K-trans (MR perfusion)

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K is a measure of capillary permeability obtained using dynamic contrast-enhanced (DCE) MR perfusion. It is calculated by measuring the accumulation of gadolinium-based contrast agent in the extravascular-extracellular space.

Increased permeability of vessels in the brain is seen in a variety of conditions:

  • glioma: VEGF produced by the tumor reduces the effectiveness of gap junction and creates fenestrations in the endothelium of brain capillaries; this has been shown to correlate with tumor grade
  • cerebral metastases, which lack blood brain barrier and resemble the vascularity of the parent tissue
  • inflammatory lesions (e.g. demyelinating plaques of multiple sclerosis)

It should be noted that how k is interpreted varied according to permeability and blood flow. In situations where permeability is very low (near-intact blood brain barrier) then k is a useful measure of permeability, whereas in situations where permeability is very high (disrupted blood brain barrier) then k will reflect blood flow .

Extracranial usage