Difuse optical reflectance spectrometry in thyroid and parathyroid surgery (abstract only)

INTRODUCTION: In thyroid and parathyroid surgery iatrogenic injury of the parathyroid glands or the recurrent laryngeal nerve (RLN) is a possible complication that needs to be prevented. The visible contrast between thyroid and parathyroid tissue is delicate to observe. The aim of this pilot study was to collect in vivo spectral reflectance-signatures of critical tissue types encountered during thyroid and parathyroid surgery, and to assess the presence of useful spectral distinctive features that might be applied for future devices enabling intraoperative tissue-specific image contrast enhancement.
METHODS: Wide-band spectra (350-1830nm, 1nm resolution) were collected in vivo during thyroid and parathyroid surgery. Subjected to tissue type accessibility, on average 2 tissue types per patient were measured. For each tissue type, 5 spectra were recorded per site, covering 1-2 sites per tissue type. Mean tissue spectra were calculated for all measured tissue types. After visually comparing these mean spectra, two spectral signature features for all individual measured sites were extracted: 1. Slope within the 650-700nm range; 2. Amplitude gradient between dominant local reflectance minimum and maximum within 1350-1830nm.
RESULTS: In 10 consecutive patients 158 in vivo spectra were recorded on 32 tissue sites. Based on the mean diffuse reflectance spectra for thyroid, parathyroid and RLN, the estimated features for the three tissue types were plotted. Significance was tested using a paired Student's t-test and by applying a Holm-Bonferoni correction (criterion set to p<0.025). Regarding feature 1 significance was found for parathyroid (p=0.003) and RLN (p=0.006). With respect to feature 2 RLN was significant (p=0.001). Both investigated spectral features seem to offer added value to distinguish between the studied tissue types.
CONCLUSION: To our knowledge, this study is the first to date to investigate in vivo spectral reflectance-signatures of critical tissues encountered during parathyroid and thyroid surgery, far beyond the spectral detection boundary of the human eye (i.e. the infrared light spectrum). Within the recorded spectral reflectance-signatures we identified two spectral features which may be used for further developments towards intraoperative image contrast enhancement and thereby facilitate differentiation of tissue structures, either during open or endoscopic surgery.