Principle and clinical usefulness of the infrared fluorescence endoscopy

A narrative review of fluorescence imaging in robotic-assisted surgery

Objective

In this review, we provide examples of applications of fluorescence imaging in urologic, gynecologic, general, and endocrine surgeries.

Background

While robotic-assisted surgery has helped increase the availability of minimally invasive procedures across surgical specialties, there remains an opportunity to reduce adverse events associated with open, laparoscopic, and robotic-assisted methods. In 2011, fluorescence imaging was introduced as an option to the da Vinci Surgical System, and has been standard equipment since 2014. Without interfering with surgical workflow, this fluorescence technology named Firefly^® allows for acquisition and display of near-infrared fluorescent signals that are co-registered with white light endoscopic images. As a result, robotic surgeons of all specialties have been able to explore the clinical utility of fluorescence guided surgery.

Methods

Literature searches were performed using the PubMed and MEDLINE databases using the keywords "robotic-assisted fluorescence surgery", "ICG robotic surgery", and "fluorescence guided surgery" covering the years 2011-2020.

Conclusions

Real-time intraoperative fluorescence guidance has shown great potential in helping guide surgeons in both simple and complex surgical interventions. Indocyanine green is one of the most widely-used imaging agents in fluorescence guided surgery, and other targeted, near-infrared imaging agents are in various stages of development. Fluorescence is becoming a reliable tool that can help surgeons in their decision-making process in some specialties, while explorations continue in others.

Gastrointestinal diagnosis using non-white light imaging capsule endoscopy

Capsule endoscopy (CE) has proved to be a powerful tool in the diagnosis and management of small bowel disorders since its introduction in 2001. However, white light imaging (WLI) is the principal technology used in clinical CE at present, and therefore, CE is limited to mucosal inspection, with diagnosis remaining reliant on visible manifestations of disease. The introduction of WLI CE has motivated a wide range of research to improve its diagnostic capabilities through integration with other sensing modalities. These developments have the potential to overcome the limitations of WLI through enhanced detection of subtle mucosal microlesions and submucosal and/or transmural pathology, providing novel diagnostic avenues. Other research aims to utilize a range of sensors to measure physiological parameters or to discover new biomarkers to improve the sensitivity, specificity and thus the clinical utility of CE. This multidisciplinary Review summarizes research into non-WLI CE devices by organizing them into a taxonomic structure on the basis of their sensing modality. The potential of these capsules to realize clinically useful virtual biopsy and computer-aided diagnosis (CADx) is also reported.

Application of indocyanine green fluorescence endoscopic system in transsphenoidal surgery for pituitary tumors

BACKGROUND

For the precise removal of pituitary tumors, preserving the surrounding normal structures, we need real-time intraoperative information on tumor location, margins, and surrounding structures. The aim of this study was to evaluate the benefits of a new intraoperative real-time imaging modality using indocyanine green (ICG) fluorescence through an endoscopic system during transsphenoidal surgery (TSS) for pituitary tumors.

METHODS

Between August 2013 and October 2014, 20 patients with pituitary and parasellar region tumors underwent TSS using the ICG fluorescence endoscopic system. We used a peripheral vein bolus dose of 6.25 mg/injection of ICG, started with a time counter, and examined how each tissue type increased and decreased in fluorescence through time.

RESULTS

A total of 33 investigations were performed for 20 patients: 9 had growth hormone secreting adenomas, 6 non-functioning pituitary adenomas, 3 Rathke's cleft cysts, 1 meningioma, and 1 pituicytoma. After the injection of ICG, the intensity of fluorescence of tumor and normal tissues under near-infrared light showed clear differences. We could differentiate tumor margins from adjacent normal tissues and define clearly the surrounding normal structures using the different fluorescent intensities time changes and tissue-specific fluorescence patterns.

CONCLUSIONS

The ICG endoscopic system is simple, user-friendly, quick, cost-effective, and reliable. The method offered real-time information during TSS to delimit pituitary and parasellar region tumor tissue from surrounding normal structures. This method can contribute to the improvement of total removal rates of tumors, reduction of complications after TSS, saving surgical time, and preserving endocrinological functions.

Use of Indocyanine Green Fluorescence Endoscopy to Treat Concurrent Perimedullary and Dural Arteriovenous Fistulas in the Cervical Spine

BACKGROUND

Intraoperative microscopic fluorescence angiography using indocyanine green (ICG) provides visual information on real-time blood flow. However, this method cannot be applied for lesions that are not visible under microscopic imaging because excitation light does not reach the targeted vascular structures. Endoscope-integrated ICG video-angiography has recently been advocated to compensate for this limitation. This is the first reported case of a spinal arteriovenous malformation in which endoscope-integrated ICG video-angiography was successfully used.

CASE DESCRIPTION

We report the case of a 63-year-old man who presented with a subarachnoid hemorrhage from a spinal arteriovenous malformation at the C3 level. We chose the direct surgery option with a posterior approach to treat this lesion. Although the preoperative diagnosis was a perimedullary arteriovenous fistula (AVF) with multiple feeders, we found concurrent dural AVF and perimedullary AVFs during surgery. We introduced an endoscope and performed endoscope-integrated ICG video-angiography because it was difficult to identify the angioarchitectures of the perimedural and dural AVFs on the ventral surface of the spinal cord under microscopic view alone. Endoscope-integrated ICG video-angiography gave us clear and magnified angioarchitectures of these lesions. The fistulous point and the varix of the perimedullary AVF was coagulated and dissected under endoscopic view, and the draining vein of the dural AVF was also coagulated and dissected at the origin from the dura mater under microscopic view.

CONCLUSIONS

A posterior approach with the assistance of an endoscope and endoscope-integrated ICG video-angiography is feasible for spinal vascular diseases located ventrally.

Infrared Fluorescence-Based Cancer Screening Capsule for the Small Intestine

Infrared fluorescence endoscopy (IRFE), in conjunction with an infrared fluorescent-labelling contrast agent, is a well known technique used for efficient early-stage cancer detection. In this paper we present a cost-effective (< $500) screening capsule prototype, which is able to detect infrared (IR) fluorescence emitted by indocyanine green (ICG) fluorophore dye. Rather than image, the capsule works as a high-sensitivity fluorometer that records fluorescence levels throughout the small intestine. The presented mixed-signal system has a small size, consumes very little power (≈ 6.3 mA) and does not require an external belt and hardware for data collection. By determining fluorescence levels in the intestine, rather than collecting images, we avoid the need for labour intensive video analysis. The whole system is contained within a compact ingestible capsule, that is sized so as to come into close contact with the intestine walls during peristalsis. Ex-vivo experiments, on ICG-impregnated swine intestine, have shown that the prototype system is able to detect low concentrations of ICG in the nanomolar and micromolar region, which is required to detect early cancer in the small intestine.

An ingestible, NIR-fluorometric, cancer-screening capsule

Asymptomatic, early-stage, cancer detection is a problem in the small intestine, that is largely inaccessible. This paper presents a cost-effective screening capsule prototype, which is able to detect infrared (IR) fluorescence emitted by indocyanine green (ICG) fluorophore dye. The presented mixed-signal system has a small size, consumes little power and works as a high-sensitivity fluorometer that records fluorescence levels throughout the small intestine, rather than collecting images that need labour intensive video analysis. Ex-vivo experiments, on ICG-impregnated swine intestine, have shown that the prototype system is able to detect low concentrations of ICG in the nanomolar and micromolar region, which is required to detect early cancer in the small intestine.

Near infrared optical visualization of epidermal growth factor receptors levels in COLO205 colorectal cell line, orthotopic tumor in mice and human biopsies

In this study, we present the applicability of imaging epidermal growth factor (EGF) receptor levels in preclinical models of COLO205 carcinoma cells in vitro, mice with orthotopic tumors and ex vivo colorectal tumor biopsies, using EGF-labeled with IRDye800CW (EGF-NIR). The near infrared (NIR) bio-imaging of COLO205 cultures indicated specific and selective binding, reflecting EGF receptors levels. In vivo imaging of tumors in mice showed that the highest signal/background ratio between tumor and adjacent tissue was achieved 48 hours post-injection. Dissected colorectal cancer tissues from different patients demonstrated ex vivo specific imaging using the NIR bio-imaging platform of the heterogeneous distributed EGF receptors. Moreover, in the adjacent gastrointestinal tissue of the same patients, which by Western blotting was demonstrated as EGF receptor negative, no labeling with EGF-NIR probe was detected. Present results support the concept of tumor imaging by measuring EGF receptor levels using EGF-NIR probe. This platform is advantageous for EGF receptor bio-imaging of the NCI-60 recommended panel of tumor cell lines including 6-9 colorectal cell lines, since it avoids radioactive probes and is appropriate for use in the clinical setting using NIR technologies in a real-time manner.

Optical imaging

Non-invasive optical imaging techniques, such as fluorescence imaging (FI) or bioluminescence imaging (BLI) have emerged as important tools in biomedical research. As demonstrated in different animal disease models, they enable visualization of physiological and pathophysiological processes at the cellular and molecular level in vivo with high specificity. Optical techniques are easy to use, fast, and affordable. Furthermore, they are characterized by their high sensitivity. In FI, very low amounts of the imaging agent (nano- to femtomol or even less) can be detected. Due to the absorption and scattering of light in tissue, optical techniques exhibit a comparably low spatial resolution in the millimeter range and a depth limit of a few centimeters. However, non-invasive imaging of biological processes in small animals and in outer or inner surfaces as well as during surgery even in humans is feasible. Currently two agents for fluorescence imaging are clinically approved, namely indocyanine green (ICG) and 5-aminolevulinic acid (5-ALA). In the past years, a number of new optical imaging agents for FI and reporter systems for BLI have been developed and successfully tested in animal models. Some of the FI agents might promise the application in clinical oncology. In this chapter, we describe the basic principles of non-invasive optical imaging techniques, give examples for the visualization of biological processes in animal models of cancer, and discuss potential clinical applications in oncology.

Bio-imaging of colorectal cancer models using near infrared labeled epidermal growth factor

Novel strategies that target the epidermal growth factor receptor (EGFR) have led to the clinical development of monoclonal antibodies, which treat metastatic colorectal cancer (mCRC) but only subgroups of patients with increased wild type KRAS and EGFR gene copy, respond to these agents. Furthermore, resistance to EGFR blockade inevitably occurred, making future therapy difficult. Novel bio-imaging (BOI) methods may assist in quantization of EGFR in mCRC tissue thus complementing the immunohistochemistry methodology, in guiding the future treatment of these patients. The aim of the present study was to explore the usefulness of near infrared-labeled EGF (EGF-NIR) for bio-imaging of CRC using in vitro and in vivo orthotopic tumor CRC models and ex vivo human CRC tissues. We describe the preparation and characterization of EGF-NIR and investigate binding, using BOI of a panel of CRC cell culture models resembling heterogeneity of human CRC tissues. EGF-NIR was specifically and selectively bound by EGFR expressing CRC cells, the intensity of EGF-NIR signal to background ratio (SBR) reflected EGFR levels, dose-response and time course imaging experiments provided optimal conditions for quantization of EGFR levels by BOI. EGF-NIR imaging of mice with HT-29 orthotopic CRC tumor indicated that EGF-NIR is more slowly cleared from the tumor and the highest SBR between tumor and normal adjacent tissue was achieved two days post-injection. Furthermore, images of dissected tissues demonstrated accumulation of EGF-NIR in the tumor and liver. EGF-NIR specifically and strongly labeled EGFR positive human CRC tissues while adjacent CRC tissue and EGFR negative tissues expressed weak NIR signals. This study emphasizes the use of EGF-NIR for preclinical studies. Combined with other methods, EGF-NIR could provide an additional bio-imaging specific tool in the standardization of measurements of EGFR expression in CRC tissues.

Application of near-infrared dyes for tumor imaging, photothermal, and photodynamic therapies

Near-infrared (NIR) dyes, small organic molecules that function in the NIR region, have received increasing attention in recent years as diagnostic and therapeutic agents in the field of tumor research. They have been demonstrated great successes in imaging and treating tumors both in vitro and in vivo. And their different applications in clinical practices have made rapid gains. This review primarily focuses on the progress of the application of NIR dyes in tumor imaging and therapy. In particular, advances in the use of different NIR dyes in tumor-specific imaging, photothermal, and photodynamic therapies are discussed. Limitations and prospects associated with NIR dyes in diagnostic and therapeutic application are also reviewed.

Autofluorescence imaging and magnification endoscopy

It is well known that angiogenesis is critical in the transition from premalignant to malignant lesions. Consequently, early detection and diagnosis based on morphological changes to the microvessels are crucial. In the last few years, new imaging techniques which utilize the properties of light-tissue interaction have been developed to increase early diagnosis of gastrointestinal (GI) tract neoplasia. We analyzed several “red-flag” endoscopic techniques used to enhance visualization of the vascular pattern of preneoplastic and neoplastic lesions (e.g. trimodal imaging including autofluorescence imaging, magnifying endoscopy and narrow band imaging). These new endoscopic techniques provide better visualization of mucosal microsurface structure and microvascular architecture and may enhance the diagnosis and characterization of mucosal lesions in the GI tract. In the near future, it is expected that trimodal imaging endoscopy will be practiced as a standard endoscopy technique as it is quick, safe and accurate for making a precise diagnosis of gastrointestinal pathology, with an emphasis on the diagnosis of early GI tract cancers. Further large-scale randomized controlled trials comparing these modalities in different patient subpopulations are warranted before their endorsement in the routine practice of GI endoscopy.

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.

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.

Targeted endoscopic imaging

Endoscopy has undergone explosive technological growth in recent years, and with the emergence of targeted imaging, its truly transformative power and impact on medicine lies just over the horizon. Today, our ability to see inside the digestive tract with medical endoscopy is headed toward exciting crossroads. The existing paradigm of making diagnostic decisions based on observing structural changes and identifying anatomic landmarks may soon be replaced by visualizing functional properties and imaging molecular expression. In this novel approach, the presence of intracellular and cell surface targets unique to disease are identified and used to predict the likelihood of mucosal transformation and response to therapy. This strategy could result in the development of new methods for early cancer detection, personalized therapy, and chemoprevention. This targeted approach will require further development of molecular probes and endoscopic instruments, and will need support from the US Food and Drug Administration for streamlined regulatory oversight. Overall, this molecular imaging modality promises to significantly broaden the capabilities of the gastroenterologist by providing a new approach to visualize the mucosa of the digestive tract in a manner that has never been seen before.

Palliative management of gastric cancer

Advanced gastric cancer and its palliative treatment have a long and interesting history. Today, gastric adenocarcinoma is the second leading cause of cancer death worldwide. Unfortunately, many cases are not diagnosed until late stages of disease, which underscores the importance of the palliative treatment of gastric cancer. Palliative care is best defined as the active total care of patients whose disease is not responsive to curative treatment. Although endoscopy is the most useful method for securing the diagnosis of gastric adenocarcinoma, computed tomography may be useful to assess local and distant disease. The main indication for the institution of palliative care is the presence of advanced gastric cancer for which curative treatment is deemed inappropriate. The primary goal of palliative therapy of gastric cancer patients is to improve quality, not necessarily length, of life. Four main modalities of palliative therapy for advanced gastric cancer are discussed: resection, bypass, stenting, and chemotherapy. The choice of modality depends on a variety of factors, including individual patient prognosis and goals, and should be made on case-by-case basis. Future directions include the discovery and development of serum or stool tumor markers aimed at prevention, improving prognostication and stratification, and increasing awareness and education.

Infrared fluorescence endoscopy for the diagnosis of superficial gastric tumors

BACKGROUND

Indocyanine green (ICG) is a fluorescent marker that is excited by rays at a wavelength of 768 nm to emit fluorescence at a wavelength of 807 nm in the infrared (IR) range. We developed an IR fluorescence endoscope (IRFE) to observe superficial gastric tumors and assessed its clinical usefulness.

OBJECTIVE

To evaluate the clinical usefulness of an IRFE for the assessment of superficial gastric tumors.

DESIGN

An observational study.

SETTING

University hospital.

INTERVENTIONS

Newly developed IRFE.

PATIENTS

Thirty patients with gastric tumors were enrolled in this study, and their lesions were subjected to endoscopic submucosal dissection (ESD), or laparoscopic gastrectomy after observation with the IRFE.

METHODS

Gastric lesions were subjected to conventional observation, followed by IR fluorescence observation before and after intravenous ICG (0.01 mg/kg) injection.

MAIN OUTCOME MEASUREMENTS

The relationship between the positive fluorescence and invasivity of each tumor.

RESULTS

Fluorescence was positive in 8 of 10 gastric cancers with submucosal invasion (80%) and 1 of 20 adenomas or intramucosal gastric cancers (5%); the difference was statistically significant (P<.01).

CONCLUSION

IRFE is a useful diagnostic tool for estimating the invasivity of gastric tumors.