A study of the apparent diffusion coefficient of grey and white matter in human ischaemic stroke

Bastin, Mark E.; Rana, Arnab; Wardlaw, Joanna M.; Armitage, Paul A.; Keir, Sarah

doi:10.1097/00001756-200009110-00008

Cited by 16 publications

(10 citation statements)

References 3 publications

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“…Another study of patients during both hyperacute (12-24 h) and acute to subacute (24-72 h) phases of stroke found that both of these patient subgroups exhibited statistically similar declines in ADC av for WM and GM. 42 However, these investigators did find an earlier renormalization of GM lesions (in comparison to WM) as the infarct evolved (although the explanation for this result remains unclear), consistent with observations of other groups. 32 Given the inconsistent results obtained in a number of these recent investigations, it appears that additional studies are needed to better clarify the time course of WM and GM ADC changes during human stroke.…”

Section: Water Diffusion Changes In Human Strokesupporting

confidence: 79%

The role of diffusion tensor imaging in the evaluation of ischemic brain injury – a review

2002

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Water diffusion in brain tissue is affected by the presence of barriers to translational motion such as cell membranes and myelin fibers. The measured water apparent diffusion coefficient (ADC) value is therefore frequently anisotropic and varies depending upon the orientation of restricting barriers (such as white matter tracts) relative to the diffusion-sensitive-gradient direction. Anisotropic water diffusion can be specified using indices of diffusion anisotropy [e.g. standard deviation of the individual ADC values, fractional anisotropy (FA), lattice index (LI)], which are derived from measurements of the full diffusion tensor. The rotationally invariant nature of particular diffusion anisotropy indices (e.g. FA, LI) allows orientation-independent comparisons of these parameters between different subjects. Pathophysiological processes (such as cerebral ischemia) that modify the integrity of the tissue microstructure result in significant alterations in tissue anisotropy and make this metric a useful endpoint for characterizing the temporal evolution of the disease. Diffusion-tensor imaging (DTI) studies of both experimental and human stroke suggest that DTI may provide additional information about the evolution of the disease that is not available from diffusion-weighted MRI (DWI) alone. Acute reductions in the average diffusivity [ = ( 1 2 3 )/3 where 1 , 2 , and 3 are the eigenvalues of the diffusion tensor] following the onset of cerebral ischemia are often accompanied by increases in diffusion anisotropy. In the transition from acute to sub-acute and chronic stroke, renormalizes and subsequently increases whereas diffusion anisotropy measures (e.g. FA) decline and remained reduced in chronic infarcts. Overall isotropic ADC changes during infarct evolution have been observed to be greater in white matter (WM) than in gray matter (GM) lesions (although there have been conflicting reports on this issue) and GM lesions tend to renormalize prior to WM lesions as the infarct evolves. Ischemic WM exhibits a significant decrease in diffusion anisotropy (relative to normal WM) during ischemic evolution whereas that of ischemic GM remains statistically unchanged. Furthermore, the percentage decrease in ischemic WM is largely determined by reductions in 1 , the eigenvalue that coincides with the long axis of the WM fiber tract. Variations in unidirectional ADC or over the ischemic time course limit the usefulness of this parameter alone as a predictor of ischemic injury. Consequently, ADC information has been combined with that of other MR parameters (including DTI) to unambiguously stage and predict ischemic brain injury over its entire temporal evolution. Combined and diffusion anisotropy measurements have identified three phases of diffusion abnormality: (1) reduced and elevated anisotropy; (2) reduced and reduced anisotropy; and (3) elevated and reduced anisotropy. However, variations in the differential patterns of and diffusion anisotropy evolution have been obser...

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Section: Water Diffusion Changes In Human Strokesupporting

confidence: 79%

The role of diffusion tensor imaging in the evaluation of ischemic brain injury – a review

2002

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“…In contrast, the volume of abnormality can be more readily identified on diffusion-weighted images. The analysis typically ends up becoming a two-step process; first, a volume of abnormal tissue is identified in the DWI, and then the ADC values for that volume are analyzed (10,22,28).…”

Section: Discussionmentioning

confidence: 99%

“…The control is typically assumed to be a homologous region of tissue in the contra-lesional hemisphere. Results are then presented as the ratio of ipsito contra-lesional ADC values (10,22,28,29). While such an approach has proven scientifically fruitful, it significantly degrades the utility of a voxel-based measurement technique by executing the analysis on volumes of interest (VOIs) that are much larger than the original size of the image voxel.…”

Section: Discussionmentioning

confidence: 99%

Cerebral spinal fluid contamination of the measurement of the apparent diffusion coefficient of water in acute stroke

Latour

Warach

2002

Magnetic Resonance in Med

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“…Although ADC and perfusion thresholds have been identified that differentiate between penumbra and other tissue with modest degrees of accuracy, 7,14,15 there is no real difference in ADC thresholds of gray and white matter. 16 Despite lower CBF in white compared with gray matter based on PET studies, there is no evidence to suggest an MTT difference, and it seems reasonable to use an MTT delay of 4 seconds for both compartments. 7 Furthermore, because we used relative MTT values compared with each mirror contralateral voxel rather than absolute values, threshold differences between compartments are eliminated.…”

Section: Koga Et Al Evolution Of Diffusion-perfusion Mismatched Tissuementioning

confidence: 99%

The Existence and Evolution of Diffusion–Perfusion Mismatched Tissue in White and Gray Matter After Acute Stroke

Koga

Reutens

Wright

et al. 2005

Stroke

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Background and Purpose-Although white matter is a potential target of acute stroke therapy, there is uncertainty about its relative resistance to ischemia and whether it is capable of mounting a penumbral response. To explore these issues further, we examined the differential effects of ischemia on gray and white matter using magnetic resonance (MR) perfusion-diffusion mismatch after acute stroke. Methods-MR imaging studies were performed within 12 hours in patients with initial hemispheric ischemic stroke."At-risk" tissue was defined as tissue with abnormal diffusion-weighted imaging/perfusion-weight imaging or infarction on follow-up image. Tissue was segmented using a probabilistic atlas generated from age-matched controls. The proportions of "at-risk" tissue, which was penumbral at the time of imaging, were compared between gray and white matter. Results-Thirty-two patients had diffusion-perfusion mismatched penumbral tissue present in both gray and white matter compartments. Although the absolute mismatch volumes were greater in gray (median 42 cm 3 , interquartile range 18 to 70 cm 3 ) than in white matter (39 cm 3 , 17 to 49 cm 3 ; PϽ0.001), the proportion of "at-risk" tissue, which was penumbral at the time of imaging (median 3.7 hours, range 1.5 to 9.9 hours) was greater in white (69%, 49% to 86%) than gray matter (62%, 52% to 75%; Pϭ0.026). However, the proportions spontaneously salvaged by 3 months were similar in both compartments. Conclusions-These findings are consistent with white matter being able to mount an ischemic penumbral response in humans and being more resistant to cerebral ischemia than gray matter. They also raise the possibility that the therapeutic window is longer for white matter and may require alternative therapeutic strategies. (Stroke. 2005;36:2132-2137.)

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A study of the apparent diffusion coefficient of grey and white matter in human ischaemic stroke

Cited by 16 publications

References 3 publications

The role of diffusion tensor imaging in the evaluation of ischemic brain injury – a review

The role of diffusion tensor imaging in the evaluation of ischemic brain injury – a review

Cerebral spinal fluid contamination of the measurement of the apparent diffusion coefficient of water in acute stroke

The Existence and Evolution of Diffusion–Perfusion Mismatched Tissue in White and Gray Matter After Acute Stroke

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