Figure 2.

Characteristic fluorescence patterns of the tumor and peritumoral brain tissue in two patients with surgery of a brain metastasis after preoperative 5-ALA administration. (A) The brain metastasis of the first patient in the right occipital lobe demonstrates a cystic pattern of contrast-enhancement on T1-weighted MR images and (B) shows a distinct peritumoral edema on T2-weighted images. (C) After dura opening, the tumor is visible under conventional white-light microscopy and (D) demonstrates strong 5-ALA fluorescence under violet-blue excitation light. (E) Although the brain metastasis was completely removed under white-light microscopy, (F) visible fluorescence is detected in the peritumoral brain tissue. (G) The brain metastasis of the second patient in the left frontal lobe is characterized by heterogenous contrast-enhancement on T1-weighted images (H) with an extensive peritumoral edema. (I) During surgery, the brain metastasis is visible under conventional white-light microscopy, (J) but no visible fluorescence is detected under violet-blue excitation light. (K) After complete removal of the brain metastasis under white-light microscopy, (L) visible fluorescence is found in the peritumoral brain tissue although the brain metastasis itself did not reveal any visible fluorescence.