Fluorescence In Vivo Endomicroscopy Part 2: Applications of High-Resolution, 3-Dimensional Confocal Laser Endomicroscopy
Peter Delaney4 1
Mohammedayaz Rangrez,1 Optiscan, Toronto, Ontario, Canada
*
lbussau@optiscan.com
Abstract: Fluorescence in vivo endomicroscopy (FIVE) is a state-of- the-art endoscopy technique used to image tissue interactions and molecular events in a cell. In Part 1 of this series, the history, types of confocal laser endomicroscopy (CLE), and limitations of the technology were discussed. In Part 2 of the series, we describe several applica- tions of FIVE technology, including advances in cancer, gastrointestinal, liver, rectal mucosal barrier function, acute lung injury, and brain imag- ing. Future perspectives for the technology are also presented.
Keywords: in vivo endomicroscopy, fluorescence, cancer, acute lung injury, brain imaging
Introduction In Part 1 of this series, we described fluorescence in vivo
endomicroscopy (FIVE) technology and some of the advan- tages and limitations of the instruments [1]. In simple terms, it is a laser scanning confocal microscope where the imag- ing end is attached to an optical fiber allowing the operator to “peek” inside a living organism. Confocal laser endomi- croscopy (CLE) has reversed the age-old approach where the biological tissue was resected, processed, stained, and imaged on a microscope stage. With FIVE, tissue architecture can be imaged instantaneously with the use of intravenous (i.v.) and topical fluorescent dyes, providing a virtual real-time biopsy. FIVE is a cutting-edge CLE technology with subcellu- lar resolution and optical sectioning competency. Compared to other CLEs, FIVE visualizes three-dimensional (3-D) tis- sue architecture in vivo and provides information on tissue interactions with its environment and even molecular events in the cell (Figure 1). It has successfully achieved the vision of endoscopists to obtain histoarchitecture of a given tissue while performing endoscopy. Over the last 20 years, FIVE has been used in integrated confocal endomicroscopes for tar- geted gastrointestinal biopsies, in a neurosurgical device for surgical assistance in brain cancer surgery, and for veterinary and laboratory imaging purposes. Several applications and the future perspectives of FIVE are described below.
Fluorescence In Vivo Endomicroscopy Applications Intraoperative imaging for surgical guidance in cancer.
Te goal of cancer surgery is complete extirpation of dis- eased tissue. Te challenge in meeting this requirement is the accurate determination of the extent of tumor spread and infiltration of apparent margins. Te current gold standard, histopathological examination of excised tissue, provides
14 doi:10.1017/S1551929521000729
cellular detail but has several drawbacks. Firstly, quick his- topathological confirmation (frozen sections) takes between 20 minutes and up to an hour while the surgeon waits for the pathologist’s interpretation. Frozen section results are generally considered to be of lower accuracy when compared to more time-consuming methods but are nonetheless cru- cial for the rapidity with which cellular information can be gleaned. For fixed tissues, pathology may take up to a week for results. Secondly, the excised tissue shrinks aſter excision while the wound area expands. Tus, it is extremely difficult to pinpoint an area of the wound bed by looking at the excised tissue. Te surgeon must oſten guess and rely on his/her expe- rience, if the pathologist recommends cutting more from a specific area of the wound bed. Tirdly, this process does not provide the surgeon cellular-level detail while performing the surgery. Critical tumor resection surgeries can be life- threatening and can leave the patient physically impaired if too much tissue is excised. FIVE provides a suitable alterna- tive to histopathological examination during cancer surgery. It can capture images while the surgery is being performed, rapidly providing the surgeon with cellular details of the tis- sue to be excised. FIVE can be used with fluorophores show- ing tissue architecture, or with cancer specific fluorophores, and can provide the surgeon confirmation and confidence on the excision procedure. FIVE has been used successfully for performing intraoper-
ative virtual biopsies. Nguyen and his colleagues [2] performed FIVE imaging in patients who underwent surgery for intra- abdominal malignancy (gastric adenocarcinoma, pancreatic ductal adenocarcinoma, and small bowel lymphoma) for real- time, intraoperative, in vivo histologic surface and subsurface imaging. Te surgeons reported fluorescein contrast enabled visualization of cellular histoarchitecture and epidermal mor- phology of visceral organs, with magnification and resolu- tion equivalent to light microscopy. Tis enabled distinction between normal and diseased tissue and influenced surgical decisions. Similarly, Preul and his team tested the usability of FIVE in 74 glioma and meningioma patients. First-generation FIVE devices were able to detect gliomas with 94% specificity and 91% sensitivity and meningiomas with 93% specificity and 97% sensitivity [3]. FIVE can also work as a molecular imaging tool to visualize epidermal growth factor receptors (EGFR) in cell culture, mice xenograſt models, and human biopsied tissue
www.microscopy-today.com • 2021 May Lindsay Bussau,2
2Optiscan Pty Ltd., Mulgrave, Victoria, Australia 3Barrow Neurological Institute, Phoenix, Arizona 4Orb-Med Consulting, Melbourne, Victoria, Australia
* Kishwar Ifrit,2 Mark C. Preul,3 and
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