Chapter 8 imaging in the so‐called extended near‐infrared window (i.e. beyond the silicon detection range) based upon endogenous chromophores (e.g. water and lipid) has recently been described by Cao et al.23. Using a mouse model spectral characterization of various tissues (skeletal muscle, liver, kidney, cardiac tissue, cerebrum, cerebellum and adipose tissue) was obtained. Diffuse reflectance spectroscopy (DRS) has been used previously to acquire spectral characteristics of different tissue types in order to discriminate between e.g. normal, premalignant and malignant colonic tissue24,25. The present in vivo human study follows‐up on our previously reported study on freshly extirpated samples of colon, ureter and mesenteric adipose tissue by using wide‐band (350 – 1830 nm) DRS26. To evaluate the potential of hyperspectral imaging in colorectal surgery, we collected in vivo wide‐band (350 – 1830 nm) spectral reflectance‐signatures during colon surgery, i.e. of colon, mesenteric adipose tissue, muscle, artery, vein and ureter. The main focus of tissue spectral analysis was identifying endogenous contrasts of respectively ureter and artery versus surrounding adipose tissue. In contrast to earlier studies, which rely upon signal intensity to classify tissues using a support vector machine (SVM)22, we propose the exploration of spectral tissue signatures by extraction of relative spectral features from DRS signal which are quite robust with regard to variations in signal intensity27. Methods In vivo human tissue measurements were performed at the Surgery Department of Maastricht University Medical Center (MUMC, Maastricht, The Netherlands) during open colorectal surgery. Prior to measurements, the local institutional review board of Maastricht University Medical Center (registration number METC 10‐4‐035) granted approval and preoperative written informed consent was obtained from all patients. Material Diffuse reflectance spectra were acquired using custom developed sterile disposable optical fibre probes (TNO, Eindhoven the Netherlands & Light Guide Optics, Rheinbach Germany), a modified Xenon light source (D‐light C, Karl Storz, Tuttlingen Germany), and a spectrometer (Analytical Spectral Devices, Inc., Colorado USA) covering the range of 350 – 1830 nm. The spectrometer is equipped with two sensor technologies: a silicon (Si) based sensor and an indium gallium arsenide (InGaAs) based sensor with a cross‐over 110 point at 1000 nm. The fibre probe is the medium through which light is
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