TABLE 4.

Perfusion MRI Features Differentiating True Early Progression of Glioblastoma and Pseudoprogression

Feature	True Early Progression	Pseudoprogression
Contrast enhancement	Yes	Yes
Time frame	Definition varies, but typically in the first 3–6 mo after completion of radiation therapy as part of chemoradiation with temozolomide for newly diagnosed high-grade glioma	Definition varies, but typically in the first 3–6 mo after completion of radiation therapy as part of chemoradiation with temozolomide for newly diagnosed high-grade glioma
Perfusion (rCBV)	Significantly greater than in pseudoprogression	Significantly less than in true early progression

Note—It is unclear how perfusion and permeability differentiate pseudoresponse from true response. In general, permeability and perfusion threshold values cannot be given because of differences in data acquisition and postprocessing and interpretation. Institutional techniques should be compared with particular studies described. rCBV = relative cerebral blood volume.