Real-time intraoperative assessment of the extrahepatic bile ducts in rats and pigs using invisible near-infrared fluorescent light

Fluorescence-Guided Surgery for Hepatoblastoma with Indocyanine Green

Fluorescence-guided surgery with indocyanine green (ICG) for malignant hepatic tumors has been gaining more attention with technical advancements. Since hepatoblastomas (HBs) possess similar features to hepatocellular carcinoma, fluorescence-guided surgery can be used for HBs, as aggressive surgical resection, even for distant metastases of HBs, often contributes positively to R0 (complete) resection and subsequent patient survival. Despite a few caveats, fluorescence-guided surgery allows for the more sensitive identification of lesions that may go undetected by conventional imaging or be invisible macroscopically. This leads to precise resection of distant metastatic tumors as well as primary liver tumors.

A Biliary Tract-Specific Near-Infrared Fluorescent Dye for Image-Guided Hepatobiliary Surgery

Despite advances, visual inspection, palpation, and intraoperative ultrasound remain the most utilized tools during surgery today. A particularly challenging issue is the identification of the biliary system due to its complex architecture partially embedded within the liver. Fluorescence guided surgical interventions, particularly using near-infrared (NIR) wavelengths, are an emerging approach for the real-time assessment of the hepatobiliary system. However, existing fluorophores, such as the FDA-approved indocyanine green (ICG), have significant limitations for rapid and selective visualization of bile duct anatomy. Here we report a novel NIR fluorophore, BL (Bile Label)-760, which is exclusively metabolized by the liver providing high signal in the biliary system shortly after intravenous administration. This molecule was identified by first screening a small set of known heptamethine cyanines including clinically utilized agents. After finding that none of these were well-suited, we then designed and tested a small series of novel dyes within a prescribed polarity range. We validated the molecule that emerged from these efforts, BL-760, through animal studies using both rodent and swine models employing a clinically applicable imaging system. In contrast to ICG, BL-760 fluorescence revealed a high target-to-background ratio (TBR) of the cystic duct relative to liver parenchyma 5 min after intravenous injection. During hepatic resection surgery, intrahepatic ducts were clearly highlighted, and bile leakage was easily detected. In conclusion, BL-760 has highly promising properties for intraoperative navigation during hepatobiliary surgery.

Fluorescent Nanoparticles for the Guided Surgery of Ovarian Peritoneal Carcinomatosis

Complete surgical resection is the ideal cure for ovarian peritoneal carcinomatosis, but remains challenging. Fluorescent guided surgery can be a promising approach for precise cytoreduction when appropriate fluorophore is used. In the presence paper, we review already developed near- and short-wave infrared fluorescent nanoparticles, which are currently under investigation for peritoneal carcinomatosis fluorescence imaging. We also highlight the main ways to improve the safety of nanoparticles, for fulfilling prerequisites of clinical application.

Effects of an Unlabeled Loading Dose on Tumor-Specific Uptake of a Fluorescently Labeled Antibody for Optical Surgical Navigation

PURPOSE

Intraoperative optical imaging to guide surgeons during oncologic resections offers a unique and promising solution to the ambiguity of cancer margins to tactile and visual assessment that results in devastatingly high rates of positive margins. Sequestering of labeled antibodies by normal tissues with high expression of the antibody target, or "antigen sinks", diminishes the efficacy of these probes to provide contrast between the tumor and background tissues by decreasing the amount of circulating probe available for uptake by the tumor and by increasing the fluorescence of non-tumor tissues. We hypothesized that administering a dose of unlabeled antibody prior to infusion of the near-infrared (NIR) fluorescently labeled antibody would improve tumor-specific uptake and contrast of the fluorescently labeled probe by occupying extra-tumoral binding sites, thereby increasing the amount of labeled probe available for uptake by the tumor.

PROCEDURES

In this study, we explore this concept by testing two different "pre-load" doses of unlabeled cetuximab (the standard 10-mg test dose, and a larger, experimental 100-mg test dose) in six patients receiving cetuximab conjugated to the fluorescent dye IRDye800CW (cetuximab-IRDye800CW) in a clinical trial, and compared the amount of fluorescent antibody in tumor and background tissues, as well as the tumor-specific contrast of each.

RESULTS

The patients receiving the larger preload (100 mg) of unlabeled cetuximab demonstrated significantly higher concentrations (9.5 vs. 0.1 μg) and a longer half-life (30.3 vs. 20.6 days) of the labeled cetuximab in plasma, as well as significantly greater tumor fluorescence (32.3 vs. 9.3 relative fluorescence units) and tumor to background ratios (TBRs) (5.5 vs. 1.7).

CONCLUSIONS

Administering a preload of unlabeled antibody prior to infusion of the fluorescently labeled drug may be a simple and effective way to improve the performance of antibody-based probes to guide surgical resection of solid malignancies.

Benchtop and animal validation of a portable fluorescence microscopic imaging system for potential use in cholecystectomy

We propose a portable fluorescence microscopic imaging system (PFMS) for intraoperative display of biliary structure and prevention of iatrogenic injuries during cholecystectomy. The system consists of a light source module, a camera module, and a Raspberry Pi computer with an LCD. Indocyanine green (ICG) is used as a fluorescent contrast agent for experimental validation of the system. Fluorescence intensities of the ICG aqueous solution at different concentration levels are acquired by our PFMS and compared with those of a commercial Xenogen IVIS system. We study the fluorescence detection depth by superposing different thicknesses of chicken breast on an ICG-loaded agar phantom. We verify the technical feasibility for identifying potential iatrogenic injury in cholecystectomy using a rat model in vivo. The proposed PFMS system is portable, inexpensive, and suitable for deployment in resource-limited settings.

Near-infrared fluorescence laparoscopy of the cystic duct and cystic artery: first experience with two new preclinical dyes in a pig model

Background

Imaging techniques that enhance visualisation of the anatomy may help prevent bile duct injury. Near-Infrared Fluorescence Imaging is such a technique. Previous experiments with ICG have shown that illumination of the extra-hepatic bile ducts is feasible. Yet, there is room for improvement in the visualisation of the target as compared to the background. Experiments with IRDye^® 800CW show promising results. However, this dye is too expensive for routine clinical use. The aim of this study is to test the first applicability of two newly developed preclinical dyes regarding intraoperative imaging of the cystic duct and cystic artery, compared with IRDye^® 800CW.

Methods

Laparoscopic cholecystectomy was performed in three pigs, using a laparoscopic fluorescence imaging system. Each pig received 6 mg of one of the fluorescent dyes (1 mg/mL; IRDye^® 800CW, IRDye^® 800BK or IRDye^® 800NOS) by intravenous injection. Intraoperative recognition of the biliary system and cystic artery was registered at set time points. All procedures were digitally recorded, and the target to background ratio (TBR) was determined to assess the fluorescence signal.

Results

With all three fluorescent dyes, the cystic artery was directly visualised. For the visualisation of the cystic duct, 15, 34 and 30 min were needed using IRDye^® 800BK, IRDye^® 800NOS and IRDye^® 800CW, respectively. The maximum TBR of the cystic duct was the highest with IRDye^® 800NOS (4.20) after 36 min, compared to 2.45 for IRDye^® 800BK and 2.15 for IRDye^® 800CW, both after 45 min. There were no adverse events.

Conclusion

IRDye^® 800BK and IRDye^® 800NOS seem to be good alternatives for IRDye^® 800CW for the visualisation of the cystic duct and cystic artery in pigs.

Characterizing the Utility and Limitations of Repurposing an Open-Field Optical Imaging Device for Fluorescence-Guided Surgery in Head and Neck Cancer Patients

The purpose of this study was to assess the potential of U.S. Food and Drug Administration-cleared devices designed for indocyanine green-based perfusion imaging to identify cancer-specific bioconjugates with overlapping excitation and emission wavelengths. Recent clinical trials have demonstrated potential for fluorescence-guided surgery, but the time and cost of the approval process may impede clinical translation. To expedite this translation, we explored the feasibility of repurposing existing optical imaging devices for fluorescence-guided surgery.

METHODS

Consenting patients (n = 15) scheduled for curative resection were enrolled in a clinical trial evaluating the safety and specificity of cetuximab-IRDye800 (NCT01987375). Open-field fluorescence imaging was performed preoperatively and during the surgical resection. Fluorescence intensity was quantified using integrated instrument software, and the tumor-to-background ratio characterized fluorescence contrast.

RESULTS

In the preoperative clinic, the open-field device demonstrated potential to guide preoperative mapping of tumor borders, optimize the day of surgery, and identify occult lesions. Intraoperatively, the device demonstrated robust potential to guide surgical resections, as all peak tumor-to-background ratios were greater than 2 (range, 2.2-14.1). Postresection wound bed fluorescence was significantly less than preresection tumor fluorescence (P < 0.001). The repurposed device also successfully identified positive margins.

CONCLUSION

The open-field imaging device was successfully repurposed to distinguish cancer from normal tissue in the preoperative clinic and throughout surgical resection. This study illuminated the potential for existing open-field optical imaging devices with overlapping excitation and emission spectra to be used for fluorescence-guided surgery.

Benchtop and Animal Validation of a Projective Imaging System for Potential Use in Intraoperative Surgical Guidance

We propose a projective navigation system for fluorescence imaging and image display in a natural mode of visual perception. The system consists of an excitation light source, a monochromatic charge coupled device (CCD) camera, a host computer, a projector, a proximity sensor and a Complementary metal-oxide-semiconductor (CMOS) camera. With perspective transformation and calibration, our surgical navigation system is able to achieve an overall imaging speed higher than 60 frames per second, with a latency of 330 ms, a spatial sensitivity better than 0.5 mm in both vertical and horizontal directions, and a projection bias less than 1 mm. The technical feasibility of image-guided surgery is demonstrated in both agar-agar gel phantoms and an ex vivo chicken breast model embedding Indocyanine Green (ICG). The biological utility of the system is demonstrated in vivo in a classic model of ICG hepatic metabolism. Our benchtop, ex vivo and in vivo experiments demonstrate the clinical potential for intraoperative delineation of disease margin and image-guided resection surgery.

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.

Bioimaging of Hyaluronate-Interferon α Conjugates Using a Non-Interfering Zwitterionic Fluorophore

We conducted real-time bioimaging of the hyaluronate-interferon α (HA-IFNα) conjugate using a biologically inert zwitterionic fluorophore of ZW800-1 for the treatment of hepatitis C virus (HCV) infection. ZW800-1 was labeled on the IFNα molecule of the HA-IFNα conjugate to investigate its biodistribution and clearance without altering its physicochemical and targeting characteristics. Confocal microscopy clearly visualized the effective in vitro cellular uptake of the HA-IFNα conjugate to HepG2 cells. After verifying the biological activity in Daudi cells, we conducted the pharmacokinetic analysis of the HA-IFNα conjugate, which confirmed its target-specific delivery to the liver with a prolonged residence time longer than that of PEGylated IFNα. In vivo and ex vivo bioimaging of the ZW800-1-labeled HA-IFNα conjugate directly showed real-time biodistribution and clearance of the conjugate that are consistent with the biological behaviors analyzed by an enzyme-linked immunosorbent assay. Furthermore, the elevated level of OAS1 mRNA in the liver confirmed in vivo antiviral activity of HA-IFNα conjugates. With the data taken together, we could confirm the feasibility of ZW800-1 as a biologically inert fluorophore and target-specific HA-IFNα conjugate for the treatment of HCV infection.

Application of fluorescence in robotic general surgery: review of the literature and state of the art

The initial use of the indocyanine green fluorescence imaging system was for sentinel lymph node biopsy in patients with breast or colorectal cancer. Since then, application of this method has received wide acceptance in various fields of surgical oncology, and it has become a valid diagnostic tool for guiding cancer treatment. It has also been employed in numerous conventional surgical procedures with much success and benefit to the patient. The advent of minimally invasive surgery brought with it a new use for fluorescence in helping to improve the safety of these procedures, particularly for single-site procedures. In 2010, a near-infrared camera was integrated into the da Vinci Si System, creating a combination of technical and minimally invasive advantages that have been embraced by several experienced surgeons. The use of fluorescence, although useful, is considered challenging. Only a few studies are currently available on the use of fluorescence in robotic general surgery, whereas many articles have focused on its application in open and laparoscopic surgery. Many of these reports describe promising and satisfactory results, although with some shortcomings. The purpose of this article is to review the current status of the use of fluorescence in general surgery and particularly its role in robotic surgery. We also review potential uses in the future.

Optimization of near-infrared fluorescence cholangiography for open and laparoscopic surgery

BACKGROUND

During laparoscopic cholecystectomy, common bile duct (CBD) injury is a rare but severe complication. To reduce the risk of injury, near-infrared (NIR) fluorescent cholangiography using indocyanine green (ICG) has recently been introduced as a novel method of visualizing the biliary system during surgery. To date, several studies have shown feasibility of this technique; however, liver background fluorescence remains a major problem during fluorescent cholangiography. The aim of the current study was to optimize ICG dose and timing for NIR cholangiography using a quantitative intraoperative camera system during open hepatopancreatobiliary (HPB) surgery. Subsequently, these results were validated during laparoscopic cholecystectomy using a laparoscopic fluorescence imaging system.

METHODS

Twenty-seven patients who underwent NIR imaging using the Mini-FLARE image-guided surgery system during open HPB surgery were analyzed to assess optimal dosage and timing of ICG administration. ICG was intravenously injected preoperatively at doses of 5, 10, and 20 mg, and imaged at either 30 min (early) or 24 h (delayed) post-injection. Next, the optimal doses found for early and delayed imaging were applied to two groups of seven patients (n = 14) undergoing laparoscopic NIR fluorescent cholangiography during laparoscopic cholecystectomy.

RESULTS

Median liver-to-background contrast was 23.5 (range 22.1–35.0), 16.8 (range 11.3–25.1), 1.3 (range 0.7–7.8), and 2.5 (range 1.3–3.6) for 5 mg/30 min, 10 mg/30 min, 10 mg/24 h, and 20 mg/24 h, respectively. Fluorescence intensity of the liver was significantly lower in the 10 mg delayed-imaging dose group compared with the early imaging 5 and 10 mg dose groups (p = 0.001), which resulted in a significant increase in CBD-to-liver contrast ratio compared with the early administration groups (p < 0.002). These findings were qualitatively confirmed during laparoscopic cholecystectomy.

CONCLUSION

This study shows that a prolonged interval between ICG administration and surgery permits optimal NIR cholangiography with minimal liver background fluorescence.

Fluorescent imaging of the biliary tract during laparoscopic cholecystectomy

The introduction of laparoscopic cholecystectomy was associated with increased incidences of bile duct injury. The primary cause appears to be misidentification of the biliary anatomy. Routine intra-operative cholangiography has been recommended to reduce accidental duct injury, although in practice it is more often reserved for selected cases. There has been interest in the use of fluorescent agents excreted via the biliary system to enable real-time intra-operative imaging, to aid the laparoscopic surgeon in correctly interpreting the anatomy. The primary aim of this review is to evaluate the ability of fluorescent cholangiography to identify important biliary anatomy intra-operatively. Secondary aims are to investigate its ability to detect important intra-operative pathology such as bile leaks, identify potential alternative fluorophores, and evaluate the evidence regarding patient outcomes.

Endoscopic molecular imaging of cancer

White light endoscopy has proven to be a very powerful tool in oncology. There is still, however, a need for better endoscopic techniques to overcome the current limitations of white light optics. New technologies that allow higher sensitivity, improved microanatomy and molecular characterization have been available for in vitro microscopy and are now being translated into in vivo endoscopy. Endoscopic molecular imaging is still in its infancy but holds the promise for enhancing sensitivity for early lesions, thus allowing earlier diagnosis and enabling early image-guided endoscopic intervention. A key feature of endoscopic molecular imaging is its increased sensitivity and specificity, which will be illustrated in this article, as well as describing perspectives on its future use in oncologic surgery.

From shadow to light: visualization of extrahepatic bile ducts using image-enhanced laparoscopy

BACKGROUND

Correct recognition of the extrahepatic bile ducts is thought to be crucial to reduce the risk of bile duct injuries during various laparoscopic procedures. Image-enhanced laparoscopy techniques, utilizing various optical modalities other than white light, may help in detecting structures "hidden" underneath connective tissue.

METHODS

A systematic literature search was conducted of studies describing image-enhanced laparoscopy techniques for visualization of the extrahepatic bile ducts.

RESULTS

In all, 29 articles met inclusion criteria. They describe various techniques in the animal or human setting, including autofluorescence imaging, drug-enhanced fluorescence imaging, infrared thermography, and spectral imaging. This review describes these various techniques and their results.

CONCLUSION

Image-enhanced laparoscopy techniques for real-time visualization of extrahepatic bile ducts are still in its infancy. Out of the techniques currently described, indocyanine green-enhanced near-infrared fluorescence laparoscopy has the most mature results, but other techniques also appear promising. It can be expected that in the future, image-enhanced laparoscopy might become a routine adjunct to any white-light laparoscopic operation near the hepatic hilum.

Near-infrared fluorescence laparoscopy of the cystic duct and artery in pigs: performance of a preclinical dye

BACKGROUND

Near-infrared fluorescence laparoscopy after intravenous indocyanine green (ICG) administration has been proposed as a promising surgical imaging technique for real-time visualization of the extrahepatic bile ducts and arteries in clinical laparoscopic cholecystectomies. However, optimization of this new technique with respect to the imaging system combined with the fluorophore is desirable. The performance of a preclinical near-infrared dye, CW800-CA, was compared with that of ICG for near-infrared fluorescence laparoscopy of the cystic duct and artery in pigs.

MATERIALS AND METHODS

Laparoscopic cholecystectomy was performed in six pigs (average weight, 35 kg) using a commercially available laparoscopic fluorescence imaging system. The fluorophores CW800-CA and ICG (both 800 nm fluorescent dyes) were administered by intravenous injection in four and two pigs, respectively. CW800-CA was administered in three different doses (consecutively 0.25, 1, and 3 mg); ICG was intravenously injected (2.5 mg) for comparison. Intraoperative recognition of the biliary structures was recorded at set time points. The target-to-background ratio was determined to quantify the fluorescence signal of the designated tissues.

RESULTS

A clinically proven dose of 2.5 mg of ICG resulted in a successful fluorescence delineation of both the cystic duct and artery. In the CW800-CA-injected pigs a clear visualization of the cystic duct and artery was obtained after administration of 3 mg of CW800-CA. Time from injection until fluorescence identification of the cystic duct was reduced when CW800-CA was used compared with ICG (11.5 minutes versus 21.5 minutes, respectively). CW800-CA provided clearer illumination of the cystic artery, in terms of target-to-background ratio.

CONCLUSIONS

As well as ICG, CW800-CA can be applied for fluorescence identification of the cystic artery and duct using a commercially available laparoscopic fluorescence imaging system. Fluorescence cholangiography of the cystic duct can be obtained earlier after intravenous injection of CW800-CA, compared with ICG. These findings increase the possibilities of use and of optimization of this imaging technique.

Application of a new dye for near-infrared fluorescence laparoscopy of the ureters: demonstration in a pig model

BACKGROUND

Ureteral injury during laparoscopic colorectal surgery is a rare but serious complication with a reported incidence rate of 0.66%. The early detection and prevention of ureteral injury is clinically relevant and important. The successful use of preclinical near-infrared fluorophore CW800-CA for real-time intraoperative identification of the anatomical course of the ureters with the use of a laparoscopic fluorescence imaging system is reported.

METHODS

The usefulness of this new imaging technique was explored in two 35-kg pigs. Intravenous CW800-CA was administered 10 minutes before fluorescence imaging was conducted with the use of a commercially available laparoscopic fluorescence imaging system.

RESULTS

A dose of 1 mg/mL CW800-CA (bolus injection of 3 mL) provided clear delineation of the course of both ureters by using the fluorescence mode of the laparoscope. There were no adverse reactions to the injected dye.

CONCLUSION

Near-infrared fluorescence laparoscopy of the ureters, following intravenous CW800-CA administration, is easily applicable and provides real-time identification of the course of the ureters.

Image-guided cancer surgery using near-infrared fluorescence

Paradigm shifts in surgery arise when surgeons are empowered to perform surgery faster, better and less expensively than current standards. Optical imaging that exploits invisible near-infrared (NIR) fluorescent light (700-900 nm) has the potential to improve cancer surgery outcomes, minimize the time patients are under anaesthesia and lower health-care costs largely by way of its improved contrast and depth of tissue penetration relative to visible light. Accordingly, the past few years have witnessed an explosion of proof-of-concept clinical trials in the field. In this Review, we introduce the concept of NIR fluorescence imaging for cancer surgery, examine the clinical trial literature to date and outline the key issues pertaining to imaging system and contrast agent optimization. Although NIR seems to be superior to many traditional imaging techniques, its incorporation into routine care of patients with cancer depends on rigorous clinical trials and validation studies.

Image-guided hepatopancreatobiliary surgery using near-infrared fluorescent light

Background

Improved imaging methods and surgical techniques have created a new era in hepatopancreatobiliary (HPB) surgery. Despite these developments, visual inspection, palpation, and intraoperative ultrasound remain the most utilized tools during surgery today. This is problematic, though, especially in laparoscopic HPB surgery, where palpation is not possible. Optical imaging using near-infrared (NIR) fluorescence can be used for the real-time assessment of both anatomy (e.g., sensitive detection and demarcation of tumours and vital structures) and function (e.g., assessment of luminal flow and tissue perfusion) during both open and minimally invasive surgeries.

Methods

This article reviews the published literature related to preclinical development and clinical applications of NIR fluorescence imaging during HPB surgery.

Results

NIR fluorescence imaging combines the use of otherwise invisible NIR fluorescent contrast agents and specially designed camera systems, which are capable of detecting these contrast agents during surgery. Unlike visible light, NIR fluorescent light can penetrate several millimetres through blood and living tissue, thus providing improved detectability. Applications of this technique during HPB surgery include tumour imaging in liver and pancreas, and real-time imaging of the biliary tree.

Conclusions

NIR fluorescence imaging is a promising new technique that may someday improve surgical accuracy and lower complications.

Targeted zwitterionic near-infrared fluorophores for improved optical imaging

The signal-to-background ratio (SBR) is the key determinant of sensitivity, detectability and linearity in optical imaging. As signal strength is often constrained by fundamental limits, background reduction becomes an important approach for improving the SBR. We recently reported that a zwitterionic near-infrared (NIR) fluorophore, ZW800-1, exhibits low background. Here we show that this fluorophore provides a much-improved SBR when targeted to cancer cells or proteins by conjugation with a cyclic RGD peptide, fibrinogen or antibodies. ZW800-1 outperforms the commercially available NIR fluorophores IRDye800-CW and Cy5.5 in vitro for immunocytometry, histopathology and immunoblotting and in vivo for image-guided surgery. In tumor model systems, a tumor-to-background ratio of 17.2 is achieved at 4 h after injection of ZW800-1 conjugated to cRGD compared to ratios of 5.1 with IRDye800-CW and 2.7 with Cy5.5. Our results suggest that introducing zwitterionic properties into targeted fluorophores may be a general strategy for improving the SBR in diagnostic and therapeutic applications.

Simultaneous Assessment of Luminal Integrity and Vascular Perfusion of the Gastrointestinal Tract Using Dual-Channel Near-Infrared Fluorescence

Anastomotic complications such as stenosis and leakage in the gastrointestinal (GI) tract can cause high patient morbidity and mortality. To identify the potential preconditions of these complications intraoperatively, we explored the use of two 700 nm near-infrared (NIR) fluorophores administered intraluminally: (1) chlorella, an over-the-counter herbal supplement containing high concentrations of chlorophyll, and (2) methylene blue (MB). In parallel, we administered the 800 nm NIR fluorophore indocyanine green (ICG) intravenously to assess vascular function. Dual-channel, real-time intraoperative imaging and quantitation of the contrast to background ratio (CBR) were performed under normal conditions or after anastomosis or leakage of the stomach and intestines in 35 kg Yorkshire pigs using the Fluorescence-Assisted Resection and Exploration (FLARE) imaging system. Luminal integrity could be assessed with relatively high sensitivity with either chlorella or MB, although chlorella provided significantly higher CBR. ICG angiography provided assessment of blood perfusion of normal, ischemic, and anastomotic areas of the GI tract. Used simultaneously, 700 nm (chlorella or MB) and 800 nm (ICG) NIR fluorescence permitted independent assessment of luminal integrity and vascular perfusion of the GI tract intraoperatively and in real time. This technology has the potential to identify critical complications, such as anastomotic leakage, intraoperatively, when correction is still possible.

Simultaneous assessment of luminal integrity and vascular perfusion of the gastrointestinal tract using dual-channel near-infrared fluorescence

Anastomotic complications such as stenosis and leakage in the gastrointestinal (GI) tract can cause high patient morbidity and mortality. To identify the potential preconditions of these complications intraoperatively, we explored the use of two 700 nm near-infrared (NIR) fluorophores administered intraluminally: (1) chlorella, an over-the-counter herbal supplement containing high concentrations of chlorophyll, and (2) methylene blue (MB). In parallel, we administered the 800 nm NIR fluorophore indocyanine green (ICG) intravenously to assess vascular function. Dual-channel, real-time intraoperative imaging and quantitation of the contrast to background ratio (CBR) were performed under normal conditions or after anastomosis or leakage of the stomach and intestines in 35 kg Yorkshire pigs using the Fluorescence-Assisted Resection and Exploration (FLARE) imaging system. Luminal integrity could be assessed with relatively high sensitivity with either chlorella or MB, although chlorella provided significantly higher CBR. ICG angiography provided assessment of blood perfusion of normal, ischemic, and anastomotic areas of the GI tract. Used simultaneously, 700 nm (chlorella or MB) and 800 nm (ICG) NIR fluorescence permitted independent assessment of luminal integrity and vascular perfusion of the GI tract intraoperatively and in real time. This technology has the potential to identify critical complications, such as anastomotic leakage, intraoperatively, when correction is still possible.

Real-time simultaneous near-infrared fluorescence imaging of bile duct and arterial anatomy

BACKGROUND

We hypothesized that two independent wavelengths of near-infrared (NIR) fluorescent light could be used to identify bile ducts and hepatic arteries simultaneously, and intraoperatively.

MATERIALS AND METHODS

Three different combinations of 700 and 800 nm fluorescent contrast agents specific for bile ducts and arteries were injected into N = 10 35-kg female Yorkshire pigs intravenously. Combination 1 (C-1) was methylene blue (MB) for arterial imaging and indocyanine green (ICG) for bile duct imaging. Combination 2 (C-2) was ICG for arterial imaging and MB for bile duct imaging. Combination 3 (C-3) was a newly developed, zwitterionic NIR fluorophore ZW800-1 for arterial imaging and MB for bile duct imaging. Open and minimally invasive surgeries were imaged using the fluorescence-assisted resection and exploration (FLARE) surgical imaging system and minimally invasive FLARE (m-FLARE) imaging systems, respectively.

RESULTS

Although the desired bile duct and arterial anatomy could be imaged with contrast-to-background ratios (CBRs) ≥ 6 using all three combinations, each one differed significantly in terms of repetition and prolonged imaging. ICG injection resulted in high CBR of the liver and common bile duct (CBD) and prolonged imaging time (120 min) of the CBD (C-1). However, because ICG also resulted in high background of liver and CBD relative to arteries, ICG produced a lower arterial CBR (C-2) at some time points. C-3 provided the best overall performance, although C-2, which is clinically available, did enable effective laparoscopy.

CONCLUSIONS

We demonstrate that dual-channel NIR fluorescence imaging provides simultaneous, real-time, and high resolution identification of bile ducts and hepatic arteries during biliary tract surgery.

Risk factors for central bile duct injury complicating partial liver resection

BACKGROUND

Bile duct injury is a serious complication following liver resection. Few studies have differentiated between leakage from small peripheral bile ducts and central bile duct injury (CBDI), defined as an injury leading to leakage or stenosis of the common bile duct, common hepatic duct, right or left hepatic duct. This study analysed the incidence, risk factors and consequences of CBDI in liver resection.

METHODS

Patients undergoing liver resection between 1990 and 2007 were included in this study. Those having resection for bile duct-related pathology or trauma, or after liver transplantation were excluded. Characteristics and outcome variables were collected prospectively and analysed retrospectively.

RESULTS

There were 19 instances of CBDI in 462 liver resections (4·1 per cent). One-third of patients with CBDI required surgical reintervention and construction of a hepaticojejunostomy. Resection type (P < 0·001), previous liver resection (P = 0·039) and intraoperative blood loss (P = 0·002) were associated with an increased risk of CBDI. Of all resection types, extended left hemihepatectomy was associated with the highest incidence of CBDI (2 of 9 procedures).

CONCLUSION

Patients undergoing extended left hemihepatectomy or repeat hepatectomy were at increased risk of CBDI.

Inert coupling of IRDye800CW to monoclonal antibodies for clinical optical imaging of tumor targets

Background

Photoimmunodetection, in which monoclonal antibodies [mAbs] are labeled with fluorescent dyes, might have clinical potential for early detection and characterization of cancer. For this purpose, the dye should be coupled in an inert way to mAb. In this study, different equivalents of IRDye800CW, a near-infrared fluorescent dye, were coupled to ⁸⁹Zr-labeled cetuximab and bevacizumab, and conjugates were evaluated in biodistribution studies. Radiolabeled mAbs were used to allow accurate quantification for assessment of the number of dye groups that can be coupled to mAbs without affecting their biological properties.

Methods

⁸⁹Zr-cetuximab and ⁸⁹Zr-bevacizumab, containing 0.5 ⁸⁹Zr-desferal group per mAb molecule, were incubated with 1 to 10 eq IRDye800CW at pH 8.5 for 2 h at 35°C, and ⁸⁹Zr-mAb-IRDye800CW conjugates were purified by a PD10 column using 0.9% NaCl as eluent. HPLC analysis at 780 nm was used to assess conjugation efficiency. In vitro stability measurements were performed in storage buffer (0.9% NaCl or PBS) at 4°C and 37°C and human serum at 37°C. ⁸⁹Zr-mAb-IRDye800CW conjugates and ⁸⁹Zr-mAb conjugates (as reference) were administered to nude mice bearing A431 (cetuximab) or FaDu (bevacizumab) xenografts, and biodistribution was assessed at 24 to 72 h after injection.

Results

Conjugation efficiency of IRDye800CW to ⁸⁹Zr-mAbs was approximately 50%; on an average, 0.5 to 5 eq IRDye800CW was conjugated. All conjugates showed optimal immunoreactivity and were > 95% stable in storage buffer at 4°C and 37°C and human serum at 37°C for at least 96 h. In biodistribution studies with ⁸⁹Zr-cetuximab-IRDye800CW, enhanced blood clearance with concomitant decreased tumor uptake and increased liver uptake was observed at 24 to 72 h post-injection when 2 or more eq of dye had been coupled to mAb. No significant alteration of biodistribution was observed 24 to 48 h after injection when 1 eq of dye had been coupled. ⁸⁹Zr-bevacizumab-IRDye800CW showed a similar tendency, with an impaired biodistribution when 2 eq of dye had been coupled to mAb.

Conclusion

Usage of ⁸⁹Zr-mAbs allows accurate quantification of the biodistribution of mAbs labeled with different equivalents of IRDye800CW. Alteration of biodistribution was observed when more than 1 eq of IRDye800CW was coupled to mAbs.

Synthesis, in vitro evaluation, and in vivo metabolism of fluor/quencher compounds containing IRDye 800CW and Black Hole Quencher-3 (BHQ-3)

Protease-cleavable peptides containing a suitable fluor/quencher (Fl/Q) pair are optically dark until cleaved by their target protease, generating fluorescence. This approach has been used with many Fl/Q pairs, but little has been reported with IRDye 800CW, a popular near-infrared (NIR) fluor. We explored the use of the azo-bond-containing Black Hole Quencher 3 (BHQ-3) as a quencher for IRDye 800CW and found that IRDye 800CW/BHQ-3 is a suitable Fl/Q pair, despite the lack of proper spectral overlap for fluorescence resonance energy transfer (FRET) applications. Cleavage of IRDye 800CW-PLGLK(BHQ-3)AR-NH(2) (8) and its D-arginine (Darg) analogue (9) by matrix metalloproteinases (MMPs) in vitro yielded the expected cleavage fragments. In vivo, extensive metabolism was found. Significant decomposition of a "non-cleavable" control IRDye 800CW-(1,13-diamino-4,7,10-trioxatridecane)-BHQ-3 (10) was evident in plasma of normal mice by 3 min post injection. The major metabolite showed a m/z and UV/vis spectrum consistent with azo bond cleavage in the BHQ-3 moiety. Preparation of an authentic standard of this metabolite (11) confirmed the assignment. Although the IRDye 800CW/BHQ-3 constructs showed efficient contact quenching prior to enzymatic cleavage, BHQ-3 should be used with caution in vivo, due to instability of its azo bond.

Characterization of chemical, radiochemical and optical properties of a dual-labeled MMP-9 targeting peptide

Optical imaging possesses similar sensitivity to nuclear imaging and has led to the emergence of multimodal approaches with dual-labeled nuclear/near-infrared (NIR) agents. The growing impact of (68)Ga (t(1/2)=68 min) labeled peptides on preclinical and clinical research offers a promising opportunity to merge the high spatial resolution of NIR imaging with the clinically-accepted positron emission tomography (PET). Previously, dual-labeled agents have been prepared with longer-lived radiometals and showed no detrimental effects on optical properties as a result of radiolabeling. In this study, we selected a peptide (M(2)) that targets MMP-2/9 and is dual-labeled with IRDye 800 CW and (68)Ga. Since (68)Ga chelation typically requires low pH (3.5-4) and elevated heating temperatures (95 °C), we sought to evaluate the impact of (68)Ga labeling on the optical properties of M(2). An efficient method for preparation of (68)Ga-M(2) was developed and reaction conditions were optimized. Stability studies in PBS, DTPA, and serum were performed and high levels of intact agent were evident under each condition. The addition of multiple reporters to a targeting agent adds further complexity to the characterization and validation and thus requires not only testing to ensure the agent is stable chemically and radiochemically, but also optically. Therefore, fluorescence properties were evaluated using a spectrofluorometer as well as by fluorescence detection via HPLC. It was determined that (68)Ga-labeling conditions did not impair the fluorescent properties of the agent. The agent was then used for in vivo imaging in a mouse model of heterotopic ossification (HO) with activated MMP-9 expression as an early biomarker which precedes mineralization. Although (68)Ga-complexation greatly reduced binding affinity of the peptide and negated tracer uptake on PET, NIR imaging showed consistent fluorescent signal that correlated to MMP-9 expression. This attests to the feasibility of using (68)Ga/NIR for dual-labeling of other peptides or small molecules for multimodality molecular imaging.

Intraoperative assessment of biliary anatomy for prevention of bile duct injury: a review of current and future patient safety interventions

Background

Bile duct injury (BDI) is a dreaded complication of cholecystectomy, often caused by misinterpretation of biliary anatomy. To prevent BDI, techniques have been developed for intraoperative assessment of bile duct anatomy. This article reviews the evidence for the different techniques and discusses their strengths and weaknesses in terms of efficacy, ease, and cost-effectiveness.

Method

PubMed was searched from January 1980 through December 2009 for articles concerning bile duct visualization techniques for prevention of BDI during laparoscopic cholecystectomy.

Results

Nine techniques were identified. The critical-view-of-safety approach, indirectly establishing biliary anatomy, is accepted by most guidelines and commentaries as the surgical technique of choice to minimize BDI risk. Intraoperative cholangiography is associated with lower BDI risk (OR 0.67, CI 0.61–0.75). However, it incurs extra costs, prolongs the operative procedure, and may be experienced as cumbersome. An established reliable alternative is laparoscopic ultrasound, but its longer learning curve limits widespread implementation. Easier to perform are cholecystocholangiography and dye cholangiography, but these yield poor-quality images. Light cholangiography, requiring retrograde insertion of an optical fiber into the common bile duct, is too unwieldy for routine use. Experimental techniques are passive infrared cholangiography, hyperspectral cholangiography, and near-infrared fluorescence cholangiography. The latter two are performed noninvasively and provide real-time images. Quantitative data in patients are necessary to further evaluate these techniques.

Conclusions

The critical-view-of-safety approach should be used during laparoscopic cholecystectomy. Intraoperative cholangiography or laparoscopic ultrasound is recommended to be performed routinely. Hyperspectral cholangiography and near-infrared fluorescence cholangiography are promising novel techniques to prevent BDI and thus increase patient safety.

Combined intraoperative use of contrast-enhanced ultrasonography imaging using a sonazoid and fluorescence navigation system with indocyanine green during anatomical hepatectomy

PURPOSE

The clear demarcation line is ideal for real-time surgical navigation imaging during hepatectomy.

METHODS

The study population was comprised of 22 patients with moderate liver cirrhosis scheduled to undergo an anatomical liver resection for the treatment of hepatocellular carcinoma. This study set out to assess the clinical value of the concomitant intra-operative use of contrast-enhanced intra-operative ultrasound using Sonazoid™, and a fluorescence navigation system (PDE) with ICG, as a novel tool for patients undergoing an anatomical liver resection.

RESULTS

Following portal pedicle ligation for anatomical resection, 2 min after injection of ICG, the segments to be resected were detected as a negative-brightness area using PDE fluorescence. Sonazoid™ administration provides a parenchymal transectional line, as the margin of a loss of blood flow shows a hypo-enhanced image, and the resectional line of the parenchyma can be confirmed by CE-IOUS. Although the demarcation line of the liver surface after the portal pedicle ligation was apparent in 17 patients, the resection line using PDE was clearly detected in all 22 patients (p < 0.018).

CONCLUSIONS

The combined use of these methods is therefore considered to be useful and safe for surgeons, as an additional tool for performing a liver resection.

Image-guided surgery using invisible near-infrared light: fundamentals of clinical translation

The field of biomedical optics has matured rapidly over the last decade and is poised to make a significant impact on patient care. In particular, wide-field (typically > 5 cm), planar, near-infrared (NIR) fluorescence imaging has the potential to revolutionize human surgery by providing real-time image guidance to surgeons for tissue that needs to be resected, such as tumors, and tissue that needs to be avoided, such as blood vessels and nerves. However, to become a clinical reality, optimized imaging systems and NIR fluorescent contrast agents will be needed. In this review, we introduce the principles of NIR fluorescence imaging, analyze existing NIR fluorescence imaging systems, and discuss the key parameters that guide contrast agent development. We also introduce the complexities surrounding clinical translation using our experience with the Fluorescence-Assisted Resection and Exploration (FLARE™) imaging system as an example. Finally, we introduce state-of-the-art optical imaging techniques that might someday improve image-guided surgery even further.

Real-time optical imaging using quantum dot and related nanocrystals

Biomedical optical imaging is rapidly evolving because of its desirable features of rapid frame rates, high sensitivity, low cost, portability and lack of radiation. Quantum dots are attractive as imaging agents owing to their high brightness, and photo- and bio-stability. Here, the current status of in vitro and in vivo real-time optical imaging with quantum dots is reviewed. In addition, we consider related nanocrystals based on solid-state semiconductors, including upconverting nanoparticles and bioluminescence resonance energy transfer quantum dots. These particles can improve the signal-to-background ratio for real-time imaging largely by suppressing background signal. Although toxicity and biodistribution of quantum dots and their close relatives remain prime concerns for translation to human imaging, these agents have many desirable features that should be explored for medical purposes.

Intraoperative near-infrared fluorescent cholangiography (NIRFC) in mouse models of bile duct injury

BACKGROUND

Accidental injury to the common bile duct is a rare but serious complication of laparoscopic cholecystectomy. Accurate visualization of the biliary ducts may prevent injury or allow its early detection. Conventional X-ray cholangiography is often used and can mitigate the severity of injury when correctly interpreted. However, it may be useful to have an imaging method that could provide real-time extrahepatic bile duct visualization without changing the field of view from the laparoscope. The purpose of the present study was to test a new near-infrared (NIR) fluorescent agent that is rapidly excreted via the biliary route in preclinical models to evaluate intraoperative real-time near infrared fluorescent cholangiography (NIRFC).

METHODS

To investigate probe function and excretion, a lipophilic near-infrared fluorescent agent with hepatobiliary excretion was injected intravenously into one group of C57/BL6 control mice and four groups of C57/BL6 mice under the following experimentally induced conditions: (1) chronic biliary obstruction, (2) acute biliary obstruction (3) bile duct perforation, and (4) choledocholithiasis, respectively. The biliary system was imaged intravitally for 1 h with near-infrared fluorescence (NIRF) with an intraoperative small animal imaging system (excitation 649 nm, emission 675 nm).

RESULTS

The extrahepatic ducts and extraluminal bile were clearly visible due to the robust fluorescence of the excreted fluorochrome. Twenty-five minutes after intravenous injection, the target-to-background ratio peaked at 6.40 +/- 0.83 but signal was clearly visible for ~60 min. The agent facilitated rapid identification of biliary obstruction and bile duct perforation. Implanted beads simulating choledocholithiasis were promptly identifiable within the common bile duct lumen.

CONCLUSIONS

Near-infrared fluorescent agents with hepatobiliary excretion may be used intraoperatively to visualize extrahepatic biliary anatomy and physiology. Used in conjunction with laparoscopic imaging technologies, the use of this technique should enhance hepatobiliary surgery.

Real-time intra-operative near-infrared fluorescence identification of the extrahepatic bile ducts using clinically available contrast agents

BACKGROUND

Iatrogenic bile duct injuries are serious complications with patient morbidity. We hypothesized that the invisible near-infrared (NIR) fluorescence properties of methylene blue (MB) and indocyanine green (ICG) could be exploited for real-time, intraoperative imaging of the extrahepatic bile ducts during open and laparoscopic surgeries.

METHODS

In all, 2.0 mg/kg of MB and 0.05 mg/kg of ICG were injected intravenously into 35-kg female Yorkshire pigs and the extrahepatic bile ducts were imaged over time using either the Fluorescence-Assisted Resection and Exploration (FLARE) image-guided surgery system (open surgery) or a custom NIR fluorescence laparoscopy system. Surgical anatomy was confirmed using x-ray cholangiography. The contrast-to-background ratio (CBR), contrast-to-liver ratio (CLR), and chemical concentrations in the cystic duct (CD) and common bile duct (CBD) were measured, and the performance of each agent was quantified.

RESULTS

Using NIR fluorescence of MB, the CD and CBD could be identified with good sensitivity (CBR and CLR > or =4), during both open and laparoscopic surgeries, from 10 to 120 min postinjection. Functional impairment of the ducts, including constriction and injury were immediately identifiable. Using NIR fluorescence of ICG, extrahepatic bile ducts did not become visible until 90 min postinjection because of strong residual liver retention; however, between 90 and 240 min, ICG provided exquisitely high sensitivity for both CD and CBD, with CBR > or =8 and CLR > or =4.

CONCLUSION

We demonstrate that 2 clinically available NIR fluorophores, MB fluorescing at 700 nm and ICG fluorescing at 800 nm, provide sensitive, prolonged identification of the extrahepatic bile ducts and assessment of their functional status.

Biodistribution of encapsulated indocyanine green in healthy mice

Indocyanine green (ICG) is a fluorescent probe used in various optically mediated diagnostic and therapeutic applications. However, utility of ICG remains limited by its unstable optical properties and nonspecific localization. We have encapsulated ICG within electrostatically assembled mesocapsules (MCs) to explore its potential for targeted optical imaging and therapy. In this study, we investigate how the surface coating and size of the MCs influences ICG's biodistribution in vivo. ICG was administered intravenously to Swiss Webster mice as a free solution or encapsulated within either 100 nm diameter MCs coated with dextran; 500 nm diameter MCs coated with dextran; or 100 nm diameter MCs coated with 10 nm ferromagnetic iron oxide nanoparticles, themselves coated with polyethylene glycol. ICG was extracted from harvested blood and organs at various times and its amount quantified with fluorescence measurements. MCs containing ICG accumulated in organs of the reticuloendothelial system, namely, the liver and spleen, as well as the lungs. The circulation kinetics of ICG appeared unaffected by encapsulation; however, the deposition within organs other than the liver suggests a different biodistribution mechanism. Results suggest that the capsules' coating influences their biodistribution to a greater extent than their size. The MC encapsulation system allows for delivery of ICG to organs other than the liver, enabling the potential development of new optical imaging and therapeutic strategies.

Clinical implications of near-infrared fluorescence imaging in cancer

Near-infrared (NIR) fluorescence cancer imaging is a growing field for both preclinical and clinical application to the clinical management for cancer patients due to its advantageous features, including a high spatial resolution, portability, real-time display and detailed molecular profiling with the multiplexed use of fluorescent probes. In this review, we present a basic concept of NIR fluorescence imaging and overview its potential clinical applications for in vivo cancer imaging, including cancer detection/characterization, lymphatic imaging (sentinel lymph node detection) and surgical/endoscopic guidance. NIR fluorescence imaging can compensate some limitations of conventional imaging modalities, and thus it could play an important role for cancer imaging combined with other modalities in clinical practice.

Intraoperative exploration of biliary anatomy using fluorescence imaging of indocyanine green in experimental and clinical cholecystectomies

BACKGROUND/PURPOSE

We evaluated the usefulness of intraoperative exploration of the biliary anatomy using fluorescence imaging with indocyanine green (ICG) in experimental and clinical cholecystectomies.

METHODS

The experimental study was done using two 40-kg pigs and the clinical study was done in 12 patients for whom cholecystectomy was planned from January 2009 to June 2009. Initially we used a laparoscopic approach for the evaluation of fluorescence imaging of the biliary system in the two pigs. Then the clinical study was started on the basis of these experimental results. ICG (1.0 ml/body of 2.5 mg/ml ICG) was infused 1-2 h before surgery. With the subjects under general anesthesia we observed in real time the condition of the biliary tract under the guidance of fluorescence imaging employing an infrared camera or a prototype laparoscope. ICG was added intravenously to observe the location or flow condition of the cystic artery.

RESULTS

We obtained a clear view of the biliary tract and the location of the cystic duct in the two pigs. Local compression with a transparent hemispherical plastic device was effective for offering a clearer view. The biliary tract, except for the gallbladder, was clearly recognized in all clinical subjects. Local compression with a transparent hemispherical plastic device for open cholecystectomy and a flat plastic device for laparoscopy provided clearer visualization of the confluence between the cystic duct and common bile duct or common hepatic duct. The location of the cystic artery was revealed after division of the connective tissues, and the flow condition of the cystic artery was confirmed 7-10 s after intravenous re-infusion of ICG. There were no adverse events related to the intraoperative procedure or the ICG itself.

CONCLUSIONS

This method is safe and easy for the identification of the biliary anatomy, without requiring cannulation into the cystic duct, X-ray equipment, or the use of radioactive materials. Although fluorescence imaging is still at an early stage of application in comparison with ordinary intraoperative cholangiography, we expect that this method will become routine, offering a lower degree of invasiveness that will help avoid bile duct injury.

Real-time assessment of cardiac perfusion, coronary angiography, and acute intravascular thrombi using dual-channel near-infrared fluorescence imaging

OBJECTIVES

We have developed an image-guided surgical system based on invisible near-infrared fluorescent light. Presently, the only clinically available near-infrared fluorophore is indocyanine green, which fluoresces at approximately 800 nm and is used for coronary angiography. Our objective was to determine whether methylene blue, already US Food and Drug Administration approved for other indications, has useful near-infrared fluorescence properties for image-guided cardiac surgery.

METHODS

The optical properties of methylene blue were measured after dissolution in 100% serum. Biodistribution and clearance were quantified in organs and tissue after intravenous bolus injection of 2 mg/kg methylene blue in 3 rats. Coronary arteriography and cardiac perfusion were imaged in real time after intravenous bolus injection of 1 mg/kg methylene blue in 5 pigs with coronary obstructions. Coronary angiography and acute thrombi were assessed by using 800-nm fluorophores, indocyanine green, and IR-786-labeled platelets, respectively.

RESULTS

The peak absorbance and emission of methylene blue as a near-infrared fluorophore occur at 667 nm and 686 nm, respectively. After intravenous injection, methylene blue provides highly sensitive coronary angiography. A lipophilic cation, methylene blue is extracted rapidly into tissue, with myocardium displaying unusually high uptake. Methylene blue permits real-time visualization and quantitative assessment of myocardial perfusion. Because of absent spectral overlap, use of 2 independent fluorophores in our imaging system permits simultaneous quantification of perfusion, venous drainage, and/or intravascular thrombi.

CONCLUSIONS

Methylene blue is an effective near-infrared fluorophore that provides direct visualization of coronary arteriography and cardiac perfusion. In conjunction with approximately 800-nm near-infrared fluorophores, important functional assessments during cardiac surgery are also possible.

The FLARE intraoperative near-infrared fluorescence imaging system: a first-in-human clinical trial in breast cancer sentinel lymph node mapping

BACKGROUND

Invisible NIR fluorescent light can provide high sensitivity, high-resolution, and real-time image-guidance during oncologic surgery, but imaging systems that are presently available do not display this invisible light in the context of surgical anatomy. The FLARE imaging system overcomes this major obstacle.

METHODS

Color video was acquired simultaneously, and in real-time, along with two independent channels of NIR fluorescence. Grayscale NIR fluorescence images were converted to visible "pseudo-colors" and overlaid onto the color video image. Yorkshire pigs weighing 35 kg (n = 5) were used for final preclinical validation of the imaging system. A six-patient pilot study was conducted in women undergoing sentinel lymph node (SLN) mapping for breast cancer. Subjects received (99m)Tc-sulfur colloid lymphoscintigraphy. In addition, 12.5 microg of indocyanine green (ICG) diluted in human serum albumin (HSA) was used as an NIR fluorescent lymphatic tracer.

RESULTS

The FLARE system permitted facile positioning in the operating room. NIR light did not change the look of the surgical field. Simultaneous pan-lymphatic and SLN mapping was demonstrated in swine using clinically available NIR fluorophores and the dual NIR capabilities of the system. In the pilot clinical trial, a total of nine SLNs were identified by (99m)Tc- lymphoscintigraphy and nine SLNs were identified by NIR fluorescence, although results differed in two patients. No adverse events were encountered.

CONCLUSIONS

We describe the successful clinical translation of a new NIR fluorescence imaging system for image-guided oncologic surgery.

Tissue- and organ-selective biodistribution of NIR fluorescent quantum dots

A significant portion of the field of nanomedicine is predicated on being able to target nanoparticles to sites of disease. However, in vivo biodistribution and clearance of nanoparticles are poorly understood. In this study, a novel formulation of near-infrared fluorescent InAs(ZnS) quantum dots was synthesized and coated with a systematically increasing chain length of PEG. We found that varying PEG chain length resulted in major changes in organ/tissue-selective biodistribution and clearance from the body.