A handheld optical device for image-guided surgery Free

Magnetic resonance imaging (MRI) and computer-aided x-ray tomography (CT) can both provide surgeons with an image of a malignant tumor before an operation. But neither technique is compatible with surgery. To excise a tumor without damaging healthy tissue, a surgeon needs a safe, convenient means to see the tumor's edges while the patient lies on the operating table. A collaboration led by Huabei Jiang of the University of Florida in Gainesville and Lily Yang of Emory University in Atlanta aims to reach that goal with an imaging system based on fluorescent molecular tomography (FMT). The patient—or at this stage of R&D, the lab mouse—is given a dose of nanoparticles, which make their way to a tumor, stick to its surface, and fluoresce in the near-IR. Photons in that waveband can penetrate about a centimeter into tissue, but they also scatter heavily, which complicates imaging. Forming a surgically useful 3D image entails using a sensitive and compact imager that can view the target from several angles and then applying a sophisticated reconstruction algorithm. The front end of the Gainesville–Emory imager consists of 25 optical fibers bundled together like a handful of pencils. Ten of the fibers deliver near-IR laser light to the target; the other 15 send the returning fluorescent light to a CCD detector. Moving the fibers over the target yields the image. In a recent test, the FMT imager reliably delineated tumors 5 mm beneath a mouse's skin with a precision of 0.5 mm laterally and 1.5 mm axially. (Q. Zhao et al., Med. Phys. 38, 5873, 2011.)—Charles Day