Numerical Simulation of a Scanning Illumination System for Deep Tissue Fluorescence Imaging

Area of Science:

• Biomedical Optics
• Fluorescence Imaging
• Small Animal Imaging

Background:

• Fluorescence imaging in small animals is limited by light scattering, absorption, and autofluorescence.
• Near-infrared (NIR) fluorescent contrast agents and advanced imaging configurations are being explored to overcome these limitations.

Purpose of the Study:

• To quantitatively compare the influence of light wavelength and imaging configurations on fluorescence imaging performance.
• To evaluate surface radiance and spatial resolution for full-field illumination versus scanning systems across NIR wavelengths.

Main Methods:

• Utilized a modified simulation tool, Near-Infrared Fluorescence and Spectral Tomography, to calculate surface radiance.
• Embedded fluorescent targets within a scattering medium at varying depths.
• Acquired surface radiance and spatial resolution data for emission wavelengths from 620 nm to 1000 nm.

Main Results:

• Spatial resolution in scanning systems remained independent of tissue optical properties.
• Full-field illumination showed degraded spatial resolution at longer wavelengths.
• The scanning system achieved a 25% lower full width at half maximum (FWHM) compared to full-field illumination for centrally located targets.

Conclusions:

• While NIR wavelengths can enhance surface radiance in small animal fluorescence imaging, they may compromise spatial resolution.
• Scanning imaging configurations demonstrate superior spatial resolution compared to full-field illumination, particularly in scattering media.