Article
Integrated intraoperative imaging of glioblastoma using stimulated raman histology and 5-ALA mediated fluorescence
Integrierte intraoperative Bildgebung von Glioblastomgewebe mittels Stimulierter Raman Histologie und 5-ALA vermittelter Fluoreszenz
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Published: | May 25, 2022 |
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Objective: Intraoperative histological evaluations of CNS malignancies is challenging and limited to labour- and time-intensive neuropathological assessments. Integrated Stimulated Raman Histology (SRH) and 5-ALA mediated fluorescence imaging enables novel perspectives of interactive histo- and molecular feedback during brain tumor surgeries. Our investigations aimed to discover the heterogeneity of SRH-histomorphological pattern in glioblastoma correlated to 5-ALA mediated fluorescence signals to enable precise intraoperative interpretation of SRH.
Methods: 5-ALA mediated fluorescence and stimulated Raman scattering microscopy was performed on 50 glioblastoma specimens from 18 surgical resections and 5 stereotactic biopsies. All images with an input shape of [9000,9000,3] were randomly segregated into 1000 patches with the shape [160,160,3], resulting in a total of 50k patches. The data was then split 1:1 into training and validation data. A generative deep learning network architecture (variational autoencoder) was used to simplify the image information by learning to reconstruct the image based on a reduced information content (latent space). The reduced information was further clustered to uncover unique histomorphological patterns.
Results: Image reconstruction with Deep Learning showed the highest accuracy (F1 score 96.2 p<0.021) using a convolutional neural network embedded in a variational autoencoder (CNN-VAE). In a preliminary analysis, the clustering of the reduced image information yielded 6 clusters, with one cluster representing images with artifacts (5.43%). The other clusters reflected vascular proliferations (12.91%), high nuclear density (16.23%), large saturated fibers (19.43%), and small saturated fibers (20.36%) and nonsaturated fibers (25.64%). Integration of 5-ALA fluorescence revealed significantly enriched signal only in the clusters of saturated fibers. Samples obtained from the tumor periphery showed significant enrichment of the cluster of large saturated fibers (p=2.4e10-6).
Conclusion: Our analysis provides new insights into intraoperative analysis of combined SRS and 5-ALA fluorescence. We identified spatial heterogeneity of 5-ALA enrichment across different histopathological patterns in glioblastoma, suggesting that SRH may improve intraoperative diagnostics. The underlying pathophysiology of individual clusters, particularly saturated fiber bundles, a morphology absent in classical H&E staining, requires further investigation.