Hyperspectral imaging for thermal effect monitoring in in vivo liver during laser ablation

Abstract

Thermal ablation is a minimally invasive technique used to induce a controlled necrosis of malignant cells by increasing the temperature in localized areas. This procedure needs an accurate and real-time monitoring of thermal effects to evaluate and control treatment outcome. In this work, a hyperspectral imaging (HSI) technique is proposed as a new and non-invasive method to monitor ablative therapy. HSI provides images of the target object in several spectral bands, hence the reflectance/absorbance spectrum for each pixel. This paper presents a preliminary and original HSI-based analysis of the thermal state in the in vivo porcine liver undergoing laser ablation. In order to compare the spectral response between treated and untreated areas of the organ, proper Regions of Interest (ROIs) were chosen on the hyperspectral images; for each ROI, the absorbance variation for the selected wavelengths (i.e., 630, 760, and 960nm, for deoxyhemoglobin, methemoglobin, and water respectively) was assessed. Results obtained during and after laser ablation show that the absorbance of the methemoglobin peaks increases up to 40% in the burned region with respect to the non-ablated one. Conversely, the relative change of deoxyhemoglobin and water peaks is less marked. Based on these results, absorbance threshold values were retrieved and used to visualize the ablation zone on the images. This preliminary analysis suggests that a combination of the absorbance information is essential to achieve a more accurate identification of the ablation region. The results encourage further studies on the correlation between thermal effects and the spectral response of biological tissues undergoing thermal ablation, for final clinical use.

Hyperspectral image-based analysis of thermal damage in living liver undergoing laser ablation

“…Indeed, spectral responses above those temperatures suggest a plateau phase possibly caused by tissue carbonization. The main shape variations, especially occurring after exceeding temperature thresholds involve the following: (i) smoothing of the HbO2 double peak; (ii) MetHb peak formation and increasing (iii) Hb peak consistent variation, (iv) shape and sign changes for H2O wavelength range [16]. Spectra evolution during and after the ablation procedure was also reported in Fig.…”

“…Absorbance spectra acquired during in vivo liver ablation in one test for three ROI dimensions(16, 77, and 170 pixels area).…”

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

“…Tissue chromophores such as oxyhemoglobin (HbO 2 ), deoxyhemoglobin (Hb), and water (H 2 O) [ 19 ] are sensitive to the temperature of the environment, thus monitoring their spectral variation has the potential to be the basis for design a therapeutic supportive-tool, which can indicate the thermal tissue state [ 20 , 21 ]. In this scenario, hyperspectral imaging (HSI) holds the potentiality of combining spectral and spatial information of the thermal state of the tissue [ 22 , 23 , 24 , 25 ]. The use of HSI is rapidly increasing in the biomedical field, where HSI is devoted to “see the invisible” in several diagnostic and therapeutic applications [ 26 , 27 ].…”

Automated thermal imaging for the detection of fatty liver disease

“…Thermal image analysis was able to correlate liver thermography with liver viability in transplanted livers 12 , and identify liver fibrosis and steatosis when combined with chemical imaging techniques 13 or other advanced spectroscopy methods 14 . Several reports have also described the utility of thermal imaging in monitoring tissue damage during various liver ablation procedures [15][16][17] .…”