Comparison of indocyanine green fluorescence and parathyroid autofluorescence imaging in the identification of parathyroid glands during thyroidectomy

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.

Methods for the identification and preservation of parathyroid glands in thyroid surgery: a narrative review

Background and Objective

Accurate intraoperative identification and viability assessment of the parathyroid glands (PGs) has always been a crucial but challenging aspect of thyroid surgery. The traditional method, naked-eye (NE) assessment, is significantly associated with the experience of the surgeon. Therefore, various methods have been developed to help surgeons protect PGs, with some benefits and limitations. Recently, near-infrared autofluorescence (NIRAF) and indocyanine green fluorescence imaging (ICGFI) have been demonstrated to be promising in the identification and viability assessment of PGs. Herein, we provide an overview of the methods of intraoperative identification and viability assessment of PGs, focusing on the application of NIRAF and ICGFI.

Methods

We performed a systematic literature search of PubMed, Medline, Cochrane Library databases, Web of Science, and EMBASE to identify all relevant studies published up to March 2023. The keywords were ((autofluorescence) OR (indocyanine green)) AND (parathyroid gland).

Key Content and Findings

In this narrative review, we summarized the benefits and limitations of intraoperative methods for PG identification and viability assessment, focusing on the application of NIRAF and ICGFI.

Conclusions

Intraoperative parathyroid protection methods have developed from traditional subjective identification of PGs to the latest near-infrared (NIR) fluorescence imaging technology. The discovery, development, and application of NIRAF and ICGFI have provided better ways for surgeons to protect PGs intraoperatively.

Why does diseased parathyroid appear weak or heterogenous intensity during intraoperative near-infrared autofluorescence?

Background

During intraoperative autofluorescence, the imaging intensity of diseased parathyroid glands is often lower than that of normal parathyroid glands, and some diseased glands especially those in secondary hyperparathyroidism (HPT) show heterogeneous intensities. This study aimed to investigate the reasons for these findings.

Methods

After formalin and paraffin fixation and bivalve cutting, 18 diseased glands from patients with primary HPT, 35 diseased parathyroid glands from patients with uremic HPT, and the surrounding thyroid and thymus tissues were measured using near-infrared autofluorescence with a Fluorobeam imaging system (Fluoptics, France). None of the tissues were stained with indocyanine green. Hematoxylin and eosin staining matched the intensity of the autofluorescence.

Results

Using the bright white intensity of the adult normal parathyroid gland as a reference (index score of 2), the chief cells and oxyphilic cell tissues of the diseased parathyroid had the same intensity score of 2 as that of the normal parathyroid gland, and the clear water parathyroid cell had a weaker intensity score (1-1.5). Their glandular architecture, including the trabecular, follicular, or solid arrangements, did not affect the level of intensity. The thymus, thyroid, fat, fibrosis, and necrosis had very low intensities (scores of 0). The red blood cell-hemorrhage appeared dark black (intensity score -1). The thickness of the fibrotic capsule varied in the diseased parathyroid glands; however, only a very thin capsule was observed in the normal parathyroid glands.

Conclusions

Various degrees of fibrotic capsules in the diseased parathyroid gland may be the main factor contributing to the lower intensity during autofluorescence, and different cell types, necrosis, fibrosis, and hemorrhage may explain the appearance of heterogeneous intensity in the diseased parathyroid glands.

Robot-Assisted Parathyroidectomy Using Indocyanine Green (ICG) Fluorescence in Primary Hyperparathyroidism

Background and Objectives: Surgical treatment for primary hyperparathyroidism (PHPT) has evolved from bilateral exploration through a long transcervical incision to focused parathyroidectomy with a minimal incision above the pathologic gland. Recently, endoscopic or robot-assisted parathyroid surgery without direct neck incision has been introduced. The aim of this study was to investigate the effectiveness of indocyanine green (ICG) fluorescence as a new method for the visual identification of abnormal hyperfunctioning parathyroid glands in robot-assisted parathyroidectomy using FireflyTM technology. We also aimed to conduct a comparative analysis between robot-assisted parathyroidectomy and conventional focused parathyroidectomy in order to identify clinical differences between the two surgical approaches. Materials and Methods: A total of 37 patients with PHPT underwent parathyroidectomy at a single university hospital between September 2018 and December 2022. Thirty-one patients underwent open focused parathyroidectomy (open group), and six patients underwent robot-assisted parathyroidectomy (robot group). Pre-operative localization via parathyroid SPECT-CT and an intraoperative parathyroid hormone (IOPTH) assay were used to successfully remove the pathologic parathyroid in both groups. ICG was administered only in the robot group. Results: Pathologic parathyroid showed a persistent fluorescence pattern under near-infrared vision. After the removal of the fluorescent parathyroid gland, IOPTH was normalized in all six patients in the robot group. However, the open group showed shorter hospital stays (1.8 ± 1.2 vs. 3.0 ± 0.0 days, p < 0.001) and shorter operation times (91.1 ± 69.1 vs. 152.5 ± 23.6 min, p = 0.001) than the robot group. After 6 months of surgery, PTH, calcium, and ionized calcium levels were all normalized without significant differences between the groups. Conclusions: Robot-assisted parathyroidectomy using ICG is helpful for the visual identification of the pathologic parathyroid gland. The advantage of robot parathyroidectomy is a better cosmetic outcome. However, it still does not show better clinical outcomes than conventional open focused parathyroidectomy.

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.

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.

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.

Use of fluorescence imaging and indocyanine green during thyroid and parathyroid surgery: Results of an intercontinental, multidisciplinary Delphi survey

BACKGROUND

In recent years, fluorescence imaging-relying both on parathyroid gland autofluorescence under near-infrared light and angiography using the fluorescent dye indocyanine green-has been used to reduce risk of iatrogenic parathyroid injury during thyroid and parathyroid resections, but no published guidelines exist regarding its use. In this study, orchestrated by the International Society for Fluorescence Guided Surgery, areas of consensus and nonconsensus were examined among international experts to facilitate future drafting of such guidelines.

METHODS

A 2-round, online Delphi survey was conducted of 10 international experts in fluorescence imaging use during endocrine surgery, asking them to vote on 75 statements divided into 5 modules: 1 = patient preparation and contraindications to fluorescence imaging (n = 11 statements); 2 = technical logistics (n = 16); 3 = indications (n = 21); 4 = potential advantages and disadvantages of fluorescence imaging (n = 20); and 5 = training and research (n = 7). Several methodological steps were taken to minimize voter bias.

RESULTS

Overall, parathyroid autofluorescence was considered better than indocyanine green angiography for localizing parathyroid glands, whereas indocyanine green angiography was deemed superior assessing parathyroid perfusion. Additional surgical scenarios where indocyanine green angiography was thought to facilitate surgery are (1) when >1 parathyroid gland requires resection; (2) during redo surgeries, (3) facilitating parathyroid autoimplantation; and (4) for the predissection visualization of abnormal glands. Both parathyroid autofluorescence and indocyanine green angiography can be used during the same procedure and employing the same imaging equipment. However, further research is needed to optimize the dose and timing of indocyanine green administration.

CONCLUSION

Though further research remains necessary, using fluorescence imaging appears to have uses during thyroid and parathyroid surgery.

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.

Indocyanine green fluorescence for parathyroid gland identification and function prediction: Systematic review and meta-analysis

BACKGROUND

To evaluate the diagnostic accuracies of indocyanine green (ICG) fluorescence for identifying parathyroid glands during surgery and predicting the postoperative function.

METHODS

From six databases, 21 studies were finally included in the study. True-positive, true-negative, false-positive, and false-negative data were extracted for the analysis. The quality of each study was analyzed using the QUADAS-2 tool.

RESULTS

The sensitivity of ICG-based parathyroid gland identification was 0.9380 (95% CI [0.9003, 0.9621]). The diagnostic odds ratio for ICG-based prediction of parathyroid gland function was 54.5652 [13.2059, 225.4570]. The area under the summary receiver operating characteristic curve was 0.909. Fluorescence intensity-based prediction presented higher diagnostic accuracy than that of score-based prediction. The incidence of postoperative hypoparathyroidism was higher in the group with a zero ICG score compared to the high scored group.

CONCLUSIONS

Identification of parathyroid gland and prediction of postoperative function using ICG are valuable to patients undergoing thyroidectomy or parathyroidectomy.

Hypoparathyroidism: Consequences, economic impact, and perspectives. A case series and systematic review

BACKGROUND

Postoperative hypoparathyroidism (PH) is the most common complication after total thyroidectomy. Incidence varies from 2% to 83%, depending on the definition.

OBJECTIVE

We performed a systematic review of the literature to determine the medico-economic effects of PH and update understanding of long-term consequences, morbidity, and quality of life related to hypoparathyroidism.

METHODS

We considered relevant articles published between 2000 and 2020 concerning long-term consequences of PH and quality of life. All studies concerning the medico-economic assessment of PH were included. We compared data from 2018 to results in the literature.

RESULTS

A proportion of 64/403 (16.8%) patients presented with transient PH during 2018, and 7/403 (1.7%) had permanent PH. Seven patients needed supplementation with alfacalcidol at 6-month follow-up. Factors predicting the need for alfacalcidol were age <45, thyroidectomy for goiter, and lymph node dissection. Additional therapy costs related to PH were €9781.10, and additional hospital costs were €230,400. We qualitatively synthesized 41 studies. Most were retrospective studies and only a few reported costs. No series assessed direct or indirect costs of postoperative PH.

CONCLUSION

To our knowledge, no previous studies reported the medico-economic impact of PH. Decreasing PH associated with fluorescence usage should be considered, particularly concerning cost-effectiveness.

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.

Can near-infrared autofluorescence imaging be used for intraoperative confirmation of parathyroid tissue?

BACKGROUND AND OBJECTIVES

Whether ex vivo autofluorescence (AF) imaging findings could be quantified to intraoperatively differentiate parathyroid tissue has not been reported. Our aim was to assess the ability of AF imaging to confirm parathyroid tissue during thyroidectomy and parathyroidectomy procedures.

METHODS

This was a retrospective Institutional Review Board-approved study. AF signals of specimens imaged ex vivo before submission to pathology during thyroidectomy and parathyroidectomy procedures were quantified. Using receiver operating characteristic (ROC) curves, optimal values for sensitivity/specificity to differentiate parathyroid tissue were calculated.

RESULTS

166 parathyroid and 217 non-parathyroid specimens were analyzed. With surgical drapes as background, the optimal normalized AF intensity threshold to predict parathyroid tissue on ROC curve analysis was 1.72 (86.1% sensitivity, 84.8% specificity, and area under the curve [AUC]: 0.919). The cutoff for 97% sensitivity was 1.31 and for 99.1% specificity was 3.16. With Telfa as background, the optimal threshold to predict parathyroid tissue was 1.46 (88.4% sensitivity, 76.8% specificity, and AUC: 0.896). The threshold for 96.8% sensitivity was 1.18 and for 98.8% specificity was 2.44. If thresholds for highest specificity were used, 40% of frozen sections to confirm parathyroid tissue could have been avoided.

CONCLUSION

Quantified brightness analysis of ex vivo AF signals may have utility in intraoperative differentiation of parathyroid tissue for 40% of surgical specimens.

Could fluorescence-guided surgery be an efficient and sustainable option? A SICE (Italian Society of Endoscopic Surgery) health technology assessment summary

BACKGROUND

Indocyanine green fluorescence vision is an upcoming technology in surgery. It can be used in three ways: angiographic and biliary tree visualization and lymphatic spreading studies. The present paper shows the most outstanding results from an health technology assessment study design, conducted on fluorescence-guided compared with standard vision surgery.

METHODS

A health technology assessment approach was implemented to investigate the economic, social, ethical, and organizational implications related to the adoption of the innovative fluorescence-guided view, with a focus on minimally invasive approach. With the support of a multidisciplinary team, qualitative and quantitative data were collected, by means of literature evidence, validated questionnaires and self-reported interviews, considering the dimensions resulting from the EUnetHTA Core Model.

RESULTS

From a systematic search of literature, we retrieved the following studies: 6 on hepatic, 1 on pancreatic, 4 on biliary, 2 on bariatric, 4 on endocrine, 2 on thoracic, 11 on colorectal, 7 on urology, 11 on gynecology, 2 on gastric surgery. Fluorescence guide has shown advantages on the length of hospitalization particularly in colorectal surgery, with a reduction of the rate of leakages and re-do anastomoses, in spite of a slight increase in operating time, and is confirmed to be a safe, efficacious, and sustainable vision technology. Clinical applications are still presenting a low evidence in the literature.

CONCLUSION

The present paper, under the patronage of Italian Society of Endoscopic Surgery, based on an HTA approach, sustains the use of fluorescence-guided vision in minimally invasive surgery, in the fields of general, gynecologic, urologic, and thoracic surgery, as an efficient and economically sustainable technology.

Intraoperative near-infrared autofluorescence imaging for hypocalcemia risk reduction after total thyroidectomy: Evidence from a meta-analysis

This meta-analysis evaluates whether near-infrared autofluorescence (NIRAF) imaging reduces the risk of hypocalcemia after total thyroidectomy. A systematic literature search in PubMed, EMBASE, Web of Science, and Cochrane Library for studies from June 2011 to January 2021 comparing total thyroidectomy with NIRAF and conventional surgery (naked eye). Six eligible studies involving 2180 patients were included. The prevalence of transient hypocalcemia was 8.11% (40/493) and 25.19% (425/1687) in the NIRAF and naked eye groups (p < 0.0001), respectively. The prevalence of permanent hypocalcemia was 0% (0/493) and 2.19% (37/1687) in the NIRAF and naked eye groups (p = 0.05), respectively. NIRAF reduces the risk of transient hypocalcemia and may possibly lower the rate of permanent hypocalcemia. Nonetheless, further studies are needed to verify our results and evaluate the cost-effectiveness of NIRAF in real-world clinical practice.

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.

A visual quantification of tissue distinction in robotic transabdominal lateral adrenalectomy: comparison of indocyanine green and conventional views

BACKGROUND

Recent studies have reported the feasibility of indocyanine green fluorescence imaging of adrenal tumors to guide dissection. Although the adrenal has been reported to concentrate the dye more than surrounding tissues, the amount of tissue distinction and how this compares with conventional vision has not been quantified before. The aim of this study is to quantify this distinction using color analysis.

METHODS

This was an institutional review board-approved retrospective study. By excluding adrenal cortical carcinoma, metastasis and pheochromocytoma, video recordings of 50 patients who underwent robotic transabdominal lateral adrenalectomy with indocyanine green (ICG) imaging for adrenocortical tumors between August 2015 and May 2018 were reviewed. Using a color analysis software, the pixel intensity of adrenal tumors versus adjacent retroperitoneal tissues was calculated for conventional red, green and blue, as well as indocyanine green (ICG) scales. Statistical analysis was performed using ANOVA.

RESULTS

A total of 50 patients underwent unilateral robotic transabdominal lateral adrenalectomy. All procedures were completed robotically without a conversion to laparoscopy or open. Morbidity was 4%. Measured pixel intensity of adrenal tumors was higher than adjacent retroperitoneal tissues for all conventional color and ICG modes (p < 0.0001), with the gradient being more pronounced for ICG green versus conventional red, green and blue modes.

CONCLUSIONS

To our knowledge this is the first study attempting to encode tissue planes in robotic adrenalectomy. The results show that the visual contrast distinction observed between adrenal and adjacent retroperitoneal tissues can be quantified using pixel intensity. ICG enabled the distinction of tissue planes with a wider gradient compared to conventional RGB view, quantifying its subjective benefits reported in prior studies.

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.

Intraoperative near-infrared imaging of parathyroid glands: A comparison of first- and second-generation technologies

BACKGROUND

Intraoperative near-infrared imaging (NIFI) of parathyroid glands (PG) by first-generation technology had limited image quality and depth penetration. Second-generation NIFI has recently been introduced. Our aim was to compare (1) capability to detect PG and (2) image quality between older and newer technologies.

METHODS

Accurately detecting PG, as well as, quality of autofluorescence (AF) was compared between an older charge-coupled device (CCD) camera and a newer complementary metal-oxide semiconductor (CMOS). χ² , t test, and analysis of variance were used for analysis.

RESULTS

There were 300 patients who underwent parathyroidectomy (PTX) and/or thyroidectomy (THY) with NIFI, 200 with CCD, and 100 with CMOS. Although both NIFI technologies detected >94% of PG, CMOS was superior to CCD. Comparing AF quality, mean pixel intensity of PG compared with the background was higher with CMOS compared with CCD. When comparing PG detected by NIFI before visual identification by a surgeon, both CCD and CMOS had similar results (25% vs. 22%; p = .3).

CONCLUSION

Both NIFI cameras were excellent at detecting PG. Second-generation NIFI (CMOS) displayed higher detection rates and AF intensity. Although surgeons identified majority of PG before NIFI detection, 25% of PG were identified with NIFI first, suggesting future advancements of this technology may expand its applications during parathyroid/thyroid operations.

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.

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.

Intraoperative Indocyanine Green (ICG) Angiography for the Identification of the Parathyroid Glands: Current Evidence and Future Perspectives

BACKGROUND/AIM

Recently, indocyanine green (ICG) fluorescence imaging has been used for the identification of the parathyroid glands (PG) during thyroid and parathyroid surgery. However, an overall consensus on the optimal technique, the dosage, the timing of the ICG administration and finally its interpretation and clinical usefulness is still lacking evidence. The aim of this review is to investigate the use of ICG angiography during thyroidectomy and/or parathyroidectomy for identification as well as for the perfusion integrity of the parathyroid glands.

MATERIALS AND METHODS

The PubMed database was systematically searched for publications regarding intraoperative ICG imaging in patients that undergo thyroidectomy or parathyroidectomy.

RESULTS

Eighteen publications reporting on 612 patients, namely 71 parathyroidectomy and 541 thyroidectomy patients met the inclusion criteria. Eleven publications reported the use of ICG angiography for the identification of the parathyroid glands during thyroidectomy and seven during parathyroidectomy for primary and secondary hyperparathyroidism.

CONCLUSION

ICG fluorescence imaging is a simple, fast and reproducible method capable of intraoperatively visualizing and assessing the function of parathyroid glands, and can, therefore, assist surgeons in their decision-making. Despite all this, ICG fluorescence imaging technique for PG detection still lacks standardization and further studies are needed to establish its clinical utility.

Recent Advances and the Potential for Clinical Use of Autofluorescence Detection of Extra-Ophthalmic Tissues

The autofluorescence (AF) characteristics of endogenous fluorophores allow the label-free assessment and visualization of cells and tissues of the human body. While AF imaging (AFI) is well-established in ophthalmology, its clinical applications are steadily expanding to other disciplines. This review summarizes clinical advances of AF techniques published during the past decade. A systematic search of the MEDLINE database and Cochrane Library databases was performed to identify clinical AF studies in extra-ophthalmic tissues. In total, 1097 articles were identified, of which 113 from internal medicine, surgery, oral medicine, and dermatology were reviewed. While comparable technological standards exist in diabetology and cardiology, in all other disciplines, comparability between studies is limited due to the number of differing AF techniques and non-standardized imaging and data analysis. Clear evidence was found for skin AF as a surrogate for blood glucose homeostasis or cardiovascular risk grading. In thyroid surgery, foremost, less experienced surgeons may benefit from the AF-guided intraoperative separation of parathyroid from thyroid tissue. There is a growing interest in AF techniques in clinical disciplines, and promising advances have been made during the past decade. However, further research and development are mandatory to overcome the existing limitations and to maximize the clinical benefits.

Total Versus Near-total Thyroidectomy in Graves Disease: Results of the Randomized Controlled Multicenter TONIG-trial

BACKGROUND

Previous data suggest that the incidence of hypoparathyroidism after surgery for Graves disease (GD) is lower after subtotal thyroidectomy compared to total thyroidectomy (TT). The present study evaluated the incidence of postoperative hypoparathyroidism after near-total (NTT) versus TT in GD.

METHODS/DESIGN

In a multicenter prospective randomized controlled clinical trial, patients with GD were randomized intraoperatively to NTT or TT. Primary endpoint was the incidence of transient postoperative hypoparathyroidism. Secondary endpoints were permanent hypoparathyroidism, transient recurrent laryngeal nerve palsy (RLNP), reoperations for bleeding, inadvertently removed parathyroid glands, and recurrent hyperthyroidism after 12 months.

RESULTS

Eighteen centers randomized 205 patients to either TT (n = 102) or NTT (n = 103) within 16 months. According to intention-to-treat postoperative transient hypoparathyroidism occurred in 19% (20/103) patients after NTT and in 21% (21 of 102) patients after TT (P = 0.84), which persisted >6 months in 2% and 5% of the NTT and TT groups (P = 0.34). The rates of parathyroid autotransplantation (NTT 24% vs TT 28%, P = 0.50) and transient RLNP (NTT 3% vs TT 4%, P = 0.35) was similar in both groups. The rate of reoperations for bleeding tended to be higher in the NTT group (3% vs 0%, P = 0.07) and the rate of inadvertently removed parathyroid glands was significantly higher after NTT (13% vs 3%, P = 0.01). An existing endocrine orbitopathy improved in 35% and 24% after NTT and TT (P = 0.61). Recurrent disease occurred in only 1 patient after TT (P = 0.34).

CONCLUSION

NTT for GD is not superior to TT regarding transient postoperative hypoparathyroidism.

Near-infrared autofluorescence in thyroid and parathyroid surgery

Contrast-free autofluorescence (AF) of the parathyroid glands (PTGs) and thyroid tissue occurs in the near-infrared (NIR) spectrum on excitation by light in the upper range of the visible spectrum or lower NIR spectrum. In vivo, PTGs autofluoresce more brightly than thyroid (by a factor of 2-20 times) and appear as a bright spot against surrounding thyroid, muscle or fat on a processed image which is generated in real-time. NIR-AF of PTGs was first described in 2009 although NIR-AF had previously been used in several other clinical applications. Since then there has been a great amount of interest in the use of NIR-AF in thyroid and parathyroid surgery with over 25 published reports of the utilisation of both self-built and proprietary NIR-AF devices in neck endocrine surgery. All of these reports have confirmed the feasibility of NIR-AF intraoperatively and its ability to detect PTGs, although the reported accuracy varies from 90-100%. Reports of the effect of NIR-AF on relevant clinical endpoints i.e., post-operative hypoparathyroidism in thyroidectomy and persistent disease in parathyroidectomy are however scant. There has been one multicentre clinical trial of NIR-AF in thyroidectomy but this did not report clinical outcomes and two single-centre, non-randomised studies which did report post-operative hypoparathyroidism but with differing results: one showing no benefit in 106 NIR-AF vs. 163 controls and one, a reduction of early hypocalcaemia from 20% to 5% in 93 NIR-AF patients vs. 420 controls. There were only 2 cases of permanent hypoparathyroidism across both studies and therefore no significant observable difference in this key outcome variable. In parathyroidectomy, possible variability of the AF signal due to composition of a PTG adenoma, secondary/tertiary disease and MEN1 as well as depth-penetration preventing detection of sub-surface PTGs would imply that NIR-AF in its current form is not well-placed to improve cure-rates in hyperparathyroidism, which may already be as high as 98%. Thus far, no study has addressed this. Despite the promising results of NIR-AF, the absence of data demonstrating an improvement in outcomes and the cost of its use currently limit its use in routine clinical practice, especially in a publicly funded healthcare system with budgetary constraints. However, it can be utilised in research settings and this should be undertaken within the context of well-designed and conducted randomised, multi-centre, appropriately powered studies, which will assist in establishing its role in neck endocrine surgery.

Phase-sensitive fluorescence detector for parathyroid glands during thyroidectomy: A preliminary report

Despite advances in medical technology, the parathyroid glands are still damaged during thyroid surgery. Our previous studies exploring methods for locating the parathyroid glands using autofluorescence have limitations, such as turning off the surgical light or requiring additional matching between the autofluorescence image and real-surgical field-of-view. We developed a probe-type parathyroid autofluorescence detector using a phase-sensitive process and optical filtering to overcome these limitations. A preliminary clinical trial was performed on eight parathyroid glands in four patients. The normalized mean signal of the normal parathyroid glands was 332% stronger than that of the thyroid, and 384%, 459% and 286% stronger than the signal of the muscle, trachea and fat, respectively. Additionally, the device also detected fluorescence from indocyanine green.

Multi-Wavelength Fluorescence in Image-Guided Surgery, Clinical Feasibility and Future Perspectives

With the rise of fluorescence-guided surgery, it has become evident that different types of fluorescence signals can provide value in the surgical setting. Hereby a different range of targets have been pursued in a great variety of surgical indications. One of the future challenges lies in combining complementary fluorescent readouts during one and the same surgical procedure, so-called multi-wavelength fluorescence guidance. In this review we summarize the current clinical state-of-the-art in multi-wavelength fluorescence guidance, basic technical concepts, possible future extensions of existing clinical indications and impact that the technology can bring to clinical care.

New Advances of ICG Angiography in Parathyroid Identification

Objective:

For surgeons, locating parathyroid in thyroidectomy and parathyroidectomy is critical since parathyroid plays an important role in calcium balance. The fluorescence of parathyroid has already been found by researchers and the angiography equipment detecting the fluorescence of parathyroid with indocyanine green has been widely applied. Using the indocyanine green angiography and looking at the actual fluorescence of in vivo and in vitro tissues, it was possible to identify thyroid, parathyroid, lymph nodes and fat tissues during the surgical procedure. This mini-review aims to present the application of indocyanine green angiography in parathyroid detection and discusses the safety of this method.

Methods:

The relevant data were searched by using the keywords “Indocyanine green,” “Parathyroid,” and “Identification” and “Protection” in “Pubmed,” “Web of Science” and “China Knowledge Resource Integrated databases”, and a manual search was done to acquire peer-reviewed articles and reports about indocyanine green.

Results:

Indocyanine green dye along with the intraoperative fluorescence imaging system is safe in detecting parathyroid and predicting postoperative hypoparathyroidism.

Conclusion:

The conclusion suggests that indocyanine green angiography is a safe, effective and easy way to detect parathyroid glands. The conclusion will be of interest to surgeons regarding thyroidectomy and parathyroidectomy.

Does fluoroscopy prevent inadvertent parathyroidectomy in thyroid surgery?

INTRODUCTION

Near-infrared imaging may facilitate intraoperative identification of parathyroid glands by causing autofluorescence but its clinical value has not been established. Inadvertent parathyroidectomy occurs in 5-22% of thyroidectomies and is associated with temporary and permanent hypoparathyroidism. The aim of this study was to determine whether near-infrared imaging prevents inadvertent parathyroidectomy and early hypocalcaemia as a surrogate for permanent hypoparathyroidism.

MATERIALS AND METHODS

Near-infrared imaging was used in a prospective cohort of consecutive thyroidectomies. Thyroidectomies performed prior to the introduction of near-infrared imaging formed a control group. The thyroid bed and specimen were scanned with near-infrared imaging. Areas of autofluorescence on the specimen were examined and any parathyroid tissue found was autotransplanted. Inadvertent parathyroidectomy was therefore recorded as established intraoperatively by near-infrared imaging (allowing autotransplantation) or on subsequent histology (missed). Serum calcium and parathyroid hormone were measured on day one and at two weeks and six months postoperatively.

RESULTS

A total of 269 patients were included: 106 near-infrared imaging and 163 controls. Inadvertent parathyroidectomy was detected by near-infrared imaging in two (and autotransplantation performed) and histologically (i.e. missed by near-infrared imaging in 13, 12.3% vs 17, 10.4% controls). Neither result was statistically significant (P = 0.08, 0.89). There was no significant difference in serum calcium or parathyroid hormone between near-infrared imaging and control groups at one day, two weeks or thereafter.

DISCUSSION

Near-infrared imaging may detect inadvertent parathyroidectomy and may allow autotransplantation. It did not, however, reduce the incidence of missed inadvertent parathyroidectomy and no difference was seen in early hypocalcaemia or late hypoparathyroidism. Current near-infrared imaging technology does not appear to confer a clinical benefit sufficient to justify its use.

Indocyanine green fluorescence imaging during partial adrenalectomy

BACKGROUND

Indocyanine green (ICG) fluorescence imaging represents an emerging technology that facilitates the assessment of tissue vascularity, tissue distinction, and tumor localization during surgery. The aim of this study was to investigate the potential role of ICG imaging during laparoscopic partial adrenalectomy.

METHODS

Indocyanine fluorescence imaging was carried out during laparoscopic partial adrenalectomy for bilateral pheochromocytoma and bilateral Cushing's syndrome. A first bolus of 5 mg ICG was applied intravenously upon exposure of the retroperitoneal plane to identify the adrenal borders. The fluorescence was visualized using a Storz^® NIR/ICG endoscopic system. As the camera of this system detects NIR light as a blue signal, the well-vascularized adrenal tissue was expected to show a strong fluorescence in the blue color channel in contrast to the surrounding adipose tissue. Following partial adrenalectomy, a second bolus of 5 mg ICG was applied intravenously to evaluate the vascularity of the remaining adrenal tissue.

RESULTS

We investigated six adrenal glands from three patients undergoing bilateral partial adrenalectomy. The indication for surgery was pheochromocytoma in two patients and Cushing's syndrome with bilateral adenomas in one patient. Regarding left adrenalectomies, ICG imaging was helpful in visualizing the adrenal borders and the adrenal vein. Further, it facilitated the identification of the hypofluorescent pheochromocytoma and to resect the entire tumor. On the right side, due to the more apparent anatomy, ICG imaging did not contribute to the conduct of the operation. Four adrenal remnants showed a strong vascularization and two remnants were only reasonably vascularized.

CONCLUSION

ICG fluorescence may be helpful in guiding partial adrenalectomy and assessing the vascularity of remaining adrenal tissue.

The use of Indocyanine green in endocrine surgery of the neck: A systematic review

BACKGROUND

The insufficient reliability of preoperative imaging technology and limited convenience of intraoperative visualizing techniques have been associated with difficulty in surgical navigation in neck endocrine surgery. Indocyanine green (ICG) fluorescence imaging has stood out as the real-time intraoperative guide amidst research for novel modalities, with an emerging use in endocrine surgery.

METHODS

We performed a systematic review of the PubMed, Scopus and Embase databases, to identify published studies on parathyroid and thyroid operations employing ICG. Well-described articles were selected according to 7 criteria and analyzed per operation type and organ structure.

RESULTS

Twenty-one articles matched our selection criteria. Dosage, equipment, and techniques are well-described in literature. ICG was found to significantly enhance the surgical experience and outcomes. Occasional discrepancy among studies was attributed to the lack of standard quantification of values and divergence of study designs.

CONCLUSION

The most successful applications of ICG are:Future research is needed for standard quantification of fluorescence intensity and objective comparisons.

Intraoperative Near-Infrared Autofluorescence and Indocyanine Green Imaging to Identify Parathyroid Glands: A Comparison

OBJECTIVE

To investigate the feasibility of near-infrared autofluorescence (AF) and indocyanine green (ICG) fluorescence to identify parathyroid glands intraoperatively.

METHODS

Fluorescence imaging was carried out during open parathyroid and thyroid surgery. After visual identification, parathyroid glands were exposed to near-infrared (NIR) light with a wavelength between 690 and 770 nm. The camera of the Storz® NIR/ICG endoscopic system used detects NIR light as a blue signal. Therefore, parathyroid AF was expected to be displayed in the blue color channel in contrast to the surrounding tissue. Following AF imaging, a bolus of 5 mg ICG was applied intravenously. ICG fluorescence was detected using the same NIR/ICG imaging system. Well-vascularized parathyroid glands were expected to show a strong fluorescence in contrast to surrounding lymphatic and adipose tissue.

RESULTS

We investigated 78 parathyroid glands from 50 patients. 64 parathyroid glands (82%) displayed AF showing the typical bluish violet color. 63 parathyroid glands (81%) showed a strong and persistent fluorescence after application of ICG. The sensitivity of identifying a parathyroid gland by AF was 82% (64 true positive and 14 false negative results), while ICG imaging showed a sensitivity of 81% (63 true positive and 15 false negative results). The Fisher exact test revealed no significant difference between both groups at p < 0.05. Neither lymph nodes nor adipose tissue revealed substantial AF or ICG fluorescence.

CONCLUSION

AF and ICG fluorescence reveal a high degree of sensitivity in identifying parathyroid glands. Further, ICG imaging facilitates the assessment of parathyroid perfusion. However, in the current setting both techniques are not suitable as screening tools to identify parathyroid glands at an early stage of the operation.

Parathyroid gland management using optical technologies during thyroidectomy or parathyroidectomy: A systematic review

New optical technologies enhancing localization or assessing viability of parathyroid glands (PG) during endocrine surgery have been reported in clinical studies. These technologies could become complementary to the surgeon's eyes and may improve surgical outcomes in thyroidectomy and parathyroidectomy. Here, we conducted a systematic review focusing on PG identification and functional assessment using optical methods to enhance surgery. A systematic literature review was performed using MEDLINE and Embase database. Two authors selected studies and extracted data; qualitative analysis was performed to summarize the characteristics of reported optical tools for thyroidectomy or parathyroidectomy. Identification and vascularisation of PG during surgery were evaluated. Clinical and biochemical outcomes were appraised when reported. Studies relating to parathyroidectomy or thyroidectomy combined with autofluorescence, fluorescent methylene blue, 5-aminolevulinic acid, indocyanine green (ICG), optical coherence tomography, laser speckle contrast imaging, dynamic optical contrast imaging and Raman spectroscopy were identified with MEDLINE and Embase. We included a total of 47 relevant articles with a total of 1615 patients enrolled. Each optical technique is described and appreciated related to its surgical purpose. Autofluorescence and ICG imaging of PG are the most widely reported optical technologies for identification and assessment of vascularisation of PG. Results are mainly based on observational studies and argue for the feasibility of both techniques in endocrine surgery but prospective randomized studies have not been performed. In vivo applications are still limited for the other methods and further investigations correlating these techniques with post-operative parathormone measurements are still needed before considering these technologies in clinical practice.