Intraoperative near-infrared fluorescence imaging of parathyroid adenomas with use of low-dose methylene blue

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.

Test method for evaluating the photocytotoxic potential of fluorescence imaging products

Various fluorescence imaging agents are currently under clinical studies. Despite significant benefits, phototoxicity is a barrier to the clinical translation of fluorophores. Current regulatory guidelines on medication-based phototoxicity focus on skin effects during sun exposure. However, with systemic and local administration of fluorophores and targeted illumination, there is now possibility of photochemical damage to deeper tissues during intraoperative imaging procedures. Hence, independent knowledge regarding phototoxicity is required to facilitate the development of fluorescence imaging products. Previously, we studied a cell-free assay for initial screening of reactive molecular species generation from fluorophores. The current work addresses a safety test method based on cell viability as an adjunct and a comparator with the cell-free assay. Our goal is to modify and implement an approach based on the in vitro 3T3 neutral red uptake assay of the Organization for Economic Co-Operation and Development Test Guideline 432 (OECD TG432) to evaluate the photocytotoxicity of clinically relevant fluorophores. These included indocyanine green (ICG), proflavine, methylene blue (MB), and IRDye800, as well as control photosensitizers, benzoporphyrin derivative (BPD) and rose bengal (RB). We performed measurements at agent concentrations and illumination parameters used for clinic imaging. Our results aligned with prior studies, indicating photocytotoxicity in RB and BPD and an absence of reactivity for ICG and IRDye800. DNA interactive agents, proflavine and MB, exhibited drug/light dose-response curves like photosensitizers. This study provides evidence and insights into practices useful for testing the photochemical safety of fluorescence imaging products.

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.

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.

Intraoperative uses of near-infrared fluorescence spectroscopy in pediatric surgery: A systematic review

BACKGROUND

The application of near infrared spectroscopy (NIRS) imaging in surgery is growing. This study aimed to systematically review the literature to summarize the intraoperative uses of NIRS in pediatric surgery.

METHODS

A PRISMA-compliant literature search was conducted in PubMed, Embase, Scopus, and Web of Science from inception to February 2020. Title/abstract and then full-text screening were performed. The Oxford centre for Evidence Based Medicine tool (OCEBM) was used to evaluate the level of evidence of included studies.

RESULTS

Reviewers identified 53 articles. Of which, 34 studies (64.2%) were case-series and 11 (20.8%) were case reports. Most of the studies (n = 45, 84.9%) were level 4 on the OCEBM tool. The most common uses of NIRS were to visualize the biliary tree and to identify primary and metastatic malignant tissues. Other applications include assessment of perfusion of tissues including bowel anastomoses, and lymphatic surgery. Several advantages of the introduction of NIRS in pediatric surgery exist including having the potential to reduce operative time and intra/post-operative complications. Moreover, NIRS helps in detecting malignant tissues that can be missed by conventional imaging. However, NIRS has important limitations such as difficulty in identification of the biliary tree in obese patients or inflamed gallbladder, detection of small deeply localized malignant tissues, as well as the high cost.

CONCLUSIONS

NIRS is a promising modality that can be used intraoperatively to augment different pediatric surgical procedures. NIRS has important advantages and limitations compared to conventional surgery, however, more studies are required to evaluate its outcomes and cost-effectiveness.

LEVEL OF EVIDENCE

IV.

Solar Heterogenous Photocatalytic Degradation of Methylthionine Chloride on a Flat Plate Reactor: Effect of pH and H2O2 Addition

Methylthionine chloride (MTC) is a compound with several applications both in the clinical and medical industries. Nevertheless, such compounds can become an environmental problem, as they are not properly treated by wastewater treatment plants. This objective of this work was to study MTC degradation in a flat plate reactor through solar photolysis and heterogeneous photocatalysis processes with TiO2 as a catalyst. In addition to the processes, three pH (3.5, 6.5, and 9) and the effect of H2O2 addition (no dose, 0.5, and 1 mM/L) were tested. The results show that acidic pH is the most appropriate for MTC degradation, which ranged between 56% and 68.7% for photolysis and between 76% and 86.7% in photocatalysis. The H2O2 addition resulted in lower degradation in all cases, leading the authors to conclude that the presence of peroxide actually hinders degradation in solar photolysis and photocatalysis processes. Statistical analysis showed that the constant rate reactions calculated for every process, under the same conditions of pH and H2O2 addition, are significantly different from one another, and the three factors considered for experimental design (process, pH, and H2O2) have a statistically significant effect on MTC degradation. The collector area per order confirmed higher efficiency for photocatalysis when compared to photolysis processes.

The anatomical basis for preserving the blood supply to the parathyroids during thyroid surgery, and a review of current technologic advances

BACKGROUND

Devascularization of the parathyroid glands is generally accepted as the most common mechanism for iatrogenic hypocalcemia, a frequently seen complication of both total and completion thyroidectomy procedures. Much has been written about iatrogenic hypoparathyroidism, but few papers have precisely delineated the arterial supply of the parathyroid glands and the common anatomical variations that may impact parathyroid preservation during thyroid surgery.

METHODS

We offer an illustrated review and discussion of the only two anatomic studies published in the medical literature focusing on parathyroid vasculature. In addition, we examine current techniques of parathyroid identification, preservation, and classification.

FINDINGS

A surgical technique that preserves the parathyroid arteries is vital to preserving the viability of the parathyroid gland(s) during thyroid surgery. In 1907, Halsted and Evans described a technique of ligating the distal branches of the thyroid arteries beyond the origin of the parathyroid arteries, a technique termed ultra-ligation. In 1982, Flament et al.. reported three distinct anatomical variations of the parathyroid arteries which place the parathyroid blood supply at risk for devascularization during thyroid surgery. Our review also highlights novel techniques that aid surgeons in identification and assessment of the parathyroid glands.

CONCLUSIONS

Recognition of the variations of parathyroid anatomy and their potential to lead to devascularization aids thyroid surgeons in their pursuit of parathyroid preservation. An awareness of the variety of novel parathyroid identification and preservation techniques can assist surgeons to achieve this goal.

Receptor-Targeted Fluorescence-Guided Surgery With Low Molecular Weight Agents

Cancer surgery remains the primary treatment option for most solid tumors and can be curative if all malignant cells are removed. Surgeons have historically relied on visual and tactile cues to maximize tumor resection, but clinical data suggest that relapse occurs partially due to incomplete cancer removal. As a result, the introduction of technologies that enhance the ability to visualize tumors in the operating room represents a pressing need. Such technologies have the potential to revolutionize the surgical standard-of-care by enabling real-time detection of surgical margins, subclinical residual disease, lymph node metastases and synchronous/metachronous tumors. Fluorescence-guided surgery (FGS) in the near-infrared (NIRF) spectrum has shown tremendous promise as an intraoperative imaging modality. An increasing number of clinical studies have demonstrated that tumor-selective FGS agents can improve the predictive value of fluorescence over non-targeted dyes. Whereas NIRF-labeled macromolecules (i.e., antibodies) spearheaded the widespread clinical translation of tumor-selective FGS drugs, peptides and small-molecules are emerging as valuable alternatives. Here, we first review the state-of-the-art of promising low molecular weight agents that are in clinical development for FGS; we then discuss the significance, application and constraints of emerging tumor-selective FGS technologies.

Review of successful pathways for regulatory approvals in open-field fluorescence-guided surgery

SIGNIFICANCE

The modern use of fluorescence in surgery came iteratively through new devices and pre-existing imaging agents, with indications that were paved via regulatory approvals and device clearances. These events led to a growing set of surgery subspecialty uses.

AIM

This article outlines the key milestones that initiated commercially marketed systems and agents by highlighting temporal sequences and strategic decisions between them, with the goal of helping to inform future successes.

APPROACH

A review of successful regulatory approvals and the sequences between them was completed for companies that achieved US Food and Drug Administration (FDA) premarket approval or new drug approvals (NDAs) or device clearances in the fields of fluorescent imaging agents, open surgery imaging devices, and their approved medical indications.

RESULTS

Angiography agents, indocyanine green and fluorescein, were approved for human use as absorbing dyes, and this use in retinal imaging was the precursor to lateral translation into tissue perfusion imaging in the last two decades with a growing number of devices. Many FDA cleared devices for open fluorescence-guided surgery used the predicate created by the SPY SP2000 system. This first system was 510(k) cleared for angiography imaging with a unique split predicate from x-ray imaging of vasculature and retinal fluorescence angiography. Since that time, the lateral spread of open surgery devices being cleared for new indications has been occurring with a growth of adoption in surgical subspecialties. Growth into new surgical subspecialties has been achieved by leveraging different NDAs and clearances between indications, such that medical uses have broadened over time.

CONCLUSIONS

Key decisions made by developers to advance specific device clearances and NDAs have been based upon existing optical fluorescent agents. The historical lessons and regulatory trends in newer indications and contrast agents can help the field evolve via successful investment in new systems and applications.

Methylene Blue-Current Knowledge, Fluorescent Properties, and Its Future Use

Methylene blue is a fluorescent dye discovered in 1876 and has since been used in different scientific fields. Only recently has methylene blue been used for intraoperative fluorescent imaging. Here, the authors review the emerging role of methylene blue, not only as a dye used in clinical practice, but also as a fluorophore in a surgical setting. We discuss the promising potential of methylene blue together with the challenges and limitations among specific surgical techniques. A literature review of PubMed and Medline was conducted based on the historical, current and future usage of methylene blue within the field of medicine. We reviewed not only the current usage of methylene blue, but we also tried to grasp its’ function as a fluorophore in five main domains. These domains include the near-infrared imaging visualization of ureters, parathyroid gland identification, pancreatic tumors imaging, detection of breast cancer tumor margins, as well as breast cancer sentinel node biopsy. Methylene blue is used in countless clinical procedures with a relatively low risk for patients. Usage of its fluorescent properties is still at an early stage and more pre-clinical, as well as clinical research, must be performed to fully understand its potentials and limitations.

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.

Multimodal imaging with integrated auto-fluorescence and optical coherence tomography for identification of neck tissues

We report a multimodal optical system by combining OCT with autofluorescence imaging for identifying neck tissues, which can use the advantages of large field of view and high sensitivity for identifying parathyroid glands of fluorescence imaging, and high-resolution structural imaging of OCT to confirm them and identify lymph nodes and metastatic lymph nodes at the same time. It is proven that this multimodal optical system can be used to identify different neck tissues effectively and efficiently. We think that integrated auto-fluorescence and OCT imaging have the great potential in the application of navigation and assistant diagnosis of thyroid surgery.

Methylene Blue-Based Near-Infrared Fluorescence Imaging for Breast Cancer Visualization in Resected Human Tissues

Breast-conserving surgery is facing the challenge of objective tumor margin identification intraoperatively. Near-infrared fluorescence imaging would be an ideal approach to visualize tumor margins during surgeries. In this preliminary study, the feasibility of methylene blue-based near-infrared fluorescence imaging technique for breast cancer detection was assessed in resected human breast specimens after breast cancer surgeries. Thirty patients with breast cancer scheduled for surgical treatment were enrolled, including 10 patients with preoperative chemotherapy and 20 patients without. Each of them received an injection of 1 mg/kg methylene blue intravenously 3 hours before the surgery. Then, a home-developed methylene blue-specific near-infrared fluorescence imaging system was employed to image the resected breast tissues and identify the tumor by the fluorescence contrast. Specimens were taken for pathological examinations as the reference. There were no severe adverse events attributable to methylene blue. Of 20 patients, who did not receive preoperative chemotherapy, 16 exhibited fluorescent contrast on their resected tissues (signal-to-background ratio: 1.94 ± 0.71). In contrast, tumors were identified in 3 of 10 specimens from patients who underwent preoperative chemotherapy (signal-to-background ratio: 1.63 ± 0.38). A total of 35 tissues were sampled from 30 specimens. Besides 30 tumor samples, 5 more suspicious samples with fluorescence signal were confirmed to be benign hemorrhagic tissues. Therefore, a sensitivity of 0.63 and a positive predictive value of 0.79 were achieved by the methylene blue fluorescence imaging strategy. Here, we demonstrate the feasibility of using methylene blue fluorescence imaging to identify breast cancer. Preoperative chemotherapy had an impact on imaging effect, which may reduce the detection rate. After all, methylene blue fluorescence imaging has great potential to be used into breast-conserving surgery for tumor-positive margins detection, but further clinical trial study is needed ( http://www.chictr.org.cn/ Clinical Trial Registry ID: ChiCTR1800015400, Near-infrared fluorescence imaging applied in breast cancer identification with methylene blue).

Intraoperative Autofluorescence and Indocyanine Green Angiography for the Detection and Preservation of Parathyroid Glands

Fluorescence imaging is a well-known method for both the in vivo and in vitro identification of specific cells or tissues. This imaging tool is gaining importance in the intraoperative detection and preservation of parathyroid glands during endocrine surgery owing to the intrinsic properties of parathyroid tissue. The aim of this paper is to provide an overview of the basics of the technology, its history, and the recent surgical intraoperative applications of near-infrared imaging methods. Moreover, a literature review of the utilization of fluorescence devices in thyroid surgery suggests that the use of near-infrared imaging seems to be beneficial in reducing postoperative hypoparathyroidism, which is one of the most frequent complications of thyroid surgery.

Mesoporous Silica Containers and Programmed Catalytic Hairpin Assembly/Hybridization Chain Reaction Based Electrochemical Sensing Platform for MicroRNA Ultrasensitive Detection with Low Background

In this work, based on mesoporous silica containers (MSNs) with the programmed enzyme-free DNA assembly amplification of catalytic hairpin assembly (CHA) and hybridization chain reaction (HCR), an ultrasensitive electrochemical sensing platform with low background is developed for the detection of microRNA (miRNA). Herein, the electrochemical reporter methylene blue (MB) was sealed in the pores of MSNs by the double-stranded DNA (dsDNA) gate of hairpin DNA H1 and anchor DNA. In the absence of target, neither the CHA nor the HCR process happened, which enabled a low background. After target was added, DNA H1 was displaced from the MSNs surface and participated in the CHA process with the assistance of hairpin DNA H2, which accelerated the release of MB from the MSNs pore. Meanwhile, the CHA products H1-H2 were hybridized with the capture probes (SH-CP) on the electrode surface, which further initiated the HCR process. The released MB from the MSNs will effectively intercalate into long dsDNA polymers of HCR products, resulting in a significant electrochemical response. Taking miRNA-21 as the model target, the proposed sensing platform achieves a satisfactory detection limit down to 0.037 fM, which is lower than that of electrochemical assay with amplification methods. In addition, the strategy shows good selectivity against other miRNAs and is capable in practical analytes. Benefitting from the features of being label-free and enzyme-free and having low background, high sensitivity, and selectivity, this strategy shows great potential in bioanalysis and clinical diagnostics.

Fluorescence Guidance in Surgical Oncology: Challenges, Opportunities, and Translation

Surgical resection continues to function as the primary treatment option for most solid tumors. However, the detection of cancerous tissue remains predominantly subjective and reliant on the expertise of the surgeon. Surgery that is guided by fluorescence imaging has shown clinical relevance as a new approach to detecting the primary tumor, tumor margins, and metastatic lymph nodes. It is a technique to reduce recurrence and increase the possibility of a curative resection. While significant progress has been made in developing this emerging technology as a tool to assist the surgeon, further improvements are still necessary. Refining imaging agents and tumor targeting strategies to be a precise and reliable surgical strategy is essential in order to translate this technology into patient care settings. This review seeks to provide a comprehensive update on the most recent progress of fluorescence-guided surgery and its translation into the clinic. By highlighting the current status and recent developments of fluorescence image-guided surgery in the field of surgical oncology, we aim to offer insight into the challenges and opportunities that require further investigation.

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.

Near-infrared irradiation of the thyroid area: effects on weight development and thyroid and parathyroid secretory patterns

This study evaluates possible changes in weight and the secretory patterns of the thyroid and parathyroid glands irradiated with a 780-nm light-emitting diode (LED) source under conditions allowing their identification in an animal model. The use of near-infrared light sources to detect the parathyroid glands has been a subject of research due to the benefit provided to patients undergoing thyroid and parathyroid surgery. However, few studies have explored possible changes in weight and the secretory patterns of the glands when subjected to light stimulation. Thirty-two male Wistar rats were divided into two groups and subjected to cervical dissection and irradiation of the thyroid-parathyroid region under general anesthesia. The animals in group 1 (irradiated) were exposed to a 780-nm LED light beam for 180 s (dose 1.37 J/cm²), whereas the animals in group 2 (control) were not irradiated. Blood samples were collected pre-exposure, 7 min after exposure, and 30 and 60 days after exposure to measure calcium, parathyroid hormone (PTH), triiodothyronine (T₃), thyroxine (T₄), and thyroid-stimulating hormone (TSH) levels in both groups. Weight variations between the evaluation periods were also analyzed. Parametric statistics were used (Student's t test and ANOVA) after assuming normal distribution of continuous variables with the Shapiro-Wilk test. No significant variation was observed in any of the analyzed parameters pre- and postexposure. A significant increase in the calcium level was observed at 30 days in the irradiated group compared with that in the control group (11.156 ± 1.31 mg/dl vs 10.300 ± 0.30 mg/dl; df = 30 p < 0.03) but this change was no longer observed at 60 days (9.925 ± 0.23 mg/dl vs 10.014 ± 0.18 mg/dl; df = 14 p = 0.21). Irradiated rats gained less weight in the first 30 days after surgery (39.647 ± 32.39 vs 55.917 ± 22.61; df = 30 p = 0.146) and at 60 days (84.000 ± 27.36 vs 84.571 ± 5.62; df = 14 p = 0.957), no differences were observed between the two groups. No significant variations in weight development or changes in the secretory patterns of the thyroid and parathyroid glands exposed to near-infrared stimulation were observed, confirming the safety of this light source in the identification of the parathyroid glands.

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.

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.

The development of fluorescence guided surgery for pancreatic cancer: from bench to clinic

INTRODUCTION

Surgeons face major challenges in achieving curative R0 resection for pancreatic cancers. When the lesion is localized, they must appropriately visualize the tumor, determine appropriate resection margins, and ensure complete tumor clearance. Real-time surgical navigation using fluorescence-guidance has enhanced the ability of surgeons to see the tumor and has the potential to assist in achieving more oncologically complete resections. When there is metastatic disease, fluorescence enhancement can help detect these lesions and prevent unnecessary and futile surgeries. Areas covered: This article reviews different approaches for delivery of a fluorescence signal, their pre-clinical and clinical developments for fluorescence guided surgery, the advantages/challenges of each, and their potential for advancements in the future. Expert commentary: A variety of molecular imaging techniques are available for delivering tumor-specific fluorescence signals. Significant advancements have been made in the past 10 years due to the large body of literature on targeted therapies and this has translated into rapid developments of tumor-specific probes.

Label-free hyperspectral imaging and quantification methods for surgical margin assessment of tissue specimens of cancer patients

Hyperspectral imaging (HSI) is a relatively new modality in medicine and can have many potential applications. In this study, we developed label-free hyperspectral imaging for tumor margin assessment. HSI data, hypercube (x,y,λ), consists of a series of images of the same field of view that are acquired at different wavelengths. Every pixel in the hypercube has an optical spectrum. We collected surgical tissue specimens from 16 human subjects who underwent head and neck (H&N) cancer surgery. We acquired both HSI, autofluorescence images, and fluorescence images with 2-NBDG and proflavine from the specimens. Digitized histologic slides were examined by an H&N pathologist. We developed image preprocessing and classification methods for HSI data and differentiate cancer from benign tissue. The hyperspectral imaging and classification method was able to distinguish between cancer and normal tissue from oral cavity with an average accuracy of 90±8%, sensitivity of 89±9%, and specificity of 91±6%. This study suggests that label-free hyperspectral imaging has great potential for surgical margin assessment in tissue specimens of H&N cancer patients. Further development of the imaging technology and quantification methods is warranted for its application in image-guided surgery.

Photodynamic Therapy

Photodynamic therapy is a clinical technique for the treatment of cancers, microbial infections and other medical conditions by means of light-induced generation of reactive oxygen species using photosensitising drugs. The intrinsic fluorescence of many such drugs make them potential theranostic agents for simultaneous diagnosis and therapy. This chapter reviews the basic chemical and biological aspects of photodynamic therapy with an emphasis on its applications in theranostics. The roles of nanotechnology is highlighted, as well as emerging trends such as photoimmunotherapy, image-guided surgery and light- and singlet-oxygen dosimetry.

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.

Intraoperative Near-Infrared Fluorescence Imaging of Multiple Pancreatic Neuroendocrine Tumors: A Case Report

Multiple endocrine neoplasia type 1 syndrome can feature pancreatic neuroendocrine lesions that have the potential to degenerate into malignancies (pancreatic neuroendocrine tumors [PNETs]). Resection is required in selected cases and aims to cure patients and to prevent metastasis. Preoperative imaging is important to assess the number, size, and location of PNETs. However, sensitivity of preoperative imaging modalities to detect small lesions can be rather disappointing. This makes intraoperative reassessment of the pancreas crucial. Methylene blue (MB) accumulates in neuroendocrine lesions after intravenous administration. Methylene blue emits fluorescence of approximately 700 nm and can be visualized using a dedicated near-infrared (NIR) fluorescence imaging system. We present a 58-year-old male patient with multiple endocrine neoplasia type 1 syndrome and 2 lesions suspected as PNETs identified during regular follow-up. Intraoperative administration of MB allowed successful NIR fluorescence imaging of multiple lesions missed by preoperative imaging. After confirmation by intraoperative ultrasound, this new finding led to a major change in treatment: from enucleations to total pancreatectomy. Histopathologic examination confirmed that the fluorescent lesions were indeed neuroendocrine lesions ranging from microadenomas to PNETs. This case demonstrates that intraoperative assessment of neuroendocrine lesions can be improved by intraoperative NIR fluorescence imaging using MB, a safe and relatively easy technique.

Fluorescence-Guided Surgery

Surgical resection of cancer remains an important treatment modality. Despite advances in preoperative imaging, surgery itself is primarily guided by the surgeon’s ability to locate pathology with conventional white light imaging. Fluorescence-guided surgery (FGS) can be used to define tumor location and margins during the procedure. Intraoperative visualization of tumors may not only allow more complete resections but also improve safety by avoiding unnecessary damage to normal tissue which can also reduce operative time and decrease the need for second-look surgeries. A number of new FGS imaging probes have recently been developed, complementing a small but useful number of existing probes. In this review, we describe current and new fluorescent probes that may assist FGS.

Use of methylene blue and near-infrared fluorescence in thyroid and parathyroid surgery

Purpose

Intraoperative localisation and preservation of parathyroid glands improves outcomes following thyroid and parathyroid surgery. This can be facilitated by fluorescent imaging and methylene blue; a fluorophore is thought to be taken up avidly by parathyroid glands. This preliminary study aims to identify the optimum dose of methylene blue (MB), fluorescent patterns of thyroid and parathyroid glands and develop a protocol for the use of intravenous MB emitted fluorescence to enable parathyroid identification.

Methods

This is a phase 1b, interventional study (NCT02089542) involving 41 patients undergoing thyroid and/or parathyroid surgery. After exposure of the thyroid and/or parathyroid gland(s), intravenous boluses of between 0.05 and 0.5 mg/kg of MB were injected. Fluobeam® (a hand held fluorescence real-time imager) was used to record fluorescence from the operating field prior and up to 10 min following administration.

Results

The optimum dose of MB to visualise thyroid and parathyroid glands was 0.4 mg/kg body weight. The median time to onset of fluorescence was 23 and 22 s and the median time to peak fluorescence was 41.5 and 40 s, respectively. The peak fluorescence for thyroid and parathyroid glands compared to muscle were 2.6 and 4.3, respectively. Parathyroid auto-fluorescence prior to methylene blue injection was commonly observed.

Conclusions

A clinical protocol for detection of fluorescence from MB during thyroid and parathyroid surgery is presented. Parathyroids (especially enlarged glands) fluoresce more intensely than thyroid glands. Auto-fluorescence may aid parathyroid detection, but MB fluorescence is needed to demonstrate viability.

Optical molecular imaging for tumor detection and image-guided surgery

We have witnessed rapid development of fluorescence molecular imaging of solid tumors for cancer diagnosis and image-guided surgery in the past decade. Many biomarkers unique to cancer cells or tumor microenvironment, such as cell surface receptors, hypoxia, secreted proteases and extracellular acidosis have been characterized, and can be used to distinguish cancer from normal tissue. A variety of optical imaging probes have been developed to target these biomarkers to improve tumor contrast over the background tissue. Unlike conventional anatomical and molecular imaging technologies, fluorescent imaging method benefits from its safety, high-spatial resolution and real-time capability, and therefore, has become a highly adoptable imaging method for tumor detection and image-guided surgery in clinics. In this review, we summarize recent progress in 'always-ON' and stimuli-activatable fluorescent imaging probes, and discuss their potentials in tumor detection and image-guided surgery.

Intraoperative Parathyroid Localization with Near-Infrared Fluorescence Imaging Using Indocyanine Green during Total Parathyroidectomy for Secondary Hyperparathyroidism

The detection of all glands during total parathyroidectomy (TPTX) in secondary hyperparathyroidism (SHPT) patients is often difficult due to their variability in number and location. The objective of this study was to evaluate the feasibility of near-infrared fluorescence (NIRF) imaging using indocyanine green (ICG) for intraoperative parathyroid gland (PTG) localization in SHPT patients. Twenty-nine patients with SHPT were divided into two groups with or without intraoperative NIRF imaging. ICG was administered in patients undergoing intraoperative imaging, and the fluorescence of PTGs was assessed. Clinical and histopathologic variables were analyzed to determine factors associated with ICG uptake. Comparisons between NIRF and preoperative imaging, as well as differences between groups with or without NIRF imaging, were carried out to evaluate the efficacy of this technique. Most PTGs could be clearly identified, including one ectopic gland. The sensitivity of NIRF imaging is 91.1% in contrast to 81.82% for ultrasonography (US), 62.34% for ^99mTc-MIBI and 85.71% for computed tomography (CT). In addition, intraoperative NIRF imaging can reduce the operation time and improve the complete resection rate compared with the group not using it. Intraoperative NIRF imaging using ICG during TPTX is technically feasible and reliable for assisting surgeons in detecting and confirming PTGs.

Beyond the margins: real-time detection of cancer using targeted fluorophores

Over the past two decades, synergistic innovations in imaging technology have resulted in a revolution in which a range of biomedical applications are now benefiting from fluorescence imaging. Specifically, advances in fluorophore chemistry and imaging hardware, and the identification of targetable biomarkers have now positioned intraoperative fluorescence as a highly specific real-time detection modality for surgeons in oncology. In particular, the deeper tissue penetration and limited autofluorescence of near-infrared (NIR) fluorescence imaging improves the translational potential of this modality over visible-light fluorescence imaging. Rapid developments in fluorophores with improved characteristics, detection instrumentation, and targeting strategies led to the clinical testing in the early 2010s of the first targeted NIR fluorophores for intraoperative cancer detection. The foundations for the advances that underline this technology continue to be nurtured by the multidisciplinary collaboration of chemists, biologists, engineers, and clinicians. In this Review, we highlight the latest developments in NIR fluorophores, cancer-targeting strategies, and detection instrumentation for intraoperative cancer detection, and consider the unique challenges associated with their effective application in clinical settings.

Combination of Fluorescence-Guided Surgery With Photodynamic Therapy for the Treatment of Cancer

Specific visualization of body parts is needed during surgery. Fluorescence-guided surgery (FGS) uses a fluorescence contrast agent for in vivo tumor imaging to detect and identify both malignant and normal tissues. There are several advantages and clinical benefits of FGS over other conventional medical imaging modalities, such as its safety, effectiveness, and suitability for real-time imaging in the operating room. Recent advancements in contrast agents and intraoperative fluorescence imaging devices have led to a greater potential for intraoperative fluorescence imaging in clinical applications. Photodynamic therapy (PDT) is an alternative modality to treat tumors, which uses a light-sensitive drug (photosensitizers) and special light to destroy the targeted tissues. In this review, we discuss the fluorescent contrast agents, some newly developed imaging devices, and the successful clinical application of FGS. Additionally, we present the combined strategy of FGS with PDT to further improve the therapeutic effect for patients with cancer. Taken together, this review provides a unique perspective and summarization of FGS.

Tumor margin assessment of surgical tissue specimen of cancer patients using label-free hyperspectral imaging

We are developing label-free hyperspectral imaging (HSI) for tumor margin assessment. HSI data, hypercube (x,y,λ), consists of a series of high-resolution images of the same field of view that are acquired at different wavelengths. Every pixel on the HSI image has an optical spectrum. We developed preprocessing and classification methods for HSI data. We used spectral features from HSI data for the classification of cancer and benign tissue. We collected surgical tissue specimens from 16 human patients who underwent head and neck (H&N) cancer surgery. We acquired both HSI, autofluorescence images, and fluorescence images with 2-NBDG and proflavine from the specimens. Digitized histologic slides were examined by an H&N pathologist. The hyperspectral imaging and classification method was able to distinguish between cancer and normal tissue from oral cavity with an average accuracy of 90±8%, sensitivity of 89±9%, and specificity of 91±6%. For tissue specimens from the thyroid, the method achieved an average accuracy of 94±6%, sensitivity of 94±6%, and specificity of 95±6%. Hyperspectral imaging outperformed autofluorescence imaging or fluorescence imaging with vital dye (2-NBDG or proflavine). This study suggests that label-free hyperspectral imaging has great potential for tumor margin assessment in surgical tissue specimens of H&N cancer patients. Further development of the hyperspectral imaging technology is warranted for its application in image-guided surgery.

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.

Intraoperative Identification of a Normal Pituitary Gland and an Adenoma Using Near-Infrared Fluorescence Imaging and Low-Dose Indocyanine Green

BACKGROUND

The intraoperative distinction between normal and abnormal pituitary tissue is crucial during pituitary adenoma surgery to obtain a complete tumor resection while preserving endocrine function. Near-infrared (NIR) fluorescence imaging is a technique to intraoperatively visualize tumors by using indocyanine green (ICG), a contrast agent allowing visualization of differences in tissue vascularization. Although NIR fluorescence imaging has been described in pituitary surgery, it has, in contrast to other surgical areas, never become widely used.

OBJECTIVE

To evaluate NIR fluorescence imaging in pituitary surgery, both qualitatively and quantitatively, and to assess the additional value of resecting adenoma tissue under NIR fluorescence guidance.

METHODS

We included 10 patients planned to undergo transnasal transsphenoidal selective adenomectomy. Patients received multiple intravenous administrations of 5 mg ICG, up to a maximum of 15 mg per patient. Endoscopic NIR fluorescence imaging was performed at multiple points in time. The NIR fluorescent signal in both the adenoma and pituitary gland was obtained, and the fluorescence contrast ratio was assessed.

RESULTS

Four patients had Cushing disease, 1 had acromegaly, and 1 had a prolactinoma. Four patients had a nonfunctioning macroadenoma. In 9 of 10 patients with a histologically proven pituitary adenoma, the normal pituitary gland showed a stronger fluorescent signal than the adenoma. A fluorescence contrast ratio of normal pituitary gland to adenoma of 1.5 ± 0.2 was obtained. In 2 patients; adenoma resection was actually performed under NIR fluorescence guidance instead of under white light.

CONCLUSION

NIR fluorescence imaging can easily and safely be implemented in pituitary surgery. The timing of ICG administration is important for optimal results and warrants further study. It appears that injection of ICG can best be postponed until some part of the normal pituitary gland is identified. Subsequent repeated low-dose ICG administrations improved the distinction between adenoma and gland.

Towards automated spectroscopic tissue classification in thyroid and parathyroid surgery

BACKGROUND

In (para-)thyroid surgery iatrogenic parathyroid injury should be prevented. To aid the surgeons' eye, a camera system enabling parathyroid-specific image enhancement would be useful. Hyperspectral camera technology might work, provided that the spectral signature of parathyroid tissue offers enough specific features to be reliably and automatically distinguished from surrounding tissues. As a first step to investigate this, we examined the feasibility of wide band diffuse reflectance spectroscopy (DRS) for automated spectroscopic tissue classification, using silicon (Si) and indium-gallium-arsenide (InGaAs) sensors.

METHODS

DRS (350-1830 nm) was performed during (para-)thyroid resections. From the acquired spectra 36 features at predefined wavelengths were extracted. The best features for classification of parathyroid from adipose or thyroid were assessed by binary logistic regression for Si- and InGaAs-sensor ranges. Classification performance was evaluated by leave-one-out cross-validation.

RESULTS

In 19 patients 299 spectra were recorded (62 tissue sites: thyroid = 23, parathyroid = 21, adipose = 18). Classification accuracy of parathyroid-adipose was, respectively, 79% (Si), 82% (InGaAs) and 97% (Si/InGaAs combined). Parathyroid-thyroid classification accuracies were 80% (Si), 75% (InGaAs), 82% (Si/InGaAs combined).

CONCLUSIONS

Si and InGaAs sensors are fairly accurate for automated spectroscopic classification of parathyroid, adipose and thyroid tissues. Combination of both sensor technologies improves accuracy. Follow-up research, aimed towards hyperspectral imaging seems justified. Copyright © 2016 John Wiley & Sons, Ltd.

Luminescence-based Imaging Approaches in the Field of Interventional Molecular Imaging

Luminescence imaging-based guidance technologies are increasingly gaining interest within surgical and radiologic disciplines. Their promise to help visualize molecular features of disease in real time and with microscopic detail is considered desirable. Integrating luminescence imaging with three-dimensional radiologic- and/or nuclear medicine-based preinterventional imaging may overcome limitations such as the limited tissue penetration of luminescence signals. At the same time, the beneficial features of luminescence imaging may be used to complement the routinely used radiologic- and nuclear medicine-based modalities. To fully exploit this integrated concept, and to relate the largely experimental luminesce-based guidance approaches into perspective with routine imaging approaches, it is essential to understand the advantages and limitations of this relatively new modality. By providing an overview of the available luminescence technologies and the various clinically evaluated exogenous luminescent tracers (fluorescent, hybrid, and theranostic tracers), this review attempts to place luminescence-based interventional molecular imaging technologies into perspective to the available radiologic- and/or nuclear medicine-based imaging technologies. At the same time, the transition from anatomic to physiologic and even molecular interventional luminescence imaging is illustrated.

The Value of Intraoperative Near-Infrared Fluorescence Imaging Based on Enhanced Permeability and Retention of Indocyanine Green: Feasibility and False-Positives in Ovarian Cancer

Objective

In ovarian cancer, two of the most important prognostic factors for survival are completeness of staging and completeness of cytoreductive surgery. Therefore, intra-operative visualization of tumor lesions is of great importance. Preclinical data already demonstrated tumor visualization in a mouse-model using near-infrared (NIR) fluorescence imaging and indocyanine green (ICG) as a result of enhanced permeability and retention (EPR). The aim of this study was to determine feasibility of intraoperative ovarian cancer metastases imaging using NIR fluorescence imaging and ICG in a clinical setting.

Methods

Ten patients suspected of ovarian cancer scheduled for staging or cytoreductive surgery were included. Patients received 20 mg ICG intravenously after opening the abdominal cavity. The mini-FLARE NIR fluorescence imaging system was used to detect NIR fluorescent lesions.

Results

6 out of 10 patients had malignant disease of the ovary or fallopian tube, of which 2 had metastatic disease outside the pelvis. Eight metastatic lesions were detected in these 2 patients, which were all NIR fluorescent. However, 13 non-malignant lesions were also NIR fluorescent, resulting in a false-positive rate of 62%. There was no significant difference in tumor-to-background ratio between malignant and benign lesions (2.0 vs 2.0; P=0.99).

Conclusions

This is the first clinical trial demonstrating intraoperative detection of ovarian cancer metastases using NIR fluorescence imaging and ICG. Despite detection of all malignant lesions, a high false-positive rate was observed. Therefore, NIR fluorescence imaging using ICG based on the EPR effect is not satisfactory for the detection of ovarian cancer metastases. The need for tumor-specific intraoperative agents remains.

Trial Registration

ISRCTN Registry ISRCTN16945066

Intraoperative guidance in parathyroid surgery using near-infrared fluorescence imaging and low-dose Methylene Blue

BACKGROUND

Identification of diseased and normal parathyroid glands during parathyroid surgery can be challenging. The aim of this study was to assess whether near-infrared (NIR) fluorescence imaging using administration of a low-dose Methylene Blue (MB) at the start of the operation could provide optical guidance during parathyroid surgery and assist in the detection of parathyroid adenomas.

METHODS

Patients diagnosed with primary hyperparathyroidism planned for parathyroidectomy were included. Patients received 0.5 mg/kg MB intravenously directly after start of anesthesia. During the operation, NIR fluorescence imaging was performed to identify parathyroid adenomas. Imaging results were compared with a previous published feasibility study in which 12 patients received MB after intraoperative identification of the adenoma.

RESULTS

A total of 13 patients were included in the current study. In 10 of 12 patients with a histologically proven adenoma, the adenoma was fluorescent. Mean signal to background ratio was 3.1 ± 2.8. Mean diameter of the resected lesions was 17 ± 9 mm (range 5-28 mm). Adenomas could be identified up to 145 minutes after administration, which was the longest timespan until resection. Interestingly, in 3 patients, a total of 6 normal parathyroid glands (median diameter 2.5 mm) with a signal to background ratio of 1.8 ± 0.4 were identified using NIR fluorescence imaging.

CONCLUSION

Early administration of low-dose MB provided guidance during parathyroidectomy by identifying both parathyroid adenomas and normal parathyroid glands. In patients in whom difficult identification of the parathyroid adenoma is expected or when normal glands have to be identified, the administration of MB may improve surgical outcome.

NIR fluorescent small molecules for intraoperative imaging

Recent advances in bioimaging and nanomedicine have permitted the exploitation of molecular optical imaging in image-guided surgery; however, the parameters mediating optimum performance of contrast agents are not yet precisely determined. To develop ideal contrast agents for image-guided surgery, we need to consider the following criteria: (1) excitation and emission wavelengths in the near-infrared (NIR) window, (2) optimized optical characteristics for high in vivo performance, (3) overcoming or harnessing biodistribution and clearance, and (4) reducing nonspecific uptake. The design considerations should be focused on optimizing the optical and physicochemical property criteria. Biodistribution and clearance should first be considered because they mediate the fate of a contrast agent in the body such as how long after intravenous injection a contrast agent reaches the peak signal-to-background ratio (SBR) and how long the signal lasts (retention).

Structure-inherent targeting of near-infrared fluorophores for parathyroid and thyroid gland imaging

The typical method for creating targeted contrast agents requires covalent conjugation of separate targeting and fluorophore domains. In this study, we demonstrate that it is possible to create near-infrared (NIR) fluorophores with different tissue specificities driven by their inherent chemical structures. Thus, a single compact molecule performs both targeting and imaging. We use this strategy to solve a major problem in head and neck surgery: the identification and preservation of parathyroid and thyroid glands. We synthesized 700-nm and 800-nm halogenated fluorophores that show high uptake into these glands after a single intravenous (IV) injection of 0.06 mg kg(-1) in a pig. By using a dual-channel NIR imaging system, we observed-in real time and with high sensitivity-the unambiguous distinction of parathyroid and thyroid glands simultaneously in the context of blood and surrounding soft tissue. This novel technology lays a foundation for performing head and neck surgery with increased precision and efficiency along with potentially lower morbidity, and it provides a general strategy for developing targeted NIR fluorophores.

Intraoperative near-infrared fluorescence imaging of a paraganglioma using methylene blue: A case report

•

A 19-year-old patient diagnosed with a rare neuroendocrine tumor is presented.

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Innovative intraoperative imaging of the tumor was performed.

•

NIR fluorescence imaging identified an otherwise undetectable lesion during surgery.

•

This technique could result in more complete resections in paraganglioma surgery.

Introduction

Intraoperative identification of tumors can be challenging. Near-infrared (NIR) fluorescence imaging is an innovative technique that can assist in intraoperative identification of tumors, which may otherwise be undetectable.

Presentation of case

A 19-year-old patient with symptoms, normetanephrine levels and radiological findings suspicious for a paraganglioma, a rare tumor arising from extra-adrenal chromaffin cells within the sympathetic nervous system, is presented. Intraoperative NIR fluorescence imaging using intravenous administration of methylene blue (MB) assisted in intraoperative detection of the tumor, and even identified a smaller second lesion, which was not identified during surgery by visual inspection.

Discussion

Although the exact mechanism of MB accumulation in neuroendocrine tumors is unclear, it is described in both preclinical and clinical studies.

Conclusion

In this report, we describe the first case of intraoperative NIR fluorescence imaging of a paraganglioma using MB, which identified an otherwise undetectable lesion.

Near infrared fluorescence imaging of rabbit thyroid and parathyroid glands

BACKGROUND

Near infrared fluorescence imaging using intravenous methylene blue (MB) is a novel technique that has potential to aid the parathyroid gland (PG) localization during thyroid and parathyroid surgery. The aim of this study was to examine MB fluorescence in the rabbit neck and determine the influence of MB dose and time following administration on fluorescence from thyroid and PGs.

METHODS

Thyroid and external PGs were exposed in six New Zealand white rabbits under anesthesia. Varying doses of MB (0.025-3 mg/kg) were injected through the marginal ear vein. Near infrared fluorescence from exposed tissues was recorded at different time intervals (10-74 min) using Fluobeam 700. Specimens of identified glands were then resected for histologic assessment.

RESULTS

Histology confirmed accurate identification of all excised thyroid and PGs; these were the only neck structures to demonstrate significant fluorescence. The parathyroid demonstrated lower fluorescence intensities and reduced washout times at all MB doses compared with the thyroid gland. A dose of 0.1 mg/kg MB was adequate to identify fluorescence; this also delineated the blood supply of the external PGs.

CONCLUSIONS

The study demonstrates that near infrared fluorescence with intravenous MB helps differentiate between thyroid and PGs in the rabbit. This has potential to improve outcomes in thyroid and parathyroid surgery by increasing the accuracy of parathyroid identification; however, the findings require replication in human surgery. The use of low doses of MB may also avoid the side effects associated with currently used doses in humans (3-7 mg/kg).

Fluorescent-tilmanocept for tumor margin analysis in the mouse model

BACKGROUND

Dendritic cells (DC) are localized in close proximity to cancer cells in many well-known tumors, and thus maybe a useful target for tumor margin assessment.

MATERIALS AND METHODS

[(99m)Tc]- cyanine 7 (Cy7)-tilmanocept was synthesized and in vitro binding assays to bone marrow-derived DC were performed. Fifteen mice, implanted with either 4T1 mouse mammary or K1735 mouse melanoma tumors, were administered 1.0 nmol of [(99m)Tc]-Cy7-tilmanocept via tail vein injection. After fluorescence imaging 1 or 2 h after injection, the tumor, muscle, and blood were assayed for radioactivity to calculate percent-injected dose. Digital images of the tumors after immunohistochemical staining for DC were analyzed to determine DC density.

RESULTS

In vitro binding demonstrated subnanomolar affinity of [(99m)Tc]-Cy7-tilmanocept to DC (KA = 0.31 ± 0.11 nM). After administration of [(99m)Tc]-Cy7-tilmanocept, fluorescence imaging showed a 5.5-fold increase in tumor signal as compared with preinjection images and a 3.3-fold difference in fluorescence activity when comparing the tumor with the surgical bed after tumor excision. Immunohistochemical staining analysis demonstrated that DC density positively correlated with tumor percent of injected dose per gram (r = 0.672, P = 0.03), and higher DC density was observed at the periphery versus center of the tumor (186 ± 54 K versus 64 ± 16 K arbitrary units, P = 0.001).

CONCLUSIONS

[(99m)Tc]-Cy7-tilmanocept exhibits in vitro and in vivo tumor-specific binding to DC and maybe useful as a tumor margin targeting agent.