Research on Indocyanine Green Angiography for Predicting Postoperative Hypoparathyroidism

Hao Jin; Qichao Dong; Zhuocheng He; Jinrui Fan; Kun Liao; Min Cui


Clin Endocrinol. 2019;90(3):487-493. 

In This Article

Materials and Methods


Criteria for selecting the subjects were as follows: A total number of 26 patients with thyroid disease who underwent total thyroidectomy from May 1st to August 08st, 2018 were admitted into our study. The indications for surgery included the following: (a) malignant biopsy results; (b) clinically worrying lesion; (c) compressive symptoms; (d) recurrent cancer; (e) recurrent cyst; (f) thyroglossal duct cyst; (g) thyrotoxicosis; and (h) cosmetic issues.

In order to identify parathyroid gland tissue, the fluorescence imaging system and ICG dyes were applied during the surgical procedure for all participants. Prior to undertaking the investigation, ethical clearance was obtained from Zhuhai People's Hospital Ethical Committee. Written informed consents were acquired from each subject before the data were collected.

Surgical Procedure and ICG Angiography Method

Patients received general anaesthesia with endotracheal intubation. After that they were placed in a supine position with their necks slightly extended. A 4-6 cm incision was made on the superior border of the sternum. Platsysma myoides were abstracted to expose the thyroid gland. From the sternal notch to the level of the thyroid cartilage, subplastymal flap dissection was conducted. The thyroid lobe was dissected with an harmonic scalpel (Johnson & Johnson Inc, New Brunswick, NJ, USA). In the process of operation, recurrent laryngeal nerves, thyroid arteries and thyroid veins should be carefully identified or transected. After that, total thyroidectomy was conducted. After one lobe of thyroid had been resected, the ICG angiograohy was performed to identify the parathyroid and valuate the parathyroid perfusion. The approach to the patient is shown as Figure 1.

Figure 1.

A schematic figure showing the approach to the patient. A, Incision and thyroid gland partial resection; B, Resected thyroid lobe; C, Intraoperative evaluation of the parathyroid gland visually(circle shows the parathyroid gland); D, ICG infusion and the parathyroid gland evaluation by fluorescence; E, Resected parathyroid gland; F, The resected parathyroid gland evaluation by fluorescence (final surgical decision for the parathyroid autotransplantation)

Using the fluorescence imaging system Intraoperative Navigation System (INS; Digi-MIHI-I-001; Digital Precision Medicine Technology Co., Ltd, Beijing, China) and ICG dye, it was possible to identify the intrinsic fluorescence of different tissues. The INS was manipulated according to the instructions of the equipment. According to the use of the hardware system, the imaging system control software was developed by Beijing Digital Precision Medicine Technology Co., Ltd. The main function of the software consists of two parts. One is the real-time video imaging mode. In this mode, the real-time fluorescence, green and colour images could be displayed on the screen. The other part is the camera quantification mode. When we need to calculate the images, after setting the parameters of the camera, the region of interest (ROI) will be calculated in real time. Furthermore, if the reference ROI was chosen, signal to background ratio (SBR) will also be calculated simultaneously. All procedures were carried out on the system.

The INS has adjustable configurations, and its parameters for measurement were fixed (brightness was minimum, contrast was maximum, excitation light was maximum, and the fluorescence mode was preselected) in this study. In fluorescence mode, the INS excitation light blinked on and off at 30 Hz. The images were constructed by subtracting the light-off image from the light-on image every 0.033 second. Injection of 5 mg ICG dye during the surgical procedure was given to patients after adequate exposure of each central neck compartment. The parathyroid glands took up the dye within 2 minutes and remained fluorescent up to 20 minutes. The injection could be repeated until a maximum regimen of 5 mg/kg/d was reached. Images were acquired the software of the INS. ICG is a kind of anionic, water-soluble tricarbocyananine molecule, which would emit fluorescence when it was excited by near-infrared (NIR) fluorescence with a wavelength of 800 nm.[5] ICG has a mean (SD) half-life of 3.4 (0.7) minutes.[5] When injected intravenously, ICG could rapidly bind plasma lipoproteins. Previous research has found that as the ICG is excreted through the hepatic system at once via first-pass effect, ICG does not possess any toxic or other kinds of side effects.[13]

All identified parathyroid glands were scored visually from grade 0 to grade 2 according to vascularity of parathyroid before ICG angiography was performed. Score 0, score 1 and score 2 represents no vascularity, moderate vascularity and excellent vascularity respectively. In the ICG angiography, the parathyroid fluorescence intensity (FI) depends on the amount of ICG took up by the parathyroid. The mechanism for the parathyroid to take up the dye should be related to the abundant blood supply of endocrine organs. Thereby, FI of the parathyroid reflects vascularization of the parathyroid. In ICG angiography applications, the different grades of grey can be applied as the standard of different levels of the parathyroid function. The parathyroid glands were scored from score 0 to score 2 according to the FI after ICG angiography. Score 0, score 1 and score 2 represents weak FI, moderate FI and strong FI respectively. For the parathyroid glands which were visually evaluated as well vascularized, but were valued as devascularized in ICG angiography, the surgeons will conduct the parathyroid autotransplantation.

Postoperative Follow-up

Serum calcium and parathyroidism (PTH) levels of all participants were measured postoperative day (POD) 1, POD 7, POD 14 and 6 months after operation. Oral calcium and 25-hydroxyvitamin D supplementation were given to participants until the first follow-up appointment at POD 7. Calcium and PTH levels were measured in the clinical laboratories of Zhuhai People's Hospital. The flow chart are listed in Figure 2.

Figure 2.

Flow chart of the study. Hypoparathyroidism was defined by a parathyroidism level below 1.1 pmol/L; ICG indocyanine green; POD postoperative day

Statistical Analysis

The data groups were presented as mean values (SD) and compared using chi-square test. A P value Descriptive data were generated for all variables. P < 0.05 was considered as statistically significant. Statistical analysis was performed using SPSS software (version 22.0; IBM Co., Ltd, Amun, New York, NY, USA).