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SU‐FF‐I‐123: Clinical Value of Diffusion‐Weighted MRI in White Matter in Vivo
Author(s) -
Olariu E,
Cameron I
Publication year - 2009
Publication title -
medical physics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.473
H-Index - 180
eISSN - 2473-4209
pISSN - 0094-2405
DOI - 10.1118/1.3181244
Subject(s) - splenium , white matter , diffusion mri , nuclear magnetic resonance , magnetic resonance imaging , corpus callosum , diffusion , chemistry , nuclear medicine , relaxation (psychology) , effective diffusion coefficient , materials science , physics , medicine , anatomy , radiology , thermodynamics
The excellent soft tissue contrast of diffusion‐weighted magnetic resonance imaging, DW‐MRI has made it an invaluable technique especially in oncological assessment bringing hope in distinguishing between brain abscesses and necrotic and cystic neoplasms. However, a clear characterization of brain tumors and the associated pathologic structures is still a challenge. In this study, a tissue model is proposed to interpret the water diffusion behaviour in white matter based on the measured apparent diffusivities and their volume fractions. Measurements were performed on a 1.5T clinical scanner (Siemens). The protocol included: DTI measurements ( b =0 and 500s/mm 2 ), DW images (96 b‐values ranging from 0 to 10,000s/mm 2 with diffusion gradient rotated in the x‐z plane, NEX=6, TE=200ms) and 96‐echoes, non‐linearly sampled using T2‐sequence. All decay curves measured in the splenium agreed well with the assumed bi‐exponential function: S / S0 = f fast exp ( − b* ADC fast) + fslo exp ( − b * ADC slow ) . The fast water pool, ADC fast had a long apparent T 2 relaxation rate while the slow water pool, ADC slow had a shorter T 2 constant. The volume fraction f slow correlate with the volume fraction directly estimated from the T 2 spectrum. Markedly anisotropy was observed in ADC fast and f slow and more subtle in ADC slow . Evaluation of water diffusion in normal appearing corpus callosum is clearly assisting the peculiar properties of water in biological system, invoking long‐range hydration structures modulated by the concentration of lipid‐protein complexes in the membranes, cellular size and tissue architecture. ADC slow originate from the water in the hydration layers, as ADC fast the rest of the tissue bulk water. The membrane and associated hydration layers form a barrier to water diffusion perpendicular to them since diffusion within the hydration layers is anisotropic. This model is very sensitive to cellularity and further to a brain tumor grade; cell swelling and increased density of membranes enlarge f slow resulting in a decreased ADCs linked to cell proliferation.