JAS FMRI Program Overview:
Functional Magnetic Resonance Imaging (FMRI)
The focus of FMRI efforts at the Neuroimaging Facility have been on the development of procedures
applicable to clinically available instruments. FMRI has the potential of becoming routinely
available at no additional cost to any imaging center already having a capable clinical MRI
instrument. Our experience is helping to determine the clinical indications for this functional imaging modality, assess the accuracy of FMRI relative to other techniques, and to define the requirements for successful examinations.
At our facility, the emerging technology of FMRI is being integrated into routine radiological practice.
Procedures have been developed on the clinical MRI system that allow successful patient or
volunteer examinations to be performed within normal imaging examination durations. FMRI is
a difference technique between images acquired between resting and an activation state. (Figure 1)
Motor, somatosensory, auditory, or visual stimulation is typically employed for presurgical mapping, and research examination protocols have been established for speech, language, epilepsy, and memory.
A range of robust procedures are available to support clinical and research investigation.
Primary FMRI research activities include technology and paradigm development, application to clinical presurgical mapping, cross-
validation with electrophysiological methods such as MEG, validation with invasive cortical EEG monitoring, and general acquisition/processing improvement.
The presurgical FMRI program examines patients scheduled for surgery in order to identify
functional (e.g., somatomotor) regions relative to the pathology. The information obtained is
combined with the structural data for surgical planning and is used in conjunction with the
intraoperative localization systems (see below) to guide the neurosurgical procedure.
Application of the technology resources of the Facility to improving neurosurgical outcome
have been demonstrated and are currently being formally documented. In cases where the
patient is also studied by electrophysiologic methods, the FMRI results are compared with
MEG/EEG results for cross-validation(Figure 2). If clinically indicated, the standard intraoperative EEG
monitoring results are also available and are used to validate the non-invasive presurgical
techniques. (Figure 3)
The validation of FMRI results with those from additional modalities helps determine
localization accuracy, the significance of potential FMRI artifact mechanisms, and opportunities
for combined analysis. For example, the information from MEG and FMRI is largely
complementary. MEG directly measures neuromagnetic fields associated with neural currents
with millisecond resolution and excels in determining the time course of individual, focal
sources. FMRI directly localizes function with respect to anatomy by measuring local blood
flow changes induced by sustained neural activation and can readily identify multiple diffuse
regions of activation. In conjunction with colleagues at Los Alamos National Laboratory, MEG
signal analysis procedures utilizing FMRI information are being developed.
FMRI examination, particularly using clinical instrumentation, can be technically demanding
and research is ongoing to improve the data acquisition (sequence design to reduce patient
motion, bulk flow effects, optimize acquisition parameters, and reduce system measurement
variability), data processing (statistical, signal processing, and clustering/pattern recognition
procedures (Figure 4), and image interpretation (automated identification of FMRI image artifacts).
Last Modified: July 14, 1999
Copyright 1999 John A Sanders, VAMC