Article

Structured illumination enhances resolution and contrast in thick tissue fluorescence imaging

J Biomed Opt 15:010506. DOI:10.1117/1.3299321 ISBN: 1560-2281 (Electronic) 1083-3668 (Linking) pp.010506

ABSTRACT We introduce a noncontact imaging method utilizing multifrequency structured illumination for improving lateral and axial resolution and contrast of fluorescent molecular probes in thick, multiple-scattering tissue phantoms. The method can be implemented rapidly using a spatial light modulator and a simple image demodulation scheme similar to structured light microscopy in the diffraction regime. However, imaging is performed in the multiple-scattering regime utilizing spatially modulated scalar photon density waves. We demonstrate that by increasing the structured light spatial frequency, fluorescence from deeper structures is suppressed and signals from more superficial objects enhanced. By measuring the spatial frequency dependence of fluorescence, background can be reduced by localizing the signal to a buried fluorescent object. Overall, signal-to-background ratio (SBR) and resolution improvements are dependent on spatial frequency and object depth/dimension with as much as sevenfold improvement in SBR and 33% improvement in resolution for approximately 1-mm objects buried 3 mm below the surface in tissue-like media with fluorescent background.

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Keywords

33% improvement
 
axial resolution
 
deeper structures
 
fluorescence
 
fluorescent molecular probes
 
imaging
 
light microscopy
 
localizing
 
multiple-scattering regime utilizing spatially modulated scalar photon density waves
 
noncontact imaging method utilizing multifrequency
 
signal-to-background ratio
 
simple image demodulation scheme
 
spatial frequency
 
spatial frequency dependence
 
spatial light modulator
 
structured light spatial frequency
 
thick