ICG Imaging: Seeing the Body in a New Light

ICG Imaging: The Future of Seeing Inside the Body?

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Nico Varela in Health & Wellness October 2026 • 4 min read.

"Discover how near-infrared fluorescence imaging with Indocyanine Green (ICG) is revolutionizing medical diagnostics and surgery."


Imagine a world where surgeons can see blood vessels, identify tumors, and assess tissue health in real-time during operations. This isn't science fiction; it's the reality being shaped by Indocyanine Green (ICG) near-infrared fluorescence imaging. This innovative technique is changing how doctors diagnose and treat a wide range of conditions.

ICG imaging uses a special dye that emits fluorescence when exposed to near-infrared light. This allows doctors to visualize structures and processes beneath the skin's surface that would otherwise be invisible to the naked eye. The technique is safe, effective, and offers numerous advantages over traditional imaging methods.

This article delves into the exciting world of ICG imaging, exploring its applications, benefits, and potential for the future of medicine. We'll break down the science in an accessible way and show you how this technology is improving patient care.

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Clinical Use of NIR ICG Imaging

A review of human near-infrared (NIR) fluorescence imaging studies reports clinical use of six different devices. These devices employed varying doses of indocyanine green (ICG) as a nonspecific contrast agent. The source does not provide a total patient count or a comparative impact estimate.

NIR Fluorescence Imaging Methods

ICG has been used in medical imaging for over half a century, and its near-infrared spectral properties lie in the 700–900 nm window. After administration, it rapidly binds to plasma proteins, according to the supplied protocol overview. NIR imaging systems capture fluorescence; one described experimental system uses a movable platform to capture both visible light and NIR fluorescence. The supplied comparison guide describes ICG as a nonspecific blood-vascular imaging agent and says optimized system choice matters for robust, reproducible research.

From FDA Approval to Surgical Use

ICG was approved for clinical practice by the FDA more than 50 years ago. Its use has expanded with the development of minimally invasive surgery, and NIR fluorescence imaging with ICG is described as one of the emerging technologies with wide diffusion. A historical guide traces ICG’s origins to Kodak, which developed the tricarbocyanine dye during World War II for color imaging.

What is ICG Imaging and How Does It Work?

ICG Imaging: Seeing the Body in a New Light

ICG, or Indocyanine Green, is a fluorescent dye that has been approved for medical use for decades. It's unique because it emits light in the near-infrared (NIR) spectrum. When injected into the body, ICG binds to proteins in the blood, making it an excellent tool for visualizing blood vessels and tissue perfusion.

Here's a simple breakdown of how ICG imaging works:

  • ICG dye is injected into the patient's bloodstream.
  • A near-infrared light is shone onto the area of interest.
  • The ICG dye absorbs the light and emits fluorescence.
  • A special camera detects the fluorescence, creating a real-time image of the targeted area.
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Expanding ICG Applications

A review examines advances in ICG and its derivatives for NIR-II imaging and image-guided therapy, covering both fundamental and clinical perspectives while discussing challenges and future opportunities. Research into ICG NIR-light fluorescence imaging during oncologic surgery has increased, with reported roles in tumor identification and localization and lymph-node applications. A 2026 systematic review and meta-analysis synthesizes seven studies involving 230 patients on NIR-ICG fluorescence imaging for intraoperative endometriosis detection. Another study evaluates ICG-guided NIR imaging for identifying lymphatic drainage pathways.

NIR and SWIR Imaging Comparisons

A 2023 comparative study enrolled patients from March to December 2022 who received intravenous ICG at 5 mg/kg one day before planned lung-cancer surgery, then imaged nodules using NIR-I and NIR-II windows. Separately, a 2019 comparison describes shortwave infrared (SWIR) imaging as a proposed alternative to conventional NIR fluorescence, citing reduced tissue scattering and negligible autofluorescence as potential advantages. A 2018 paper characterizes ICG NIR fluorescence as promising for deep tissue penetration, low autofluorescence, weak dependence on ambient light, and safety for patients and medical staff. The supplied performance-methods paper describes a cohesive battery of tests for evaluating fluorescence image quality in wide-field imagers.

This process allows doctors to see blood flow, identify areas of inflammation, and visualize the structure of tissues and organs with greater clarity than ever before. Because NIR light penetrates deeper than visible light, ICG imaging can reveal details hidden beneath the surface.

ICG Imaging: A Brighter Future for Medicine

ICG imaging is more than just a technological advancement; it's a paradigm shift in how we approach medical diagnostics and surgery. Its ability to provide real-time visualization, improve accuracy, and enhance patient outcomes makes it an invaluable tool for doctors across various specialties.

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Evidence and Feasibility

A review of ICG-guided radical gastrectomy reports that the meta-analysis it found included six articles, two published in Chinese, but omitted eight important studies that had already been published. This highlights a limitation in the evidence synthesis described by that source. In a prospective, non-randomized, single-arm feasibility study, 70 patients with bone and soft-tissue tumors were enrolled to investigate whether intraoperative ICG fluorescence could assist with surgical-margin evaluation and guide surgery.

Quantifying Function and Extending Imaging

A prototype system reported in April 2026 combines ICG-based NIR fluorescence imaging with a quantitative framework to measure vascular structure and function simultaneously, addressing the stated lack of functional information such as blood-flow velocity and perfusion in vascular morphology imaging. The system incorporates a 785 nm laser. A study of shortwave infrared fluorescence reports real-time imaging with ICG at clinically relevant doses, including imaging of blood and lymph vessels and hepatobiliary clearance, with increased contrast compared with NIR fluorescence imaging. These reports point to research directions in quantitative vascular assessment and imaging beyond conventional NIR.

As research continues, we can expect even more innovative applications of ICG imaging to emerge, further solidifying its place as a cornerstone of modern medicine. From early cancer detection to personalized surgical approaches, the potential of ICG imaging is truly limitless.

The development and refinement of techniques like ICG imaging highlight the ongoing commitment to improving healthcare through innovation. By embracing these advancements, we can look forward to a future where medical procedures are safer, more effective, and tailored to the unique needs of each patient.

What ICG fluorescence can and cannot tell us

ICG fluorescence can be useful as a visual signal, but interpreting that signal may depend on the surgeon; the cited review notes variation between users. That makes a qualitative image less consistent as a measure of how much fluorescence is present.[1]

ICG’s brightness changes when it binds to proteins, and the amount of binding may be unknown. This complicates attempts to compare fluorescence quantitatively, even though protein binding can also increase the signal.[2]

Why reported ICG results can differ

For sentinel lymph-node biopsy, the sources identify variation in node definitions, protocols, equipment, doses, and techniques as obstacles to drawing reliable conclusions across meta-analyses. A separate gastric-cancer assessment also cautions that its sensitivity was not optimal and that the evidence should be viewed cautiously because the studies were heterogeneous.[3] [4]

ICG-guided lymphadenectomy may help with lymph-node harvest during oesophageal and gastric cancer surgery, but the source says its oncological benefits may be limited and warns that relying on it alone risks missing metastatic nodes. This is a different question from whether fluorescence helps locate a node: locating structures does not by itself establish that all clinically important disease is found.[5]

The evidence base also has a possible publication-bias signal: an analysis of gastric-cancer sentinel-node studies found an asymmetrical diagnostic-odds-ratio funnel plot. That finding raises uncertainty about how representative the published results may be, rather than showing that ICG itself performs uniformly well or poorly.[6]

What remains unresolved about ICG imaging

  • How reproducible are fluorescence-based judgments across surgeons, given the reported user-to-user variation in interpreting signals?[1]
  • How can quantitative comparisons account for protein binding when its extent is unknown and it changes ICG’s quantum yield?[2]
  • In lymph-node procedures, how much do differing definitions, equipment, and protocols account for the variation in reported performance?[3] [4]

Sources

  1. Quantification of Indocyanine Green Fluorescence Imaging in General, Visceral and Transplant Surgery (pmc.ncbi.nlm.nih.gov)
  2. Fluorescent Tracers for In Vivo Imaging of Lymphatic Targets (pmc.ncbi.nlm.nih.gov)
  3. Indocyanine green versus technetium-99m for sentinel lymph node biopsy in breast cancer: the FLUORO trial (pmc.ncbi.nlm.nih.gov)
  4. Diagnostic evaluation of sentinel lymph node biopsy using indocyanine green and infrared or fluorescent imaging in gastric cancer: a systematic review and meta-analysis. (pubmed.ncbi.nlm.nih.gov)
  5. The use of indocyanine green and near-infrared fluorescence in the detection of metastatic lymph nodes during oesophageal and gastric cancer resection: a systematic review and meta-analysis (link.springer.com)
  6. Application value of indocyanine green fluorescence imaging in guiding sentinel lymph node biopsy diagnosis of gastric cancer: Meta-analysis (pmc.ncbi.nlm.nih.gov)

About this Article -

Written with AI assistance from published research, and reviewed by the Mystum team. See our About page for more information.

Everything You Need To Know

1

What exactly is ICG Imaging?

ICG Imaging, also known as Indocyanine Green imaging, is a medical imaging technique that uses a special fluorescent dye called Indocyanine Green (ICG). This dye is injected into the patient's bloodstream and emits fluorescence when exposed to near-infrared (NIR) light. A special camera then detects this fluorescence, creating a real-time image of the targeted area within the body.

2

Why is ICG Imaging important?

The significance of ICG Imaging lies in its ability to visualize structures and processes beneath the skin's surface that are otherwise invisible. This is particularly important because it allows doctors to see blood vessels, identify tumors, and assess tissue health in real-time during operations. The use of Near-infrared (NIR) light further enhances this capability, as it penetrates deeper into tissues than visible light. Improved visualization leads to more accurate diagnoses and surgical procedures.

3

What are the benefits of ICG Imaging?

The main advantage of ICG Imaging is its improved diagnostic capabilities. It provides real-time visualization of blood flow, tissue perfusion, and the structure of tissues and organs. This helps in identifying areas of inflammation, tumors, and other abnormalities with greater clarity and precision. This leads to more effective treatments and better patient outcomes. Compared to traditional methods, it provides a more detailed view without the need for invasive procedures in many cases.

4

In what areas of medicine is ICG Imaging used?

ICG Imaging is used in a variety of medical fields. Surgeons use it to guide procedures, such as identifying the boundaries of tumors, assessing the health of blood vessels, and ensuring proper tissue perfusion. It's also used in diagnostics to assess blood flow, detect inflammation, and identify various conditions that would otherwise be difficult to visualize. It is a versatile tool that can be tailored to different areas of the body.

5

What does the future hold for ICG Imaging?

The future of ICG Imaging is promising. The technique is constantly evolving, with advancements in imaging technology and the development of new applications. As technology advances, it is expected to become even more precise and versatile. The improved accuracy and enhanced patient outcomes are expected to become more prominent, making it an invaluable tool for doctors across various specialties. The potential for minimally invasive procedures is also a key benefit.

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