Real-time spectrum quantification of tumor-related fluorescence during neurosurgery: A preliminary report

The fluorescent dye, 5-aminolevulinic acid (5-ALA), is currently applied for fluorescence-guided resections of high-grade gliomas. Present limitations of this technique are qualitative and subjective analyses, which show little of the background structures. This paper describes the intraoperative quantitative analysis of fluorescence intensity, hot-spot enhancement by frame averaging, and observation of surrounding structures by using 1000-nm lighting in real time.

A sample of diluted protoporphyrin IX (PpIX) in a bottle and 37 samples from nine patients with brain lesions were involved in this study. In this preliminary study, we determined appropriate conditions for image averaging and filters and selected the most sensitive spectrometer. In addition, we utilized a 1000-nm lighting system to visualize surrounding structures with no interference from PpIX fluorescence.

The novel system permitted the real-time quantitative analysis of PpIX fluorescence in operative fields by illuminating structures with 1000-nm-lighting. The real-time quantification provided subjective evaluations for surgical decision-making. We found good correlations between the fluorescence and PpIX contents in brain tissue. Furthermore, 1000-nm lighting visualized the anatomical structures and PpIX fluorescence simultaneously.

The combination of spectroscopy and a 1000-nm lighting system could enable surgeons to create a spectrogram of targets of interest while observing background structures. The spectrometer that we selected is highly sensitive to PpIX fluorescence and enables us to perform intraoperative real-time tissue mapping. By using a real-time system, we can perform quantitative and objective evaluations to achieve maximal tumor resection.