Impact of autofluorescence-based identification of parathyroids during total thyroidectomy on postoperative hypocalcemia: a before and after controlled study

Near-Infrared Autofluorescence Signatures of Single- vs Multigland Disease in Primary Hyperparathyroidism

Importance

The success of parathyroidectomy depends on accurate intraoperative localization and identification of all diseased glands in parathyroid exploration based on surgeon expertise to prevent persistent hyperparathyroidism. Near-infrared autofluorescence (NIRAF) imaging has recently emerged as a promising adjunctive intraoperative tool for localizing parathyroid glands; however, its potential utility in the assessment of parathyroid glands has yet to be established.

Objective

To analyze the differences in NIRAF signatures of parathyroid glands in single vs multiple glands in primary hyperparathyroidism (pHPT).

Design, Setting, and Participants

This prospective diagnostic study analyzed in vivo NIRAF images of parathyroid glands obtained during parathyroidectomies between November 18, 2019, and December 31, 2023, at a single tertiary referral center. Pixel intensities of the images were measured using third-party software. Patients who underwent parathyroidectomy for sporadic pHPT using a second-generation NIRAF imaging device were included. Patients with multiple endocrine neoplasm disorders were excluded. In vivo NIRAF images obtained during the procedures were analyzed.

Exposure

Near-infrared autofluorescence imaging during parathyroidectomy.

Main Outcomes and Measures

The primary outcomes were the autofluorescence intensity and heterogeneity of single adenomas and multigland disease (ie, double adenomas and 3- or 4-gland hyperplasia) in sporadic pHPT. Normalized autofluorescence intensity was calculated by dividing the mean pixel intensity of the parathyroid gland by the background tissue. A heterogeneity index was calculated by dividing the standard deviation by the mean pixel intensity of the gland. The secondary outcome was the visibility of each parathyroid gland on NIRAF imaging before it became apparent to the naked eye during exploration.

Results

A total of 1287 in vivo NIRAF images obtained from 377 patients (median [IQR] age, 66 [56-73] years; 299 female [79.3%]) were analyzed. Of all patients, 230 (61.0%) had a single adenoma, 91 (24.1%) had double adenomas, and 56 (14.9%) had 3- or 4-gland hyperplasia. A mean (SD) of 3.4 (1.1) parathyroid glands were identified in the procedures. A comparison of 581 diseased glands (45.1%) and 706 normal glands (54.9%) showed a lower median normalized autofluorescence intensity of 2.09 (95% CI, 1.07-4.01) vs 2.66 (95% CI, 1.43-4.20; effect size = 0.36) and higher heterogeneity index of 0.18 (95% CI, 0.07-0.41) vs 0.11 (95% CI, 0.01-0.27; effect size = 0.45), respectively. Of diseased glands, single adenomas (233 [40.1%]) vs double adenomas (187 [32.2%]) and 3- or 4-gland hyperplasia (161 [27.7%]) had a lower median autofluorescence intensity of 1.92 (95% CI, 1.02-4.44) vs 2.22 (95% CI, 1.10-3.97; effect size = 0.21), respectively. On receiver operating characteristic analysis, the optimal autofluorescence intensity threshold to differentiate between single adenomas vs multigland disease was 2.14, with a sensitivity of 64.4%, specificity of 58.1%, and area under the curve of 0.626.

Conclusions and Relevance

These findings suggest that parathyroid glands in single- vs multigland disease may exhibit different autofluorescence characteristics. Although the effect size was modest, the differences identified should be kept in mind when assessing the parathyroid glands during surgical exploration.

Analysis of near-infrared autofluorescence imaging for detection of inadvertently resected parathyroid glands after endoscopic thyroidectomy

BACKGROUND

Preserving parathyroid function during thyroidectomy is crucial, but remains challenging. Real-time near-infrared autofluorescence (NIRAF) aids surgeons in intraoperative parathyroid gland (PTG) identification. However, its role in detecting PTGs unintentionally removed during surgery is unclear.

STUDY DESIGN

This prospective study included adult patients undergoing endoscopic thyroidectomy. Surgeons identified and documented PTGs visually. Excised specimens underwent visual inspection and NIRAF imaging (PDE-Neo II). All fluorescent tissues were dissected and pathologically evaluated (reference standard). One scanned image per lobe was chosen to quantify autofluorescence (AF) intensity.

RESULTS

Overall, 95 patients underwent endoscopic thyroidectomies, with NIRAF imaging applied to 152 excised lobes. Of these, 19 lobes displayed a total of 23 spots with increased intensity. 175 specimens were sent for pathological evaluation, and 7 were confirmed to be parathyroid tissue. NIRAF demonstrated 100.0 % sensitivity and 90.5 % specificity for predicting parathyroid tissue, with 30.4 % positive predictive value, 100.0 % negative predictive value of and 90.9 % accuracy. Quantitatively normalized, the AF signal intensity was significantly higher in NIRAF-positive tissues than negative (4.3 vs 1.2 times, p < 0.0001). Additionally, the AF signal intensity in regions pathologically confirmed of parathyroid tissue was higher than non-parathyroid tissue (9.1 vs 2.1 times, p < 0.0001).

CONCLUSION

This study suggests that NIRAF has high sensitivity and specificity for detecting inadvertently resected PTGs after endoscopic thyroidectomy, contributing to preservation efforts. However, NIRAF-positive tissues still require additional confirmation through multiple methods, emphasizing other examinations to verify that they are indeed parathyroid tissues. Further research is warranted to refine NIRAF imaging parameters.

Correlation Between Near-Infrared Autofluorescence Properties and Sestamibi Uptakes of Parathyroid Glands in Primary Hyperparathyroidism

OBJECTIVE

Near-infrared autofluorescence (NIRAF) characteristics of parathyroid glands in primary hyperparathyroidism (pHPT) vary, with unclarity regarding the underlying mechanism. Similarly, 99mTc-sestamibi uptake in diseased parathyroid glands is variable. There is a suggestion that oxyphilic cell content may influence both imaging modalities. This study aims to analyze the relationship between NIRAF imaging characteristics, 99mTc-sestamibi uptake, and cellular composition in pHPT.

STUDY DESIGN

Retrospective analysis of an Institutional Review Board-monitored prospective database.

SETTING

Single tertiary referral center.

METHODS

NIRAF characteristics of parathyroid glands of patients with pHPT between 2019 and 2024 were compared with 99mTc-sestamibi scan findings from a prospective database. Using third-party software, brightness intensity and heterogeneity index (HI) of the glands were calculated. A subgroup of parathyroid glands obtained from consecutive patients with pHPT in 2020 to 2021 underwent histological analysis.

RESULTS

A total of 428 patients with 638 diseased parathyroid glands were analyzed. Forty-seven percent of the glands showed an uptake on 99mTc-sestamibi scans. The brightness intensity of the NIRAF signals from parathyroid glands that were seen versus not seen on sestamibi was 2.1 versus 2.3 (P = .002) and HI 0.18 versus 0.17 (P = .35), respectively. On multivariate analysis, low autofluorescence intensity, high gland volume, and single adenoma were associated with detectability on 99mTc-sestamibi scan (P < .0001). Intraglandular adipose tissue content was lower in diseased glands that were detected on 99mTc-sestamibi scans (0% vs 5%, P < .0001).

CONCLUSION

Our findings indicate an inverse relationship between autofluorescence intensity and detectability on 99mTc-sestamibi scans and a lack of correlation between different cell types and autofluorescence properties.

Impact of autofluorescence-guided surgery of parathyroid glands during total thyroidectomy in experienced surgeons: A randomized clinical trial

INTRODUCTION

Post-surgical hypoparathyroidism often occurs after total thyroidectomy (TT). The aim of this study is to investigate whether the use of near-infrared autofluorescence (NIRAF) of parathyroid glands (PGs) can aid experienced surgeons in identifying more PGs during surgery, potentially reducing unintended resection, and assessing its impact on post-surgical hypoparathyroidism.

MATERIALS AND METHODS

All patients undergoing at least a TT by two experienced surgeons, between 2020 and 2021, were enrolled and randomized into two cohorts: NIRAF group (NG) and CONTROL group (CG). Transient hypoparathyroidism was defined by serum concentration of PTH<12 ng/mL at the 1st post-operative day and permanent by the need of calcium-active vitamin D treatment >6 months from the surgery with still undetectable PTH or <12 ng/m.

RESULTS

Among 236 patients (111 in NG, 125 in CG), the number of PGs identified was higher in NG (93.9%, 417/444) compared to CG (81.4%, 407/500) (p < 0.001), with a mean of 3.76 ± 0.44 PGs per patient in NG and 3.25 ± 0.79 in CG. The number of unintendedly resected PGs was 14 in NG and 42 in CG (p < 0.0001). Transient hypoparathyroidism was observed in 18 patients (16.2%) in NG and 40 patients (32.0%) in CG (p = 0.004). Permanent hypoparathyroidism affected 1 patient in NG and 7 patients in CG (p = 0.06). The mean operative time was longer in NG (104.3 ± 32.08 min) compared to CG (85.5 ± 40.62 min) (p < 0.001).

CONCLUSIONS

NIRAF enhances the identification of PGs, preventing their inadvertent resection and reducing the overall incidence of post-surgical hypoparathyroidism.

Autofluorescence-Guided Total Thyroidectomy in Low-Volume, Nonparathyroid Institutions

Importance

Hypoparathyroidism following thyroid surgery is a serious complication that occurs frequently when surgery is performed by low-volume thyroid surgeons without experience in parathyroid surgery.

Objective

To evaluate the occurrence of hypoparathyroidism following total thyroidectomy after the introduction of autofluorescence in low-volume, nonparathyroid institutions.

Design, Setting, and Participants

This prospective, multicenter cohort study, with a follow-up period of up to 1 year, was conducted in Denmark at 2 low-volume nonparathyroid institutions between January 2021 and November 2023. All adult patients referred for total thyroidectomy were assessed for eligibility (n = 90). Only patients with no history of thyroid surgery were considered (n = 89). Patients who only underwent lobectomy (n = 6) or declined to participate (n = 5) were excluded. All included patients completed follow-up. The prospective cohort was compared with a historical cohort of successive patients undergoing primary total thyroidectomy from 2016 to 2020 (before autofluorescence was available).

Intervention

Included patients underwent autofluorescence-guided total thyroidectomy.

Main outcomes and Measures

Rate of hypoparathyroidism. Immediate hypoparathyroidism was defined as the need for active vitamin D postoperatively, whereas permanent hypoparathyroidism was considered when there still was a need for active vitamin D 1 year after surgery.

Results

Seventy-eight patients underwent autofluorescence-guided surgery (mean [SD] age, 55.6 [13.1] years; 67 [86%] female) and were compared with 89 patients in the historical cohort (mean [SD] age, 49.7 [12.8] years; 78 [88%] female). The rate of immediate hypoparathyroidism decreased from 37% (95% CI, 27%-48%) to 19% (95% CI, 11%-30%) after the introduction of autofluorescence (P = .02). Permanent hypoparathyroidism rates decreased from 32% (95% CI, 22%-42%) to 6% (95% CI, 2%-14%) (P < .001), reaching 0% at the end of the study. More parathyroid glands were identified with autofluorescence (75% [95% CI, 70%-80%] vs 61% [95% CI, 56%-66%]) (P < .001) and less parathyroid glands were inadvertently excised (4% [95% CI, 1%-11%] vs 21% [95% CI, 13%-31%]) (P = .001).

Conclusions and Relevance

In this cohort study of autofluorescence-guided thyroid surgery in low-volume, nonparathyroid institutions, the use of autofluorescence was associated with a significant decrease in both immediate and permanent hypoparathyroidism. When autofluorescence was used, hypoparathyroidism rates were comparable with those of high-volume surgeons who also perform parathyroid surgery.

Real-time imaging of ipsilateral parathyroid glands by retrograde injection of methylene blue into the superior thyroid artery: a new intraoperative parathyroid protection method

BACKGROUND

Postoperative hypoparathyroidism caused by parathyroid injury is a problem faced by thyroid surgeons. The current technologies for parathyroid imaging all have some defects.

METHODS

Patients with differentiated thyroid carcinoma (DTC) who underwent unilateral thyroidectomy plus ipsilateral central lymph node dissection were recruited. We dissected the main trunk of the superior thyroid artery entering the thyroid gland and placed the venous indwelling tube into the artery. The sensitivity, specificity, accuracy, positive predictive value (PPV) and negative predictive value (NPV) were calculated.

RESULTS

A total of 132 patients enrolled in this single-arm clinical trial, 105 of them completed retrograde catheterization via the superior artery. The sensitivity was 69.23 and 83.33% respectively. The specificity was 72.91 and 64.89%. The accuracy was 72.91 and 64.89%. The PPV was 85.71 and 81.08%. The NPV was 22.58 and 45.45%. There were no patients with allergic reactions to the methylene blue, or methylene blue toxicity.

CONCLUSIONS

Retrograde injection of methylene blue via the superior thyroid artery is an effective and safe method to visualize parathyroid glands. This method can accurately locate the target organ by ultraselecting the blood vessel and injecting the contrast agent while avoiding background contamination and reducing the amount of contrast agent.

TRIAL REGISTRATION

Clinical trial registration numbers and date of registration: ChiCTR2300077263、02/11/2023.

Autofluorescence-guided hemithyroidectomy in a low-volume thyroid institution with no experience in parathyroid surgery: randomized clinical trial

BACKGROUND

Recent studies suggest that low-volume surgeons with no experience in parathyroid surgery are at increased risk of causing parathyroid gland damage during thyroid surgery. The aim of this RCT was to evaluate the impact of using autofluorescence in hemithyroidectomy on parathyroid gland identification and preservation in a low-volume institution with no experience in parathyroid surgery.

METHODS

Patients referred for hemithyroidectomy were randomized 1 : 1 to either autofluorescence-guided hemithyroidectomy (the near-infrared autofluorescence group) or conventional hemithyroidectomy (the control group). The primary outcome was parathyroid gland identification rate. Secondary outcomes were the rate of parathyroid gland autotransplantation and the rate of inadvertent parathyroid gland excision.

RESULTS

A total of 170 patients were randomized to either autofluorescence-guided hemithyroidectomy (84 patients) or conventional hemithyroidectomy (86 patients). In the near-infrared autofluorescence group, 81.0% of parathyroid glands were identified, compared with 57.0% in the control group (P < 0.001). Autofluorescence enabled parathyroid gland visualization before the naked eye in 46.3% of cases. Surgeons had lower confidence in the parathyroid gland identification process in the control group than in the near-infrared autofluorescence group (59.1% versus 87.5% respectively; P < 0.001). In the near-infrared autofluorescence group, the parathyroid gland autotransplantation rate was initially high, but declined over time. There was no difference in the rate of inadvertent parathyroid gland excision.

CONCLUSION

Autofluorescence guidance significantly improved the parathyroid gland identification rate in hemithyroidectomy in a low-volume institution with no experience in parathyroid surgery and provided an increase in surgical confidence. The pattern of parathyroid gland autotransplantation in autofluorescence-guided surgery indicates the presence of a learning curve.

REGISTRATION NUMBER

NCT05044351 (http://www.clinicaltrials.gov).

Intraoperative strategies in identification and functional protection of parathyroid glands for patients with thyroidectomy: a systematic review and network meta-analysis

BACKGROUND

This study aimed to assess the benefits and limitations of four intraoperative visualization of parathyroid gland (IVPG) strategies in the identification and functional protection of parathyroid glands (PGs).

METHODS

We searched PubMed, the Cochrane Central Register of Controlled Trials, CNKI, EMBASE, Web of Science and Google Scholar databases until 30 June 2023. Four IVPG strategies were composed of the naked eyes (NE) and three imaging strategies: autofluorescence (AF), indocyanine green fluorescence (ICGF), and carbon nanoparticles (CN). We performed a pairwise meta-analysis (PMA) for direct comparisons and a Bayesian network meta-analysis (NMA) for indirect comparisons.

RESULTS

A total of 29 eligible studies were included. According to NMA and PMA, AF had significantly lower rates of postoperative hypocalcemia and hypoparathyroidism, PG inadvertent resection, and PG auto-transplantation compared to NE, while had significantly higher rate of PG identification. CN showed significantly lower rates of postoperative hypocalcemia and hypoparathyroidism, and PG inadvertent resection compared to NE in PMA and NMA. ICGF showed a significantly higher rate of PG auto-transplantation compared to NE in PMA and AF in NMA. According to SUCRA values, AF showed the best advantage in reducing the rate of postoperative hypocalcemia (0.85) and PG inadvertent resection (0.89), and increasing the rate of PG identification (0.80). CN had the greatest advantage in reducing the rate of postoperative hypoparathyroidism (0.95). ICGF ranked the highest in the rate of PG auto-transplantation (0.98).

CONCLUSIONS

Three imaging strategies demonstrate significant superiority over NE in the intraoperative PG identification and functional protection. AF is the best strategy in reducing the incidence of postoperative hypocalcemia, increasing the rate of PG identification, and reducing the rate of PG inadvertent resection and auto-transplantation. ICGF has great value in assessing PG viability, leading to the trend towards PG auto-transplantation. CN is the best strategy in reducing the incidence of postoperative hypoparathyroidism.

Autofluorescence of Parathyroid Glands: A Review of Methods of Parathyroid Gland Identification and Parathyroid Vascular Assessment

Postoperative hypoparathyroidism may cause significant patient morbidity and even mortality. Emerging technologies centered on autofluorescent properties of parathyroid glands when exposed to near-infrared light hold promise to improve surgical parathyroid gland identification and preservation. Two systems (probe-based and camera-based) are commercially available currently; however, neither system alone provides indication of vascular viability or postoperative parathyroid gland function. The administration of indocyanine green, when combined with near-infrared fluorescence imaging, enables subjective assessment of parathyroid gland perfusion. Additional technologies to assess parathyroid gland perfusion are being developed. The impact of these nascent technologies on relevant clinical outcomes is an area of active investigation.

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.

Hypoparathyroidism following total thyroidectomy: high rates at a low-volume, non-parathyroid institution

Background

Hypoparathyroidism following total thyroidectomy is globally the most common complication to thyroid surgery. The reported complication rates vary widely and might be highly dependent on the surgical experience. In this study we aimed to evaluate the rate of hypoparathyroidism following primary total thyroidectomy at a low-volume institution that only performs thyroid surgery and does not have any experience with parathyroid surgery.

Methods

Retrospective cohort study. All patients undergoing primary total thyroidectomy at the ENT-Department, Goedstrup Hospital, Denmark, over a 5-year period (2016-2020) were identified through the procedure codes for total thyroidectomy. Medical records, pathology reports, biochemical and medical histories were fully assessed for each patient. The primary endpoint was the rate of hypoparathyroidism- both immediate and permanent. Secondary outcomes were parathyroid gland identification rates, rates of parathyroid gland autotransplantation, and rates of inadvertent parathyroid gland excision.

Results

A total of 89 patients were included in the final analysis. A total of 33 patients (37.1%) experienced immediate hypoparathyroidism following surgery, while 30 patients (33.7%) still were on active vitamin D two months postoperatively. One year following surgery, 28 patients (31.5%) were still on active vitamin D and were considered as having permanent hypoparathyroidism. Sixty-one percent of the parathyroid glands were identified intraoperatively, and 19% of the patients experienced parathyroid autotransplantation. Inadvertent parathyroid gland excision occurred for 21% of the patients and was associated with a significantly increased risk of permanent hypoparathyroidism (RR = 2.99; 95% CI: 1.36 - 6.62, p = 0.005).

Conclusion

Both transient and permanent hypoparathyroidism following total thyroidectomy at a low-volume, non-parathyroid institution occurred with much higher frequencies than previously reported. The elevated rates were most likely due to the low-volume, non-parathyroid nature of the surgeons which in part was mirrored in low parathyroid gland identifications rates, and high rates of autotransplantation and inadvertent parathyroid gland excision.

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.

An update on the use of near-infrared autofluorescence imaging in endocrine surgical procedures

Over the past decade, near-infrared autofluorescence (NIRAF) imaging has been a major breakthrough in endocrine surgery. Although initial focus was directed at the parathyroid glands, subsequent work has also shown that non-parathyroid neuroendocrine tumors also possess autofluorescence properties. The aim of this review is to present an update and synopsis about NIRAF applications in various endocrine surgical procedures. Methodology includes a review of the literature supplemented with expert opinion. Overall, our review reveals that the use of NIRAF may provide the surgeon with adjunctive critical information that has the potential to change the conduct of many various endocrine surgical procedures.

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.

The utility of parathyroid autofluorescence as an adjunct in thyroid and parathyroid surgery 2023

Thyroid and parathyroid surgery requires careful dissection around the vascular pedicle of the parathyroid glands to avoid excessive manipulation of the tissues. If the blood supply to the parathyroid glands is disrupted, or the glands are inadvertently removed, temporary and/or permanent hypocalcemia can occur, requiring post-operative exogenous calcium and vitamin D analogues to maintain stable levels. This can have a significant impact on the quality of life of patients, particularly if it results in permanent hypocalcemia. For over a decade, parathyroid tissue has been noted to have unique intrinsic properties known as "fluorophores," which fluoresce when excited by an external light source. As a result, parathyroid autofluorescence has emerged as an intra-operative technique to help with identification of parathyroid glands and to supplement direct visualization during thyroidectomy and parathyroidectomy. Due to the growing body of literature surrounding Near Infrared Autofluorescence (NIRAF), we sought to review the value of using autofluorescence technology for parathyroid detection during thyroid and parathyroid surgery. A literature review of parathyroid autofluorescence was performed using PubMED. Based on the reviewed literature and expert surgeons' opinions who have used this technology, recommendations were made. We discuss the current available technologies (image vs. probe approach) as well as their limitations. We also capture the opinions and recommendations of international high-volume endocrine surgeons and whether this technology is of value as an intraoperative adjunct. The utility and value of this technology seems promising and needs to be further defined in different scenarios involving surgeon experience and different patient populations and conditions.

Feasibility of parathyroid gland autofluorescence imaging after indocyanine green fluorescence angiography

Background

In thyroid surgery, autofluorescence allows the parathyroid glands (PTGs) to be located very early to protect them. Moreover, indocyanine green (ICG) fluorescence angiography (ICG-FA) allows for assessing the viability of the PTGs and identifying blood vessels to preserve them. The main limitation of using ICG-FA is that once ICG has been injected, it is no longer possible to observe PTG autofluorescence using existing devices. This study aimed to describe an approach that allows for visualization of the PTGs by autofluorescence, even after ICG injection.

Methods

We redesigned the FLUOBEAM® LX system to excite fluorescence at 685 nm and detect fluorescence between 700 and 900 nm. This device had short-pass filters at 775 nm that helped to split the contributions of the PTG autofluorescence and ICG fluorescence. Tests were performed on extemporaneous PTG preparations placed next to ICG droplets to assess for rejection of the ICG signal.

Results

A low-pass filter at 775 nm detected 60% of the autofluorescence signals and 10% of the ICG signals.

Conclusion

These findings support the possibility of visualizing PTG autofluorescence despite multiple ICG injections and measuring the balance between ICG and autofluorescence signals.

Accidental parathyroidectomy during total thyroidectomy and hypoparathyroidism in a large series of 766 patients: incidence and consequences in a referral center

PURPOSE

Transient hypoparathyroidism is the most common complication after total thyroidectomy, and accidental parathyroidectomy (AP) may be a cause. The aim of this study was to investigate the incidence of AP and its impact on postoperative calcemia.

MATERIALS AND METHODS

From February 2016 to May 2018, 766 patients undergoing total thyroidectomy were prospectively included. Surgical indications, hormonal status, definitive histology, and postoperative calcium and PTH levels were analyzed.

RESULTS

578/(75.45%) were women and 188/(24.55%) men with mean age of 53.4 years. Parathyroid tissue on the thyroid specimen was observed in 40 (5.2%) patients: 30 APs and 10 parathyroid fragments. Among the 30 APs, 12 glands were intrathyroid and 18 (2.3%) in eutopic location. 97 (12.6%) patients were treated for postoperative hypocalcemia: 90 (11.7%) had transient and 5 (0.6%) definitive hypoparathyroidism; 2 were lost in follow-up. 13/30 (43.3%) with AP had transient hypoparathyroidism. A strong correlation was found (p < 0.0001) between AP and postoperative hypocalcemia. 1/30 (3.3%) patient with APs had definitive hypoparathyroidism. Transient and persistent nerve palsies were found in 10 (1.3%) and 3 (0.4%) patients, respectively.

DISCUSSION

A careful examination of the thyroid gland after resection help to identify an AP that could be autotransplanted. Surgeon and hospital activity volume per years seem to reduce the risk of hypoparathyroidism.

CONCLUSION

Total thyroidectomy and intrathyroid localization of parathyroid glands are risk factors for the AP. The incidence of AP was 2.3%, and this remains low due to our longstanding experience in thyroid and parathyroid surgery.

New Techniques for Intraoperative Parathyroid Localization

Accurate identification of abnormal parathyroid glands (PGs) during parathyroidectomy and thyroidectomy can be challenging even for experienced surgeons given PGs variable location, size, and similar appearance to surrounding tissue. Inadvertent removal or devascularization of healthy PGs can lead to transient or permanent hypoparathyroidism. Permanent hypoparathyroidism is associated with increased rates of renal insufficiency, seizures, skeletal abnormalities, increased costs, decreased quality of life, and increased mortality. Conversely, the inability to identify and remove hyperfunctioning PGs results in failed parathyroidectomy which can result in need for reoperations that are associated with increased technical difficulty, operative duration, rates of hypoparathyroidism and recurrent laryngeal nerve damage, and cost.

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.

Converting a probe-based fluorescence system into an easy-to-use adjunct for the detection of parathyroid glands accidentally resected intraoperatively

PURPOSE

The reported threshold of a near-infrared fluorescence detection probe (FDP) for judging parathyroid glands (PGs) is based on the autofluorescence intensity relative to other non-PG tissues, making it unreliable when not enough reference tissues are measured. We aim to convert FDP into a more convenient tool for identifying accidentally resected PGs by quantitative measurements of autofluorescence in resected tissues.

METHODS

It was a prospective study approved by the Institutional Review Board. The research was divided into two stages: (1) In order to calibrate the novel FDP system, autofluorescence intensity of different in / ex vivo tissues was measured and the optimal threshold was obtained using receiver operating characteristic (ROC) curve. (2) To further validate the effectiveness of the new system, detection rates of incidental resected PGs by pathology in the control group and by FDP in the experimental group were compared.

RESULTS

Autofluorescence of PGs was significantly higher than that of non-PG tissue (43 patients, Mann-Whitney U test, p < 0.0001). An optimal threshold of sensitivity / specificity (78.8% and 85.1%) for discriminating PGs was obtained. The detection rates of experimental group (20 patients) and control group (33 patients) are 5.0% and 6.1% respectively (one-tailed Fisher's exact test, p = 0.6837), indicating the novel FDP system can achieve a similar proportion of PG detection compared with pathological examinations.

CONCLUSIONS

The novel FDP system can be used as an easy-to-use adjunct for detecting PG accidentally resected intraoperatively before the tissues are sent for frozen sections during thyroidectomy surgeries.

TRIAL REGISTRATION

Registration number: ChiCTR2200057957.

Modern Surgical Techniques of Thyroidectomy and Advances in the Prevention and Treatment of Perioperative Complications

Thyroid cancer is the most common cancer of the endocrine system, and, in recent years, there has been a phenomenon of overdiagnosis followed by subsequent overtreatment. This results in an increasing number of thyroidectomy complications being faced in clinical practice. In this paper, we present the current state of knowledge and the latest findings in the fields of modern surgical techniques, thermal ablation, the identification and assessment of parathyroid function, recurrent laryngeal nerve monitoring and treatment and perioperative bleeding. We reviewed 485 papers, from which we selected 125 papers that are the most relevant. The main merit of this article is its comprehensive view of the subject under discussion-both general, concerning the selection of the appropriate method of surgery, and particular, concerning the selection of the appropriate method of prevention or treatment of selected perioperative complications.

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.

Recent Advances in the Surgical Management of Thyroid Cancer

A growing incidence of differentiated thyroid cancer (DTC) has been reported in most developed countries, corresponding mainly to incidentally discovered small papillary thyroid carcinomas. Given the excellent prognosis of most patients with DTC, optimal therapeutic management, minimizing complications, and preserving patient quality of life are essential. Thyroid surgery has a central role in both the diagnosis, staging, and treatment of patients with DTC. Thyroid surgery should be integrated into the global and multidisciplinary management of patients with DTC. However, the optimal surgical management of DTC patients is still controversial. In this review article, we discuss the recent advances and current debates in DTC surgery, including preoperative molecular testing, risk stratification, the extent of thyroid surgery, innovative surgical tools, and new surgical approaches.

Central node dissection in papillary thyroid carcinoma in the era of near-infrared fluorescence

The most common site of lymph node metastases in papillary thyroid carcinoma is the central compartment of the neck (level VI). In many patients, nodal metastases in this area are not clinically apparent, neither on preoperative imaging nor during surgery. Prophylactic surgical clearance of the level VI in the absence of clinically suspicious lymph nodes (cN0) is still under debate. It has been suggested to reduce local recurrence and improve disease-specific survival. Moreover, it helps to accurately diagnose the lymph node involvement and provides important staging information useful for tailoring of the radioactive iodine regimen and estimating the risk of recurrence. Yet, many studies have shown no benefit to the long-term outcome. Arguments against the prophylactic central lymph node dissection (CLND) cite minimal oncologic benefit and concomitant higher operative morbidity, with hypoparathyroidism being the most common complication. Recently, near-infrared fluorescence imaging has emerged as a novel tool to identify and preserve parathyroid glands during thyroid surgery. We provide an overview of the current scientific landscape of fluorescence imaging in thyroid surgery, of the controversies around the prophylactic CLND, and of fluorescence imaging applications in CLND. To date, only three studies evaluated fluorescence imaging in patients undergoing thyroidectomy and prophylactic or therapeutic CLND for thyroid cancer. The results suggest that fluorescence imaging has the potential to minimise the risk of hypoparathyroidism associated with CLND, while allowing to exploit all its potential benefits. With further development, fluorescence imaging techniques might shift the paradigm to recommend more frequently prophylactic CLND.

The Utility of Near-Infrared Autofluorescence for Parathyroid Gland Identification During Thyroid Surgery: A Single-Center Experience

Parathyroid gland injury during thyroid surgery is common and can lead to postoperative hypocalcemia. This study aims to determine the utility of near-infrared autofluorescence (NIRAF) technology for parathyroid gland identification in thyroid surgery. A prospective case series of patients who underwent thyroid surgery between March and June 2021 were examined. Following intra-operative visualisation, parathyroid glands and surrounding tissues were exposed to near-infrared light with a wavelength of approximately 800 nm using the Storz® Near-Infrared Range/Indocyanine Green (NIR/ICG) endoscopic system. Parathyroid glands were expected to show autofluorescence following exposure. Twenty patients who underwent thyroid surgery were included. Eighteen patients (90%) were female, with a median age of 50.0 (IQR 41.0 - 62.5). Surgeries performed include hemithyroidectomy (9 patients; 45.0%), total thyroidectomy (8 patients; 40.0%), completion thyroidectomy (2 patients; 10.0%) and right inferior parathyroidectomy (1 patient; 5.0%). Attempts were made to identify 56 parathyroid glands in this case series. There were 46/56 (82.1%) surgeon-identified parathyroid glands through direct visualisation. Using NIRAF technology, 39/46 (84.8%) were identified as parathyroid glands. There was no inadvertent resection of parathyroid glands or post-operative hypocalcaemia. NIRAF technology has the potential to be a useful tool in confirming the presence of parathyroid glands following direct visualisation intra-operatively.

Effect of near infrared autofluorescence guided total thyroidectomy on postoperative hypoparathyroidism: a randomized clinical trial

PURPOSE

The purpose of this single-blinded, 2-centre, randomized controlled trial was to test if near-infrared (NIR) autofluorescence image guidance for parathyroid gland (PG) detection during total thyroidectomy can reduce the incidence of hypoparathyroidism in both malignant and benign cases.

METHOD

Patients admitted for primary or completion total thyroidectomy were randomized to either the NIR intervention group or the standard care NONIR (no near infrared) group. The primary endpoint was the rate of hypoparathyroidism at the 3-month follow-up, defined as hypocalcemia and inappropriately low parathyroid hormone levels and/or continuous treatment with active vitamin D. The secondary endpoint was the PG identification rate.

RESULTS

A total of 147 patients were included of whom 73 were allocated to NIR. Primary or completion thyroidectomy was conducted in 84 and 63 cases, respectively. A total of 130 completed 3 months follow-up. Postoperative hypoparathyroidism in the NIR group at 12 h, 1 month and 3 months was, respectively, 31.8, 14.1, 6.5% compared with 35.9, 18.9, 11.8% in the NONIR group (all p > 0.46). In the NIR group, the identification rate of PGs was 69.5% (146 of 210 PGs), and 9% (19 of 210 PGs) were identified only due to additional use of NIR. For 15 out of 69 patients (21.7%) additionally PGs was found.

CONCLUSION

Hypoparathyroidism was nominally less frequent in the NIR group, although not statistically significant. Further studies are needed to confirm if NIR may be a supportive PG identification tool to minimize the number of PG which would have been otherwise missed, especially during more complicated thyroid procedures.

TRIAL REGISTRY

ClinicalTrials.gov: NCT04193332. Registration date: 16.08.2019.

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.

Intraoperative Autofluorescence Imaging for Parathyroid Gland Identification during Total Laryngectomy with Thyroidectomy

OBJECTIVE

Hypoparathyroidism is a known complication of total laryngectomy, although parathyroid preservation and/or reimplantation are not routine. Autofluorescence is a new technique for identifying parathyroid glands intraoperatively. The aim of this study was to evaluate the feasibility of autofluorescence in this context.

MATERIALS AND METHODS

A retrospective study of patients undergoing total laryngectomy/pharyngectomy with concomitant thyroidectomy using the Fluobeam^® (Fluoptics, Grenoble, France) and frozen section of a parathyroid fragment in case of reimplantation. The rates of identification using autofluorescence, reimplantation, and hypoparathyroidism were evaluated.

RESULTS

Eighteen patients (16 males, median age 67) underwent total laryngectomy/pharyngectomy with total thyroidectomy (n = 12) or hemithyroidectomy (n = 6). A median of 2 parathyroid glands were identified per patient. Ninety-two percent were identified by autofluorescence before visualisation. All parathyroids were reimplanted due to devascularization. Temporary hypoparathyroidism occurred in nine patients, and was permanent in one patient. After 34 months of median follow-up (range 1-49), no tumor recurrence was observed in the reimplantation sites.

CONCLUSIONS

To our knowledge, this is the largest study to evaluate autofluorescence during total laryngectomy with thyroidectomy. No tumor recurrence occurred in the sites of parathyroid reimplantation.

Indocyanine green fluorescence and near-infrared autofluorescence may improve post-thyroidectomy parathyroid function

BACKGROUND

Near-infrared autofluorescence and indocyanine green fluorescence are 2 recent tools introduced to improve postoperative parathyroid function during thyroid surgery.

METHODS

We conducted a randomized prospective study. Patients undergoing total thyroidectomy were randomly assigned either to the fluorescence group, in which near-infrared autofluorescence and indocyanine green fluorescence were used, or to the control group. The primary outcomes of the study were the rate of postoperative transient and symptomatic hypocalcemia.

RESULTS

A significantly higher number of parathyroid glands were identified in the fluorescence group (3.83 vs 3.64, P = .028). The rate of postoperative symptomatic hypocalcemia was significantly lower in the fluorescence group (6% vs 17%, P = .015), as was the dosage (1.53 vs 1.91 g, P = .007) and the duration of calcium therapy (32.30 vs 45.66 days, P = .003). Having at least 2 well-vascularized parathyroid glands correlates to lower rates of transient hypocalcemia (7.4% vs 21.9%, P = .037) as well as to higher serum calcium (8.70 vs 8.42 mg/dL, P = .027) and parathyroid hormone levels (19.15 vs 11.4 pg/mL, P = .0002) on postoperative day 1.

CONCLUSION

Near-infrared autofluorescence and indocyanine green fluorescence are novel tools that may support the endocrine surgeon in preserving and predicting post-thyroidectomy parathyroid gland function.

A multicenter evaluation of near-infrared autofluorescence imaging of parathyroid glands in thyroid and parathyroid surgery

BACKGROUND

The usefulness of incorporating near-infrared autofluorescence into the surgical workflow of endocrine surgeons is unclear. Our aim was to develop a prospective registry and gather expert opinion on appropriate use of this technology.

METHODS

This was a prospective multicenter collaborative study of patients undergoing thyroidectomy and parathyroidectomy at 7 academic centers. A questionnaire was disseminated among 24 participating surgeons.

RESULTS

Overall, 827 thyroidectomy and parathyroidectomy procedures were entered into registry: 42% of surgeons found near-infrared autofluorescence useful in identifying parathyroid glands before they became apparent; 67% correlated near-infrared autofluorescence pattern to normal and abnormal glands; 38% of surgeons used near-infrared autofluorescence, rather than frozen section, to confirm parathyroid tissue; and 87% and 78% of surgeons reported near-infrared autofluorescence did not improve the success rate after parathyroidectomy or the ability to find ectopic glands, respectively. During thyroidectomy, 66% of surgeons routinely used near-infrared autofluorescence to rule out inadvertent parathyroidectomy. However, only 36% and 45% felt near-infrared autofluorescence decreased inadvertent parathyroidectomy rates and improved ability to preserve parathyroid glands during central neck dissections, respectively.

CONCLUSION

This survey study identified areas of greatest potential use for near-infrared autofluorescence, which can form the basis of future objective trials to document the usefulness of this technology.

Etiology and Pathophysiology of Hypoparathyroidism: A Narrative Review

The approach utilized a systematic review of the medical literature executed with specifically designed criteria that focused on the etiologies and pathogenesis of hypoparathyroidism. Enhanced attention by endocrine surgeons to new knowledge about parathyroid gland viability are reviewed along with the role of intraoperative parathyroid hormone (ioPTH) monitoring during and after neck surgery. Nonsurgical etiologies account for a significant proportion of cases of hypoparathyroidism (~25%), and among them, genetic etiologies are key. Given the pervasive nature of PTH deficiency across multiple organ systems, a detailed review of the skeletal, renal, neuromuscular, and ocular complications is provided. The burden of illness on affected patients and their caregivers contributes to reduced quality of life and social costs for this chronic endocrinopathy. © 2022 The Authors. Journal of Bone and Mineral Research published by Wiley Periodicals LLC on behalf of American Society for Bone and Mineral Research (ASBMR).

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.

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.

Combined Use of Autofluorescence and Indocyanine Green Fluorescence Imaging in the Identification and Evaluation of Parathyroid Glands During Total Thyroidectomy: A Randomized Controlled Trial

Background and objectives

Accurate identification and evaluation of the parathyroid glands (PGs) intraoperatively is critical to reduce the incidence of postoperative hypoparathyroidism after total thyroidectomy. Near-infrared fluorescence imaging (NIFI), including the autofluorescence (AF) and indocyanine green fluorescence (ICGF) imaging, is a promising technique to protect PGs. This study aimed to assess whether the combined use of AF and ICGF could reduce the incidence of postoperative hypoparathyroidism and improve the identification and evaluation of PGs during total thyroidectomy.

Methods

This randomized controlled trial enrolled 180 patients who were randomized into two groups and underwent total thyroidectomy with unilateral or bilateral central lymph node dissection. In the control group, the PGs were identified and evaluated by the naked eye. In the NIFI group, AF was used to identify the PGs and ICGF was applied to assess the blood perfusion of the PGs in situ. The primary outcome was the incidence of postoperative hypoparathyroidism. The secondary outcomes included the number of identified PGs, autotransplanted PGs, and known preserved PGs in situ.

Results

The incidence of postoperative transient hypoparathyroidism was significantly lower in the NIFI group than in the control group (27.8% vs. 43.3%, P = 0.029). More PGs were identified in the NIFI group than in the control group (3.6 ± 0.5 vs. 3.2 ± 0.4, P < 0.001). No significant difference was observed in the number of autotransplanted PGs between the two groups (P = 0.134). Compared with the control group, a greater number of known PGs were preserved in situ in the NIFI group (1.3 ± 0.6 vs. 1.0 ± 0.5, P < 0.001). In the NIFI group, only 4.5% of the patients with at least one well-perfused PG (ICG score of 2) developed postoperative hypoparathyroidism, which was significantly lower than that of the control group (34.6%, P < 0.001).

Conclusion

Combined use of AF and ICGF during total thyroidectomy reduces the risk of transient postoperative hypoparathyroidism, enhances the ability to identify and preserve PGs, and improves the accuracy of evaluating the perfusion of PGs during surgery.

Clinical Trial Registration

Chinese Clinical Trial Register (www.chictr.org.cn), identifier ChiCTR2100045320. Registered on April 12, 2021.

[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.

A visual deep learning model to predict abnormal versus normal parathyroid glands using intraoperative autofluorescence signals

BACKGROUND

Previous work demonstrated that abnormal versus normal parathyroid glands (PGs) exhibit different patterns of autofluorescence, with former appearing darker and more heterogenous. Our objective was to develop a visual artificial intelligence model using intraoperative autofluorescence signals to predict whether a PG is abnormal (hypersecreting and/or hypercellular) or normal before excision during surgical exploration for primary hyperparathyroidism.

METHODS

A total of 906 intraoperative parathyroid autofluorescence images of 303 patients undergoing parathyroidectomy/thyroidectomy were used to develop model. Autofluorescence image of each PG was uploaded into the visual artificial intelligence platform as abnormal or normal. For deep learning, randomly chosen 80% of data was used for training, 10% for testing, 10% for validation. The area under the receiver operating characteristic (AUROC), area under the precision-recall curve (AUPRC), recall (sensitivity), and precision (positive predictive value) of the model were calculated.

RESULTS

AUROC and AUPRC of the model to predict normal and abnormal PGs were 0.90 and 0.93, respectively. Recall and precision of the model were 89% each.

CONCLUSION

Visual artificial intelligence platforms may be used to compare the autofluorescence signal of a given parathyroid gland against a large database. This may be a new adjunctive tool for intraoperative assessment of parathyroid glands during surgical exploration for primary hyperparathyroidism.

A Visual Deep Learning Model to Localize Parathyroid-Specific Autofluorescence on Near-Infrared Imaging : Localization of Parathyroid Autofluorescence with Deep Learning

BACKGROUND AND PURPOSE

Parathyroid glands may be detected by their autofluorescence on near-infrared imaging. Nevertheless, recognition of parathyroid-specific autofluorescence requires a learning curve, with other unrelated bright signals causing confusion. The aim of this study was to find out whether machine learning could be used to facilitate identification of parathyroid-specific autofluorescence signals on intraoperative near-infrared images in patients undergoing thyroidectomy and parathyroidectomy procedures.

METHODS

In an institutional review board-approved study, intraoperative near-infrared images of patients who underwent thyroidectomy and/or parathyroidectomy procedures within a year were used to develop an artificial intelligence model. Parathyroid-specific autofluorescence signals were marked with rectangles on intraoperative near-infrared still images and used for training a deep learning model. A randomly chosen 80% of the data were used for training, 10% for testing, and 10% for validation. Precision and recall of the model were calculated.

RESULTS

A total of 466 intraoperative near-infrared images of 197 patients who underwent thyroidectomy and/or parathyroidectomy procedures were analyzed. Procedures included total thyroidectomy in 54 patients, thyroid lobectomy in 24 patients, parathyroidectomy in 108 patients, and combined thyroidectomy and parathyroidectomy procedures in 11 patients. The overall recall and precision of the model were 90.5 and 95.7%, respectively.

CONCLUSIONS

To our knowledge, this is the first study that describes the use of artificial intelligence tools to assist in recognition of parathyroid-specific autofluorescence signals on near-infrared imaging. The model developed may have utility in facilitating training and decreasing the learning curve associated with the use of this technology.

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.

Preliminary experience with the EleVision IR system in detection of parathyroid glands autofluorescence and perfusion assessment with ICG

BACKGROUND

Postoperative hypoparathyroidism remains the most frequent complication of neck endocrine surgery. In order to reduce the incidence of this feared complication, several systems for imaging of near infrared autofluorescence (NIRAF) have been invented to help surgeons identify parathyroid glands (PTGs) and evaluate their vascularization. We evaluated the efficacy of the EleVision IR system in thyroid and parathyroid surgery.

METHODS

We used the EleVision IR system in 25 patients who underwent thyroid/parathyroid surgery or both at our institution between December 2020 and July 2021. At various stages of the surgery, the surgeon first looked for PTGs with the naked eye and then completed the visual inspection with NIRAF imaging. We then compared both the naked eye and NIRAF-supported PTGs detection rates. At the end of surgery, we performed indocyanine green angiography of PTGs in 17 patients.

RESULTS

In total, we identified 80% of PTGs: 65% with the naked eye only and additional 15% with the assistance of the EleVision IR system. 14 of 17 patients evaluated by ICG angiography had at least one well-vascularized PTG. Only one of these patients (a case of subtotal parathyroidectomy for tertiary hyperparathyroidism) developed symptomatic postoperative hypocalcemia despite a normal parathormone level. The three other patients had at least one remaining moderately-vascularized PTG and only one patient developed transient postoperative hypoparathyroidism.

CONCLUSION

We concluded that EleVision IR provides an efficient support for identification and evaluation of PTGs, and may be of great assistance in endocrine surgery. The images are easy to interpret even for less experienced surgeons thanks to the different types of color visualization and the possibility to measure the relative fluorescence intensity of PTGs and surrounding tissues.

Intraoperative Mapping Angiograms of the Parathyroid Glands Using Indocyanine Green During Thyroid Surgery: Results of the Fluogreen Study

BACKGROUND

During thyroid surgery, preservation of parathyroid gland (PG) feeding vessels is often impossible. The aim of the Fluogreen study was to determine the feasibility of using indocyanine green (ICG)-based intraoperative mapping angiograms of the PG (iMAP) to improve vascular preservation.

STUDY DESIGN

This prospective study enrolled all patients undergoing thyroid lobectomy or total thyroidectomy at the Hôpital Européen Marseille between September and December 2018. After exploring the thyroid lobe by autofluorescence to locate the PGs, ICG solution was injected intravenously to locate the PG feeding vessels and guide dissection. A second ICG injection was administered at the end of the lobectomy to assess perfusion of the PGs. The primary outcome was the quality of the angiogram, scaled as iMAP 0 (not informative), iMAP 1 (general vascular pattern visible but no clear vascular pedicle flowing into the PG), or iMAP 2 (clear vascular pedicle flowing into the PG). The secondary outcome was the PG perfusion score at the end of surgery, scaled from ICG 0 (no perfusion) to ICG 2 (intense uptake).

RESULTS

A total of 47 adult patients were analyzed, including 34 total thyroidectomies and 13 lobectomies. ICG angiography assessed 76 PGs, which were scored as iMAP 2 in 24 cases (31.6%), iMAP 1 in 46 (60.5%) and iMAP 0 in six (7.9%). At the end of dissection, the ICG perfusion score was significantly better for the PGs with informative angiography (iMAP 1 or 2), than for the PGs with uninformative angiography (iMAP 0), or the PGs not evaluated by vascular angiography (p < 0.05).

CONCLUSION

iMAP is feasible and provides direct vascular information in one-third of the cases. Further improvements to this technology are necessary, and the influence of this technique on patient outcomes during thyroidectomy will need to be further evaluated.

Methods of identification of parathyroid glands in thyroid surgery: A literature review

Intra-operative identification and preservation of parathyroid glands is an important but challenging aspect of thyroid surgery. Failure to do so may lead to transient or permanent hypocalcaemia, where the latter represents a serious complication causing life-long morbidity. It would be beneficial, therefore, if a simple and reliable modality can be developed to assist in the identification of parathyroid glands intra-operatively. The aim of this literature review is to provide an overview of intra-operative modalities used to identify parathyroid glands with a particular focus on near-infrared autofluorescence (NIRAF). Twenty-seven studies were considered relevant in this literature review. Several modalities have been used to aid parathyroid gland identification, including Raman spectroscopy, indocyanine green angiography, and NIRAF. NIRAF technology allows parathyroid glands to spontaneously give off light (autofluorescence) when exposed to near-infrared light at a wavelength of 785 nm, creating a contrast between tissues to allow intra-operative differentiation. Studies utilising NIRAF technology were able to identify 76.3%-100% of parathyroid glands intra-operatively. Furthermore, two randomised controlled trials comparing NIRAF and white light showed that the use of NIRAF was able to significantly increase the mean number of parathyroid glands detected and reduce the incidence of post-operative hypocalcaemia. NIRAF is an emerging tool that has been shown to increase the number of intra-operative parathyroid gland identification and reduce the rate of post-operative hypocalcaemia in a safe and reproducible manner. Future trials are needed to evaluate the real-life impact of NIRAF technology in outcomes of patients following thyroid surgery.

Fluorescence Image-Guided Surgery for Thyroid Cancer: Utility for Preventing Hypoparathyroidism

Background: Hypoparathyroidism is one of the most frequent complications of thyroid surgery, especially when associated with lymph node dissection in cases of thyroid cancer. Fluorescence-guided surgery is an emerging tool that appears to help reduce the rate of this complication. The present review aims to highlight the utility of fluorescence imaging in preserving parathyroid glands during thyroid cancer surgery. Methods: We performed a systematic review of the literature according to PRISMA guidelines to identify published studies on fluorescence-guided thyroid surgery with a particular focus on thyroid cancer. Articles were selected and analyzed per indication and type of surgery, autofluorescence or exogenous dye usage, and outcomes. The Methodological Index for Non-Randomized Studies (MINORS) was used to assess the methodological quality of the included articles. Results: Twenty-five studies met the inclusion criteria, with three studies exclusively assessing patients with thyroid cancer. The remaining studies assessed mixed cohorts with thyroid cancer and other thyroid or parathyroid diseases. The majority of the papers support the potential benefit of fluorescence imaging in preserving parathyroid glands in thyroid surgery. Conclusions: Fluorescence-guided surgery is useful in the prevention of post-thyroidectomy hypoparathyroidism via enhanced early identification, visualization, and preservation of the parathyroid glands. These aspects are notably beneficial in cases of associated lymphadenectomy for thyroid cancer.