title: Monte Carlo investigation on quantifying the retinal pigment epithelium melanin concentration by photoacoustic ophthalmoscopy.
abstract: The retinal pigment epithelium (RPE) melanin plays an important role in maintaining normal visual functions. A decrease in the RPE melanin concentration with aging is believed to be associated with several blinding diseases, including age-related macular degeneration. Quantifying the RPE melanin noninvasively is therefore important in evaluating the retinal health and aging conditions. Photoacoustic ophthalmoscopy (PAOM), as an optical absorption-based imaging technology, can potentially be applied to measure variations in the RPE melanin if the relationship between the detected photoacoustic (PA) signal amplitudes and the RPE melanin concentrations can be established. In this work, we tested the feasibility of using PA signals from retinal blood vessels as references to measure RPE melanin variation using Monte Carlo (MC) simulation. The influences from PAOM axial resolution, the depth and diameter of the retinal blood vessel, and the RPE thickness were examined. We proposed a calibration scheme by relating detected PA signals to the RPE melanin concentrations, and we found that the scheme is robust to these tested parameters. This study suggests that PAOM has the capability of quantitatively measuring the RPE melanin in vivo.
authors.affiliation: Northwestern University, Department of Biomedical Engineering, Evanston, Illinois 60208.
authors.forename: Xiao
authors.initials: X
authors.lastname: Shu
authors.affiliation: Northwestern University, Department of Biomedical Engineering, Evanston, Illinois 60208.
authors.forename: Wenzhong
authors.initials: W
authors.lastname: Liu
authors.affiliation: Northwestern University, Department of Biomedical Engineering, Evanston, Illinois 60208bNorthwestern University, Department of Ophthalmology, Chicago, Illinois 60611.
authors.forename: Hao F
authors.initials: HF
authors.lastname: Zhang
mesh_terms: D000818:Animals; D003198:Computer Simulation; D006801:Humans; D008543:Melanins / Q000378:metabolism*; D008954:Models, Biological; D015233:Models, Statistical; D057054:Molecular Imaging; D009010:Monte Carlo Method; D009887:Ophthalmoscopy / Q000379:methods*; D061088:Photoacoustic Techniques / Q000379:methods*; D015203:Reproducibility of Results; D055213:Retinal Pigment Epithelium / Q000166:cytology* / Q000378:metabolism*; D012680:Sensitivity and Specificity; D014018:Tissue Distribution
chemical_list: D008543:Melanins