| 1. |
- Andersson, Karin, 1972, et al.
(författare)
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Inflammation in the hippocampus affects IGF1 receptor signaling and contributes to neurological sequelae in rheumatoid arthritis.
- 2018
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Ingår i: Proceedings of the National Academy of Sciences of the United States of America. - : Proceedings of the National Academy of Sciences. - 1091-6490. ; 115:51
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Tidskriftsartikel (refereegranskat)abstract
- Rheumatoid arthritis (RA) is an inflammatory joint disease with a neurological component including depression, cognitive deficits, and pain, which substantially affect patients' quality of daily life. Insulin-like growth factor 1 receptor (IGF1R) signaling is one of the factors in RA pathogenesis as well as a known regulator of adult neurogenesis. The purpose of this study was to investigate the association between IGF1R signaling and the neurological symptoms in RA. In experimental RA, we demonstrated that arthritis induced enrichment of IBA1+ microglia in the hippocampus. This coincided with inhibitory phosphorylation of insulin receptor substrate 1 (IRS1) and up-regulation of IGF1R in the pyramidal cell layer of the cornus ammoni and in the dentate gyrus, reproducing the molecular features of the IGF1/insulin resistance. The aberrant IGF1R signaling was associated with reduced hippocampal neurogenesis, smaller hippocampus, and increased immobility of RA mice. Inhibition of IGF1R in experimental RA led to a reduction of IRS1 inhibition and partial improvement of neurogenesis. Evaluation of physical functioning and brain imaging in RA patients revealed that enhanced functional disability is linked with smaller hippocampus volume and aberrant IGF1R/IRS1 signaling. These results point to abnormal IGF1R signaling in the brain as a mediator of neurological sequelae in RA and provide support for the potentially reversible nature of hippocampal changes.
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| 2. |
- Brun, Eva, et al.
(författare)
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Early prediction of treatment outcome in head and neck cancer with 2-18FDG PET
- 1997
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Ingår i: Acta Oncologica. - : Informa UK Limited. - 1651-226X .- 0284-186X. ; 36:7, s. 741-747
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Tidskriftsartikel (refereegranskat)abstract
- The development of alternative treatment regimens in clinical oncology has increased the need for early prediction of cancer therapy outcome. The aim of this study was, early in the treatment phase, to identify patients with advanced head and neck cancer, responding or not responding to initiated therapy. The tumour metabolic rate of glucose (MRgl) examined by 2-18FDG-PET was determined in 17 patients before and after the first weeks of either radiotherapy (16-35 Gy) or one course of combination chemotherapy. Metabolic values uptake values normalized to plasma activity integrals--were correlated to loco-regional outcome, as evaluated 5-6 weeks after completion of treatment. Initial low tumour MRgl (<20 micromol/min/100 g tissue), in primary lesions or regional metastases, predicted a local complete response. When a high initial tumour MRgl was found, the magnitude of the reduction of MRgl in the second PET examination might be an adjunct in predicting local tumour response.
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| 3. |
- DrAdda, Ilenia, et al.
(författare)
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A Statistical DOI Estimation Algorithm for a SiPM-Based Clinical SPECT Insert
- 2022
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Ingår i: IEEE Transactions on Radiation and Plasma Medical Sciences. - 2469-7311. ; 6:7, s. 771-777
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Tidskriftsartikel (refereegranskat)abstract
- A prototype clinical brain SPECT insert has been designed for use in simultaneous SPECT/MRI. The system utilises novel slit-slat collimators which, like pinhole collimators, suffers from parallax errors due to the large incident angle of photons. A statistical algorithm has been developed to determine the depth-of-interaction (DOI) with a view to improving image performance. The importance of DOI correction was demonstrated using Monte Carlo simulation. This simulation also indicated that 4 DOI layers (3×1.5 mm+3.5 mm) may be sufficient. The improvement in event localisation was demonstrated on a single detector before implementing the algorithm on the full clinical prototype where some limitations in event localisation in layers close to the readout plane were observed. Nevertheless DOI enabled the rejection of poorly localised events with improved resolution in reconstructed line sources.
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| 4. |
- Hutton, B F, et al.
(författare)
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Reducing the influence of spatial resolution to improve quantitative accuracy in emission tomography : A comparison of potential strategies
- 2006
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Ingår i: Nuclear Instruments and Methods in Physics Research Section A. - : Elsevier BV. - 0168-9002 .- 1872-9576. ; 569:2 SPEC. ISS., s. 462-466
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Tidskriftsartikel (refereegranskat)abstract
- The goal of this paper is to compare strategies for reducing partial volume effects by either minimizing the cause (i.e. improving resolution) or correcting the effect. Correction for resolution loss can be achieved either by modelling the resolution for use in iterative reconstruction or by imposing constraints based on knowledge of the underlying anatomy. Approaches to partial volume correction largely rely on knowledge of the underlying anatomy, based on well-registered high-resolution anatomical imaging modalities (CT or MRI). Corrections can be applied by considering the signal loss that results by smoothing the high-resolution modality to the same resolution as obtained in emission tomography. A physical phantom representing the central brain structures was used to evaluate the quantitative accuracy of the various strategies for either improving resolution or correcting for partial volume effects. Inclusion of resolution in the reconstruction model improved the measured contrast for the central brain structures but still underestimated the true object contrast (∼0.70). Use of information on the boundaries of the structures in conjunction with a smoothing prior using maximum entropy reconstruction achieved some degree of contrast enhancement and improved the noise properties of the resulting images. Partial volume correction based on segmentation of registered anatomical images and knowledge of the reconstructed resolution permitted more accurate quantification of the target to background ratio for individual brain structures. © 2006 Elsevier B.V. All rights reserved.
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| 5. |
- Jawak, Shridhar D., et al.
(författare)
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SIOS's Earth Observation (EO), Remote Sensing (RS), and Operational Activities in Response to COVID-19
- 2021
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Ingår i: Remote Sensing. - : MDPI. - 2072-4292. ; 13:4
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Tidskriftsartikel (refereegranskat)abstract
- Svalbard Integrated Arctic Earth Observing System (SIOS) is an international partnership of research institutions studying the environment and climate in and around Svalbard. SIOS is developing an efficient observing system, where researchers share technology, experience, and data, work together to close knowledge gaps, and decrease the environmental footprint of science. SIOS maintains and facilitates various scientific activities such as the State of the Environmental Science in Svalbard (SESS) report, international access to research infrastructure in Svalbard, Earth observation and remote sensing services, training courses for the Arctic science community, and open access to data. This perspective paper highlights the activities of SIOS Knowledge Centre, the central hub of SIOS, and the SIOS Remote Sensing Working Group (RSWG) in response to the unprecedented situation imposed by the global pandemic coronavirus (SARS-CoV-2) disease 2019 (COVID-19). The pandemic has affected Svalbard research in several ways. When Norway declared a nationwide lockdown to decrease the rate of spread of the COVID-19 in the community, even more strict measures were taken to protect the Svalbard community from the potential spread of the disease. Due to the lockdown, travel restrictions, and quarantine regulations declared by many nations, most physical meetings, training courses, conferences, and workshops worldwide were cancelled by the first week of March 2020. The resumption of physical scientific meetings is still uncertain in the foreseeable future. Additionally, field campaigns to polar regions, including Svalbard, were and remain severely affected. In response to this changing situation, SIOS initiated several operational activities suitable to mitigate the new challenges resulting from the pandemic. This article provides an extensive overview of SIOS's Earth observation (EO), remote sensing (RS) and other operational activities strengthened and developed in response to COVID-19 to support the Svalbard scientific community in times of cancelled/postponed field campaigns in Svalbard. These include (1) an initiative to patch up field data (in situ) with RS observations, (2) a logistics sharing notice board for effective coordinating field activities in the pandemic times, (3) a monthly webinar series and panel discussion on EO talks, (4) an online conference on EO and RS, (5) the SIOS's special issue in the Remote Sensing (MDPI) journal, (6) the conversion of a terrestrial remote sensing training course into an online edition, and (7) the announcement of opportunity (AO) in airborne remote sensing for filling the data gaps using aerial imagery and hyperspectral data. As SIOS is a consortium of 24 research institutions from 9 nations, this paper also presents an extensive overview of the activities from a few research institutes in pandemic times and highlights our upcoming activities for the next year 2021. Finally, we provide a critical perspective on our overall response, possible broader impacts, relevance to other observing systems, and future directions. We hope that our practical services, experiences, and activities implemented in these difficult times will motivate other similar monitoring programs and observing systems when responding to future challenging situations. With a broad scientific audience in mind, we present our perspective paper on activities in Svalbard as a case study.
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| 6. |
- Ljungberg, Michael, et al.
(författare)
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Single Photon Emission Computed Tomography (SPECT) and SPECT/CT Hybrid Imaging
- 2022. - 1
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Ingår i: Handbook of Nuclear Medicine and Molecular Imaging for Physicists : Instrumentation and Imaging Procedures - Instrumentation and Imaging Procedures. - 9781138593268 - 9780429489556 ; 1
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Bokkapitel (refereegranskat)abstract
- Images created using a standard collimator-based scintillation camera are essentially 2D images, lacking information regarding the source depth, since the value in a particular pixel in the image represents detection of photons along a line determined by the collimator. However, it is possible to reconstruct a set of 2D images that together form a 3D image of the underlying activity distribution from data acquired of the same source distribution at different projection angles around the object. This chapter will describe the way in which these data can be used to reconstruct transversal images by the filtered back-projection (FBP) method as well as by iterative algorithms, and also how noise regularization can be implemented. Various physical factors that affect the reconstructed images will also be discussed. If we combine a SPECT system with a CT system and display the images from both as a single hybrid image, additional useful information can be obtained. The CT information can also be used to correct for non-homogeneous attenuation, scatter, and partial-volume effects. Finally, the chapter will discuss how the combination of quantitative SPECT images registered to CT images can be used for dosimetry calculations.
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| 7. |
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| 8. |
- Morahan, Ashley J., et al.
(författare)
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Impact of DOI in a Clinical SPECT/MRI System : A Simulation Study
- 2020
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Ingår i: 2020 IEEE Nuclear Science Symposium and Medical Imaging Conference, NSS/MIC 2020. - 9781728176932
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Konferensbidrag (refereegranskat)abstract
- A novel SPECT/MRI scanner has been modelled and tested here using Monte Carlo simulation software, SIMIND. The INSERT SPECT/MRI system faces challenges with event reconstruction due to photon depth of interaction. The novel SPECT system is subject to parallax errors due to its crystal size and slit aperture collimator. We present a simple measure of the DOI errors through SIMIND experiments; by modelling the DOI layers we are able to improve the reconstruction of projection data in the INSERT scanner. A set of capillary phantoms are simulated to explore the impact of DOI on the resolution of the scanner and establish corrections in the system's reconstruction.
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| 9. |
- Sjögreen Gleisner, Katarina, et al.
(författare)
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Parametric images of antibody pharmacokinetics based on serial quantitative whole-body imaging and blood sampling
- 2007
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Ingår i: Journal of Nuclear Medicine. - : Society of Nuclear Medicine. - 0161-5505. ; 48:8, s. 1369-1378
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Tidskriftsartikel (refereegranskat)abstract
- We present a method for pharmacokinetic modeling of distributions of In-111-labeled monoclonal antibodies (mAbs) on individual pixels of planar scintillation-camera images. Methods: The method is applied to 2 sets of clinical whole-body images, each consisting of 6 consecutive images acquired over a week. Quantification is performed on a pixel basis, yielding images in units of Bq/pixel. The images acquired on the different occasions are registered using a nonrigid method, and for each pixel location a time-activity curve is obtained for which kinetic modeling is performed. The In-111-mAb is assumed to be located in either the vascular or the extravascular space. The vascular content is assumed to follow the global blood kinetics as determined from blood samples, together with a model parameter alpha that describes the fraction of the whole-body blood volume present in the particular pixel. The rate of change of the extravascular compartment is described by a linear 1-tissue-compartment model with 2 rate constants, K-1' and k(2), reflecting extravasation and washout, respectively. The model is optimized for each pixel position with regard to the values of the 3 parameters (alpha, K-1', and k(2)), resulting in 3 parametric images. From these, images of the cumulated activity in vascular and extravascular spaces are calculated, as is an image of the rate-constants ratio, which is closely related to the volume of distribution. Results: The resulting parametric images are analyzed in terms of the appearance of the time-activity curves at various locations. Results also include interpretation of the parametric images in their clinical context, and the location of regions that exhibit high extravasation and a low washout rate is compared with confirmed malignant sites. Conclusion: Parametric imaging allows the study and analysis of the spatial and temporal distributions of mAbs simultaneously. Parametric imaging enhances regions where the pharmacokinetics differ from the surrounding tissue and provides a tool to detect and locate unexpected kinetic behavior, which is sometimes characteristic of malignant tissue. For dosimetry in radionuclide therapy, parametric imaging offers a less biased means of analyzing serial mAb images than traditional region-of-interest-based analysis.
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| 10. |
- Sjögreen Gleisner, Katarina, et al.
(författare)
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Registration of abdominal CT and SPECT images using Compton scatter data
- 1997
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Ingår i: Information Processing in Medical Imaging. - Berlin, Heidelberg : Springer Berlin Heidelberg. - 1611-3349 .- 0302-9743. - 9783540630463 ; 1230, s. 232-244
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Bokkapitel (refereegranskat)abstract
- The present study investigates the possibility to utilize Compton scatter data for registration of abdominal SPECT images. A method for registration to CT is presented, based on principal component analysis and cross-correlation of binary images representing the interior of the patient. Segmentation of scatter images is performed with two methods, thresholding and a deformable contour method. To achieve similarity of organ positions between scans, a positioning device is applied to the patient. Evaluation of the registration accuracy is performed with a) a 131I phantom study, b) a Monte Carlo simulation study of an anthropomorphic phantom, and c) a 123I patient trial. For a) r.m.s. distances between positions that should be equal in CT and SPECT are obtained to 1.0±0.7 mm, which thus for a rigid object is at sub pixel level. From b) results show that r.m.s. distances depend on the slice activity distribution. With a symmetrical distribution deviations are in the order of 5 mm. In c) distances between markers on the patient boundary are at the maximum 16 mm and on an average 10 mm. It is concluded that by utilizing the available Compton scatter data, valuable positioning information is achieved, that can be used for registration of SPECT images.
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