Magnetic Resonance Imaging (MRI)

Subject motion during scanning can greatly reduce MRI image quality and is a major reason for discarding data in both clinical and research scanning. The quality of the high-resolution structural data used for morphometric analysis is especially compromised by subject movement because high-resolution scans are of longer duration. A method is presented that measures and corrects rigid body motion and associated first-order shim changes in real time, using a pulse sequence with embedded cloverleaf navigators and a feedback control mechanism.

Considerable evidence indicates that a stimulus that is subthreshold, and thus consciously invisible, influences brain activity and behavioral performance. However, it is not clear how subthreshold stimuli are processed in the brain. We found that a task-irrelevant subthreshold coherent motion led to a stronger disturbance in task performance than did suprathreshold motion. With the subthreshold motion, activity in the visual cortex measured by functional magnetic resonance imaging was higher, but activity in the lateral prefrontal cortex was lower, than with suprathreshold motion.

Face perception is a skill crucial to primates. In both humans and macaque monkeys, functional magnetic resonance imaging (fMRI) reveals a system of cortical regions that show increased blood flow when the subject views images of faces, compared with images of objects. However, the stimulus selectivity of single neurons within these fMRI-identified regions has not been studied. We used fMRI to identify and target the largest face-selective region in two macaques for single-unit recording.

Physiological noise dominates the SNR of the fMRI time-course at commonly used spatial resolutions at field strengths of 3 T and above. Operating in this physiological noise dominated regime limits some benefits of high field acquisition since increases in image SNR produce only modest increases in time-course SNR. Although previous studies have shown that the physiological noise dominance can be mitigated by using higher spatial resolutions, not all functional studies require voxel sizes smaller than the thickness of the human cortex.

Cancer is a diverse disease with many manifestations. Magnetic resonance (MR) has a wide range of sensitivities, and therefore has often been used to study cancer in humans in numerous different ways, most typically with MR spectroscopy and MR imaging. This article is not an exhaustive catalog of the use of MR in cancer, but will briefly highlight some of the many promising MR methods that have been developed, proposed, or used to focus on the problem of detecting and characterizing cancer, its treatments, and adverse effects.

Functional MRI (fMRI) has tremendous clinical potential that is as yet unrealized. There are tremendous unmet medical needs that fMRI could address with significant benefit to human health. However, both medical and technical barriers prevent this benefit from accruing today. Technical barriers may be the reflexive focus of the current practitioners of fMRI, a technically savvy group. However, the real challenge lies in the medical realm, and this will require multidisciplinary and interdisciplinary work since the technical aspects of fMRI are ahead of the medical aspects.

Categories like "noun" and "verb" represent the basic units of grammar in all human languages, and the retrieval of categorical information associated with words is an essential step in the production of grammatical speech. Studies of brain-damaged patients suggest that knowledge of nouns and verbs can be spared or impaired selectively; however, the neuroanatomical correlates of this dissociation are not well understood. We used event-related functional MRI to identify cortical regions that were active when English-speaking subjects produced nouns or verbs in the context of short phrases.

Spatially selective RF waveforms were designed and demonstrated for parallel excitation with a dedicated eight-coil transmit array on a modified 3T human MRI scanner. Measured excitation profiles of individual coils in the array were used in a low-flip-angle pulse design to achieve desired spatial target profiles with two- (2D) and three-dimensional (3D) k-space excitation with simultaneous transmission of RF on eight channels.

The kinematics of motor task performance affect brain activity. However, few functional magnetic resonance imaging (fMRI) motor studies have accounted for on-line kinematics because there are currently few MRI-compatible devices to record motor performance. We built a device based on Micro-Electro-Mechanical System (MEMS) gyroscopes that measures the angular velocity of one segment of each of the 10 fingers while a subject performs a finger motor task during fMRI. Finger position, acceleration, and jerk were computed from the angular velocity measurements.

Animal studies have demonstrated that motor recovery after hemiparetic stroke is associated with functional and structural brain plasticity. While studies in stroke patients have revealed functional plasticity in sensorimotor cortical areas in association with motor recovery, corresponding structural plasticity has not been shown. We sought to test the hypothesis that chronic hemiparetic stroke patients exhibit structural plasticity in the same sensorimotor cortical areas that exhibit functional plasticity.