Abstract
.Significance: 5-Aminolevulinic acid (5-ALA)-based fluorescence guidance in conventional neurosurgical microscopes is limited to strongly fluorescent tumor tissue. Therefore, more sensitive, intrasurgical 5-ALA fluorescence visualization is needed.Aim: Macroscopic fluorescence lifetime imaging (FLIM) was performed ex vivo on 5-ALA-labeled human glioma tissue through a surgical microscope to evaluate its feasibility and to compare it to fluorescence intensity imaging.Approach: Frequency-domain FLIM was integrated into a surgical microscope, which enabled parallel wide-field white-light and fluorescence imaging. We first characterized our system and performed imaging of two samples of suspected low-grade glioma, which were compared to histopathology.Results: Our imaging system enabled macroscopic FLIM of a field of view at spatial resolutions . A frame of with a lifetime accuracy was obtained in 65 s. Compared to conventional fluorescence imaging, FLIM considerably highlighted areas with weak 5-ALA fluorescence, which was in good agreement with histopathology.Conclusions: Integration of macroscopic FLIM into a surgical microscope is feasible and a promising method for improved tumor delineation.
Highlights
In brain tumor therapy, the key factor for improved patient outcome is complete resection.[1]
Even though fluorescence-guided surgery using 5-aminolevulinic acid (5-ALA)-induced protoporphyrin IX (PpIX) allows the surgeon to locate malignant tissue, its use is mostly limited to high-grade tumors.[2]
Proposed in vivo methods rely on endoscopic platforms with limited field of view (FOV).[3]
Summary
The key factor for improved patient outcome is complete resection.[1]. Erkkilä et al.: Surgical microscope with integrated fluorescence lifetime imaging. More sensitive detection of PpIX fluorescence is limited among others by tissue autofluorescence. Spectrally resolved fluorescence imaging[3] has been proposed to detect nonvisible PpIX accumulations. It relies on the knowledge or parallel measurement of the optical tissue properties. This requires additional measurement channels making these devices more complex. Fluorescence lifetime imaging (FLIM) relies on the time delay between the excitation and subsequent fluorescence emission and is thereby intrinsically independent of any intensity variations due to altered scattering or absorption in the tissue.[4]
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