title: Reduction of excitation light leakage to improve near-infrared fluorescence imaging for tissue surface and deep tissue imaging.
abstract: OBJECTIVE
  Fluorescence-enhanced optical imaging using near-infrared (NIR) light developed for in vivo molecular targeting and reporting of various diseases provides promising opportunities for diagnostic imaging. However, the measurement sensitivity of NIR fluorescence (NIRF) optical imaging systems is limited by the leakage of the strong backscattered excitation light through rejection filters. In this article, the authors present a systematic method for improving sensitivity and validating the NIRF optical imager currently used for clinical imaging of human lymphatic function.
  
  
  METHODS
  The proposed systemic method consists of an appropriate filter combination and a collimation optics adapted to an NIRF optical imager. The spectral contributions were first assessed due to the excitation light backscattered from the tissue and from non-normal-incidence of the excitation light on the optical filters used in the authors' NIRF clinical imaging system. Then two tests were conducted to assess the system with and without the components of appropriate filters combination and collimation optics using: (1) a phantom to evaluate excitation light leakage as a function of target depth and (2) deployment in an actual human study.
  
  
  RESULTS
  The phantom studies demonstrate as much as two to three orders of magnitude reduction in the transmission ratio, indicating that the excitation light leakage can be reduced upon using the appropriate filter combination and collimation optics while an in vivo investigatory human study confirms improved imaging.
  
  
  CONCLUSIONS
  The method for reducing the excitation light leakage is presented for validating collected signals for fluorescence imaging.
authors.affiliation: Center of Molecular Imaging, The Brown Foundation Institute of Molecular Medicine, The University of Texas Health Science Center at Houston, Houston, Texas 77030, USA.
authors.forename: Banghe
authors.initials: B
authors.lastname: Zhu
authors.forename: John C
authors.initials: JC
authors.lastname: Rasmussen
authors.forename: Yujie
authors.initials: Y
authors.lastname: Lu
authors.forename: Eva M
authors.initials: EM
authors.lastname: Sevick-Muraca
mesh_terms: D003287:Contrast Media / Q000494:pharmacology; D003952:Diagnostic Imaging / Q000379:methods; D005453:Fluorescence; D005456:Fluorescent Dyes / Q000737:chemistry*; D006801:Humans; D007834:Lasers; D008027:Light; D008198:Lymph Nodes / Q000473:pathology; D055095:Optics and Photonics; D019047:Phantoms, Imaging; D019265:Spectroscopy, Near-Infrared / Q000379:methods*; D013499:Surface Properties; D013997:Time Factors
chemical_list: D003287:Contrast Media; D005456:Fluorescent Dyes