Diagnostic potential of laser-induced autofluorescence emission in brain tissue

Abstract

Laser-induced autofluorescence measurement of the brain was performed to assess its spectroscopic properties and to distinguish brain tumors from the normal tissues. The excitation-induced emission spectra were plotted on a 2-dimensional map, the excitation-emission matrix, to determine the excitation wavelengths most sensitive for the spectroscopic identification of brain tumors. The excitation-emission matrices of various types of human brain tumors and normal brain samples lead to the selection of three fluorescence peaks at 470, 520, and 630 nm, corresponding excitation light at 360, 440, and 490 nm, respectively for comparing the autofluorescence signatures of brain tissue. The fluorophores most likely related to each of these peaks are NAD(P)H, various flavins, and porphyrins, respectively. In vivo studies of rat gliomas showed that "NAD(P)H", "flavin", and "porphyrin" fluorescence were lower in gliomas than in normal brain. This finding suggests that there are certain relationship between brain tissue autofluorescence intensity and metabolic activity. In vitro human normal brain tissue fluorescence signals were lower in gray matter than in white matter and "NAD(P)H" fluorescence were lower in all measured human brain tumors than in normal brain. "Flavin" and "porphyrin" fluorescence in the neoplastic tissues was lower or higher than normal tissue depending on their nature. In conclusion, the fluorescence spectroscopic diagnostic system might be able to distinguish brain tumors from the normal brain tissue. The results of this study need to be verified and the investigation extended to human brain tumors in the operating room.

405 nm versus 633 nm for protoporphyrin IX excitation in fluorescence‐guided stereotactic biopsy of brain tumors

“…Additionally, a broad and characteristic emission spectrum is induced, allowing the extraction of valuable spectral information. [46,47] Moreover, the use of a 405 nm light source also leads to the excitation of tissue autofluorescence, which could be used as an additional parameter for tissue discrimination [48][49][50] or serve as reference for the normalization of PpIX signals [27].…”

Review of the potential of optical technologies for cancer diagnosis in neurosurgery: a step toward intraoperative neurophotonics

“…It could be a more effective tool for optical biopsy because not only does the contrast from different fluorescence lifetimes result from changes of cellular or tissue environment, but also these changes are independent of fluorescent signal intensity, irregular brain surfaces, tissue illumination, blood, and fluorophore quantum yield. 61,66 Time-resolved fluorescence measurement can also differentiate the fluorescence components of overlapping emission spectra, providing the ability to detect variations in pH and temperature. 59,67 However, time-resolved fluorescence measurements (either spectroscopic or imaging) require more complex equipment, including more sophisticated lasers, high-speed detectors, and electronics that function in the picosecond range.…”

“…An autofluorescence study in a rat glioma model was presented by Chung et al 61 and it showed that there are relationships between brain tissue autofluorescence intensity and metabolic activity. For instance, fluorescence signals were lower in gliomas than in normal brain tissue, and flavin and porphyrin fluorescence in neoplastic tissues was different from that of normal tissue.…”

Review of Neurosurgical Fluorescence Imaging Systems for Clinical Application

“…Most studies in 5-ALA-guided neurosurgery have been performed using fluorescence microscopy [35][36][37][38].…”