Intraoperative detection of malignant gliomas using 5-Aminolevulinic acid-induced protoporphyrin fluorescence, openMRI and real-time navigation system

It is generally accepted by neurosurgeons that the complete tumor resection is one of the factors to improve the prognosis of malignant glioma patient. However, the extensive resection remains controversial because the tumor margin is difficult to be distinguished from surrounding normal and/or edematous brain. It has been established that photosensitizer protoporphyrin IX (PpIX) induced by 5-Aminolevulinic acid (5-ALA) is used as a fluorescence detection marker for photodiagnosis of malignant gliomas. We tried to study whether or not the location of fluorescence detection using 5-ALA is compatible with image-guided tumor location and whether or not the fluoresce-positive tissue contained tumor cell by histological staining. Patients with malignant gliomas received oral doses of 5-ALA before anesthesia. During surgery, an MR image was scanned and registered for navigation system. Tumor fluorescence was visualized under Ultra-violet (UV) light illumination. The locations of fluorescence detection were confirmed by the real-time navigation. The marked fluorescing tissues were removed and used for following histological analysis. The locations of fluorescence detection were confirmed to be in agreement with Gd-enhanced region indicated by real-time navigation, whereas the area was macroscopically impossible to distinguish from the regions in which there was no radiological enhancement. Histological study showed that the tissues from fluorescence positive regions contained tumor cells.