Search PubMed⌕ Search

Biomedical subjects

Franz Fazekas

Publications and source records attributed to Franz Fazekas.

12 recordsLinked to original sources
PubMed2003

Progression of cerebral white matter lesions: 6-year results of the Austrian Stroke Prevention Study.

More than half of all elderly people have some degree of cerebral white matter lesions. However, the rate of progression of these lesions is uncertain. We aimed to assess the progression of lesions in community-dwelling volunteers aged 50-75 years without neuropsychiatric disease. We used MRI to grade and measure the total volume of white matter lesions in 296 volunteers at baseline, 3 years, and 6 years. 58 participants with no lesions and 123 with punctate abnormalities at baseline had a low tendency for lesion progression, whereas 14 participants with early confluent and nine with confluent lesions underwent median increases of 2.7 cm(3) (IQR 0.5-5.9) and 9.3 cm(3) (7.1-21.0), respectively, in lesion volume at 6 years. Lesion grade at baseline was the only significant predictor of lesion progression (p<0.0001). Punctate white matter lesions are not progressive and are thus benign, whereas early confluent and confluent white matter abnormalities are progressive, and thus malignant.

Aged↗
PubMed2003

Lower levels of N-acetylaspartate in multiple sclerosis patients with the apolipoprotein E epsilon4 allele.

BACKGROUND: In multiple sclerosis (MS), the epsilon4 allele of apolipoprotein E (APOE epsilon4) has been associated with more rapid clinical worsening and more severe tissue damage on magnetic resonance imaging. OBJECTIVE: To use proton magnetic resonance spectroscopy ((1)H-MRS) to further explore the biochemical changes in the brains of patients with MS associated with APOE epsilon4. DESIGN: A 2-year clinical and (1)H-MRS follow-up cohort study. SETTING: The MS outpatient clinic, Department of Neurology, and Magnetic Resonance Center of Karl-Franzens University. PATIENTS: We performed (1)H-MRS of the central portion of both hemispheres and APOE genotyping in 72 patients (52 women and 20 men; mean +/- SD age, 34.8 +/- 8.8 years) with clinically definite relapsing-remitting MS. Repeated studies were performed in 44 patients after a mean +/- SD interval of 34 +/- 9 months. MAIN OUTCOME MEASURE: Levels of N-acetylaspartate as measured by (1)H-MRS. RESULTS: Patients with MS and an epsilon4 allele (n = 19) had a significantly lower mean +/- SD N-acetylaspartate-creatine ratio than those without an epsilon4 allele (n = 53) (1.73 +/- 0.26 vs 1.89 +/- 0.24; P =.04) despite the absence of significant differences in age at onset, disease duration, Expanded Disability Status Scale score, and number of previous relapses between subgroups. During follow-up, the drop in the N-acetylaspartate-creatine ratio of epsilon4 carriers was also significantly larger (-0.31 vs -0.10; P =.01). This was paralleled by a higher number of relapses (mean +/- SD, 4.1 +/- 2.7 vs 1.7 +/- 1.6; P =.02) and a faster although nonsignificant progression of disability (mean +/- SD (Delta)Expanded Disability Status Scale score, 0.9 +/- 1.8 vs 0.3 +/- 1.1; P =.19). CONCLUSIONS: The APOE epsilon4 allele has a negative effect on the course of MS, and increasing axonal damage may be an important mechanism.

Adult↗
PubMed2003

Method for quantitative imaging of the macromolecular 1H fraction in tissues.

A new method was developed for mapping the relative density of the macromolecular protons involved in magnetization transfer (MT). This method employs a stimulated echo preparation scheme in order to modulate the phase distribution within a spin ensemble. This labeled spin ensemble is then used as an intrinsic indicator, which is diluted due to magnetization exchange with macromolecular protons. A pulse sequence is presented which compensates for longitudinal relaxation, allows observation of the dilution effect only, and provides for calculation of parameter maps using indicator dilution theory. Compared to other quantitative MT techniques, neither additional relaxation time measurements nor knowledge regarding the lineshape of the macromolecular proton pool are required. Moreover, the inherent low specific absorption rate and the low sensitivity for B(1) errors make this method favorable in a clinical setting. This sequence was used to measure the macromolecular proton density in cross-linked bovine serum albumin. Using a navigated echo planar readout, the sequence was also employed to visualize the macromolecular content of human brain in vivo.

Animals↗
PubMed2003

Inter-sequence and inter-imaging unit variability of diffusion tensor MR imaging histogram-derived metrics of the brain in healthy volunteers.

BACKGROUND AND PURPOSE: Diffusion tensor MR imaging has the potential to improve our ability to monitor several neurologic conditions. As a preliminary step to the assessment of the role of diffusion tensor MR imaging in the context of longitudinal and multicenter studies, we evaluated the effect of sequence-, imaging unit-, and imaging-reimaging-induced variations on diffusion tensor MR imaging quantities derived from histogram analysis of a large portion of the central brain of healthy volunteers. METHODS: Each of eight healthy volunteers underwent imaging on two MR imaging units using three different pulsed gradient spin-echo single shot echo-planar pulse sequences (each of them having a different diffusion gradient scheme). Four additional healthy participants underwent imaging twice on the same imaging unit to assess imaging-reimaging variability. RESULTS: For mean diffusivity histograms, the differences between inter-sequence and inter-imaging unit coefficients of variation were significant for all the considered quantities with P values ranging from.003 to <.001. Also, the inter-imaging unit coefficient of variation for average fractional anisotropy was significantly higher than the corresponding inter-sequence coefficient of variation (P =.002). In general, inter-sequence mean diffusivity histogram-derived metrics (coefficients of variation ranging from 1.72% to 5.56%) were more reproducible than were fractional anisotropy histogram-derived metrics (coefficients of variation ranging from 5.45% to 7.34%). Imaging-reimaging variability was found to fall in the range of inter-sequence coefficients of variation for all the considered quantities. CONCLUSION: This study shows that inter-sequence, imaging-reimaging, and inter-imaging unit variabilities of diffusion tensor MR imaging-derived measurements are relatively low, suggesting that diffusion tensor MR imaging might provide additional measures of outcome with which to assess the evolution of brain structural damage in large scale studies of various neurologic conditions.

Analysis of Variance↗
PubMed2002

The natural course of MRI white matter hyperintensities.

The rate and extent of progression of white matter hyperintensities (WMH) over time in elderly subjects is yet unclear. These abnormalities may represent an early form of subcortical vascular dementia. As to whether such changes could be used, as a surrogate marker for this subtype of vascular dementia remains to be determined. So far there exists only a very limited number of studies determining the rate, clinical predictors and cognitive consequences of WMH evolution. There is evidence that these changes do progress over time, however the results of the different studies cannot be compared due to methodological differences. The Austrian Stroke Prevention Study reported that 17.9% of normal individuals show progression over time. The only published quantitative data demonstrated an absolute increase of 1.1 cm(3) over an observational period of 4 years in healthy subjects. Diastolic blood pressure, early confluent or confluent WMH at baseline and genetic variants in the angiotensinogen gene are so far the only known predictors of WMH progression. The Austrian Stroke Prevention Study did not find an association between the evolution of WMH and cognitive functioning but the statistical power of this analysis was small and the relationship needs to be further explored.

Aged↗
PubMed2002

Diffusion-weighted imaging of the spinal cord: interleaved echo-planar imaging is superior to fast spin-echo.

PURPOSE: To compare and evaluate two novel diffusion-weighted sequences, based either on fast spin-echo (FSE) or interleaved echo-planar imaging (EPI) methods, as potential tools for investing spinal cord abnormalities. MATERIALS AND METHODS: Following recent improvements, both interleaved EPI (IEPI) and FSE techniques could be alternative approaches for rapid diffusion-weighted imaging (DWI). Therefore, a navigated diffusion-weighted multishot FSE sequence and a fat-suppressed navigated diffusion-weighted IEPI sequence with local shimming capabilities were tested. Both methods were compared in a consecutive series of five healthy volunteers and five patients with suspected intramedullary lesions. The sequences were graded qualitatively as either superior, inferior, or equal in quality, and also quantitatively by measuring the amount of ghosting artifacts in the background. Quantitative measurements of the diffusion coefficients within the spine were included. RESULTS: The overall image quality of IEPI was superior to FSE. Two out of five FSE scans were rated with poor image quality, whereas all IEPI scans were of sufficient quality. The ghosting levels ranged from approximately 3.3% to 6.2% for IEPI and from approximately 7.5% to 18.9% for FSE. Diffusion coefficients measured in healthy volunteers were similar for both IEPI and FSE, but showed higher fluctuations with the FSE technique. CONCLUSION: Despite potential advantages of FSE, the IEPI technique is preferable for DWI applications in the spinal cord.

Diffusion↗
PubMed2002

Diffusion tensor imaging using single-shot SENSE-EPI.

SENSitivity Encoding (SENSE) greatly enhances the quality of diffusion-weighted echo-planar imaging (EPI) by reducing blurring and off-resonance artifacts. Such improvement would also be desirable for diffusion tensor imaging (DTI), but measures derived from the diffusion tensor can be extremely sensitive to any kind of image distortion. Whether DTI is feasible in combination with SENSE has not yet been explored, and is the focus of this study. Using a SENSE-reduction factor of 2, DTI scans in eight healthy volunteers were carried out with regular- and high-resolution acquisition matrices. To further improve the stability of the SENSE reconstruction, a new coil-sensitivity estimation technique based on variational calculus and the principles of matrix regularization was applied. With SENSE, maps of the trace of the diffusion tensor and of fractional anisotropy (FA) had improved spatial resolution and less geometric distortion. Overall, the geometric distortions were substantially removed and a significant resolution enhancement was achieved with almost the same scan time as regular EPI. DTI was even possible without the use of quadrature body coil (QBC) reference scans. Geometry-factor-related noise enhancement was only discernible in maps generated with higher-resolution matrices. Error boundaries for residual fluctuations in SENSE reconstructions are discussed. Our results suggest that SENSE can be combined with DTI and may present an important adjunct for future neuroimaging applications of this technique.

Brain↗
PubMed2002

Image registration and subtraction to detect active T(2) lesions in MS: an interobserver study.

Serial MRI studies are used to analyse change in multiple sclerosis (MS) lesion volume in clinical trials. As such an evaluation is very time consuming and subject to quantification errors, one might assess only the change in number or size of lesions using subtracted images. The advantage of subtracted images is that both new and/or enlarging and resolving and/or shrinking lesions can be evaluated, resulting in a more precise volume change than a net volume change. We studied the interobserver agreement in the detection of active MS lesions using paired dual-echo T(2)-weighted spin-echo studies (3-mm slices) of 30 MS patients with a range of MS disease activity on MRI from treatment trials. Using an automatic matching algorithm based on mutual information, the follow-up scan was registered to baseline, after which subtracted images were obtained. After a training session with formulation of guidelines, six observers identified new, enlarging, resolving and shrinking lesions on subtracted images. Weighted kappa (kappa) values were calculated to assess interobserver agreement. Good agreement was found for new lesions (kappa 0.69 +/- 0.08), while moderate agreement was found for enlarging lesions (kappa 0.52 +/- 0.06). When new and enlarging lesions were combined, good agreement was found for "positive" activity (kappa 0.71 +/-0.06). The interobserver agreement was poor for resolving lesions (kappa 0.31 +/- 0.07), and moderate for shrinking lesions (kappa 0.53 +/- 0.08). In conclusion, the use of subtracted images in the visual detection of new T(2) lesions resulted in a good level of interobserver agreement for "positive" disease activity. Subtraction of registered images is a reliable, time efficient method to assess disease progression in MS.

Adult↗
PubMed2002

Evolution of white matter lesions.

A 3-year follow-up of 273 participants (mean age 60 years) of the Austrian Stroke Prevention Study provides first information on the rate, clinical predictors and cognitive consequences of MRI white matter lesions (WML) in elderly individuals without neuropsychiatric disease. Lesion progression was found in 17.9% of individuals over a time period of 3 years. Diastolic blood pressure and early confluent or confluent white matter hyperintensities at baseline were the only significant predictors of white matter hyperintensity progression. Genetic association studies in the setting of the Austrian Stroke Prevention Study provide first evidence for genetic susceptibility factors for progression of WML. We observed associations with the paraoxonase Leu-->Met 54 polymorphism and with the M235T polymorphism of the angiotensinogen gene. Lesion progression had no influence on the course of neuropsychologic test performance over the observational period, but the statistical power of this analysis was low.

Aged↗
PubMed2002

CT and MRI rating of white matter lesions.

Rating scales play an important role in the evaluation of computed tomography (CT) or magnetic resonance-detected white matter lesions (WML). Unfortunately, this type of visual semiquantitative assessment is not yet an optimal tool because commonly agreed concepts regarding its use are lacking. To generate a discussion platform for further improvement of CT and MRI rating, we will provide some basic definitions, summarize the advantages and disadvantages of scoring schemes and review current efforts towards the improvement of this tool. Future research will have to concentrate on deepening our understanding of the histopathologic substrates of WML and on strategies to document their progression.

Aged↗