Multimodal optical imaging of the oculofacial region using a solid tissue-simulating facial phantom

Area of Science:

• Biomedical optics
• Tissue optics
• Medical imaging technologies

Background:

• Spatial Frequency Domain Imaging (SFDI) quantifies subsurface tissue optical properties using patterned near-infrared light.
• The periocular region presents unique anatomical challenges for SFDI due to its complex, curved structure.
• Previous SFDI applications have focused on flatter tissues, with limited understanding of its accuracy on highly variable surfaces.

Purpose of the Study:

• To evaluate the geometric impact of the periocular region's complex topography on SFDI imaging reliability.
• To determine if anatomical variations affect the accuracy of measured optical properties in the periocular area.
• To assess the influence of imaging orientation on SFDI measurements in a facial phantom.

Main Methods:

• SFDI was used to measure the reduced scattering coefficient (µs') and absorption coefficient (µa) in a facial tissue-simulating phantom.
• Images were captured across various periocular regions of interest (ROIs), including the central eyelid margin and forehead.
• Measurements were taken from different imaging positions ('en face' and 'side profile') and compared to a flat reference surface.

Main Results:

• SFDI measurements in the inferior temporal, inferior nasal, superior temporal quadrants, and forehead showed accuracy comparable to a flat surface.
• No significant difference in measured optical properties was found based on imaging orientation for these flatter regions.
• Regions with extreme topographical variation, specifically the central eyelid margin and rostral lateral nasal bridge, exhibited significant differences in measured optical properties.

Conclusions:

• SFDI provides accurate optical property measurements for relatively flat periocular areas (ITQ, INQ, STQ, FH) on a generalized face model.
• Areas with significant topographical variations (CEM, RLNB) introduce measurement variability, highlighting the importance of ROI selection.
• Imaging orientation and device positioning do not appear to bias SFDI measurements in the periocular region, but careful ROI selection is crucial for accuracy.