Near Infra Red Imaging (NIFI): a non-invasive, effective and reproducible technology to identify Parathyroid Gland during Thyroid Surgery

Abstract

The number of thyroid surgeries especially due to malignant indications has risen in past few decades in India as well as across the globe. The most common complication after Total Thyroidectomy is hypocalcemia from hypoparathyroidism which occurs majorly due to inadvertent removal of parathyroid glands (PGs) or injury leading to devascularization of PG. Post surgery hypocalcaemia (PSH) is assessed by evaluating the value of post-surgery 24-48 hr Serum Calcium level. Majority of times the PSH is transient, it recovers in few weeks to months, only if it persists for > 6 months it is labelled as permanent hypocalcemia. According to literature incidence of transient and permanent PSH is 20–35 % and 1–10%, respectively. PSH is symptomatic and sometimes morbid. It can only be prevented/decreased by early identification and preservation of PGs. The standard methodology is visual analysis of surgical field by operating surgeon. PGs are small in size, with colour similar to brown fat and their position in thyroid bed is also not consistent. They are difficult to identify and success in this method depends on the experience of operating team. This study evaluates the use Near Infra- Red Imaging during thyroidectomy to preserve the PG based on its inherent autofluorescence. PG, when viewed through Near Infra-Red Imaging (NIFI), at wavelength of 785 nm, there is a spontaneous and immediate emission of fluorescent light at 820–830 nm from PGs which is 2- to 11-fold enhanced signal over that of the surrounding tissue. The study consists of 7 patients who underwent Total or Completion Thyroid surgeries with use of NIFI along with review of literature. All the seven patients did not experience PSH and in one patient Intrathyroidal PG was identified with thyroid gland in-situ. The study advocates the use of NIFI to make thyroid surgery safer.