The imaging system shown in Fig. 1(a), which also served as the surgical microscope, consisted of a stereo-microscope (SMZ-1000) with a objective (P-Plan Apo, numerical aperture of 0.012 at zoom magnification and 0.05 at zoom magnification), fluorescent filter attachment, and dual beam splitter (Nikon Instruments, Melville, NY), an excitation light source, a computer, a calibration pyramid, and two high-performance synchronized digital CCD cameras with 2 GB of internal memory (pco.1600, PCO-TECH, Romulus, MI). The angle of view difference between the two cameras was 6.3 deg. During image acquisition, the arterial images were stored on the camera’s internal memory and then, after each experiment, downloaded to a computer for image processing. The near-infrared emission light of the contrast agent was filtered using 18-mm diameter 690- to 730-nm bandpass emission filters (710AF40, Omega Optical, Brattleboro, VT). To excite the fluorescent contrast agent, a 150-W fiber-optic illuminator (Schott-Fostec, LLC, Auburn, NY) was used; it was outfitted with an EKE high-output halogen bulb (USHIO, Cypress, CA) and depleted of infrared wavelengths using a hot mirror (0 angle of incidence, Edmund Optics, Barrington, NJ). Attached to the illuminator was a liquid light guide (8 mm core diameter, 1 m long, Newport, Irvine, CA) and a fiber-optic focusing lens unit (Edmund Optics), which was modified to hold the 25-mm-diameter Qdot excitation filter (shortpass 650 nm cutoff, Edmund Optics) [see Fig. 1(b)]; the focusing unit was attached to an articulating arm mounting system to position the focusing unit during image acquisition. The calibration pyramid [see Fig. 1(c)] used in this study to define the imaging geometry was analogous to that used in previous biplane angiographic studies of human coronary arterial motion.10,35 The pyramid was a black Delrin pyramid ( base, 8.0 mm height) embedded with 88 0.5-mm-diameter stainless steel spheres (Salem Specialty Ball, Canton, CT), with the centroid of each sphere’s relative location known.