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Asked Questions

Fluorescence Guided Surgery
Frequently Asked Questions

We’ve put together some commonly asked questions about Fluorescence Guided Surgery.
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Fluorescence Guided Surgery (FGS) is a medical imaging technique that uses fluorescent dye to identify anatomic structures during surgical procedures.  Fluorescence Guided Surgery (FGS) typically involves the use of a Fluorescent Dye, and a special camera system to visualize the fluorescence. The most commonly used fluorescent agent is Indocyanine Green (ICG). ICG was approved by the US FDA in 1959, has an excellent safety profile and can be used in a variety of surgical applications.

Surgery is among one of the most common treatments prescribed for acute and chronic diseases with as many as 40 million surgeries performed annually in the United States alone. Much of human surgery is performed without any image guidance where the surgeon has only direct visualizationas as their guide. Fluorescence Guided Surgery (FGS), (also called ‘Fluorescence image-guided surgery’) is a medical imaging technique used to detect fluorescently labelled structures during surgery and provide real time assessment of blood flow to these structures. FGS guides the surgical procedure and provides the surgeon with real time visualization of their operating field.

Fluorescence is a phenomenon of light emission with a certain wavelength from a material when it is irradiated by light with another wavelength. The irradiated and emitted lights are called “Excitation Light” and “Fluorescence Light” respectively. The material is called a “Fluorescent Substance” or “fluorophore”.

Despite many advances in preoperative medical imaging such as CT and MRI scans, surgeons still almost exclusively operate under white (visible) light during their procedures and must rely on their ability to see and feel target tissues. Unfortunately, most human tissue looks very similar under white light, and it can be very difficult to distinguish one tissue from another or to completely remove a target tissue such as a tumor. In addition, a surgeon can only see the uppermost layer of tissue under white light while tissues and structures underneath will remain hidden.


Fluorescence Guided Surgery (FGS) essentially gives the surgeons the ability to ‘see’ these invisible structures by using a different wavelength of light. By combining this visual ability with the special dyes that fluoresce in those wavelengths, surgeons can much more precisely target or avoid certain organs or tissues. In addition, the near-infrared light used in FGS can more easily penetrate human tissues, allowing surgeons to see ‘through’ layers of tissue and organs. FGS has the added advantage of being a real-time imaging process. Whereas traditional imaging like X-Rays, CT Scans, and MRI scans can provide excellent images, they are all limited to providing static images.

The most used fluorescent marker is Indocyanine Green (ICG). ICG is a tricarbocyanine dye with both hydrophilic and lipophilic properties. Developed in the 1950s, Indocyanine Green (ICG) is a water-soluble fluorescent molecule with a proven safety profile that binds to plasma proteins. ICG is used as a marker in the assessment of vascular perfusion (or blood flow) to the tissues and organs in many areas of medicine. The light required to trigger fluorescence is generated by a near-infrared light source attached to a camera, which tracks and documents both absorption and fluorescence in real time.

Yes, Indocyanine Green, ICG is available in many territories worldwide. Marketed in many territories in Europe under the name Verdye and in the USA by the name Indocyanine Green, for Injection, USP, it is sold internationally by Diagnostic Green.  Diagnostic Green is the leading provider of trusted high quality Indocyanine Green (ICG) for physicians worldwide.

Indocyanine Green (ICG) is intended for intravenous injection (I.V.) via an injection needle, a central or peripheral catheter or cardiac catheter. Following I.V. administration, ICG is rapidly bound to plasma proteins, of which beta-apolipoprotein B is the principle carrier (95%) and remains in the blood vessels.  ICG is cleared exclusively through the liver, and then eliminated through the bile. It does not undergo metabolism.

Indocyanine Green (ICG), has been used for more 50 years for fluorescence angiography purposes in various medical fields (ophthalmology, microsurgery). As it is exclusively removed by the liver, it is also used for liver function testing. Half-life after injection into blood is three-four minutes, is rapidly bound to plasma protein and undergoes no significant extrahepatic or enterohepatic circulation. Diagnostic procedures with ICG should be performed under the supervision of a physician.

Both the excitation and fluorescent lights are in the near-infrared region where light absorption by hemoglobin (and water) is small, so the light can travel long distances in the human body.  ICG can be excited and emits fluorescence which can be visualized by appropriate camera systems approved worldwide.

Live images from the fluorescent dye and the surgical field are obtained using a combination of filters, lenses and cameras. During open surgery, hand-held devices are usually preferred for their ease of use and mobility. Examples of hand-held systems include IC-Flow, PDE Neo and Fluobeam. Fluorescence Guided Surgery, FGS can also be performed using minimally invasive devices such as laparoscopes or endoscopes. In this case, a system of filters, lenses and cameras is attached to the end of the probe.  Examples of endoscopic camera systems include Visera Elite, EleVision and Rubina™. Fluorescence Guided Surgery (FGS) devices can also be implemented for robotic surgery (for example in the da Vinci Surgical System).

“Intraoperative fluorescence imaging offers the benefits of low cost, ease of use, no reliance upon damaging ionizing radiation and enhanced safety through visualization,” said Michael Bouvet, MD, center Co-director and former president of the International Society of Fluorescence Guided Surgery.


“The use of fluorescence is an absolute game-changer for cancer surgeries,” Dr Ann M Wallace, Director of the Comprehensive Breast Health Center at UC San Diego Health.