biomédicale, F-75013, Paris, France.,Centre pour l'Acquisition et le Traitement des Images (www.cati-neuroimaging.com), Paris, France
| | - Mamadou Diallo
- Sorbonne Universités, UPMC Univ Paris 06, CNRS, INSERM, Laboratoire d'Imagerie Biomédicale, F-75013, Paris, France.,Centre pour l'Acquisition et le Traitement des Images (www.cati-neuroimaging.com), Paris, France
| | - Aurélie Kas
- Sorbonne Universités, UPMC Univ Paris 06, CNRS, INSERM, Laboratoire d'Imagerie Biomédicale, F-75013, Paris, France.,Centre pour l'Acquisition et le Traitement des Images (www.cati-neuroimaging.com), Paris, France.,AP-HP, Hôpital Pitié-Salpêtrière, Département de Médecine Nucléaire, F-75013, Paris, France
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Grafström J, Ahlzén HS, Stone-Elander S. A method for comparing intra-tumoural radioactivity uptake heterogeneity in preclinical positron emission tomography studies. EJNMMI Phys 2015; 2:19. [PMID: 26501820 PMCID: PMC4562910 DOI: 10.1186/s40658-015-0124-1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/11/2015] [Accepted: 08/31/2015] [Indexed: 11/29/2022] Open
Abstract
Background Non-uniformity influences the interpretation of nuclear medicine based images and consequently their use in treatment planning and monitoring. However, no standardised method for evaluating and ranking heterogeneity exists. Here, we have developed a general algorithm that provides a ranking and a visualisation of the heterogeneity in small animal positron emission tomography (PET) images. Methods The code of the algorithm was written using the Matrix Laboratory software (MATLAB). Parameters known to influence the heterogeneity (distances between deviating peaks, gradients and size compensations) were incorporated into the algorithm. All data matrices were mathematically constructed in the same format with the aim of maintaining overview and control. Histograms visualising the spread and frequency of contributions to the heterogeneity were also generated. The construction of the algorithm was tested using mathematically generated matrices and by varying post-processing parameters. It was subsequently applied in comparisons of radiotracer uptake in preclinical images in human head and neck carcinoma and endothelial and ovarian carcinoma xenografts. Results Using the developed algorithm, entire tissue volumes could be assessed and gradients could be handled in an indirect manner. Similar-sized volumes could be compared without modifying the algorithm. Analyses of the distribution of different tracers gave results that were generally in accordance with single plane preclinical images, indicating that it could appropriately handle comparisons of targeting vs. non-targeting tracers and also for different target levels. Altering the reconstruction algorithm, pixel size, tumour ROI volumes and lower cut-off limits affected the calculated heterogeneity factors in expected directions but did not reverse conclusions about which tumour was more or less heterogeneous. Conclusions The algorithm constructed is an objective and potentially user-friendly tool for one-to-one comparisons of heterogeneity in whole similar-sized tumour volumes in PET imaging.
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Affiliation(s)
| | - Hanna-Stina Ahlzén
- Division of Biochemistry, Department of Medical Biochemistry and Biophysics, Karolinska Institutet, SE-17177, Stockholm, Sweden.
| | - Sharon Stone-Elander
- Department of Clinical Neuroscience, Karolinska Institutet, SE-17176, Stockholm, Sweden. .,PET Radiochemistry, Neuroradiology Department, Karolinska University Hospital, SE-17176, Stockholm, Sweden.
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