Fig 12.

A, Postcontrast T1-weighted MR image in a patient with a new appearance of a contrast-enhancing lesion in a formerly radiotherapeutically treated fibrillary astrocytoma. From conventional imaging sequences, one cannot differentiate treatment-related blood-brain barrier breakdown and malignization of the tumor. B, rCBF perfusion parameter image shows a highly perfused lesion, which was suspicious and later histologically confirmed as a high-grade tumor nodule within the low-grade astrocytoma.