The ability to better identify and preserve normal parathyroid glands during this surgery could reduce patient morbidity, length of hospitalization, and overall cost of care. —Mark Zafereo, MD
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February 2021
During surgery, the practitioner may accidentally remove the parathyroid glands or cut off the very tiny vessels that provide their blood supply, causing the organs to die. These outcomes are often temporary, but a small percentage of patients experience permanent loss of their parathyroid glands, said Dr. Stack. Newer near-infrared imaging devices could help surgeons mitigate these risks, which is crucial even if the total number of patients affected is small, he added.
“You may have only a 2% to 3% chance of developing hypoparathyroidism overall, but in any given patient we could have a 0% or 100% risk. At this time, there’s limited treatment for this condition. The surgeon is advised to keep a working parathyroid gland in the neck.”
How Technologies Compare
In the past 10 to 15 years, technology emerged to help surgeons identify various structures near the thyroid, including robust nerve monitoring capability using a specialized endotracheal tube that provides a signal when nerves are stimulated, said David Terris, MD, professor and surgical director at Augusta University Thyroid and Parathyroid Center in Georgia. While nerve monitoring improved the procedure’s safety and quality immensely, it did not address the challenge of identifying the parathyroid glands, he said.
ICG-enhanced fluorescence imaging was approved by the FDA for clinical use in 1959 and was first used to assess macular degeneration in patients, but in recent years, various ICG devices have been used in thyroid and parathyroid surgery. Although adverse reactions to ICG dye are very rare (fatal allergic reactions are estimated to occur in as few as one out of 333,000 cases) and the technology is an effective way to assess parathyroid gland function (Br J Surg. 2016;103:537-543), surgeons point out its drawbacks.
“After you inject the patient, the dye works only for a short time, and it’s clunky and cumbersome to use,” said Dr. Terris. Once injected, the contrast dye has a half-life of three to five minutes and may be eliminated after 20 minutes (Gland Surg. 2017;6:579-586).
Phillip K. Pellitteri, DO, an otolaryngologist–head and neck surgeon in private practice in Danville, Penn., also finds ICG imaging systems “cumbersome” to use, requiring a camera and tripod. Although relatively safe, ICG dye still carries a potential toxicity risk, and “the stimulating light may not penetrate the fat or tissue over the parathyroid glands,” he said.
In 2011, a group of biomedical engineers at Vanderbilt University published a paper on near-infrared imaging technology using autofluorescence as a “nonintrusive, real-time, automated, in vivo method for the detection of the parathyroid gland” during surgery (J Biomed Opt. 2011;16:067012). When parathyroid tissue is excited by light at a near-infrared wavelength of 785 nanometers, it exhibits intense fluorescence (J Clin Med. 2020;9:830). After reading this paper, Dr. Pellitteri said he was intrigued by the capability of the technology when he first heard about it around 2016.
“It’s thought that there’s a calcium-sensing entity in these glands that’s molecularly active when stimulated by specific wavelengths of light,” he said. “This could create real-time autofluorescence that can be projected on a video screen and can be digitally recorded. With real-time autofluorescence, you have the advantage of looking and working at the same time, and this expedites the procedure. It’s a smoother, more efficient evaluation.”