Augmented Microscopy Increases Surgical Accuracy

Prototype imaging technology can overlay virtual diagnostic data (such as blood flow) on top of images being viewed directly through a microscope.

Developed by researchers at the University of Arizona (UA; Tucson, USA), the augmented microscopy intraoperative imaging technique merges bright-field optical and electronically processed near-infrared (NIR) fluorescent images within the optical path of a stereo-microscope. According to the researchers, the augmentation can be implemented as an add-on module to visualize NIR contrast agents, laser beams, or various types of electronic data within surgical microscopes commonly used in neurosurgical, cerebrovascular, otolaryngological, and ophthalmic procedures.

By utilizing the optical path of the stereomicroscope, the augmentation maintains full three-dimensional (3-D) stereoscopic vision, which is lost in fully digital display systems. It also retains a familiar imaging environment, including key features of surgical microscopes, such as real-time magnification and focus adjustments, camera mounting, and multiuser access. Under 100,000 lux illumination, the augmented microscope can detect a 189 nM concentration of indocyanine green, producing a composite of the real and synthetic images within the eyepiece of the microscope at a rate of 20 fps. The study describing the system was published on October 6, 2015, in the Journal of Biomedical Optics.

“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,” said lead author Jeffrey Watson, BSc, and colleagues of the UA departments of biomedical engineering and surgery. “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.”

“Surgeons want to see the molecular signals with their eyes, so that they can feel confident about what is there,” commented Journal of Biomedical Optics associate editor Prof. Brian Pogue, PhD, of Dartmouth College (Hanover, NH, 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.”

Current surgical stereomicroscopes used in complex vascular surgeries switch between two different views: the fully optical bright-field (real) view and the computer-processed projection of NIR fluorescence. Since the NIR image is two-dimensional, it lacks the spatial cues that would help the surgeon identify anatomical points of reference, and 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.

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