Preoperative Mapping of the Sensorimotor Cortex: Comparative Assessment of Task-Based and Resting-State fMRI (original) (raw)
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Acta Neurochirurgica, 2009
Background Functional magnetic resonance imaging (fMRI) is a widely used method for research and visualization of the brain function. However, its clinical use is still limited. Our objective was to study fMRI reliability in localizing the primary hand motor cortex (M1) under pathological conditions caused by the proximity of a brain tumour. The results were then compared with standard technique of cortical function mapping-electric cortical stimulation (ECS). Method We compared M1 areas localized with the fMRI and ECS in 18 patients with brain tumours in fronto-parietal regions. The 1.5 T blood oxygenation-level dependent (BOLD) fMRI was performed preoperatively using a motor task involving rhythmic touching of the thumb consecu-tively with other fingers on the same hand contralateral to the affected hemisphere. Each individual fMRI result was displayed at the P < 0.05 significance level corrected for family wise error (more conservative approach) or at the P < 0.001 level uncorrected (less conservative approach) and projected on the T1-weighted image used for neuronavigation. Findings In 12 patients (66.6%) we found full agreement between the fMRI and ECS. In 3 patients (16.6%) the overlap was only partial, with one ECS testing position on motor response found outside the BOLD signal cluster. In another 3 cases (16.6%) there was a discrepancy between the two methods. The fMRI sensitivity for localizing the ECS reactive M1 cortex was 71%. The fMRI/ECS consistency was within a 5-mm range in 77% of the testing positions used for ECS which complies with the inherent accuracy of the navigation system. Conclusions Because the overlap between the two methods never exceeded 10-mm, we found that the fMRI method correctly guided the ECS to the M1 cortex in 83% of patients. Infiltrative growth of the tumour and collateral oedema were the reasons for the BOLD signal suppression in three patients. Our results support using ECS as a more reliable tool for M1 cortical mapping than fMRI.
Clinical Neurophysiology, 2003
Objective: Comparison of functional magnetic resonance imaging (fMRI) representational maps, that were generated during voluntary thumb abduction, hand dorsiflexion and foot elevation to amplitude maps of motor-evoked potentials (MEPs) elicited by single transcranial magnetic stimulation (TMS) administered to cortical motor representation areas of the muscles of the thenar eminence, extensor carpi radialis and tibialis anterior muscles.
Human Brain Mapping, 1996
The primary goal of the study was to compare estimates of motor cortex localization from functional magnetic resonance imaging (FMRI) and magnetoencephalography (MEG). Thirteen normal volunteers were studied using both methods. FMRI was performed on a clinical 1.5 T system using gradient-echo acquisitions and basic f-test processing. MEG primary motor field was characterized by a single dipole model. Comparisons between the location of the btst-fitting MEG dipole and the FMRI activation results were made using both fixed regions-of-interest weighted averaging and clustering analysis to reduce the observed FMRI activations to a single representative location.
Medical Engineering & Physics, 2011
Functional Electrical Stimulation (FES) is a well known clinical rehabilitation procedure, however the neural mechanisms that underlie this treatment at Central Nervous System (CNS) level are still not completely understood. Functional magnetic resonance imaging (fMRI) is a suitable tool to investigate effects of rehabilitative treatments on brain plasticity. Moreover, monitoring the effective executed movement is needed to correctly interpret activation maps, most of all in neurological patients where required motor tasks could be only partially accomplished. The proposed experimental set-up includes a 1.5 T fMRI scanner, a motion capture system to acquire kinematic data, and an electro-stimulation device. The introduction of metallic devices and of stimulation current in the MRI room could affect fMRI acquisitions so as to prevent a reliable activation maps analysis. What we are interested in is that the Blood Oxygenation Level Dependent (BOLD) signal, marker of neural activity, could be detected within a given experimental condition and set-up. In this paper we assess temporal Signal to Noise Ratio (SNR) as image quality index. BOLD signal change is about 1-2% as revealed by a 1.5 T scanner. This work demonstrates that, with this innovative set-up, in the main cortical sensorimotor regions 1% BOLD signal change can be detected at least in the 93% of the sub-volumes, and almost 100% of the sub-volumes are suitable for 2% signal change detection. The integrated experimental set-up will therefore allows to detect FES induced movements fMRI maps simultaneously with kinematic acquisitions so as to investigate FES-based rehabilitation treatments contribution at CNS level.
Magnetic Resonance Imaging, 1995
Functional magnetic resonance imaging (fMR1) is usually based on acquisition of alternating series of images under rest and an activation task (stimulus). Brain activation maps can be generated from fMRI data sets by applying several mathematical methods. Two methods of image postprocessing have been compared: (i) simple difference of mean values between rest and stimulation, and (ii) Student's t-test. The comparison shows that the difference method is very sensitive to arbitrary signal fluctuations as seen mainly in large vessels (e.g., in the sagittal sinus), leading to insignificantly activated spots in brain activation maps. In contrary, Student's t-test maps show strongly reduced sensitivity for fluctuations and have the advantage of giving activation thresholds by setting significance levels. This allows the comparison of activation strength between patient collectives by using a grid overlay tecbnique leading to an observer independent quantification of the stimulation effects. The method was able to reproduce previous findings of activation differences between healthy volunteers and schizophrenic patients. Moreover, a simple algorithm for the correction of slight bead movements during the functional imaging task is presented. The algorithm is based on shifting the fMRI data set relative to a reference image by maximizing the linear correlation coefficients. This leads to a further reduction of insignificant brain activation and to an improvement in brain activation map quality. methods providing objective criteria for brain acti-RECEIVED 7/11/94; ACCEPTED 2/14/95.
Current Medical Imaging Reviews, 2010
Intracranial lesions may compromise structures critical for motor performance, and mapping of the cortex, especially of the motor hand area, is important to reduce postoperative morbidity. We investigated nine patients with parietal lobe tumours and used functional MRI sensitized to changes in blood oxygenation to de®ne the di¨erent motor areas, especially the primary sensorimotor cortex, in relation to the localization of the tumour. Activation was determined by pixel-by-pixel correlation of the signal intensity time course with a reference waveform equivalent to the stimulus protocol. All subjects showed signi®cant activation of the primary sensorimotor cortex while performing a ®nger opposition task with the a¨ected and un-a¨ected side. In ®ve patients the ®nger opposition task additionally activated the ipsilateral sensorimotor cortex and the supplementary motor area (SMA). Extension and¯exion of the foot, additionally performed in two patients, also activated the sensorimotor cortex, in one case within the perifocal oedema of the tumour. Tumour localization near the central sulcus induced displacement of the sensorimotor cortex as compared to the una¨ected side in all patients with a relevant mass e¨ect. The results of our study demonstrate that functional MRI at 1.5 T with a clinically used tomograph can reproducibly localize critical brain regions in patients with intracranial lesions.
Simple fMRI Postprocessing Suffices for Normal Clinical Practice
American Journal of Neuroradiology, 2013
BACKGROUND AND PURPOSE: Whereas fMRI postprocessing tools used in research are accurate but unwieldy, those used for clinical practice are user-friendly but are less accurate. We aimed to determine whether commercial software for fMRI postprocessing is accurate enough for clinical practice. METHODS: Ten volunteers underwent fMRI while performing motor and language tasks (hand, foot, and orolingual movements; verbal fluency; semantic judgment; and oral comprehension). We compared visual concordance, image quality (noise), voxel size, and radiologist preference for the activation maps obtained by using Neuro3D software (provided with our MR imaging scanner) and by using the SPM program commonly used in research. RESULTS: Maps obtained with the 2 methods were classified as "partially overlapping" for 70% for motor and 72% for language paradigm experiments and as "overlapping" in 30% of motor and in 15% of language paradigm experiments. CONCLUSIONS: fMRI is a helpful and robust tool in clinical practice for planning neurosurgery. Widely available commercial fMRI software can provide reliable information for therapeutic management, so sophisticated, less widely available software is unnecessary in most cases. ABBREVIATIONS: LI ϭ laterality index; Tmax ϭ maximal T; Tth ϭ threshold T f MRI is increasingly being used in the clinical setting. Whereas
Journal of Neural Transmission, 1997
Multiple non-invasive methods of imaging brain function are now available for presurgical planning and neurobiological research. As these new methods become available, it is important to understand their relative advantages and liabilities, as well as how the information gained compares across different methods. A current and future trend in neurobiological studies as well as presurgical planning is to combine information from different imaging techniques. Multi-modal integration may perhaps give more powerful information than each modality alone, especially when one of the methods is transcranial magnetic stimulation (TMS), with its ability to non-invasively activate the brain. As an initial venture in cross comparing new imaging methods, we performed the following 2 studies, locating motor cortex with echoplanar BOLD fMRI and TMS. The two methods can be readily integrated, with concurring results, although each have important limitations.