title: Noninvasive photoacoustic and fluorescence sentinel lymph node identification using dye-loaded perfluorocarbon nanoparticles.
abstract: The contrast mechanisms used for photoacoustic tomography (PAT) and fluorescence imaging differ in subtle, but significant, ways. The design of contrast agents for each or both modalities requires an understanding of the spectral characteristics as well as intra- and intermolecular interactions that occur during formulation. We found that fluorescence quenching that occurs in the formulation of near-infrared (NIR) fluorescent dyes in nanoparticles results in enhanced contrast for PAT. The ability of the new PAT method to utilize strongly absorbing chromophores for signal generation allowed us to convert a highly fluorescent dye into an exceptionally high PA contrast material. Spectroscopic characterization of the developed NIR dye-loaded perfluorocarbon-based nanoparticles for combined fluorescence and PA imaging revealed distinct dye-dependent photophysical behavior. We demonstrate that the enhanced contrast allows detection of regional lymph nodes of rats in vivo with time-domain optical and photoacoustic imaging methods. The results further show that the use of fluorescence lifetime imaging, which is less dependent on fluorescence intensity, provides a strategic approach to bridge the disparate contrast reporting mechanisms of fluorescence and PA imaging methods.
authors.affiliation: Department of Radiology, Washington University School of Medicine, 4525 Scott Avenue, Saint Louis, Missouri 63108, United States.
authors.forename: Walter J
authors.initials: WJ
authors.lastname: Akers
authors.forename: Chulhong
authors.initials: C
authors.lastname: Kim
authors.forename: Mikhail
authors.initials: M
authors.lastname: Berezin
authors.forename: Kevin
authors.initials: K
authors.lastname: Guo
authors.forename: Ralph
authors.initials: R
authors.lastname: Fuhrhop
authors.forename: Gregory M
authors.initials: GM
authors.lastname: Lanza
authors.forename: Georg M
authors.initials: GM
authors.lastname: Fischer
authors.forename: Ewald
authors.initials: E
authors.lastname: Daltrozzo
authors.forename: Andreas
authors.initials: A
authors.lastname: Zumbusch
authors.forename: Xin
authors.initials: X
authors.lastname: Cai
authors.forename: Lihong V
authors.initials: LV
authors.lastname: Wang
authors.forename: Samuel
authors.initials: S
authors.lastname: Achilefu
mesh_terms: D000042:Absorption; D000162:Acoustics; D000818:Animals; D001365:Axilla; D005456:Fluorescent Dyes / Q000737:chemistry / Q000378:metabolism; D005466:Fluorocarbons / Q000737:chemistry* / Q000378:metabolism*; D008027:Light; D008198:Lymph Nodes / Q000378:metabolism*; D008207:Lymphatic Metastasis / Q000175:diagnosis; D057054:Molecular Imaging / Q000379:methods*; D053758:Nanoparticles / Q000737:chemistry*; D051381:Rats; D013050:Spectrometry, Fluorescence
chemical_list: D005456:Fluorescent Dyes; D005466:Fluorocarbons