Biomedical subjects

Emily T Cooper

Publications and source records attributed to Emily T Cooper.

3 recordsLinked to original sources

PubMed2005

MRI diffusion coefficients in spinal cord correlate with axon morphometry.

Following spinal cord injury, diffusion MRI (DWI) has been shown to detect injury and functionally significant neuroprotection following treatment that otherwise would go undetected with conventional MRI. The underlying histologic correlates to directional apparent diffusion coefficients (ADC) obtained with DWI have not been determined, however, and we address this issue by directly correlating ADC values with corresponding axon morphometry in the normal rat cervical spinal cord. ADC values transverse (perpendicular) and longitudinal (parallel) to axons both correlate with axon counts, however each directional ADC reflects distinct histologic parameters. DWI may therefore be capable of providing specific histologic data regarding the integrity of white matter.

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PubMed2005

Spinal cord diffusion tensor imaging and fiber tracking can identify white matter tract disruption and glial scar orientation following lateral funiculotomy.

Diffusion tensor magnetic resonance imaging (DTI) provides data concerning water diffusion in the spinal cord, from which white matter tracts may be inferred, and connectivity between spinal cord segments may be determined. We evaluated this potential application by imaging spinal cords from normal adult rats and rats that received cervical lateral funiculotomies, disrupting the rubrospinal tract (RST). Vitrogen and fibroblasts were transplanted into the surgical lesion at time of injury in order to fill the cavity. At 10 weeks, animals were sacrificed; the spinal cords were dissected out and then imaged in a 9.4-Tesla magnet. DTI tractography demonstrated the disruption of the rubrospinal tract axons while indicating which axon tracts were preserved. Additionally, DTI imaging could identify the orientation of glial processes in the gray matter adjacent to the site of injury. In the injured animals, reactive astrocytes in adjacent gray matter appeared to orient themselves perpendicular to white matter tracts. In summary, DTI identified not only white matter disruption following injury, but could distinguish the orientation of the accompanying glial scar.

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PubMed2005

Ex vivo evaluation of ADC values within spinal cord white matter tracts.

BACKGROUND AND PURPOSE: Our purpose was to evaluate the effect of fixative on apparent diffusion coefficient (ADC) values and anisotropy within spinal cord white matter. As glutaraldehyde (GL) better preserves axonal ultrastructure as compared with paraformaldehyde (PF), we hypothesize that spinal cord white matter fixed with GL will have increased anisotropic water diffusion as compared with specimens fixed with PF. METHODS: Eleven rats were perfusion-fixed with either 4% PF or a combination of 2.5% GL and 4% PF. Diffusion-weighted imaging of the ex vivo spinal cord was performed using a 9.4T magnet with b values up to 3100 s/mm(2). In-plane resolution was 39 mum x 39 mum, and section thickness was 500 mum. RESULTS: Overall, animals fixed with a combination of GL and PF (GL-PF) showed a greater increase in longitudinal ADC (lADC) as compared to those fixed with PF only, without differences in transverse ADC (tADC). As a consequence of the increased lADC, overall anisotropic diffusion increased in those animals fixed with GL-PF, as measured with an anisotropy index (AI = tADC/lADC). Evaluation of specific tracts demonstrated that lADC for animals fixed with GL-PF were significantly elevated in the rubrospinal, vestibulospinal, and reticulospinal tracts as compared with animals fixed with PF only. CONCLUSION: Using a fixative of GL-PL results in increased anisotropy (decreased AI values) in spinal cord white matter tracts, as compared with PF fixation only, largely owing to increases in the lADC values. This finding may be due to better fixation of intra-axonal cytoskeletal proteins that results when GL is combined with PF and sheds further light on underlying sources of anisotropic water diffusion in CNS white matter.

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