We present a novel pipeline for robust optical analysis of fresh human brain tissue. We capture fluorescence signal and characterize optical properties with high sensitivity and high spectral resolution. These in turn allow for quantitative analysis of protoporphyrin IX (PpIX) accumulation in various types of tumor tissue. Our ex vivo protocol for tissue handling was designed to promote high-fidelity replication of in vivo conditions. The on-going consolidation of a fresh ex vivo quantitative dataset from a cohort of 20 patients plus a control cohort lays foundation for the development of imaging devices for intraoperative fluorescence guided resection.
Three major one layer tissue models (Modified Beer-Lambert,1 Jacques 1999,2 Pilon 20093) are compared to Monte Carlo simulated diffuse reflectance spectra and measured tissue phantom spectra with known ground truth. These ground truth values were obtained using inverse adding doubling and absorbance measurements and validated using a phantom with known ground truth (BioPixs). Finally, a two layer model (Pilon 2009) was evaluated against Monte Carlo simulations and used to analyse skin reflectance data (NIST4). These models were compared on goodness of fit and parameter extraction accuracy. It was found that the Pilon 2009 one layer model performed best against Monte Carlo simulations and phantom measurements, however the Pilon 2009 two layer model had significant regions of inaccuracy. These inaccurate regions correspond to circumstances where the epidermal layer has significant thickness and melanin content, while the dermal layer has low fraction of blood meaning that the haemoglobin impact is “masked”. The extraction of parameters from the NIST skin dataset using this model returns values that do not correspond well to literature values suggesting that many of these spectra lie within an inaccurate region or indicates oversimplification of the tissue modelling. This suggests both Pilon 2009 and Jacques 1999 are suitable for modelling tissue that can be approximated as a single, homogeneous, semi-infinite slab, however the Pilon 2009 two layer model is not yet effective when encountering empirical data.
A clinically-compatible imaging platform capable of performing widefield quantitative oxygenation and fluorescence imaging is presented with its potential for tissue status assessment in particular for blood perfusion and tumor margin assessment
Fluorescence-guided surgery give the surgeons extra input to improve the outcome of tumor resection procedures. However, the analysis of fluorescence images is qualitative and subjective inputs such as the surgeon’s perception and experience are considered when assessing the tumor margins. Objective indicators are needed to assess accurately the amount of fluorophore within the tissues. We developed a multimodal imaging platform capable of widefield quantitative fluorescence imaging for the use in a clinical environment. By mapping the fluorophore concentration, we offer an objective input for distinguishing healthy from diseased tissue and determining the resections margins in the optimal way: removing cancerous tissue while preserving healthy tissue and vital structures.
Despite the technological evolutions that transform the operating rooms nowadays, a major clinical need remains: surgeons need to distinguish healthy from diseased tissues while performing a procedure. Tissue status assessment procedures such as blood perfusion monitoring require objective input that can potentially be obtained with fluorescence imaging and oxygenation imaging. We developed a multimodal imaging platform for performing widefield quantitative oxygenation imaging and fluorescence imaging in a clinical environment. We demonstrate in-vivo the impact of widefield quantitative oxygenation imaging on blood perfusion assessment. Fluorescence imaging provided by the system is used in complement to confirm the outcome of oxygenation imaging.
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