John A. Sanders

Comparison of primary motor cortex localization using functional magnetic resonance imaging and magnetoencephalography

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 t‐test processing. MEG primary motor field was characterized by a single dipole model. Comparisons between the location of the best‐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.

Areas of interictal spiking are associated with Metabolic dysfunction in MRI-negative temporal lobe epilepsy

Summary:  Purpose: The objective of our study was to determine noninvasively whether metabolic dysfunction is present in focal areas of interictal electrophysiologic abnormality and whether metabolic dysfunction correlates with frequency of spiking.

MRI morphometry of mamillary bodies, caudate nuclei, and prefrontal cortices after chemotherapy for childhood leukemia: multivariate models of early and late developing memory subsystems.

Neurotoxic intrathecal chemotherapy for childhood acute lymphoblastic leukemia (ALL) affects developing structures and functions of memory and learning subsystems selectively. Results show significant reductions in magnetic resonance imaging morphometry of mamillary bodies, components of the corticolimbic-diencephalic subsystem subserving functionally later developing, single-trial memory, nonsignificant changes in bilateral heads of the caudate nuclei, components of the corticostriatal subsystem subserving functionally earlier developing, multitrial learning, significant reductions in prefrontal cortical volume, visual and verbal single-trial memory deficits, and visuospatial, but not verbal, multitrial learning deficits. Multiple regression models provide evidence for partial dissociation and connectivity between the subsystems, and suggest that greater involvement of caudate may compensate for inefficient corticolimbic-diencephalic components.

CHAPTER 7 – Functional Magnetic Resonance Imaging

Publisher Summary This chapter focuses on functional magnetic resonance imaging (FMRI). Techniques that can localize functional activity can provide clinically relevant information in cases of distorted or uncertain brain anatomy. Functional imaging is also valuable in the surgical treatment of brain lesions. In many cases, the precise localization of essential functional cortex is required to minimize postoperative neurologic deficit yet allow maximum removal of diseased or dysfunctional tissue. The preoperative identification of essential functional regions allows evaluation of both surgical feasibility and approach. The resulting clinical benefits include improved identification of candidates for successful surgery, improved outcome of those surgeries undertaken, and reduced overall treatment cost. Presurgical localization of critical functional regions is an area where FMRI can be immediately clinically useful. FMRI offers the possibility of performing these localizations routinely and on existing rather than expensive new instrumentation. Image acquisition and processing times are similar to those for structural MRI examinations and allow the ready integration of FMRI into existing radiology practice.

Design and implementation of a clinical MSI workstation

It is noted that magnetic source imaging (MSI) has unique processing and presentation requirements that must be addressed for it to become incorporated into clinical practice. As the combination of multislice medical imaging, particularly magnetic resonance imaging (MRI), and magnetoencephalography (MEG) functional localization, MSI is heavily computer-dependent for data preparation and evaluation as well as for data generation. The general issues of volumetric display and manipulation are compounded by the necessity for geometric accuracy and for interactive preparation of the data to be clinically evaluated. The authors discuss the design and implementation of a workstation-based system for processing MRI and MEG data and generating the combination of functional/anatomical images.<<ETX>>

Clinical Brain Imaging: Computerized Axial Tomography and Magnetic Resonance Imaging

This chapter discusses clinical brain imaging and provides an overview of computerized axial tomography and magnetic resonance imaging. The introduction of computerized axial tomography (CAT or CT) and magnetic resonance imaging (MRI or MR) into the field of brain imaging has resulted in dramatic improvements in the evaluation of suspected intracranial abnormalities. The chapter provides an overview of these two techniques. Magnetic resonance imaging (MRI) represents a recent and dramatic advance in neurodiagnostic imaging. This noninvasive anatomic/pathologic imaging technique utilizes magnetic fields and radiofrequency (RF) energy to manipulate atomic nuclei. The essential components of a CT scanner include the gantry, x-ray source, detection system, computer, and display network. Although MRI represents one of the most sophisticated and detailed central nervous system evaluations possible, there are limitations to this technique. A wide variety of artifacts exist, with the most common being patient motion. X-ray computed tomography (CT), positron emission tomography (PET), single photon emission computed tomography (SPECT), and nuclear magnetic resonance imaging (MRI) all fall in the general imaging class of reconstruction of the object from their projections. Tomography refers to the creation of images in slices or sections.

Practical, computer-aided registration of multiple, three-dimensional, magnetic-resonance observations of the human brain

We define a methodology for aligning multiple, three-dimensional, magnetic-resonance observations of the human brain over six degrees of freedom. The observations may be taken with disparate resolutions, pulse sequences, and orientations. The alignment method is a practical combination of off-line and interactive computation. An off-line computation first automatically performs a robust surface extraction from each observation. Second, an operator executes interactively on a graphics workstation to produce the alignment. For our experiments, we were able to complete both alignment tasks interactively, due to the quick execution of our implementation of the off-line computation on a highly-parallel supercomputer. To assess accuracy of an alignment, we also propose a consistency measure.