Intraoperative photodynamic detection of normal parathyroid glands using 5-aminolevulinic acid

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.

RNA-Seq-based transcriptomics analysis during the photodynamic therapy of primary cells in secondary hyperparathyroidism

BACKGROUND

The aim of this study was to identify changes in gene expression before and after 5-aminolevulinic acid-mediated photodynamic therapy (5-ALA-PDT) and to investigate the potential mechanism of 5-ALA-PDT based on ribonucleic acid sequencing (RNA-Seq) analysis.

METHODS

Secondary hyperparathyroidism (SHPT) primary cells were isolated from surgically excised specimens and exposed to laser light. The transcription profiles of SHPT primary cells were identified through RNA-Seq. Differentially expressed genes (DEGs) were identified. Enrichment of functions and signaling pathway analysis were performed based on Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) analyses. Quantitative real-time polymerase chain reaction (RT-qPCR) and western blot analysis were used to validate genes based on RNA-Seq results.

RESULTS

In total, 1320 DEGs were identified, of which 1019 genes were upregulated and 301 genes were downregulated. GO and KEGG pathway analyses identified significantly enriched pathways in DEGs, including TGF beta in extracellular matrix (ECM), negative regulation of triglyceride biosynthetic process, protein heterodimerization activity, systemic lupus erythematosus, ECM-receptor interaction, focal adhesion and protein digestion and absorption. Protein-protein interaction (PPI) network analyses identified potential heat shock protein (HSP) interactions among the DEGs. Eight HSP genes were also identified that were most likely involved in 5-ALA-PDT, which were further validated by RT-qPCR and western blotting.

CONCLUSIONS

The findings of this descriptive study reveal changes in the transcriptome profile during 5-ALA-PDT, suggesting that gene expression and mutation, signaling pathways, and the molecular network are altered in SHPT primary cells. The above findings provide new insight for further studies on the mechanisms underlying 5-ALA-PDT in SHPT.

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

Objectives

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

Methods

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

Results

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

Conclusions

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

Update on Preoperative Parathyroid Localization in Primary Hyperparathyroidism

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

Intraoperative identification of parathyroid glands during endocrine surgery

Nowadays, diabetes and diseases of thyroid gland take place on the first two stage in the rank of all endocrine diseases. There are 3 directions to treat thyroid glands pathologies such as: using special pills which substitute natural thyroid hormones, surgery and radioiodine therapy. It has proven that surgery of thyroid gland is the most effective method among considering upper. at The same time, it is associated with the greatest risks of complications. The most common injuries are damage to the recurrent laryngeal nerve and unintentional traumatization or removal of a healthy parathyroid gland. Parathyroid gland is a critical organ during thyroid surgery. It means that all negative reaction nearby the structure can lead to development different complications: hypoparathyroidism (transient or chronic) and hypocalcemia. In this article is considered actual methods of intraoperative optical visualization of parathyroid glans. The fundamental foundations of such methods, their advantages and disadvantages are also analyzed. It is shown that fluorescent methods in the red and near infrared regions of the spectrum using exogenous dyes have essential importance for endocrine surgery, as they allow to improve identification and reduce the risk of postoperative complications.

Autofluorescence of parathyroid glands during endocrine surgery with minimally invasive technique

PURPOSE

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

METHODS

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

RESULTS

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

CONCLUSION

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

Thyroidectomy for Cancer: The Surgeon and the Parathyroid Glands Sparing

BACKGROUND

The diagnosis of thyroid cancer is continuously increasing and consequently the amount of thyroidectomy. Notwithstanding the actual surgical skill, postoperative hypoparathyroidism still represents its most frequent complication. The aims of the present study are to analyze the rate of postoperative hypoparathyroidism after thyroidectomy, performed for cancer by a single first operator, without any technological aid, and to compare the data to those obtained adopting the most recent technological adjuncts developed to reduce the postoperative hypoparathyroidism.

METHODS

During the period 1997-2020 at the Endocrine Surgery Unit of the Department of Clinical and Experimental Medicine of the University of Florence, 1648 consecutive extracapsular thyroidectomies for cancer (401 with central compartment node dissection) were performed. The percentage of hypoparathyroidism, temporary or permanent, was recorded both in the first period (Group A) and in the second, most recent period (Group B). Total thyroidectomies were compared either with those with central compartment dissection and lobectomies. Minimally invasive procedures (MIT, MIVAT, some transoral) were also compared with conventional. Fisher's exact and Chi-square tests were used for comparison of categorical variables. p < 0.01 was considered statistically significant. Furthermore, a literature research from PubMed^® has been performed, considering the most available tools to better identify parathyroid glands during thyroidectomy, in order to reduce the postoperative hypoparathyroidism. We grouped and analyzed them by technological affinity.

RESULTS

On the 1648 thyroidectomies enrolled for the study, the histotype was differentiated in 93.93 % of cases, medullary in 4% and poorly differentiated in the remaining 2.06%. Total extracapsular thyroidectomy and lobectomy were performed respectively in 95.45% and 4.55%. We recorded a total of 318 (19.29%) cases of hypocalcemia, with permanent hypoparathyroidism in 11 (0.66%). In regard to the literature, four categories of tools to facilitate the identification of the parathyroids were identified: (a) vital dye; (b) optical devices; (c) autofluorescence of parathyroids; and (d) autofluorescence enhanced by contrast media. Postoperative hypoparathyroidism had a variable range in the different groups.

CONCLUSIONS

Our data confirm that the incidence of post-surgical hypoparathyroidism is extremely low in the high volume centers. Its potential reduction adopting technological adjuncts is difficult to estimate, and their cost, together with complexity of application, do not allow immediate routine use. The trend towards increasingly unilateral surgery in thyroid carcinoma, as confirmed by our results in case of lobectomy, is expected to really contribute to a further reduction of postsurgical hypoparathyroidism.

Methylene Blue Spray for Identification of Parathyroid Glands During Thyroidectomy

Background: Hypocalcaemia is a common delayed complication after thyroidectomy. Several studies have identified risk factors and possible ways to prevent post-thyroidectomy hypocalcemia. The purpose of our study is to evaluate the effectiveness of an intraoperative methylene blue spray to identify parathyroid glands during thyroidectomy.

Materials and methods: We have conducted a prospective non-randomised cohort study with 50 patients who underwent hemithyroidectomy or total thyroidectomy between January 2019 and January 2020. During thyroidectomy, 1 ml (10 mg) of 1% methylene blue was sprayed over the parathyroid glands, the inferior thyroid artery, and the recurrent laryngeal nerve.

Results: Our study included 50 patients with ages ranging from 18 to 80 years old (43.0±9.7). We were able to identify the parathyroid glands with the intraoperative methylene blue spray in 82% of cases, with no significant postoperative complications.

Conclusion: Our study concludes that the methylene blue spray is a safe, feasible, and effective technique to identify parathyroid glands.

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.

Near-Infrared Fluorescence Imaging in the Identification of Parathyroid Glands in Thyroidectomy

OBJECTIVES/HYPOTHESIS

To assess the ability of near-infrared fluorescence imaging (NIFI) to identify parathyroid glands (PGs) among histologically proven PG/non-PG specimens compared with a surgeon's visual acumen, and to determine NIFI sensitivity in detecting incidentally resected PGs from thyroidectomy specimens, compared to the surgeon's visual inspection.

STUDY DESIGN

Prospective study.

METHODS

With mean age of 61 years, 36 patients with various thyroid diseases were enrolled. Possible PGs (n = 28) and lymph nodes (n = 32) were identified by the experienced surgeon's visual inspection. Using NIFI, 15 PGs were further identified from thyroidectomy specimens. For these 75 specimens, the surgeon's judgments (PG vs. non-PG) were recorded. Histological evaluation was performed after examining the NIFI auto-fluorescence of each specimen.

RESULTS

There were no significant differences in sensitivity, specificity, positive predictive value, and negative predictive value between the surgeon's visual inspection and NIFI in identifying PGs, with values of 100%/97.1%, 85.0%/87.5%, 85.4%/87.2%, and 100%/97.2%, respectively. The sensitivity of NIFI (82.9%) for detection of PGs from thyroidectomy specimens was significantly higher than that of the surgeon's visual inspection (61.0%). False negative specimens contained bleeding/congestion and/or encapsulation by thick tissues, whereas false positive specimens contained electrocoagulated tissues.

CONCLUSIONS

NIFI showed results comparable to the experienced surgeon's visual inspection in identifying PGs. This could benefit novice surgeons. NIFI may be useful for experienced surgeons to locate incidentally resected PGs within thyroidectomy specimens for auto-transplantation. Prevention of intra-gland bleeding and congestion, careful removal of thick capsules, and bloodless surgeries without electrocoagulation are important for reducing false positive and false negative results. Laryngoscope, 131:1188-1193, 2021.

Indocyanine green fluorescence angiography-guided transoral endoscopic thyroidectomy and parathyroidectomy: First clinical report

BACKGROUND

Indocyanine green fluorescence (ICG) angiography has been used for many purposes including as part of a focused parathyroidectomy technique. Concomitant fluorescence of thyroid tissue may cause challenges defining parathyroid tissue during surgery, since ICG is not a selective fluorescent agent. On the other hand, cosmesis is still a big problem for patients due to the visible neck scars produced by the standard surgical technique. In this study, we described a novel technique to solve both these handicaps.

MATERIALS AND METHODS

Seven patients who underwent ICG fluorescence angiography-guided transoral endoscopic thyroidectomy and parathyroidectomy vestibular approach between February 2018 and July 2019 were included. Serum parathyroid hormone (PTH) levels were measured intraoperatively and on postoperative day 1. Fluorescent images were confirmed with intraoperative quick-PTH levels.

RESULTS

All operations were done successfully without conversion to open surgery. Intense and isolated parathyroid fluorescent images were achieved in all operations. All patients had a 50 % decrease between the baseline and final quick-PTH levels and the final quick-PTH levels were in the normal range in all. One of 7 patients had epistaxis due to nasotracheal intubation. One of 7 patients had seroma on post-operative day 5. None of patients had mental nerve injury, permanent hypocalcemia and temporary or permanent recurrent laryngeal nerve injury.

CONCLUSION

ICG-guided transoral endoscopic thyroid and parathyroid surgery can be used in select patients to increase operative success in focused parathyroidectomy with excellent cosmetic outcome also noted.

Delta-Aminolevulinic Acid-Mediated Photodiagnoses in Surgical Oncology: A Historical Review of Clinical Trials

Fluorescence imaging is an emerging clinical technique for real-time intraoperative visualization of tumors and their boundaries. Though multiple fluorescent contrast agents are available in the basic sciences, few fluorescence agents are available for clinical use. Of the clinical fluorophores, delta aminolevulinic acid (5ALA) is unique for generating visible wavelength tumor-specific fluorescence. In 2017, 5ALA was FDA-approved for glioma surgery in the United States. Additionally, clinical studies suggest this agent may have utility in surgical subspecialties outside of neurosurgery. Data from dermatology, OB/GYN, urology, cardiothoracic surgery, and gastrointestinal surgery show 5ALA is helpful for intraoperative visualization of malignant tissues in multiple organ systems. This review summarizes data from English-language 5ALA clinical trials across surgical subspecialties. Imaging systems, routes of administration, dosing, efficacy, and related side effects are reviewed. We found that modified surgical microscopes and endoscopes are the preferred imaging devices. Systemic dosing across surgical specialties range between 5 and 30 mg/kg bodyweight. Multiple studies discussed potential for skin irritation with sun exposure, however this side effect is infrequently reported. Overall, 5ALA has shown high sensitivity for labeling malignant tissues and providing a means to visualize malignant tissue not apparent with standard operative light sources.

Parathyroid Autofluorescence-How Does It Affect Parathyroid and Thyroid Surgery? A 5 Year Experience

Injury to parathyroid glands during thyroid and parathyroid surgery is common and postoperative hypoparathyroidism represents a serious complication. Parathyroid glands possess a unique autofluorescence in the near-infrared spectrum which could be used for their identification and protection at an early stage of the operation. In the present study parathyroid autofluorescence was visualized intraoperatively using a standard Storz laparoscopic near-infrared/indocyanine green (NIR/ICG) imaging system with minor modifications to the xenon light source (filtered to emit 690 nm to 790 nm light, less than 1% in the red and green above 470 nm and no blue light). During exposure to NIR light parathyroid tissue was expected to show autofluorescence at 820 nm, captured in the blue channel of the camera. Over a period of 5 years, we investigated 205 parathyroid glands from 117 patients. 179 (87.3%) glands were correctly identified by their autofluorescence. Surrounding structures such as thyroid, lymph nodes, muscle, or adipose tissue did not reveal substantial autofluorescence. We conclude that parathyroid glands can be identified by their unique autofluorescence at an early stage of the operation. This may help to preserve these fragile structures and their vascularization and lower the rate of postoperative hypocalcemia.

The sensitivity and specificity of methylene blue spray to identify the parathyroid gland during thyroidectomy

Background

Hypocalcemia is a common complication of thyroidectomy resulting from an injury to the parathyroid gland. Methylene blue, which is a medication and dye that has been used for more than a century, is safe and readily available. The previous study has found that methylene blue spray on the surgical field is absorbed by the parathyroid gland faster than in the perithyroidal area. This study was aimed to evaluate the diagnostic value of methylene blue spray to identify the parathyroid gland during thyroid lobectomy.

Methods

Patients who underwent thyroid lobectomy were recruited. After the recurrent laryngeal nerve was identified, methylene blue was sprayed onto the thyroid bed. After 5 min, the thyroid bed was inspected for areas in which the blue color had been rapidly absorbed. Biopsies were conducted for histopathology at both the stained area and the area in which the color had faded. The sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) were calculated.

Results

A total of 47 patients participated in this study. The sensitivity of methylene blue spray to identify the parathyroid gland during thyroid lobectomy was 92.31% (95% CI [63.97–99.81]) and specificity was 56.79% (95% CI [45.31–67.76]). The PPV was 25.53% (95% CI [20.34–31.53]) and NPV was 97.87% (95% CI [87.39–99.67]). There were no patients with post-operative hypocalcemia, allergic reactions to the methylene blue, or methylene blue toxicity.

Conclusion

The methylene blue spray could serve as a screening tool for identification of the parathyroid gland.

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.

Near-infrared autofluorescence imaging to detect parathyroid glands in thyroid surgery

Objective To identify and save parathyroid glands during thyroidectomy by displaying their autofluorescence. Methods Autofluorescence imaging was carried out during thyroidectomy with and without central lymph node dissection. After visual recognition by the surgeon, the parathyroid glands and the surrounding tissue were exposed to near-infrared light with a wavelength of 690-770 nm using a modified Karl Storz near infrared/indocyanine green endoscopic system. Parathyroid tissue was expected to show near infrared autofluorescence at 820 nm, captured in the blue channel of the camera. Results We investigated 41 parathyroid glands from 20 patients; 37 glands were identified correctly based on near-infrared autofluorescence. Neither lymph nodes nor thyroid revealed substantial autofluorescence and nor did adipose tissue. Conclusions Parathyroid tissue is characterised by showing autofluorescence in the near-infrared spectrum. This effect can be used to identify and preserve parathyroid glands during thyroidectomy.

Automatic identification of parathyroid in optical coherence tomography images

BACKGROUND AND OBJECTIVE

The identification and preservation of parathyroid is a major problem in thyroid surgery. In order to solve this problem, optical coherence tomography was involved as a real-time, non-invasive high-resolution imaging technique. This study demonstrated an effective and fast method to distinguish parathyroid tissue from thyroid, lymph node, and adipose tissue in their ex vivo optical coherence tomography (OCT) images automatically.

METHODS

OCT images were obtained from parathyroid, thyroid, lymph node, and adipose tissue, respectively. A classification and an identification system based on texture features analysis and back propagation artificial neural network (BP-ANN) were established to classify the four types of tissue and identify each of the four types automatically.

RESULTS

A total of 248 OCT images were taken from 16 patients undergoing thyroidectomy. The accuracy of classification for parathyroid, thyroid, lymph node, and adipose were 99.21, 98.43, 97.65, and 98.43%, respectively.

CONCLUSION

The proposed automatic identification method is capable of distinguishing among parathyroid, thyroid, lymph, and adipose automatically and effectively. Compared with the identification results of human, it has a better accuracy and reliability. For identifying parathyroid from the other entities, it has a satisfying performance. Lasers Surg. Med. 49:305-311, 2017. © 2017 Wiley Periodicals, Inc.

Intraoperative near-infrared autofluorescence imaging of parathyroid glands

OBJECTIVE

To identify parathyroid glands intraoperatively by exposing their autofluorescence using near-infrared light.

METHODS

Fluorescence imaging was carried out during minimally invasive and open parathyroid and thyroid surgery. After identification, the parathyroid glands as well as the surrounding tissue were exposed to near-infrared (NIR) light with a wavelength of 690-770 nm using a modified Karl Storz near-infrared/indocyanine green (NIR/ICG) endoscopic system. Parathyroid tissue was expected to show near-infrared autofluorescence, captured in the blue channel of the camera. Whenever possible the visual identification of parathyroid tissue was confirmed histologically.

RESULTS

In preliminary investigations, using the original NIR/ICG endoscopic system we noticed considerable interference of light in the blue channel overlying the autofluorescence. Therefore, we modified the light source by interposing additional filters. In a second series, we investigated 35 parathyroid glands from 25 patients. Twenty-seven glands were identified correctly based on NIR autofluorescence. Regarding the extent of autofluorescence, there were no noticeable differences between parathyroid adenomas, hyperplasia and normal parathyroid glands. In contrast, thyroid tissue, lymph nodes and adipose tissue revealed no substantial autofluorescence.

CONCLUSION

Parathyroid tissue is characterized by showing autofluorescence in the near-infrared spectrum. This effect can be used to distinguish parathyroid glands from other cervical tissue entities.

Backscattering intensity measurements in optical coherence tomography as a method to identify parathyroid glands

BACKGROUND AND OBJECTIVE

Previous studies have shown that the use of optical coherence tomography (OCT) permits the differentiation between parathyroid tissue, thyroid tissue, lymph nodes and adipose tissue. We investigated the backscattering intensity profiles of OCT images in order to determine whether significant differences between these tissue types exist.

METHODS

Mean backscattering intensity profiles were obtained from OCT images of parathyroid glands, thyroid tissue, lymph nodes and adipose tissue. The profiles were analyzed employing Fisher's Linear Discriminant Analysis (LDA). The results were cross validated employing improved parameter estimation techniques.

RESULTS

Mean backscattering intensity profiles from 300 OCT images of 34 patients undergoing thyroid or parathyroid surgery were analyzed. The overall rate of correct classifications was 96.15%. The cross validation employing improved parameter estimation techniques yielded results identical to those derived from Fisher's LDA.

CONCLUSION

Besides the individual assessment of OCT images by interpreting morphological criteria, backscattering intensity measurements can reliably distinguish between different tissue entities.

Aetiology, Diagnosis and Surgical Treatment of Primary Hyperparathyroidism in Children: New Trends

Primary hyperparathyroidism (PHPT) in children is a rare disorder with sharp contrasts in its presentation and aetiology compared with the disease process in adults. This review outlines the current literature, which is limited to about 200 cases, with reference to the aetiology, clinical features, outcomes of investigations, and surgery in children affected by PHPT. Familial conditions account for almost half of all cases of PHPT in children, suggesting that routine genetic testing would be appropriate. Neonatal severe hyperparathyroidism requires urgent medical attention, and performing total parathyroidectomies offers cure, though conservative management is successful in selected cases. Familial hyperparathyroidism in older children can be caused by conditions such as multiple endocrine neoplasia types 1 and 2a, hyperparathyroidism-jaw tumour syndrome and familial hyperparathyroidism. The role of surgery for this group is discussed. The use of ultrasound and MIBI (99mTc-methoxyisobutylnitrile) scanning appears to accurately localise solitary adenomas in sporadic PHPT, thereby supporting the role of minimally invasive parathyroidectomy in children. © 2015 S. Karger AG, Basel.

Identification of pathological and normal parathyroid tissue by fluorescent labeling with 5-aminolevulinic acid during endocrine neck surgery

BACKGROUND

When performing parathyroid or thyroid surgery, surgeons must distinguish parathyroid tissue from the surrounding thyroid tissue, to preserve healthy parathyroid tissue while excising diseased thyroid tissue or to completely remove pathological parathyroid lesions. Here, we explored the feasibility of labeling the parathyroid glands for easy identification by administering 5-aminolevulinic acid (5-ALA) orally to patients undergoing endocrine neck surgery, because 5-ALA accumulates in the parathyroid and has a fluorescent metabolite, protoporphyrin IX.

METHODS

Twenty-nine patients about to undergo endocrine (parathyroid or thyroid gland) neck surgery were orally given 5-ALA, a nontoxic substance that occurs naturally in the human body and has no known major side effects. During surgery, we used blue light to excite protoporphyrin IX, the fluorescent metabolite of 5-ALA, and viewed the resulting bright red fluorescence through an optical filter.

RESULTS

In the majority of the patients, the parathyroid glands were defined by a clear fluorescence. In 23 patients with pathological parathyroid tissue, the fluorescence enabled us to identify and completely remove diseased parathyroid tissue. In 3 patients with thyroid disease, we were able to easily remove diseased thyroid tissue, and an accidentally removed parathyroid gland was autotransplanted during surgery.

CONCLUSIONS

In all but a few cases, 5-ALA clearly labeled parathyroid tissue, allowing for its clean removal or preservation according to the purpose of the surgery. This simple, benign technique is extremely useful for identifying parathyroid tissue, whether pathological or normal, during endocrine neck surgery.

X-ray fluorescence-based differentiation of neck tissues in a bovine model: implications for potential intraoperative use

This study explores the possibility of using X-ray fluorescence (XRF)-based trace-element analysis for differentiation of various bovine neck tissues. It is motivated by the requirement for an intra-operative in-vivo method for identifying parathyroid glands, particularly beneficial in surgery in the central neck-compartment. Using a dedicated X-ray spectral analysis, we examined ex-vivo XRF spectra from various histologically verified fresh neck tissues from cow, which was chosen as the animal model; these tissues included fat, muscle, thyroid, parathyroid, lymph nodes, thymus and salivary gland. The data for six trace elements K, Fe, Zn, Br, Rb and I, provided the basis for tissue identification by using multi-parameter analysis of the recorded XRF spectra. It is shown that the combination of XRF signals from these elements is sufficient for a reliable tissue differentiation. The average total abundance of these trace elements was evaluated in each tissue type, including parathyroid and salivary gland for the first time. It is shown that some tissues can unequivocally be identified on the basis of the abundance of a single element, for example, iodine and zinc for the identification of thyroid gland and muscle, respectively.

Intraoperative optical coherence tomography imaging to identify parathyroid glands

OBJECTIVE

Optical coherence tomography (OCT) is a non-invasive high-resolution imaging technique that permits characterization of microarchitectural features in real time. Previous ex vivo studies have shown that the technique is capable of distinguishing between parathyroid tissue, thyroid tissue, lymph nodes, and adipose tissue. The purpose of this study was to evaluate the practicality of OCT during open and minimally invasive parathyroid and thyroid surgery.

METHODS

During parathyroid and thyroid surgery, OCT images were generated from parathyroid glands, thyroid tissue, lymph nodes, and adipose tissue. The images were immediately assessed by the operating team using the previously defined criteria. Second, the OCT images were blinded with respect to their origin and analyzed by two investigators. Whenever possible the OCT findings were matched to the corresponding histology.

RESULTS

A total of 227 OCT images from 27 patients undergoing open or minimally invasive thyroid or parathyroid surgery were analyzed. Parathyroid glands were correctly identified in 69.2%, thyroid tissue in 74.5%, lymph nodes in 37.5%, and adipose tissue in 69.2%. 43 OCT images (18.9%) could not be allocated to one of the tissue types (Table 2). Sensitivity and specificity in distinguishing parathyroid tissue from the other entities were 69% (63 true positive, 13 false negative findings, 15 images where an allocation was not possible) and 66%, respectively (71 true negative, 9 false positive, 28 images where an assessment was not possible).

CONCLUSION

OCT is capable of distinguishing between parathyroid, thyroid, and adipose tissue. An accurate differentiation between parathyroid tissue and lymph nodes was not possible. The disappointing results compared to the previous ex vivo study are related to problems handling the endoscopic probe intraoperatively. However, further refinement of this new technology may lead to OCT systems with higher resolution and intraoperative probes that are easier to handle.

Indocyanine green as a near-infrared fluorescent agent for identifying parathyroid glands during thyroid surgery in dogs

BACKGROUND

Surgical procedures involving the thyroid gland require identification of the parathyroid glands. Indocyanine green (ICG) is a near-infrared (NIR) fluorescent contrast agent used for a variety of procedures such as intraoperative angiography, extrahepatic cholangiography, and lymph node mapping. In this study, we used a canine model to evaluate ICG for NIR fluorescent imaging of the parathyroid gland.

METHODS

Three dogs were used for the study. The dogs were administered general anesthesia, and after surgical dissection, each dog received a series of intravenous ICG doses ranging from 12.5 to 100 µg/kg ICG. The excitation light source used to illuminate the operating field was a NIR laser (λ = 785 nm). Intravascular ICG fluorescence (λ = 835/45 nm) was recorded using a charge-coupled device that employed optical filtering to block ambient and laser light. Fluorescent imaging was assessed after injection of each dose of ICG.

RESULTS

NIR fluorescent imaging visualized the parathyroid glands. The intensity curves showing the peak and plateau of fluorescence are similar regardless of the concentration of ICG. The time to peak fluorescent intensity was 50.2 ± 2.0 s after injection of ICG. Taking into consideration background fluorescent intensity, the estimated optimal dose of ICG was 18.75 µg/kg. At 106.7 ± 5.8 s, the parathyroid glands lost much of their fluorescence, although they remained sufficiently fluorescent to be distinguishable. There was a positive correlation of fluorescent intensity with ICG dose escalation up to 25 µg/kg.

CONCLUSIONS

ICG NIR fluorescent imaging was useful in detecting the parathyroid glands of dogs. By allowing detection of parathyroid glands, the current technique shows promise for use by endocrine surgeons performing thyroidectomies.

Optical coherence tomography as a method to identify parathyroid glands

BACKGROUND AND OBJECTIVE

The identification of parathyroid glands can be a major problem in parathyroid surgery. The purpose of this study was to evaluate the feasibility of optical coherence tomography (OCT) in distinguishing between parathyroid tissue, thyroid tissue, lymph nodes, and adipose tissue.

METHODS

Ex vivo OCT images as well as histological sections were generated from parathyroid glands, thyroid tissue, lymph nodes and fat in order to define significant morphologic differences between these entities. As a second step all OCT images were separately evaluated by two blinded investigators and later compared to the corresponding histology. Sensitivity and specificity of OCT in distinguishing between the different tissues were determined. To assess the interobserver agreement, κ coefficients were calculated from the ratings of each investigator for each OCT image seen.

RESULTS

A total of 320 OCT images from 32 patients undergoing thyroid surgery, parathyroidectomy or lymphadenectomy were compared with the corresponding histology. The sensitivity and specificity in distinguishing parathyroid tissue from the other entities was 84% (second investigator: 82%) and 94% (93%) respectively. Unweighted κ using four diagnostic categories was 0.97 (95% CI, 0.94-0.99) showing substantial agreement between both investigators.

CONCLUSION

OCT is highly sensitive in distinguishing between parathyroid tissue, thyroid tissue, lymph nodes and adipose tissue. These ex vivo results should be confirmed by using OCT imaging intraoperatively.