Diagnostics & Imaging Week Contributing Writer
Putting a microscope at the tip of an endoscope suddenly advances by a considerable magnitude the diagnostic and imaging opportunities for surgeons.
While continuing to watch a macro view rendered by the endoscope’s camera, surgeons are able to zoom to a cellular close-up with a magnification of tissue up to 1,000 times in order to determine in real time the stage of development of a disease with sub-surface, even sub-cellular resolution.
Clinical trials have shown that endomicroscopy is comparable to conventional histology, for example, in distinguishing intraepithelial neoplasia.
Researchers from Johns Hopkins University (Baltimore) and Johanes Gutenberg University of Mainz (Mainz, Germany) noted in the conclusion of their study of Barrett’s esophagus in 46 patients, “In vivo microscopy can immediately change the macroscopic diagnosis” with high accuracy and without prolonging procedure time.
The expected economic benefit of virtual histology, also called optical biopsy, is a significant reduction in biopsy samples required for a diagnosis compared to a typical random biopsy protocol. Endomicroscopy enables surgeons to extract fewer suspect tissue samples and with pinpoint precision for laboratory tests.
First introduced in 2004 as a technology demonstration at Digestive Disease Week (DDW) in New Orleans, the images presented by Pentax (Tokyo) provoked “frenetic activity,” the company reported.
Since that first glimpse at the possibilities, enthusiasm for this potentially disruptive technology in gastroenterology has grown as two competing clinical endomicroscopy systems received FDA 501(k) clearance, progressively refined equipment and launched multi-center studies to establish the medical and economic benefit for early GI cancer diagnosis.
At DDW 2007, to be held in Washington May 19-24, two commercially available confocal endomicroscopy systems — Pentax’s OptiScan and the CellVizio-GI from Mauna Kea Technologies (Paris) — will be presented. Pentax was first to market with promotions for OptiScan at DDW 2006 in Los Angeles.
CellVizio-GI, which had a single poster displayed last year, will have a substantially wider footprint at DDW 2007, with five speaking sessions, eight posters, a video forum and a display area.
Results from clinical trials with OptiScan or CellVizio on Barrett’s esophagus to test optical biopsy against traditional histologic results will be presented by Johns Hopkins, Gutenberg University, the Mayo Clinic (Rochester, Minnesota), Technical University of Munich (Munich, Germany) Charite Hospital (Berlin) and University Hospital Nottingham (Nottingham, UK).
While Pentax has narrowed its focus exclusively to the large market potential of gastrointestinal diseases with OptiScan — jointly developed by Optiscan Imaging (Victoria, Australia) — the French start-up Mauna Kea is building out to wider applications for CellVizio in clinical and surgical markets from an initial customer base for in vivo animal research.
In March, Mauna Kea reported signing an exclusive distribution agreement with Leica Microsystems (Wetzlar, Germany), boosting its position in the clinical benchtop market.
In May, concurrent with the presentation of CellVizio-GI at DDW, the company will introduce its most recent product evolution, CellVizio-Lung, at the American Thoracic Society (ATS; New York) meeting in San Francisco.
Rigid fixed confocal microscopes long ago proved their value for in vitro research and for benchtop small animal in vivo research.
The revolutionary development was to place the microscope objective at the end of a flexible fiber optic bundle that sends signals back to an image processor for rendering on a monitor. For practical purposes, the length of the cable is unlimited, as signal attenuation in the optic fibers is insignificant. The deceptively thin (3 mm to 1.4 mm) and common-looking cable houses up to 30,000 optic fibers with a 2-micron diameter.
Where conventional microscopes gather light from an illuminated area at all depths, a confocal objective screens out reflected or refracted light except for that coming precisely from a single point on the targeted surface. The surface is scanned point-by-point following a classic Cartesian protocol with a 488-nanometer laser pulse under the confocal objective covering a maximum field of view of 600 x 500 m and a depth of observation from 0 to 150 m, depending on the model.
Confocal endomicroscopy benefits from the vast families of agents, biomarkers and plain stains developed in clinical research for fluoresence of specific objects, biological processes or disease demarcation.
With the aid of such agents, the resolution of confocal laser microscopy can be applied to imaging of molecular-level processes and objects.
Researchers from Harvard Medical School (Boston) will deliver a paper to a molecular imaging session at DDW 2007 presenting results of an effort to detect changes in pancreatic ductal adenocarcinom capillary diameter distribution using a CellVizio suite of probe, laser scanning unit and software for display.
“We are lucky with the lungs,” said Lacombe. “The alveoli and macrophage are composed of collagen and elastine, both being naturally fluorescent under the blue laser light used for CellVizio-Lung. The tar from cigarettes is also naturally visible.
“To this point we are still in the physics of optics,” he said, adding that the raw view through a confocal objective is “like looking at the world through a sieve.”
The final challenge for confocal endomicroscopy becomes pulling the point-by-point data into an image that “makes everyone forget the technology,” Lacombe said.
The solution, mathematics, comes naturally to Lacombe and fellow astrophysicist Sasha Loiseau, president of Mauna Kea. First the fiber bundle pattern is removed, said Lacombe, creating a more natural view. The dynamic sequence of data arriving at a rate of 12 frames per second is then stitched into a natural motion in real time.
A video clip is not the only output format, as the digitized image data can also be reconstructed to show cell development across a landscape of several millimeters in a still image.
The unique solution of algorithms and mathematics developed by Mauna Kea will be the subject of a poster presentation at DDW 2007, “Mosaicing of Confocal Microscopic Video Sequences: Larger Field of View and Still Higher Resolution.”
Lacombe sums it up: “Building on the resolution with mathematics we reconstruct a larger field of view and create a very different perception of the landscape.”
Reducing the number of biopsy samples from dozens to just two “is a significant change,” he said.
“We turn on the light where people have not seen before,” said Lacombe. “We do not know where people might want to take this.”