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Kroll T, Miranda A, Drechsel A, Beer S, Lang M, Drzezga A, Rosa-Neto P, Verhaeghe J, Elmenhorst D, Bauer A. Dynamic neuroreceptor positron emission tomography in non-anesthetized rats using point source based motion correction: A feasibility study with [ 11C]ABP688. J Cereb Blood Flow Metab 2024:271678X241239133. [PMID: 38684219 DOI: 10.1177/0271678x241239133] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 05/02/2024]
Abstract
To prevent motion artifacts in small animal positron emission tomography (PET), animals are routinely scanned under anesthesia or physical restraint. Both may potentially alter metabolism and neurochemistry. This study investigates the feasibility of fully awake acquisition and subsequent absolute quantification of dynamic brain PET data via pharmacokinetic modelling in moving rats using the glutamate 5 receptor radioligand [11C]ABP688 and point source based motion correction. Five male rats underwent three dynamic [11C]ABP688 PET scans: two test-retest awake PET scans and one scan under anesthesia for comparison. Specific radioligand binding was determined via the simplified reference tissue model (reference: cerebellum) and outcome parameters BPND and R1 were evaluated in terms of stability and reproducibility. Test-retest measurements in awake animals gave reliable results with high correlations of BPND (y = 1.08 × -0.2, r = 0.99, p < 0.01) and an acceptable variability (mean over all investigated regions 15.7 ± 2.4%). Regional [11C]ABP688 BPNDs under awake and anesthetized conditions were comparable although in awake scans, absolute radioactive peak uptakes were lower and relative blood flow in terms of R1 was higher. Awake small animal PET with absolute quantification of neuroreceptor availability is technically feasible and reproducible thereby providing a suitable alternative whenever effects of anesthesia are undesirable, e.g. in sleep research.
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Affiliation(s)
- Tina Kroll
- Institute of Neurosciences and Medicine (INM-2), Forschungszentrum Jülich GmbH, Germany
| | - Alan Miranda
- Molecular Imaging Center Antwerp, University of Antwerp, Belgium
| | - Alexandra Drechsel
- Institute of Neurosciences and Medicine (INM-2), Forschungszentrum Jülich GmbH, Germany
| | - Simone Beer
- Institute of Neurosciences and Medicine (INM-2), Forschungszentrum Jülich GmbH, Germany
| | - Markus Lang
- Institute of Neurosciences and Medicine (INM-5), Forschungszentrum Jülich GmbH, Germany
| | - Alexander Drzezga
- Institute of Neurosciences and Medicine (INM-2), Forschungszentrum Jülich GmbH, Germany
- Department of Nuclear Medicine, University Hospital Cologne, Germany
- German Center for Neurodegenerative Diseases (DZNE), Bonn-Cologne, Germany
| | - Pedro Rosa-Neto
- Translational Neuroimaging Laboratory, McGill University Research Centre for Studies in Aging, Alzheimer's Disease Research Unit, Douglas Research Institute, Le Centre intégré universitaire de santé et de services sociaux (CIUSSS) de l'Ouest-de-l'Île-de-Montréal; Department of Neurology and Neurosurgery, Psychiatry and Pharmacology and Therapeutics, McGill University, Montreal, Canada
| | - Jeroen Verhaeghe
- Molecular Imaging Center Antwerp, University of Antwerp, Belgium
| | - David Elmenhorst
- Institute of Neurosciences and Medicine (INM-2), Forschungszentrum Jülich GmbH, Germany
- Department of Nuclear Medicine, University Hospital Cologne, Germany
| | - Andreas Bauer
- Institute of Neurosciences and Medicine (INM-2), Forschungszentrum Jülich GmbH, Germany
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Rodríguez-Sevilla P, Marin R, Ximendes E, del Rosal B, Benayas A, Jaque D. Luminescence Thermometry for Brain Activity Monitoring: A Perspective. Front Chem 2022; 10:941861. [PMID: 35903194 PMCID: PMC9315374 DOI: 10.3389/fchem.2022.941861] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/11/2022] [Accepted: 06/22/2022] [Indexed: 11/13/2022] Open
Abstract
Minimally invasive monitoring of brain activity is essential not only to gain understanding on the working principles of the brain, but also for the development of new diagnostic tools. In this perspective we describe how brain thermometry could be an alternative to conventional methods (e.g., magnetic resonance or nuclear medicine) for the acquisition of thermal images of the brain with enough spatial and temperature resolution to track brain activity in minimally perturbed animals. We focus on the latest advances in transcranial luminescence thermometry introducing a critical discussion on its advantages and shortcomings. We also anticipate the main challenges that the application of luminescent nanoparticles for brain thermometry will face in next years. With this work we aim to promote the development of near infrared luminescence for brain activity monitoring, which could also benefit other research areas dealing with the brain and its illnesses.
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Affiliation(s)
- Paloma Rodríguez-Sevilla
- Departamento de Física de Materiales, Nanomaterials for Bioimaging Group (NanoBIG), Facultad de Ciencias, Universidad Autónoma de Madrid, Madrid, Spain
- Nanomaterials for Bioimaging Group (NanoBIG), Instituto Ramón y Cajal de Investigación Sanitaria (IRYCIS), Hospital Ramón y Cajal, Madrid, Spain
| | - Riccardo Marin
- Departamento de Física de Materiales, Nanomaterials for Bioimaging Group (NanoBIG), Facultad de Ciencias, Universidad Autónoma de Madrid, Madrid, Spain
| | - Erving Ximendes
- Departamento de Física de Materiales, Nanomaterials for Bioimaging Group (NanoBIG), Facultad de Ciencias, Universidad Autónoma de Madrid, Madrid, Spain
- Nanomaterials for Bioimaging Group (NanoBIG), Instituto Ramón y Cajal de Investigación Sanitaria (IRYCIS), Hospital Ramón y Cajal, Madrid, Spain
| | | | - Antonio Benayas
- Departamento de Física de Materiales, Nanomaterials for Bioimaging Group (NanoBIG), Facultad de Ciencias, Universidad Autónoma de Madrid, Madrid, Spain
- Nanomaterials for Bioimaging Group (NanoBIG), Instituto Ramón y Cajal de Investigación Sanitaria (IRYCIS), Hospital Ramón y Cajal, Madrid, Spain
| | - Daniel Jaque
- Departamento de Física de Materiales, Nanomaterials for Bioimaging Group (NanoBIG), Facultad de Ciencias, Universidad Autónoma de Madrid, Madrid, Spain
- Nanomaterials for Bioimaging Group (NanoBIG), Instituto Ramón y Cajal de Investigación Sanitaria (IRYCIS), Hospital Ramón y Cajal, Madrid, Spain
- *Correspondence: Daniel Jaque,
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Kyme AZ, Fulton RR. Motion estimation and correction in SPECT, PET and CT. Phys Med Biol 2021; 66. [PMID: 34102630 DOI: 10.1088/1361-6560/ac093b] [Citation(s) in RCA: 21] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/13/2020] [Accepted: 06/08/2021] [Indexed: 11/11/2022]
Abstract
Patient motion impacts single photon emission computed tomography (SPECT), positron emission tomography (PET) and X-ray computed tomography (CT) by giving rise to projection data inconsistencies that can manifest as reconstruction artifacts, thereby degrading image quality and compromising accurate image interpretation and quantification. Methods to estimate and correct for patient motion in SPECT, PET and CT have attracted considerable research effort over several decades. The aims of this effort have been two-fold: to estimate relevant motion fields characterizing the various forms of voluntary and involuntary motion; and to apply these motion fields within a modified reconstruction framework to obtain motion-corrected images. The aims of this review are to outline the motion problem in medical imaging and to critically review published methods for estimating and correcting for the relevant motion fields in clinical and preclinical SPECT, PET and CT. Despite many similarities in how motion is handled between these modalities, utility and applications vary based on differences in temporal and spatial resolution. Technical feasibility has been demonstrated in each modality for both rigid and non-rigid motion, but clinical feasibility remains an important target. There is considerable scope for further developments in motion estimation and correction, and particularly in data-driven methods that will aid clinical utility. State-of-the-art machine learning methods may have a unique role to play in this context.
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Affiliation(s)
- Andre Z Kyme
- School of Biomedical Engineering, The University of Sydney, Sydney, New South Wales, AUSTRALIA
| | - Roger R Fulton
- Sydney School of Health Sciences, The University of Sydney, Sydney, New South Wales, AUSTRALIA
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Abstract
Positron emission tomography (PET) is a non-invasive imaging technology employed to describe metabolic, physiological, and biochemical processes in vivo. These include receptor availability, metabolic changes, neurotransmitter release, and alterations of gene expression in the brain. Since the introduction of dedicated small-animal PET systems along with the development of many novel PET imaging probes, the number of PET studies using rats and mice in basic biomedical research tremendously increased over the last decade. This article reviews challenges and advances of quantitative rodent brain imaging to make the readers aware of its physical limitations, as well as to inspire them for its potential applications in preclinical research. In the first section, we briefly discuss the limitations of small-animal PET systems in terms of spatial resolution and sensitivity and point to possible improvements in detector development. In addition, different acquisition and post-processing methods used in rodent PET studies are summarized. We further discuss factors influencing the test-retest variability in small-animal PET studies, e.g., different receptor quantification methodologies which have been mainly translated from human to rodent receptor studies to determine the binding potential and changes of receptor availability and radioligand affinity. We further review different kinetic modeling approaches to obtain quantitative binding data in rodents and PET studies focusing on the quantification of endogenous neurotransmitter release using pharmacological interventions. While several studies have focused on the dopamine system due to the availability of several PET tracers which are sensitive to dopamine release, other neurotransmitter systems have become more and more into focus and are described in this review, as well. We further provide an overview of latest genome engineering technologies, including the CRISPR/Cas9 and DREADD systems that may advance our understanding of brain disorders and function and how imaging has been successfully applied to animal models of human brain disorders. Finally, we review the strengths and opportunities of simultaneous PET/magnetic resonance imaging systems to study drug-receptor interactions and challenges for the translation of PET results from bench to bedside.
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Miyaoka RS, Lehnert A. Small animal PET: a review of what we have done and where we are going. Phys Med Biol 2020; 65. [PMID: 32357344 DOI: 10.1088/1361-6560/ab8f71] [Citation(s) in RCA: 27] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/10/2019] [Accepted: 05/01/2020] [Indexed: 02/07/2023]
Abstract
Small animal research is an essential tool in studying both pharmaceutical biodistributions and disease progression over time. Furthermore, through the rapid development of in vivo imaging technology over the last few decades, small animal imaging (also referred to as preclinical imaging) has become a mainstay for all fields of biologic research and a center point for most preclinical cancer research. Preclinical imaging modalities include optical, MRI and MRS, microCT, small animal PET, ultrasound, and photoacoustic, each with their individual strengths. The strong points of small animal PET are its translatability to the clinic; its quantitative imaging capabilities; its whole-body imaging ability to dynamically trace functional/biochemical processes; its ability to provide useful images with only nano- to pico‑ molar concentrations of administered compounds; and its ability to study animals serially over time. This review paper gives an overview of the development and evolution of small animal PET imaging. It provides an overview of detector designs; system configurations; multimodality PET imaging systems; image reconstruction and analysis tools; and an overview of research and commercially available small animal PET systems. It concludes with a look toward developing technologies/methodologies that will further enhance the impact of small animal PET imaging on medical research in the future.
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Affiliation(s)
- Robert S Miyaoka
- Radiology, University of Washington, Seattle, Washington, UNITED STATES
| | - Adrienne Lehnert
- Radiology, University of Washington, Seattle, Washington, UNITED STATES
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7
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Abbas W, Masip Rodo D. Computer Methods for Automatic Locomotion and Gesture Tracking in Mice and Small Animals for Neuroscience Applications: A Survey. SENSORS (BASEL, SWITZERLAND) 2019; 19:E3274. [PMID: 31349617 PMCID: PMC6696321 DOI: 10.3390/s19153274] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 05/31/2019] [Revised: 07/19/2019] [Accepted: 07/21/2019] [Indexed: 01/07/2023]
Abstract
Neuroscience has traditionally relied on manually observing laboratory animals in controlled environments. Researchers usually record animals behaving freely or in a restrained manner and then annotate the data manually. The manual annotation is not desirable for three reasons; (i) it is time-consuming, (ii) it is prone to human errors, and (iii) no two human annotators will 100% agree on annotation, therefore, it is not reproducible. Consequently, automated annotation for such data has gained traction because it is efficient and replicable. Usually, the automatic annotation of neuroscience data relies on computer vision and machine learning techniques. In this article, we have covered most of the approaches taken by researchers for locomotion and gesture tracking of specific laboratory animals, i.e. rodents. We have divided these papers into categories based upon the hardware they use and the software approach they take. We have also summarized their strengths and weaknesses.
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Affiliation(s)
- Waseem Abbas
- Multimedia and Telecommunications Department, Universitat Oberta de Catalunya, 08018 Barcelona, Spain.
| | - David Masip Rodo
- Multimedia and Telecommunications Department, Universitat Oberta de Catalunya, 08018 Barcelona, Spain
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8
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Angelis GI, Gillam JE, Ryder WJ, Fulton RR, Meikle SR. Direct Estimation of Voxel-Wise Neurotransmitter Response Maps From Dynamic PET Data. IEEE TRANSACTIONS ON MEDICAL IMAGING 2019; 38:1371-1383. [PMID: 30507497 DOI: 10.1109/tmi.2018.2883756] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
Computational methods, such as the linear parametric neurotransmitter PET (lp-ntPET) method, have been developed to characterize the transient changes in radiotracer kinetics in the target tissue during endogenous neurotransmitter release. In this paper, we describe and evaluate a parametric reconstruction algorithm that uses an expectation maximization framework, along with the lp-ntPET model, to estimate the endogenous neurotransmitter response to stimuli directly from the measured PET data. Computer simulations showed that the proposed direct reconstruction method offers improved accuracy and precision for the estimated timing parameters of the neurotransmitter response at the voxel level ( td=1±2 min, for activation onset bias and standard deviation) compared with conventional post reconstruction modeling ( td=4±7 min). In addition, we applied the proposed direct parameter estimation methodology to a [11C]raclopride displacement study of an awake rat and generated parametric maps illustrating the magnitude of ligand displacement from striatum. Although the estimated parametric maps of activation magnitude obtained from both direct and post reconstruction methodologies suffered from false positive activations, the proposed direct reconstruction framework offered more reliable parametric maps when the activation onset parameter was constrained.
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9
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Kyme AZ, Angelis GI, Eisenhuth J, Fulton RR, Zhou V, Hart G, Popovic K, Akhtar M, Ryder WJ, Clemens KJ, Balleine BW, Parmar A, Pascali G, Perkins G, Meikle SR. Open-field PET: Simultaneous brain functional imaging and behavioural response measurements in freely moving small animals. Neuroimage 2018; 188:92-101. [PMID: 30502443 DOI: 10.1016/j.neuroimage.2018.11.051] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/24/2018] [Revised: 11/01/2018] [Accepted: 11/27/2018] [Indexed: 10/27/2022] Open
Abstract
A comprehensive understanding of how the brain responds to a changing environment requires techniques capable of recording functional outputs at the whole-brain level in response to external stimuli. Positron emission tomography (PET) is an exquisitely sensitive technique for imaging brain function but the need for anaesthesia to avoid motion artefacts precludes concurrent behavioural response studies. Here, we report a technique that combines motion-compensated PET with a robotically-controlled animal enclosure to enable simultaneous brain imaging and behavioural recordings in unrestrained small animals. The technique was used to measure in vivo displacement of [11C]raclopride from dopamine D2 receptors (D2R) concurrently with changes in the behaviour of awake, freely moving rats following administration of unlabelled raclopride or amphetamine. The timing and magnitude of [11C]raclopride displacement from D2R were reliably estimated and, in the case of amphetamine, these changes coincided with a marked increase in stereotyped behaviours and hyper-locomotion. The technique, therefore, allows simultaneous measurement of changes in brain function and behavioural responses to external stimuli in conscious unrestrained animals, giving rise to important applications in behavioural neuroscience.
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Affiliation(s)
- Andre Z Kyme
- Biomedical Engineering, School of Aerospace, Mechanical & Mechatronic Engineering, Faculty of Engineering and IT, The University of Sydney, Sydney, NSW, 2006, Australia; Imaging Physics Laboratory, Brain and Mind Centre, The University of Sydney, Sydney, NSW, 2006, Australia; Faculty of Health Sciences, The University of Sydney, Sydney, NSW, 2006, Australia.
| | - Georgios I Angelis
- Imaging Physics Laboratory, Brain and Mind Centre, The University of Sydney, Sydney, NSW, 2006, Australia; Faculty of Health Sciences, The University of Sydney, Sydney, NSW, 2006, Australia
| | - John Eisenhuth
- Faculty of Health Sciences, The University of Sydney, Sydney, NSW, 2006, Australia
| | - Roger R Fulton
- Imaging Physics Laboratory, Brain and Mind Centre, The University of Sydney, Sydney, NSW, 2006, Australia; Faculty of Health Sciences, The University of Sydney, Sydney, NSW, 2006, Australia; Department of Medical Physics, Westmead Hospital, Sydney, NSW, 2145, Australia
| | - Victor Zhou
- Imaging Physics Laboratory, Brain and Mind Centre, The University of Sydney, Sydney, NSW, 2006, Australia
| | - Genevra Hart
- Brain and Mind Centre, The University of Sydney, Sydney, NSW, 2006, Australia
| | - Kata Popovic
- Imaging Physics Laboratory, Brain and Mind Centre, The University of Sydney, Sydney, NSW, 2006, Australia; Faculty of Health Sciences, The University of Sydney, Sydney, NSW, 2006, Australia
| | - Mahmood Akhtar
- Imaging Physics Laboratory, Brain and Mind Centre, The University of Sydney, Sydney, NSW, 2006, Australia; Faculty of Health Sciences, The University of Sydney, Sydney, NSW, 2006, Australia
| | - William J Ryder
- Imaging Physics Laboratory, Brain and Mind Centre, The University of Sydney, Sydney, NSW, 2006, Australia; Faculty of Health Sciences, The University of Sydney, Sydney, NSW, 2006, Australia
| | - Kelly J Clemens
- School of Psychology, University of New South Wales, Sydney, NSW, 2052, Australia
| | - Bernard W Balleine
- Brain and Mind Centre, The University of Sydney, Sydney, NSW, 2006, Australia
| | - Arvind Parmar
- Imaging Physics Laboratory, Brain and Mind Centre, The University of Sydney, Sydney, NSW, 2006, Australia; Australian Nuclear Science and Technology Organisation, Sydney, NSW, 2234, Australia
| | - Giancarlo Pascali
- Imaging Physics Laboratory, Brain and Mind Centre, The University of Sydney, Sydney, NSW, 2006, Australia; Australian Nuclear Science and Technology Organisation, Sydney, NSW, 2234, Australia
| | - Gary Perkins
- Australian Nuclear Science and Technology Organisation, Sydney, NSW, 2234, Australia
| | - Steven R Meikle
- Imaging Physics Laboratory, Brain and Mind Centre, The University of Sydney, Sydney, NSW, 2006, Australia; Faculty of Health Sciences, The University of Sydney, Sydney, NSW, 2006, Australia
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10
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Miranda A, Glorie D, Bertoglio D, Vleugels J, De Bruyne G, Stroobants S, Staelens S, Verhaeghe J. Awake 18F-FDG PET Imaging of Memantine-Induced Brain Activation and Test-Retest in Freely Running Mice. J Nucl Med 2018; 60:844-850. [PMID: 30442754 PMCID: PMC6581220 DOI: 10.2967/jnumed.118.218669] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/06/2018] [Accepted: 11/05/2018] [Indexed: 11/16/2022] Open
Abstract
PET scans of the mouse brain are usually performed with anesthesia to immobilize the animal. However, it is desirable to avoid the confounding factor of anesthesia in mouse-brain response. Methods: We developed and validated brain PET imaging of awake, freely moving mice. Head-motion tracking was performed using radioactive point-source markers, and we used the tracking information for PET-image motion correction. Regional 18F-FDG brain uptake in a test, retest, and memantine-challenge study was measured in awake (n = 8) and anesthetized (n = 8) C57BL/6 mice. An awake uptake period was considered for the anesthesia scans. Results: Awake (motion-corrected) PET images showed an 18F-FDG uptake pattern comparable to the pattern of anesthetized mice. The test–retest variability (represented by the intraclass correlation coefficient) of the regional SUV quantification in the awake animals (0.424–0.555) was marginally lower than that in the anesthetized animals (intraclass correlation coefficient, 0.491–0.629) over the different regions. The increased memantine-induced 18F-FDG uptake was more pronounced in awake (+63.6%) than in anesthetized (+24.2%) animals. Additional behavioral information, acquired for awake animals, showed increased motor activity on a memantine challenge (total distance traveled, 18.2 ± 5.28 m) compared with test–retest (6.49 ± 2.21 m). Conclusion: The present method enables brain PET imaging on awake mice, thereby avoiding the confounding effects of anesthesia on the PET reading. It allows the simultaneous measurement of behavioral information during PET acquisitions. The method does not require any additional hardware, and it can be deployed in typical high-throughput scan protocols.
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Affiliation(s)
- Alan Miranda
- Molecular Imaging Center Antwerp, University of Antwerp, Antwerp, Belgium
| | - Dorien Glorie
- Molecular Imaging Center Antwerp, University of Antwerp, Antwerp, Belgium
| | - Daniele Bertoglio
- Molecular Imaging Center Antwerp, University of Antwerp, Antwerp, Belgium
| | - Jochen Vleugels
- Product Development, University of Antwerp, Antwerp, Belgium; and
| | - Guido De Bruyne
- Product Development, University of Antwerp, Antwerp, Belgium; and
| | - Sigrid Stroobants
- Molecular Imaging Center Antwerp, University of Antwerp, Antwerp, Belgium.,University Hospital Antwerp, Antwerp, Belgium
| | - Steven Staelens
- Molecular Imaging Center Antwerp, University of Antwerp, Antwerp, Belgium
| | - Jeroen Verhaeghe
- Molecular Imaging Center Antwerp, University of Antwerp, Antwerp, Belgium
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Estimation of and correction for finite motion sampling errors in small animal PET rigid motion correction. Med Biol Eng Comput 2018; 57:505-518. [PMID: 30242596 PMCID: PMC6347657 DOI: 10.1007/s11517-018-1899-8] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/23/2018] [Accepted: 09/14/2018] [Indexed: 11/23/2022]
Abstract
Motion tracking with finite time sampling causing an associated unknown residual motion between two motion measurements is one of the factors contributing to resolution loss in small animal PET motion correction. The aim of this work is (i) to provide a means to estimate the effect of the finite motion sampling on the spatial resolution of the motion correction reconstructions and (ii) to correct for this residual motion thereby minimizing resolution loss. We calculate a tailored spatially variant deconvolution kernel from the measured motion data which is then used to deconvolve the motion corrected image using a 3D Richardson-Lucy algorithm. A simulation experiment of numerical phantoms as well as a microDerenzo phantom experiment wherein the phantom was manually moved at different speeds was performed to assess the performance of our proposed method. In the motion corrected images of the microDerenzo phantom there was an average rod FWHM differences between the slow and fast motion cases of 9.7%. This difference was reduced to 5.8% after applying the residual motion deconvolution. In awake animal experiments, the proposed method can serve to mitigate the finite sampling factor degrading the spatial resolution as well as the resolution differences between fast-moving and slow-moving animals. Motion correction of positron emission tomography (PET) scans of moving subjects can be performed by measuring the motion of the subject during the PET scan with an optical tracking camera. The motion tracking data obtained from the tracking camera is then used to correct the PET image reconstructions for motion. Due to finite time sampling of the motion data, the motion corrected reconstructions suffer from loss of spatial resolution. In the proposed method, a spatially variant deconvolution kernel is calculated from the motion tracking data, which is then used to correct the motion-corrected PET reconstructions for the blurring effect of the finite motion sampling through a Richardson-Lucy deconvolution. ![]()
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Wang J, Ji X, Zhang X, Sun Z, Wang T. Real-time robust individual X point localization for stereoscopic tracking. Pattern Recognit Lett 2018. [DOI: 10.1016/j.patrec.2018.07.002] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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Angelis GI, Gillam JE, Kyme AZ, Fulton RR, Meikle SR. Image-based modelling of residual blurring in motion corrected small animal PET imaging using motion dependent point spread functions. Biomed Phys Eng Express 2018. [DOI: 10.1088/2057-1976/aab922] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
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Kyme AZ, Judenhofer MS, Gong K, Bec J, Selfridge A, Du J, Qi J, Cherry SR, Meikle SR. Open-field mouse brain PET: design optimisation and detector characterisation. Phys Med Biol 2017; 62:6207-6225. [PMID: 28475491 DOI: 10.1088/1361-6560/aa7171] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
'Open-field' PET, in which an animal is free to move within an enclosed space during imaging, is a very promising advance for neuroscientific research. It provides a key advantage over conventional imaging under anesthesia by enabling functional changes in the brain to be correlated with an animal's behavioural response to environmental or pharmacologic stimuli. Previously we have demonstrated the feasibility of open-field imaging of rats using motion compensation techniques applied to a commercially available PET scanner. However, this approach of 'retro-fitting' motion compensation techniques to an existing system is limited by the inherent geometric and performance constraints of the system. The goal of this project is to develop a purpose-built PET scanner with geometry, motion tracking and imaging performance tailored and optimised for open-field imaging of the mouse brain. The design concept is a rail-based sliding tomograph which moves according to the animal's motion. Our specific aim in this work was to evaluate candidate scanner designs and characterise the performance of a depth-of-interaction detector module for the open-field system. We performed Monte Carlo simulations to estimate and compare the sensitivity and spatial resolution performance of four scanner geometries: a ring, parallel plate, and two box variants. Each system was based on a detector block consisting of a 23 × 23 array of 0.785 × 0.785 × 20 mm3 LSO crystals (overall dim. 19.6 × 19.6 × 20 mm). We found that a DoI resolution capability of 3 mm was necessary to achieve approximately uniform sub-millimetre spatial resolution throughout the FoV for all scanners except the parallel-plate geometry. With this DoI performance, the sensitivity advantage afforded by the box geometry with overlapping panels (16% peak absolute sensitivity, a 36% improvement over the ring design) suggests this unconventional design is best suited for imaging the mouse brain. We also built and characterised the block detector modelled in the simulations, including a dual-ended readout based on 6 × 6 arrays of through-silicon-via silicon photomultipliers (active area 84%) for DoI estimation. Identification of individual crystals in the flood map was excellent, energy resolution varied from 12.4% ± 0.6% near the centre to 24.4% ± 3.4% at the ends of the crystal, and the average DoI resolution was 2.8 mm ± 0.35 mm near the central depth (10 mm) and 3.5 mm ± 1.0 mm near the ends. Timing resolution was 1.4 ± 0.14 ns. Therefore, the DoI detector module meets the target specifications for the application and will be used as the basis for a prototype open-field mouse PET scanner.
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Affiliation(s)
- Andre Z Kyme
- Department of Biomedical Engineering, University of California, Davis CA 95616, United States of America. Faculty of Health Sciences and Brain & Mind Centre, University of Sydney, Sydney, Australia. Faculty of Engineering, School of AMME, University of Sydney, Sydney, Australia
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15
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Miranda A, Staelens S, Stroobants S, Verhaeghe J. Fast and Accurate Rat Head Motion Tracking With Point Sources for Awake Brain PET. IEEE TRANSACTIONS ON MEDICAL IMAGING 2017; 36:1573-1582. [PMID: 28207390 DOI: 10.1109/tmi.2017.2667889] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
To avoid the confounding effects of anesthesia and immobilization stress in rat brain positron emission tomography (PET), motion tracking-based unrestrained awake rat brain imaging is being developed. In this paper, we propose a fast and accurate rat headmotion tracking method based on small PET point sources. PET point sources (3-4) attached to the rat's head are tracked in image space using 15-32-ms time frames. Our point source tracking (PST) method was validated using a manually moved microDerenzo phantom that was simultaneously tracked with an optical tracker (OT) for comparison. The PST method was further validated in three awake [18F]FDG rat brain scans. Compared with the OT, the PST-based correction at the same frame rate (31.2 Hz) reduced the reconstructed FWHM by 0.39-0.66 mm for the different tested rod sizes of the microDerenzo phantom. The FWHM could be further reduced by another 0.07-0.13 mm when increasing the PST frame rate (66.7 Hz). Regional brain [18F]FDG uptake in the motion corrected scan was strongly correlated ( ) with that of the anesthetized reference scan for all three cases ( ). The proposed PST method allowed excellent and reproducible motion correction in awake in vivo experiments. In addition, there is no need of specialized tracking equipment or additional calibrations to be performed, the point sources are practically imperceptible to the rat, and PST is ideally suitable for small bore scanners, where optical tracking might be challenging.
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Angelis GI, Ryder WJ, Gillam JE, Boisson F, Kyme AZ, Fulton RR, Meikle SR, Kench PL. Rigid motion correction of dual opposed planar projections in single photon imaging. Phys Med Biol 2017; 62:3923-3943. [PMID: 28333040 DOI: 10.1088/1361-6560/aa68cd] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Awake and/or freely moving small animal single photon emission imaging allows the continuous study of molecules exhibiting slow kinetics without the need to restrain or anaesthetise the animals. Estimating motion free projections in freely moving small animal planar imaging can be considered as a limited angle tomography problem, except that we wish to estimate the 2D planar projections rather than the 3D volume, where the angular sampling in all three axes depends on the rotational motion of the animal. In this study, we hypothesise that the motion corrected planar projections estimated by reconstructing an estimate of the 3D volume using an iterative motion compensating reconstruction algorithm and integrating it along the projection path, will closely match the true, motion-less, planar distribution regardless of the object motion. We tested this hypothesis for the case of rigid motion using Monte-Carlo simulations and experimental phantom data based on a dual opposed detector system, where object motion was modelled with 6 degrees of freedom. In addition, we investigated the quantitative accuracy of the regional activity extracted from the geometric mean of opposing motion corrected planar projections. Results showed that it is feasible to estimate qualitatively accurate motion-corrected projections for a wide range of motions around all 3 axes. Errors in the geometric mean estimates of regional activity were relatively small and within 10% of expected true values. In addition, quantitative regional errors were dependent on the observed motion, as well as on the surrounding activity of overlapping organs. We conclude that both qualitatively and quantitatively accurate motion-free projections of the tracer distribution in a rigidly moving object can be estimated from dual opposed detectors using a correction approach within an iterative reconstruction framework and we expect this approach can be extended to the case of non-rigid motion.
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Affiliation(s)
- G I Angelis
- Imaging Physics Laboratory, Brain and Mind Centre, Camperdown, NSW 2050, Australia. Faculty of Health Sciences, The University of Sydney, NSW 2006, Sydney, Australia
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Carrara M, Giandini T, Bonfantini F, Avuzzi B, Villa S, Bedini N, Morlino S, Carabelli G, Frasca S, Valdagni R, Pignoli E. Analysis of electromagnetic transponders tracking data to quantify intrafraction prostate motion during radiotherapy treatments. ACTA ACUST UNITED AC 2017. [DOI: 10.1088/1742-6596/777/1/012036] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
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Miranda A, Staelens S, Stroobants S, Verhaeghe J. Markerless rat head motion tracking using structured light for brain PET imaging of unrestrained awake small animals. Phys Med Biol 2017; 62:1744-1758. [PMID: 28102175 DOI: 10.1088/1361-6560/aa5a46] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
Preclinical positron emission tomography (PET) imaging in small animals is generally performed under anesthesia to immobilize the animal during scanning. More recently, for rat brain PET studies, methods to perform scans of unrestrained awake rats are being developed in order to avoid the unwanted effects of anesthesia on the brain response. Here, we investigate the use of a projected structure stereo camera to track the motion of the rat head during the PET scan. The motion information is then used to correct the PET data. The stereo camera calculates a 3D point cloud representation of the scene and the tracking is performed by point cloud matching using the iterative closest point algorithm. The main advantage of the proposed motion tracking is that no intervention, e.g. for marker attachment, is needed. A manually moved microDerenzo phantom experiment and 3 awake rat [18F]FDG experiments were performed to evaluate the proposed tracking method. The tracking accuracy was 0.33 mm rms. After motion correction image reconstruction, the microDerenzo phantom was recovered albeit with some loss of resolution. The reconstructed FWHM of the 2.5 and 3 mm rods increased with 0.94 and 0.51 mm respectively in comparison with the motion-free case. In the rat experiments, the average tracking success rate was 64.7%. The correlation of relative brain regional [18F]FDG uptake between the anesthesia and awake scan reconstructions was increased from on average 0.291 (not significant) before correction to 0.909 (p < 0.0001) after motion correction. Markerless motion tracking using structured light can be successfully used for tracking of the rat head for motion correction in awake rat PET scans.
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Affiliation(s)
- Alan Miranda
- Molecular Imaging Center Antwerp, University of Antwerp, Universiteitsplein 1, 2610 Antwerp, Belgium
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Gillam JE, Angelis GI, Kyme AZ, Meikle SR. Motion compensation using origin ensembles in awake small animal positron emission tomography. Phys Med Biol 2017; 62:715-733. [PMID: 28072574 DOI: 10.1088/1361-6560/aa52aa] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
In emission tomographic imaging, the stochastic origin ensembles algorithm provides unique information regarding the detected counts given the measured data. Precision in both voxel and region-wise parameters may be determined for a single data set based on the posterior distribution of the count density allowing uncertainty estimates to be allocated to quantitative measures. Uncertainty estimates are of particular importance in awake animal neurological and behavioral studies for which head motion, unique for each acquired data set, perturbs the measured data. Motion compensation can be conducted when rigid head pose is measured during the scan. However, errors in pose measurements used for compensation can degrade the data and hence quantitative outcomes. In this investigation motion compensation and detector resolution models were incorporated into the basic origin ensembles algorithm and an efficient approach to computation was developed. The approach was validated against maximum liklihood-expectation maximisation and tested using simulated data. The resultant algorithm was then used to analyse quantitative uncertainty in regional activity estimates arising from changes in pose measurement precision. Finally, the posterior covariance acquired from a single data set was used to describe correlations between regions of interest providing information about pose measurement precision that may be useful in system analysis and design. The investigation demonstrates the use of origin ensembles as a powerful framework for evaluating statistical uncertainty of voxel and regional estimates. While in this investigation rigid motion was considered in the context of awake animal PET, the extension to arbitrary motion may provide clinical utility where respiratory or cardiac motion perturb the measured data.
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Affiliation(s)
- John E Gillam
- Faculty of Health Sciences and Brain & Mind Centre, University of Sydney, Sydney, Australia
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Spangler-Bickell MG, de Laat B, Fulton R, Bormans G, Nuyts J. The effect of isoflurane on 18F-FDG uptake in the rat brain: a fully conscious dynamic PET study using motion compensation. EJNMMI Res 2016; 6:86. [PMID: 27888500 PMCID: PMC5124015 DOI: 10.1186/s13550-016-0242-3] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/24/2016] [Accepted: 11/17/2016] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND In preclinical positron emission tomography (PET) studies an anaesthetic is used to ensure that the animal does not move during the scan. However, anaesthesia may have confounding effects on the drug or tracer kinetics under study, and the nature of these effects is usually not known. METHOD We have implemented a protocol for tracking the rigid motion of the head of a fully conscious rat during a PET scan and performing a motion compensated list-mode reconstruction of the data. Using this technique we have conducted eight rat studies to investigate the effect of isoflurane on the uptake of 18F-FDG in the brain, by comparing conscious and unconscious scans. RESULTS Our results indicate that isoflurane significantly decreases the whole brain uptake, as well as decreasing the relative regional FDG uptake in the cortex, diencephalon, and inferior colliculi, while increasing it in the vestibular nuclei. No statistically significant changes in FDG uptake were observed in the cerebellum and striata. CONCLUSION The applied event-based motion compensation technique allowed for the investigation of the effect of isoflurane on FDG uptake in the rat brain using fully awake and unrestrained rats, scanned dynamically from the moment of injection. A significant effect of the anaesthesia was observed in various regions of the brain.
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Affiliation(s)
- Matthew G Spangler-Bickell
- Department of Imaging and Pathology, KU Leuven - University of Leuven, Nuclear Medicine & Molecular Imaging, Medical Imaging Research Center (MIRC), Leuven, Belgium.
| | - Bart de Laat
- Department of Imaging and Pathology, KU Leuven - University of Leuven, Nuclear Medicine & Molecular Imaging, Medical Imaging Research Center (MIRC), Leuven, Belgium
| | - Roger Fulton
- Brain & Mind Centre and the Faculty of Health Sciences, University of Sydney, Sydney, Australia.,Department of Nuclear Medicine, Westmead Hospital, Sydney, Australia
| | - Guy Bormans
- Department of Radiopharmacy, KU Leuven, Leuven, Belgium
| | - Johan Nuyts
- Department of Imaging and Pathology, KU Leuven - University of Leuven, Nuclear Medicine & Molecular Imaging, Medical Imaging Research Center (MIRC), Leuven, Belgium
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Spangler-Bickell MG, Zhou L, Kyme AZ, De Laat B, Fulton RR, Nuyts J. Optimising rigid motion compensation for small animal brain PET imaging. Phys Med Biol 2016; 61:7074-7091. [PMID: 27648644 DOI: 10.1088/0031-9155/61/19/7074] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
Motion compensation (MC) in PET brain imaging of awake small animals is attracting increased attention in preclinical studies since it avoids the confounding effects of anaesthesia and enables behavioural tests during the scan. A popular MC technique is to use multiple external cameras to track the motion of the animal's head, which is assumed to be represented by the motion of a marker attached to its forehead. In this study we have explored several methods to improve the experimental setup and the reconstruction procedures of this method: optimising the camera-marker separation; improving the temporal synchronisation between the motion tracker measurements and the list-mode stream; post-acquisition smoothing and interpolation of the motion data; and list-mode reconstruction with appropriately selected subsets. These techniques have been tested and verified on measurements of a moving resolution phantom and brain scans of an awake rat. The proposed techniques improved the reconstructed spatial resolution of the phantom by 27% and of the rat brain by 14%. We suggest a set of optimal parameter values to use for awake animal PET studies and discuss the relative significance of each parameter choice.
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Affiliation(s)
- Matthew G Spangler-Bickell
- Department of Imaging and Pathology, KU Leuven-University of Leuven, Nuclear Medicine & Molecular Imaging, Medical Imaging Research Center (MIRC), Belgium
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Gillam JE, Angelis GI, Meikle SR. List-mode image reconstruction for positron emission tomography using tetrahedral voxels. Phys Med Biol 2016; 61:N497-N513. [PMID: 27552113 DOI: 10.1088/0031-9155/61/18/n497] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Image space decomposition based on tetrahedral voxels are interesting candidates for use in emission tomography. Tetrahedral voxels provide many of the advantages of point clouds with irregular spacing, such as being intrinsically multi-resolution, yet they also serve as a volumetric partition of the image space and so are comparable to more standard cubic voxels. Additionally, non-rigid displacement fields can be applied to the tetrahedral mesh in a straight-forward manner. So far studies incorporating tetrahedral decomposition of the image space have concentrated on pre-calculated, node-based, system matrix elements which reduces the flexibility of the tetrahedral approach and the capacity to accurately define regions of interest. Here, a list-mode on-the-fly calculation of the system matrix elements is described using a tetrahedral decomposition of the image space and volumetric elements-voxels. The algorithm is demonstrated in the context of awake animal PET which may require both rigid and non-rigid motion compensation, as well as quantification within small regions of the brain. This approach allows accurate, event based, motion compensation including non-rigid deformations.
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Affiliation(s)
- John E Gillam
- Faculty of Health Sciences, University of Sydney, New South Wales 2006, Australia. Brain and Mind Centre, Camperdown, New South Wales 2050, Australia
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Bickell M, Koesters T, Boada F, Nuyts J. PET motion correction using MR-derived motion parameters. EJNMMI Phys 2015; 1:A53. [PMID: 26501642 PMCID: PMC4546068 DOI: 10.1186/2197-7364-1-s1-a53] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022] Open
Affiliation(s)
- Matthew Bickell
- Department of Nuclear Medicine, Medical Imaging Research Center, KU Leuven, Belgium
| | - Thomas Koesters
- Center for Advanced Imaging Innovation and Research, New York University, Kragujevac, USA.,Department of Radiology, NYU School of Medicine, New York, Bernard & Irene Schwartz Center for Biomedical Imaging, New York, USA
| | - Fernando Boada
- Center for Advanced Imaging Innovation and Research, New York University, Kragujevac, USA.,Department of Radiology, NYU School of Medicine, New York, Bernard & Irene Schwartz Center for Biomedical Imaging, New York, USA
| | - Johan Nuyts
- Department of Nuclear Medicine, Medical Imaging Research Center, KU Leuven, Belgium
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Kim JH, Nuyts J, Kyme A, Kuncic Z, Fulton R. A rigid motion correction method for helical computed tomography (CT). Phys Med Biol 2015; 60:2047-73. [DOI: 10.1088/0031-9155/60/5/2047] [Citation(s) in RCA: 39] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
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Kyme A, Se S, Meikle S, Angelis G, Ryder W, Popovic K, Yatigammana D, Fulton R. Markerless motion tracking of awake animals in positron emission tomography. IEEE TRANSACTIONS ON MEDICAL IMAGING 2014; 33:2180-2190. [PMID: 24988591 DOI: 10.1109/tmi.2014.2332821] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/03/2023]
Abstract
Noninvasive functional imaging of awake, unrestrained small animals using motion-compensation removes the need for anesthetics and enables an animal's behavioral response to stimuli or administered drugs to be studied concurrently with imaging. While the feasibility of motion-compensated radiotracer imaging of awake rodents using marker-based optical motion tracking has been shown, markerless motion tracking would avoid the risk of marker detachment, streamline the experimental workflow, and potentially provide more accurate pose estimates over a greater range of motion. We have developed a stereoscopic tracking system which relies on native features on the head to estimate motion. Features are detected and matched across multiple camera views to accumulate a database of head landmarks and pose is estimated based on 3D-2D registration of the landmarks to features in each image. Pose estimates of a taxidermal rat head phantom undergoing realistic rat head motion via robot control had a root mean square error of 0.15 and 1.8 mm using markerless and marker-based motion tracking, respectively. Markerless motion tracking also led to an appreciable reduction in motion artifacts in motion-compensated positron emission tomography imaging of a live, unanesthetized rat. The results suggest that further improvements in live subjects are likely if nonrigid features are discriminated robustly and excluded from the pose estimation process.
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Angelis GI, Kyme AZ, Ryder WJ, Fulton RR, Meikle SR. Attenuation correction for freely moving small animal brain PET studies based on a virtual scanner geometry. Phys Med Biol 2014; 59:5651-66. [DOI: 10.1088/0031-9155/59/19/5651] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
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Angelis GI, Ryder WJ, Bashar R, Fulton RR, Meikle SR. Impact of extraneous mispositioned events on motion-corrected brain SPECT images of freely moving animals. Med Phys 2014; 41:092502. [PMID: 25186411 DOI: 10.1118/1.4892931] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022] Open
Abstract
PURPOSE Single photon emission computed tomography (SPECT) brain imaging of freely moving small animals would allow a wide range of important neurological processes and behaviors to be studied, which are normally inhibited by anesthetic drugs or precluded due to the animal being restrained. While rigid body motion of the head can be tracked and accounted for in the reconstruction, activity in the torso may confound brain measurements, especially since motion of the torso is more complex (i.e., nonrigid) and not well correlated with that of the head. The authors investigated the impact of mispositioned events and attenuation due to the torso on the accuracy of motion corrected brain images of freely moving mice. METHODS Monte Carlo simulations of a realistic voxelized mouse phantom and a dual compartment phantom were performed. Each phantom comprised a target and an extraneous compartment which were able to move independently of each other. Motion correction was performed based on the known motion of the target compartment only. Two SPECT camera geometries were investigated: a rotating single head detector and a stationary full ring detector. The effects of motion, detector geometry, and energy of the emitted photons (hence, attenuation) on bias and noise in reconstructed brain regions were evaluated. RESULTS The authors observed two main sources of bias: (a) motion-related inconsistencies in the projection data and (b) the mismatch between attenuation and emission. Both effects are caused by the assumption that the orientation of the torso is difficult to track and model, and therefore cannot be conveniently corrected for. The motion induced bias in some regions was up to 12% when no attenuation effects were considered, while it reached 40% when also combined with attenuation related inconsistencies. The detector geometry (i.e., rotating vs full ring) has a big impact on the accuracy of the reconstructed images, with the full ring detector being more advantageous. CONCLUSIONS Motion-induced inconsistencies in the projection data and attenuation/emission mismatch are the two main causes of bias in reconstructed brain images when there is complex motion. It appears that these two factors have a synergistic effect on the qualitative and quantitative accuracy of the reconstructed images.
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Affiliation(s)
- Georgios I Angelis
- Faculty of Health Sciences and Brain and Mind Research Institute, The University of Sydney, Sydney, NSW 2006, Australia
| | - William J Ryder
- Faculty of Health Sciences and Brain and Mind Research Institute, The University of Sydney, Sydney, NSW 2006, Australia
| | - Rezaul Bashar
- Faculty of Health Sciences and Brain and Mind Research Institute, The University of Sydney, Sydney, NSW 2006, Australia
| | - Roger R Fulton
- Faculty of Health Sciences and Brain and Mind Research Institute, The University of Sydney, Sydney, NSW 2006, Australia; School of Physics, University of Sydney, Sydney, NSW 2006, Australia; and Department of Medical Physics, Westmead Hospital, Sydney, NSW 2145, Australia
| | - Steven R Meikle
- Faculty of Health Sciences and Brain and Mind Research Institute, The University of Sydney, Sydney, NSW 2006, Australia
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O'Connor JM, Pretorius PH, Johnson K, King MA. A method to synchronize signals from multiple patient monitoring devices through a single input channel for inclusion in list-mode acquisitions. Med Phys 2013; 40:122502. [PMID: 24320538 PMCID: PMC3843760 DOI: 10.1118/1.4828844] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/07/2013] [Revised: 08/22/2013] [Accepted: 10/18/2013] [Indexed: 11/07/2022] Open
Abstract
PURPOSE This technical note documents a method that the authors developed for combining a signal to synchronize a patient-monitoring device with a second physiological signal for inclusion into list-mode acquisition. Our specific application requires synchronizing an external patient motion-tracking system with a medical imaging system by multiplexing the tracking input with the ECG input. The authors believe that their methodology can be adapted for use in a variety of medical imaging modalities including single photon emission computed tomography (SPECT) and positron emission tomography (PET). METHODS The authors insert a unique pulse sequence into a single physiological input channel. This sequence is then recorded in the list-mode acquisition along with the R-wave pulse used for ECG gating. The specific form of our pulse sequence allows for recognition of the time point being synchronized even when portions of the pulse sequence are lost due to collisions with R-wave pulses. This was achieved by altering our software used in binning the list-mode data to recognize even a portion of our pulse sequence. Limitations on heart rates at which our pulse sequence could be reliably detected were investigated by simulating the mixing of the two signals as a function of heart rate and time point during the cardiac cycle at which our pulse sequence is mixed with the cardiac signal. RESULTS The authors have successfully achieved accurate temporal synchronization of our motion-tracking system with acquisition of SPECT projections used in 17 recent clinical research cases. In our simulation analysis the authors determined that synchronization to enable compensation for body and respiratory motion could be achieved for heart rates up to 125 beats-per-minute (bpm). CONCLUSIONS Synchronization of list-mode acquisition with external patient monitoring devices such as those employed in motion-tracking can reliably be achieved using a simple method that can be implemented using minimal external hardware and software modification through a single input channel, while still recording cardiac gating signals.
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Affiliation(s)
- J Michael O'Connor
- Department of Radiology, University of Massachusetts Medical School, Worcester, Massachusetts 01655
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Welch A, Mingarelli M, Riedel G, Platt B. Mapping changes in mouse brain metabolism with PET/CT. J Nucl Med 2013; 54:1946-53. [PMID: 24009277 DOI: 10.2967/jnumed.113.121509] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022] Open
Abstract
UNLABELLED Because preclinical imaging offers challenges and opportunities, we set out to investigate and optimize image processing techniques to measure changes in mouse brain metabolism with preclinical (18)F-FDG PET/CT. In particular, we considered the effects of scan length, image registration methods, image quantification methods, and smoothing during statistical parametric mapping (SPM). METHODS A cohort of 12 wild-type mice was scanned on 3 occasions at an average age of 6, 10, and 14 mo. The impact of the scan length (10, 20, 30, or 40 min) was determined, and images were registered to a template based on either the PET or the CT image. Analysis was performed using SPM or predefined regions of interest (ROIs). Data were expressed in units of standardized uptake value or percentage injected dose per gram of tissue for absolute values; images were also normalized to whole-brain activity. RESULTS Significant variability was observed in global brain (18)F-FDG uptake between animals. Normalizing images to the whole-brain activity significantly improved detection of regional changes in metabolism. Registration based on CT images provided greater power for detecting changes in metabolism than did registration based on PET images only. In line with an age-dependent decline in brain metabolism, both ROI and SPM-based methods revealed significant changes; SPM, however, was generally more sensitive and region-specific. For example, small clusters of voxels within an ROI differed significantly between ages even in the absence of significant changes in average uptake over the whole region. Finally, and contrary to expectation, we found little benefit from longer scan times yet a marked reduction in uptake from 45 to 85 min after injection and regional variations in the rate of washout. CONCLUSION With appropriate processing, preclinical PET/CT provides a highly sensitive method for reliable identification of metabolic changes in the mouse brain.
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Affiliation(s)
- Andy Welch
- School of Medicine and Dentistry, University of Aberdeen, Aberdeen, United Kingdom; and
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Märk J, Benoit D, Balasse L, Benoit M, Clémens JC, Fieux S, Fougeron D, Graber-Bolis J, Janvier B, Jevaud M, Genoux A, Gisquet-Verrier P, Menouni M, Pain F, Pinot L, Tourvielle C, Zimmer L, Morel C, Laniece P. A wireless beta-microprobe based on pixelated silicon for in vivo brain studies in freely moving rats. Phys Med Biol 2013; 58:4483-500. [PMID: 23760022 DOI: 10.1088/0031-9155/58/13/4483] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
The investigation of neurophysiological mechanisms underlying the functional specificity of brain regions requires the development of technologies that are well adjusted to in vivo studies in small animals. An exciting challenge remains the combination of brain imaging and behavioural studies, which associates molecular processes of neuronal communications to their related actions. A pixelated intracerebral probe (PIXSIC) presents a novel strategy using a submillimetric probe for beta(+) radiotracer detection based on a pixelated silicon diode that can be stereotaxically implanted in the brain region of interest. This fully autonomous detection system permits time-resolved high sensitivity measurements of radiotracers with additional imaging features in freely moving rats. An application-specific integrated circuit (ASIC) allows for parallel signal processing of each pixel and enables the wireless operation. All components of the detector were tested and characterized. The beta(+) sensitivity of the system was determined with the probe dipped into radiotracer solutions. Monte Carlo simulations served to validate the experimental values and assess the contribution of gamma noise. Preliminary implantation tests on anaesthetized rats proved PIXSIC's functionality in brain tissue. High spatial resolution allows for the visualization of radiotracer concentration in different brain regions with high temporal resolution.
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Affiliation(s)
- J Märk
- CPPM, Aix-Marseille Université, CNRS/IN2P3, Marseille, France.
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Kyme A, Meikle S, Baldock C, Fulton R. Refraction-compensated motion tracking of unrestrained small animals in positron emission tomography. Med Image Anal 2012; 16:1317-28. [DOI: 10.1016/j.media.2012.04.005] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2011] [Revised: 04/19/2012] [Accepted: 04/24/2012] [Indexed: 10/28/2022]
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Kyme A, Meikle S, Baldock C, Fulton R. Tracking and characterizing the head motion of unanaesthetized rats in positron emission tomography. J R Soc Interface 2012; 9:3094-107. [PMID: 22718992 DOI: 10.1098/rsif.2012.0334] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Positron emission tomography (PET) is an important in vivo molecular imaging technique for translational research. Imaging unanaesthetized rats using motion-compensated PET avoids the confounding impact of anaesthetic drugs and enables animals to be imaged during normal or evoked behaviour. However, there is little published data on the nature of rat head motion to inform the design of suitable marker-based motion-tracking set-ups for brain imaging-specifically, set-ups that afford close to uninterrupted tracking. We performed a systematic study of rat head motion parameters for unanaesthetized tube-bound and freely moving rats with a view to designing suitable motion-tracking set-ups in each case. For tube-bound rats, using a single appropriately placed binocular tracker, uninterrupted tracking was possible greater than 95 per cent of the time. For freely moving rats, simulations and measurements of a live subject indicated that two opposed binocular trackers are sufficient (less than 10% interruption to tracking) for a wide variety of behaviour types. We conclude that reliable tracking of head pose can be achieved with marker-based optical-motion-tracking systems for both tube-bound and freely moving rats undergoing PET studies without sedation.
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Affiliation(s)
- Andre Kyme
- School of Physics, University of Sydney, Camperdown, New South Wales 2006, Australia.
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