The aim of the study is to evaluate the effectiveness of autofluorescence in the intraoperative preservation of parathyroids during total thyroidectomy with central lymph node compartment dissection.

Real-time intraoperative identification and functional maintenance of structures are of major importance in endocrine surgery, with a critical role in clinical outcomes and patients' quality of life. Despite the advances in preoperative imaging techniques, there is still need for precise intraoperative visualizing [1]. Limitations of naked eye inspection and subjectivity of palpation are imposing challenges even for the most experienced surgeons [1-3]. Nowadays, attention is attracted to intraoperative imaging techniques using Near Infrared Fluorescence (NIRF) with endogenous or exogenous contrast agents. These imaging techniques are attractive in biomedicine due to its high penetration depth and low scattering in human tissue [2].

Autofluorescence is the ability of several natural substances or drugs to be fluorescent after the absorbance of light or radiation. It has been already proved that parathyroid glands emit their own light after near-infrared (NIR) around 820nm , providing high contrast to the surrounding tissues. This made near-infrared autofluorescence a potential useful tool in hands of experienced endocrine surgeons in order to distinguish parathyroid glands from other anatomic structures during thyroidectomies.

Approximately 7.6% of thyroid surgeries resulted in hypoparathyroidism, with 75% of these cases being transient and 25% being chronic. The mechanisms that underlie hypoPTH are related to disruption of parathyroid arterial supply or venous drainage, mechanical injury, thermal or electrical injury, and either intentional or inadvertent partial or complete removal.

The aim of the present study is to evaluate the value of intra-operative autofluorescence imaging concerning the unintentional excision rate of parathyroids during total thyroidectomy with central lymph node compartment dissection. Moreover, we are going to evaluate correlation of autofluorescence with 24 hours post-operative PTH.

Inclusion Criteria:

1. Patient is over 18 years old
2. Patient scheduled for a non-emergency operation
3. Patient eligible for total thyroidectomy

Exclusion Criteria:

1. Patient is participating in another clinical trial which may affect this study's outcomes
2. Prior operation in the neck
3. Primary or secondary hyperparathyroidism
4. Vitamin D deficiency
5. Use of drugs that influences calcium metabolism (Vitamin D analogues, oral calcium supplements, bisphosphonates, teriparatide, thiazide diuretics, aromatase inhibitors)

Our sample size of 180 patients has been calculated after power analysis regarding other similar studies with an a=0.05 and Power=0.95.