| 1. |
- Börjesson, L., et al.
(författare)
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Comparison between fMRI and Wada test
- 2004
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Ingår i: Epilepsia. - : Wiley-Blackwell. - 0013-9580 .- 1528-1167. ; 45:Suppl. 3, s. 84-84
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Tidskriftsartikel (refereegranskat)abstract
- Purpose: Language lateralisation in patients with epilepsy is more often atypical compared to a normal population. The Wada procedure for testing language and memory has some shortcomings; it is invasive and there is always a risk that the patient becomes too sedated, leading to difficulties in performing the tests. fMR1have shown promising results, showing good correlation to the Wadaprocedure concerning language-lateralisation. The aim of this studywas to investigate if fMRI could be used to determine which hemisphere was language dominant and compare the fMR1 results with the Wada-tests with a focus on patients with a complicated lateralisation.Method: 4 subjects were tested and they had a heterogeneous (I left handed, I ambidexter and 2 right handed) lateralisation and one had a severe dyslexia. A standard Wada procedure was used and compared with a fMRl investigation using a language paradigm.Results: The patients studied showed different language lateralisation patterns (2 left hemisphere and 2 bilateral). In two patients the two tests were fully concordant, in the others the fMRI showed a more bilateral pattern.Conclusion: fMR1 adds valuable information in the pre-surgical investigation for patients with a complex language lateralisation.
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| 2. |
- Engström, Maria, et al.
(författare)
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Clinical fMRI of language function in aphasic patients: Reading paradigm successful, while word generation paradigm fails
- 2010
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Ingår i: Acta Radiologica. - : Informa Healthcare. - 0284-1851 .- 1600-0455. ; 51:6, s. 679-686
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Tidskriftsartikel (refereegranskat)abstract
- Background: In fMRI examinations, it is very important to select appropriate paradigms assessing the brain function of interest. In addition, the patients ability to perform the required cognitive tasks during fMRI must be taken into account. Purpose: To evaluate two language paradigms, word generation and sentence reading for their usefulness in examinations of aphasic patients and to make suggestions for improvements of clinical fMRI. Material and Methods: Five patients with aphasia after stroke or trauma sequelae were examined by fMRI. The patients language ability was screened by neurolinguistic tests and elementary pre-fMRI language tests. Results: The sentence-reading paradigm succeeded to elicit adequate language-related activation in perilesional areas whereas the word generation paradigm failed. These findings were consistent with results on the behavioral tests in that all patients showed very poor performance in phonemic fluency, but scored well above mean at a reading comprehension task. Conclusion: The sentence-reading paradigm is appropriate to assess language function in this patient group, while the word-generation paradigm seems to be inadequate. In addition, it is crucial to use elementary pre-fMRI language tests to guide the fMRI paradigm decision.
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| 3. |
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| 4. |
- Engström, Maria, 1958-, et al.
(författare)
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Paradigm design of sensory–motor and language tests in clinical fMRI
- 2004
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Ingår i: Neurophysiologie clinique. - : Elsevier BV. - 0987-7053 .- 1769-7131. ; 34:6, s. 267-277
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Tidskriftsartikel (refereegranskat)abstract
- Functional magnetic resonance imaging (fMRI) paradigms on sensory–motor and language functions are reviewed from a clinical user’s perspective. The objective was to identify special requirements regarding the design of fMRI paradigms for clinical applications. A wide range of methods for setting up fMRI examinations were found in the literature. It was concluded that there is a need for standardised procedures adapted for clinical settings. Sensory–motor activation patterns do not vary much at different hand motion tasks. Nevertheless it is one of the most important clinical tests. In contrast, the language system is much more complex. In several studies it has been observed that word production tasks are preferable in determination of language lateralisation. Broca’s area is activated by most tasks, whereas sentence processing and semantic decision also involve activation in temporoparietal and frontal areas. However, combined task analysis (CTA) of several different tasks has been found to be more robust and reliable for clinical fMRI compared to separate task analysis.
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| 5. |
- Engström, Maria, et al.
(författare)
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Projection screen or video goggles as stimulus modality in functional magnetic resonance imaging
- 2005
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Ingår i: Magnetic Resonance Imaging. - : Elsevier BV. - 0730-725X .- 1873-5894. ; 23:5, s. 695-699
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Tidskriftsartikel (refereegranskat)abstract
- The purpose of this study was to investigate the reliability of functional magnetic resonance imaging (fMRI) by using either a projection screen or video goggles as stimulus modality. A sequence of visual stimuli were presented to the same subject at different occasions. The sequence was optimized with a genetic algorithm. In five sessions the stimuli were presented using a projection screen viewed through a mirror in the head coil and in five sessions using video goggles. Failure to detect visual activation in the medial left hemisphere was observed in sessions using the projection screen as stimulus modality. Decreased thresholds for P values and cluster size resulted in activation outside the occipital lobe and did not significantly increase activated areas in this region. Results in this study indicate that presentation of fMRI tasks with visual routes is more reliable with direct input through video goggles than with the conventional use of projection screens. Failure to detect crucial visual areas has severe consequences for tumor surgery in the visual cortex. Inferior visual impression might also have negative consequences for cognitive tests with high demand on attention and perception.
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| 6. |
- Fornander, Lotta, et al.
(författare)
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Age- and time-dependent effects on functional outcome and cortical activation pattern in patients with median nerve injury: a functional magnetic resonance imaging study Clinical article
- 2010
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Ingår i: Journal of Neurosurgery. - : American Association of Neurological Surgeons. - 0022-3085 .- 1933-0693. ; 113:1, s. 122-128
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Tidskriftsartikel (refereegranskat)abstract
- Object. The authors conducted a study to determine age- and time-dependent effects on the functional outcome after median nerve injury and repair and how such effects are related to changes in the pattern of cortical activation in response to tactile stimulation of the injured hand. Methods. The authors studied 11 patients with complete unilateral median nerve injury at the wrist repaired with epineural suture. In addition, 8 patients who were reported on in a previous study were included in the statistical analysis. In the entire study cohort, the mean age at injury was 23.3 +/- 13.4 years (range 7-57 years) and the time after injury ranged from 1 to 11 years. Sensory perception was measured with the static 2-point discrimination test and monofilaments. Functional MR imaging was conducted during tactile stimulation (brush strokes) of Digits II-III and IV-V of both hands, respectively. Results. Tactile sensation was diminished in the median territory in all patients. The strongest predictor of 2-point discrimination was age at injury (p less than 0.0048), and when this was accounted for in the regression analysis, the other age- and time-dependent predictors had no effect. The activation ratios (injured/healthy hand) for Digit II-III and Digit IV-V stimulation were positively correlated (rho 0.59, p less than 0.011). The activation ratio for Digit II-III stimulation correlated weakly with time after injury (p less than 0.041). The activation ratio of Digits IV-V correlated weakly with both age at injury (p less than 0.048) and time after injury (p less than 0.033), but no predictor reached significance in the regression model. The mean ratio of ipsi- and contralateral hemisphere activation after stimulation of the injured hand was 0.55, which was not significantly different from the corresponding ratio of the healthy hand (0.66). Conclusions. Following a median nerve injury (1-11 years after injury) there may be an initial increase in the volume of the cortical representation, which subsequently declines during the restoration phase. These dynamic changes may involve both median and ulnar nerve cortical representation, because both showed negative correlation with time after injury. These findings are in agreement with animal studies showing that cortical plasticity is an important mechanism for functional recovery after peripheral nerve injury and repair.
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| 7. |
- Ragnehed, Mattias, 1976-
(författare)
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Application of fMRI in clinical situations
- 2006
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Since its discovery in the early 1990's functional MRI (fMRI) has become the most widely used technique for mapping of brain functions. Its non-invasiveness and the large number of MR-scanners have contributed to the popularity of fMRI. In recent years the interest in using fMRI as a clinical instrument has increased, primarily for pre-operative planning. The purpose of this work is to improve the applicability of fMRI to clinical situations.In order to attain the objectives the capacity of analysis methods for fMRI was evaluated, design of paradigms to suit patients was looked into and the effects of an anxiolytic was investigated.Especially when fMRI is used in the clinic it is crucial that the analysis method employed is sensitive and reliable. It was confirmed that the method developed by Friman et al. is a worthy competitor to other analysis methods. In general the abilities of patients are reduced compared with healthy volunteer subjects. Therefore one has to design the tasks and task instructions to be readily comprehensible. In addition it is not uncommon that patients are anxious before the examinations and the unfamiliar environment in the MR department. Some need a small dose of an anxiolytic to be able to undergo the examination. The effect of an anxiolytic on healthy volunteers was evaluated. No effects on the fMRI results was identified but the results were confounded by a large session effect.
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| 8. |
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| 9. |
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| 10. |
- Ragnehed, Mattias, 1976-
(författare)
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Functional Magnetic Resonance Imaging for Clinical Diagnosis : Exploring and Improving the Examination Chain
- 2009
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Functional Magnetic Resonance Imaging (fMRI) is a relatively new imaging technique, first reported in 1992, which enables mapping of brain functions with high spatial resolution. Functionally active areas are distinguished by a small signal increase mediated by changes in local blood oxygenation in response to neural activity. The ability to non-invasively map brain function and the large number of MRI scanners quickly made the method very popular, and fMRI have had a huge impact on the study of brain function, both in healthy and diseased subjects.The most common clinical application of fMRI is pre-surgical mapping of brain functions in order to optimise surgical interventions. The clinical fMRI examination procedure can be divided into four integrated parts: (1) patient preparation, (2) image acquisition, (3) image analysis and (4) clinical decision. In this thesis, important aspects of all parts of the fMRI examination procedure are explored with the aim to provide recommendations and methods for prosperous clinical usage of the technique.The most important results of the thesis were: (I) administration of low doses of diazepam to reduce anxiety did not invalidate fMRI mapping results of primary motor and language areas, (II) the choice of visual stimuli equipment can have severe impact on the mapping of visual areas, (III) three-dimensional fMRI imaging sequences did not perform better than two-dimensional imaging sequences, (IV) adaptive spatial filtering can improve the fMRI data analysis, (V) clinical decisions should not be based on activation results from a single statistical threshold.
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| 11. |
- Ragnehed, Mattias, 1976-, et al.
(författare)
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Influence of diazepam on clinically designed FMRI
- 2007
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Ingår i: The Journal of Neuropsychiatry and Clinical Neurosciences. - 0895-0172 .- 1545-7222. ; 19:2, s. 164-172
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Tidskriftsartikel (refereegranskat)abstract
- The authors investigated the effect of diazepam on clinically relevant measures from functional magnetic resonance imaging (fMRI) examinations. Twenty volunteers were scanned twice. Using a double-blind randomized study design, the volunteers received placebo on one occasion, and on the other, 5 mg of diazepam. Three functional tests were used: motor, word generation, and working memory. Images were analyzed individually for each subject and the number of activated voxels and the laterality index were calculated. No significant effects related to the drug were detected. In contrast, the motor and working memory tasks showed a significant decrease in the number of activated voxels between Sessions 1 and 2, independently of diazepam administration. These results indicate that diazepam may be administered for premedication prior to fMRI investigations.
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| 12. |
- Ragnehed, Mattias, et al.
(författare)
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Performance of canonical correlation analysis in language tests by functional MRI
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- In this paper a new method based on constraitwd canonical correlation analysis (CCA) for the analysis of fMRI data is evaluated. In particular the method benefits from a powerful way of choosing temporal basis functions in additiou to an adaptive spatial filtering scheme. A modified receiver operating characteristic (ROC) method was used to quantify the results and to compare it with traditionally used statistics in an objective way. The evaluation was performed using real fMRI data form a language test. It was shown that the CCA based method offers a significant gain in detection power.
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| 13. |
- Ragnehed, Mattias, et al.
(författare)
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Restricted Canonical Correlation Analysis in Functional MRI-Validation and a Novel Thresholding Technique
- 2009
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Ingår i: Journal of Magnetic Resonance Imaging. - : Wiley. - 1053-1807 .- 1522-2586. ; 29:1, s. 146-154
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Tidskriftsartikel (refereegranskat)abstract
- Purpose: To validate the performance of an analysis method for fMRI data based on restricted canonical correlation analysis (rCCA) and adaptive filtering, and to increase the usability of the method by introducing a new technique for significance estimation of rCCA maps.Materials and Methods: Activation data from a language task and also a resting state fMRI data were collected from eight volunteers. Data was analyzed using both the rCCA method and the General Linear Model (GLM). A modified Receiver Operating Characteristic (ROC) method was used to evaluate the performance of the different analysis methods. The area under a fraction of the ROC curve was used as a measure of performance. On resting state data the fraction of voxels above certain significance thresholds were used to evaluate the significance estimation method.Results: The rCCA method scored significantly higher on the area under the ROC curve than the GLM. The fraction of activated voxels determined by thresholding according to the introduced significance estimation technique showed good agreement with the thresholds selected.Conclusion: The rCCA method is an effective analysis tool for fMRI data and its usability is increased with the introduced significance estimation method.
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| 14. |
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| 15. |
- Ragnehed, Mattias, 1976-, et al.
(författare)
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Visual Grading of 2D and 3D fMRI compared to image based descriptive measures
- 2010
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Ingår i: European Radiology. - Berlin / Heidelberg : Springer. - 0938-7994 .- 1432-1084. ; 20:3, s. 714-724
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Tidskriftsartikel (refereegranskat)abstract
- A prerequisite for successful clinical use of functional Magnetic Resonance Imaging (fMRI) is the selection of an appropriate imaging sequence. In this paper, 2D and 3D fMRI sequences were compared using different image quality assessment methods. Descriptive image measures, such as activation volume and temporal signal-to-noise ratio (TSNR), were compared with results from Visual Grading Characteristics (VGC) analysis of the fMRI results. It was found that significant differences in activation volume and TSNR were not directly reflected by differences in VGC scores. The results suggest that better performance on descriptive image measures is not always an indicator of improved diagnostic quality of the fMRI results. In conclusion, in addition to descriptive image measures, it is important to include measures of diagnostic quality when comparing different fMRI data acquisition methods.
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| 16. |
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| 17. |
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| 18. |
- van Ettinger-Veenstra, Helene M, et al.
(författare)
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Right-hemispheric brain activation correlates to language performance
- 2010
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Ingår i: NEUROIMAGE. - : Elsevier BV. - 1053-8119. ; 49:4, s. 3481-3488
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Tidskriftsartikel (refereegranskat)abstract
- Language function in the right-hemispheric homologues of Brocas and Wernickes areas does not only correlate with left-handedness or pathology, but occurs naturally in right-handed healthy subjects as well. In the current study, two non-invasive methods of assessing language lateralization are correlated with behavioral results in order to link hemispheric dominance to language ability in healthy subjects. Functional magnetic resonance imaging (fMRI) together with a sentence-completion paradigm was used to determine region-specific lateralization indices in the left- and right-sided Brocas and Wernickes areas, the frontal temporal lobe, the anterior cingulate cortex and the parietal lobe. In addition, dichotic listening results were used to determine overall language lateralization and to strengthen conclusions by correlating with fMRI indices. Results showed that fMRI lateralization in the superior parietal, the posterior temporal, and the anterior cingulate cortices correlated to dichotic listening. A decreased right ear advantage (REA), which indicates less left- hemispheric dominance in language, correlated with higher performance in most administered language tasks, including reading, language ability, fluency, and non-word discrimination. Furthermore, right hemispheric involvement in the posterior temporal lobe and the homologue of Brocas area suggests better performance in behavioral language tasks. This strongly indicates a supportive role of the right-hemispheric counterparts of Brocas and Wernickes areas in language performance.
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| 19. |
- van Ettinger-Veenstra, Helene, 1982-, et al.
(författare)
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Right-hemispheric cortical contributions to language ability in healthy adults
- 2012
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Ingår i: Brain and Language. - : Elsevier. - 0093-934X .- 1090-2155. ; 120:3, s. 395-400
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Tidskriftsartikel (refereegranskat)abstract
- In this study we investigated the correlation between individual linguistic ability based on performance levels and their engagement of typical and atypical language areas in the brain. Eighteen healthy subjects between 21 and 64 years participated in language ability tests, and subsequent functional MRI scans measuring brain activity in response to a sentence completion and a word fluency task. Performance in both reading and high-level language tests correlated positively with increased right-hemispheric activation in the inferior frontal gyrus (specifically Brodmann area 47), the dorsolateral prefrontal cortex (DLPFC), and the medial temporal gyrus (Brodmann area 21). In contrast, we found a negative correlation between performance and left-hemispheric DLPFC activation. Our findings indicate that the right lateral frontal and right temporal regions positively modulate aspects of language ability.
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