Fluorescence guidance during stereotactic biopsy

Objective: When a stereotactic biopsy is taken to enable histopathological diagnosis of a suspected brain tumor, it is essential to i) do this safely, that is not injure a major blood vessel and ii) to obtain relevant vital material from the tumor. We are investigating the suitability of Indocyanine Green (ICG) fluorescence for blood vessel recognition and 5- Aminolevulinic acid (5-ALA) induced Protoporphyrin IX (PpIX) fluorescence for identification of proliferative brain tumor tissue. Methods: A fiber-optic endoscopic approach was studied to generate and detect both fluorescence signals. PpIX concentrations in brain tumors have been measured by chemical extraction. Preliminary equipment was studied in a mouse model. Results: PpIX-concentrations in glioblastoma tissue showed high inner- and inter-patient variability, but each patient out of 15 with interpretable data showed at least one sample with a PpIX-concentration exceeding 2.4 μmol/l, which is easily detectable by state-of-the-art fiberoptic fluorescence spectroscopy and imaging. The imaging fluoroscope with 30,000 pixels resolution could be introduced through a position controlled stereotactic needle. ICG-fluorescence from vessels with diameters ≥ 0.1 mm can be detected with a contrast of 2-2.5 against surrounding tissue. Conclusion: Fluorescence detection during stereotactic biopsy might increase safety and precision of the procedure significantly.