Fluorescence Lifetime Imaging

English version for veterinarians.

“A novel macroscopic imaging tool to guide surgeons in the removal of cancerous tissue: Fluorescence Lifetime Imaging”

(S. Janssen/H. de Rooster)

Fluorescence-guided surgery is used to assist surgeons in identifying structures and/or delineating the boundaries of diseased tissue. For fluorescence-guided surgery, contrast agents are required. Certain cells in our body, including hemoglobin, can also emit light, which may create background noise during surgery, making it less clear where the exact borders of the affected area begin or end. By using contrast agents that emit light at wavelengths where this background is no longer detected, it becomes possible to more precisely visualize the extent of the mass.

The most commonly used contrast agent, Indocyanine Green (ICG), has been approved for clinical use. Although this contrast agent does not specifically bind to cancer cells, it gradually accumulates in the tumor due to its poorly formed vasculature. Approximately 24 hours after injection, the dye is predominantly present in the tumor, though some signal may still be detected in healthy inflammatory tissue surrounding the tumor. Since this residual signal cannot be entirely eliminated, surgery is always performed 24 hours after the injection of the contrast agent.

Because ICG may persist in the healthy inflammatory tissue adjacent to the tumor, intensity-based measurements alone do not always provide a clear delineation of the tumor's margins. Therefore, researchers are exploring new techniques that can offer contrast where intensity measurements fall short.

Fluorescence Lifetime Imaging (FLI) not only measures the intensity of the emitted light but also the time it takes for a molecule to release a photon. This lifetime is influenced by the environment in which the contrast agent is located. This clinical study aims to determine whether Fluorescence Lifetime Imaging can better assist surgeons in removing cancer compared to techniques that rely solely on intensity measurements.

WHAT IS THE OBJECTIVE OF THIS PROJECT?

A previously published study by Massachusetts Eye and Ear hospital in the USA demonstrated the potential of Fluorescence Lifetime Imaging with Indocyanine Green in delineating cancerous tissue. The study indicated that Fluorescence Lifetime Imaging offers higher specificity in detecting cancer cells compared to traditional intensity-based imaging.

However, these studies have so far been only conducted on surgically removed tissue, meaning they were performed ex vivo. In collaboration with the Vrije Universiteit Brussel, we now aim to conduct an in vivo study in cancer patients during surgery to investigate whether this technique can provide intraoperative guidance to surgeons for complete cancer removal. The camera used in this study was developed by the Vrije Universiteit Brussel (VUB-ETRO). The VUB tauCAM™ has undergone extensive preclinical testing and has now been adapted for clinical use.

PARTICIPATION IN THE PROJECT

By informing pet owners about this study, specialists and surgeons will be able to use this new imaging technique during surgery to determine whether it can aid in the complete removal of cancer. The surgery itself will follow standard surgical protocols. Images will be taken during surgery and after the removal of the mass. Participation in this study could provide valuable insights that may lead to improved prognoses in the future. Additionally, participating pets will gain access to an advanced technique that is not yet available in human medicine. Positive results from this study could serve as a foundation for future clinical trials in humans.

As a token of appreciation for participation in this study, the pathological evaluation of the tumor will be offered free of charge. When available, the pathology results will be shared with both the referring veterinarian and the pet owner. There will be no additional costs compared to other patients undergoing surgery who are not part of the clinical study.

For any questions or concerns, please feel free to contact the researcher responsible for this project, veterinarian Simone Janssen (simone.janssen@ugent.be) or our team of specialists at chirurgie.khd@ugent.be