Biomedical subjects

Victor Haughton

Publications and source records attributed to Victor Haughton.

11 recordsLinked to original sources

PubMed2006

Imaging intervertebral disc degeneration.

Magnetic resonance imaging provides excellent anatomic detail of spinal tissues, but fails to provide the type of information that permits a definitive diagnosis in many patients with back pain. New imaging strategies that can be applied to the study of intervertebral disc degeneration include diffusion-weighted imaging, magnetic resonance imaging, diffusion tensor imaging, magnetic resonance spectroscopy, functional magnetic resonance imaging, dynamic computed tomography and magnetic resonance imaging, and T2 relaxometry. With dynamic imaging, the relative motions of normal and degenerated lumbar motion segments can be evaluated noninvasively. With further evaluation of the technique, hypermobile segments may be distinguishable from those with normal relative motion. T2 measurements obtained by T2 relaxometry appear to have important advantages with regard to spinal imaging because this modality provides a continuous and objective measure of the content of free water in the disc, which decreases with aging and degeneration. Anatomic imaging of the spine is highly accurate in the evaluation of nonmechanical causes of back pain and less beneficial in the evaluation of back pain that is due to mechanical causes. The development of functional imaging strategies of the spine will likely improve the management of patients with back pain. This article outlines the current magnetic resonance imaging protocols for intervertebral disc degeneration, indicates deficiencies in current imaging, and describes functional imaging strategies for the spine that will likely improve the evaluation of patients with back pain. It also reviews recent published articles on magnetic resonance imaging and computed tomographic imaging of the spine and details the results of studies that have explored the future potential of spine imaging.

Diagnostic Imaging↗

PubMed2005

Accuracy of an automated method to measure rotations of vertebrae from computerized tomography data.

STUDY DESIGN: In this phantom study, rotations of a vertebral body calculated from computerized tomography (CT) were compared to the actual rotations provided by a specially designed device incorporating a reduction gear. OBJECTIVE: The objective was to measure the accuracy of the CT and an automated software program to calculate rotations of lumbar vertebral bodies. BACKGROUND: Rotations of individual vertebrae secondary to a change in position or load can be measured in select patients by roentgen stereophotogrammetry or by using CT and a specially constructed table that creates the rotation of the torso. The purpose of this study was to measure the precision and accuracy of rotation measurements made with a CT scanner and an automated program to calculate rotation. METHODS: We constructed a phantom with a lumbar vertebra that can be rotated within a CT scanner. CT of the vertebra were obtained at angular positions of 0, 0.360 degrees , 1.080 degrees , 2.520 degrees , 5.400 degrees , 11.160 degrees , 29.160 degrees , 29.340 degrees , 29.520 degrees , 29.610 degrees , 29.700 degrees , 29.790 degrees , 29.880 degrees , and 29.889 degrees . With an automated program based on a pixel-shift algorithm, we calculated rotations of the vertebra between pairs of images. Accuracy was calculated as mean difference between the actual and the calculated rotation, and precision was calculated as the standard deviation of the differences. RESULTS: Differences between actual and calculated rotations varied from -0.083 degrees to 0.132 degrees . For rotations less than 15 degrees , mean error (accuracy) was -0.039 degrees , and the standard deviation (precision) was 0.029 degrees . For rotations greater than 15 degrees , the accuracy was 0.086 degrees , and the precision was 0.023 degrees . CONCLUSIONS: This study shows that rotations of lumbar vertebrae may be measured with CT, and an automated program to an accuracy and precision better than 0.1 degrees , comparable to that of roentgen stereophotogrammetry.

Humans↗

PubMed2005

Age-related variations in peak cerebrospinal fluid velocities in the foramen magnum.

OBJECT: Measurements of cerebrospinal fluid (CSF) velocities in the foramen magnum are used to determine the functional significance of Chiari malformation Type I (CM-I). Significantly higher peak velocities are found in adult patients with CM-I than in adult control participants. In addition, it appears that higher CSF velocities are found in pediatric patients with CM-I than in adult patients. Variations in CSF velocities across age groups in healthy individuals, however, have not been systematically studied. METHODS: Phase-contrast magnetic resonance imaging was performed in 10 pediatric patients after induction of anesthesia to evaluate conditions thought not to affect CSF flow in the foramen magnum. The peak systolic and diastolic velocities were plotted with respect to age and compared with velocities obtained in a group of 10 healthy adult volunteers. Differences between the adult and pediatric groups were tested for significance by using the Student t-test. Peak velocities ranged from 1.9 to 19.9 cm/second in the pediatric group and from 1.2 to 4.5 cm/second in the adults. A trend line fitted to the data showed a decrease in velocity with age in the first two decades of life, and little change thereafter. Differences in the pediatric and adult groups were significant at a level of 0.05. CONCLUSIONS: Peak CSF velocities vary significantly with age. To determine the normalcy of a CSF flow measurement, it must be compared with age-appropriate normative data.

Adolescent↗

PubMed2005

PC VIPR: a high-speed 3D phase-contrast method for flow quantification and high-resolution angiography.

BACKGROUND AND PURPOSE: Three-dimensional phase-contrast (3DPC) is limited by long imaging times, limited coverage, flow artifacts, and the need to perform multiple additional 2D examinations (2DPC) to measure flow. A highly undersampled 3D radial acquisition (isotropic-voxel radial projection imaging [PCVIPR]) makes it possible to increase the product of volume coverage and spatial resolution by a factor of 30 for the same imaging time as conventional Cartesian 3DPC. This provides anatomic information over a large volume with high isotropic resolution and permits retrospective measurement of average flow rates throughout the volume. METHODS: PCVIPR acquires a reference and three flow-encoded acquisitions for each VIPR projection. Complex difference images were formed by combining information from all flow directions. Following retrospective definition of planes perpendicular to selected vessels, volume flow rates were determined by using phase-difference information. The accuracy of average flow measurement was investigated in a phantom and in six volunteers. Anatomic PCVIPR images acquired in three patients and three volunteers by using a 384(3) matrix were compared with conventional Cartesian 3DPC. RESULTS: The flow validation produced R2 = 0.99 in vitro and R2 = 0.97 in vivo. PCVIPR produced minimal streak and pulsatile flow artifacts. PCVIPR produced far higher resolution and volume coverage in comparable imaging times. The highest acceleration factors relative to 3DPC were achieved by using gadolinium-contrast material. Ultimately, acceleration factors are limited by signal-to-noise ratio. CONCLUSION: PCVIPR rapidly provides isotropic high-resolution angiographic images and permits retrospective measurement of average flow rate throughout the volume without the need to prescribe multiple 2D acquisition planes.

Adult↗

PubMed2004

Medical imaging of intervertebral disc degeneration: current status of imaging.

STUDY DESIGN: The author reviewed literature and reports on spine imaging, selected key articles in which novel imaging strategies were described, and prepared a review of currently developing imaging strategies in intervertebral disc degeneration. OBJECTIVES: To provide a review of imaging in intervertebral disc degeneration that covers the current methodology briefly and describes developing techniques in detail. SUMMARY OF BACKGROUND DATA: Computed tomography and magnetic resonance imaging provide excellent anatomic images of the spine. However, anatomic imaging of the spine does not reliably identify the source of pain in patients with intervertebral disc degeneration. Many functional imaging techniques are suited to the study of the spine. Some of these techniques will improve our understanding of intervertebral disc degeneration and clinical symptomatology. METHODS: The author selected reports in the current literature for further review and attempted to describe succinctly the material in the reports that are most relevant to spine imaging. RESULTS: New and potentially useful imaging strategies for spine imaging include dynamic computed tomography, dynamic magnetic resonance imaging, functional magnetic resonance imaging, diffusion imaging, and magnetic resonance spectroscopy. CONCLUSIONS: Technological advances in magnetic resonance imaging and computed tomography imaging continue to offer more opportunities to investigate and diagnose back pain and intervertebral disc degeneration.

Back Pain↗

PubMed2004

Cerebrospinal fluid flow in foramen magnum: temporal and spatial patterns at MR imaging in volunteers and in patients with Chiari I malformation.

PURPOSE: To measure spatial and temporal variations in cerebrospinal fluid (CSF) flow through the cardiac cycle and throughout the subarachnoid space at magnetic resonance (MR) imaging in volunteer subjects with no known neurologic or spinal problems and in patients with Chiari I malformation. MATERIALS AND METHODS: A cardiac-gated phase-contrast MR technique was used to acquire images at 14 time points evenly spaced through the cardiac cycle in 10 volunteers and eight patients with Chiari I malformation. Instantaneous CSF velocities were displayed as temporal and spatial plots and examined for homogeneity, differences between flow anterior and flow posterior to the spinal cord, synchronous bidirectional flow, and equivalence of the caudad flow and craniad flow in each voxel. Indexes for flow homogeneity, synchronous bidirectional flow, and preferential flow direction were calculated, and differences between the patient and volunteer groups were tested for significance with a t test of the means. RESULTS: In volunteers, diastolic velocity peaked in two regions in the anterior paramedial subarachnoid space. Patients had greater inhomogeneity of flow than volunteers. They had substantially increased flow (jets) in the anterior paramedial locations. Synchronous bidirectional flow was seen in six of the patients and in none of the volunteers. Cephalad flow in the jets or nodes (P =.05), proportion of cephalad and caudad flow in the anterior compartment (P <.005 for both), and the fraction of voxels with flow directionality (P =.03) differed significantly between patients and volunteers. CONCLUSION: CSF flow in symptomatic patients with Chiari I malformation, unlike that in volunteer subjects, is characterized by flow jets, regions with a preponderance of flow in one direction, and synchronous bidirectional flow.

Adult↗

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

Functional MR imaging: paradigms for clinical preoperative mapping.

Clinical applications of functional MR imaging include mapping of brain functions in relationship to intracranial tumors, seizure foci, or vascular malformations to determine the risk for performing surgical excision, the need for intraoperative mapping during excision, and selecting the optimal surgical approach to a lesion. A variety of paradigms are used to produce a blood-oxygen-level-dependent response in various brain regions, which can be identified with functional MR imaging. The paradigms used include active motor, language, or cognitive tasks, and passive tactile, auditory, or visual stimuli. Activation usually indicates the location of eloquent cortex. Lack of function in a region cannot be assumed when functional MR imaging shows absence of activation within the region.

Acoustic Stimulation↗

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↗