Intra-Operative Indocyanine Green Angiography of the Parathyroid Gland

Advances in the application of auxiliary imaging techniques in parathyroid diseases

Hypoparathyroidism is one of the main complications after total thyroidectomy, severely affecting patients' quality of life. How to effectively protect parathyroid function after surgery and reduce the incidence of hypoparathyroidism has always been a key research area in thyroid surgery. Therefore, precise localization of parathyroid glands during surgery, effective imaging, and accurate surgical resection have become hot topics of concern for thyroid surgeons. In response to this clinical phenomenon, this study compared several different imaging methods for parathyroid surgery, including nanocarbon, indocyanine green, near-infrared imaging techniques, and technetium-99m methoxyisobutylisonitrile combined with gamma probe imaging technology. The advantages and disadvantages of each method were analyzed, providing scientific recommendations for future parathyroid imaging. In recent years, some related basic and clinical research has also been conducted in thyroid surgery. This article reviewed relevant literature and provided an overview of the practical application progress of various imaging techniques in parathyroid surgery.

Comparison of indocyanine green angiography vs intraoperative parathyroid hormone in early prediction of risk of post-thyroidectomy hypocalcemia: a prospective cohort study

Introduction

Indocyanine green (ICG) angiography is the 'real-time intraoperative imaging' technique used to reduce the chances of hypoparathyroidism in post-thyroidectomy patients. In our study, the authors predicted the risk of early post-thyroidectomy hypocalcemia by intraoperative evaluation of parathyroid gland perfusion by ICG angiography.

Materials and methods

In patients who underwent total thyroidectomy, ICG angiography was done using the SPY PHI imaging system (Stryker). Post-thyroid specimen removal, scoring of parathyroids was done in spy contrast mode. All 4 or <4 visualized parathyroids were scored for vascularity with the highest score of 8. Serum ionized calcium was done 6 h postsurgery and on the morning and evening of postoperative days 1 and 2. Calcium supplements were given to only those who developed clinical or severe biochemical hypocalcemia.

Results

Out of 60, postoperative hypocalcemia was noted in 41 patients. Total ICG score ≤5 was seen in 34 patients, out of which 28 developed postoperative hypocalcemia showing PPV 82.3% and diagnostic accuracy of 68.3% while iPTH (4.28 pmol/l) showed PPV 76.7 and diagnostic accuracy 70 %. In eight patients, none of the glands was scored as 2 (White) and all these patients developed hypocalcemia requiring calcium infusion.

Conclusion

The absence of visualization of at least 1 well-perfused (score 2) gland on ICG angiography is highly predictive of hypocalcemia and the majority of patients with total ICG score ≤5 developed hypocalcemia in the immediate postoperative period. ICG is a good predictor of the absence of hypoparathyroidism after thyroidectomy and is comparable to iPTH in the prediction of post-thyroidectomy hypocalcemia.

[Indocyanine green angiography in assessment of parathyroid remnant perfusion after subtotal parathyroidectomy: a case report]

A 72-year-old female patient with chronic kidney disease stage presented with multiple parathyroid adenomas and tertiary hyperparathyroidism. SPECT/CT with 99mTc-MIBI revealed accumulation of radiopharmaceuticals in 2 out of 4 parathyroid glands. Ultrasound established localization of all parathyroid glands. Subtotal parathyroidectomy with excision of 3 glands and resection of half of the fourth gland was performed. Intraoperative indocyanine green angiography was performed to identify all parathyroid glands and remnant perfusion. There was normal parathyroid function after 6 months.

Assessing Parathyroid Gland Viability and Predicting Postoperative Hypoparathyroidism in Thyroid Surgery: The Utility of Indocyanine Green Angiography

Objectives

Postoperative hypoparathyroidism is a common complication following thyroidectomy, with the potential for significant morbidity and cost. While various techniques have been proposed for intraoperative parathyroid gland (PG) identification and preservation, indocyanine green (ICG) angiography has emerged as a promising method. In this retrospective study, patients who underwent total thyroidectomy with or without central neck dissection were evaluated for the utility of ICG angiography in identifying PGs and the correlation of ICG scores with postoperative parathyroid function.

Methods

ICG angiography was performed using a standardized protocol, and the degree of PG vascularization was assessed visually. A scoring system was employed based on ICG uptake intensity in PGs, as described in the literature. Pearson's correlation test examined the relationship between the total ICG score and percentage parathyroid hormone (PTH) gradient, postoperative calcium, and PTH levels. In addition, patients with at least one well-vascularized PG were also evaluated.

Results

Twenty-two patients were included in the study. Significant positive correlations were found between the total ICG score and postoperative PTH levels (r=0.549, p=0.008), and a negative correlation with the percentage of PTH gradient (r=-0.504, p=0.01). However, six patients with well-vascularized PGs on ICG angiography still developed postoperative hypoparathyroidism.

Conclusion

ICG angiography offers a potential tool for evaluating PG vascularization during thyroidectomy and predicting the risk of postoperative hypoparathyroidism. However, its application should be used judiciously, and the technique should be improved for PG preservation. Further studies are warranted to better understand its benefits and limitations in thyroid surgery.

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

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

Correlation between visual scores and parathyroid function

This mini review summarizes the controversies regarding routine parathyroid identification reviews publications that assess visual scores to predict parathyroid function after thyroidectomy during the pre-ICG era.

Incremental value of magnification and indocyanine green for parathyroid preservation in thyroid surgery

BACKGROUND

To assess the promise of surgical magnification and of intraoperative indocyanine green (ICG) assisted near-infrared fluorescence (NIRF) in improving parathyroid identification and viability assessment during thyroidectomy.

METHODS

Prospective comparative study. Parathyroid gland identification sequentially assessed by naked eye, surgical microscopy, and by NIRF imaging following ICG administration (5 mgIV). Parathyroid perfusion/vitality reassessed end-surgery by ICG-NIRF.

RESULTS

An expected total of 104 parathyroid glands were assessed in 35 patients (17 total-thyroidectomy, 18 hemi-thyroidectomy). 54/104 (51.9%) were identified by naked eye, and sequentially greater numbers identified by microscope magnification (n = 61; 58.7%; p = 0.33), and by ICG-NIRF (n = 72; 69.2%; p = 0.01). ICG-NIRF detected additional parathyroid glands in 16/35 patients (45.7%). Confident identification of at least one parathyroid remained unachieved in 5/35 by naked eye, in 4/35 by microscopic magnification, and in no patient by ICG-NIRF. ICG-NIRF indicated end-of-surgery devascularization in 12/72 glands and informed decisions regarding gland implantation.

CONCLUSION

Significantly greater parathyroid glands are identified and preserved with surgical magnification and with ICG-NIRF. Both techniques merit routine adoption for thyroidectomy.

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.

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.

Incidental Parathyroidectomy Among Pediatric Patients Undergoing Thyroid Surgery

OBJECTIVE

To evaluate rates of incidental parathyroidectomy(IP) and to determine risk factors among children undergoing thyroid surgery.

STUDY DESIGN

Retrospective case-control study.

METHODS

Pediatric patients undergoing thyroidectomy with or without neck dissection were included in this retrospective cohort study over a 20 year period. Demographics, clinical features, and surgical outcomes were evaluated. The primary outcome was the presence of parathyroid tissue in the surgical specimen.

RESULTS

Two hundred and eighty-six patients were included (100 cases with ≥1 parathyroid gland found in the pathology specimen and 186 controls). The most common surgical indication was cancer (49%), followed by benign nodule (25%). Hemithyroidectomy was performed in 119 (42%) patients, total thyroidectomy in 138 (48%), and completion in 29 (10%). Central neck dissection (CND) and lateral neck dissection were performed in 41% and 13%, respectively. 27 (9%) patients had parathyroid reimplantation. On univariable analysis, diagnosis, adenopathy on preoperative ultrasound, extent of thyroidectomy, neck dissection, and parathyroid reimplantation were significant predictors of IP. On multivariate analysis, CND > 5 nodes were the sole predictor of IP. Patients with IP were more likely to require postoperative calcium/vitamin D supplementation compared to those without (44% vs. 16%; P < .001).

CONCLUSIONS

Incidental parathyroidectomy during pediatric thyroidectomy is relatively common. CND was independently predictive of IP. There were increased rates of postoperative hypocalcemia when 1 or more parathyroid gland was identified in the specimen. Reimplantation of 1 parathyroid gland was predictive of another gland in the specimen. Anticipating outcomes may help optimize patient care by allowing for early supplementation, frequent monitoring, and consideration of ancillary monitoring modalities in high-risk procedures.

LEVEL OF EVIDENCE

Level 4 Laryngoscope, 132:2262-2269, 2022.

Near-infrared autofluorescence of the parathyroid glands during thyroidectomy for the prevention of hypoparathyroidism: a prospective randomized clinical trial

Purpose

Postoperative hypoparathyroidism remains the most often complication in thyroid surgery. Near-infrared autofluorescence (NIR-AF) is a modality to identify parathyroid glands (PG) in vivo with high accuracy, but its use in daily routine surgery is unclear so far. In this randomized controlled trial, we evaluate the ability of NIR-AF to prevent postoperative hypoparathyroidism following total thyroidectomy.

Methods

Patients undergoing total thyroidectomy were allocated in two groups with the use of NIR-AF in the intervention group or according to standard practice in the control group. The aim was to identify the PGs in an early most stage of the operation to prevent their devascularization or removal. Parathyroid hormone was measured pre- and postoperatively and on postoperative day (POD) 1. Serum calcium was measured on POD 1 and 2. Possible symptoms and calcium/calcitriol supplement were recorded.

Results

A total of 60 patients were randomized, of whom 30 underwent NIR-AF-based PG identification. Hypoparathyroidism at skin closure occurred in 7 out of 30 patients using NIR-AF, respectively, in 14 out of 30 patients in the control group (p=0.058). There was no significant difference in serum calcium and parathyroid hormone levels between both groups. Likewise, NIR-AF could not detect PGs at a higher rate.

Conclusion

The use of NIR-AF may help surgeons identify and preserve PGs but did not significantly reduce the incidence of postoperative hypoparathyroidism in this trial. Larger case series have to clarify whether there is a benefit in routine thyroidectomy.

Trial registration number

DRKS00009242 (German Clinical Trial Register). Registration date: 03.09.2015

The Effectiveness and Quality of Life Outcomes by Transoral Endoscopic Vestibular Thyroidectomy Using Intraoperative Indocyanin Green Fluorescence Imaging and Neuromonitoring—A Cohort Study

Background: Transoral endoscopic vestibular thyroidectomy (TOEVT), a variant of natural orifice transluminal endoscopic surgery, offers a scar-less thyroid to young females. However, few studies have compared the effectiveness and quality of life (QoL) outcomes of the TOEVT with open thyroidectomy (OT). This is the first study in the Middle East and North Africa region that compares the effectiveness, safety profile and QoL outcomes between TOEVT with OT. Methods: We reviewed the medical records of consecutive patients with TOETV and OT at Zulekha Hospital Sharjah and Dubai United Arab Emirates, between 1 January 2019 and 1 April 2021. The data for demographics, type of surgery, operative time, blood loss, post-operative nodule size, hospital stay and post-operative complications were analyzed. We used an SF-36 questionnaire pre- and postoperatively for the assessment of QoL in both groups. Findings: Out of a total of 41 OT and 32 TOEVT procedures, 59 patients (31 TOEVT and 28 OT) fulfilled the inclusion criteria. There were 45 women and 14 men with an average age of 41 years. The mean operating time was 126 min in TOEVT and 96 min in OT (p = 0.000). The mean thyroid size was 5.55 cm in TOEVT and 8.76 cm in OT (p = 0.000). Lastly, the mean intraoperative blood loss was 39 cc and 95.7 cc in TOEVT and OT, respectively (p = 0.001). There was one temporary hypocalcemia and seroma in TOEVT, four cases of temporary hypocalcemia and one with minor bleeding in OT. The post-operative QoL significantly improved in all patients. However, the QoL improved more significantly in the TOEVT group for bodily pain, vitality, role emotions and cosmetic concerns (p = 0.000). Conclusion: The safety profile and effectiveness of the TOEVT is comparable to the OT procedure. However, TOEVT has an additional advantage of being scarless and offers a better QoL.

The utility of indocyanine green (ICG) for the identification and assessment of viability of the parathyroid glands during thyroidectomy

We conducted this study to evaluate the ability of indocyanine green (ICG) and near infra-red fluorescence (NIRF) camera to aid in the identification and assessment of viability of parathyroid glands during thyroid surgery. A prospective observational study was conducted between May and October 2020 among 50 consecutive patients who underwent total thyroidectomy at a single institution. Parathyroid glands were identified under white light during thyroidectomy following which reconstituted ICG was injected through a peripheral vein and the location of parathyroid glands was confirmed. The perfusion to the parathyroid gland was assessed by documenting the fluorescence intensity score (FIS) and the parathyroid angiogram score (PAS). There was no difference in the number of parathyroid glands seen on visual inspection 147 (73.5%) when compared to under NIRF camera, 146 (73%). Though the rate of postoperative hypoparathyroidism was lower in the cohort with FIS 3 (14.2%) compared to score 2 and 1 (28.5% and 100%, respectively), this was not significant (p = 0.35). A significant correlation was noted between a delayed flow on PAS and the development of post-thyroidectomy hypoparathyroidism (p = 0.01). PAS had a sensitivity of 100%, specificity of 88.6%, NPV of 100% and PPV of 55.6% to predict the development of post-thyroidectomy hypoparathyroidism. In this study, there was no additional benefit of ICG and NIRF camera in the identification of parathyroid glands. However, ICG angiogram seems to be a good adjunct for the intraoperative assessment of the viability of the parathyroid glands and accurately predicts the development of postoperative hypoparathyroidism.

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

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

Diagnostic Performance of Indocyanine Green Plus Methylene Blue Versus Radioisotope Plus Methylene Blue Dye Method for Sentinel Lymph Node Biopsy in Node-Negative Early Breast Cancer

PURPOSE

Sentinel lymph node biopsy (SLNB) by dual-dye method (radioisotope plus blue) is the gold standard for axillary staging in patients with breast cancer, but in developing countries, logistic issues and financial constraint play a vital role. Recently, indocyanine green (ICG) has emerged as an alternative to radioisotope (technetium-99 [Tc-99]) for SLNB in breast cancer. This study compared the diagnostic performance of Tc-99 plus methylene blue (MB) dye versus ICG + MB dye SLNB.

METHODS

Two hundred seven patients with early breast cancer (T1-3N0) were included in the study from 2017 to 2019. SLNB was done either with Tc-99 + MB or with ICG + MB as per availability of radioisotope. SLN identification rate (IR), SLN positivity rate, and metastatic SLN counts were compared between the 2 groups.

RESULTS

IR was 199 (96%) of 207. IR was 95% in Tc-99 + MB compared with 97% with ICG + MB. The mean number of SLNs identified were 3.17 (standard deviation [SD], 1.84), with > 1 SLN identified in 87% patients by Tc-99 + MB. SLN was positive in 31.3% of patients with a metastatic SLN count of 0.37 (SD, 0.76). With ICG + MB, the number of SLNs was 2.73 (SD, 1.55), with > 1 SLN identified in 79% of patients. Twenty-eight percent of patients had positive SLNs, with a metastatic SLN count of 0.41 (SD, 0.77). A sharp decline in the availability of Tc-99 was observed, with 58% of patients in 2014 and only 12% of patients in 2018.

CONCLUSION

ICG is equivalent to Tc-99 for SLNB in early breast cancer and has a good potential to be adopted by surgeons in resource-constrained setups.

Rapid intraoperative perfusion assessment of parathyroid adenomas with ICG using a wide-field portable hand-held fluorescence imaging system

BACKGROUND

Fluorescence angiography (FA) using indocyanine green dye (ICG) has recently been introduced for real-time identification of parathyroid adenomas. However, time to peak fluorescence has not yet been critically evaluated.

METHODS

This was a retrospective review of parathyroidectomies with ICG FA over a one-year period.

RESULTS

There were 66 patients with average age of 64 years. The average time to initial fluorescence was 26.7 s and to peak fluorescence was 38.0 s. The time to saline flush administration significantly correlated with times to initial and peak fluorescence (p < .0001). The rate of in-situ fluorescence was 97%. The rates of suspected adenoma detection were 69% for sestamibi scan, 71% for ultrasound, and 96% for CT scan. Imaging was discordant in 13 cases (20%), with the adenoma located on the opposite side of the neck in 4 cases.

CONCLUSIONS

ICG FA is a rapid and effective adjunct for the intraoperative identification of parathyroid adenomas.

Intraoperative Nerve Monitoring in Thyroidectomies for Malignancy: Does it Matter?

BACKGROUND

Recurrent laryngeal nerve (RLN) injury and postoperative hypocalcemia are potential complications of thyroidectomy, particularly in malignancy. Intraoperative nerve monitoring (IONM) remains controversial. We sought to evaluate the impact of IONM on these complications using a national data set.

METHODS

The American College of Surgeons National Surgical Quality Improvement Program thyroidectomy-targeted data set was queried for patients who underwent thyroidectomies from 2016 to 2017. Patients were grouped according to IONM use. Logistic regression models were constructed to evaluate associations of variables with 30-day hypocalcemic events (HCEs) and RLN injury. Associations were expressed as odds ratios (ORs) with 95% confidence intervals (95% CIs). A subgroup analysis was performed of patients with malignancy.

RESULTS

A total of 9527 patients were identified; 5969 (62.7%) underwent thyroidectomy with IONM and 3558 (37.3%) without. By multivariable analysis, IONM had protective associations with HCE (OR = .81, 95% CI = .68-.96; P = .013) and RLN injury (OR = .83, 95% CI = .69-.98; P = .033). Malignancy increased risk of HCE (OR = 1.21, 95% CI=1.01-1.45; P = .038) and RLN injury (OR = 1.22, 95% CI = 1.02-1.46; P = .034). A large proportion (5943/9527, 62.4%) of patients had malignancy; 3646 (61.3%) underwent thyroidectomy with IONM and 2297 (38.7%) without. In the subgroup analysis, IONM had stronger protective associations with HCE (OR = .73, 95% CI = .60-.90; P = .003) and RLN injury (OR = .76, 95% CI = .62-.94; P = .012).

DISCUSSION

Malignancy was associated with increased risk of HCE and RLN injury. Intraoperative nerve monitoring had a protective association with HCE and RLN injury, both overall, and in the malignant subgroup. Intraoperative nerve monitoring was correlated with improved thyroidectomy outcomes, especially if the indication was malignancy. This warrants further study to clarify cause and effect.

Feasibility of Autofluorescence for Parathyroid Glands During Thyroid Surgery and the Risk of Hypocalcemia: First Results in Belgium and Review of the Literature

Background. Post-operative hypocalcemia remains the most frequent complication after total thyroidectomy. Recently, autofluorescence imaging was introduced to detect parathyroid glands early during dissection. Aim. We aimed to check the feasibility of autofluorescence regarding the number of parathyroid glands visualised and the risk of post-operative hypocalcemia. Methods. In a prospectively gathered cohort of patients undergoing thyroid surgery, we describe the risk of hypocalcemia in relation to the number of parathyroid glands visualised during surgery (and the risk reported in the scientific literature) and the feasibility to obtain an autofluorescence of the parathyroid glands. Results. From 2010 to 2019, 1083 patients were referred for total thyroidectomy in our tertiary referral centre for endocrine surgery, of which, 40 consecutive cases were operated using autofluorescence. Among the autofluorescence group, 14 (35.0%) had all 4 parathyroid glands visualised, compared to 147 (14.1%) in the other patients, without differences in the number of parathyroid glands reimplanted. No permanent hypocalcemia occurred in the autofluorescence group and 17.5% temporary hypoparathyroidism, compared to 3.1% and 31.9% among the other patients, and 4% (95% confidence interval [CI] 3-5%) and 19% (95% CI 15-24%) in the literature. Conclusion. Autofluorescence imaging provides reliable real-time visualisation at any point during thyroid surgery and helps to identify the parathyroid glands before detection with the naked eye. To date, it cannot be used as a standard technique and does not replace meticulous dissection. To become a useful adjunct in peroperative parathyroid management, large multicentre studies need to establish a potential clinical benefit of this novel technique.

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.

Efficacy of Fluorescein Green Dye in Assessing Intra-Operative Parathyroid Gland Vascularity and Predicting Post-Thyroidectomy Hypocalcaemia- A Novel Prospective Cohort Study

BACKGROUND

Postoperative hypocalcaemia (POH) after total thyroidectomy (TT) is a common complication. Parathyroid hormone (PTH), an accurate predictor of POH cannot assess intra-operative viability of parathyroid glands (PGs). Different dyes including indocyanine green or carbon nanoparticles have been used, but they are expensive and not widely available. Fluorescein green dye (FD) has been used as a low-cost alternative to study viability of various organs, but seldom tried in visualizing PGs. This novel study aims to assess utility of FD in determining parathyroid viability and predicting POH.

MATERIAL AND METHOD

Total 72 out of 88 patients undergoing TT between January and December 2019 were included. Two ml of 25% FD was given intravenously before wound closure and attempts were made to visualize PGs under blue light. A numerical score was given according to the number of PGs visualized. Intact-PTH and corrected calcium were measured on postoperative day 1 and patients observed for POH.

RESULTS

No PGs were visualized in 6 patients, 1 in 13, 2 in 30, 3 in 16 & 4 in 7 patients. Mean PTH was 6, 16.9, 31.6, 33.2 and 48.5 respectively. Corrected-calcium was 7.08, 7.7, 7.9, 8.5 and 8.5 respectively. All patients with score 0 received supplementary IV calcium, while 53.8% (score-1), 30% (score-2), 0% (scores-3, 4) received the same. Sensitivity, specificity and ROC of PG score of ≥2 on FD in predicting POH were 100%, 44% and 0.83 respectively.

CONCLUSION

FD visualization of parathyroids post TT is feasible and can be used as low cost efficacious method to predict POH.

Benefits of 11C-methionine PET/MRI and intraoperative fluorescence in treating hyperparathyroidism

Multiple endocrine neoplasia 1 (MEN1) is a rare genetic syndrome characterized by the manifestation of tumors in endocrine glands most often in the parathyroid gland (PG). Treatment may involve several parathyroidectomies (PTX), especially in young patients, which increases the risk of postoperative complications. We present a 16-year-old patient with a family history of MEN1 syndrome. The patient started to show biochemical signs of hyperparathyroidism (HPT) and hypercalcemia at the age of 10. One and a half years later a PTX was successfully performed with removal of the two left PGs. However, a rise in plasma parathyroid hormone and ionized calcium was observed 4 years later. Preoperative noninvasive imaging with ^99mTc-sestamibi scintigraphy showed no definitive parathyroid adenoma. A ¹¹C-methionine position emission tomography combined with MRI (MET-PET/MRI) was then performed and detected a focus posterior to the lower part of the right thyroid lobe. Intraoperative angiography with fluorescence and indocyanine green dye was used to assess the vascularization of the remaining PGs. The lower right PG was removed. The patient was discharged with normalized biochemical values and without postoperative complications. Recurrence of primary HPT is frequent in MEN1 patients which often necessitates repeated operations. Our case report showed that the use of advanced noninvasive preoperative imaging techniques and intraoperative fluorescent imaging are valuable tools and should be taken into consideration in selected cases to avoid postoperative complications. To our knowledge, this is the first case where MET-PET/MRI has been used to detect parathyroid pathology.

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.

Intraoperative Adjunct Methods for Localization in Primary Hyperparathyroidism

Primary hyperparathyroidism (pHPT) is a frequently seen endocrine disease, and its main treatment is surgery. In the majority of pHPT, the disease involves only a single gland, and the majority of the pathological glands can be determined by preoperative localization methods.In addition to preoperative localization studies in parathyroidectomy, the use of adjunct methods to improve intraoperative localization in order to increase success of surgery is becoming widespread. These methods include different approaches, mainly intraoperative parathyroid hormone (PTH) measurement, followed by intraoperative gamma probe application, intraoperative ultrasonography, parathyroid imaging with methylene blue, and frozen section examination. Recently, especially promising new imaging methods have been described in the literature with various optical technologies to increase the localization of the parathyroid glands and to evaluate their viability. These methods include parathyroid imaging with autofluorescence, indocyanine green imaging with autofluorescence, autofluorescence imaging with methylene blue, autofluorescence imaging with 5-aminolevulinic acid, optical coherence tomography, laser speckle contrast imaging, dynamic optical contrast imaging, and Raman spectroscopy. Currently, minimally invasive parathyroidectomy has become the standard treatment for selected pHPT patients with the aid of preoperative imaging and intraoperative auxiliary methods . The aim of the present study was to evaluate the routinely used new promising intraoperative adjunct methods in pHPT.

Preoperative and Intraoperative Methods of Parathyroid Gland Localization and the Diagnosis of Parathyroid Adenomas

Accurate pre-operative determination of parathyroid glands localization is critical in the selection of minimally invasive parathyroidectomy as a surgical treatment approach in patients with primary hyperparathyroidism (PHPT). Its importance cannot be overemphasized as it helps to minimize the harmful side effects associated with damage to the parathyroid glands such as in hypocalcemia, severe hemorrhage or recurrent laryngeal nerve dysfunction. Preoperative and intraoperative methods decrease the incidence of mistakenly injuring the parathyroid glands and allow for the timely diagnosis of various abnormalities, including parathyroid adenomas. This article reviews 139 studies conducted between 1970 and 2020 (49 years). Studies that were reviewed focused on several techniques including application of carbon nanoparticles, carbon nanoparticles with technetium sestamibi (99m Tc-MIBI), Raman spectroscopy, near-infrared autofluorescence, dynamic optical contrast imaging, laser speckle contrast imaging, shear wave elastography, and indocyanine green to test their potential in providing proper parathyroid glands' localization. Apart from reviewing the aforementioned techniques, this study focused on the applications that helped in the detection of parathyroid adenomas. Results suggest that applying all the reviewed techniques significantly improves the possibility of providing proper localization of parathyroid glands, and the application of indocyanine green has proven to be the 'ideal' approach for the diagnosis of parathyroid adenomas.

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.

Autofluorescence in Parathyroidectomy: Signal Intensity Correlates with Serum Calcium and Parathyroid Hormone but Routine Clinical Use is Not Justified

BACKGROUND

The inability to identify the pathological gland at surgery results in failure to cure hyperparathyroidism in 2-5%. The poorly understood characteristic of parathyroid tissue to manifest autofluorescence (AF) under near-infrared (NIR) light has been promoted as an intraoperative adjunct in parathyroid surgery. This study sought to explore potential clinical correlates for AF and assess the clinical utility of AF in parathyroid surgery.

METHODS

Consecutive patients undergoing parathyroid surgery for primary and renal disease were included. NIR imaging was used intraoperatively and the degree of AF of parathyroid glands graded by the operating surgeon. Variables assessed for correlation with AF were: pre-operative serum calcium and PTH, SestaMIBI positivity, gland weight and histological composition.

RESULTS

Ninety-six patients underwent parathyroidectomy over an 8-month period: 49 bilateral explorations, 41 unilateral and 6 focussed lateral approaches: 284 potentially 'visualisable' glands in total. Two hundred and fifty-seven glands (90.5%) were visualised with NIR. Correlation was found between the degree of fluorescence and pre-operative serum calcium and PTH, but not between gland weight and SestaMIBI positivity. In those with renal hyperparathyroidism, a predominance of oxyphil cells correlated with increased AF.

CONCLUSION

Autofluorescence intensity correlates with serum calcium, PTH and gland composition. Further refinements would be required for this information to be of value in a clinical setting. Improvements allowing NIR to visualise the additional 9.5% of parathyroids and overcome the variation in signal intensity due to depth of access are required for the routine adoption of this technology. At present, its routine use in a clinical setting cannot be justified.

Evaluation of Parathyroid Glands with Indocyanine Green Fluorescence Angiography After Thyroidectomy

BACKGROUND

Indocyanine green fluorescence angiography (ICGA) is a new adjunct that has been used in surgical procedures to assess blood flow. This study evaluated the utility of ICGA compared to visual inspection to predict parathyroid function, guide autotransplantation and potentially decrease permanent hypoparathyroidism.

METHODS

This was a retrospective study of patients who underwent total or near-total thyroidectomy (T-NT) between January 2015 and March 2018. Patients with preoperative hyperparathyroidism and those undergoing reoperation were excluded. Patients who had ICGA were compared to T-NT patients without ICGA. Data were analyzed to assess the frequency of autotransplantation and incidence of hypoparathyroidism between groups.

RESULTS

In total, 210 patients underwent T-NT: 86 with ICGA and 124 without. Autotransplantation was more common in the ICGA group at 36% compared to 12% in the control (p = 0.0001). There was no correlation with at least one normal parathyroid gland on ICGA and postoperative PTH levels (p = 0.75). There was a difference in having normal postoperative PTH when there were at least two normal parathyroid glands (n = 50) compared to patients with less than two normal ICGA glands (n = 36, p = 0.044). Visual assessment and ICGA assessment of vascularity were in agreement, 245/281 (87%). There were 19 glands (6.8%) that would have undergone autotransplant based on visual inspection that had adequate blood supply on ICGA. Transient hypoparathyroidism was present in 45 out of 124 controls (36%) and 32 out of 86 (37%) in the ICG group.

CONCLUSIONS

ICGA is a novel technique that may improve the assessment of parathyroid gland blood supply compared to visual inspection. ICGA can guide more appropriate autotransplantation without compromising postoperative parathyroid function. At least two vascularized glands on ICGA may predict postoperative parathyroid gland function.

Indocyanine Green Fluorescence Angiography Can Guide Intraoperative Localization During Parathyroid Surgery

BACKGROUND AND AIMS

Intraoperative localization of pathologic parathyroid glands is of major importance for the hyperparathyroidism treatment. Based on the small size and the anatomic variability, the localization can be very challenging. The current practice is to compare preoperative ultrasonography with Technetium-99m sestamibi scintigraphy (MIBI) and plan the resection accordingly. In this study, we implemented indocyanine green angiography for the intraoperative localization of parathyroid glands.

MATERIALS AND METHODS

This is a retrospective analysis of 37 patients with primary, secondary, or tertiary hyperparathyroidism who were operated using indocyanine green angiography for the intraoperative localization of pathological parathyroid glands. An indocyanine green solution of 2.5 mg was were intravenously administered for parathyroid gland visualization. Different fluorescence scores were correlated with changes in postoperative parathyroid hormone levels.

RESULTS

Patients were divided into two groups depending on the presence of uniglandular or multiglandular disease. Sixty-four lesions were resected, and the final histopathologic analysis confirmed the parathyroid origin in 62 of them (96.8%). None of the patients with uniglandular disease developed postoperative hypoparathyroidism, whereas three patients in the multiglandular group developed temporary hypoparathyroidism symptoms. Indocyanine green imaging had higher sensitivity for the intraoperative detection of parathyroid glands compared with ultrasonography and MIBI (p < 0.001).

CONCLUSION

Indocyanine green angiography indicated high sensitivity for the intraoperative identification of pathologic parathyroid glands leading to a resection rate of 95.16%. The modality was useful, especially in cases of revisional surgery or ectopic parathyroid glands. Randomized trials have already proven the value of indocyanine green imaging in predicting postoperative hypocalcemia. Our results support the regular use of this method during parathyroid surgery.

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.

Impact of fluorescence and autofluorescence on surgical strategy in benign and malignant neck endocrine diseases

Fluorescence and autofluorescence have been shown by several recent studies to be valuable adjuncts in identifying parathyroid glands during thyroidectomy and parathyroidectomy. The aim of this chapter is to review the impact of this new technology on surgical strategy concerning identification and preservation of parathyroid glands during thyroidectomy, identification of parathyroid glands in hyperparathyroidism, and the potential role in thyroid cancer surgery.

Efficacy of indocyanine green fluorescence in predicting parathyroid vascularization during thyroid surgery

BACKGROUND

We examined the value of indocyanine green (ICG) fluorescence angiography in predicting parathyroid vascularization following thyroid and central compartment surgeries.

METHODS

Data were prospectively collected on adult patients undergoing thyroid and/or central compartment surgeries. Outcomes were compared in surgeries performed with and without ICG use. ICG scoring was used to quantify the vascularity of parathyroid glands.

RESULTS

One hundred eleven patients were included; 43 (38.7%) patients underwent ICG injections. There was no significant difference in mean parathyroid hormone (PTH) changes at the end of surgery (29.24 vs 23.48 pg/mL, P = .38), symptomatic hypocalcemia (7.9% vs 3.9%, P = .37), or length of stay (1.095 ± 0.22 vs 0.912 ± 0.07 days, P = .51) between surgeries performed with and without ICG. The average vascularization score among individuals undergoing ICG angiography was 2.89 out of a maximum of 8 points.

CONCLUSION

Low-flow ICG patterns are not associated with postoperative PTH changes or transient hypocalcemia and may lead to unnecessary parathyroid autotransplantation.

Intraoperative verification of parathyroid glands in primary and secondary hyperparathyroidism using near-infrared autofluorescence (IOPA)

Intraoperative verification of parathyroid glands relies on visual identification by the surgeon and, with some time delay, on serum parathormon measurements and frozen section. Fluorescence imaging, however, is an instant on-table method for direct visualization of parathyroid tissue which is known to exhibit increased autofluorescence intensity when exposed to near-infrared light. In this retrospective observational study, we evaluate the clinical use of this method in a series of patients with primary and secondary hyperparathyroidism. A total of 66 adenomatous and hyperplastic parathyroid glands were examined with intraoperative autofluorescence in 39 patients with primary and secondary hyperparathyroidism using a near-infrared system (KARL STORZ GmbH & Co. KG). The specimens were verified by conventional histology. Fifty-seven of 66 histologically proven adenomatous/hyperplastic glands exhibited autofluorescence. The sensitivity of near-infrared autofluorescence was 0.9 in pHPT and 0.83 in sHPT, respectively. The positive predictive value was 0.93 in pHPT and 1.0 in sHPT, respectively. Near-infrared autofluorescence guidance presents an innovative instant surgical imaging tool with sensitivity in detecting adenomatous and hyperplastic parathyroid glands comparable to current intraoperative methods. Due to its elegant and tracer-free design combined with low follow-up costs, this method can be useful for routine use.

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.

Feasibility of indocyanine green fluorescence imaging for intraoperative identification of parathyroid glands during thyroid surgery

Background

This study assessed the feasibility of near‐infrared fluorescence imaging with indocyanine green (ICG) to identify the parathyroid glands (PGs) intraoperatively and to assess their perfusion after thyroid resection.

Methods

Patients undergoing elective thyroidectomy were enrolled in this prospective study. An intravenous bolus of 7.5 mg ICG was administered twice: the first bolus to identify the PGs before resection of the thyroid and the second to assess vascularization of the PGs after resection.

Results

A total of 30 operations in 26 patients were included. In 17 surgeries (56.7%), fluorescence imaging was of added value, especially to confirm the presence of a suspected PG. No intraoperative or postoperative complications occurred because of the use of ICG.

Conclusion

Near‐infrared fluorescence imaging with the use of ICG for intraoperative identification of the PGs and the assessment of its vascularization is feasible and safe and can provide more certainty about the location of the PGs.

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.

Randomized clinical trial of intraoperative parathyroid gland angiography with indocyanine green fluorescence predicting parathyroid function after thyroid surgery

BACKGROUND

Hypoparathyroidism, the most common complication after thyroid surgery, leads to hypocalcaemia and significant medical problems. An RCT was undertaken to determine whether intraoperative parathyroid gland angiography with indocyanine green (ICG) could predict postoperative hypoparathyroidism, and obviate the need for systematic blood tests and oral calcium supplementation.

METHODS

Between September 2014 and February 2016, patients who had at least one well perfused parathyroid gland on ICG angiography were randomized to receive standard follow-up (measurement of calcium and parathyroid hormone (PTH) on postoperative day (POD) 1 and systematic supplementation with calcium and vitamin D; control group) or no supplementation and no blood test on POD 1 (intervention group). In all patients, calcium and PTH levels were measured 10-15 days after thyroidectomy. The primary endpoint was hypocalcaemia on POD 10-15.

RESULTS

A total of 196 patients underwent ICG angiography during thyroid surgery, of whom 146 had at least one well perfused parathyroid gland on ICG angiography and were randomized. None of these patients presented with hypoparathyroidism, including those who did not receive calcium supplementation. The intervention group was statistically non-inferior to the control group (exact 95 per cent c.i. of the difference in proportion of patients with hypocalcaemia -0·053 to 0·053; P = 0·012). Eleven of the 50 excluded patients, in whom no well perfused parathyroid gland could be identified by angiography, presented with hypoparathyroidism on POD 1, and six on POD 10-15, which was significantly different from the findings in randomized patients (P = 0·007).

CONCLUSION

ICG angiography reliably predicts the vascularization of the parathyroid glands and obviates the need for postoperative measurement of calcium and PTH, and supplementation with calcium in patients with at least one well perfused parathyroid gland. Registration number: NCT02249780 (http://www.clinicaltrials.gov).

Usefulness of near-infrared angiography for identifying the intersegmental plane and vascular supply during video-assisted thoracoscopic segmentectomy

OBJECTIVES

Segmentectomy by video-assisted thoracoscopic surgery (VATS) permits anatomical resection for diagnosis and treatment of small lung nodules but requires that intersegmental planes and segmental vessels be identified accurately. Near-infrared angiography with systemic injection of indocyanine green (ICG) can precisely identify the intersegmental plane. The purpose of this study was to confirm the usefulness of ICG angiography during VATS segmentectomy.

METHODS

We retrospectively reviewed the records of 22 consecutive patients who underwent VATS segmentectomy performed with near-infrared angiography between November 2014 and October 2015. Segments were localized and anatomical vascular supply was identified on preoperative computed tomography scans. VATS segmentectomy was performed using an anterior approach with 2 ports and 1 non-spreading minithoracotomy, with ICG injected systemically after arterial ligation.

RESULTS

VATS was feasible for all 22 segmentectomies, and in all patients, the intersegmental plane was identified accurately by ICG angiography. This angiography method was also useful in patients whose anatomical vascular segmentation was difficult to identify and, in a few patients, to assess the distribution of an artery before sectioning, to determine the vascular supply of the remaining lung and to distinguish between segmental and intersegmental veins. The postoperative course was uneventful for 18 patients and complicated for 2 patients who had prolonged air leak (10 and 15 days) with pneumonia, 1 patient with gastroparesis and 1 with colonic ileus. The drain was removed before the 3rd postoperative day in all but 2 patients, and the mean hospital stay was 5.4 ± 4.5 days. Anatomopathological examination indicated that 4 benign lesions and 18 primary lung cancers were completely removed, including 14 that were Stage IA, 2 Stage IIA and 2 Stage IIIA.

CONCLUSIONS

Indocyanine green angiography provides technical support for identifying the intersegmental plane and the vasculature during VATS segmentectomy. It contributes to the quality of diagnostic and therapeutic excisions of small nodules that are often not visible and not palpable during VATS.

Indocyanine green fluorescence-guided parathyroidectomy for primary hyperparathyroidism

BACKGROUND

Our aim was to evaluate the ease and utility of using indocyanine green fluorescence angiography for intraoperative localization of the parathyroid glands.

METHODS

Indocyanine green fluorescence angiography was performed during 60 parathyroidectomies for primary hyperparathyroidism during a 22-month period. Indocyanine green was administered intravenously to guide operative navigation using a commercially available fluorescence imaging system. Video files were graded by 3 independent surgeons for strength of enhancement using an adapted numeric scoring system.

RESULTS

There were 46 (77%) female patients and 14 (23%) male patients whose ages ranged from 17 to 87 (average 60) years old. Of the 60 patients, 43 (71.6%) showed strong enhancement, 13 (21.7%) demonstrated mild to moderate vascular enhancement, and 4 (6.7%) exhibited little or no vascular enhancement. Of the 54 patients who had a preoperative sestamibi scan, a parathyroid adenoma was identified in 36, while 18 failed to localize. Of the 18 patients who failed to localize, all 18 patients (100%) had an adenoma that fluoresced on indocyanine green imaging. The operations were performed safely with minimal blood loss and short operative times.

CONCLUSION

Indocyanine green angiography has the potential to assist surgeons in identifying parathyroid glands rapidly with minimal risk.

A reappraisal of vascular anatomy of the parathyroid gland based on fluorescence techniques

Identification of the parathyroid glands (PGs) during thyroid surgery may prevent their inadvertent surgical removal and prevent postoperative hypoparathyroidism. However, identification of the PGs does not guarantee their function, and their vascular supply needs to be preserved as well. The recent introduction of intraoperative indocyanine green (ICG) fluorescent angiography of the PGs during thyroid surgery allows for the appraisal of the vascular anatomy and evaluation of PG function. The use of this tool could lead to a significant reduction in the rate of postoperative hypoparathyroidism, as it allows surgeons to adapt their surgical technique for the preservation of the PGs. ICG fluorescent angiography is currently the only available real-time tool to assess the vascular blood supply of each individual PG intraoperatively and can thus assist surgeons in their decision-making. Herein, we review the relevant literature.

The use of ICG enhanced fluorescence for the evaluation of parathyroid gland preservation

Indocyanine green (ICG) enhanced fluorescence imaging is recent innovation as the "real-time intraoperative imaging" technique. Many clinical studies have been reported in the literature which use different devices and techniques that employ various doses and usages of ICG as a non-specific contrast agent. Several groups have performed studies in endocrine surgery, especially with regards to parathyroid-related outcomes after thyroid and parathyroid surgery. However, there is no consensus on the technical details that should be applied. With this study, we aimed to review the current literature on potential use of intraoperative ICG angiography for evaluating parathyroid gland (PTG) preservation.

The use of near-infrared fluorescence imaging in endocrine surgical procedures

Near-infrared fluorescence imaging in endocrine surgery is a new, yet highly investigated area. It involves indocyanine green use as well as parathyroid autofluorescence. Several groups have described their technique and reported on the observed utility. However, there is no consensus on technical details. Furthermore, the correlation between intraoperative findings and postoperative outcomes is unclear. With this study, we aim to review the current literature on fluorescence imaging and share our insights on technical details.

INCIDENTAL PARATHYROIDECTOMY DURING THYROID SURGERY - RISK, PREVENTION AND CONTROVERSIES; AN EVIDENCE-BASED REVIEW

Background

Postoperative hypocalcemia after thyroid surgery has a high prevalence ( 16-55% in different series). Incidental parathyroidectomy (IP) is a less discussed complication of thyroidectomy with consequences not properly defined. The aim of our study was to find incidence, risk factors and how to prevent IP.

Methods

Extensive search of English literature publications via PubMed was performed and 73 papers from 1980 to 2017 were analysed using the GRADE system/classification, quality of evidence was classified as "strong" when the result is highly unlikely to change existing recommendation and "weak" when opposite.

Results

Incidence of IP is 3.7-24.9%, while prevalence of permanent hypoparathyroidism is less frequent 6-12%. Direct relation between IP and hypoparathyroidism/hypocalcemia remains controversial. Female patients, ectopic parathyroids, small thyroids, Graves', malignancy, redo surgeries and total thyroidectomy favour IP. Routine visualization of parathyroids, new hemostatic devices, magnifying instruments and fluorescence can prevent incidental removal of parathyroids. Incidence of IP during videoassisted or robotic thyroidectomies was similar to open procedures. High volume, experienced and younger surgeons have lower complication rates (including hypoparathyroidism).

Conclusions

Incidental parathyroidectomy is more frequent than we might have expected. It should be avoided and parathyroid glands should be kept in situ. Majority of studies are retrospective (low degree of evidence according to previous mentioned GRADE classification) and further meta-analysis or randomized control studies are welcome in order to define the impact of incidental removal of parathyroids on postoperative outcome.