Chapter 10 Diffuse reflectance spectroscopy was studied for tissue differentiation as basis for a feedback system to enhance nerve preservation in oral and maxillofacial surgery20, but not yet for other anatomical structures such as parathyroid or thyroid tissue. Nachabé et al.21,22 showed the benefit of extending visualization up to a wavelength of 1600 nm, providing additional information regarding tissue concentrations of the biological chromophores water and lipid. The present translational study is a first fiber‐optic spectrometric exploration with the ultimate long‐term goal of obtaining parathyroid gland‐specific image enhancement. In vivo, wide band (350 – 1830 nm) diffuse reflectance spectra of human thyroid, parathyroid and surrounding adipose tissue were collected and assessed for the presence of endogenous contrasts that might enable future tissue‐specific contrast enhancement. Therefore we applied tissue classification using spectral features that are largely independent to signal intensity using a previously reported approach23. Methods All in vivo data acquisition was performed at the Surgery Department of Maastricht University Medical Center (MUMC, Maastricht, The Netherlands) during thyroid and parathyroid surgery (surgeon N.D.B.). 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. The cross‐over point between these sensors is at 1000 nm. The fibre probe is the medium to transport light from source to tissue, and to transport reflected light from tissue to spectrometer. The system was installed on a compact trolley to facilitate in vivo tissue data acquisition during routine surgery. The setup was tested and approved according to the essential requirements of IEC 60601‐1 to assure patient safety. The equipment has previously been described in more detail24. 148
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