Parathyroid differentiation during thyroid and parathyroid surgery by spectroscopy 147 Introduction To perform safe and efficient thyroid and parathyroid surgery, a high level of surgical skills is required together with understanding of natural variations in head and neck anatomy (e.g. thyroid, parathyroid, lymph nodes, and recurrent laryngeal nerves). Especially detecting the small sized parathyroid glands and performing re‐operative thyroid surgery can be challenging and time consuming. This visual task can be even more challenging due to anatomical variations in location, especially for the lower parathyroid glands1. During these complicated surgical procedures iatrogenic injury to the parathyroid glands may occur2. In a retrospective analysis of 5104 primary and 685 secondary thyroidectomies, temporary hypocalcaemia associated with hypo‐parathyroidism occurred in respectively 7.1% and 5% of cases (permanent in 1.8% and 2.5%). The rate of permanent complications was found to be significantly higher in re‐operative surgery3. Intraoperative identification of parathyroid glands before removal of the thyroid gland is of great importance to prevent these complications. Therefore, a tool for improved intraoperative parathyroid gland detection is desirable. Exploring the capabilities of spectroscopy beyond the limitations of the human eye offers a possible roadmap towards such a tool. Several innovative optical techniques have been under investigation for their potential in differentiating benign from malignant cells in thyroid and parathyroid specimens: multispectral image analysis4,5, Raman spectroscopy6 and elastic scattering spectroscopy7. Fluorescence imaging after peripheral infusion of aminolevulinic acid8,9 or methylene blue10 can be used for intraoperative detection of parathyroid adenomas. Near‐infrared auto‐fluorescence incorporates potential for real‐time parathyroid tissue localization as well11. Furthermore, optical coherence tomography is reported as a tool for parathyroid gland identification12,13. For color vision, the human eye contains only blue, green and red cones, which also partly overlap in sensitivity (poor channel separation). Yet, the trained human eye can discern quite subtle color differences within the visible range (400 – 780 nm). Hyperspectral cameras discern a multitude of well‐separated bands for each pixel, including the near‐infrared which is (by definition) invisible to the human eye, incorporating potential to facilitate image‐guided surgery14. It has, for example, been investigated for noninvasive intraoperative assessment of tissue oxygen saturation15,16, for intraoperative enhancement of anatomical structures17,18 and for intraoperative tumor detection19. Medical hyperspectral imaging‐systems typically use silicon (Si) or indium gallium arsenide (InGaAs) camera chips. The wavelength range of 400 ‐ 1000 nm is covered by Si, whereas InGaAs is typically sensitive in the 900 – 1700 nm wavelength region (and depending on chip composition even up to 2500 nm)14.
proefschrift_Schols_SLV
To see the actual publication please follow the link above