|Vol. 4, Issue 2, Article 1||Saleem, S.|
Diffusion-weighted imaging (DWI) can detect changes in water diffusion associated with cellular dysfunction. It has been well documented that DWI can differentiate between cytotoxic edema and vasogenic edema, whereas conventional MRI cannot (47).
Acute parenchymal NBD lesions are associated with vasogenic edema as a reflection of the inflammatory process (32, 48); they appear isointense (49) or slightly hyper-intense on b=1000 s/mm2 DW images (48, 50) (Fig 23). Chronic parenchymal NBD lesions appear isointense too (51). Parenchymal NBD lesions, show increased diffusion (52).
On the other hand, acute infarcts associated with cytotoxic edema characterized by restricted diffusion (reduced ADC), are displayed as high signal on DW (b=1000 s/mm2) image (53).Venous infarct in association with sinus occlusion in NBD shows extensive hyper intensity on T2- and diffusion-weighted images as well as reduction of ADC values (Fig 24) (43).
However, heterogeneous signal intensities of venous infarcts on DWI are common. This pattern most likely represents hemorrhage or vasogenic edema in association with cytotoxic edema (Fig 25) (54).
As increased diffusivity in both acute and chronic phase in parenchymal NBD is different from the restricted pattern in ischaemic infarcts, DWI might be helpful for differentiating between these conditions. DWI is now considered a routine study in suspected NBD cases (52).
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