Video: Clinical evaluation of a laparoscopic hyperspectral imaging system

Abstract

Background: Hyperspectral imaging (HSI) during surgical procedures is a new method for perfusion quantification and tissue discrimination. Its use has been limited to open surgery due to large camera sizes, missing color video, or long acquisition times. A hand-held, laparoscopic hyperspectral camera has been developed now to overcome those disadvantages and evaluated clinically for the first time.

Methods: In a clinical evaluation study, gastrointestinal resectates of ten cancer patients were investigated using the laparoscopic hyperspectral camera. Reference data from corresponding anatomical regions were acquired with a clinically approved HSI system. An image registration process was executed that allowed for pixel-wise comparisons of spectral data and parameter images (StO₂: oxygen saturation of tissue, NIR PI: near-infrared perfusion index, OHI: organ hemoglobin index, TWI: tissue water index) provided by both camera systems. The mean absolute error (MAE) and root mean square error (RMSE) served for the quantitative evaluations. Spearman's rank correlation between factors related to the study design like the time of spectral white balancing and MAE, respectively RMSE, was calculated.

Results: The obtained mean MAEs between the TIVITA® Tissue and the laparoscopic hyperspectral system resulted in StO₂: 11% ± 7%, NIR PI: 14±3, OHI: 14± 5, and TWI: 10 ± 2. The mean RMSE between both systems was 0.1±0.03 from 500 to 750 nm and 0.15 ±0.06 from 750 to 1000 nm. Spearman's rank correlation coefficients showed no significant correlation between MAE or RMSE and influencing factors related to the study design.

Conclusion: Qualitatively, parameter images of the laparoscopic system corresponded to those of the system for open surgery. Quantitative deviations were attributed to technical differences rather than the study design. Limitations of the presented study are addressed in current large-scale in vivo trials.

Keywords: Clinical evaluation study; Gastrointestinal surgery; Hyperspectral imaging; Laparoscopic surgery; Minimally invasive surgery.

Fig. 1

Structure and composition of hyperspectral data and physiological parameters calculated thereof visualized as false-color images. StO₂ oxygen saturation of tissue, NIR PI near-infrared perfusion index, TWI tissue water index, OHI organ hemoglobin index (Color figure online)

Fig. 2

Technical comparison of the HSI systems for open (left) and minimally invasive surgery (right). Differences are highlighted in red. In the upper part, the relevant parts of both systems are shown at a glance beside the corresponding LED light source. Below, the structures of the hyperspectral cameras are illustrated schematically. The HSI MIS contains an additional beam splitter and a color image sensor to provide an RGB video in real-time (Color figure online)

Fig. 3

Mean absolute error (MAE) and standard deviation of the calculated tissue parameters for all records from the same (TvsT) and two TIVITA® Tissue systems (T1vsT2), the same HSI MIS system (LvsL), and the difference between both systems (TvsL) (Color figure online)

Fig. 4

Mean root mean square error (RMSE) and standard deviation for all records in the visible (500 to 750 nm) and near-infrared range (750 to 1000 nm) of the reflectance spectra measured with the same (TvsT) and two TIVITA® Tissue systems (T1vsT2), the same HSI MIS system (LvsL), and both systems (TvsL)