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Emerging Insights On The Diagnostic Benefits Of Fluorescence Imaging In Wound Care

We are in an age when we have a handheld device that can give us real-time information whether a wound has bacteria that is preventing healing.

Fluorescence imaging is the visualization of fluorescent dyes or proteins as labels for molecular processes or structures. The imaging enables a wide range of experimental observations including gene expression, protein expression and molecular interactions in cells and tissues.

Mostly, fluorescence imaging has been in use in the laboratory setting. In the past five to 10 years, I have seen several modalities that employ the use of fluorescence imaging at the bedside or clinic setting. 

The SPY Elite Fluorescence Imaging System (Novadaq) is one that comes to mind. This product makes use of intravenously injected indocyanine green (ICG), which binds to plasma proteins and then persists in the vasculature. The laser light source illuminates the surgical field with white light and low intensity, invisible, infrared light, causing the ICG to fluoresce. The camera system detects the fluorescent ICG as it passes through the arterial, capillary and venous phases of perfusion. 

Surgery with molecular fluorescence imaging decreases the risk of residual cancer and improves survival.1,2

In August 2018, the U.S. Food and Drug Administration (FDA) announced its approval of the MolecuLight i:X Wound Imaging Device (Smith and Nephew). This had been approved for the Canadian market since 2015.3 

The MolecuLight i:X is a state of the art fluorescence imaging device that provides instant visual detection and documentation of bacteria, which might otherwise be invisible to the naked eye, in wounds. The MolecuLight i:X emits a precise wavelength of safe ultraviolet light, which interacts with the wound tissue and bacteria, causing the wound and surrounding skin to emit a green fluorescence (i.e. collagen), a red fluorescence (i.e. porphyrins) for potentially harmful bacteria or a cyan-fluorescence color (greenish blue) due to endogenous pyoverdine molecules, which is mostly attributed to Pseudomonas spp.

There is nothing to inject. The safety profile of MolecuLight i:X is not much different than that of taking a regular digital image or that of using a smartphone.

Evidence from clinical studies indicates that the MolecuLight i:X can detect the following bacterial species that we most often encounter in wound care settings:4–6

  • Staphylococcus aureus
  • Methicillin-resistant Staphylococcus aureus (MRSA)
  • Enterobacter cloacae
  • Enterococcus faecalis
  • Proteus mirabilis
  • Klebsiella pneumoniae
  • Escherichia coli
  • Beta-hemolytic Streptococci (Group B)
  • Coagulase-negative Staphylococci (e.g. S. lugdunensis)
  • Pseudomonas aeruginosa

Being able to visualize the presence of bacteria in a wound at chair side, as opposed to waiting for culture confirmation, should help us decide on a more cost-effective course of action on the day of care. One might conclude that a simple, traditional dressing—not an antimicrobial dressing—is the best solution if there is no contamination by bacteria. More judicious use of advanced dressings means more cost savings. If one chooses advanced treatments such as cellular and tissue-based products, the MolecuLight i:X assists clinicians in removing bacteria prior to the application of these treatments to optimize the therapy. The device can help us predict better outcomes and control the use of resources. This may become of more importance as we continue on our current path with alternative payment models based on outcomes and cost-driven care.  

Clinical studies in the Canadian health system have demonstrated up to an 89 percent overall reduction in cost in comparison to standard care by having this information from MolecuLight i:X readily available.4

The MolecuLight i:X can detect bacteria at and below the wound surface (typically to 1.5 mm deep). When debriding a wound using fluoresence imaging guidance, I may discover bacteria in deeper parts of the wound that were not visible to the naked eye prior to debridement. This allows me to be more thorough in my debridement. Cultures are still recommended with sensitivity so one can implement a more targeted treatment plan. In the hospitals, we are all now hearing about antibiotic stewardship and this device can definitely play a role in helping us to argue for times when we do not give antibiotics just because there is an open wound. With devices like the MolecuLight i:X, we can prove why our intuition (or our experience) says we do not need to give every patient with an open wound oral antibiotics, even if they have diabetes.

The MolecuLight i:X can also capture standard wound images and enables physicians to quickly and accurately measure wound areas for documentation. The device still does not measure depth, which one should do manually, but I am advised that the engineers are working on being able to measure depth with the device. Just the fact that the MolecuLight i:X can quickly calculate the length and width is of great benefit with documentation of debridement so one can bill the procedure correctly.

Clinicians can use the device to evaluate treatment effectiveness in real-time and reduce or eliminate wound care costs associated with inappropriate choices of dressings or treatment modalities.

Smith and Nephew has been the global distributor of the MolecuLight i:X and will also be the distributor of the device in the United States following the FDA approval last August.7

I was so very excited about the MolecuLight i:X. When I first heard about in in 2016 at the Symposium on Advanced Wound Care (SAWC), I immediately contacted the researcher to see how I could get my hands on it.5 I have been using it in the clinic since August 2018.

On January 31, 2019, we enrolled the first patient in the clinical trial I initiated, looking at cellular and tissue-based products or skin grafts in an attempt to predict the success or failure of these procedures by taking images with the device. I hope to have enough information to be able to present this study at the American Podiatric Medical Association annual meeting in late summer this year. Submission is pending.

References

1. Dubay L. Fluorescence biosensors detect, measure cancer cells' ability to metastasize. BioOptics World. Available at https://www.bioopticsworld.com/articles/2018/12/fluorescence-biosensors-detect-measure-cancer-cells-ability-to-metastasize.html . Published Dec. 10, 2018.

2. Nguyen QT, Olson ES, Aguilera TA, et al. Surgery with molecular fluorescence imaging using cell-penetrating peptides decreases residual cancer and improves survival. Proc Natl Acad Sci USA. 2010; 107(9):4317-4322.

3. Dubay L. Handheld fluorescence imager receives U.S. FDA De Novo clearance. BioOptics World. Available at https://www.bioopticsworld.com/articles/2018/08/handheld-fluorescence-imager-receives-u-s-fda-de-novo-clearance.html . Published Aug. 14, 2018.

4. Rennie MY, Lindvere-Teene L, Tapang K, Linden R. Point-of-care fluorescence imaging predicts the presence of pathogenic bacteria in wounds: a clinical study. J Wound Care. 2017;26(8):452-460.

5. Hill R, Rennie MY, Douglas J. Using bacterial fluorescence imaging and antimicrobial stewardship to guide wound management practices: a case series. Ostomy Wound Management. 2018;64(8):18–28.

6. Anghel EL, Falola RA, Kim PJ. Fluorescence technology for point of care wound management. Surgical Technology Int. 2016; 28:58-64.

7. Densford S. Smith and Nephew launches MolecuLight i:X wound imaging device. Medical Company Product News. Available at https://www.massdevice.com/smith-nephew-launches-moleculight-ix-wound-bacteria-visualizer-europe/ . Published Dec. 12, 2017.

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