SwePub
Sök i SwePub databas

  Utökad sökning

Träfflista för sökning "WFRF:(Lätt Jimmy) "

Sökning: WFRF:(Lätt Jimmy)

  • Resultat 1-50 av 78
Sortera/gruppera träfflistan
   
NumreringReferensOmslagsbildHitta
1.
  • Askaner, Krister, et al. (författare)
  • Differentiation of Brain Metastases due to Primary Malignancy and Glioblastomas using Dynamic Susceptibility Contrast-Enhanced MR at 3T
  • 2017
  • Konferensbidrag (refereegranskat)abstract
    • Purpose:To find out differences in cerebral blood volume (CBV) maps derived from dynamic susceptibility contrast-enhanced magnetic resonance imaging (DSCE-MRI) in glioblastomas and cerebral metastases. The main purpose was to compare CBV maps between metastases with different primary malignancies. Furthermore the metastasis group was compared with the glioblastoma group.Method:Conventional imaging and DSCE-MRI using 3T MRI system was performed in 114 patients, 38 glioblastomas and 76 metastases, 32 lung, 12 breast, 12 melanoma, 10 gastrointestinal (GI), and 10 other. CBV values were measured in the solid tumor area, peritumoral edema, area adjacent to peritumoral edema, and in normal apparent white matter in contralateral semioval center. The four subgroups of metastases were compared with one-way ANOVA to determine differences in CBV of significance. CBV values in glioblastomas and metastases were then statistically compared using paired t-test. Receiver -operating characteristic analysis was used to determine optimal cut-off values when parameters showed statistical differences.Results:There were no significantly differences in CBV between the four subgroups of metastases. CBV in the peritumoral edema significantly differentiated metastases from glioblastomas, p=0.0001. CBV cutoff value of 2.3 yielded a sensitivity, specificity, positive predictive value, and negative predictive value of 87, 87, 71, and 91% respectively. Conclusions:Differentiation of glioblastomas and metastases is possible using DSCE-MRI. No statistically significant differences regarding CBV between metastases from lung, breast, melanoma, and GI were detected.
  •  
2.
  • Blomstergren, Adam, et al. (författare)
  • Evaluation of reproducibility in MRI quantitative volumetric assessment and its role in the prediction of overall survival and progression-free survival in glioblastoma
  • 2019
  • Ingår i: Acta Radiologica. - : SAGE Publications. - 0284-1851 .- 1600-0455. ; 60:4, s. 516-525
  • Tidskriftsartikel (refereegranskat)abstract
    • Background: Residual tumor volume (RTV) and extent of resection (EOR) have previously been shown to affect survival in glioblastoma (GB) patients. Quantitative radiological assessment (QRA) of these factors could potentially affect clinical decision-making in the postoperative period. Purpose: The first aim was to evaluate the reproducibility of different volume estimation methods of RTV and EOR by comparing QRA with subjective visual estimation and with objective volume estimations. The second aim was to clarify whether QRA of RTV and EOR would provide accuracy in predicting progression-free survival (PFS) and overall survival (OS) in GB patients. Material and Methods: Seventy GB patients were studied retrospectively. Reproducibility of QRA was compared to conventional visual analysis. Intra-rater agreement between two repeated measurements of 25 patients was calculated. QRA for RTV and EOR was made for the entire study population. Survival analysis was performed by multivariate cox-regression analysis. Results: QRA of RTV and EOR gave superior intra-rater agreement compared to subjective evaluation. Multivariate survival analysis showed prognostic significance on 18 months PFS (hazard ratio [HR] = 0.44, P = 0.003) and OS (HR = 0.42, P = 0.012) at RTV < 1.6 mL and with EOR > 96% on PFS (HR = 2.152, P = 0.005) but not on OS (HR = 1.92, P = 0.053). Conclusion: QRA of tumor volumes is more robust compared to standard evaluation methods. Since EOR and RTV are correlated to the prognosis in GB, quantitative analysis of tumor volumes could aid decision-making and patient management postoperatively.
  •  
3.
  • Durmo, Faris, et al. (författare)
  • Assessment of Amide proton transfer weighted (APTw) MRI for pre-surgical prediction of final diagnosis in gliomas
  • 2020
  • Ingår i: PLoS ONE. - : Public Library of Science (PLoS). - 1932-6203. ; 15:12
  • Tidskriftsartikel (refereegranskat)abstract
    • PURPOSE: Radiological assessment of primary brain neoplasms, both high (HGG) and low grade tumors (LGG), based on contrast-enhancement alone can be inaccurate. We evaluated the radiological value of amide proton transfer weighted (APTw) MRI as an imaging complement for pre-surgical radiological diagnosis of brain tumors.METHODS: Twenty-six patients were evaluated prospectively; (22 males, 4 females, mean age 55 years, range 26-76 years) underwent MRI at 3T using T1-MPRAGE pre- and post-contrast administration, conventional T2w, FLAIR, and APTw imaging pre-surgically for suspected primary/secondary brain tumor. Assessment of the additional value of APTw imaging compared to conventional MRI for correct pre-surgical brain tumor diagnosis. The initial radiological pre-operative diagnosis was based on the conventional contrast-enhanced MR images. The range, minimum, maximum, and mean APTw signals were evaluated. Conventional normality testing was performed; with boxplots/outliers/skewness/kurtosis and a Shapiro-Wilk's test. Mann-Whitney U for analysis of significance for mean/max/min and range APTw signal. A logistic regression model was constructed for mean, max, range and Receiver Operating Characteristic (ROC) curves calculated for individual and combined APTw signals.RESULTS: Conventional radiological diagnosis prior to surgery/biopsy was HGG (8 patients), LGG (12 patients), and metastasis (6 patients). Using the mean and maximum: APTw signal would have changed the pre-operative evaluation the diagnosis in 8 of 22 patients (two LGGs excluded, two METs excluded). Using a cut off value of >2.0% for mean APTw signal integral, 4 of the 12 radiologically suspected LGG would have been diagnosed as high grade glioma, which was confirmed by histopathological diagnosis. APTw mean of >2.0% and max >2.48% outperformed four separate clinical radiological assessments of tumor type, P-values = .004 and = .002, respectively.CONCLUSIONS: Using APTw-images as part of the daily clinical pre-operative radiological evaluation may improve diagnostic precision in differentiating LGGs from HGGs, with potential improvement of patient management and treatment.
  •  
4.
  • Durmo, Faris, et al. (författare)
  • Brain Tumor Characterization Using Multibiometric Evaluation of MRI
  • 2018
  • Ingår i: Tomography : a journal for imaging research. - : MDPI AG. - 2379-1381. ; 4:1, s. 14-25
  • Tidskriftsartikel (refereegranskat)abstract
    • The aim was to evaluate volume, diffusion, and perfusion metrics for better presurgical differentiation between high-grade gliomas (HGG), low-grade gliomas (LGG), and metastases (MET). For this retrospective study, 43 patients with histologically verified intracranial HGG (n = 18), LGG (n = 10), and MET (n = 15) were chosen. Preoperative magnetic resonance data included pre- and post-gadolinium contrast-enhanced T1-weighted fluid-attenuated inversion recover, cerebral blood flow (CBF), cerebral blood volume (CBV), fractional anisotropy, and apparent diffusion coefficient maps used for quantification of magnetic resonance biometrics by manual delineation of regions of interest. A binary logistic regression model was applied for multiparametric analysis and receiver operating characteristic (ROC) analysis. Statistically significant differences were found for normalized-ADC-tumor (nADC-T), normalized-CBF-tumor (nCBF-T), normalized-CBV-tumor (nCBV-T), and normalized-CBF-edema (nCBF-E) between LGG and HGG, and when these metrics were combined, HGG could be distinguished from LGG with a sensitivity and specificity of 100%. The only metric to distinguish HGG from MET was the normalized-ADC-E with a sensitivity of 68.8% and a specificity of 80%. LGG can be distinguished from MET by combining edema volume (Vol-E), Vol-E/tumor volume (Vol-T), nADC-T, nCBF-T, nCBV-T, and nADC-E with a sensitivity of 93.3% and a specificity of 100%. The present study confirms the usability of a multibiometric approach including volume, perfusion, and diffusion metrics in differentially diagnosing brain tumors in preoperative patients and adds to the growing body of evidence in the clinical field in need of validation and standardization.
  •  
5.
  • Durmo, Faris, et al. (författare)
  • Multivoxel 1H-MR Spectroscopy Biometrics for Preoprerative Differentiation Between Brain Tumors
  • 2018
  • Ingår i: Tomography : a journal for imaging research. - : MDPI AG. - 2379-1381. ; 4:4, s. 172-181
  • Tidskriftsartikel (refereegranskat)abstract
    • We investigated multivoxel proton magnetic resonance spectroscopy (1H-MRS) biometrics for preoperative differentiation and prognosis of patients with brain metastases (MET), low-grade glioma (LGG) and high-grade glioma (HGG). In total, 33 patients (HGG, 14; LGG, 9; and 10 MET) were included. 1H-MRS imaging (MRSI) data were assessed and neurochemical profiles for metabolites N-acetyl aspartate (NAA) + NAAG(NAA), Cr + PCr(total creatine, tCr), Glu + Gln(Glx), lactate (Lac), myo-inositol(Ins), GPC + PCho(total choline, tCho), and total lipids, and macromolecule (tMM) signals were estimated. Metabolites were reported as absolute concentrations or ratios to tCho or tCr levels. Voxels of interest in an MRSI matrix were labeled according to tissue. Logistic regression, receiver operating characteristic, and Kaplan-Meier survival analysis was performed. Across HGG, LGG, and MET, average Ins/tCho was shown to be prognostic for overall survival (OS): low values (≤1.29) in affected hemisphere predicting worse OS than high values (>1.29), (log rank < 0.007). Lip/tCho and Ins/tCho combined showed 100% sensitivity and specificity for both HGG/LGG (P < .001) and LGG/MET (P < .001) measured in nonenhancing/contrast-enhancing lesional tissue. Combining tCr/tCho in perilesional edema with tCho/tCr and NAA/tCho from ipsilateral normal- appearing tissue yielded 100% sensitivity and 81.8% specificity (P < .002) for HGG/MET. Best single biomarker: Ins/tCho for HGG/LGG and total lipid/tCho for LGG/MET showed 100% sensitivity and 75% and 100% specificity, respectively. HGG/MET; NAA/tCho showed 75% sensitivity and 84.6% specificity. Multivoxel 1H-MRSI provides prognostic information for OS for HGG/LGG/MET and a multibiometric approach for differentiation may equal or outperform single biometrics.
  •  
6.
  •  
7.
  • Eriksson, Sam, et al. (författare)
  • Changes in apparent diffusion coefficient and pathological response in colorectal liver metastases after preoperative chemotherapy
  • 2023
  • Ingår i: Acta Radiologica. - : SAGE Publications. - 0284-1851 .- 1600-0455. ; 64:1, s. 51-57
  • Tidskriftsartikel (refereegranskat)abstract
    • Background: The pathological response to preoperative chemotherapy of colorectal liver metastases (CRLMs) is predictive of long-term prognosis after liver resection. Accurate preoperative assessment of chemotherapy response could enable treatment optimization. Purpose: To investigate whether changes in lesion-apparent diffusion coefficient (ADC) measured with diffusion-weighted magnetic resonance imaging (MRI) can be used to assess pathological treatment response in patients with CRLMs undergoing preoperative chemotherapy. Material and Methods: Patients who underwent liver resection for CRLMs after preoperative chemotherapy between January 2011 and December 2019 were retrospectively included if they had undergone MRI before and after preoperative chemotherapy on the same 1.5-T MRI scanner with diffusion-weighted imaging with b-values 50, 400, and 800 s/mm2. The pathological chemotherapy response was assessed using the tumor regression grade (TRG) by AJCC/CAP. Lesions were divided into two groups: pathological responding (TRG 0–2) and non-responding (TRG 3). The change in lesion ADC after preoperative chemotherapy was compared between responding and non-responding lesions. Results: A total of 27 patients with 49 CRLMs were included, and 24/49 lesions showed a pathological chemotherapy response. After chemotherapy, ADC increased in both pathological responding (pretreatment ADC: 1.26 [95% confidence interval (CI)=1.06–1.37] vs. post-treatment ADC: 1.33 [95% CI=1.13–1.56] × 10−3 mm2/s; P = 0.026) and non-responding lesions (1.12 [95% CI=0.980–1.21] vs. 1.20 [95% CI=1.09–1.43] × 10−3 mm2/s; P = 0.018). There was no difference in median relative difference in ADC after chemotherapy between pathological responding and non-responding lesions (15.8 [95% CI=1.42–26.3] vs. 7.17 [95% CI=−4.31 to 31.2]%; P = 0.795). Conclusion: Changes in CRLM ADCs did not differ between pathological responding and non-responding lesions.
  •  
8.
  • Falk Delgado, Anna, et al. (författare)
  • Diffusion kurtosis imaging of gliomas grades II and III : a study of perilesional tumor infiltration, tumor grades and subtypes at clinical presentation
  • 2017
  • Ingår i: Radiology and Oncology. - : Walter de Gruyter GmbH. - 1318-2099 .- 1581-3207. ; 51:2, s. 121-129
  • Tidskriftsartikel (refereegranskat)abstract
    • Background. Diffusion kurtosis imaging (DKI) allows for assessment of diffusion influenced by microcellular structures. We analyzed DKI in suspected low-grade gliomas prior to histopathological diagnosis. The aim was to investigate if diffusion parameters in the perilesional normal-appearing white matter (NAWM) differed from contralesional white matter, and to investigate differences between glioma malignancy grades II and III and glioma subtypes (astrocytomas and oligodendrogliomas).Patients and methods. Forty-eight patients with suspected low-grade glioma were prospectively recruited to this institutional review board-approved study and investigated with preoperative DKI at 3T after written informed consent. Patients with histologically proven glioma grades II or III were further analyzed (n=35). Regions of interest (ROIs) were delineated on T2FLAIR images and co-registered to diffusion MRI parameter maps. Mean DKI data were compared between perilesional and contralesional NAWM (student's t-test for dependent samples, Wilcoxon matched pairs test). Histogram DKI data were compared between glioma types and glioma grades (multiple comparisons of mean ranks for all groups). The discriminating potential for DKI in assessing glioma type and grade was assessed with receiver operating characteristics (ROC) curves.Results. There were significant differences in all mean DKI variables between perilesional and contralesional NAWM (p=< 0.000), except for axial kurtosis (p=0.099). Forty-four histogram variables differed significantly between glioma grades II (n=23) and III (n=12) (p=0.003-0.048) and 10 variables differed significantly between ACs (n=18) and ODs (n=17) (p=0.011-0.050). ROC curves of the best discriminating variables had an area under the curve (AUC) of 0.657-0.815.Conclusions. Mean DKI variables in perilesional NAWM differ significantly from contralesional NAWM, suggesting altered microstructure by tumor infiltration not depicted on morphological MRI. Histogram analysis of DKI data identifies differences between glioma grades and subtypes.
  •  
9.
  •  
10.
  •  
11.
  • Falk Delgado, Anna, et al. (författare)
  • Preoperative Quantitative MR Tractography Compared with Visual Tract Evaluation in Patients with Neuropathologically Confirmed Gliomas Grades II and III : A Prospective Cohort Study
  • 2016
  • Ingår i: Radiology research and practice. - : Hindawi Limited. - 2090-1941 .- 2090-195X. ; 2016:1, s. 1-15
  • Tidskriftsartikel (refereegranskat)abstract
    • Background and Purpose. Low-grade gliomas show infiltrative growth in white matter tracts. Diffusion tensor tractography can noninvasively assess white matter tracts. The aim was to preoperatively assess tumor growth in white matter tracts using quantitative MR tractography (3T). The hypothesis was that suspected infiltrated tracts would have altered diffusional properties in infiltrated tract segments compared to noninfiltrated tracts. Materials and Methods. Forty-eight patients with suspected low-grade glioma were included after written informed consent and underwent preoperative diffusion tensor imaging in this prospective review-board approved study. Major white matter tracts in both hemispheres were tracked, segmented, and visually assessed for tumor involvement in thirty-four patients with gliomas grade II or III (astrocytomas or oligodendrogliomas) on postoperative neuropathological evaluation. Relative fractional anisotropy (rFA) and mean diffusivity (rMD) in tract segments were calculated and compared with visual evaluation and neuropathological diagnosis. Results. Tract segment infiltration on visual evaluation was associated with a lower rFA and high rMD in a majority of evaluated tract segments (89% and 78%, resp.). Grade II and grade III gliomas had similar infiltrating behavior. Conclusion. Quantitative MR tractography corresponds to visual evaluation of suspected tract infiltration. It may be useful for an objective preoperative evaluation of tract segment involvement.
  •  
12.
  • Follin, Cecilia, et al. (författare)
  • Associations between Metabolic Risk Factors and the Hypothalamic Volume in Childhood Leukemia Survivors Treated with Cranial Radiotherapy.
  • 2016
  • Ingår i: PLoS ONE. - : Public Library of Science (PLoS). - 1932-6203. ; 11:1
  • Tidskriftsartikel (refereegranskat)abstract
    • Metabolic complications are prevalent in individuals treated with cranial radiotherapy (CRT) for childhood acute lymphoblastic leukemia (ALL). The hypothalamus is a master regulator of endocrine and metabolic control. The aim of this study was to investigate whether the hypothalamic volume would be associated to metabolic parameters in ALL survivors. Thirty-eight (21 women) survivors participated in this study 34 years after diagnosis and with a median age of 38 (27-46) years. All were treated with a median CRT dose of 24 Gy and 11 years (3-13) of complete hormone supplementation. Comparisons were made to 31 matched controls. We performed analyses of fat mass, fat free mass, plasma (p)-glucose, p-insulin, Homa-Index (a measure of insulin resistance), serum (s)-leptin, s-ghrelin and of the hypothalamic volume in scans obtained by magnetic resonance imaging (MRI) at 3 Tesla. Serum leptin/kg fat mass (r = -0.4, P = 0.04) and fat mass (r = -0.4, P = 0.01) were negatively correlated with the HT volume among ALL survivors, but not among controls. We also detected significantly higher BMI, waist, fat mass, p-insulin, Homa-Index, leptin/kg fat mass and s-ghrelin and significantly lower fat free mass specifically among female ALL survivors (all P<0.01). Interestingly, s-ghrelin levels increased with time since diagnosis and with low age at diagnosis for childhood ALL. Our results showed that leptin/kg fat mass and fat mass were associated with a reduced HT volume 34 years after ALL diagnosis and that women treated with CRT after ALL are at high risk of metabolic abnormalities. Taken together our data suggest that the hypothalamus is involved in the metabolic consequences after CRT in ALL survivors.
  •  
13.
  • Follin, Cecilia, et al. (författare)
  • Hypothalamic dysfunction revealed by magnetic resonance diffusion tensor imaging in childhood leukemia survivors treated with cranial radiotherapy but not in craniopharyngeoma survivors
  • 2016
  • Konferensbidrag (refereegranskat)abstract
    • Background: Metabolic complications with obesity are frequent in childhood acute lymphoblastic leukemia (ALL) survivors treated with cranial radiotherapy (CRT). Childhood onset Craniopharyngioma (CP) survivors without hypothalamic (HT) involvement are spared gross obesity. Magnetic resonance diffusion tensor imaging (DTI) provides information of microstructure function of the brain and quantified as fractional anisotrophy (FA), mean diffusivity (MD), axial and radial diffusivity (AD, RD). Since MD in HT is reportedly impaired (increased) in obese compared to non-obese subjects, we investigated DTI in the HT.Methods: Twenty nine ALL survivors on hormone supplementation were investigated 34 years after CRT (24 Gy). 17 CO-CP survivors with hormone supplementation but without HT damage were investigated. Comparisons were made with these two patient populations to 27 matched controls regarding DTI parameters in the HT and for BMI, fat mass, fat free mass and waist/hip measurements.Results: We recorded reduced FA (0.27 vs 0.29, P=0.04), and increased MD (1.13 vs 1.00, P<0.001), AD (1.41 vs 1.25, P<0.001), and RD (0.99 vs 0.86, P<0.001) in the right HT and increased MD (1.42 vs 1.25, P<0.001), AD (1.75 vs 1.58, P<0.001), and RD (1.25 vs 1.04, P<0.001) in left HT in ALL survivors compared to matched controls. The CPs showed no difference in the HT for these parameters compared to controls. ALL survivors with a BMI ≥ 25 showed elevated MD (P=0.03) and AD (P=0.02) compared to ALL survivors with a BMI < 25 and compared to controls with BMI ≥ 25 in the right HT. This was not the case in CP survivors or in controls.Conclusions: Thirty four years after CRT for ALL, DTI measures are deranged in the HT. ALL survivors with a BMI ≥ 25 were presented with worse HT dysfunction. CP survivors were unaffected. The present data suggests changes in the microstructure of the HT in these ALL survivors.
  •  
14.
  • Follin, Cecilia, et al. (författare)
  • Impaired brain metabolism and neurocognitive function in childhood leukemia survivors despite complete hormone supplementation in adulthood
  • 2016
  • Ingår i: Psychoneuroendocrinology. - : Elsevier BV. - 0306-4530 .- 1873-3360. ; 73, s. 157-165
  • Tidskriftsartikel (refereegranskat)abstract
    • Cranial radiotherapy is a known risk factor for neurocognitive impairment in survivors of childhood acute lymphoblastic leukemia (ALL). Understanding the nature of cognitive dysfunction during adulthood in ALL survivors is important as it has an impact on major life situations. Thirty-eight (21 women) ALL survivors were investigated 34 years after diagnosis. Median-age was 38 (27–46) years. All were treated with a CRT dose of 24 Gy and 11 years (3–13) of complete hormone supplementation. Comparisons were made to 29 matched controls. Assessments of magnetic resonance spectroscopy (white and grey matter metabolic alterations), brain volume and neuropsychological tests were performed. ALL survivors demonstrate a generally lower performance in neuropsychological tests. ALL survivors scored lower than controls in vocabulary (p < 0.001), memory (p < 0.001), learning capacity (p < 0.001), spatial ability (p < 0.001), executive functions and attention (p < 0.001) 34 years after ALL treatment. Compared to controls ALL survivors had reduced white matter (WM) (492 vs 536 cm3, p < 0.001) and grey matter (GM) volumes (525 vs 555 cm3, p = 0.001). ALL survivors had lower levels of WM N-acetyl aspartate/creatin (NAA/Cr) (1.48 vs 1.63, p = 0.004), WM NAA + NAAG (N-acetylaspartylglutamate)/Cr (1.61 vs 1.85, p < 0.001) and lower levels of GM NAA/Cr (1.18 vs 1.30, p = 0.001) and GM NAA + NAAG/Cr (1.28 vs 1.34, p = 0.01) compared to controls. ALL survivors had higher levels in WM MI (Myoinositol)/NAA (0.65 vs 0.56, p = 0.01) concentrations compared to controls. There was a significantly negative correlation of years since ALL diagnosis to WM NAA + NAAG/Cr (r = −0.4, p = 0.04) in ALL survivors. The present study shows impaired brain metabolism detected by MRS, reduced brain volumes and neurocognitive impairment in childhood ALL survivors treated with cranial radiotherapy and chemotherapy, despite complete hormone substitution. We also report an impairment of metabolites correlated to time since treatment and a progressive impairment in sustained attention, suggesting an accelerated aging in the irradiated brain. Following these survivors many decades, or throughout life, after treatment with cranial radiotherapy and chemotherapy is highly warranted for a broader understanding of long-term outcome in this patient group.
  •  
15.
  • Follin, Cecilia, et al. (författare)
  • Microstructural white matter alterations associated to neurocognitive deficits in childhood leukemia survivors treated with cranial radiotherapy–a diffusional kurtosis study
  • 2019
  • Ingår i: Acta Oncologica. - 0284-186X. ; 58:7, s. 1021-1028
  • Tidskriftsartikel (refereegranskat)abstract
    • Background: Cranial radiotherapy (CRT) is a known risk factor for neurocognitive impairment in survivors of childhood acute lymphoblastic leukemia (ALL). Diffusion tensor imaging (DTI) and diffusional kurtosis imaging (DKI) are MRI techniques that quantify microstructural changes in brain white matter (WM) and DKI is regarded as the more sensitive of them. Our aim was to more thoroughly understand the nature of cognitive deficits after cranial radiotherapy (CRT) in adulthood after childhood ALL. Material and methods: Thirty-eight (21 women) ALL survivors, median age 38 (27–46) years, were investigated at median 34 years after diagnosis. All had been treated with a CRT dose of 24 Gy and with 11 years of complete hormone supplementation. DTI and DKI parameters were determined and neurocognitive tests were performed in ALL survivors and 29 matched controls. Results: ALL survivors scored lower than controls in neurocognitive tests of vocabulary, memory, learning capacity, spatial ability, executive functions, and attention (p <.001). The survivors had altered DTI parameters in the fornix, uncinate fasciculus, and ventral cingulum (all p <.05) and altered DKI parameters in the fornix, uncinate fasciculus, and dorsal and ventral cingulum (p <.05). Altered DTI parameters in the fornix were associated with impaired episodic verbal memory (r = −0.40, p <.04). The left and right uncinate fasciculus (r = 0.6, p <.001), (r = −0.5, p <.02) as well as the right ventral cingulum (r = 0.5, p <.007) were associated with impaired episodic visual memory. Altered DKI parameters in the fornix, right uncinate fasciculus (r = 0.3, r = 0.05, p =.02), and ventral cingulum (r = 0.3, p =.02) were associated with impaired results of episodic visual memory. Conclusion: ALL survivors with cognitive deficits demonstrated microstructural damage in several WM tracts that were more extensive with DKI as compared to DTI; this might be a marker of radiation and chemotherapy neurotoxicity underlying cognitive dysfunction.
  •  
16.
  • Follin, Cecilia, et al. (författare)
  • Microstructure alterations in the hypothalamus in cranially radiated childhood leukaemia survivors but not in craniopharyngioma patients unaffected by hypothalamic damage
  • 2017
  • Ingår i: Clinical Endocrinology. - : Wiley. - 0300-0664. ; 87:4, s. 359-366
  • Tidskriftsartikel (refereegranskat)abstract
    • Objective: Metabolic complications are frequent in childhood leukaemia (ALL) survivors treated with cranial radiotherapy (CRT). These complications are potentially mediated by damage to the hypothalamus (HT), as childhood onset (CO) craniopharyngioma (CP) survivors without HT involvement are spared overt obesity. Diffusion tensor imaging (DTI) shows brain tissue microstructure alterations, by fractional anisotrophy (FA), mean diffusivity (MD), axial diffusivity (AD) and radial diffusivity (RD). We used DTI to determine the integrity of the microstructure of the HT in ALL survivors. Design: Case-control study. Patients: Three groups were included: (i) 27 CRT treated ALL survivors on hormone supplementation, (ii) 17 CO-CP survivors on hormone supplementation but without HT involvement and (iii) 27 matched controls. Measurements: DTI parameters of the HT were measured and body composition. Results: Microstructural alterations in the HT were more severe in ALL survivors with a BMI ≥25 than with BMI <25. Compared to controls, ALL survivors had reduced FA (P=.04), increased MD (P<.001), AD (P<.001) and RD (P<.001) in the right and left HT. In the right HT, ALL survivors with a BMI ≥25 showed elevated MD (P=.03) and AD (P=.02) compared to ALL survivors with BMI <25. In contrast, DTI parameters did not differ between CP survivors and controls. Conclusions: Long-term follow-up after CRT for ALL DTI measures were affected in the HT despite complete hormone replacement. The present data suggest that ALL survivors have demyelination and axonal loss in the HT.
  •  
17.
  • Hansson, Boel, et al. (författare)
  • Subjectively Reported Effects Experienced in an Actively Shielded 7T MRI: A Large-Scale Study.
  • 2020
  • Ingår i: Journal of magnetic resonance imaging : JMRI. - : Wiley. - 1522-2586 .- 1053-1807. ; 52:4, s. 1265-1276
  • Tidskriftsartikel (refereegranskat)abstract
    • Ultrahigh-field (UHF) MRI advances towards clinical use. Patient compliance is generally high, but few large-scale studies have investigated the effects experienced in 7T MRI systems, especially considering peripheral nerve stimulation (PNS) and caregiving.To evaluate the quantity, the intensity, and subjective experiences from short-term effects, focusing on the levels of comfort and compliance of subjects.Prospective.In all, 954 consecutive MRIs in 801 subjects for 3years.7T.After the 7T examination, a questionnaire was used to collect data.Descriptive statistics, Spearman's rank correlation, Mann-Whitney U-test, and t-test.The majority (63%) of subjects agreed that the MRI experience was comfortable and 93% would be willing to undergo future 7T MRI as a patient (5% undecided) and 82% for research purposes (12% undecided). The most common short-term effects experienced were dizziness (81%), inconsistent movement (68%), PNS (63%), headache (40%), nausea (32%), metallic taste (12%), and light flashes (8%). Of the subjects who reported having PNS (n = 603), 44% experienced PNS as "not uncomfortable at all," 45% as "little or very little uncomfortable," and 11% as "moderate to very much uncomfortable." Scanner room temperature was experienced more comfortable before (78%) than during (58%) examinations, and the noise level was acceptable by 90% of subjects. Anxiety before the examination was reported by 43%. Patients differed from healthy volunteers regarding an experience of headache, metallic taste, dizziness, or anxiety. Room for improvement was pointed out after 117 examinations concerning given information (n = 73), communication and sound system (n = 35), or nursing care (n = 15).Subjectively reported effects occur in actively shielded 7T MRI and include physiological responses and individual psychological issues. Although leaving room for improvement, few subjects experienced these effects being so uncomfortable that they would lead to aversion to future UHF examinations.1 TECHNICAL EFFICACY: Stage 5.
  •  
18.
  • Hansson, Oskar, et al. (författare)
  • Blood-based NfL : A biomarker for differential diagnosis of parkinsonian disorder
  • 2017
  • Ingår i: Neurology. - : Lippincott Williams & Wilkins. - 0028-3878 .- 1526-632X. ; 88:10, s. 930-937
  • Tidskriftsartikel (refereegranskat)abstract
    • Objective: To determine if blood neurofilament light chain (NfL) protein can discriminate between Parkinson disease (PD) and atypical parkinsonian disorders (APD) with equally high diagnostic accuracy as CSF NfL, and can therefore improve the diagnostic workup of parkinsonian disorders. Methods: The study included 3 independent prospective cohorts: the Lund (n = 278) and London (n = 117) cohorts, comprising healthy controls and patients with PD, progressive supranuclear palsy (PSP), corticobasal syndrome (CBS), and multiple system atrophy (MSA), as well as an early disease cohort (n = 109) of patients with PD, PSP, MSA, or CBS with disease duration ≤3 years. Blood NfL concentration was measured using an ultrasensitive single molecule array (Simoa) method, and the diagnostic accuracy to distinguish PD from APD was investigated. Results: We found strong correlations between blood and CSF concentrations of NfL (ρ ≥ 0.73-0.84, p ≤ 0.001). Blood NfL was increased in patients with MSA, PSP, and CBS (i.e., all APD groups) when compared to patients with PD as well as healthy controls in all cohorts (p < 0.001). Furthermore, in the Lund cohort, blood NfL could accurately distinguish PD from APD (area under the curve [AUC] 0.91) with similar results in both the London cohort (AUC 0.85) and the early disease cohort (AUC 0.81). Conclusions: Quantification of blood NfL concentration can be used to distinguish PD from APD. Blood-based NfL might consequently be included in the diagnostic workup of patients with parkinsonian symptoms in both primary care and specialized clinics. Classification of evidence: This study provides Class III evidence that blood NfL levels discriminate between PD and APD.
  •  
19.
  • Harper, Luke, et al. (författare)
  • Anterior cingulate sulcation is associated with onset and survival in frontotemporal dementia
  • 2023
  • Ingår i: Brain Communications. - 2632-1297. ; 5:5
  • Tidskriftsartikel (refereegranskat)abstract
    • Frontotemporal dementia is the second most common form of early onset dementia (<65 years). Despite this, there are few known disease-modifying factors. The anterior cingulate is a focal point of pathology in behavioural variant frontotemporal dementia. Sulcation of the anterior cingulate is denoted by the presence of a paracingulate sulcus, a tertiary sulcus developing, where present during the third gestational trimester and remaining stable throughout life. This study aims to examine the impact of right paracingulate sulcal presence on the expression and prognosis of behavioural variant frontotemporal dementia. This retrospective analysis drew its population from two clinical samples recruited from memory clinics at university hospitals in the USA and The Netherlands. Individuals with sporadic behavioural variant frontotemporal dementia were enrolled between 2000 and 2022 and followed up for an average of 7.71 years. T1-MRI data were evaluated for hemispheric paracingulate sulcal presence in accordance with an established protocol by two blinded raters. Outcome measures included age at onset, survival, cortical thickness and Frontotemporal Lobar Degeneration-modified Clinical Dementia Rating determined clinical disease progression. The study population consisted of 186 individuals with sporadic behavioural variant frontotemporal dementia (113 males and 73 females), mean age 63.28 years (SD 8.32). The mean age at onset was 2.44 years later in individuals possessing a right paracingulate sulcus [60.2 years (8.54)] versus individuals who did not [57.76 (8.05)], 95% confidence interval > 0.41, P = 0.02. Education was not associated with age at onset (β = -0.05, P = 0.75). The presence of a right paracingulate sulcus was associated with an 83% increased risk of death per year after age at onset (hazard ratio 1.83, confidence interval [1.09-3.07], P < 0.02), whilst the mean age at death was similar for individuals with a present and absent right paracingulate sulcus (P = 0.7). Right paracingulate sulcal presence was not associated with baseline cortical thickness. Right paracingulate sulcal presence is associated with disease expression and survival in sporadic behavioural variant frontotemporal dementia. Findings provide evidence of neurodevelopmental brain reserve in behavioural variant frontotemporal dementia that may be important in the design of trials for future therapeutic approaches.
  •  
20.
  • Helms, Gunther, et al. (författare)
  • Cross-vendor transfer and RF coil comparison of a high-resolution MP2RAGE protocol for brain imaging at 7T
  • 2020
  • Ingår i: Acta Scientiarum Lundensia. - 1651-5013. ; 2020:001, s. 1-12
  • Tidskriftsartikel (refereegranskat)abstract
    • Abstract. An established MP2RAGE protocol for semi-quantitative structural brain MRI was transferred from one 7T MR scanner to that of another vendor featuring comparable hardware, but opposite polarity. On this system, the scan time could be reduced from 11 to 8 minutes by elliptical k-space sampling. Three configurations of radio-frequency (RF) transmission were compared (single channel with quadrature slitting, two and eight channels of fixed phase delays). Data processing for offline calculation MP2RAGE images is described in detail. The DICOM scaling of scanner B entails a loss of precision and accuracy and stronger artifacts in regions of low RF field, which can be improved by dielectric pads. For comparison and multi-site studies, though, use of an identical scan protocol and identical RF hardware is recommended.
  •  
21.
  • Jakabek, David, et al. (författare)
  • Regional structural hypo- and hyperconnectivity of frontal–striatal and frontal–thalamic pathways in behavioral variant frontotemporal dementia
  • 2018
  • Ingår i: Human Brain Mapping. - : Wiley. - 1065-9471. ; 39:10, s. 4083-4093
  • Tidskriftsartikel (refereegranskat)abstract
    • Behavioral variant frontotemporal dementia (bvFTD) has been predominantly considered as a frontotemporal cortical disease, with limited direct investigation of frontal–subcortical connections. We aim to characterize the grey and white matter components of frontal–thalamic and frontal–striatal circuits in bvFTD. Twenty-four patients with bvFTD and 24 healthy controls underwent morphological and diffusion imaging. Subcortical structures were manually segmented according to published protocols. Probabilistic pathways were reconstructed separately from the dorsolateral, orbitofrontal and medial prefrontal cortex to the striatum and thalamus. Patients with bvFTD had smaller cortical and subcortical volumes, lower fractional anisotropy, and higher mean diffusivity metrics, which is consistent with disruptions in frontal–striatal–thalamic pathways. Unexpectedly, regional volumes of the striatum and thalamus connected to the medial prefrontal cortex were significantly larger in bvFTD (by 135% in the striatum, p =.032, and 217% in the thalamus, p =.004), despite smaller dorsolateral prefrontal cortex connected regional volumes (by 67% in the striatum, p =.002, and 65% in the thalamus, p =.020), and inconsistent changes in orbitofrontal cortex connected regions. These unanticipated findings may represent compensatory or maladaptive remodeling in bvFTD networks. Comparisons are made to other neuropsychiatric disorders suggesting a common mechanism of changes in frontal–subcortical networks; however, longitudinal studies are necessary to test this hypothesis.
  •  
22.
  • Jakabek, David, et al. (författare)
  • Structural and microstructural thalamocortical network disruption in sporadic behavioural variant frontotemporal dementia
  • 2023
  • Ingår i: NeuroImage: Clinical. - 2213-1582. ; 39, s. 1-11
  • Tidskriftsartikel (refereegranskat)abstract
    • Background: Using multi-block methods we combined multimodal neuroimaging metrics of thalamic morphology, thalamic white matter tract diffusion metrics, and cortical thickness to examine changes in behavioural variant frontotemporal dementia. (bvFTD). Method: Twenty-three patients with sporadic bvFTD and 24 healthy controls underwent structural and diffusion MRI scans. Clinical severity was assessed using the Clinical Dementia Rating scale and behavioural severity using the Frontal Behaviour Inventory by patient caregivers. Thalamic volumes were manually segmented. Anterior and posterior thalamic radiation fractional anisotropy and mean diffusivity were extracted using Tract-Based Spatial Statistics. Finally, cortical thickness was assessed using Freesurfer. We used shape analyses, diffusion measures, and cortical thickness as features in sparse multi-block partial least squares (PLS) discriminatory analyses to classify participants within bvFTD or healthy control groups. Sparsity was tuned with five-fold cross-validation repeated 10 times. Final model fit was assessed using permutation testing. Additionally, sparse multi-block PLS was used to examine associations between imaging features and measures of dementia severity. Results: Bilateral anterior-dorsal thalamic atrophy, reduction in mean diffusivity of thalamic projections, and frontotemporal cortical thinning, were the main features predicting bvFTD group membership. The model had a sensitivity of 96%, specificity of 68%, and was statistically significant using permutation testing (p = 0.012). For measures of dementia severity, we found similar involvement of regional thalamic and cortical areas as in discrimination analyses, although more extensive thalamo-cortical white matter metric changes. Conclusions: Using multimodal neuroimaging, we demonstrate combined structural network dysfunction of anterior cortical regions, cortical-thalamic projections, and anterior thalamic regions in sporadic bvFTD.
  •  
23.
  • Kvickstrom, Pia, et al. (författare)
  • Selective frontal neurodegeneration of the inferior fronto-occipital fasciculus in progressive supranuclear palsy (PSP) demonstrated by diffusion tensor tractography
  • 2011
  • Ingår i: BMC Neurology. - : Springer Science and Business Media LLC. - 1471-2377. ; 11
  • 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.
  •  
24.
  • Lampinen, Björn, et al. (författare)
  • Optimal experimental design for filter exchange imaging: Apparent exchange rate measurements in the healthy brain and in intracranial tumors.
  • 2017
  • Ingår i: Magnetic Resonance in Medicine. - : Wiley. - 1522-2594 .- 0740-3194. ; 77:3, s. 1104-1114
  • Tidskriftsartikel (refereegranskat)abstract
    • PURPOSE: Filter exchange imaging (FEXI) is sensitive to the rate of diffusional water exchange, which depends, eg, on the cell membrane permeability. The aim was to optimize and analyze the ability of FEXI to infer differences in the apparent exchange rate (AXR) in the brain between two populations.METHODS: A FEXI protocol was optimized for minimal measurement variance in the AXR. The AXR variance was investigated by test-retest acquisitions in six brain regions in 18 healthy volunteers. Preoperative FEXI data and postoperative microphotos were obtained in six meningiomas and five astrocytomas.RESULTS: Protocol optimization reduced the coefficient of variation of AXR by approximately 40%. Test-retest AXR values were heterogeneous across normal brain regions, from 0.3 ± 0.2 s-1 in the corpus callosum to 1.8 ± 0.3 s-1 in the frontal white matter. According to analysis of statistical power, in all brain regions except one, group differences of 0.3-0.5 s-1 in the AXR can be inferred using 5 to 10 subjects per group. An AXR difference of this magnitude was observed between meningiomas (0.6 ± 0.1 s-1 ) and astrocytomas (1.0 ± 0.3 s-1 ).CONCLUSIONS: With the optimized protocol, FEXI has the ability to infer relevant differences in the AXR between two populations for small group sizes. Magn Reson Med 77:1104-1114, 2017.
  •  
25.
  • Lampinen, Björn, et al. (författare)
  • Probing brain tissue microstructure with MRI: principles, challenges, and the role of multidimensional diffusion-relaxation encoding.
  • 2023
  • Ingår i: NeuroImage. - 1095-9572. ; 282
  • Tidskriftsartikel (refereegranskat)abstract
    • Diffusion MRI uses the random displacement of water molecules to sensitize the signal to brain microstructure and to properties such as the density and shape of cells. Microstructure modeling techniques aim to estimate these properties from acquired data by separating the signal between virtual tissue 'compartments' such as the intra-neurite and the extra-cellular space. A key challenge is that the diffusion MRI signal is relatively featureless compared with the complexity of brain tissue. Another challenge is that the tissue microstructure is wildly different within the gray and white matter of the brain. In this review, we use results from multidimensional diffusion encoding techniques to discuss these challenges and their tentative solutions. Multidimensional encoding increases the information content of the data by varying not only the b-value and the encoding direction but also additional experimental parameters such as the shape of the b-tensor and the echo time. Three main insights have emerged from such encoding. First, multidimensional data contradict common model assumptions on diffusion and T2 relaxation, and illustrates how the use of these assumptions cause erroneous interpretations in both healthy brain and pathology. Second, many model assumptions can be dispensed with if data are acquired with multidimensional encoding. The necessary data can be easily acquired in vivo using protocols optimized to minimize Cramér-Rao lower bounds. Third, microscopic diffusion anisotropy reflects the presence of axons but not dendrites. This insight stands in contrast to current 'neurite models' of brain tissue, which assume that axons in white matter and dendrites in gray matter feature highly similar diffusion. Nevertheless, as an axon-based contrast, microscopic anisotropy can differentiate gray and white matter when myelin alterations confound conventional MRI contrasts.
  •  
26.
  • Lampinen, Björn, et al. (författare)
  • Time dependence in diffusion MRI predicts tissue outcome in ischemic stroke patients
  • 2021
  • Ingår i: Magnetic Resonance in Medicine. - : Wiley. - 0740-3194 .- 1522-2594. ; 86:2, s. 754-764
  • Tidskriftsartikel (refereegranskat)abstract
    • Purpose: Reperfusion therapy enables effective treatment of ischemic stroke presenting within 4–6 hours. However, tissue progression from ischemia to infarction is variable, and some patients benefit from treatment up until 24 hours. Improved imaging techniques are needed to identify these patients. Here, it was hypothesized that time dependence in diffusion MRI may predict tissue outcome in ischemic stroke. Methods: Diffusion MRI data were acquired with multiple diffusion times in five non-reperfused patients at 2, 9, and 100 days after stroke onset. Maps of “rate of kurtosis change” (k), mean kurtosis, ADC, and fractional anisotropy were derived. The ADC maps defined lesions, normal-appearing tissue, and the lesion tissue that would either be infarcted or remain viable by day 100. Diffusion parameters were compared (1) between lesions and normal-appearing tissue, and (2) between lesion tissue that would be infarcted or remain viable. Results: Positive values of k were observed within stroke lesions on day 2 (P =.001) and on day 9 (P =.023), indicating diffusional exchange. On day 100, high ADC values indicated infarction of 50 ± 20% of the lesion volumes. Tissue infarction was predicted by high k values both on day 2 (P =.026) and on day 9 (P =.046), by low mean kurtosis values on day 2 (P =.043), and by low fractional anisotropy values on day 9 (P =.029), but not by low ADC values. Conclusions: Diffusion time dependence predicted tissue outcome in ischemic stroke more accurately than the ADC, and may be useful for predicting reperfusion benefit.
  •  
27.
  • Larsson, Elna-Marie, et al. (författare)
  • MRI with diffusion tensor imaging post-mortem at 3.0 T in a patient with frontotemporal dementia.
  • 2004
  • Ingår i: Dementia and Geriatric Cognitive Disorders. - : S. Karger AG. - 1420-8008 .- 1421-9824. ; 17:4, s. 316-319
  • Tidskriftsartikel (refereegranskat)abstract
    • The formalin-fixed brain of a patient with clinically diagnosed frontotemporal dementia (FTD) was examined post-mortem using magnetic resonance imaging (MRI) with diffusion tensor imaging (DTI) at 3.0 T. Frontotemporal atrophy as well as bilateral frontal white matter abnormalities were seen. The white matter changes were slightly more extensive on DTI than on conventional MRI. Correlation with histopathology of the corresponding regions revealed typical frontal lobe degeneration of non-Alzheimer type, with mild frontotemporal degeneration in the outer cortical layers and a moderate frontal white matter gliosis with demyelination. Post-mortem MRI/DTI with histopathologic correlation will enhance our understanding of the basis of white matter changes observed in dementia patients and may improve the in vivo MRI/DTI diagnostic assessment in FTD.
  •  
28.
  • Lasic, Samo, et al. (författare)
  • Apparent exchange rate mapping with diffusion MRI.
  • 2011
  • Ingår i: Magnetic Resonance in Medicine. - : Wiley. - 1522-2594 .- 0740-3194. ; 66, s. 356-365
  • Tidskriftsartikel (refereegranskat)abstract
    • Water exchange through the cell membranes is an important feature of cells and tissues. The rate of exchange is determined by factors such as membrane lipid composition and organization, as well as the type and activity of aquaporins. A method for noninvasively estimating the rate of water exchange would be useful for characterizing pathological conditions, e.g., tumors, multiple sclerosis, and ischemic stroke, expected to be associated with a change of the membrane barrier properties. This study describes the filter exchange imaging method for determining the rate of water exchange between sites having different apparent diffusion coefficients. The method is based on the filter-exchange pulsed gradient spin-echo NMR spectroscopy experiment, which is here modified to be compatible with the constraints of clinical MR scanners. The data is analyzed using a model-free approach yielding maps of the apparent exchange rate, here being introduced in analogy with the concept of the apparent diffusion coefficient. Proof-of-principle experiments are performed on microimaging and whole-body clinical scanners using yeast suspension phantoms. The limitations and appropriate experimental conditions are examined. The results demonstrate that filter exchange imaging is a fast and reliable method for characterizing exchange, and that it has the potential to become a powerful diagnostic tool. Magn Reson Med, 2011. © 2011 Wiley-Liss, Inc.
  •  
29.
  • LI, WEN, et al. (författare)
  • Extensive graft-derived dopaminergic innervation is maintained 24 years after transplantation in the degenerating parkinsonian brain.
  • 2016
  • Ingår i: Proceedings of the National Academy of Sciences of the United States of America. - : Proceedings of the National Academy of Sciences. - 1091-6490. ; 113:23, s. 6544-6549
  • Tidskriftsartikel (refereegranskat)abstract
    • Clinical trials using cells derived from embryonic ventral mesencephalon have shown that transplanted dopaminergic neurons can survive and function in the long term, as demonstrated by in vivo brain imaging using 18F-fluorodopa and 11C-raclopride positron emission tomography. Here we report the postmortem analysis of a patient with Parkinson’s disease who 24 y earlier underwent unilateral transplantation of embryonic dopaminergic neurons in the putamen and subsequently exhibited major motor improvement and recovery of striatal dopaminergic function. Histopathological analysis showed that a dense, near-normal graft-derived dopaminergic reinnervation of the putamen can be maintained for a quarter of a century despite severe host brain pathology and with no evidence of immune response. In addition, ubiquitin- and α-synuclein–positive inclusions were seen, some with the appearance of typical Lewy bodies, in 11–12% of the grafted dopaminergic neurons, reflecting the spread of pathology from the host brain to the transplants. Because the clinical benefits induced by transplantation in this patient were gradually lost after 14 y posttransplantation, our findings provide the first reported evidence, to our knowledge, that even a viable dopaminergic graft giving rise to extensive striatal reinnervation may lose its efficacy if widespread degenerative changes develop in the host brain.
  •  
30.
  • Lätt, Jimmy, et al. (författare)
  • Accuracy of q-space related parameters in MRI: Simulations and phantom measurements
  • 2007
  • Ingår i: IEEE Transactions on Medical Imaging. - 1558-254X. ; 26:11, s. 1437-1447
  • Tidskriftsartikel (refereegranskat)abstract
    • The accuracy of q-space measurements was evaluated at a 3.0-T clinical magnetic resonance imaging (MRI) scanner, as compared with a 4.7-T nuclear magnetic resonance (NMR) spectrometer. Measurements were performed using a stimulated-echo pulse-sequence on n-decane as well as on polyethylene glycol (PEG) mixed with different concentrations of water, in order to obtain bi-exponential signal decay curves. The diffusion coefficients as well as the modelled diffusional kurtosis K-fit, were obtained from the signal decay curve, while the full-width at half-maximum (FWHM) and the diffusional kurtosis K were obtained from the displacement distribution. Simulations of restricted diffusion, under conditions similar to those obtainable with a clinical MRI scanner, were carried out assuming various degrees of violation of the short gradient pulse (SGP) condition and of the long diffusion time limit., The results indicated that an MRI system can not be used for quantification of structural sizes less than about 10 mu m by means of FWHM since the parameter underestimates the confinements due to violation of the SGP condition. However, FWHM can still be used as an important contrast parameter. The obtained kurtosis values were lower than expected from theory and the results showed that care must be taken when interpreting a kurtosis estimate deviating from zero.
  •  
31.
  • Lätt, Jimmy, et al. (författare)
  • Diffusion-weighted MRI measurements on stroke patients reveal water-exchange mechanisms in sub-acute ischaemic lesions.
  • 2009
  • Ingår i: NMR in Biomedicine. - : Wiley. - 0952-3480 .- 1099-1492. ; 22:6, s. 619-628
  • Tidskriftsartikel (refereegranskat)abstract
    • The aim of this study was to investigate the diffusion time dependence of signal-versus-b curves obtained from diffusion-weighted magnetic resonance imaging (DW-MRI) of sub-acute ischaemic lesions in stroke patients. In this case series study, 16 patients with sub-acute ischaemic stroke were examined with DW-MRI using two different diffusion times (60 and 260 ms). Nine of these patients showed sufficiently large lesions without artefacts to merit further analysis. The signal-versus-b curves from the lesions were plotted and analysed using a two-compartment model including compartmental exchange. To validate the model and to aid the interpretation of the estimated model parameters, Monte Carlo simulations were performed. In eight cases, the plotted signal-versus-b curves, obtained from the lesions, showed a signal-curve split-up when data for the two diffusion times were compared, revealing effects of compartmental water exchange. For one of the patients, parametric maps were generated based on the extracted model parameters. These novel observations suggest that water exchange between different water pools is measurable and thus potentially useful for clinical assessment. The information can improve the understanding of the relationship between the DW-MRI signal intensity and the microstructural properties of the lesions. Copyright (c) 2009 John Wiley & Sons, Ltd.
  •  
32.
  • Lätt, Jimmy, et al. (författare)
  • Effects of restricted diffusion in a biological phantom: a q-space diffusion MRI study of asparagus stems at a 3T clinical scanner
  • 2007
  • Ingår i: Magma. - : Springer Science and Business Media LLC. - 1352-8661. ; 20:4, s. 213-222
  • Tidskriftsartikel (refereegranskat)abstract
    • Introduction The aim of this work was to study the effects of restricted diffusion in a biological phantom consisting of green asparagus stems using q-space MRI at a clinical scanner. Method Measurements of the full width at half maximum (FWHM) of the displacement distribution were performed with varied diffusion time (T d). The accuracy of the measurements was investigated with respect to the degree of violation of the short gradient pulse (SGP) condition, partial volume effects and a FWHM-based tensor model. Results The measurements showed a reasonably constant FWHM perpendicular to the capillaries in the vascular bundles and an increased FWHM parallel with the bundles when the T d was increased. A 15% decrease in FWHM perpendicular to the bundles was observed when the diffusion encoding duration was prolonged from 24 to 74 ms, owing to the violation of the SGP condition. For a population of different confinement sizes, simulations indicated that the FWHM reflects the smaller sizes rather then the mean size of the confinements. Conclusion A new method allowing tensor analysis of FWHM was derived and yielded accurate results. In conclusion, we found it possible to measure the effects of restricted diffusion with q-space MRI using a clinical MRI scanner.
  •  
33.
  • Lätt, Jimmy, et al. (författare)
  • In vivo visualization of displacement-distribution-derived parameters in q-space imaging.
  • 2008
  • Ingår i: Magnetic Resonance Imaging. - : Elsevier BV. - 1873-5894 .- 0730-725X. ; 26:1, s. 77-87
  • Tidskriftsartikel (refereegranskat)abstract
    • Objective This study aimed to explore the potential of in vivo q-space imaging in the differentiation between different cerebral water components. Materials and Methods Diffusion-weighted imaging was performed in six directions with 32 equally spaced q values and a maximum b value of 6600 s/mm2. The shape of the signal-attenuation curve and the displacement propagator were examined and compared with a normal distribution using the kurtosis parameter. Maps displaying kurtosis, fast and slow components of the apparent diffusion coefficients, fractional anisotropy and directional diffusion were calculated. The displacement propagator was further described by the full width at half and at tenth maximum and by the probability density of zero displacement P(0). Three healthy volunteers and three patients with previously diagnosed multiple sclerosis (MS) were examined. Results Simulations indicated that the kurtosis of a signal-attenuation curve can determine if more than one water component is present and that care must be taken to select an appropriate threshold. It was possible to distinguish MS plaques in both signal and diffusional kurtosis maps, and in one patient, plaques of different degree of demyelinization showed different behavior. Discussion Our results indicate that in vivo q-space analysis is a potential tool for the assessment of different cerebral water components, and it might extend the diagnostic interpretation of data from diffusion magnetic resonance imaging.
  •  
34.
  • Lätt, Jimmy (författare)
  • Investigation of Water Mobility using Diffusion-Sensitive MRI: The Role of q-Space Imaging, High b-Values and Diffusion Time
  • 2008
  • Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
    • Nuclear magnetic resonance (NMR) diffusometry provides important information about molecular motion on a microscopic scale. The advantage of NMR diffusometry is its ability to characterise microstructures non-invasively. This has made the method important not only in chemistry, biochemistry and materials science, but also in medicine. Diffusion-weighted magnetic resonance imaging (DW-MRI) has been used for about 20 years at specialised radiology departments worldwide. One of the most important clinical features of DW-MRI is its ability to reveal ischaemic lesions within minutes of the onset of an infarct. Surprisingly, the mechanism behind the observed image contrast has not yet been completely explained. As the performance of clinical MRI scanner hardware improves, methods originally developed for experimental NMR spectrometers can be applied to studies of human tissue in vivo. This will benefit patients by improving the diagnostic capability of MRI. The aim of the studies described in this doctoral thesis was to use DW-MRI measurements to develop and evaluate methods for studies of the microstructural environment of diffusing water molecules in vivo. The experiments were primarily performed using a 3T clinical head scanner, but additional phantom measurements were carried out using an NMR spectrometer. In one of the studies, multiple sclerosis (MS) patients were examined and q-space-related parameters were evaluated with respect to image contrast. A closer examination of the limitations of the q-space method using both phantom measurements and extensive Monte Carlo simulations was performed in an additional project. The knowledge obtained was applied to investigations of a biological phantom in which compartments sizes restricting the diffusion of water were quantified using a clinical scanner. Based on the understanding gained from the simulations and phantom measurements, a slightly different approach, based on the use of different diffusion times, was used in a volunteer study to investigate the possible effects of restricted diffusion in nerve tissue in vivo. This approach was pursued in a preliminary study of patients with ischaemic lesions, and the results revealed water exchange between different water pools within the lesions.
  •  
35.
  • Lätt, Jimmy, et al. (författare)
  • Regional values of diffusional kurtosis estimates in the healthy brain.
  • 2013
  • Ingår i: Journal of Magnetic Resonance Imaging. - : Wiley. - 1522-2586 .- 1053-1807. ; 37:3, s. 610-618
  • 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.
  •  
36.
  •  
37.
  • Madru, Renata, et al. (författare)
  • 99mTc-Labeled Superparamagnetic Iron Oxide Nanoparticles for Multimodality SPECT/MRI of Sentinel Lymph Nodes.
  • 2012
  • Ingår i: Journal of Nuclear Medicine. - : Society of Nuclear Medicine. - 0161-5505 .- 2159-662X. ; 53:3, s. 459-463
  • Tidskriftsartikel (refereegranskat)abstract
    • The purpose of this study was to develop multimodality SPECT/MRI contrast agents for sentinel lymph node (SLN) mapping in vivo. METHODS: Nanoparticles with a solid iron oxide core and a polyethylene glycol coating were labeled with (99m)Tc. The labeling efficiency was determined with instant thin-layer chromatography and magnetic separation. The stability of the radiolabeled superparamagnetic iron oxide nanoparticles (SPIONs) was verified in both sterile water and human serum at room temperature 6 and 24 h after labeling. Five Wistar rats were injected subcutaneously in the right hind paw with (99m)Tc-SPIONs (25-50 MBq, ∼0.2 mg of Fe) and sacrificed 4 h after injection. Two animals were imaged with SPECT/MRI. All 5 rats were dissected; the lymph nodes, liver, kidneys, spleen, and hind paw containing the injection site were removed and weighed; and activity in the samples was measured. The microdistribution within the lymph nodes was studied with digital autoradiography. RESULTS: The efficiency of labeling of the SPIONs was 99% 6 h after labeling in both water and human serum. The labeling yield was 98% in water and 97% in human serum 24 h after labeling. The SLN could be identified in vivo with SPECT/MRI. The accumulation of (99m)Tc-SPIONs (as the percentage injected dose/g [%ID/g]) in the SLN was 100 %ID/g, whereas in the liver and spleen it was less than 2 %ID/g. Digital autoradiography images revealed a nonhomogeneous distribution of (99m)Tc-SPIONs within the lymph nodes; nanoparticles were found in the cortical, subcapsular, and medullary sinuses. CONCLUSION: This study revealed the feasibility of labeling SPIONs with (99m)Tc. The accumulation of (99m)Tc-SPIONs in lymph nodes after subcutaneous injection in animals, verified by SPECT/MRI, is encouraging for applications in breast cancer and malignant melanoma.
  •  
38.
  • Mellander, Helena, et al. (författare)
  • Metal artifact reduction by virtual monoenergetic reconstructions from spectral brain CT
  • 2023
  • Ingår i: European Journal of Radiology Open. - : Elsevier BV. - 2352-0477. ; 10, s. 1-6
  • Tidskriftsartikel (refereegranskat)abstract
    • PURPOSE: Conventional computed tomography (CT) images are severely affected by metal artifacts in patients with intracranial coils. Monoenergetic images have been suggested to reduce metal artifacts.The aim of this study was to assess metal artifacts in virtual monoenergetic images (VMIs) reconstructed from spectral brain CT.METHODS: Thirty-two consecutive patients with intracranial coils examined by spectral non contrast brain CT (NCCT) at our center between November 2017 and April 2019 were included. Attenuation and standard deviations were measured in regions of interest (ROIs) at predefined areas in artifact-free and artifact-affected areas. Measurements were performed in conventional polyenergetic images (CIs) and the corresponding data for VMIs were retrieved through spectral diagrams for the each ROI. Subjective analysis was performed by visual grading of CIs and specific VMIs by two neuroradiologists, independently.RESULTS: In artefact-affected image areas distal from the metal objects, the attenuation values decreased with higher energy level VMIs. The same effect was not seen for artefact-affected image areas close to the metal.Subjective rating of the artefact severity was significantly better in VMIs at 50 keV for one of the two reviewers compared to the CIs. Overall image quality and tissue differentiation scores were significantly higher for both reviewers in VMIs at 60 and 70 keV compared to CIs.CONCLUSION: Our quantitative and qualitative image analysis shown that there is a small significant reduction of intracranial coils artifacts severity by all monoenergetic reconstructions from 50 to 200 keV with preserved or increased overall subjective image quality compared to conventional images.
  •  
39.
  • Mellander, Helena, et al. (författare)
  • Virtual monoenergetic images by spectral detector computed tomography may improve image quality and diagnostic ability for ischemic lesions in acute ischemic stroke
  • 2023
  • Ingår i: Acta Radiologica. - : SAGE Publications. - 0284-1851 .- 1600-0455. ; 64:4, s. 1631-1640
  • Tidskriftsartikel (refereegranskat)abstract
    • Background: Acute ischemic lesions are challenging to detect by conventional computed tomography (CT). Virtual monoenergetic images may improve detection rates by increased tissue contrast. Purpose: To compare the ability to detect ischemic lesions of virtual monoenergetic with conventional images in patients with acute stroke. Material and Methods: We included consecutive patients at our center that underwent brain CT in a spectral scanner for suspicion of acute stroke, onset <12 h, with or without (negative controls) a confirmed cortical ischemic lesion in the initial scan or a follow-up CT or magnetic resonance imaging. Attenuation was measured in predefined areas in ischemic gray (guided by follow-up exams), normal gray, and white matter in conventional images and retrieved in spectral diagrams for the same locations in monoenergetic series at 40–200 keV. Signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR) were calculated. Visual assessment of diagnostic measures was performed by independent review by two neuroradiologists blinded to reconstruction details. Results: In total, 29 patients were included (January 2018 to July 2019). SNR was higher in virtual monoenergetic compared to conventional images, significantly at 60–150 keV. CNR between ischemic gray and normal white matter was higher in monoenergetic images at 40–70 keV compared to conventional images. Virtual monoenergetic images received higher scores in overall image quality. The sensitivity for diagnosing acute ischemia was 93% and 97%, respectively, for the reviewers, compared to 55% of the original report based on conventional images. Conclusion: Virtual monoenergetic reconstructions of spectral CIs may improve image quality and diagnostic ability in stroke assessment.
  •  
40.
  • Morsing, Eva, et al. (författare)
  • Brain volumes and developmental outcome in childhood following fetal growth restriction leading to very preterm birth
  • 2018
  • Ingår i: Frontiers in Physiology. - : Frontiers Media SA. - 1664-042X. ; 9:NOV
  • Tidskriftsartikel (refereegranskat)abstract
    • Background: Children born very preterm (PT) after fetal growth restriction (FGR) exhibit cognitive impairment at early school age. The relationship between neurodevelopmental impairment and attained regional brain volumes is unknown. Methods: We studied 23 preterm children with FGR (PT-FGR), 24 matched preterm children AGA (PT-AGA), and 27 matched term AGA children (T-AGA) by measuring brain volumes with magnetic resonance imaging at early school age. Cognitive and motor functions were assessed by the Wechsler Intelligence Scales for Children and the ABC-Movement score. Results: The mean (SD) full-scale IQ was 80 (17) in the PT-FGR group and 103 (12) in the PT-AGA group (p < 0.001). The PT-FGR group had lower mean total, gray matter, white matter, thalamic, cerebellar white matter, and hippocampal volumes as compared to the T-AGA group (p = 0.01, 0.04, 0.003, 0.002, 0.001, and 0.009, respectively). Brain volumes did not differ significantly between the PT groups. Reduction of hippocampal volume correlated with degree of growth restriction at birth (r = 0.46, p = 0.05). Neither the full-scale IQ nor the ABC movement score <5th percentile were related to brain volumes. Conclusion: Brain volumes as determined by MRI at early school age were primarily associated with degree of prematurity at birth and less with FGR. Regional brain volumes did not discriminate cognitive and motor function beyond that predicted by gestational age at birth.
  •  
41.
  • Mårtensson, Johanna (författare)
  • Diffusion tensor magnetic resonance imaging of the brain : Tractography analysis with application in healthy individuals and patients
  • 2017
  • Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
    • In study 1, thirty-eight healthy controls were used for optimization of the method. Fifteen patients with progressive supranuclear palsy and an equal number of age-matched healthy controls underwent diffusion tensor MRI and were then investigated and compared groupwise.It was shown that tractography analyses may preferably be performed regionally, such as along the tracts or in different segments of the tracts. Normalization of white matter tracts can be performed using anatomical landmarks.In study 2, 104 males and 153 females in the age interval 13 to 84 years of age participated as healthy individuals in order to investigate age-related changes with diffusion tensor MRI.It was shown that spatially differences in age-related changes exist between subdivided segments within white matter tracts. The aging processes within the CB and the IFO vary regionally.In study 3, 38 human brains were used for investigation of the white matter tract inferior longitudinal fasciculus (ILF) and its subcomponents. Of these, white matter anatomical dissection was performed in 14 post-mortem normal human brains. The remaining 24 brains were investigated in vivo with diffusion tensor MRI in healthy individuals.It was validated that fibers of the ILF in the occipito-temporal region have a clear, constant and detailed organisation. The anatomical connectivity pattern, and quantitative differences between the ILF subcomponents, confirmed a pivotal role of the ILF.In study 4, 12 patients with iNPH were included in the study and examined with diffusion tensor at three time points. For comparison, 12 healthy controls, matched by gender and age were also included. Controls were examined with MRI only once.It was shown that DTI measures differ significantly between patients with iNPH and healthy controls. DTI measures of the CC, the CST and the SLF, correlated to changes in clinical symptoms after shunt surgery.Deeper knowledge about functions of the brain increases possibilities to take advantages from DTI analyses with tractography. 
  •  
42.
  •  
43.
  • Mårtensson, Johanna, et al. (författare)
  • Spatial analysis of diffusion tensor tractography statistics along the inferior fronto-occipital fasciculus with application in progressive supranuclear palsy
  • 2013
  • Ingår i: Magnetic Resonance Materials in Physics, Biology and Medicine. - : Springer Science and Business Media LLC. - 0968-5243 .- 1352-8661. ; 26:6, s. 527-537
  • Tidskriftsartikel (refereegranskat)abstract
    • The purpose of the study was to develop a method for analysis of diffusion parameters along white matter (WM) tracts, using spatial normalization based on anatomical landmarks, and to introduce the apparent area coefficient (AAC). The method's applicability was tested in the inferior fronto-occipital fasciculus (IFO) in patients with progressive supranuclear palsy (PSP) and healthy controls (HCs). A framework for analysis of diffusion parameters was developed. Spatial normalization of the tracts was performed using anatomical landmarks, to avoid deformations caused by cerebral atrophy. Initially, 38 HCs were used to optimize a threshold for the minimal size of regions that differ between groups. The fractional anisotropy, mean diffusivity, AAC, and the hemispheric asymmetry index (AI), were compared between 11 PSP patients and 15 HCs. The method was feasible for analysis of PSP patients and HCs. The AI showed that the observed hemispheric asymmetry of AAC was significantly larger in PSP patients compared with HCs in small regions of the IFO. The method was successfully employed for analysis of diffusion parameters along the IFO in a patient group. This method can be potentially useful in studies of WM diseases, with or without cerebral atrophy.
  •  
44.
  • Mårtensson, Johan, et al. (författare)
  • Structural changes on mri demonstrate specific cerebellar involvement in sle patients—a vbm study
  • 2021
  • Ingår i: Brain Sciences. - : MDPI AG. - 2076-3425. ; 11:4
  • Tidskriftsartikel (refereegranskat)abstract
    • The purpose of this study is to investigate possible differences in brain structure, as measured by T1-weighted MRI, between patients with systemic lupus erythematosus (SLE) and healthy controls (HC), and whether any observed differences were in turn more severe in SLE patients with neuropsychiatric manifestations (NPSLE) than those without (non-NPSLE). Structural T1weighted MRI was performed on 69 female SLE patients (mean age = 35.8 years, range = 18–51 years) and 24 age-matched female HC (mean age = 36.8 years, range = 23–52 years) in conjunction with neuropsychological assessment using the CNS Vital Signs test battery. T1-weighted images were preprocessed and analyzed by FSL-VBM. The results show that SLE patients had lower grey matter probability values than the control group in the VIIIa of the cerebellum bilaterally, a region that has previously been implied in sensorimotor processing in human and non-human primates. No structural differences for this region were found between NPSLE and non-NPSLE patients. VBM values from the VIIIa region showed a weak positive correlation with the psychomotor speed domain from CNS Vital Signs (p = 0.05, r = 0.21), which is in line with its presumed role as a sensorimotor processing area.
  •  
45.
  • Nilsson, Markus, et al. (författare)
  • Evaluating the accuracy and precision of a two-compartment Kärger model using Monte Carlo simulations.
  • 2010
  • Ingår i: Journal of Magnetic Resonance. - : Elsevier BV. - 1096-0856 .- 1090-7807. ; 206:1, s. 59-67
  • Tidskriftsartikel (refereegranskat)abstract
    • Specific parameters of the neuronal tissue microstructure, such as axonal diameters, membrane permeability and intracellular water fractions are assessable using diffusion MRI. These parameters are commonly estimated using analytical models, which may introduce bias in the estimated parameters due to the approximations made when deriving the models. As an alternative to using analytical models, a database of signal curves generated by fast Monte Carlo simulations can be employed. Simulated diffusion MRI measurements were generated and evaluated using the two-compartment Kärger model as well as the simulation model based on a database containing signal curves from approximately 60000 simulations performed with different combinations of microstructural parameters. A protocol based on a pulsed gradient spin echo sequence with diffusion times of 30 and 60ms and with gradient amplitudes obtainable with a clinical MRI scanner was employed for the investigations. When using the analytical model, a major negative bias (up to approximately 25%) in the estimated intracellular volume fraction was observed for short exchange times, while almost no bias was seen for the simulation model. In general, the simulation model improved the accuracy of the estimated parameters as compared to the analytical model, except for the exchange time parameter.
  •  
46.
  • Nilsson, Markus, et al. (författare)
  • Noninvasive mapping of water diffusional exchange in the human brain using filter-exchange imaging.
  • 2013
  • Ingår i: Magnetic Resonance in Medicine. - : Wiley. - 1522-2594 .- 0740-3194. ; 69:6, s. 1572-1580
  • Tidskriftsartikel (refereegranskat)abstract
    • We present the first in vivo application of the filter-exchange imaging protocol for diffusion MRI. The protocol allows noninvasive mapping of the rate of water exchange between microenvironments with different self-diffusivities, such as the intracellular and extracellular spaces in tissue. Since diffusional water exchange across the cell membrane is a fundamental process in human physiology and pathophysiology, clinically feasible and noninvasive imaging of the water exchange rate would offer new means to diagnose disease and monitor treatment response in conditions such as cancer and edema. The in vivo use of filter-exchange imaging was demonstrated by studying the brain of five healthy volunteers and one intracranial tumor (meningioma). Apparent exchange rates in white matter range from 0.8 ± 0.08 s(-1) in the internal capsule, to 1.6 ± 0.11 s(-1) for frontal white matter, indicating that low values are associated with high myelination. Solid tumor displayed values of up to 2.9 ± 0.8 s(-1) . In white matter, the apparent exchange rate values suggest intra-axonal exchange times in the order of seconds, confirming the slow exchange assumption in the analysis of diffusion MRI data. We propose that filter-exchange imaging could be used clinically to map the water exchange rate in pathologies. Filter-exchange imaging may also be valuable for evaluating novel therapies targeting the function of aquaporins. Magn Reson Med, 2012. © 2012 Wiley Periodicals, Inc.
  •  
47.
  • Nilsson, Markus, et al. (författare)
  • On the effects of a varied diffusion time in vivo: is the diffusion in white matter restricted?
  • 2009
  • Ingår i: Magnetic Resonance Imaging. - : Elsevier BV. - 1873-5894 .- 0730-725X. ; 27:2008 Jul 25, s. 176-187
  • Tidskriftsartikel (refereegranskat)abstract
    • The aim of this work was to study the diffusion-related signal attenuation curves (signal-vs.-b curves) measured perpendicular and parallel to the neuronal fibers of the corticospinal tract in vivo and to determine whether effects of restricted diffusion could be observed when varying the diffusion time (T(D)). A biexponential model and a two-compartment model including exchange according to the Kärger formalism were employed to analyze the signal-vs.-b curves. To validate the two-compartment model, restricted diffusion with exchange was simulated for uniformly sized cylinders, using different diameters and exchange times. The model was shown to retrieve the simulated parameters well, also when the short gradient pulse approximation was not met. The in vivo measurements performed perpendicular to the tracts, using b values up to 28000 s/mm(2) and T(D) values between 64 and 256 ms, did not show the effects of restricted diffusion as expected from previous ex vivo studies. The applied two-compartment model yielded an average axonal diameter of about 4 mum and an intracellular exchange time of about 300 ms, but did not fit statistically well to the data. In conclusion, this study indicates that if the diffusion is modeled as two compartments, of which one is restricted, exchange must be included in the model.
  •  
48.
  • Nilsson, Markus, et al. (författare)
  • The importance of axonal undulation in diffusion MR measurements: a Monte Carlo simulation study.
  • 2012
  • Ingår i: NMR in Biomedicine. - : Wiley. - 0952-3480. ; 25, s. 795-805
  • Tidskriftsartikel (refereegranskat)abstract
    • Many axons follow wave-like undulating courses. This is a general feature of extracranial nerve segments, but is also found in some intracranial nervous tissue. The importance of axonal undulation has previously been considered, for example, in the context of biomechanics, where it has been shown that posture affects undulation properties. However, the importance of axonal undulation in the context of diffusion MR measurements has not been investigated. Using an analytical model and Monte Carlo simulations of water diffusion, this study compared undulating and straight axons in terms of diffusion propagators, diffusion-weighted signal intensities and parameters derived from diffusion tensor imaging, such as the mean diffusivity (MD), the eigenvalues and the fractional anisotropy (FA). All parameters were strongly affected by the presence of undulation. The diffusivity perpendicular to the undulating axons increased with the undulation amplitude, thus resembling that of straight axons with larger diameters. Consequently, models assuming straight axons for the estimation of the axon diameter from diffusion MR measurements might overestimate the diameter if undulation is present. FA decreased from approximately 0.7 to 0.5 when axonal undulation was introduced into the simulation model structure. Our results indicate that axonal undulation may play a role in diffusion measurements when investigating, for example, the optic and sciatic nerves and the spinal cord. The simulations also demonstrate that the stretching or compression of neuronal tissue comprising undulating axons alters the observed water diffusivity, suggesting that posture may be of importance for the outcome of diffusion MRI measurements. Copyright © 2011 John Wiley & Sons, Ltd.
  •  
49.
  • Nilsson, Markus, et al. (författare)
  • The role of tissue microstructure and water exchange in biophysical modelling of diffusion in white matter.
  • 2013
  • Ingår i: Magma. - : Springer Science and Business Media LLC. - 1352-8661. ; 26:4, s. 345-370
  • Forskningsöversikt (refereegranskat)abstract
    • Biophysical models that describe the outcome of white matter diffusion MRI experiments have various degrees of complexity. While the simplest models assume equal-sized and parallel axons, more elaborate ones may include distributions of axon diameters and axonal orientation dispersions. These microstructural features can be inferred from diffusion-weighted signal attenuation curves by solving an inverse problem, validated in several Monte Carlo simulation studies. Model development has been paralleled by microscopy studies of the microstructure of excised and fixed nerves, confirming that axon diameter estimates from diffusion measurements agree with those from microscopy. However, results obtained in vivo are less conclusive. For example, the amount of slowly diffusing water is lower than expected, and the diffusion-encoded signal is apparently insensitive to diffusion time variations, contrary to what may be expected. Recent understandings of the resolution limit in diffusion MRI, the rate of water exchange, and the presence of microscopic axonal undulation and axonal orientation dispersions may, however, explain such apparent contradictions. Knowledge of the effects of biophysical mechanisms on water diffusion in tissue can be used to predict the outcome of diffusion tensor imaging (DTI) and of diffusion kurtosis imaging (DKI) studies. Alterations of DTI or DKI parameters found in studies of pathologies such as ischemic stroke can thus be compared with those predicted by modelling. Observations in agreement with the predictions strengthen the credibility of biophysical models; those in disagreement could provide clues of how to improve them. DKI is particularly suited for this purpose; it is performed using higher b-values than DTI, and thus carries more information about the tissue microstructure. The purpose of this review is to provide an update on the current understanding of how various properties of the tissue microstructure and the rate of water exchange between microenvironments are reflected in diffusion MRI measurements. We focus on the use of biophysical models for extracting tissue-specific parameters from data obtained with single PGSE sequences on clinical MRI scanners, but results obtained with animal MRI scanners are also considered. While modelling of white matter is the central theme, experiments on model systems that highlight important aspects of the biophysical models are also reviewed.
  •  
50.
  • Nystedt, Jessika, et al. (författare)
  • Altered white matter microstructure in lupus patients : A diffusion tensor imaging study
  • 2018
  • Ingår i: Arthritis Research and Therapy. - : Springer Science and Business Media LLC. - 1478-6354 .- 1478-6362. ; 20:1
  • Tidskriftsartikel (refereegranskat)abstract
    • Background: The purpose of this study was to investigate whether white matter microstructure is altered in patients suffering from systemic lupus erythematosus (SLE), and if so, whether such alterations differed between patients with and without neuropsychiatric symptoms. Methods: Structural MRI and diffusion tensor imaging (DTI) were performed in 64 female SLE patients (mean age 36.9 years, range 18.2-52.2 years) and 21 healthy controls (mean age 36.7 years, range 23.3-51.2 years) in conjunction with clinical examination, laboratory tests, cognitive evaluation, and self-assessment questionnaires. The patients were subgrouped according to the American College of Rheumatology Neuropsychiatric Systemic Lupus Erythematosus case definitions into non-neuropsychiatric SLE (nonNPSLE) and neuropsychiatric SLE (NPSLE). Results: Comparisons between the SLE group and healthy controls showed that the mean fractional anisotropy (FA) was significantly reduced in the right rostral cingulum (p=0.038), the mid-sagittal corpus callosum (CC) (p=0.050), and the forceps minor of the CC (p=0.015). The mean diffusivity (MD) was significantly increased in the left hippocampal cingulum (p=0.017). No significant differences in MD or FA values were identified between NPSLE and nonNPSLE patients. Disease duration among all SLE patients correlated significantly with reduced FA in the CC (p<0.05). No correlations were found between DTI parameters and white matter hyperintensities, SLE Disease Activity Index-2000, Systemic Lupus International Collaborating Clinical/ACR Organ Damage Index, or Montgomery Asberg Depression Rate Score Self-report. Conclusions: We found alterations of white matter microstructure in SLE patients that were related to disease duration and fatigue. Our results indicate that cerebral involvement in SLE is not isolated to the NPSLE subgroup.
  •  
Skapa referenser, mejla, bekava och länka
  • Resultat 1-50 av 78
Typ av publikation
tidskriftsartikel (64)
konferensbidrag (8)
annan publikation (3)
doktorsavhandling (2)
forskningsöversikt (1)
Typ av innehåll
refereegranskat (72)
övrigt vetenskapligt/konstnärligt (6)
Författare/redaktör
Lätt, Jimmy (77)
Nilsson, Markus (41)
van Westen, Danielle (36)
Ståhlberg, Freddy (22)
Sundgren, Pia C. (14)
Wirestam, Ronnie (14)
visa fler...
Brockstedt, Sara (14)
Larsson, Elna-Marie (12)
Hansson, Oskar (12)
Englund, Elisabet (10)
Lampinen, Björn (10)
Szczepankiewicz, Fil ... (8)
Sundgren, Pia (7)
Nilsson, Christer (7)
Knutsson, Linda (7)
Svärd, Daniel (7)
Bengzon, Johan (6)
Mårtensson, Johanna (6)
Lindberg, Olof (6)
Rydelius, Anna (6)
Erfurth, Eva Marie (5)
Björkman-Burtscher, ... (5)
Follin, Cecilia (5)
Minthon, Lennart (4)
Alafuzoff, Irina (4)
Helms, Gunther (4)
Björkman-Burtscher, ... (4)
Wasselius, Johan (4)
Widner, Håkan (4)
Engelholm, Silke (4)
Zetterling, Maria (4)
Hall, Sara (4)
Nägga, Katarina (4)
Falk Delgado, Anna (4)
Mannfolk, Peter (4)
Olsson, Hampus (4)
Bengtsson, Anders (3)
Jönsen, Andreas (3)
Topgaard, Daniel (3)
Stomrud, Erik (3)
Fahlström, Markus (3)
Petersén, Åsa (3)
Askaner, Krister (3)
Maly Sundgren, Pia (3)
Kinhult, Sara (3)
Olsrud, Johan (3)
Durmo, Faris (3)
Santillo, Alexander ... (3)
Sjöbeck, Martin (3)
Fjalldal, Sigridur (3)
visa färre...
Lärosäte
Lunds universitet (74)
Karolinska Institutet (9)
Uppsala universitet (8)
Göteborgs universitet (4)
Linköpings universitet (3)
Umeå universitet (1)
Språk
Engelska (78)
Forskningsämne (UKÄ/SCB)
Medicin och hälsovetenskap (73)
Naturvetenskap (11)
Teknik (5)

År

Kungliga biblioteket hanterar dina personuppgifter i enlighet med EU:s dataskyddsförordning (2018), GDPR. Läs mer om hur det funkar här.
Så här hanterar KB dina uppgifter vid användning av denna tjänst.

 
pil uppåt Stäng

Kopiera och spara länken för att återkomma till aktuell vy