Fluorescent Imaging with Indocyanine Green: Experience with the Russian «MARS» System in Open Surgery

Fluorescent imaging with indocyanine green (ICG) has long been established among medical specialists across various fields as a safe and highly accurate diagnostic tool. Over the 60 years since its discovery, numerous scientific publications worldwide have attested to its efficacy. Initially adopted in ophthalmology for diagnosing vascular pathologies of the eye, ICG navigation has since expanded into diverse medical disciplines, including neurosurgery, abdominal surgery, oncological breast and gynecological surgery, cardiac surgery, endocrinology, vascular surgery, and many others. Specific applications will be explored in detail further on.

The adoption of fluorescent imaging in Russian clinical practice began relatively recently, no more than 20 years ago. Initially, the methodology relied on imported agents and equipment capable of registering fluorescence and visualizing blood or lymph flow in real time. The advent of domestically produced agents and systems, like the «MARS» system, has significantly increased the accessibility of this technology for Russian healthcare institutions. In many oncology departments and centers, ICG navigation is not merely an alternative to the radioisotope method but has, in some cases, become the primary tool for identifying sentinel lymph nodes during biopsy procedures. In certain specialties, ICG technology is already included in clinical guidelines and is classified as a high-tech diagnostic method. This underscores the need to elaborate on the principle of ICG action for diagnostic and intraoperative analysis of blood flow, lymph flow, and tissue perfusion.

The Principle of ICG Navigation

The principle involves the intravenous or intradermal administration of the contrast agent, indocyanine green. The agent binds to blood or lymph proteins and begins to fluoresce. A specialized device, featuring a laser light source and an infrared camera with an interference filter, detects this fluorescence and displays the image on a monitor. Thus, during surgery or a diagnostic procedure, the physician directs the optical unit to the area of interest and receives a real-time depiction of blood or lymph flow. It is important to note that the penetration depth of the laser excitation is limited to approximately 1.1 cm; however, this is greater than that achievable with lasers of other wavelengths (e.g., ultraviolet, blue, green). ICG itself has a broad absorption spectrum (600-900 nm) and emits fluorescence between 750-950 nm. Medical equipment utilizes ICG's peak absorption in blood plasma at around 800 nm. Consequently, lasers with a wavelength of about 780 nm are typically used for optimal fluorescence detection after filtering out scattered excitation light.

This article provides examples of ICG technology application in traditional open surgeries, though it is also widely used in laparoscopic procedures. Below are the key open-surgery applications:

1) Sentinel Lymph Node (SLN) Biopsy in Breast Cancer, Melanoma, and Cervical Cancer Mapping lymphatic vessels and detecting sentinel nodes often allows for a reduction in the extent of surgery, avoiding full lymphadenectomy. This helps patients avoid postoperative complications like lymphedema. ICG technology is a safe and equally effective alternative to the radioisotope method, which requires preoperative administration of a radiotracer and the use of a gamma detector. Fluorescent imaging requires no special patient preparation, and the hospital needs no dedicated radioisotope laboratory.

2) Lymphovenous Anastomosis (LVA) LVA is a microsurgical procedure to create a drainage pathway for lymph fluid by directly connecting a lymphatic vessel to a subcutaneous vein, often to relieve limb edema in patients post-lymphadenectomy or mastectomy. Fluorescent imaging is used initially to detect lymphatic vessels and finally to assess the quality of the completed anastomosis. This highly complex procedure is performed under a surgical microscope by qualified surgeons. Experts see significant scientific potential for this technology in the surgical treatment of lymphedema.

3) Detection and Viability Assessment of Parathyroid Glands during Thyroidectomy Preserving the parathyroid glands during thyroid tumor removal is crucial to prevent hypoparathyroidism, as these glands regulate calcium and phosphate homeostasis via parathyroid hormone (PTH) secretion. While fluorescent imaging is a well-established method for visualizing these glands, visual differentiation from adipose tissue or lymph nodes can be challenging. The quantitative assessment of fluorescence intensity, a feature of the «MARS» software, has significantly reduced false-positive results.

4) Organ and Tissue Transplantation

4.1 Kidney Transplantation: Fluorescent imaging is a safe and sensitive method for the intraoperative assessment of renal allograft perfusion, revealing deficits invisible to the naked eye. It also provides an objective assessment of ureteral blood supply to determine the resection margin, helping to avoid postoperative urological complications.

4.2 Liver Transplantation: ICG fluorescence is applied at various stages of transplantation. It is used preoperatively to assess graft function, intraoperatively to visualize organ structure, locate tumors, assess liver function, and guide the surgical site, thereby reducing time and improving efficiency. It also helps predict postoperative complication risks.

4.3 Skin Flap Transplantation: ICG visualization allows for qualitative assessment of tissue perfusion, overcoming the subjectivity of current methods (e.g., skin color, swelling, turgor). Near-infrared videofluorescence assesses soft tissue viability and perfusion in plastic and reconstructive surgeries (e.g., free flap transfer, breast reconstruction), minimizing the risks of marginal necrosis.

5) Abdominal Surgery A primary application in abdominal surgery is defining resection margins and assessing perfusion in colonic anastomoses. IV-administered ICG visualizes the vascular network of the intestinal area of interest within a minute. Quantitative fluorescence intensity metrics allow surgeons to accurately distinguish perfused from non-viable tissue, choose the correct resection line, and assess the blood supply of the newly formed anastomosis.

6) Coronary Artery Bypass Grafting (CABG) After bypass graft placement, ICG is injected IV to visualize blood flow through the newly placed shunt. The resulting visualization of superficial vessels (up to ~1 cm deep) allows the surgeon to verify the procedure's quality intraoperatively and make immediate adjustments if necessary. The quality of the bypass can also be quantified.

7) Diabetic Foot Units The goal of ICG imaging here is to assess soft tissue perfusion in the foot in cases of lower limb ischemia. Beyond visual assessment, quantitative fluorescence parameters help provide an objective picture of the patient's arterial status, complementing methods like Doppler ultrasound or CT angiography. This aids specialists in determining the need for surgical revascularization.

Conclusion

The key advantages of ICG technology in open surgery are multifold. Firstly, ICG itself is a safe agent, excreted unchanged by the liver. Secondly, the technology requires minimal preparation, allowing for prompt use. Unlike radioisotope methods, it requires no special licensing for room use. Its broad application spectrum and the long lifespan of system components (cameras, laser) are significant benefits. Advantages of the domestic «MARS» system over some analogues include a hands-free optical unit that can be fixed in position (freeing the surgeon's hands) and no need for complete operating room darkness. Furthermore, it offers high-quality imaging and excellent software functionality. In summary, ICG fluorescent imaging is a reliable visualization tool for surgeons with numerous promising applications.

Author: Sergey G. Kuzmenko, Product Manager for «MARS»

You can learn more about this device on the Kriptomed company website.