Hyperspectral Imagery for Assessing Laser-Induced Thermal State Change in Liver

Abstract

This work presents the potential of hyperspectral imaging (HSI) to monitor the thermal outcome of laser ablation therapy used for minimally invasive tumor removal. Our main goal is the establishment of indicators of the thermal damage of living tissues, which can be used to assess the effect of the procedure. These indicators rely on the spectral variation of temperature-dependent tissue chromophores, i.e., oxyhemoglobin, deoxyhemoglobin, methemoglobin, and water. Laser treatment was performed at specific temperature thresholds (from 60 to 110 °C) on in-vivo animal liver and was assessed with a hyperspectral camera (500–995 nm) during and after the treatment. The indicators were extracted from the hyperspectral images after the following processing steps: the breathing motion compensation and the spectral and spatial filtering, the selection of spectral bands corresponding to specific tissue chromophores, and the analysis of the areas under the curves for each spectral band. Results show that properly combining spectral information related to deoxyhemoglobin, methemoglobin, lipids, and water allows for the segmenting of different zones of the laser-induced thermal damage. This preliminary investigation provides indicators for describing the thermal state of the liver, which can be employed in the future as clinical endpoints of the procedure outcome.

Thermal analysis of laser irradiation-gold nanorod combinations at 808 nm, 940 nm, 975 nm and 1064 nm wavelengths in breast cancer model

“…Starting from our results, future studies should investigate the optimization of the laser settings parameters to guarantee safe treatment margins [55,56], through the assessment also of the internal tumor temperature change during irradiation. Concerning the temperature monitoring approach utilized in the present study, thermographic imaging has been exploited thanks to its noninvasive nature and the possibility of accurate and real-time monitoring, which make it an excellent solution for the evaluation of the attained superficial temperature.…”

Intraoperative Guidance Using Hyperspectral Imaging: A Review for Surgeons

“…Using an open surgical set-up, researchers performed hepatic laser thermal ablations in an in vivo porcine model and by analyzing the liver's surface with HSI, they assessed a 40% increase in the spectral curves of the ablated tissue at the methemoglobin peak [35]. In a further study with a similar set-up, researchers monitored the hepatic thermal ablation with HSI and an infrared thermal camera simultaneously [36]. Subsequently, the spectral integrals corresponding to thermal-sensitive chromophores were extracted, and preliminary indicators of the thermal damage were proposed, successfully correlating to the thermal information (Figure 2F).…”

Prediction of In Vivo Laser-Induced Thermal Damage with Hyperspectral Imaging Using Deep Learning

“…Therefore, optical technology is a promising tool for achieving safe ablation margins [ 26 , 27 ]. Among the optical approaches, hyperspectral imaging (HSI) recently gained importance in image-guided surgery [ 28 , 29 ] and in the ablative therapy field [ 30 , 31 , 32 ]. HSI provides a discrete three-dimensional image with two spatial dimensions (x,y) coupled with a third dimension (z), which gives the relative reflectance of each pixel of the image within a narrow spectral band, forming a hypercube.…”