Automated spectroscopic tissue classification in colorectal surgery transported from light source to tissue, and back again from tissue to spectrometer. The system was installed on a compact trolley to facilitate in vivo tissue measurements 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 detail26. Figure 8.1 shows the fibre probe tip composed of eight optical fibres: One central receiving fibre (400 um diameter, NA 0.22 ±0.02) and seven illuminating fibres (300 um diameter, NA 0.22 ±0.02). The rigid stainless steel probe tip has a 2 mm diameter and a length of 10 mm. The remaining length of the sterile fibre probe is highly flexible. In vivo data acquisition During open colorectal surgery, in vivo wide‐band diffuse reflectance spectra (350‐1830 nm, 1 nm spectral resolution) were collected. For each tissue type, five spectra per site (taking 30 seconds per site) were recorded, covering at least one site per tissue type (see also Table 8.1). The sterile fibre probe was handled by the surgeon and gently brought into direct contact with one of the designated tissues (see Figure 8.1). When blood was visibly present on the tissue surface, it was dapped away using sterile gauze. Between spectral measurements on different sites, the fibre probe tip was swiped with clean sterile gauze (wetted in saline). Acquired data was labeled according to the tissue type description of the attending surgeon. To correct for dark current16, the spectrometer was calibrated prior to in vivo data acquisition. After the completion of in vivo spectroscopy, a reference spectrum was acquired, for calibration purposes, by direct contact measurement on a white reference phantom (Optical‐grade spectralon reference; Labsphere, Inc., North Sutton, New Hampshire USA). The integration times of the Silicon and InGaAs sensor were individually optimized during the Spectralon calibration. No correction for ambient light was performed. 111
proefschrift_Schols_SLV
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