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| 2. |
- Olsrud, Johan, et al.
(författare)
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A two-compartment gel phantom for optimization and quality assurance in clinical BOLD fMRI
- 2008
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Ingår i: Magnetic Resonance Imaging. - : Elsevier BV. - 1873-5894 .- 0730-725X. ; 26:2, s. 279-286
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Tidskriftsartikel (refereegranskat)abstract
- Clinical applications of blood oxygen level-dependent (BOLD) functional magnetic resonance imaging (fMRI) depend heavily on robust paradigms, imaging methods and analysis procedures. In this work, as a means to optimize and perform quality assurance of the entire imaging and analysis chain, a phantom that provides a well known and reproducible signal change similar to a block type fMRI experiment is presented. It consists of two gel compartments with slightly different T(2) that dynamically enter and leave the imaged volume. The homogeneous gel in combination with a cylindrical geometry results in a well-defined T(2) difference causing a signal difference between the two compartments in T(2)-weighted MR images. From time series data obtained with the phantom, maps of percent signal change (PSC) and t-values are calculated. As an example of image parameter optimisation, the phantom is demonstrated to be useful for accurate determination of the influence of echo time (TE) on BOLD fMRI results, taking the t-value as a measure of sensitivity. In addition, the phantom is proposed as a tool for quality assurance (QA) since reproducible time series and t-maps are obtained in a series of independent repeat experiments. The phantom is relatively simple to build and can therefore be used by any clinical fMRI center.
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| 4. |
- van Westen, Danielle, et al.
(författare)
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Bilder av hjärnan arbete.
- 2008
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Ingår i: Läkartidningen. - 0023-7205. ; 105:47, s. 3438-3442
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Tidskriftsartikel (refereegranskat)
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| 5. |
- van Westen, Danielle, et al.
(författare)
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Functional magnetic resonance imaging at 3T as a clinical tool in patients with intracranial tumors.
- 2005
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Ingår i: Acta Radiologica. - : SAGE Publications. - 1600-0455 .- 0284-1851. ; 46:6, s. 599-609
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Tidskriftsartikel (refereegranskat)abstract
- Purpose: To investigate the potential of functional magnetic resonance imaging (fMRI) at 3T as a clinical tool in the preoperative evaluation of patients with intracranial tumors. High magnetic field strength such as 3T is of benefit for fMRI because signal-to-noise ratio and sensitivity to susceptibility changes are field-strength-dependent. Material and Methods: Twenty patients with tumors close to eloquent sensorimotor or language areas were studied. Motor, sensory, and two language paradigms (word generation, rhyming) were used; their effectiveness was determined as the percentage of patients in whom the functional area of interest was activated. Activation maps were calculated and their quality rated as high, adequate, or insufficient. The influence of fMRI on the neurosurgical decision regarding operability, surgical approach, and extent of the resection, was assessed. Results: Paradigm effectiveness was 90% for motor and 95% for sensory stimulation, and varied from 79% to 95% for word generation and rhyming in combination. Ninety percent of the activation maps held high or adequate quality. fMRI proved useful: in the decision to operate (9 patients), in the surgical approach (13 patients), and in extent of the resection (12 patients). Conclusion: fMRI at 3T is a clinically applicable tool in the work-up of patients with intracranial tumors.
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| 6. |
- Waites, Anthony B, et al.
(författare)
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Flexible statistical modelling detects clinical functional magnetic resonance imaging activation in partially compliant subjects.
- 2007
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Ingår i: Magnetic Resonance Imaging. - : Elsevier BV. - 1873-5894 .- 0730-725X. ; 25:2, s. 188-196
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Tidskriftsartikel (refereegranskat)abstract
- Clinical functional magnetic resonance imaging (MRI) occasionally fails to detect significant activation, often due to variability in task performance. The present study seeks to test whether a more flexible statistical analysis can better detect activation, by accounting for variance associated with variable compliance to the task over time. Experimental results and simulated data both confirm that even at 80% compliance to the task, such a flexible model outperforms standard statistical analysis when assessed using the extent of activation (experimental data), goodness of fit (experimental data), and area under the operator characteristic curve (simulated data). Furthermore, retrospective examination of 14 clinical fMRI examinations reveals that in patients where the standard statistical approach yields activation, there is a measurable gain in model performance in adopting the flexible statistical model, with little or no penalty in lost sensitivity. This indicates that a flexible model should be considered, particularly for clinical patients who may have difficulty complying fully with the study task. (c) 2007 Elsevier Inc. All rights reserved.
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