| 1. |
- Knutsson, Linda, et al.
(författare)
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Dynamic susceptibility contrast MRI with a prebolus contrast agent administration design for improved absolute quantification of perfusion.
- 2014
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Ingår i: Magnetic Resonance in Medicine. - : Wiley. - 1522-2594 .- 0740-3194. ; 72:4, s. 996-1006
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Tidskriftsartikel (refereegranskat)abstract
- Arterial partial-volume effects (PVEs) often hamper reproducible absolute quantification of cerebral blood flow (CBF) and cerebral blood volume (CBV) obtained by dynamic susceptibility contrast MRI (DSC-MRI). The aim of this study was to examine whether arterial PVEs in DSC-MRI data can be minimized by rescaling the arterial input function (AIF) using a sagittal-sinus venous output function obtained following a prebolus administration of a low dose of contrast agent.
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| 2. |
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| 3. |
- Delavaran, Hossein, et al.
(författare)
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Proximity of brain infarcts to regions of endogenous neurogenesis and involvement of striatum in ischaemic stroke.
- 2012
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Ingår i: European Journal of Neurology. - : Wiley. - 1351-5101 .- 1468-1331.
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Tidskriftsartikel (refereegranskat)abstract
- BACKGROUND: Clinical stroke trials with stem cell-based approaches aiming for trophic actions, modulation of inflammation and neuroprotection are ongoing. However, experimental studies also suggest that neuronal replacement by grafted neural stem cells (NSCs) and possibly by endogenous NSCs from the subventricular zone (SVZ) may restore function in the stroke-damaged striatum. To evaluate the potential clinical impact of these findings, we analyzed the spatial relationship of infarcts to the SVZ and the proportion of individuals with striatal lesions in a consecutive series of ischaemic stroke patients. METHODS: Patients aged 20-75 years with first-ever ischaemic stroke underwent DW-MRI of the brain within 4 days after stroke onset. We analyzed location, size, number of acute focal ischaemic abnormalities and their spatial relationship to the SVZ. Stroke severity was assessed using NIH Stroke Scale (NIHSS). RESULTS: Of 108 included patients, the distance from the nearest margin of the infarct(s) to the SVZ was ≤2 mm in 51/102 patients with visible ischaemic lesions on DW-MRI. Twenty-four patients had involvement of striatum. Eight of these had predominantly striatal lesions, that is >50% of the total ischaemic lesion volume was located in caudate nucleus and/or putamen. These 8 patients had a median NIHSS of 3. CONCLUSIONS: Many stroke patients have infarcts located close to the SVZ, providing some supportive evidence that optimized endogenous neurogenesis may have therapeutic potential. However, predominantly striatal infarcts are rare and tend to give mild neurological deficits, indicating that striatum should not be the primary target for neuronal replacement efforts in humans.
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| 4. |
- Knutsson, Linda, et al.
(författare)
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Absolute quantification of cerebral blood flow: correlation between dynamic susceptibility contrast MRI and model-free arterial spin labeling.
- 2010
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Ingår i: Magnetic Resonance Imaging. - : Elsevier BV. - 1873-5894 .- 0730-725X. ; 28:1, s. 1-7
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Tidskriftsartikel (refereegranskat)abstract
- PURPOSE: To compare absolute cerebral blood flow (CBF) estimates obtained by model-free arterial spin labeling (ASL) and dynamic susceptibility contrast MRI (DSC-MRI), corrected for partial volume effects (PVEs). METHODS: CBF was measured using DSC-MRI and model-free ASL (quantitative signal targeting with alternating radiofrequency labeling of arterial regions) at 3 T in 15 subjects with brain tumor, and the two modalities were compared with regard to CBF estimates in normal gray matter (GM) and DSC-to-ASL CBF ratios in selected tumor regions. The DSC-MRI CBF maps were calculated using a global arterial input function (AIF) from the sylvian-fissure region, but, in order to minimize PVEs, the AIF time integral was rescaled by a venous output function time integral obtained from the sagittal sinus. RESULTS: In GM, the average DSC-MRI CBF estimate was 150+/-45 ml/(min 100 g) (mean+/-SD) while the corresponding ASL CBF was 44+/-10 ml/(min 100 g). The linear correlation between GM CBF estimates obtained by DSC-MRI and ASL was r=.89, and observed DSC-to-ASL CBF ratios differed by less than 3% between GM and tumor regions. CONCLUSIONS: A satisfactory positive linear correlation between the CBF estimates obtained by model-free ASL and DSC-MRI was observed, and DSC-to-ASL CBF ratios showed no obvious tissue dependence.
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| 5. |
- Kvickstrom, Pia, et al.
(författare)
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Selective frontal neurodegeneration of the inferior fronto-occipital fasciculus in progressive supranuclear palsy (PSP) demonstrated by diffusion tensor tractography
- 2011
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Ingår i: BMC Neurology. - : Springer Science and Business Media LLC. - 1471-2377. ; 11
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Tidskriftsartikel (refereegranskat)abstract
- Background: The clinical presentation in progressive supranuclear palsy (PSP), an atypical parkinsonian disorder, includes varying degrees of frontal dysexecutive symptoms. Using diffusion tensor imaging (DTI) and tractography (DTT), we investigated whether diffusion changes and atrophy of the inferior fronto-occipital fasciculus (IFO) occurs in PSP and if these changes correlate with disease stage and clinical phenotype. The corticospinal tract (CST), which is often involved in PSP, was investigated for comparison. Methods: DTI of the whole brain was performed with a 3 T MR scanner using a single shot-EPI sequence with diffusion encoding in 48 directions. Scans were obtained in patients with PSP (n = 13) and healthy age-matched controls (n = 12). DTT of the IFO and CST was performed with the PRIDE fibre tracking tool (Philips Medical System). Fractional anisotropy (FA) and apparent diffusion coefficient (ADC) were calculated and correlated with disease stage and clinical phenotype. Results: In patients with PSP, significantly decreased FA and increased ADC was found in the frontal part of IFO compared with the medial and occipital parts of IFO, as well as compared to controls. Four of the thirteen patients with PSP showed a marked decrease in the number of tracked voxels in the frontal part of IFO. These findings were most pronounced in patients with severe frontal cognitive symptoms, such as dysexecutive problems, apathy and personality change. There was a strong correlation (r(2) = -0.84; p < 0,001) between disease stage and FA and ADC values in the CST. Conclusions: DTT for identification of neuronal tracts with subsequent measurement of FA and ADC is a useful diagnostic tool for demonstrating patterns of neuronal tract involvement in neurodegenerative disease. In selected tracts, FA and ADC values might act as surrogate markers for disease stage.
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| 6. |
- Looi, Jeffrey C. L., et al.
(författare)
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Morphometric analysis of subcortical structures in progressive supranuclear palsy: In vivo evidence of neostriatal and mesencephalic atrophy
- 2011
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Ingår i: Psychiatry Research: Neuroimaging. - : Elsevier BV. - 0925-4927. ; 194:2, s. 163-175
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Tidskriftsartikel (refereegranskat)abstract
- Progressive supranuclear palsy (PSP) is a neurodegenerative disease characterized by gait and postural disturbance, gaze palsy, apathy, decreased verbal fluency and dysexecutive symptoms, with some of these clinical features potentially having origins in degeneration of frontostriatal circuits and the mesencephalon. This hypothesis was investigated by manual segmentation of the caudate and putamen on MRI scans, using previously published protocols, in 15 subjects with PSP and 15 healthy age-matched controls. Midbrain atrophy was assessed by measurement of mid-sagittal area of the midbrain and pons. Shape analysis of the caudate and putamen was performed using spherical harmonics (SPHARM-PDM, University of North Carolina). The sagittal pons area/midbrain area ratio (P/M ratio) was significantly higher in the PSP group, consistent with previous findings. Significantly smaller striatal volumes were found in the PSP group - putamina were 10% smaller and caudate volumes were 17% smaller than in controls after controlling for age and intracranial volume. Shape analysis revealed significant shape deflation in PSP in the striatum, compared to controls; with regionally significant change relevant to frontostriatal and corticostriatal circuits in the caudate. Thus, in a clinically diagnosed and biomarker-confirmed cohort with early PSP, we demonstrate that neostriatal volume and shape are significantly reduced in vivo. The findings suggest a neostriatal and mesencephalic structural basis for the clinical features of PSP leading to frontostriatal and mesocortical-striatal circuit disruption. (C) 2011 Elsevier Ireland Ltd. All rights reserved.
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| 7. |
- Looi, Jeffrey C. L., et al.
(författare)
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The Australian, US, Scandinavian Imaging Exchange (AUSSIE): an innovative, virtually-integrated health research network embedded in health care
- 2014
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Ingår i: Australasian Psychiatry. - : SAGE Publications. - 1039-8562 .- 1440-1665. ; 22:3, s. 260-265
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Tidskriftsartikel (refereegranskat)abstract
- Objective: To describe the development, design and function of an innovative international clinical research network for neuroimaging research, based in Australia, within a joint state health service/medical school. This Australian, US, Scandinavian Imaging Exchange (AUSSIE) network focuses upon identifying neuroimaging biomarkers for neuropsychiatric and neurodegenerative disease. Methods: We describe a case study of the iterative development of the network, identifying characteristic features and methods which may serve as potential models for virtual clinical research networks. This network was established to analyse clinically-derived neuroimaging data relevant to neuropsychiatric and neurodegenerative disease, specifically in relation to subcortical brain structures. Results: The AUSSIE network has harnessed synergies from the individual expertise of the component groups, primarily clinical neuroscience researchers, to analyse a variety of clinical data. Conclusion: AUSSIE is an active virtual clinical research network, analogous to a connectome, which is embedded in health care and has produced significant research, advancing our understanding of neuropsychiatric and neurodegenerative disease through the lens of neuroimaging.
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| 8. |
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| 9. |
- Lätt, Jimmy, et al.
(författare)
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Regional values of diffusional kurtosis estimates in the healthy brain.
- 2013
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Ingår i: Journal of Magnetic Resonance Imaging. - : Wiley. - 1522-2586 .- 1053-1807. ; 37:3, s. 610-618
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Tidskriftsartikel (refereegranskat)abstract
- PURPOSE: To provide estimates of the diffusional kurtosis in the healthy brain in anatomically defined areas and list these along previously reported values in pathologies. MATERIALS AND METHODS: Thirty-six volunteers (mean age = 33.1 years; range, 19-64 years) underwent diffusional kurtosis imaging. Mean kurtosis (MK), radial kurtosis (RK), mean diffusivity (MD), radial diffusivity (RD), and fractional anisotropy (FA) were determined in 26 anatomical structures. Parameter estimates were assessed regarding age dependence. RESULTS: MK varied from 1.38 in the splenium of the corpus callosum to 0.66 in the caudate head, MD varied from 0.68 to 0.62 μm(2) /ms and FA from 0.87 to 0.29. MK, and FA showed a strong positive correlation, RK and RD a strong negative correlation. Parameter estimates showed age correlation in some regions; also the average MK and RK for all WM and all GM areas, respectively, were negatively correlated with age. CONCLUSION: DKI parameter estimates MK and RK varied depending on the anatomical region and varied with age in pooled WM and GM data. MK estimates in the internal capsule, corpus callosum, and thalamus were consistent with previous studies. The range of values of MK and RK in healthy brain overlapped with that in pathologies. J. Magn. Reson. Imaging 2012. © 2012 Wiley Periodicals, Inc.
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| 10. |
- Löve, Askell, et al.
(författare)
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Hybrid iterative reconstruction algorithm in brain CT: a radiation dose reduction and image quality assessment study.
- 2013
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Ingår i: Acta radiologica (Stockholm, Sweden : 1987). - : SAGE Publications. - 1600-0455 .- 0284-1851.
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Tidskriftsartikel (refereegranskat)abstract
- Iterative reconstruction (IR) algorithms improve image quality and allow for radiation dose reduction in CT. Dose reduction is particularly challenging in brain CT where good low-contrast resolution is essential. Ideally, evaluation of image quality combines objective measurements and subjective assessment of clinically relevant quality criteria. Subjective assessment is associated with various pitfalls and biases.
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