Researchers at University of Arizona (USA) have developed a prototype of a new microscope technology that could help surgeons work with a greater degree of accuracy. The new technology, augmented microscopy, overlays images depicting diagnostic information such as blood flow and cancerous tissue on real images of blood vessels and other tissues and structures being viewed in the microscope.
A report on the work by SPIE member Jeffrey Watson and co-authors from the university’s departments of Biomedical Engineering and Surgery was published in October 2015 in the Journal of Biomedical Optics.
The new technology is an improvement over the specialized stereomicroscopes that are widely used for image guidance during delicate operations such as neurosurgery. Within the last decade, they have been combined with near-infrared fluorescence imaging, in which NIR scans may reveal patterns of blood flow or differentiate cancerous from normal tissue.
These microscopes, however, switch between two different views: the fully optical bright-field (real) view and the computer-processed projection of NIR fluorescence. In complex vascular surgeries, for example, the NIR image is two-dimensional, and on its own lacks the spatial cues that would help the surgeon identify anatomical points of reference. So the surgeon must visualize how the fluorescence in the NIR image lines up with the respective anatomical structures shown in the bright-field view.
In “Augmented microscopy: Real-time overlay of bright-field and near-infrared fluorescence images,” the researchers describe their prototype of an augmented stereomicroscope that presents a simultaneous view of real objects in the surgical field and computer-processed images superimposed in real time.
Researchers delivered NIR laser light through a handheld laser wand to demonstrate NIR laser beam guidance by augmented microscope: (a) visible image conceals location of NIR laser beam, (b) NIR image lacks any spatial information, and (c) augmented image visualizes both NIR light and visible spatial cues.
EXPANDING SURGEONS’ VISION
“Surgeons want to see the molecular signals with their eyes so that they can feel confident about what is there,” said journal associate editor Brian Pogue of Dartmouth College (USA). “Too often, what they see is a report of the signals depicted in false color on a monitor. By displaying information through the surgical scope itself, the surgeon then sees the information with his or her own eyes.”
Pogue, an SPIE member who cochairs the molecular-guided surgery conference at BiOS, part of SPIE Photonics West, said he sees the work being important in advancing the translation of research into clinical practice. “There are very few papers on this idea of augmenting the surgical field of view that the surgeon sees, yet this is a high-interest topic,” he said.
“This article presents a very practical idea and innovative implementation which is well done technically.”
The prototype offers advantages over earlier versions of augmented microscopes. By utilizing the optical path of the stereomicroscope, it maintains full three-dimensional stereoscopic vision, which is lost in digital display systems.
It also retains the imaging environment familiar to surgeons, including key features of surgical microscopes such as real-time magnification and focus adjustments, camera mounting, and multiuser access.
USEFUL FOR LASER SURGERY
One possible application for this augmented microscope is laser surgery. In the past, surgeons could not see the laser beam through the standard stereomicroscope, nor anatomical details in the NIR images.
The researchers also suggest that this technology will be useful in the surgical treatment of brain tumors. Surgeons aggressively removing a tumor run the risk of damaging normal brain tissue and impairing the patient’s brain functions; on the other hand, incomplete removal of a tumor results in immediate relapse in 90% of patients.
Being able to simultaneously see the surgical field and the contrast agent identifying cancerous tissue within the augmented microscope may allow surgeons to remove these challenging tumors more accurately.
Watson, a PhD candidate in biomedical engineering at the university, received funding for the research from the National Institutes of Health. Coauthors are Christian F. Gainer, Nikolay Martirosyan, Jesse Skoch, G. Michael Lemole, Jr., Rein Anton, and Marek Romanowski.