Incident Dark-Field (IDF) Illumination Microscopy as a Novel Tool for Real-Time, Dye-Free Parathyroid Perfusion Assessment in Thyroid Surgery.

Background: Postsurgical hypoparathyroidism is a frequent complication in thyroid surgery. Visual inspection to assess parathyroid gland (PG) viability is subjective and inconsistent. Although indocyanine green (ICG) angiography can improve perfusion assessment, it introduces workflow disruptions and carries a risk of allergic reactions.

Methods: This pilot study investigated the feasibility of incident dark-field (IDF) microscopy as a dye-free, real-time imaging method for assessing PG perfusion during thyroidectomy. Thyroidectomy patients were prospectively enrolled at a tertiary referral hospital. Parathyroid glands were visually identified and confirmed with near-infrared autofluorescence (NIRAF). Imaging was recorded using three techniques: gross inspection (GI), IDF microscopy, and ICG angiography. Perfusion status was evaluated and classified into three categories (devascularized, compromised, and well-vascularized) and reviewed by three independent, blinded observers. Statistical analyses included interobserver reliability and inter-evaluation correlation assessments.

Results: Among 41 NIRAF-confirmed PGs, IDF microscopy demonstrated rapid assessment, requiring 2.41 ± 1.01 min per PG evaluation compared with 5.40 ± 1.53 min for ICG angiography. For PG viability evaluation, IDF showed higher correlation with ICG than GI (weighted kappa, 0.75 vs 0.60; both P < 0.001). Surpassing GI's moderate agreement (weighted kappa, 0.44-0.47; P < 0.001), IDF microscopy exhibited moderate to substantial inter-evaluation agreement (weighted kappa 0.51-0.66; P < 0.001).

Conclusions: Incident dark-field microscopy offers a rapid, reliable, and dye-free method for real-time assessment of PG perfusion, demonstrating diagnostic performance on par with ICG angiography while providing notable workflow advantages. This technique has the potential to reduce hypoparathyroidism by enhancing PG preservation in thyroid surgery. Further studies are needed to validate these findings and refine quantification methods.