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functional_magnetic_resonance_imaging

Functional magnetic resonance imaging

Functional magnetic resonance imaging or functional MRI (fMRI) is a functional neuroimaging procedure using MRI technology.

At present, presurgical functional mapping is the most prevalent clinical application of functional magnetic resonance imaging (fMRI).

Advantages

fMRI for clinical routine is a reliable and rapid method for identification of functional brain areas prior to brain surgery adjacent to functional areas. This method allows direct monitoring of the data quality and visualization without being time consuming. Knowledge about the relation of functional areas to the brain lesions improves the preoperative planning, the operation strategy and decision making with patients 1).

Functional MRI (fMRI) can be used to measure neural activation by measurement of changes in blood oxygenation using the blood oxygen level dependent technique which is sensitive to local changes in the magnetic field induced by the presence of deoxygenated haemoglobin 2).

In a typical block-design application, the subject alternates between a passive resting state and performing a task. Clinical applications of task-based fMRI have focused on localizing areas of critical function for presurgical planning 3) and have been shown to correlate with intraoperative electrophysiology 4) Wada testing 5) and prediction of loss of function postoperatively 6).

Disadvantages

Despite its utility, task-based fMRI has several disadvantages that limit its application for preoperative functional localization.

Although it is a potentially powerful presurgical tool, fMRI can be fraught with artifacts, leading to interpretive errors, many of which are not fully accounted for in routinely applied correction methods.

The results are dependent on how well the patient can perform the prescribed task. In the setting of a brain tumor, cooperation and effective participation may be impaired due to neurological deficits or confusion 7). Second, because the patient must be awake during the imaging procedure, sedation cannot be used. This often limits effective imaging in pediatric populations for whom conscious sedation is frequently necessary. Finally, task-based fMRI can be lengthy if multiple functional sites are interrogated in a single imaging session.

As an alternative to task-based fMRI, resting state functional magnetic resonance imaging (rs-fMRI) has been proposed as an imaging methodology for localizing critical sites independent of patient participation 8).

The addition of independent component analysis denoising of fMRI data in preoperative patients with glioma has a significant impact on data quality, resulting in reduced false-positives and an increase in true-positives compared with more commonly applied motion scrubbing or simple realignment methods 9).

Indications

Mapping of language area

see Preoperative mapping of language area Functional MRI (fMRI) can assess language lateralization in brain tumor patients; however, this can be limited if the primary language area-Broca's area (BA)-is affected by the tumor.

Recent research indicates the value of including fMRI maps of attentional tasks along with traditional language-processing tasks in preoperative planning in patients undergoing neurosurgery procedures 10).


Functional magnetic resonance imaging (fMRI) is a noninvasive and reliable tool for mapping eloquent cortex in patients prior to brain surgery. Ensuring intact perceptual and cognitive processing is a key goal for neurosurgeons, and recent research has indicated the value of including attentional network processing in pre-surgical fMRI in order to help preserve such abilities, including reading, after surgery.


The integration of anatomical and functional studies allows a safe functional resection of the brain tumors located in eloquent areas. Multimodal navigation allows integration and correlation among preoperative and intraoperative anatomical and functional data. Cortical motor functional areas are anatomically and functionally located preoperatively thanks to MR and functional magnetic resonance imaging and subcortical motor pathways with Diffusion tensor imaging and tractography. Intraoperative confirmation is done with cortical stimulation (CS) and N20 inversion wave for cortical structures and with subcortical stimulation (sCS) for subcortical pathways 11).

1)
Mahvash M, Maslehaty H, Jansen O, Mehdorn HM, Petridis AK. Functional magnetic resonance imaging of motor and language for preoperative planning of neurosurgical procedures adjacent to functional areas. Clin Neurol Neurosurg. 2014 Aug;123:72-7. doi: 10.1016/j.clineuro.2014.05.011. Epub 2014 May 29. PubMed PMID: 25012016.
2)
Ward NS, Frackowiak RS. The functional anatomy of cerebral reorganisation after focal brain injury. J Physiol Paris 2006;99:425-36.
3)
Matthews PM, Honey GD, Bullmore ET. Applications of fMRI in translational medicine and clinical practice. Nat Rev Neurosci. 2006;7(9):732-744.
4)
Vlieger EJ, Majoie CB, Leenstra S, Den Heeten GJ. Functional magnetic resonance imaging for neurosurgical planning in neurooncology. Eur Radiol. 2004;14(7):1143-1153.
5)
Adcock JE, Wise RG, Oxbury JM, Oxbury SM, Matthews PM. Quantitative fMRI assessment of the differences in lateralization of language-related brain activation in patients with temporal lobe epilepsy. Neuroimage. 2003;18(2):423-438.
6)
Håberg A, Kvistad KA, Unsgård G, Haraldseth O. Preoperative blood oxygen level-dependent functional magnetic resonance imaging in patients with primary brain tumors: clinical application and outcome. Neurosurgery. 2004;54(4):902-914; discussion 914-905.
7)
Pujol J, Conesa G, Deus J, López-Obarrio L, Isamat F, Capdevila A. Clinical application of functional magnetic resonance imaging in presurgical identification of the central sulcus. J Neurosurg. 1998;88(5):863-869.
8)
Zhang D, Johnston JM, Fox MD, et al. Preoperative sensorimotor mapping in brain tumor patients using spontaneous fluctuations in neuronal activity imaged with functional magnetic resonance imaging: initial experience. Neurosurgery. 2009;65(6 suppl):226-236
9)
Middlebrooks EH, Frost CJ, Tuna IS, Schmalfuss IM, Rahman M, Old Crow A. Reduction of Motion Artifacts and Noise Using Independent Component Analysis in Task-Based Functional MRI for Preoperative Planning in Patients with Brain Tumor. AJNR Am J Neuroradiol. 2016 Nov 10. doi: 10.3174/ajnr.A4996. [Epub ahead of print] PubMed PMID: 28056453.
10)
Mickleborough MJ, Kelly ME, Gould L, Ekstrand C, Lorentz E, Ellchuk T, Babyn P, Borowsky R. Inclusion of attentional networks in the pre-surgical neuroimaging assessment of a large deep hemispheric cavernous malformation: an FMRI case report. Cerebrovasc Dis. 2015;39(3-4):202-8. doi: 10.1159/000376612. Epub 2015 Mar 14. PubMed PMID: 25791396.
11)
González-Darder JM, González-López P, Talamantes F, Quilis V, Cortés V, García-March G, Roldán P. Multimodal navigation in the functional microsurgical resection of intrinsic brain tumors located in eloquent motor areas: role of tractography. Neurosurg Focus. 2010 Feb;28(2):E5. doi: 10.3171/2009.11.FOCUS09234. PubMed PMID: 20121440.
functional_magnetic_resonance_imaging.txt · Last modified: 2017/08/15 22:51 by administrador