Background There are four (one pair on top and one pair on bottom) flat, oval, green pea-sized tissues located on the dorsal side of the thyroid gland, which are the parathyroid glands. According to statistics, 80% of normal people have 4 parathyroid glands, 6% have 5 parathyroid glands, 13% have 3 parathyroid glands, and some have up to 8 parathyroid glands, but it is rare to have <3 or >5 parathyroid glands. The parathyroid glands are generally yellowish, reddish, or reddish-brown in color, and most are spherical, elliptical, or flattened oval. The parathyroid glands are often surrounded by fat and lymphatic tissue and are not easily identified. The function of the parathyroid glands is to secrete parathyroid hormone (PTH), which regulates and maintains the stability and balance of calcium and phosphorus levels in the body. One of the most common and serious complications of thyroid cancer surgery is hypoparathyroidism caused by parathyroid gland injury, which is clinically manifested as hypocalcemia. The main symptoms are numbness and tonicity of the face and lips or hands and feet, accompanied by fear and anxiety, increased respiration, followed by facial and hand and foot twitching, abdominal muscle spasm, or even laryngospasm and generalized convulsions, chest pain and cardiac arrhythmia. The quality of life of the patient is seriously affected by hypoparathyroidism. Complications of parathyroid gland injury can occur if the anatomical location of the parathyroid glands is altered or unclear during surgery, or if the technique used to protect the parathyroid glands during thyroid surgery is inadequate. Injuries to the parathyroid glands include temporary parathyroid injury and permanent parathyroid injury. Temporary parathyroid injury requires only calcium supplementation. Patients’ PTH levels return to normal within 3 to 6 months, hypocalcemia disappears, and they can gradually get rid of calcium supplementation. However, if the parathyroid blood supply is severely impaired or several parathyroid glands are removed, low calcium symptoms remain after 6 months and long-term oral calcium preparations and osteopontin, supplemented with intravenous calcium supplementation, are required, which means permanent parathyroid injury. A new technology for parathyroid gland protection Nanocarbon suspension injection is a black tracer with lymphatic specificity, which is the first of its kind in China and adds a technical tool for parathyroid gland protection in surgical treatment of thyroid cancer. The specific application is as follows: after local injection of carbon nanosuspension injection around the lesion during thyroid cancer surgery, the tracer flows with the lymphatic network in the thyroid gland and enters the lymphatic system, staining the thyroid gland and the surrounding lymphatic network and lymph nodes one after another, but the parathyroid gland is not stained (negative parathyroid image), which greatly improves the accuracy of identifying the parathyroid gland during surgery with such an obvious contrast. With such an obvious contrast, the accuracy of parathyroid gland identification during surgery is greatly improved, enabling targeted removal of the thyroid gland and complete clearance of the surrounding lymph nodes while better protecting and preserving the parathyroid gland in situ. The results of the clinical comparison between the nano-carbon group and the control group showed that the incidence of postoperative hypocalcemic symptoms of parathyroid injury was significantly lower in the nano-carbon group than in the control group, and the symptoms gradually disappeared after surgery.