Fluorescence-Guided Surgery: From Indocyanine Green to Tumor-Specific Fluorophores in 2026

Understanding Fluorescence-Guided Surgery

Principles of fluorescence-guided surgery

Fluorescence-guided surgery is an intraoperative imaging modality that enables visualization of fluorescently labeled tissues during surgical procedures. Fluorescent contrast agents are administered systemically, topically, or locally and accumulate within specific tissues, including tumors, lymphatic structures, vascular networks, or nerves. When illuminated with excitation light of a defined wavelength, these agents emit fluorescence that is captured by dedicated imaging systems and displayed in real time.

Unlike conventional image-guided surgery that depends primarily on preoperative CT, MRI, or PET imaging, fluorescence-guided surgery provides dynamic intraoperative feedback during active tissue dissection. Specialized cameras overlay fluorescence signals onto white-light surgical images, allowing surgeons to distinguish target tissues that would otherwise appear indistinguishable under standard illumination.

This capability extends the surgeon’s visual perception beyond traditional white-light reflectance. Conventional surgical visualization is inherently limited because most tissues appear within a narrow spectrum of red and pink hues. Fluorescence imaging introduces molecular contrast that improves differentiation between normal tissue, ischemic tissue, malignant lesions, and critical anatomical structures.

Compared with many other imaging modalities, fluorescence imaging offers high spatial resolution, real-time feedback, relatively low operational costs, and molecular specificity. However, optical penetration depth remains limited. Visible wavelength fluorophores typically penetrate only several hundred micrometers, whereas near-infrared (NIR) fluorophores may achieve penetration depths approaching 1–2 cm because of reduced tissue absorption and scattering within the NIR optical window.

Mechanism of fluorescent contrast agents

Fluorescent contrast agents operate through photophysical excitation and emission processes. Following excitation by light of a specific wavelength, fluorophores absorb energy and subsequently emit light at a longer wavelength. The emitted fluorescence is detected by imaging sensors and converted into visual signals for surgical guidance.

Near-infrared fluorophores are particularly valuable because biological tissues exhibit minimal absorption and autofluorescence within the 700–900 nm wavelength range. This “optical window” permits deeper tissue penetration and improved signal-to-noise ratios.

Indocyanine green exemplifies the most extensively utilized fluorophore in surgical imaging. ICG absorbs light around 800 nm and emits fluorescence near 830 nm. After intravenous administration, the dye binds extensively to plasma proteins, particularly albumin, and circulates rapidly through the vascular system.

Modern fluorescent probes increasingly incorporate molecular targeting strategies. These agents bind selectively to tumor-associated receptors, enzymes, or metabolic pathways, enabling enhanced specificity for malignant tissue. Molecularly targeted fluorophores improve intraoperative discrimination between cancerous and healthy tissue and may facilitate detection of microscopic disease deposits that are otherwise undetectable.

Clinical need for enhanced intraoperative visualization

Traditional surgery relies heavily on visual inspection and tactile feedback. Although effective in many settings, these methods are often insufficient for identifying microscopic disease, defining tumor margins, or distinguishing viable from ischemic tissue.

Incomplete tumor resection remains a major challenge across multiple cancer types. Positive surgical margins are associated with local recurrence, repeat surgery, adjuvant therapy escalation, and reduced survival outcomes. Intraoperative fluorescence imaging addresses this limitation by providing real-time molecular information during resection.

Fluorescence imaging also supports identification of critical structures such as lymphatics, bile ducts, ureters, and peripheral nerves. Improved visualization reduces inadvertent injury and may decrease postoperative complications including chronic pain, functional deficits, and anastomotic failure.

Unlike static preoperative imaging, fluorescence-guided surgery provides dynamic intraoperative assessment of tissue perfusion, residual disease, and anatomical boundaries throughout the procedure.

Indocyanine Green: The Current Clinical Standard

Properties and pharmacology of ICG

Indocyanine green received FDA approval in 1959 for cardiovascular and hepatic diagnostic applications and has since become the dominant fluorophore in clinical fluorescence imaging.

ICG is a water-soluble tricarbocyanine dye with a molecular weight of 774.96 g/mol and a short plasma half-life of approximately 2.5–4 minutes. Following intravenous injection, nearly all circulating ICG binds to plasma proteins, limiting diffusion into the interstitial space. Hepatic clearance occurs rapidly through biliary excretion without significant metabolism.

The near-infrared optical characteristics of ICG provide several important advantages:

• Reduced tissue scattering
• Greater penetration depth
• Lower tissue autofluorescence
• Improved visualization beneath tissue surfaces

ICG demonstrates an excellent safety profile with a very low incidence of severe adverse reactions. Although hypersensitivity reactions are uncommon, caution remains necessary in patients with iodine-related allergies because sodium iodide is present during formulation.

The widespread availability of compatible NIR imaging systems has contributed significantly to ICG adoption. Most contemporary laparoscopic and robotic surgical platforms now include fluorescence imaging capabilities integrated directly into operative consoles.

Clinical applications of ICG

Perfusion assessment

Perfusion imaging represents one of the most established applications of ICG fluorescence imaging. In gastrointestinal surgery, fluorescence angiography allows surgeons to evaluate bowel vascularization before anastomosis creation.

Several studies have demonstrated that intraoperative perfusion assessment may reduce anastomotic leak rates by identifying poorly perfused tissue segments requiring revision. Similar applications exist in reconstructive surgery, where ICG angiography assists in evaluating flap viability and predicting tissue necrosis.

Sentinel lymph node mapping

ICG is widely used for sentinel lymph node identification in breast, gastric, gynecologic, and colorectal malignancies. The technique enables visualization of lymphatic drainage pathways in real time.

Meta-analyses in breast cancer have reported high sentinel node detection rates with low false-negative rates. In gastric cancer surgery, ICG-guided lymphography has improved lymph node retrieval and facilitated more comprehensive nodal dissection.

Hepatobiliary imaging

ICG is particularly valuable in hepatic surgery because of its hepatobiliary clearance mechanism. Administration before surgery permits visualization of liver tumors and biliary anatomy.

Malignant hepatic lesions may exhibit characteristic fluorescence patterns, including peripheral rim enhancement caused by impaired hepatocyte uptake and altered biliary excretion. Combining ICG imaging with intraoperative ultrasonography improves detection sensitivity for hepatic metastases and hepatocellular carcinoma.

Additional applications

Other applications of ICG fluorescence imaging include:

• Identification of ureters during pelvic surgery
• Assessment of tissue perfusion in vascular surgery
• Visualization of biliary anatomy during cholecystectomy
• Evaluation of lymphatic drainage in lymphedema surgery
• Guidance during thoracic and transplant procedures

Limitations of ICG

Despite its widespread use, ICG possesses important limitations.

The dye lacks intrinsic tumor specificity and accumulates primarily through passive mechanisms such as the enhanced permeability and retention effect. Consequently, fluorescence signals may occur in inflammatory tissue, benign lesions, or nonmalignant vascular structures, reducing specificity.

False-positive fluorescence remains a recognized limitation in hepatic imaging and lymph node mapping. ICG also cannot reliably distinguish metastatic from nonmetastatic lymph nodes.

Additional limitations include:

• Limited tissue penetration depth
• Photobleaching and signal degradation
• Non-specific background fluorescence
• Variable tumor accumulation across malignancies
• Reduced utility in deeply seated tumors

These shortcomings have driven the development of tumor-specific fluorophores designed to bind selectively to malignant cells.

FDA-Approved Fluorescent Agents Beyond ICG

5-Aminolevulinic acid in glioma surgery

5-Aminolevulinic acid (5-ALA) became the first FDA-approved optical imaging agent for glioma surgery in 2017. Administered orally before surgery, 5-ALA enters the heme biosynthesis pathway and is metabolized intracellularly into protoporphyrin IX (PpIX).

Malignant glioma cells accumulate PpIX because of altered metabolic activity and reduced ferrochelatase function. Under blue-violet excitation light, PpIX emits bright red fluorescence that delineates tumor tissue.

Clinical trials have demonstrated that 5-ALA-guided resection improves rates of complete tumor removal in high-grade gliomas compared with conventional microsurgery. Enhanced extent of resection has also been associated with improved progression-free survival and overall survival outcomes.

However, fluorescence intensity is considerably lower in low-grade gliomas, and false-positive fluorescence may occur in regions of inflammation, gliosis, or radiation-related tissue injury.

Fluorescein sodium

Fluorescein sodium accumulates in regions where blood-brain barrier integrity is disrupted. Under dedicated microscope filters, malignant tissue appears yellow-green relative to surrounding brain parenchyma.

The agent has demonstrated utility in glioblastoma surgery, where fluorescence-guided resection improves visualization of contrast-enhancing tumor regions. Fluorescein is comparatively inexpensive and widely accessible, making it attractive in resource-limited settings.

Adverse effects are generally mild and transient, commonly including temporary yellow discoloration of skin and urine.

Methylene blue

Methylene blue serves primarily as a tracer for sentinel lymph node mapping. The dye remains widely used because of its affordability, ease of administration, and broad availability.

Applications include breast cancer, colorectal cancer, and selected gynecologic procedures. Identification rates vary across studies, and performance is generally inferior to combined radiotracer and fluorescence techniques. Nevertheless, methylene blue remains clinically important in regions lacking nuclear medicine infrastructure.

Pafolacianine (Cytalux)

Pafolacianine represents a major advancement in tumor-specific fluorescence imaging. The fluorophore targets folate receptor alpha, which is overexpressed in many ovarian and pulmonary adenocarcinomas.

FDA approval was granted for ovarian cancer in 2021 and for lung cancer in 2022. Clinical trials demonstrated that pafolacianine can identify additional malignant lesions not detected under white-light visualization alone.

The ELUCIDATE trial further showed that molecular imaging altered operative decision-making in a substantial proportion of thoracic surgical procedures.

Transition Toward Tumor-Specific Fluorophores

Limitations of non-specific fluorophores

Traditional fluorophores such as ICG rely largely on passive accumulation mechanisms. Although effective for perfusion imaging and lymphatic mapping, these agents often lack sufficient specificity for precise oncologic surgery.

Tumor heterogeneity further complicates imaging because receptor expression varies between cancer types and among patients with the same malignancy. Passive fluorophores may therefore demonstrate inconsistent sensitivity and specificity.

These limitations have accelerated development of molecularly targeted probes capable of binding directly to tumor-associated biomarkers.

Folate receptor-targeted probes

Folate receptor alpha is overexpressed in multiple malignancies, particularly ovarian and endometrial cancers. Folate-targeted probes exploit the high affinity between folic acid and folate receptors to achieve selective tumor localization.

Experimental near-infrared folate probes have demonstrated excellent tumor-to-background ratios in preclinical models. Early clinical investigations suggest potential utility for intraoperative detection of occult disease.

Antibody-conjugated fluorophores

Antibody-fluorophore conjugates combine the specificity of monoclonal antibodies with optical imaging capabilities.

Cetuximab-IRDye800CW targets epidermal growth factor receptor (EGFR), which is highly expressed in head and neck squamous cell carcinoma and several other malignancies. Clinical studies have demonstrated high sensitivity for tumor-positive margin detection and metastatic lymph node identification.

Panitumumab-based probes and additional antibody fragment constructs are also undergoing clinical development.

EGFR-targeted imaging

EGFR-targeted fluorophores have shown promise in oral, lung, and gastrointestinal cancers. Fluorescence imaging using EGFR-specific probes improves delineation of tumor margins and identification of metastatic disease.

Fragment-based constructs may offer faster pharmacokinetics and lower background signal compared with full monoclonal antibodies.

Activatable Fluorescent Probes

Principles of activatable imaging

Activatable fluorescent probes remain optically quenched until interacting with tumor-associated molecular triggers such as enzymes, pH changes, or intracellular transport pathways.

Unlike conventional “always-on” fluorophores, activatable probes emit fluorescence only after molecular activation, thereby significantly improving tumor-to-background contrast.

These probes generally fall into two major categories:

• Enzyme-activated probes
• Receptor-mediated internalization probes

Multiple quenching mechanisms have been developed, including Förster resonance energy transfer, photon-induced electron transfer, spirocyclization, and aggregation-induced quenching.

Enzyme-responsive probes

Many tumors overexpress enzymes such as:

• Cathepsins
• Matrix metalloproteinases
• β-galactosidase
• γ-glutamyltransferase

Enzyme-activated probes remain dark until cleaved by these enzymes within the tumor microenvironment. Activation generates highly localized fluorescence while minimizing background signal.

Several cathepsin-activated probes have demonstrated high tumor-to-background ratios in preclinical studies, including improved visualization of microscopic lesions.

pH-sensitive probes

Tumor microenvironments exhibit extracellular acidosis because of altered cancer metabolism and hypoxia. pH-sensitive fluorophores exploit this characteristic by activating selectively under acidic conditions.

Near-infrared aza-BODIPY probes with tunable pKa values have demonstrated the ability to identify submillimeter metastatic lesions following topical administration.

Advantages over conventional fluorophores

Activatable probes provide several important advantages:

• Higher tumor-to-background ratios
• Reduced background fluorescence
• Improved detection of microscopic disease
• Lower required doses
• Faster imaging kinetics
• Greater molecular specificity

These characteristics may ultimately enable more accurate identification of occult metastases and residual tumor tissue during surgery.

Fluorescence-Guided Surgery Systems Market in 2026

Major imaging system manufacturers

The fluorescence-guided surgery systems market continues to expand rapidly. Major manufacturers include:

• Stryker
• Medtronic
• Intuitive Surgical
• KARL STORZ
• Olympus Corporation

Many platforms integrate fluorescence imaging directly into robotic and laparoscopic systems. Robotic consoles increasingly permit seamless switching between white-light and fluorescence modes without interrupting workflow.

Stryker’s SPY imaging systems and Intuitive Surgical’s Firefly platform remain among the most widely adopted fluorescence imaging technologies. Integration into minimally invasive surgery has been a major driver of adoption.

Market growth

The global fluorescence-guided surgery systems market is projected to continue growing at a double-digit compound annual growth rate over the coming decade. Growth drivers include:

• Increased cancer surgery volume
• Expansion of robotic surgery
• Greater availability of tumor-specific fluorophores
• Improved imaging hardware
• Broader clinical awareness

North America currently accounts for the largest market share because of advanced healthcare infrastructure and favorable technology adoption patterns.

International Society for Fluorescence Guided Surgery

The International Society for Fluorescence Guided Surgery promotes global advancement of fluorescence imaging through education, research collaboration, and clinical standardization.

The organization hosts scientific meetings, workshops, and international training programs focused on fluorescence-guided surgical techniques and translational research.

Emerging Applications in Fluorescence-Guided Surgery

Nerve-sparing surgery

Novel nerve-specific fluorophores are being developed to improve identification of peripheral nerves during surgery. Intraoperative nerve injury remains a major source of postoperative morbidity.

Near-infrared oxazine derivatives and peptide-based tracers have demonstrated promising nerve-to-background contrast in preclinical and early clinical studies. These technologies may improve nerve preservation during robotic pelvic surgery, endocrine surgery, and reconstructive procedures.

Real-time margin assessment

Fluorescence imaging increasingly supports intraoperative margin assessment. Tumor-specific fluorophores can identify residual disease within the operative bed or resected specimens before closure.

Cetuximab-IRDye800CW has demonstrated high sensitivity for identifying tumor-positive margins in oral squamous cell carcinoma. Ex vivo fluorescence assessment may reduce reoperation rates and improve oncologic outcomes.

Detection of microscopic metastases

One of the most promising applications of fluorescence-guided surgery involves identification of occult metastatic disease. Fluorescence imaging can reveal small metastatic implants undetectable by white-light visualization or palpation.

Clinical studies using pafolacianine and ICG have demonstrated improved detection of metastatic lesions during ovarian, hepatic, and thoracic oncologic surgery.

Reconstructive and vascular surgery

ICG angiography is increasingly utilized in reconstructive surgery to assess flap perfusion and predict ischemic complications. Vascular surgeons similarly employ fluorescence imaging to evaluate graft perfusion and tissue viability intraoperatively.

Challenges and Future Directions

Cost and accessibility

High capital costs remain a major barrier to adoption. Fluorescence imaging systems may cost between USD 80,000 and USD 250,000 depending on configuration, while service contracts and maintenance costs add additional financial burden.

Smaller hospitals and ambulatory surgical centers may face difficulty implementing fluorescence-guided technologies despite potential long-term clinical benefits.

Tumor heterogeneity

Tumor-specific fluorophores depend on biomarker expression, which varies substantially across patients and tumor subtypes. Single-target imaging agents may therefore fail to identify all malignant tissue within heterogeneous tumors.

Current research increasingly focuses on multiplexed imaging strategies and combinations of targeted fluorophores capable of recognizing multiple tumor biomarkers simultaneously.

Integration with robotic surgery

The convergence of fluorescence imaging and robotic surgery represents one of the most important developments in modern operative oncology. Integrated robotic systems allow real-time fluorescence overlay without interrupting operative flow.

Minimally invasive approaches particularly benefit from fluorescence imaging because confined operative spaces limit tactile feedback and direct visualization.

Regulatory complexity

Development of novel fluorophores remains challenging because imaging agents must satisfy stringent safety, pharmacokinetic, and manufacturing requirements. Approval pathways for targeted fluorophores are often substantially longer than those for imaging hardware.

Standardization of imaging protocols, dosing regimens, calibration methods, and fluorescence quantification remains necessary to improve reproducibility across institutions and clinical trials.

FAQs

Q1. What alternatives exist to indocyanine green for fluorescence-guided surgery?

Alternatives to ICG include fluorescein sodium, 5-ALA, methylene blue, and tumor-specific fluorophores such as pafolacianine. These agents differ in mechanism, wavelength characteristics, tissue specificity, and clinical applications.

Q2. How large is the fluorescence-guided surgery systems market in 2026?

The fluorescence-guided surgery systems market is projected to exceed USD 140 million in 2026, with continued growth driven by robotic surgery integration, expanding oncologic applications, and development of targeted imaging agents.

Q3. Why is ICG administered before gastrointestinal surgery?

ICG is administered to assess tissue perfusion, vascular integrity, and anastomotic viability in real time. In hepatobiliary surgery, preoperative administration may also facilitate visualization of liver tumors and biliary anatomy.

Q4. Which fluorescent agents are currently used in surgical imaging?

Commonly used fluorescent agents include ICG, fluorescein sodium, 5-ALA, methylene blue, and pafolacianine. Additional targeted probes and activatable fluorophores are undergoing clinical evaluation.

Q5. What advantages do tumor-specific fluorophores provide?

Tumor-specific fluorophores improve molecular selectivity by binding directly to cancer-associated biomarkers. Compared with non-specific dyes, they generally provide higher sensitivity, improved specificity, reduced background signal, and enhanced detection of microscopic disease.

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