title: Pixel-based absorption correction for dual-tracer fluorescence imaging of receptor binding potential.
abstract: Ratiometric approaches to quantifying molecular concentrations have been used for decades in microscopy, but have rarely been exploited in vivo until recently. One dual-tracer approach can utilize an untargeted reference tracer to account for non-specific uptake of a receptor-targeted tracer, and ultimately estimate receptor binding potential quantitatively. However, interpretation of the relative dynamic distribution kinetics is confounded by differences in local tissue absorption at the wavelengths used for each tracer. This study simulated the influence of absorption on fluorescence emission intensity and depth sensitivity at typical near-infrared fluorophore wavelength bands near 700 and 800 nm in mouse skin in order to correct for these tissue optical differences in signal detection. Changes in blood volume [1-3%] and hemoglobin oxygen saturation [0-100%] were demonstrated to introduce substantial distortions to receptor binding estimates (error > 30%), whereas sampled depth was relatively insensitive to wavelength (error < 6%). In response, a pixel-by-pixel normalization of tracer inputs immediately post-injection was found to account for spatial heterogeneities in local absorption properties. Application of the pixel-based normalization method to an in vivo imaging study demonstrated significant improvement, as compared with a reference tissue normalization approach.
authors.affiliation: Thayer School of Engineering, Dartmouth College, Hanover, New Hampshire 03755, USA.
authors.forename: Stephen C
authors.initials: SC
authors.lastname: Kanick
authors.affiliation: Department of Biomedical Engineering, Illinois Institute of Technology, Chicago IL 60616, USA.
authors.forename: Kenneth M
authors.initials: KM
authors.lastname: Tichauer
authors.affiliation: Thayer School of Engineering, Dartmouth College, Hanover, New Hampshire 03755, USA.
authors.forename: Jason
authors.initials: J
authors.lastname: Gunn
authors.affiliation: Thayer School of Engineering, Dartmouth College, Hanover, New Hampshire 03755, USA ; Department of Surgery, Geisel School of Medicine at Dartmouth, Hanover, New Hampshire 03755, USA.
authors.forename: Kimberley S
authors.initials: KS
authors.lastname: Samkoe
authors.affiliation: Thayer School of Engineering, Dartmouth College, Hanover, New Hampshire 03755, USA ; Department of Surgery, Geisel School of Medicine at Dartmouth, Hanover, New Hampshire 03755, USA.
authors.forename: Brian W
authors.initials: BW
authors.lastname: Pogue
keywords: (170.3660) Light propagation in tissues; (170.3880) Medical and biological imaging; (170.4580) Optical diagnostics for medicine