title: Spatial localization of cardiac optical mapping with multiphoton excitation.
abstract: Depth and radius of regions interrogated by cardiac optical mapping with a laser beam depend on photon travel inside the heart. It would be useful to limit the range of depth and radius interrogated. We modeled the effects of a condensing lens to concentrate laser light at a target depth inside the heart, and near infrared excitation to increase penetration and produce two-photon absorption. A Monte Carlo simulation that incorporated a 0.55-NA lens, and absorption and scattering of 1064- or 488-nm laser light in 3-D cardiac tissue indicated the distribution of excitation fluence inside the tissue. A subsequent simulation incorporating absorption and scattering of transmembrane voltage-sensitive fluorescence (wavelength 669 nm) indicated locations from which fluorescence photons exiting the tissue surface originated. The results indicate that mapping at depths up to 300 microm in hearts can provide significant improvement in localization over existing cardiac optical mapping. The estimated interrogation region is sufficiently small to examine cardiac events at a cellular or subcellular scale and may allow mapping at various depths in the heart.
authors.affiliation: The University of North Carolina at Chapel Hill, The Department of Biomedical Engineering of the School of Medicine, CB #7575, 152 MacNider Hall, Chapel Hill, North Carolina 27599-7575, USA.
authors.forename: Venkat K
authors.initials: VK
authors.lastname: Ramshesh
authors.forename: Stephen B
authors.initials: SB
authors.lastname: Knisley
mesh_terms: D000200:Action Potentials / Q000502:physiology*; D003198:Computer Simulation; D006329:Heart Conduction System / Q000502:physiology*; D021621:Imaging, Three-Dimensional / Q000379:methods*; D008564:Membrane Potentials / Q000502:physiology*; D036641:Microscopy, Fluorescence, Multiphoton / Q000379:methods*; D008955:Models, Cardiovascular; D011726:Pyridinium Compounds; D041622:Tomography, Optical / Q000379:methods*
chemical_list: D011726:Pyridinium Compounds; C050019:1-(3-sulfonatopropyl)-4-(beta)(2-(di-n-butylamino)-6-naphthylvinyl)pyridinium betaine