This single-center, prospective, three-phase observational cohort quantifies the relationship between indocyanine green (ICG) fluorescence and early parathyroid function. Adult patients scheduled for unilateral thyroid lobectomy with autotransplantation of the ipsilateral inferior parathyroid gland are enrolled. After intravenous ICG 25 µg/kg, peak fluorescence of the superior parathyroid gland and the common carotid artery (CCA) is recorded at 60-120 seconds to calculate the ratio R = PTG/CCA. Serum parathyroid hormone (PTH) is measured 30 minutes post-operatively. A derivation cohort (\~120 patients) generates R-based thresholds for in-situ preservation versus autotransplantation, which are prospectively validated in an independent cohort (60 patients) together with decision-curve analysis of clinical net benefit.
Scheduled for unilateral thyroid lobectomy plus central (VI-level) lymph-node dissection.
Complete identification and in-situ preservation of the ipsilateral superior parathyroid gland;
Complete identification and autotransplantation of the ipsilateral inferior parathyroid gland.
Serum 25-hydroxy-vitamin D ≥ 30 ng/mL at baseline; patients below this level may be enrolled after standardized vitamin-D and calcium supplementation with re-test confirming ≥ 30 ng/mL.
Prior surgery on the thyroid or parathyroid glands.
Severe hepatic or renal impairment, or other serious metabolic bone disease.
Pregnancy or lactation.
Known hypersensitivity to indocyanine green or iodine-containing compounds.
Consecutive adult patients undergoing unilateral thyroid lobectomy with planned autotransplantation of the ipsilateral inferior parathyroid gland at a single tertiary endocrine-surgery center; recruitment limited to cases in which the superior parathyroid gland can be preserved in situ and evaluated intra-operatively with indocyanine-green fluorescence quantification.
Cohort
Retrospective
ntra-operative Indocyanine Green (ICG) Fluorescence Quantification
Diagnostic testAfter a single intravenous bolus of indocyanine green (25 µg/kg), a near-infrared sensor records raw fluorescence intensity from the superior parathyroid gland and the ipsilateral common carotid artery at 60-120 seconds. No images are stored; only peak intensity values are logged to calculate the perfusion ratio R = PTG / CCA. The measurement is observational, adds ≤2 minutes to operative time, and involves no therapeutic intent.
Parathyroid Gland Fluorescence Intensity
Peak fluorescence intensity of the ipsilateral superior parathyroid gland, captured 60 - 120 seconds after a single intravenous bolus of indocyanine green (25 µg/kg).
Common Carotid Artery (CCA) Fluorescence Intensity
Peak fluorescence intensity of the ipsilateral common carotid artery recorded in the same 60 - 120 second window; serves as the reference signal for perfusion ratio calculations.
Parathyroid Hormone (PTH) at 30 Minutes post-surgery
PTH concentration (pg/mL) measured by chemiluminescent assay 30 minutes after skin closure, reflecting immediate functional status of the preserved superior parathyroid gland.
Administered ICG Dose
Total dose of indocyanine green (µg/kg) delivered during the procedure.
PTH at 6 Hours
PTH concentration measured 6 hours after surgery.
PTH at 2 Weeks
PTH concentration measured 14 ± 2 days after surgery.
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