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. Author manuscript; available in PMC: 2017 Nov 1.
Published in final edited form as: Neuroimaging Clin N Am. 2016 Sep 2;26(4):601–620. doi: 10.1016/j.nic.2016.06.008

Figure 18.

Figure 18

Differentiating recurrent metastatic disease from the effects of stereotactic radiation therapy. Distinguishing progression of metastatic disease in patients who have previously undergone stereotactic radiation therapy can be markedly challenging as the effects of radiation therapy can have nearly identical morphological appearance on contrast-enhanced MR imaging. DSC perfusion MR imaging has been shown to help in this diagnostic dilemma. Lesion wide analysis of recurrent metastatic disease (A) tends to demonstrate elevated cerebral blood volume with reduced percentage of signal intensity recovery. Radiation necrosis (B) while appearing similarly as a progressively enhancing lesion tends to have normal to minimally elevated cerebral blood volume with near normal recovery metrics. Prior retrospective studies have suggested signal intensity recovery measurements are reliable to distinguish metastatic tumor recurrence from radiation necrosis with 96% sensitivity and 100% specificity.