Intraoperative near-infrared autofluorescence imaging of parathyroid glands

The application of autofluorescence system contributes to the preservation of parathyroid function during thyroid surgery

PURPOSE

The purpose of this study was to investigate the impact of autofluorescence technology on postoperative parathyroid function and short-term outcomes in patients undergoing thyroid surgery.

METHODS

A total of 546 patients were included in the study, with 287 in the conventional treatment group and 259 in the autofluorescence group. Both groups underwent central lymph node dissection, which is known to affect parathyroid function. Short-term outcomes, including rates of postoperative hypocalcemia and parathyroid dysfunction, serum calcium and PTH levels on the first postoperative day, as well as the need for calcium supplementation, were analyzed. A multivariable analysis was also conducted to assess the impact of autofluorescence on postoperative parathyroid dysfunction, considering factors such as age, BMI, and preoperative calcium levels.

RESULTS

The autofluorescence group demonstrated significantly lower rates of postoperative hypocalcemia and parathyroid dysfunction compared to the conventional treatment group. The autofluorescence group also had better serum calcium and PTH levels on the first postoperative day, and a reduced need for calcium supplementation. Surprisingly, the use of autofluorescence technology did not prolong surgical time; instead, it led to a shorter hospitalization duration. The multivariable analysis showed that autofluorescence significantly reduced the risk of postoperative parathyroid dysfunction, while factors such as age, BMI, and preoperative calcium levels did not show a significant correlation.

CONCLUSION

This study provides evidence that autofluorescence technology can improve the preservation of parathyroid function during thyroid surgery, leading to better short-term outcomes and reduced postoperative complications. The findings highlight the potential of autofluorescence as a valuable tool in the management of parathyroid hypofunction. Further research and validation are needed to establish the routine use of autofluorescence technology in the thyroid.

Avoiding Complications of Thyroidectomy: Preservation of Parathyroid Glands

Preservation of functional parathyroid glands during thyroidectomy and central neck surgery is crucial to avoid the common but serious complication of hypoparathyroidism. The first requirement is a solid foundational knowledge of anatomy and embryology which then enables the surgeon to use meticulous anticipatory dissection with identification and preservation of blood supply to the parathyroids. When preservation of blood supply is not possible, autotransplantation should be performed. New technologies harnessing the natural phenomenon of parathyroid autofluorescence to detect parathyroid tissue and indocyanine green to perform angiography may lead to improved outcomes with low risk to patients.

Improvement in Central Neck Dissection Quality in Thyroid Cancer by Use of Tissue Autofluorescence

BACKGROUND

Risk of postoperative transient or permanent hypoparathyroidism represents one of the most common complications following total thyroidectomy. This risk increases if a cervical lymphadenectomy procedure must also be performed, as is usually the case in thyroid carcinoma patients. Parathyroid autofluorescence (AF) is a non-invasive method that aids intraoperative identification of parathyroid glands.

METHODS

In this prospective study, 189 patients with papillary thyroid cancer who underwent total thyroidectomy with central neck dissection were included. Patients were randomly allocated to one of two groups: NAF (no AF, surgery was performed without AF) and the AF group (surgery was performed with AF-Fluobeam LX system, Fluoptics, Grenoble, France).

RESULTS

The number of excised lymph nodes was significantly higher in the AF compared to the NAF group, with mean values of 21.3 ± 4.8 and 9.2 ± 4.1, respectively. Furthermore, a significantly higher number of metastatic lymph nodes were observed in the AF group. Transient hypocalcemia recorded significantly lower rates in the AF group with 4.9% compared to 16.8% in the NAF group.

CONCLUSIONS

AF use during total thyroidectomy with central neck dissection for papillary thyroid carcinoma patients, decreased the rate of iatrogenic parathyroid gland lesions, and increased the rate of lymphatic clearance.

Comparison of incidental parathyroid tissue detection rates on pathology after total thyroidectomy performed with or without near-infrared autofluorescence imaging

BACKGROUND

Near-infrared autofluorescence imaging is an adjunct to parathyroid identification. As it does not show perfusion, it is important to study its impact during thyroidectomy by measuring quantifiable data on parathyroid detection rather than function. The aim of this study was to compare incidental parathyroidectomy rates in patients undergoing total thyroidectomy with or without near-infrared autofluorescence.

METHODS

Retrospective study of patients who underwent total thyroidectomy between 2014 and 2022 at one center. Clinical parameters, including rates of incidental parathyroid tissue on pathology reports, were compared between near-infrared autofluorescence and non-near-infrared autofluorescence groups. Near-infrared autofluorescence was used to guide dissection (identification) and/or to confirm tissue as parathyroid (confirmation). Statistical analysis was done with Wilcoxon rank sum test and χ2 analysis.

RESULTS

There were 300 patients in the near-infrared autofluorescence and 750 patients in the non-near-infrared autofluorescence group. The rate of incidental parathyroid tissue detection on final pathology was 13.3% (n = 40) in the near-infrared autofluorescence and 23.2% (n = 174) in the non-near-infrared autofluorescence group (P < .001). The rate of incidental parathyroid tissue detected on pathology with near-infrared autofluorescence decreased when used for identification and confirmation of parathyroid tissue (30.0% to 13.4%, P < .001), but not when used for confirmation only (19.6% to 18.5%, P = .89). Impact of near-infra red autofluorescence in decreasing the rate of incidental parathyroid tissue was more profound for early (38.5% to 17.1%) versus mid-late career surgeons (20% to 13%).

CONCLUSION

Our results suggest that the use of near-infrared autofluorescence may help decrease the rate of incidental parathyroid tissue detected on final pathology if used for both identification and confirmation of parathyroid glands during thyroidectomy.

Near-infrared fluorescent imaging for parathyroid identification and/or preservation in surgery for primary hyperparathyroidism

Introduction

Near infrared autofluorescence (NIRAF) is a novel intraoperative technology that has shown promising results in the localisation of parathyroid glands (PGs) over the last decade. This study aimed to assess the potential utility of NIRAF in first time surgery for primary hyperparathyroidism (PHPT).

Methods

An observational study over a period of 3 years in patients who underwent surgery for PHPT was designed. Data on the use of NIRAF and fluorescent patterns in different organs (thyroid and parathyroid) and parathyroid pathology (single versus multi-gland disease) were explored. In addition, cure rates and operating times were compared between the NIRAF and no-NIRAF groups to determine the potential value of NIRAF in this cohort.

Results

In 230 patients undergoing first time surgery for PHPT, NIRAF was used in 50 patients. Of these 50 patients, NIRAF was considered to aid parathyroid identification in 9 patients (18%). The overall cure rate at 6 months of follow-up was 96.5% (98% in NIRAF and 96.1% without NIRAF; p=1.0). The median (interquartile range) operating time was longer in the NIRAF arm at 102 minutes (74-120 minutes) compared to the no-NIRAF arm at 75 minutes (75-109 minutes); however, this difference was not statistically significant (p=0.542). Although the median parathyroid to thyroid (P/T) auto-fluorescence (AF) ratio was similar between single gland and multi gland disease (2.5 vs to 2.76; p=1.0), the P/T AF ratio correlated negatively with increasing gland weight (p=0.038).

Conclusion

The use of NIRAF resulted in some potential "surgeon-perceived" benefit but did not lead to improvements in cure rates. The negative correlation between fluorescent intensity and gland weight suggests loss of fluorescence with pathology, which needs further investigation. Further studies on larger cohorts of patients, in depth analysis of fluorescence patterns between normal, adenomatous, and hyperplastic glands and evaluation of user experience are needed. Primary hyperparathyroidism, hyperparathyroidism, autofluorescence, near-infrared fluorescence, parathyroid glands, endocrine, surgery.

Comparing laser speckle contrast imaging and indocyanine green angiography for assessment of parathyroid perfusion

Accurate intraoperative assessment of parathyroid blood flow is crucial to preserve function postoperatively. Indocyanine green (ICG) angiography has been successfully employed, however its conventional application has limitations. A label-free method overcomes these limitations, and laser speckle contrast imaging (LSCI) is one such method that can accurately detect and quantify differences in parathyroid perfusion. In this study, twenty-one patients undergoing thyroidectomy or parathyroidectomy were recruited to compare LSCI and ICG fluorescence intraoperatively. An experimental imaging device was used to image a total of 37 parathyroid glands. Scores of 0, 1 or 2 were assigned for ICG fluorescence by three observers based on perceived intensity: 0 for little to no fluorescence, 1 for moderate or patchy fluorescence, and 2 for strong fluorescence. Speckle contrast values were grouped according to these scores. Analyses of variance were performed to detect significant differences between groups. Lastly, ICG fluorescence intensity was calculated for each parathyroid gland and compared with speckle contrast in a linear regression. Results showed significant differences in speckle contrast between groups such that parathyroids with ICG score 0 had higher speckle contrast than those assigned ICG score 1, which in turn had higher speckle contrast than those assigned ICG score 2. This was further supported by a correlation coefficient of -0.81 between mean-normalized ICG fluorescence intensity and speckle contrast. This suggests that ICG angiography and LSCI detect similar differences in blood flow to parathyroid glands. Laser speckle contrast imaging shows promise as a label-free alternative that overcomes current limitations of ICG angiography for parathyroid assessment.

Does the Use of Probe-based Near-infrared Autofluorescence Parathyroid Detection Benefit Parathyroidectomy?: A Randomized Single-center Clinical Trial

OBJECTIVE

To evaluate the benefits of probe-based near-infrared autofluorescence (NIRAF) parathyroid identification during parathyroidectomy.

BACKGROUND

Intraoperative parathyroid gland identification during parathyroidectomy can be challenging, while additionally requiring costly frozen sections. Earlier studies have established NIRAF detection as a reliable intraoperative adjunct for parathyroid identification.

METHODS

Patients undergoing parathyroidectomy for primary hyperparathyroidism were prospectively enrolled by a senior surgeon (>20 years experience) and a junior surgeon (<5 years experience), while being randomly allocated to the probe-based NIRAF or control group. Data collected included procedure type, number of parathyroids identified with high confidence by the surgeon and the resident, number of frozen sections performed, parathyroidectomy duration, and number of patients with persistent disease at the first postoperative visit.

RESULTS

One hundred sixty patients were randomly enrolled under both surgeons to the probe group (n=80) versus control (n=80). In the probe group, parathyroid identification rate of the senior surgeon improved significantly from 3.2 to 3.6 parathyroids per patient ( P <0.001), while that of the junior surgeon also rose significantly from 2.2 to 2.5 parathyroids per patient ( P =0.001). Parathyroid identification was even more prominent for residents increasing significantly from 0.9 to 2.9 parathyroids per patient ( P <0.001). Furthermore, there was a significant reduction in frozen sections utilized in the probe group versus control (17 vs 47, P =0.005).

CONCLUSION

Probe-based NIRAF detection can be a valuable intraoperative adjunct and educational tool for improving confidence in parathyroid gland identification, while potentially reducing the number of frozen sections required.

Risk Factors for Calcium-Phosphate Disorders after Thyroid Surgery

INTRODUCTION

Iatrogenic hypoparathyroidism following thyroidectomy is one of the most common complications significantly reducing patients' quality of life.

OBJECTIVES

This study aimed to analyze the risk factors for calcium-phosphate disorders following thyroidectomy.

PATIENTS AND METHODS

The study group consisted of 211 patients who underwent thyroidectomy for different conditions in 2018-2020. Demographic, clinical and surgical risk factors were analyzed against hypoparathyroidism and hypocalcemia.

RESULTS

Hypoparathyroidism occurred in 15.63% of patients, and hypocalcemia occurred in 45% of those operated on. There was statistical significance between hypoparathyroidism and the extent of thyroid surgery: thyroidectomy vs. lobectomy (p = 0.02, OR = 4.5) and surgeon experience (p = 0.016, OR = 6.9). Low preoperative PTH levels were associated with a higher incidence of hypoparathyroidism (p = 0.055, OR = 0.9). There was a statistically significant correlation between the occurrence of hypocalcemia and preoperative vitamin D deficiency (p = 0.04, OR = 3.5). Low calcium levels before surgery were associated with a higher incidence of hypocalcemia (p = 0.051, OR = 0.5). Meta-analyses of selected risk factors confirmed that the most significant factor in the incidence of hypocalcemia was a decrease in PTH levels (p < 0.001).

CONCLUSIONS

The extent of thyroid surgery and the experience of the surgeon are the most significant risk factors for hypoparathyroidism. Hypocalcemia is much more common than hypoparathyroidism. Among the risk factors for hypocalcemia, in addition to the decrease in parathormone levels due to iatrogenic parathyroid damage, we should mention vitamin D deficiency in the preoperative period.

Parathyroid gland detection using an intraoperative autofluorescence handheld imager - early feasibility study

Introduction

Parathyroid glands may be compromised during thyroid surgery which can lead to hypoparathyroidism and hypocalcemia. Identifying the parathyroid glands relies on the surgeon's experience and the only way to confirm their presence was through tissue biopsy. Near infrared autofluorescence technology offers an opportunity for real-time, non-invasive identification of the parathyroid glands.

Methods

We used a new research prototype (hANDY-I) developed by Optosurgical, LLC. It offers coaxial excitation light and a dual-Red Green Blue/Near Infrared sensor that guides anatomical landmarks and can aid in identification of parathyroid glands by showing a combined autofluorescence and colored image simultaneously.

Results

We tested the imager during 23 thyroid surgery cases, where initial clinical feasibility data showed that out of 75 parathyroid glands inspected, 71 showed strong autofluorescence signal and were correctly identified (95% accuracy) by the imager.

Conclusions

The hANDY-I prototype demonstrated promising results in this feasibility study by aiding in real-time visualization of the parathyroid glands. However, further testing by conducting randomized clinical trials with a bigger sample size is required to study the effect on levels of hypoparathyroidism and hypocalcemia.

The magic mirror: a novel intraoperative monitoring method for parathyroid glands

The accurate detection of parathyroid glands (PGs) during surgery is of great significance in thyroidectomy and parathyroidectomy, which protects the function of normal PGs to prevent postoperative hypoparathyroidism and the thorough removal of parathyroid lesions. Existing conventional imaging techniques have certain limitations in the real-time exploration of PGs. In recent years, a new, real-time, and non-invasive imaging system known as the near-infrared autofluorescence (NIRAF) imaging system has been developed to detect PGs. Several studies have confirmed that this system has a high parathyroid recognition rate and can reduce the occurrence of transient hypoparathyroidism after surgery. The NIRAF imaging system, like a magic mirror, can monitor the PGs during surgery in real time, thus providing great support for surgeries. In addition, the NIRAF imaging system can evaluate the blood supply of PGs by utilizing indocyanine green (ICG) to guide surgical strategies. The NIRAF imaging system and ICG complement each other to protect normal parathyroid function and reduce postoperative complications. This article reviews the effectiveness of the NIRAF imaging system in thyroidectomies and parathyroidectomies and briefly discusses some existing problems and prospects for the future.

Emerging Imaging Technologies for Parathyroid Gland Identification and Vascular Assessment in Thyroid Surgery: A Review From the American Head and Neck Society Endocrine Surgery Section

Importance

Identification and preservation of parathyroid glands (PGs) remain challenging despite advances in surgical techniques. Considerable morbidity and even mortality result from hypoparathyroidism caused by devascularization or inadvertent removal of PGs. Emerging imaging technologies hold promise to improve identification and preservation of PGs during thyroid surgery.

Observation

This narrative review (1) comprehensively reviews PG identification and vascular assessment using near-infrared autofluorescence (NIRAF)-both label free and in combination with indocyanine green-based on a comprehensive literature review and (2) offers a manual for possible implementation these emerging technologies in thyroid surgery.

Conclusions and Relevance

Emerging technologies hold promise to improve PG identification and preservation during thyroidectomy. Future research should address variables affecting the degree of fluorescence in NIRAF, standardization of signal quantification, definitions and standardization of parameters of indocyanine green injection that correlate with postoperative PG function, the financial effect of these emerging technologies on near-term and longer-term costs, the adoption learning curve and effect on surgical training, and long-term outcomes of key quality metrics in adequately powered randomized clinical trials evaluating PG preservation.

Educational Review: Intraoperative Parathyroid Fluorescence Detection Technology in Thyroid and Parathyroid Surgery

BACKGROUND

Accurate parathyroid gland (PG) identification is a critical yet challenging component of cervical endocrine procedures. PGs possess strong near-infrared autofluorescence (NIRAF) compared with other tissues in the neck. This property has been harnessed by image- and probe-based near-infrared fluorescence detection systems, which have gained increasing popularity in clinical use for their ability to accurately aid in PG identification in a rapid, noninvasive, and cost-effective manner. All NIRAF technologies, however, cannot differentiate viable from devascularized PGs without the use of contrast enhancement. Here, we aim to provide an overview of the rapid evolution of these technologies and update the surgery community on the most recent advancements in the field.

METHODS

A PubMed literature review was performed using the key terms "parathyroid," "near-infrared," and "fluorescence." Recommendations regarding the use of these technologies in clinical practice were developed on the basis of the reviewed literature and in conjunction with expert surgeons' opinions.

RESULTS

The use of near-infrared fluorescence detection can be broadly categorized as (1) using parathyroid NIRAF to identify both healthy and diseased PGs, and (2) using contrast-enhanced (i.e., indocyanine green) near-infrared fluorescence to evaluate PG perfusion and viability. Each of these approaches possess unique advantages and disadvantages, and clinical trials are ongoing to better define their utility.

CONCLUSIONS

Near-infrared fluorescence detection offers the opportunity to improve our collective ability to identify and preserve PGs intraoperatively. While additional work is needed to propel this technology further, we hope this review will be valuable to the practicing surgeon.

The impact of near-infrared autofluorescence on postoperative hypoparathyroidism during total thyroidectomy: a case-control study

PURPOSE

Near-infrared autofluorescence is a new technology in thyroid surgery to better localize and preserve parathyroid glands. The purpose of this study is to assess if the adoption of NIR-AF can improve in short-, medium-, and long-term post-operative calcium and PTH levels compared to conventional "naked eye" surgery in patients undergoing TT for benign or malignant conditions.

METHODS

134 patients undergone total thyroidectomy between January 2020 and June 2022; 67 were treated with conventional thyroidectomy, the other 67 underwent surgery adopting an autofluorescence detecting device.

RESULTS

Significant differences were found between the two groups in percentage of patients with short-term hypocalcemia (p = 0.04) and short-term hypoparathyroidism (p = 0.011). Median short-term (p = 0.01) and medium-term (p = 0.03) PTH levels were significantly higher in autofluorescence group, while, short- (p = 0.001), medium- (p < 0.001) and long-term (p = 0.019) percentage variation of PTH levels from baseline were significantly higher in the standard-care group. Finally, the prescription of oral calcium (p < 0.01) after surgery were significantly lower in the autofluorescence group.

CONCLUSION

The adoption of near-infrared autofluorescence during total thyroidectomy is related to lower short-term hypocalcemia and hypoparathyroidism rates, decreased variation of post-operative PTH levels in short- and medium- and long-term, reducing the necessity of supplementation therapy with oral calcium compared to conventional surgery.

The utility of intraoperative PTH dosage in primary hyperparathyroidism based on preoperative diagnosis and surgical choice

BACKGROUND

The aim of this study was to evaluate the impact of the intraoperative PTH (ioPTH) monitoring in the success of parathyroidectomy based on the concordant or indeterminate preoperative imaging studies of localization and the performed surgical choices.

METHODS

Fourthy-seven patients who received parathyroidectomy operations were divided in four groups: concordance of the imaging and ioPTH, concordance of the imaging and no ioPTH, indeterminate imaging and ioPTH and indeterminate imaging and no ioPTH.

RESULTS

Overall, patients in whom ioPTH monitoring was not performed were healed in 89.47% of cases, while the percentage of recovery in patients receiving ioPTH was 85.71%. There were no differences in the changes in strategy or in the cure rates with the use of ioPTH.

CONCLUSIONS

No significant differences were found, independently from the preoperative imaging agreement, in either the cure rate or in the change of intraoperative strategy using the ioPTH dosage.

Parathyroid Autofluorescence in Pediatric Thyroid Surgery: Experience With False Positive and False Negative Results

Devices for near-infrared light stimulation of autofluorescence (NIRAF) allow for intraoperative identification of parathyroid glands with high sensitivity in adults. However, their performance in the pediatric population is unknown. In this case series with chart review at a tertiary academic children's hospital, we investigated pediatric patients undergoing thyroid surgery and concurrent use of a probe-based NIRAF device. Thirteen patients (ages 6-18 years) underwent thyroid and/or neck dissection procedures, and 2 patients had revision procedures for a total of 15 cases with the NIRAF device. Eight cases had NIRAF values that matched surgeon opinion of parathyroid tissue or histology when available. Six cases had false positive NIRAF readings (40.0%) and 1 case had false negative readings (6.7%). Compared with surgeon opinion or histology, the NIRAF device confirmed 26 of 34 parathyroid gland candidates (76.5%). These devices need further investigation in pediatric patients, whose tissues may have different autofluorescence characteristics.

Detectable depth of unexposed parathyroid glands using near-infrared autofluorescence imaging in thyroid surgery

Background

Near-infrared light can penetrate the fat or connective tissues overlying the parathyroid gland (PG), enabling early localization of the PG by near-infrared autofluorescence (NIRAF) imaging. However, the depth at which the PG can be detected has not been reported. In this study, we investigated the detectable depth of unexposed PGs using NIRAF during thyroidectomy.

Materials and methods

Fifty-one unexposed PGs from 30 consecutive thyroidectomy patients, mapped by an experienced surgeon (K.D. Lee) with the use of NIRAF imaging, were included. For NIRAF detection of PGs, a lab-built camera imaging system was used. Detectable depths of the unexposed PGs were measured using a Vernier caliper. The NIRAF images were classified as faint or bright depending on whether a novice could successfully interpret the image as showing the PG. Data on variables that may affect detectable depth and NIRAF intensity were collected.

Results

Detectable depth ranged between 0.35 and 3.05 mm, with a mean of 1.23 ± 0.73 mm. The average NIRAF intensity of unexposed PGs was 3.13 au. After dissection of the overlying tissue, the intensity of the exposed PG increased to 4.88 au (p < 0.001). No difference in NIRAF intensity between fat-covered (3.27 ± 0.90 au) and connective tissue-covered PGs (3.00 ± 1.23 au) was observed (p = 0.369). PGs covered by fat tissue (depth: 1.77 ± 0.67 mm) were found at deeper locations than those covered by connective tissue (depth: 0.70 ± 0.21 mm) (p < 0.001). The brightness of images of the faint group (2.14 ± 0.48 au) was on average 1.24 au lower than that of the bright group (3.38 ± 1.04 au) (p = 0.001). A novice successfully localized 80.4% of the unexposed PGs. Other variables did not significantly affect detectable depth.

Conclusion

Unexposed PGs could be mapped using NIRAF imaging at a maximum depth of 3.05 mm and an average depth of 1.23 mm. A novice was able to localize the PGs before they were visible to the naked eye at a high rate. These results can be used as reference data for localization of unexposed PGs in thyroid surgery.

Near-infrared fluorescent imaging techniques for the detection and preservation of parathyroid glands during endocrine surgery

Objectives

In over 30% of all thyroid surgeries, complications arise from transient and definitive hypoparathyroidism, underscoring the need for real-time identification and preservation of parathyroid glands (PGs). Here, we evaluate the promising intraoperative optical technologies available for the identification, preservation, and functional assessment of PGs to enhance endocrine surgery.

Methods

We performed a review of the literature to identify published studies on fluorescence imaging in thyroid and parathyroid surgery.

Results

Fluorescence imaging is a well-demonstrated approach for both in vivo and in vitro localization of specific cells or tissues, and is gaining popularity as a technique to detect PGs during endocrine surgery. Autofluorescence (AF) imaging and indocyanine green (ICG) angiography are two emerging optical techniques to improve outcomes in thyroid and parathyroid surgeries. Near-infrared-guided technology has significantly contributed to the localization of PGs, through the detection of glandular AF. Perfusion through the PGs can be visualized with ICG, which can also reveal the blood supply after dissection.

Conclusions

Near infrared AF and ICG angiography, providing a valuable spatial and anatomical information, can decrease the incidence of complications in thyroid surgery.

Update on Preoperative Parathyroid Localization in Primary Hyperparathyroidism

Parathyroidectomy is the treatment of choice for primary hyperparathyroidism when the clinical criteria are met. Although bilateral neck exploration is traditionally the standard method for surgery, minimally invasive parathyroidectomy (MIP), or focused parathyroidectomy, has been widely accepted with comparable curative outcomes. For successful MIP, accurate preoperative localization of parathyroid lesions is essential. However, no consensus exists on the optimal approach for localization. Currently, ultrasonography and technetium-99m-sestamibi-single photon emission computed tomography/computed tomography are widely accepted in most cases. However, exact localization cannot always be achieved, especially in cases with multiglandular disease, ectopic glands, recurrent disease, and normocalcemic primary hyperparathyroidism. Therefore, new modalities for preoperative localization have been developed and evaluated. Positron emission tomography/computed tomography and parathyroid venous sampling have demonstrated improvements in sensitivity and accuracy. Both anatomical and functional information can be obtained by combining these methods. As each approach has its advantages and disadvantages, the localization study should be deliberately chosen based on each patient's clinical profile, costs, radiation exposure, and the availability of experienced experts. In this review, we summarize various methods for the localization of hyperfunctioning parathyroid tissues in primary hyperparathyroidism.

Indocyanine green (ICG) fluorescence guide for the use and indications in general surgery: recommendations based on the descriptive review of the literature and the analysis of experience

Indocyanine Green is a fluorescent substance visible in near-infrared light. It is useful for the identification of anatomical structures (biliary tract, ureters, parathyroid, thoracic duct), the tissues vascularization (anastomosis in colorectal, esophageal, gastric, bariatric surgery, for plasties and flaps in abdominal wall surgery, liver resection, in strangulated hernias and in intestinal ischemia), for tumor identification (liver, pancreas, adrenal glands, implants of peritoneal carcinomatosis, retroperitoneal tumors and lymphomas) and sentinel node identification and lymphatic mapping in malignant tumors (stomach, breast, colon, rectum, esophagus and skin cancer). The evidence is very encouraging, although standardization of its use and randomized studies with higher number of patients are required to obtain definitive conclusions on its use in general surgery. The aim of this literature review is to provide a guide for the use of ICG fluorescence in general surgery procedures.

Near-Infrared Autofluorescence Imaging in Thyroid Surgery: A Systematic Review and Meta-Analysis

OBJECTIVE

This meta-analysis aimed to assess the position of near-infrared autofluorescence (NIRAF) imaging in the recognition and protection of the parathyroid gland (PG) during thyroidectomy.

METHODS

The PubMed, MEDLINE, EMBASE, Web of Science, and Cochrane Library databases were searched up to June 2021. The primary outcome was to evaluate the rates of postoperative hypocalcemia, inadvertent PG resection, and autotransplantation of PG when adopting NIRAF imaging compared with standard naked-eye (N-E) surgery.

RESULTS

Eight studies with 2,889 patients were enrolled in the analysis. Our analysis showed that the incidence of transient hypocalcemia was 7.11% (60/844) in the NIRAF group and 22.40% (458/2045) in the N-E group (p < 0.0001) and the rate of transient hypoparathyroidism was 28.31% (126/445) and 33.36% (496/1487) in the NIRAF and N-E groups (p = 0.0008). The rate of inadvertent resection of PGs was 7.65% (55/719) in the NIRAF group and 14.39% (132/917) in the N-E group (p < 0.0001). No significant difference was observed in other indexes including the pooled proportion of permanent hypocalcemia and rate of PG autotransplantation.

CONCLUSIONS

The application of NIRAF imaging in thyroidectomy can help lower the incidence of inadvertent PG resection and reduce the risk of postoperative hypocalcemia and hypoparathyroidism compared with N-E recognition.

Autofluorescence of parathyroid glands during endocrine surgery with minimally invasive technique

PURPOSE

Accidental injury to the parathyroid glands (PTGs) is common during thyroid and parathyroid surgery. To overcome the limitation of naked eye in identifying the PTGs, intraoperative autofluorescence imaging has been embraced by an increasing number of surgeons. The aim of our study was to describe the technique and assess its utility in clinical practice.

METHODS

Near-infrared (NIR) autofluorescence imaging was carried out during open parathyroid and thyroid surgery in 25 patients (NIR group), while other 26 patients underwent traditional PTG detection based on naked eye alone (NO-NIR group). Primary variables assessed for correlation between traditional approach and autofluorescence were number of PTGs identified and incidence of postoperative hypoparathyroidism (hypoPT).

RESULTS

81.9% of PTGs were detected by means of fluorescence imaging and 74.5% with visual inspection alone, with an average of 2.72 PTGs visualized per patient using NIR imaging versus approximately 2.4 per patient using naked eye (p = 0.38). Considering only the more complex total thyroidectomies (TTs), the difference was almost statistically significant (p = 0.06). Although not statistically significant, the observed postoperative hypoPT rate was lower in the NIR group.

CONCLUSION

Despite the limitations and technical aspects still to be investigated, fluorescence seems to reduce this complication rate by improving the intraoperative detection of the PTGs.

Real-time intraoperative near-infrared autofluorescence imaging to locate the parathyroid glands: A preliminary report

Identification and localization of parathyroid glands (PGs) remains a challenge for surgeons. The aim of this study was to evaluate the efficiency of intraoperative near-infrared autofluorescence (NIRAF) imaging to detect PGs in thyroid and parathyroid diseases. Seventy-six patients undergoing surgery for thyroid or parathyroid diseases between July 9, 2020 and August 20, 2021 were retrospectively analyzed. Intraoperative carbon nanoparticle (CN) negative imaging and handheld NIRAF imaging were successively performed for each patient. Of 206 PGs that needed to be identified for surgery, 162 were identified by NIRAF imaging, with a theoretical rate of identification of 78.64%. This was higher than the rate of identification with CN negative imaging, which was 75.73%. The number of PGs identified by NIRAF imaging and CN negative imaging did not differ significantly in either total thyroidectomy or thyroid lobectomy. In addition, the autofluorescence (AF) intensity of secondary parathyroid adenoma was weaker than that of normal PGs. NIRAF imaging is potentially a more efficient tool for identification of PGs than CN negative imaging, with a shorter learning curve and lower risk. It may not be well-suited to secondary hyperthyroidism or adenoma, but it was more efficient at identifying excised specimens than visual identification by a surgeon.

[Research progress of autofluorescence imaging of parathyroid glands]

The main causes of hypoparathyroidism are unintentional parathyroidectomy and/or impaired blood supply. Therefore, accurate identification and preservation of parathyroid glands in situ during thyroid or parathyroid surgery has become one of the problems that plague endocrine surgeons. In recent years, near-infrared autofluorescence imaging technology has gradually attracted more and more attention from surgeons because of its simplicity, safety, accuracy, real-time, no-contrast agent, and non-invasiveness. This article reviews the development history, clinical application, and application prospects of the parathyroid gland autofluorescence imaging technology in recent years.

Indocyanine Green Angiography of Parathyroid Glands versus Intraoperative Parathyroid Hormone Assay as a Reliable Predictor for Post Thyroidectomy Transient Hypocalcemia

BACKGROUND

Prediction of postoperative hypocalcemia is a fundamental issue in thyroidectomy. Indocyanine green (ICG) angiography of parathyroid glands is a feasible method to detect the perfusion of parathyroid glands and predict postoperative hypocalcemia.

MATERIALS AND METHODS

A prospective observational study was conducted at Ain Shams University Hospitals between April 2018 and April 2021. The included cases of total thyroidectomy underwent intraoperative ICG fluorescence angiography to identify the four parathyroid glands and score each gland according to the viability. Patients in which less than four glands were identified were excluded. Intraoperative intact parathyroid hormone (ioPTH) level assay was also measured to compare with ICG in predicting postoperative transient hypocalcemia.

RESULTS

A total of 134 cases underwent total thyroidectomy during the study period. We could identify the four parathyroid glands in 90 patients, including them in the study. We had postoperative hypocalcemia in 28 cases (31.1%). The diagnostic accuracy of ICG angiography and ioPTH level assay was high and almost similar (82.22% versus 87.78%). Both were higher than the surgeons' diagnostic accuracy of visual inspection (62.22%).

CONCLUSIONS

ICG angiography of the parathyroid gland is a safe, reliable predictor for postoperative transient hypocalcemia with a high and almost similar accuracy compared to intraoperative parathyroid hormone level.

Heterogeneity in Utilization of Optical Imaging Guided Surgery for Identifying or Preserving the Parathyroid Glands—A Meta-Narrative Review

Background: Postoperative hypoparathyroidism is the most common complication after total thyroidectomy. Over the past years, optical imaging techniques, such as parathyroid autofluorescence, indocyanine green (ICG) angiography, and laser speckle contrast imaging (LSCI) have been employed to save parathyroid glands during thyroid surgery. This study provides an overview of the utilized methods of the optical imaging techniques during total thyroidectomy for parathyroid gland identification and preservation. Methods: PUBMED, EMBASE and Web of Science were searched for studies written in the English language utilizing parathyroid autofluorescence, ICG-angiography, or LSCI during total thyroidectomy to support parathyroid gland identification or preservation. Case reports, reviews, meta-analyses, animal studies, and post-mortem studies were excluded after the title and abstract screening. The data of the studies were analyzed qualitatively, with a focus on the methodologies employed. Results: In total, 59 articles were included with a total of 6190 patients. Overall, 38 studies reported using parathyroid autofluorescence, 24 using ICG-angiography, and 2 using LSCI. The heterogeneity between the utilized methodology in the studies was large, and in particular, regarding study protocols, imaging techniques, and the standardization of the imaging protocol. Conclusion: The diverse application of optical imaging techniques and a lack of standardization and quantification leads to heterogeneous conclusions regarding their clinical value. Worldwide consensus on imaging protocols is needed to establish the clinical utility of these techniques for parathyroid gland identification and preservation.

Assessing Intraoperative Laser Speckle Contrast Imaging of Parathyroid Glands in Relation to Total Thyroidectomy Patient Outcomes

Background: Accurate assessment of parathyroid gland vascularity is important during thyroidectomy to preserve the function of parathyroid glands and to prevent postoperative hypocalcemia. Laser speckle contrast imaging (LSCI) has been shown to be accurate in detecting differences in parathyroid vascularity. In this surgeon-blinded prognostic study, we evaluate the relationship between intraoperative LSCI measurements and postoperative outcomes of total thyroidectomy patients. Methods: Seventy-two thyroidectomy patients were included in this study. After thyroid resection, an LSCI device was used to image all parathyroid glands identified, and a speckle contrast value was calculated for each. An average value was calculated for each patient, and the data were grouped according to whether the patient had normal (16-77 pg/mL) or low levels of parathyroid hormone (PTH) measured on postoperative day 1 (POD1). The aim of this study was to establish a speckle contrast threshold for classifying a parathyroid gland as adequately perfused and to determine how many such glands are required for normal postoperative parathyroid function. Results: A speckle contrast limit of 0.186 separated the normoparathyroid and hypoparathyroid groups with 87.5% sensitivity and 84.4% specificity: 7 of 8 patients with low PTH on POD1 had an average parathyroid speckle contrast above this limit, while 54 of 64 patients with normal postoperative PTH had an average parathyroid speckle contrast below this limit. Taking this value as the threshold for adequate parathyroid perfusion, it was determined that only one vascularized gland was needed for normal postoperative parathyroid function: 64 of 69 patients (92.8%) with at least one vascularized gland (determined by LSCI) had normal postoperative PTH, while all 3 patients (100%) with no vascularized glands had low postoperative PTH. Overall, the rates of temporary and permanent hypoparathyroidism in this study were 8.3% and 1.4%, respectively. Conclusions: LSCI is a promising technique for assessing parathyroid gland vascularity. It has the potential to help reduce the incidence of hypocalcemia after thyroidectomy by providing surgeons with additional information during surgery to aid in the preservation of parathyroid function.

Evaluation of structural and ultrastructural changes in thyroid and parathyroid glands after near infrared irradiation: study on an animal model

Intraoperative identification of parathyroid glands is a tough task for surgeons performing thyroid or parathyroid surgery, because the small size, color and shape of these glands hinder their discrimination from other cervical tissues. In 2011, Paras described the autofluorescence of parathyroid glands, a property that could facilitate their intraoperative identification. Parathyroid glands submitted to a 785 nm laser beam emit fluorescence in the near infrared range, with a peak at 822 nm. As the intrinsic properties of secretory tissues may be affected by the exposure to the near infrared light, a situation that could preclude their intraoperative utilization, the authors compared the structural and ultra-structural patterns of rat’s thyroid and parathyroid glands submitted to irradiation replicating the conditions that allow their intraoperative identification, with those of non irradiated animals. Twenty-four Wistar rats were divided into six groups: animals of Groups 1, 3 and 5 were submitted under general anesthesia to direct irradiation of the cervical area with a 780 nm LED light for 3 minutes through a cervical incision, and animals of Groups 2, 4 and 6 were submitted to cervical dissection without irradiation. Animals of were euthanized immediately (Groups 1 and 2), at Day 30 (Groups 3 and 4) at and at Day 60 (Groups 5 and 6) and thyroid and parathyroid glands were removed: one lobe was prepared for conventional pathological examination and the other lobe for electron microscopy observed by three experienced pathological experts. Twenty-four samples were prepared for conventional histology and there were no alterations reported in any group. Due to technical problems, only 21 samples were observed by electron microscopy and there were no differences in the ultrastructure of parathyroid and thyroid glands, namely the nuclear pattern, mitochondria, endoplasmic reticulum or secretory granules, in any of the groups. These results confirm the innocuity of near infrared irradiation’, allowing its intraoperative utilization.

Near-infrared autofluorescence-based parathyroid glands identification in the thyroidectomy or parathyroidectomy: a systematic review and meta-analysis

PURPOSE

To evaluate the diagnostic accuracy of near-infrared autofluorescence-based identification in the identification of parathyroid glands during thyroidectomy or parathyroidectomy.

METHODS

The clinical studies were retrieved from PubMed, the Cochrane Central Register of Controlled Trials, Embase, Web of Science, SCOPUS, and Google Scholar. The study protocol was registered on Open Science Framework ( https://osf.io/um8rj/ ). The search period ranged from the date of each database's inception to May 2021. Cohort studies dealing with patients of whom parathyroid glands were detected by near-infrared autofluorescence and confirmed clinically or pathologically during thyroidectomy or parathyroidectomy were included. Editorials, letters, "how-I-do-it" descriptions, other site head and neck tumors, and articles with lack of diagnostic identification data were excluded. True positive, true negative, false positive, and false negative were extracted. The QUDAS ver. 2 was used to evaluate the methodological quality.

RESULTS

Seventeen studies with 1198 participants were evaluated in this analysis. Near-infrared autofluorescence-based identification of parathyroid glands showed a diagnostic odds ratio of 228.8759 (95% confidence interval, 134.1099; 390.6063). The area under the summary receiver operating characteristic curve was 0.967. The sensitivity, specificity, negative predictive value, and positive predictive value were 0.9693 (0.9491; 0.9816), 0.9248 (0.8885; 0.9499), 0.9517 (0.8981; 0.9778), and 0.9488 (0.9167; 0.9689), respectively. Subgroup analyses were performed to compare two autofluorescence detection methods, because there was high heterogeneity in the outcomes. The diagnostic accuracy was higher in probe-based detection than in image-based detection.

CONCLUSIONS

Near-infrared autofluorescence-based identification is valuable for identifying the parathyroid glands of patients during thyroidectomy or parathyroidectomy.

Development of an imaging device for label-free parathyroid gland identification and vascularity assessment

During thyroid surgeries, it is important for surgeons to accurately identify healthy parathyroid glands and assess their vascularity to preserve their function postoperatively, thus preventing hypoparathyroidism and hypocalcemia. Near infrared autofluorescence detection enables parathyroid identification, while laser speckle contrast imaging allows assessment of parathyroid vascularity. Here, we present an imaging system combining the two techniques to perform both functions, simultaneously and label-free. An algorithm to automate the segmentation of a parathyroid gland in the fluorescence image to determine its average speckle contrast is also presented, reducing a barrier to clinical translation. Results from imaging ex vivo tissue samples show that the algorithm is equivalent to manual segmentation. Intraoperative images from representative procedures are presented showing successful implementation of the device to identify and assess vascularity of healthy and diseased parathyroid glands.

A Tool to Locate Parathyroid Glands Using Dynamic Optical Contrast Imaging

OBJECTIVES/HYPOTHESIS

Identification of parathyroid glands and adjacent tissues intraoperatively can be quite challenging because of their small size, variable locations, and indistinct external features. The objective of this study is to test the efficacy of the dynamic optical contrast imaging (DOCI) technique as a tool in specifically differentiating parathyroid tissue and adjacent structures, facilitating efficient and reliable tissue differentiation.

STUDY DESIGN

Prospective study.

METHODS

Both animal and human tissues were included in this study. Fresh specimens were imaged with DOCI and subsequently processed for hematoxylin and eosin (H&E) stain. The DOCI images were analyzed and compared to the H&E results as ground truth.

RESULTS

In both animal and human experiments, significant DOCI contrast was observed between parathyroid glands and adjacent tissue of all types. Region of interest analysis revealed most distinct DOCI values for each tissue when using 494 and 572 nm-specific band pass filter for signal detection (P < .005 for porcine tissues, and P = .02 for human specimens). Linear discriminant classifier for tissue type prediction based on DOCI also matched the underlying histology.

CONCLUSIONS

We demonstrate that the DOCI technique reliably facilitates specific parathyroid gland localization. The DOCI technique constitutes important groundwork for in vivo precision endocrine surgery.

LEVEL OF EVIDENCE

4 Laryngoscope, 2021.

The effect of intraoperative autofluorescence monitoring on unintentional parathyroid gland excision rates and postoperative PTH concentrations-a single-blind randomized-controlled trial

PURPOSE

Intraoperative imaging of parathyroid glands (PGs) has been developed in order to reduce the risk of unintentional parathyroidectomy during total thyroidectomy. This novel modality is based on their intrinsic characteristic of autofluorescence (AF) after near-infrared light exposure. The aim of this study was to assess the effect of this method on the risk of unintentional PG excision (total or partial) during total thyroidectomy.

METHODS

This was a single-blind, randomized-controlled trial including adult patients who underwent scheduled total thyroidectomy between December 2019 and March 2020. These patients were randomly allocated to two groups: one in which near-infrared autofluorescence imaging (NIRAF) was applied (NIR group) and one without NIRAF (NONIR group). Hormonal and biochemical assessment was performed pre- and 24-h postoperatively. AF findings and the number of PGs autotransplanted were recorded.

RESULTS

One-hundred and eighty patients were eligible. Unintentional (total or partial) PG excision rates during total thyroidectomy in the NONIR (n = 90) and NIR (n = 90) groups were 28.9% [95% confidence interval (CI) 19.8-39.4%] and 14.4% (95% CI 7.7-22.1%), respectively (p = 0.02). Furthermore, NIR reduced the risk of parathyroid tissue presence in the specimen sent for pathology (relative risk 0.51, 95% CI 0.28-0.92; p = 0.02). However, the number of PGs identified by NIR could not predict the risk of postoperative hypoparthyroidism.

CONCLUSIONS

NIRAF imaging during total thyroidectomy led to a significant reduction in PG excision rates. However, this modality did not result in the reduction of postoperative hypoparathyroidism or hypocalcemia risk.

Initial clinical experiences using the intraoperative probe-based parathyroid autofluorescence identification system-PTeye™ during thyroid and parathyroid procedures

BACKGROUND AND OBJECTIVE

The Food and Drug Administration has cleared a probe-based near-infrared autofluorescence (NIRAF) detection system called PTeye™ as an adjunct tool for label-free intraoperative parathyroid gland (PG) identification. Since PTeye™ has been investigated only in a "blinded" manner to date, this study describes the preliminary impressions of PTeye™ when used by surgeons without being blinded to the device output.

METHODS

Patients undergoing thyroid and parathyroid procedures were prospectively recruited. Target tissues were intraoperatively assessed with PTeye™. The surgeon's confidence in PG identification was recorded concomitantly with NIRAF parameters that were output in real-time from PTeye™.

RESULTS

A retrospective review of prospectively collected data on 83 patients was performed. PTeye™ was used for interrogating 336 target tissues in 46 parathyroid and 37 thyroid procedures. PTeye™ yielded an overall accuracy of 94.3% with a positive predictive value of 93.0% and a negative predictive value of 100%. An increase in confidence for intraoperative PG identification with PTeye™ was observed by all three participating high-volume surgeons, irrespective of their level of accrued surgical experience.

CONCLUSIONS

Probe-based NIRAF detection with PTeye™ can be a valuable adjunct device to intraoperatively identify PGs for surgeons of varied training and experience.

Intraoperative Mapping of Parathyroid Glands Using Fluorescence Lifetime Imaging

BACKGROUND

Hypoparathyroidism is a common complication following thyroidectomy. There is a need for technology to aid surgeons in identifying the parathyroid glands. In contrast to near infrared technologies, fluorescence lifetime imaging (FLIm) is not affected by ambient light and may be valuable in identifying parathyroid tissue, but has never been evaluated in this capacity.

METHODS

We used FLIm to measure the UV induced (355 nm) time-resolved autofluorescence signatures (average lifetimes in 3 spectral emission channels) of thyroid, parathyroid, lymphoid and adipose tissue in 21 patients undergoing thyroid and parathyroid surgery. The Mann-Whitney U test was used to assess the ability of FLIm to discriminate normocellular parathyroid from each of the other tissues. Various machine learning classifiers (random forests, neural network, support vector machine) were then evaluated to recognize parathyroid through a leave-one-out cross-validation.

RESULTS

Statistically significant differences in average lifetime were observed between parathyroid and each of the other tissue types in spectral channels 2 and 3 respectively. The largest change was observed between adipose tissue and parathyroid (P < 0.001), while less pronounced but still significant changes were observed when comparing parathyroid with lymphoid tissue (P < 0.05) and thyroid (P < 0.01). A random forest classifier trained on average lifetimes was found to detect parathyroid tissue with 100% sensitivity and 93% specificity at the acquisition run level.

CONCLUSION

We found that FLIm derived parameters can distinguish the parathyroid glands and other adjacent tissue types and has promise in scanning the surgical field to identify parathyroid tissue in real-time.

Development of an algorithm for intraoperative autofluorescence assessment of parathyroid glands in primary hyperparathyroidism using artificial intelligence

BACKGROUND

Previous work showed that normal and abnormal parathyroid glands exhibit different patterns of autofluorescence, with the former appearing brighter and more homogenous. However, an objective algorithm based on quantified measurements was not provided. The aim of this study is to develop objective algorithms for intraoperative autofluorescence assessment of parathyroid glands in primary hyperparathyroidism using artificial intelligence.

METHODS

The utility of near-infrared fluorescence imaging in parathyroidectomy procedures was evaluated in a study approved by the institutional review board. Autofluorescence patterns of parathyroid glands were measured intraoperatively. Comparisons were performed between normal and abnormal glands, as well as between different pathologies. Using machine learning, decision trees were created.

RESULTS

Normal parathyroid glands were brighter (higher normalized autofluorescence pixel intensity) and more homogenous (lower heterogeneity index) compared to abnormal glands. Optimal cutoffs to differentiate normal from abnormal parathyroid glands were >2.0 for normalized autofluorescence intensity (sensitivity 73%, specificity 70%, area under the curve 0.756) and <0.12 for parathyroid heterogeneity index (sensitivity 75%, specificity 81%, area under the curve 0.839). Decision trees created by machine learning using normalized autofluorescence intensity, heterogeneity index, and gland volume were 95% accurate in predicting normal versus abnormal glands and 84% accurate in predicting subclasses of parathyroid pathologies.

CONCLUSION

To our knowledge, this is the first study to date reporting objective algorithms using quantified autofluorescence data to intraoperatively assess parathyroid glands in primary hyperparathyroidism. These results suggest that objective data can be obtained from autofluorescence signals to help differentiate abnormal parathyroid glands from normal glands.

Autofluorescence pattern of parathyroid adenomas

BACKGROUND

Primary hyperparathyroidism (pHPT) is a common endocrine pathology, and it is due to a single parathyroid adenoma in 80-85 per cent of patients. Near-infrared autofluorescence (NIRAF) has recently been used in endocrine surgery to help in the identification of parathyroid tissue, although there is currently no consensus on whether this technique can differentiate between normal and abnormal parathyroid glands. The aim of this study was to describe the autofluorescence pattern of parathyroid adenoma in pHPT.

METHODS

Between January and June 2019, patients with pHPT who underwent surgical treatment for parathyroid adenoma were enrolled. Parathyroid autofluorescence was measured.

RESULTS

Twenty-three patients with histologically confirmed parathyroid adenomas were included. Parathyroid adenomas showed a heterogeneous fluorescence pattern, and a well defined autofluorescent 'cap' region was observed in 17 of 23 specimens. This region was on average 28 per cent more fluorescent than the rest of the adenoma, and corresponded to a rim of normal histological parathyroid tissue (sensitivity and specificity 88 and 67 per cent respectively). After resection, all patients were treated successfully, with normal postoperative values of calcium and parathyroid hormone documented.

CONCLUSION

Parathyroid adenomas show a heterogeneous autofluorescence pattern. Using NIRAF imaging, the majority of specimens showed a well defined autofluorescent portion corresponding to a rim of normal parathyroid tissue. Further studies should be conducted to validate these findings.

Wireless parathyroid detection device using autofluorescence and smart glasses: A preliminary study

BACKGROUND

Autofluorescence imaging technology has been utilized for preserving or identifying parathyroid glands (PTGs) during thyroid surgery. We developed a wireless PTGs detection device linked with smart glasses that allows for real-time video recording and screen switching according to the light source.

OBJECTIVE

This study aimed to confirm the feasibility of the device and whether it would help preserve the PTG during the surgery.

METHODS

This prospective study was conducted in 30 patients with 66 PTGs. The device's agreement with the physician's judgment was evaluated, and we determined how many PTGs were preserved from thyroidectomy.

RESULTS

The positive agreement rate for PTGs detection between the surgeon and device was 70.9%. Inadvertent parathyroidectomy was identified in surgical specimens of 6 patients (20%). No PTG was removed when it was confirmed by the device (0/39). Of the 27 glands not detected by the device, there was inadvertent removal of 6 PTGs.

CONCLUSIONS

PTGs can be preserved successfully when the detection of them by the device is consistent with the surgeon's discretion. A large-scale controlled study is necessary to demonstrate the practical effect of this device on hypoparathyroidism after thyroidectomy.

Determination of the Optimum Excitation Wavelength for the Parathyroid Gland Using a Near-Infrared Camera

When performing thyroid/parathyroid surgery, difficulty detecting the parathyroid gland is a common experience because it is frequently mistaken with surrounding structures, including the thyroid gland, lymph nodes, and fat. To obtain successful surgical results, the auto fluorescent property of the parathyroid gland occurring at 820-830 nm has been used. Intraoperative visualization and detection by fluorescence enable protection of the gland from damage and unintended removal. Use of a near-infrared (NIR) camera has been proposed to indicate the parathyroid gland, but the devices and success rates have varied. This study aimed to define optimum excitation wavelength (EWL) by measuring the EWL of the parathyroid gland for its autofluorescence. Glands were exposed to EWL at 10-nm intervals from 670-790 nm with a light-emitting diode monochromator; autofluorescence intensity was recorded with a conventional NIR video camera. Autofluorescence intensity curves of three normal parathyroid glands were depicted; the optimum EWL was measured as 760-770 nm. Also, the illumination of the surrounding structures were compared at the optimum EWL. The auto fluorescent intensity of the parathyroid gland was 2-fold greater than for surrounding structures. This difference in fluorescence intensity should enable distinction of the parathyroid gland from surrounding structures. The clarification of the optimum EWL can guide refinements of the NIR camera for better surgical outcomes by improving detection of the parathyroid glands. Also, an understanding of optimum EWL should lead to developments for microscopic devices to unravel the still unknown mechanisms of the intrinsic autofluorescence of the parathyroid gland.

The Accuracy of Near Infrared Autofluorescence in Identifying Parathyroid Gland During Thyroid and Parathyroid Surgery: A Meta-Analysis

OBJECTIVE

We aim to assess the accuracy of near infrared autofluorescence in identifying parathyroid gland during thyroid and parathyroid surgery.

METHOD

A systematic literature search was conducted by using PubMed, Embase, and the Cochrane Library electronic databases for studies that were published up to February 2021. The reference lists of the retrieved articles were also reviewed. Two authors independently assessed the methodological quality and extracted the data. A random-effects model was used to calculate the combined variable. Publication bias in these studies was evaluated with the Deeks' funnel plots.

RESULT

A total of 24 studies involving 2,062 patients and 6,680 specimens were included for the meta-analysis. The overall combined sensitivity and specificity, and the area under curve of near infrared autofluorescence were 0.96, 0.96, and 0.99, respectively. Significant heterogeneities were presented (Sen: I² = 87.97%, Spe: I² = 65.38%). In the subgroup of thyroid surgery, the combined sensitivity and specificity, and the area under curve of near infrared autofluorescence was 0.98, 0.99, and 0.99, respectively, and the heterogeneities were moderate (Sen: I² = 59.71%, Spe: I² = 67.65%).

CONCLUSION

Near infrared autofluorescence is an excellent indicator for identifying parathyroid gland during thyroid and parathyroid surgery.

The Ability of Near-Infrared Autofluorescence to Protect Parathyroid Gland Function During Thyroid Surgery: A Meta-Analysis

OBJECTIVE

We conducted this meta-analysis to assess the ability of near-infrared autofluorescence to protect parathyroid gland function during thyroid surgery.

METHOD

A systematic literature search was conducted using PubMed, Embase, and the Cochrane Library electronic databases for studies published up to February 2021. The reference lists of the retrieved articles were also reviewed. Two authors independently assessed methodological quality and extracted the data. A random-effects model was used to calculate the overall pooled variable and the weighted mean deviation. Publication bias in these studies was evaluated using the Egger's and Begg's tests.

RESULT

Seven studies involving 1,480 patients were included in the analysis. Compared with patients in the naked eye group, the pooled relative risk of inadvertent parathyroid gland resection and parathyroid gland autotransplantation for the patients in the near-infrared autofluorescence group was 0.48 (95% CI, 0.26-0.9, p = 0.023) and 0.39 (95% CI, 0.09-1.68, p = 0.208), respectively. The pooled relative risk of hypocalcemia at 1 day postoperatively and at 6 months postoperatively for the patients in the near-infrared autofluorescence group was 0.49 (95% CI, 0.34-0.71, p < 0.001) and 0.34 (95% CI, 0.06-2.03, p = 0.238) compared with patients in the naked eye group.

CONCLUSION

Near-infrared autofluorescence is significantly associated with a reduced risk of inadvertent parathyroid gland resection and hypocalcemia at 1 day postoperatively.

Detecting the Near Infrared Autofluorescence of the Human Parathyroid: Hype or Opportunity?

OBJECTIVE

With the recent approval of 2 NIRAF-based devices for label-free identification of PG by the Food and Drug Administration, it becomes crucial to educate the surgical community on the realistic scope of this emerging technology. Here, we have compiled a review of studies that utilize NIRAF and present a critical appraisal of this technique for intraoperative PG detection.

BACKGROUND

Failure to visualize PGs could lead to accidental damage/excision of healthy PGs or inability to localize diseased PGs, resulting in postsurgical complications. The discovery that PGs have NIRAF led to new avenues for intraoperatively identifying PGs with high accuracy in real-time.

METHODS

Using the following key terms: "parathyroid, near infrared, autofluorescence" in various search engines such as PubMed and Google Scholar, we identified various publications relevant to this review of NIRAF as a technique for PG identification. Articles were excluded if they focused solely on contrast agents, served as commentaries/overviews on NIRAF or were not written in English.

RESULTS

To date, studies have investigated the potential of NIRAF detection for (i) identifying PG tissues intraoperatively, (ii) locating PGs before or after dissection, (iii) distinguishing healthy from diseased PGs, and (iv) minimizing postoperative hypocalcemia after total thyroidectomy.

CONCLUSIONS

Because NIRAF-based identification of PG is noninvasive and label-free, the popularity of this approach has considerably surged. As the present limitations of various technologies capable of NIRAF detection are identified, we anticipate that newer device iterations will continue to be developed enhancing the current merits of these modalities to aid surgeons in identifying and preserving PGs. However, more concrete and long-term outcome studies with these modalities are essential to determine the impact of this technique on patient outcome and actual cost-benefits.

Novel techniques for intraoperative parathyroid gland identification: a comprehensive review

INTRODUCTION

The parathyroid glands (PGs) are critical for calcium regulation and homeostasis. The preservation of PGs during neck surgery is crucial to avoid postoperative hypoparathyroidism. There are no existing guidelines for intraoperative PG identification, and the current approach relies heavily on the experience of the operating surgeon. A technique that accurately and rapidly identifies PGs would represent a useful intraoperative adjunct.

AREAS COVERED

This review aims to assess common dye and fluorescence-based PG imaging techniques and examine their utility for intraoperative PG identification. A literature search of published data on methylene blue (MB), indocyanine green (ICG) angiography, near-infrared autofluorescence (NIRAF), and the PGs between 1971 and 2020 was conducted on PubMed.

EXPERT OPINION

NIRAF and near-infrared (NIR) parathyroid angiography have emerged as promising and reliable techniques for intraoperative PG identification. NIRAF may aid with real-time identification of both normal and diseased PGs and reduce the risk of postoperative complications such as hypocalcemia. Further large prospective multicenter studies should be conducted in thyroid and parathyroid surgical patient populations to confirm the clinical efficacy of these intraoperative NIR-based PG detection techniques.

Effects of excitation light intensity on parathyroid autofluorescence with a novel near-infrared fluorescence imaging system: two surgical case reports

The intraoperative identification and preservation of the parathyroid glands are vital techniques, which are largely dependent on a surgeon's experience. Therefore, a simple and reproducible technique to identify the parathyroid glands during surgery is needed. Parathyroid tissue shows near-infrared (NIR) autofluorescence, which enables the intraoperative identification of the parathyroid gland. We herein present two cases that underwent surgery on the parathyroid glands, which were observed using the NIR fluorescence imaging system LIGHTVISION^® (Shimazu, Kyoto, Japan). In a case of papillary thyroid carcinoma, the system was adopted to preserve normal parathyroid glands during left hemithyroidectomy. The left lower parathyroid gland was identified using the imaging system under white light; however, its autofluorescence was visualized more clearly with the excitation light of NIR. In a case of primary hyperparathyroidism due to MEN1, the system was adopted to identify and remove all of the parathyroid glands during total parathyroidectomy. The autofluorescence of diseased glands was weaker than that of normal glands, even with the excitation light of NIR. When the parathyroid glands were irradiated with a red laser pointer, the intensity of autofluorescence significantly increased. However, the largest gland, which was pathologically proven to contain strongly proliferating chief cells, did not show autofluorescence. These results suggest that normal or less diseased parathyroid glands, which are generally small and difficult to identify during surgery, showed relatively strong autofluorescence. A stronger excitation light increases the autofluorescence of parathyroid glands, which enhances sensitivity for detecting parathyroid glands during surgery. In conclusion, LIGHTVISION^® is a useful device to identify parathyroid glands and an additional excitation light of a red laser pointer increases the detection sensitivity.

Association of Autofluorescence-Based Detection of the Parathyroid Glands During Total Thyroidectomy With Postoperative Hypocalcemia Risk: Results of the PARAFLUO Multicenter Randomized Clinical Trial

Importance

Because inadvertent damage of parathyroid glands can lead to postoperative hypocalcemia, their identification and preservation, which can be challenging, are pivotal during total thyroidectomy.

Objective

To determine if intraoperative imaging systems using near-infrared autofluorescence (NIRAF) light to identify parathyroid glands could improve parathyroid preservation and reduce postoperative hypocalcemia.

Design, Setting, and Participants

This randomized clinical trial was conducted from September 2016 to October 2018, with a 6-month follow-up at 3 referral hospitals in France. Adult patients who met eligibility criteria and underwent total thyroidectomy were randomized. The exclusion criteria were preexisting parathyroid diseases.

Interventions

Use of intraoperative NIRAF imaging system during total thyroidectomy.

Main Outcomes and Measures

The primary outcome was the rate of postoperative hypocalcemia (a corrected calcium <8.0 mg/dL [to convert to mmol/L, multiply by 0.25] at postoperative day 1 or 2). The main secondary outcomes were the rates of parathyroid gland autotransplantation and inadvertent parathyroid gland resection.

Results

A total of 245 of 529 eligible patients underwent randomization. Overall, 241 patients were analyzed for the primary outcome (mean [SD] age, 53.6 [13.6] years; 191 women [79.3%]): 121 who underwent NIRAF-assisted thyroidectomy and 120 who underwent conventional thyroidectomy (control group). The temporary postoperative hypocalcemia rate was 9.1% (11 of 121 patients) in the NIRAF group and 21.7% (26 of 120 patients) in the control group (between-group difference, 12.6% [95% CI, 5.0%-20.1%]; P = .007). There was no significant difference in permanent hypocalcemia rates (0% in the NIRAF group and 1.6% [2 of 120 patients] in the control group). Multivariate analyses accounting for center and surgeon heterogeneity and adjusting for confounders, found that use of NIRAF reduced the risk of hypocalcemia with an odds ratio of 0.35 (95% CI, 0.15-0.83; P = .02). Analysis of secondary outcomes showed that fewer patients experienced parathyroid autotransplantation in the NIRAF group than in the control group: respectively, 4 patients (3.3% [95% CI, 0.1%-6.6%) vs 16 patients (13.3% [95% CI, 7.3%-19.4%]; P = .009). The number of inadvertently resected parathyroid glands was significantly lower in the NIRAF group than in the control group: 3 patients (2.5% [95% CI, 0.0%-5.2%]) vs 14 patients (11.7% [95% CI, 5.9%-17.4%], respectively; P = .006).

Conclusions and Relevance

The use of NIRAF for the identification of the parathyroid glands may help improve the early postoperative hypocalcemia rate significantly and increase parathyroid preservation after total thyroidectomy.

Trial Registration

ClinicalTrials.gov Identifier: NCT02892253.

Do Near-Infrared Intra-Operative Findings Obtained Using Indocyanine Green Correlate with Post-Thyroidectomy Parathyroid Function? the Icgpredict Study

OBJECTIVE

Postoperative hypoparathyroidism (hypoPT) still remains a significant complication after thyroidectomy. Intra-operative imaging modalities, such as near-infrared fluorescence using indocyanine green (ICG), may assist in identifying and preserving the parathyroid glands (PGs). The purpose of this study was to test the association between the intra-operative ICG staining scoring system and 24-hour postoperative parathyroid hormone (PTH) levels, as well as its capability for intra-operative PG identification.

METHODS

This was a prospective study, recruiting patients scheduled for total thyroidectomy by the same surgical team, from December 2018 to April 2019. Intra-operative angiography was performed after infusion of ICG solution (5 mg). Two minutes later, images were acquired using the near-infrared system.

RESULTS

Sixty patients fulfilled the eligibility criteria. The percentage of temporary postoperative hypoPT (defined as PTH <14 pg/mL) was 11.66%. No association between intra-operative ICG staining score (expressed as the number of PGs scoring <2 per patient) and 24-hour postoperative PTH (r = 0.011; P = .933) or serum calcium concentrations (r = 0.127; P = .335) was observed. There was also no correlation between the location of PGs scoring ≤2 and postoperative PTH (P = .257) or serum calcium levels (P = .950). Moreover, with regard to secondary endpoint, ICG correctly identified PGs in 98.3% of cases. ICG score was not affected by age, gender, duration of operation, or thyroid gland pathology. No allergic reactions attributed to ICG administration were observed.

CONCLUSION

The intra-operative ICG staining scoring system did not predict 24-hour postoperative PTH and serum calcium levels. However, this modality may assist in intra-operative PG identification during a total thyroidectomy.

Identification of inadvertently removed parathyroid glands during thyroid surgery using autofluorescence

Background

Incidental excision of parathyroid glands is a common event during thyroid surgery and in spite the divergent results that can be obtained from the literature about its clinical significance, all efforts must be used to their preservation. Due to the autofluorescence emitted by parathyroid glands, authors began to use a custom device to inspect thyroidectomy specimens for incidentally removed parathyroid tissue; the results of using this device are presented in this manuscript.

Methods

Specimens of 40 consecutive thyroid surgeries were inspected. Localization of suspect high-fluorescence spots were recorded for confirmation with a pathological exam. Determinations of calcium and parathyroid hormone (PTH) were completed prior to surgery and at 24 hours and 15 days after the operation.

Results

Patient age ranged from 36 to 83 years and were predominantly female (82.5%). Calcium values at 24 hours post-operation varied between 7.1 and 9.5. The PTH values ranged between 3 and 77. Thirteen patients (32.5%) presented with biochemical hypocalcemia at 24 hours. At 15 days after the operation, only one patient presented with a calcium value below 8 (PTH: 10.9) with complete normalization 6 months after the surgery. Pathological examination identified eight parathyroid fragments in seven patients. There was no correlation between the presence of parathyroid tissue in the specimen and post-operative hypocalcemia (P=0.254). Eight suspicious areas of augmented fluorescence where detected; seven were coincident with the pathological examination and one was a false positive. One intrathyroidal gland was not identified, resulting a sensitivity of 87.5% and specificity 96.2%.

Conclusions

Although no correlation between incidental parathyroidectomy and hypocalcemia was demonstrated, autofluorescence may be a useful tool for in-table identification of incidentally-removed glands.