Beschreibung:
<jats:title>Abstract</jats:title>
<jats:p>Optical coherence tomography (OCT) is an imaging modality based on the inherent backscattering of light within different tissue types. OCT was introduced in the early 1990s and has since become a standard diagnostic tool in ophthalmology. Images can be acquired non-destructively, in real time and three dimensions at micrometer resolution. Only recently, OCT has been increasingly recognized in other fields such as neuroimaging. Here we present a multimodal imaging approach using a custom-built visible light optical coherence microscope (OCM) combined with a fluorescence imaging mode for the evaluation of different tumor compartments in glioblastoma (GB) samples retrieved during 5-aminolevulinic acid (5-ALA) fluorescence-guided surgery. 18 biopsies of ten GB patients were imaged using the visible light OCM system, providing the three-dimensional morphologic structure of the tissue on a cellular level (axial resolution in brain tissue 0.88 µm, penetration depth 100 µm). Attenuation coefficients, i.e., indicators for light penetration and scattering, were calculated for each sample. Tumor-specific contrast enhanced by 5-ALA was evaluated in co-registered images from the fluorescence channel. Samples were ultimately processed for histopathologic work-up and compared to OCM findings. Three different groups of biopsies could be defined based on quantitative 5-ALA fluorescence [normalized between 0 and 1], attenuation [mm-1] and histological H&E stainings: tumor core (n=8; fluorescence [median ± standard deviation]=0.72±0.13, attenuation [median ± standard deviation]=3.9±0.66), infiltration zone (n=6; fluorescence=0.5±0.19, attenuation=4.4±0.5), and adjacent brain parenchyma (n=4; fluorescence=0.3±0.12, attenuation=5.0±0.79). Concurrent increase in fluorescence intensity and cell density was significantly associated with tissue malignancy (tumor core: 3849±1028 nuclei/mm²; brain parenchyma: 1364±236 nuclei/mm². p=0.024). Furthermore, a negative correlation between fluorescence and attenuation coefficient was detected (r=0.51, p=0.032). Aforementioned results suggest that this multimodal imaging setup is a promising approach for non-destructively investigating the three-dimensional morphologic structure at microscopic resolution whilst at the same time leveraging tumor-specific contrast through 5-ALA fluorescence.</jats:p>