Towards intraoperative identification of colorectal carcinoma using diffise reflectance spectroscopy : a comparison of in vivo and ex vivo measurements

A few years ago, a promising optical device was created that could aid in the intraoperative localization of tumor tissue. Its discriminatory capacity for colorectal cancer tissue was investigated at the NKI-AVL. Measurements on healthy and malignant tissue were performed in and ex vivo. It was proposed to continue with only ex vivo measurements. Advantages of this approach were an increased reproducibility between measurements, easier inclusion and planning, and no need to interfere with the surgical procedure. The aim of this investigation was to validate whether the ex vivo measurements are comparable to in vivo measurements. A literature study showed that there is no clear consensus on the exact differences between in and ex vivo optical measurements (of colorectal tissues). From our statistical analysis and comparison of spectra, significant differences were found in the ex vivo measurements compared to in vivo measurements. These were mainly attributed to the loss of blood and water. The effects of these changes could be minimized if only the near-infrared (NIR) part of the spectrum is used. The fat parameters were uninfluenced in ex vivo measurements. It is therefore recommended to focus on fat and water dependent parameters obtained from NIR spectra.