Optical Signature Analysis of Liver Ablation Stages Exploiting Spatio-Spectral Imaging

Background and Objective:  Thermal ablation modalities such as Radiofrequency ablation (RFA) / Microwave ablation (MWA) are deliberately used for marginally invasive tumor removal by escalating tissue temperature. For precise tumor extinguish, thermal ablation outcomes need routine monitoring for tissue necrosis in a challenging research task. The study aims to exploit hyperspectral imaging (HSI) to evaluate the impact of the liver tissue ablation.  Materials and Methods : RFA with temperature range (≥80 °C) was accomplished on the  ex vivo  animal liver and evaluated using a spectral camera (400~1000 nm). The spectral signatures were extracted from the HSI data after the following processing steps: capturing three spectral data cubes for each liver sample with total 7-samples (before ablation, after ablation, and after ablation with sample slicing) using an HSI optical configuration. The custom HSI processing comprises “Top-hat and Bottom-hat transform” combined with “watershed transform” image segmentation to increase the intensity for a region of interest (ROI) of the investigated tissue, linking spectral and spatial data. Additionally, statistical analysis for HSI data was performed to exclusively select the best spectral band that discriminates between the normal, thermally-damaged, and ablated liver regions.  Results:  The variation of the optical parameters for the investigated liver samples provides variable interaction with the light diffuse reflection ( Ŗ d ) over the spectrum range (400~1000 nm). Where, the extracting spectral information of the various tissue zones from the induced RFA linked to the hemoglobin, methemoglobin, and water permits variations. The generated spectral image after image enhancement utilizing “Top-hat and Bottom-hat transform” followed by “watershed segmentation”, showed high contrast between normal and thermal regions at a wavelength (600 nm). However, the wavelength (900 nm) shows a high variance between the normal and ablated regions. Finally, delineation of the thermal and ablated regions on the complemented enhanced image.  Conclusion : HSI is considered a promising optical noninvasive technique for monitoring the RFA toward enhancing the ablation-based treatment for liver tumor outcomes.