Biomedical subjects

Christopher R Tench

Publications and source records attributed to Christopher R Tench.

4 recordsLinked to original sources

PubMed2005

'Importance sampling' in MS: use of diffusion tensor tractography to quantify pathology related to specific impairment.

Specific neurological impairments in multiple sclerosis (MS) are dependent on the pathology in clinically eloquent areas of the central nervous system. We aimed to use diffusion tensor fiber tracking to identify the pyramidal tracts and corpus callosum in MS patients, measure the apparent diffusivity within the tracts, and evaluate whether this would correlate with relevant disability scores. Dual-echo and diffusion tensor magnetic resonance imaging (DT-MRI) brain scans were obtained from 29 patients with relapsing remitting MS, and 13 age and gender matched normal controls. Voxels from pyramidal tracts and corpus callosum were automatically identified using a tractography based algorithm. Mean apparent diffusion coefficient (ADC(av)) was measured for these tracts. Scores of Expanded Disability Status Scale (EDSS) and Paced Auditory Serial Addition Test (PASAT) were obtained. The median EDSS score was 2.5 (inter-quartile range 2-3.25). The ADC(av) in the pyramidal tracts (p=0.02) and corpus callosum (p=0.0004) in patients was significantly higher than in controls. Pyramidal tracts ADC(av) was correlated with pyramidal FSS (r=0.5, p=0.008). Corpus callosum ADC(av) was correlated with PASAT (r=-0.58, p=0.001). Global T2 lesion volume did not correlate with the EDSS, but correlated with ADC(av) of the pyramidal tracts (r=0.6, p=0.0007) and corpus callosum (r=0.8, p<0.0001). T2 lesion volume within the pyramidal tracts and corpus callosum correlated with ADC(av) in the pyramidal tracts (r=0.6, p=0.0009) and corpus callosum (r=0.65, p=0.0002) respectively, but not with pyramidal FSS or PASAT score. DT-MRI quantifies pathology in specific white matter tracts and may increase the specificity of MRI in monitoring progression of motor and cognitive deficits in MS.

Acoustic Stimulation↗

PubMed2005

Measurement of cervical spinal cord cross-sectional area by MRI using edge detection and partial volume correction.

PURPOSE: To detail a procedure to accurately measure upper cervical cord cross-sectional area (CSA), using MRI, by correcting for partial volume averaging (PVA), and to assess the usefulness of the procedure for measuring cervical cord atrophy rates in longitudinal studies. MATERIALS AND METHODS: Analysis of errors associated with measuring CSA in the presence of PVA is given. A numerical phantom image is produced, including simulated acquisition noise, to assess accuracy of the method in idealized conditions, and to verify the results of the error analysis. A phantom, consisting of 11 rods of known CSA, was scanned 10 times and measurement accuracy assessed. A total of 10 normal subjects were scanned twice to assess the reproducibility under experimental conditions. RESULTS: The measurement error for the numerical phantom increased with increased simulated acquisition noise, as predicted by the analysis. Measurement of the plastic phantom revealed a systematic overestimate in CSA due to limited scanner accuracy of 3.15%. The scan-rescan error for the CSA of the cervical spine in the 10 normal subjects was 0.55%. CONCLUSION: Correcting for PVA allows accurate measurement of the upper cervical cord CSA and accurate measurement of a standard phantom to guard against scanner drift in longitudinal studies of cord CSA.

Algorithms↗

PubMed2005

Spinal cord imaging in multiple sclerosis.

Multiple sclerosis (MS) is a chronic neurological condition characterized pathologically by axonal loss, demyelination, inflammation, and gliosis. Magnetic resonance imaging (MRI) has had a major impact on diagnosing MS, understanding the condition, and monitoring the effects of treatments. Recently, spinal cord MRI has received increased attention. Advanced techniques have been used to image the spinal cord, particularly the cervical cord, and measure quantitative parameters such as T1 relaxation time, magnetization transfer ratio, and diffusivity. These metrics show central nervous system abnormalities in MS patients and various correlations with disability and might reflect specific pathological processes. Image analysis techniques have also been developed and combined with high-resolution MRI to measure the cord cross-sectional area (CSA), a metric that relates to cord atrophy. The cord CSA is reduced in MS patients compared to normal controls and correlates with disability. Furthermore, changes in CSA are detectable and correlate with changes in disability. Despite the technical difficulties of performing spinal cord MRI, imaging studies, particularly of the cervical cord, are becoming more common. Significant focus has been placed on measuring cord atrophy, and reproducible techniques have been developed to measure the cervical cord CSA. Spinal cord MRI may provide information about disease progression that is not readily available from brain MRI scans and could be useful in diagnosing MS in some cases, as well as for monitoring the effects of treatments.

Atrophy↗

PubMed2004

Measurement of spinal cord atrophy in multiple sclerosis.

In multiple sclerosis (MS), the spinal cord is a common area of involvement, and its dysfunction is likely to be responsible for much of motor disability. It has been reported that atrophy in the cervical spinal cord occurs early and is detectable in patients presenting with a clinically isolated syndrome. This finding has important implications for the early treatment of patients with MS because atrophy is thought to reflect destructive, irreversible pathology and subclinical impairment. Recent clinical trials of disease-modifying agents have included spinal cord imaging and, in particular, the measurement of atrophy as a secondary or exploratory measure of treatment efficacy. This review summarizes the underlying pathology responsible for spinal cord atrophy and the methods available to measure it. The relationships between spinal cord atrophy, other magnetic resonance imaging parameters, and clinical disability are also discussed.

Atrophy↗