Real-time Brain Tumor imaging with endogenous fluorophores: a diagnosis proof-of-concept study on fresh human samples

Fanny Poulon,Marc Zanello,Fabrice Chretien,Baris Turak,Darine Abi Haidar,Johan Pallud,Edouard Dezamis,Bertrand Devaux,François Nataf,Pascale Varlet,Georges Abi-Lahoud

doi:10.1038/s41598-018-33134-2

Abstract

The primary line of therapy for high-grade brain tumor is surgical resection, however, identifying tumor margins in vivo remains a major challenge. Despite the progress in computer-assisted imaging techniques, biopsy analysis remains the standard diagnostic tool when it comes to delineating tumor margins. Our group aims to answer this challenge by exploiting optical imaging of endogenous fluorescence in order to provide a reliable and reproducible diagnosis close to neuropathology. In this study, we first establish the ability of two-photon microscopy (TPM) to discriminate normal brain tissue from glioblastomas and brain metastasis using the endogenous fluorescence response of fresh human brain sample. Two-photon fluorescence images were compared to gold standard neuropathology. “Blind” diagnosis realized by a neuropathologist on a group of TPM images show a good sensitivity, 100%, and specificity, 50% to discriminate non tumoral brain tissue versus glioblastoma or brain metastasis. Quantitative analysis on spectral and fluorescence lifetime measurements resulted in building a scoring system to discriminate brain tissue samples.

Highlights

Surgical resection aims to maximize tumor removal while minimizing morbidity for both primary and metastatic brain tumors[1,2]
We investigated two photon microscopy (TPM) autofluorescence signal analysis from the visible to the infrared domains, exploring all known endogenous molecules coming from freshly extracted brain tissue, including normal tissue, glioblastoma (GBM), and brain metastasis collected from adult patients
We evaluated: (1) the capacity of TPM in distinguishing between tumorous and normal tissue; (2) the correlation between the optical signatures extracted from TPM and the histopathological diagnosis derived from the gold standard, whereby we can evaluate the clinical relevance of TPM as a more robust intraoperative diagnosis modality, and (3) the predictive power of TPM imaging features in differentiating malignant gliomas from normal tissue as well as from brain metastasis

Summary

Introduction

Surgical resection aims to maximize tumor removal while minimizing morbidity for both primary and metastatic brain tumors[1,2]. Compared to other endomicroscopy techniques, such as confocal laser endoscope, TPM provides multiple advantages[13] such as (1) intrinsic sectioning up to 1 mm; (2) no out-of-focus photobleaching and photodamage; (3) localized phototoxicity and photobleaching; (4) deeper penetration into biological tissue when set side by side with confocal microscopy (up to 1 mm)[14], and (5) no spectral overlapping between excitation and emission signals To top it up, four different optical contrast mechanisms which are: (1) spectral analysis; (2) two photon Fluorescence Lifetime Imaging Microscopy (FLIM); (3) Second Harmonic Generation (SHG) imaging[15], and (4) Two Photon Excitation Fluorescence (TPEF), can be extracted with the use of TPM to provide complementary information for improved tissue characterization. We evaluated: (1) the capacity of TPM in distinguishing between tumorous and normal tissue; (2) the correlation between the optical signatures extracted from TPM and the histopathological diagnosis derived from the gold standard, whereby we can evaluate the clinical relevance of TPM as a more robust intraoperative diagnosis modality, and (3) the predictive power of TPM imaging features in differentiating malignant gliomas from normal tissue as well as from brain metastasis

Objectives

Methods

Results

Conclusion