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Sökning: WFRF:(Larsson Elna Marie) > Linköpings universitet

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1.
  • Blystad, Ida, 1972- (författare)
  • Clinical Applications of Synthetic MRI of the Brain
  • 2017
  • Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
    • Magnetic Resonance Imaging (MRI) has a high soft-tissue contrast with a high sensitivity for detecting pathological changes in the brain. Conventional MRI is a time-consuming method with multiple scans that relies on the visual assessment of the neuroradiologist. Synthetic MRI uses one scan to produce conventional images, but also quantitative maps based on relaxometry, that can be used to quantitatively analyse tissue properties and pathological changes. The studies presented here apply the use of synthetic MRI of the brain in different clinical settings.In the first study, synthetic MR images were compared to conventional MR images in 22 patients. The contrast, the contrast-to-noise ratio, and the diagnostic quality were assessed. Image quality was perceived to be inferior in the synthetic images, but synthetic images agreed with the clinical diagnoses to the same extent as the conventional images.Patients with early multiple sclerosis were analysed in the second study. In patients with multiple sclerosis, contrast-enhancing white matter lesions are a sign of active disease and can indicate a need for a change in therapy. Gadolinium-based contrast agents are used to detect active lesions, but concern has been raised regarding the long-term effects of repeated use of gadolinium. In this study, relaxometry was used to evaluate whether pre-contrast injection tissue-relaxation rates and proton density can identify active lesions without gadolinium. The findings suggest that active lesions often have relaxation times and proton density that differ from non-enhancing lesions, but with some overlap. This makes it difficult to replace gadolinium-based contrast agent injection with synthetic MRI in the monitoring of MS patients.Malignant gliomas are primary brain tumours with contrast enhancement due to a defective blood-brain barrier. However, they also grow in an infiltrative, diffuse manner, making it difficult to clearly delineate them from surrounding normal brain tissue in the diagnostic workup, at surgery, and during follow-up. The contrast-enhancing part of the tumour is easily visualised, but not the diffuse infiltration. In studies three and four, synthetic MRI was used to analyse the peritumoral area of malignant gliomas, and revealed quantitative findings regarding peritumoral relaxation changes and non-visible contrast enhancement suggestive of non-visible infiltrative tumour growth.In conclusion, synthetic MRI provides quantitative information about the brain tissue and this could improve the diagnosis and treatment for patients.
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2.
  • Blystad, Ida, et al. (författare)
  • Synthetic MRI of the brain in a clinical setting
  • 2012
  • Ingår i: Acta Radiologica. - : Sage Publications. - 0284-1851 .- 1600-0455. ; 53:10, s. 1158-1163
  • Tidskriftsartikel (refereegranskat)abstract
    • BACKGROUND:Conventional magnetic resonance imaging (MRI) has relatively long scan times for routine examinations, and the signal intensity of the images is related to the specific MR scanner settings. Due to scanner imperfections and automatic optimizations, it is impossible to compare images in terms of absolute image intensity. Synthetic MRI, a method to generate conventional images based on MR quantification, potentially both decreases examination time and enables quantitative measurements.PURPOSE:To evaluate synthetic MRI of the brain in a clinical setting by assessment of the contrast, the contrast-to-noise ratio (CNR), and the diagnostic quality compared with conventional MR images.MATERIAL AND METHODS:Twenty-two patients had synthetic imaging added to their clinical MR examination. In each patient, 12 regions of interest were placed in the brain images to measure contrast and CNR. Furthermore, general image quality, probable diagnosis, and lesion conspicuity were investigated.RESULTS:Synthetic T1-weighted turbo spin echo and T2-weighted turbo spin echo images had higher contrast but also a higher level of noise, resulting in a similar CNR compared with conventional images. Synthetic T2-weighted FLAIR images had lower contrast and a higher level of noise, which led to a lower CNR. Synthetic images were generally assessed to be of inferior image quality, but agreed with the clinical diagnosis to the same extent as the conventional images. Lesion conspicuity was higher in the synthetic T1-weighted images, which also had a better agreement with the clinical diagnoses than the conventional T1-weighted images.CONCLUSION:Synthetic MR can potentially shorten the MR examination time. Even though the image quality is perceived to be inferior, synthetic images agreed with the clinical diagnosis to the same extent as the conventional images in this study.
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3.
  • Nordanskog, Pia, et al. (författare)
  • Hippocampal volume in relation to clinical and cognitive outcome after electroconvulsive therapy in depression
  • 2014
  • Ingår i: Acta Psychiatrica Scandinavica. - United States : Wiley-Blackwell. - 0001-690X .- 1600-0447. ; 129:4, s. 303-311
  • Tidskriftsartikel (refereegranskat)abstract
    • OBJECTIVE:In a previous magnetic resonance imaging (MRI) study, we found a significant increase in hippocampal volume immediately after electroconvulsive therapy (ECT) in patients with depression. The aim of this study was to evaluate hippocampal volume up to 1 year after ECT and investigate its possible relation to clinical and cognitive outcome.METHOD:Clinical and cognitive outcome in 12 in-patients with depression receiving antidepressive pharmacological treatment referred for ECT were investigated with the Montgomery-Asberg Depression Rating Scale (MADRS) and a broad neuropsychological test battery within 1 week before and after ECT. The assessments were repeated 6 and 12 months after baseline in 10 and seven of these patients, respectively. Hippocampal volumes were measured on all four occasions with 3 Tesla MRI.RESULTS:Hippocampal volume returned to baseline during the follow-up period of 6 months. Neither the significant antidepressant effect nor the significant transient decrease in executive and verbal episodic memory tests after ECT could be related to changes in hippocampal volume. No persistent cognitive side effects were observed 1 year after ECT.CONCLUSION:The immediate increase in hippocampal volume after ECT is reversible and is not related to clinical or cognitive outcome.
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4.
  • Nordanskog, Pia, et al. (författare)
  • Increase in Hippocampal Volume After Electroconvulsive Therapy in Patients With Depression : A Volumetric Magnetic Resonance Imaging Study
  • 2010
  • Ingår i: JOURNAL OF ECT. - 1095-0680 .- 1533-4112. ; 26:1, s. 62-67
  • Tidskriftsartikel (refereegranskat)abstract
    • Background: Major depression has traditionally been regarded as a neurochemical disease, but findings of a decreased hippocampal volume in patients with depression have turned the pathophysiological focus toward impairments in structural plasticity. The mechanisms of action of the most effective antidepressive treatment, electroconvulsive therapy (ECT), still remains elusive, but recent animal research has provided evidence for a cell proliferative effect in the hippocampus. The aim of this prospective study was to determine if hippocampal volume changes after ECT in patients with depression.Methods: Twelve patients with depression and ongoing antidepressive pharmacological treatment were investigated with clinical ratings and 3 T magnetic resonance imaging within 1 week before and after the ECT series. Each hippocampus was manually outlined on coronal slices, and the volume was calculated.Results: The left as well as the right hippocampal volume increased significantly after ECT.Conclusions: The hippocampal volume increases after ECT, supporting the hypothesis that hippocampus may play a central role in the treatment of depression.
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5.
  • Zetterling, Maria, et al. (författare)
  • Extension of diffuse low-grade gliomas beyond radiological borders as shown by the coregistration of histopathological and magnetic resonance imaging data
  • 2016
  • Ingår i: Journal of Neurosurgery. - : AMER ASSOC NEUROLOGICAL SURGEONS. - 0022-3085 .- 1933-0693. ; 125:5, s. 1155-1166
  • Tidskriftsartikel (refereegranskat)abstract
    • Background: Magnetic resonance imaging tends to underestimate the extent of diffuse low-grade gliomas (DLGGs). With the aim of studying the presence of tumor cells outside the radiological border, the authors developed a method of correlating MRI findings with histological data in patients with suspected DLGGs in whom en bloc resections were performed.Methods: Five patients with suspected DLGG suitable for en bloc resection were recruited from an ongoing prospective study. Sections of the entire tumor were immunostained with antibodies against mutated IDH1 protein (IDH1-R132H). Magnetic resonance images were coregistered with corresponding IDH1 images. The growth pattern of tumor cells in white and gray matter was assessed in comparison with signal changes on corresponding MRI slices.Results: Neuropathological assessment revealed DLGG in 4 patients and progression to WHO Grade III glioma in 1 patient. The tumor core consisted of a high density of IDH1-R132H–positive tumor cells and was located in both gray and white matter. Tumor cells infiltrated along the peripheral fibers of the white matter tracts. In all cases, tumor cells were found outside the radiological tumor border delineated on T2-FLAIR MRI sequences.Conclusions: The authors present a new method for the coregistration of histological and radiological characteristics of en bloc–removed infiltrative brain tumors that discloses tumor invasion at the radiological tumor borders. This technique can be applied to evaluate the sensitivity of alternative imaging methods to detect scattered tumor cells at tumor borders. Accurate methods for detection of infiltrative tumor cells will improve the possibility of performing radical tumor resection. In future studies, the method could also be used for in vivo studies of tumor invasion.
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6.
  • Blystad, Ida, 1972-, et al. (författare)
  • Quantitative MRI using relaxometry in malignant gliomas detects contrast enhancement in peritumoral oedema
  • 2020
  • Ingår i: Scientific Reports. - : Springer Nature. - 2045-2322. ; 10:1
  • Tidskriftsartikel (refereegranskat)abstract
    • Malignant gliomas are primary brain tumours with an infiltrative growth pattern, often with contrast enhancement on magnetic resonance imaging (MRI). However, it is well known that tumour infiltration extends beyond the visible contrast enhancement. The aim of this study was to investigate if there is contrast enhancement not detected visually in the peritumoral oedema of malignant gliomas by using relaxometry with synthetic MRI. 25 patients who had brain tumours with a radiological appearance of malignant glioma were prospectively included. A quantitative MR-sequence measuring longitudinal relaxation (R-1), transverse relaxation (R-2) and proton density (PD), was added to the standard MRI protocol before surgery. Five patients were excluded, and in 20 patients, synthetic MR images were created from the quantitative scans. Manual regions of interest (ROIs) outlined the visibly contrast-enhancing border of the tumours and the peritumoral area. Contrast enhancement was quantified by subtraction of native images from post GD-images, creating an R-1-difference-map. The quantitative R-1-difference-maps showed significant contrast enhancement in the peritumoral area (0.047) compared to normal appearing white matter (0.032), p = 0.048. Relaxometry detects contrast enhancement in the peritumoral area of malignant gliomas. This could represent infiltrative tumour growth.
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7.
  • Georgiopoulos, Charalampos, et al. (författare)
  • A study of neural activity and functional connectivity within the olfactory brain network in Parkinson's disease
  • 2019
  • Ingår i: NeuroImage. - : Elsevier. - 2213-1582. ; 23
  • Tidskriftsartikel (refereegranskat)abstract
    • Olfactory dysfunction is an early manifestation of Parkinson's disease (PD). The present study aimed to illustrate potential differences between PD patients and healthy controls in terms of neural activity and functional connectivity within the olfactory brain network. Twenty PD patients and twenty healthy controls were examined with olfactory fMRI and resting-state fMRI. Data analysis of olfactory fMRI included data-driven tensorial independent component (ICA) and task-driven general linear model (GLM) analyses. Data analysis of resting-state fMRI included probabilistic ICA based on temporal concatenation and functional connectivity analysis within the olfactory network. ICA of olfactory fMRI identified an olfactory network consisting of the posterior piriform cortex, insula, right orbitofrontal cortex and thalamus. Recruitment of this network was less significant for PD patients. GLM analysis revealed significantly lower activity in the insula bilaterally and the right orbitofrontal cortex in PD compared to healthy controls but no significant differences in the olfactory cortex itself. Analysis of resting-state fMRI did not reveal any differences in the functional connectivity within the olfactory, default mode, salience or central executive networks between the two groups. In conclusion, olfactory dysfunction in PD is associated with less significant recruitment of the olfactory brain network. ICA could demonstrate differences in both the olfactory cortex and its main projections, compared to GLM that revealed differences only on the latter. Resting-state fMRI did not reveal any significant differences in functional connectivity within the olfactory, default mode, salience and central executive networks in this cohort.
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8.
  • Georgiopoulos, Charalampos, 1984- (författare)
  • Imaging Studies of Olfaction in Health and Parkinsonism
  • 2019
  • Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
    • Olfactory loss is a common non-motor symptom of Parkinson’s disease (PD), often preceding the cardinal motor symptoms of the disease. The aim of this thesis was to: (a) evaluate whether olfactory examination can increase diagnostic accuracy, and (b) study the structural and functional neural basis of olfactory dysfunction in PD with different applications of Magnetic Resonance Imaging (MRI).Paper I was a comparison of the diagnostic accuracy between a simple smell identification test and DaTSCAN Single Photon Emission Computerized Tomography (SPECT), a nuclear medicine tomographic imaging technique that is commonly used in patients with suspected parkinsonism. The results indicate that smell test is inferior to DaTSCAN SPECT, but the combination of these two methods can lead to improved diagnostic accuracy.Paper II showed that diffusion MRI could detect discrete microstructural changes in the white matter of brain areas that participate in higher order olfactory neurotransmission, whereas MRI with Magnetization Transfer contrast could not.Paper III was a methodological study on how two different acquisition parameters can affect the activation pattern of olfactory brain areas, as observed with functional MRI (fMRI). The results indicate that brief olfactory stimulation and fast sampling rate should be preferred on olfactory fMRI studies.Paper IV used olfactory fMRI and resting-state fMRI in order to elucidate potentially altered activation patterns and functional connectivity within olfactory brain areas, between PD patients and healthy controls. Olfactory fMRI showed that olfactory impairment in PD is associated with significantly lower recruitment of the olfactory network. Resting-state fMRI did not detect any significant changes in the functional connectivity within the olfactory network of PD patients.In conclusion, the included studies provide evidence of: (a) disease-related structural and functional changes in olfactory brain areas, and (b) beneficial addition of olfactory tests in the clinical work-up of patients with parkinsonism.
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9.
  • Georgiopoulos, Charalampos, et al. (författare)
  • Olfactory fMRI: Implications of Stimulation Length and Repetition Time
  • 2018
  • Ingår i: Chemical Senses. - : OXFORD UNIV PRESS. - 0379-864X .- 1464-3553. ; 43:6, s. 389-398
  • Tidskriftsartikel (refereegranskat)abstract
    • Studying olfaction with functional magnetic resonance imaging (fMRI) poses various methodological challenges. This study aimed to investigate the effects of stimulation length and repetition time (TR) on the activation pattern of 4 olfactory brain regions: the anterior and the posterior piriform cortex, the orbitofrontal cortex, and the insula. Twenty-two healthy participants with normal olfaction were examined with fMRI, with 2 stimulation lengths (6 s and 15 s) and 2 TRs (0.901 s and 1.34 s). Data were analyzed using General Linear Model (GLM), Tensorial Independent Component Analysis (TICA), and by plotting the event-related time course of brain activation in the 4 olfactory regions of interest. The statistical analysis of the time courses revealed that short TR was associated with more pronounced signal increase and short stimulation was associated with shorter time to peak signal. Additionally, both long stimulation and short TR were associated with oscillatory time courses, whereas both short stimulation and short TR resulted in more typical time courses. GLM analysis showed that the combination of short stimulation and short TR could result in visually larger activation within these olfactory areas. TICA validated that the tested paradigm was spatially and temporally associated with a functionally connected network that included all 4 olfactory regions. In conclusion, the combination of short stimulation and short TR is associated with higher signal increase and shorter time to peak, making it more amenable to standard GLM-type analyses than long stimulation and long TR, and it should, thus, be preferable for olfactory fMRI.
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10.
  • Georgiopoulos, Charalampos, et al. (författare)
  • Olfactory Impairment in Parkinson's Disease Studied with Diffusion Tensor and Magnetization Transfer Imaging.
  • 2017
  • Ingår i: Journal of Parkinson's Disease. - : IOS PRESS. - 1877-7171 .- 1877-718X. ; 7:2, s. 301-311
  • Tidskriftsartikel (refereegranskat)abstract
    • BACKGROUND: Olfactory impairment is an early manifestation of Parkinson's disease (PD). Diffusion Tensor Imaging (DTI) and Magnetization Transfer (MT) are two imaging techniques that allow noninvasive detection of microstructural changes in the cerebral white matter.OBJECTIVE: To assess white matter alterations associated with olfactory impairment in PD, using a binary imaging approach with DTI and MT.METHODS: 22 PD patients and 13 healthy controls were examined with DTI, MT and an odor discrimination test. DTI data were first analyzed with tract-based spatial statistics (TBSS) in order to detect differences in fractional anisotropy, mean, radial and axial diffusivity between PD patients and controls. Voxelwise randomized permutation was employed for the MT analysis, after spatial and intensity normalization. Additionally, ROI analysis was performed on both the DTI and MT data, focused on the white matter adjacent to olfactory brain regions.RESULTS: Whole brain voxelwise analysis revealed decreased axial diffusivity in the left uncinate fasciculus and the white matter adjacent to the left olfactory sulcus of PD patients. ROI analysis demonstrated decreased axial diffusivity in the right orbitofrontal cortex, as well as decreased mean diffusivity and axial diffusivity in the white matter of the left entorhinal cortex of PD patients. There were no significant differences regarding fractional anisotropy, radial diffusivity or MT between patients and controls.CONCLUSIONS: ROI analysis of DTI could detect microstructural changes in the white matter adjacent to olfactory areas in PD patients, whereas MT imaging could not.
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