Biomedical subjects

Victor Haughton

Publications and source records attributed to Victor Haughton.

4 recordsLinked to original sources

PubMed2003

White matter tractography using diffusion tensor deflection.

Diffusion tensor MRI provides unique directional diffusion information that can be used to estimate the patterns of white matter connectivity in the human brain. In this study, the behavior of an algorithm for white matter tractography is examined. The algorithm, called TEND, uses the entire diffusion tensor to deflect the estimated fiber trajectory. Simulations and imaging experiments on in vivo human brains were performed to investigate the behavior of the tractography algorithm. The simulations show that the deflection term is less sensitive than the major eigenvector to image noise. In the human brain imaging experiments, estimated tracts were generated in corpus callosum, corticospinal tract, internal capsule, corona radiata, superior longitudinal fasciculus, inferior longitudinal fasciculus, fronto-occipital fasciculus, and uncinate fasciculus. This approach is promising for mapping the organizational patterns of white matter in the human brain as well as mapping the relationship between major fiber trajectories and the location and extent of brain lesions.

Algorithms↗

PubMed2003

Role of the corpus callosum in functional connectivity.

BACKGROUND AND PURPOSE: Regional cerebral blood flow fluctuates synchronously in corresponding brain regions between the hemispheres. This synchrony implies neuronal connections between brain regions. The synchrony of blood flow changes is defined operationally as functional connectivity. Our purpose was to measure functional connectivity in patients with corpus callosal agenesis, in whom the interhemispheric connectivity is hypothetically diminished. METHODS: In three patients with agenesis of the corpus callosum, functional MR imaging was performed while patients performed text-listening and finger-tapping tasks. Functional images were also acquired while the patients performed no specific task (resting state). Regions of activation temporally correlated with the performance of the tasks were identified by cross-correlating the task data with a reference function. Voxel clusters (seed voxels) that corresponded to regions of activation in the task-activation data set were selected in the resting data set. All the voxels in the resting 3D data set that had a correlation coefficient exceeding 0.4 were identified. The number of these voxels in the ipsilateral and contralateral hemispheres was tabulated. RESULTS: In all patients, technically adequate functional MR and functional connectivity MR maps were obtained. For both tasks, activation was found in both hemispheres. For all of the seed voxels, significantly more functionally connected voxels were found in the ipsilateral hemisphere than in the contralateral hemisphere. For most seed voxels, no functionally connected voxels were found in the contralateral hemisphere. CONCLUSION: Interhemispheric functional connectivity in the motor and auditory cortices is diminished in patients with agenesis of the corpus callosum compared with that of healthy subjects.

Adult↗

PubMed2002

Diffusion-tensor imaging of white matter tracts in patients with cerebral neoplasm.

OBJECT: Preserving vital cerebral function while maximizing tumor resection is a principal goal in surgical neurooncology. Although functional magnetic resonance imaging has been useful in the localization of eloquent cerebral cortex, this method does not provide information about the white matter tracts that may be involved in invasive, intrinsic brain tumors. Recently, diffusion-tensor (DT) imaging techniques have been used to map white matter tracts in the normal brain. The aim of this study was to demonstrate the role of DT imaging in preoperative mapping of white matter tracts in relation to cerebral neoplasms. METHODS: Nine patients with brain malignancies (one pilocytic astrocytoma, five oligodendrogliomas, one low-grade oligoastrocytoma, one Grade 4 astrocytoma, and one metastatic adenocarcinoma) underwent DT imaging examinations prior to tumor excision. Anatomical information about white matter tract location, orientation, and projections was obtained in every patient. Depending on the tumor type and location, evidence of white matter tract edema (two patients), infiltration (two patients), displacement (five patients), and disruption (two patients) could be assessed with the aid of DT imaging in each case. CONCLUSIONS: Diffusion-tensor imaging allowed for visualization of white matter tracts and was found to be beneficial in the surgical planning for patients with intrinsic brain tumors. The authors' experience with DT imaging indicates that anatomically intact fibers may be present in abnormal-appearing areas of the brain. Whether resection of these involved fibers results in subtle postoperative neurological deficits requires further systematic study.

Adenocarcinoma↗

PubMedDate not supplied

Contrast between scar and recurrent herniated disk on contrast-enhanced MR images.

BACKGROUND AND PURPOSE: Ionic solutes diffuse more slowly in cartilage than do nonionic ones. The purpose of this study was to test the hypothesis that the contrast between scar and recurrent herniated disk fragment on MR images is greater after the IV administration of an ionic rather than a nonionic contrast medium. METHODS: Patients who had undergone previous laminectomy and who had MR imaging evidence of recurrent herniated disk were enrolled in the study and underwent lumbar MR imaging with the nonionic medium gadodiamide and on a subsequent day with the ionic contrast medium gadopentetate dimeglumine. Enhancement of scar and disk was measured by one of the investigators as the ratio of signal intensity change from baseline to the baseline signal intensity and was plotted as a function of time. Differences in enhancement for scar and disk fragment for the two contrast media were tested for significance by using the Student t test of the means. RESULTS: Eight patients were enrolled in the study and were studied with the two contrast media within 4 weeks. The average enhancement of the disk fragment at 5 minutes was 0.1 with the ionic medium and 0.4 with the nonionic medium. The difference was significant at P <.05. Contrast between scar tissue and disk tissue was greater with the ionic than with the nonionic medium at both 5 and 20 minutes because of the lower concentration of ionic contrast medium in the disk fragment. CONCLUSION: With clinical imaging of patients with recurrent herniated disks, disk fragments enhance less after the administration of an ionic rather than a nonionic medium. Contrast between disk fragment and scar tissue is greater after the use of an ionic contrast medium than a nonionic one.

Adult↗