Magnetic Resonance Imaging (MRI)

Diseases of the spinal cord are associated with reactive changes in cerebral cortex organization. Many studies in this area have examined spinal cord conditions not associated with recovery, making it difficult to consider the value of these cortical events in the restoration of neurological function. We studied patients with myelitis, a syndrome of transient spinal cord inflammation, in order to probe cortical changes that might contribute to recovery after disease of the spinal cord.

Previous studies have shown that unilateral finger movements are normally accompanied by a small activation in ipsilateral motor cortex. The magnitude of this activation has been shown to be altered in a number of conditions, particularly in association with stroke recovery. The site of this activation, however, has received limited attention. To address this question, functional magnetic resonance imaging (MRI) was used to study precentral gyrus activation in six control and three stroke patients during right index finger tapping, then during left index finger tapping.

Measuring tissue blood flow with NMR imaging of intravascular tracers is more difficult than measurements of tissue blood volume. One major obstacle to the application of the Central Volume Principle is the direct measurement of the mean transit time. In this note, we demonstrate that mean transit time (MTT), which relates tissue blood volume to blood flow via the Central Volume Principle, is not the first moment of the concentration-time curve for MR or CT imaging of purely intravascular tracers.

BACKGROUND: The anterior cingulate cognitive division (ACcd) plays a central role in attentional processing by: 1) modulating stimulus selection (i.e., focusing attention) and/or 2) mediating response selection. We hypothesized that ACcd dysfunction might therefore contribute to producing core features of attention-deficit/hyperactivity disorder (ADHD), namely inattention and impulsivity. ADHD subjects have indeed shown performance deficits on the Color Stroop, an attentional/cognitive interference task known to recruit the ACcd.

To produce behavior, motivational states necessitate at least three fundamental operations, including (1) selection of objectives focused on goal-objects, (2) compilation of goal-object information, and (3) determination of physical plans for securing goal-objects.

Neovascularization is a common phenomenon in gliomas. MR imaging cerebral blood volume (CBV) mapping utilizes ultrasfast echo-planar imaging and simultaneous use of gadolinium-based contrast material. To determine the utility of MR CBV mapping in the clinical evaluation of gliomas, we followed 15 patients with serial studies. This technique provided functional information that was not evident with conventional CT or MR imaging. Low-grade tumors demonstrated homogeneously low CBV, while high-grade tumors often showed areas of both high and low CBV.

High-field spectroscopic studies at 5.88 tesla (T) indicate significant T2* shortening of water in suspensions of powdered bone, interpreted to be a result of magnetic susceptibility differences between bone particles and water. The authors investigated the effects of magnetic susceptibility differences between trabecular bone and water on magnetic resonance (MR) images at 0.6 T. The phantom was constructed of macerated intact trabecular human bone immersed in water.

Standard T1- and T2-weighted spin-echo acquisitions were compared with T1- and T2-weighted phase-contrast techniques in a series of 10 consecutive patients with parotid masses to assess the role of phase-contrast methods in the evaluation of lesions in the parotid fossa. Greater tissue-lesion contrast was obtained with phase-contrast methods in nine of 10 cases, allowing improved lesion visualization; however, an increase in lesion detectability was not observed in this series.

BACKGROUND AND PURPOSE: Animal studies have described remodeling of sensory and motor representational maps after cortical infarct. These changes may contribute to return of function after stroke.
METHODS: Functional MRI was used to compare sensory and motor maps obtained in 35 normal control subjects with results from 2 patients with good recovery 6 months after a cortical stroke.

Twenty-three patients with type 1 Gaucher disease were evaluated with a battery of quantitative imaging techniques. Plain radiographs were used to measure cortical thickness and Erlenmeyer flask deformity. Xenon-133 uptake was measured in scans of the lower extremities. Dual-energy quantitative computed tomography was used for calculation of trabecular bone and bone marrow fat content in the spine and long bones. Magnetic resonance (MR) imaging was performed to evaluate disease extent and three-dimensional splenic volume.