Frequently
Asked Questions

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
visualizations 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. Fluorescence Guided Surgery (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, Indocycanine Green (ICG) is a water-soluble
fluorescent molecule with a proven safety profile that binds to plasma
proteins.

Indocyanine Green (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 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. 
Indocyanine Green (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. Fluoresence 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 System Green, 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.

There are several possible reasons why ICG fluorescence may not be visible. Below are common issues and solutions:

1. Incorrect Imaging System Settings

• Issue: The fluorescence imaging system may not be set to the correct mode.
• Solution: Ensure that the system is in the correct NIR (near-infrared) fluorescence mode and that the excitation light source is turned on. Adjust brightness, contrast, and gain settings as needed.

2. Incorrect ICG Administration

• Issue: The ICG may not have been prepared or administered correctly.
• Solution:
  • Confirm that the ICG was properly diluted according to information leaflet instructions.
  • Ensure it was injected at the appropriate dose and timing.
  • Allow sufficient circulation time (typically 30-60 seconds for perfusion studies and up to a few minutes for lymphatic mapping).

3. Poor Blood Circulation or Incorrect Timing

• Issue: The ICG may not have reached the target area due to inadequate perfusion or timing issues.
• Solution:
  • Verify that the patient’s circulation is adequate (e.g., check blood pressure and perfusion status).
  • Wait a few minutes and reattempt imaging if necessary.

4. Low ICG Concentration or Degradation

• Issue: The ICG concentration may be too low, or the dye may have degraded.
• Solution:
  • Check the expiration date of the ICG solution.
  • Ensure the solution was stored correctly (protected from light and mixed just before use).
  • Consider re-dosing if the initial administration was insufficient.

5. Interference from External Light Sources

• Issue: Ambient light may be interfering with fluorescence detection.
• Solution:
  • Dim or turn off bright operating room lights that may interfere with NIR detection.
  • Ensure there is no obstruction between the excitation light and the tissue.

6. Equipment Malfunction

• Issue: The imaging system may not be functioning properly.
• Solution:
  • Check for proper connection and calibration of the imaging device.
  • Restart the system if needed.
  • Verify that the excitation and emission filters are correctly installed.

7. Tissue Depth and Absorption Issues

• Issue: Fluorescence may be blocked by excessive tissue depth or pigmentation.
• Solution:
  • Be aware that ICG fluorescence is best detected within a few millimetres of tissue depth.
  • Try adjusting the angle and distance of the imaging system.

Still Having Issues?

If none of these solutions resolve the problem, please reach out to info@diagnosticgreen.com  for further technical support and guidance.