Loupe-Based Intraoperative Fluorescence Imaging

Glioblastoma multiforme (GBM) and anaplastic astrocytoma (AA) are the most common primary malignant brain tumors. Survival of patients with these brain tumors is directly related to the extent of resection. Consequently, a great deal of effort has been directed at developing techniques and technologies that allow more extensive, safe resections. This study will test a loupe-based wearable device in the clinical setting and compare its accuracy with a large operative microscope to identify tumor tissues. Postoperative histopathological analysis on tumor tissues will be used as gold standards for comparison. The outcome from this study will be a low-cost, miniaturized, easy-to-operate, loupe-based fluorescence imaging device for intraoperative guidance of brain tumor resection with the same level of accuracy as the large microscope.

This is a prospective, observational study to compare the measurement accuracies of a wearable loupe-based device and the large microscope against the gold standards of postoperative histopathological analysis on tumor tissues. At the induction of anesthesia, patients will receive 5 mg/kg of intravenous sodium 5-aminolevulinic acid (5-ALA) or fluorescein. Surgery will be performed under the guidance of the operative fluorescence microscope (PENTERO with fluorescence kit + YELLOW 560, Carl Zeiss) or (PENTERO 900 + BLUE 400, Carl Zeiss). The operating room light will be dimmed for optimum reproduction of the fluorescent light. Tumor removal will be continued until no fluorescent area is visualized. To evaluate the accuracy of the device in the identification of tumor tissue, six samples will be biopsied from the tumor resection margin for each patient; three in the fluorescent area and three in the non-fluorescent area for the assessment of positive and negative predictive values of the devices, respectively. These biopsied tissues will be taken to the clinical pathology laboratory for the standard histological analysis. To compare the accuracy of the two imaging systems in identifying tumor tissues, the tumor resection area will be visually observed by the surgeon and video recorded using the new loupe-based device at two time points (at least): immediately before and immediately after tumor removal. Additional fluorescence images may be taken during surgery as long as the surgical workflow is not impacted. Moreover, the four fresh biopsies (2 in the fluorescent area and 2 in the non-fluorescent area) taken from the tumor margin based on the operative microscope diagnosis will also be examined intraoperatively by the loupe-based device to determine whether they are fluorescent or non-fluorescent. To discriminate between clear tumor tissue and the peritumoral areas, the postoperative histological analysis of the biopsied samples taken from the tumor margins will be classified on the basis of the current 2016 WHO classification. The neuropathologist will be blinded to the fluorescence characteristics of the biopsied samples.