A computer modeling study of the localization of cardiac optical mapping at discrete depths below the tissue surface

Depth and radius of the region interrogated by cardiac optical mapping with a laser beam depend on photon travel inside the heart. It would be useful to limit range of depth and radius interrogated. Here the effects of a condensing lens to concentrate laser light at a target depth in the heart was modeled Monte Carlo computer simulations that incorporated a 0.55 NA lens in air and absorption and scattering of 488 nm laser light in 3-d cardiac tissue indicated the distribution of excitation light fluence. A subsequent computer simulation incorporating absorption and scattering of transmembrane voltage-sensitive fluorescence (669 nm) indicated locations in tissue from which fluorescence photons exiting the tissue surface originated The results indicate the heart can be interrogated at a discrete depth below the surface of myocardium with a condensing lens, although resolution is limited This may be applicable to laser scanner systems used for cardiac optical mapping.