Can OCT be sensitive to nanoscale structural alterations in biological tissue?

Area of Science:

• Biomedical Optics
• Nanotechnology
• Tissue Engineering

Background:

• Understanding nanoscale tissue structure is vital for biological processes.
• Current optical microscopy struggles with in situ nanometer-scale tissue quantification.
• Optical Coherence Tomography (OCT) has resolution limits, hindering nanoscale analysis.

Purpose of the Study:

• To demonstrate OCT's sensitivity to nanometer-scale tissue properties without resolving geometrical features.
• To introduce Inverse Spectroscopic OCT (ISOCT) for quantifying mass-density correlations.
• To validate ISOCT's sub-diffractional sensitivity and 3D imaging capabilities.

Main Methods:

• Quantifying tissue mass-density distribution via autocorrelation functions (Whittle-Mateŕn family).
• Measuring wavelength-dependent backscattering (μb(λ)) and scattering (μs) coefficients.
• Developing ISOCT to calculate the mass-density correlation function.

Main Results:

• ISOCT demonstrates sensitivity to length scales from approximately 30 to 450 nm.
• Sub-diffractional length scales, though not resolvable by OCT, are detectable.
• Validation through numerical simulations, phantom studies, and ex vivo colon tissue analysis (cross-validated with SEM).

Conclusions:

• ISOCT extends OCT's capabilities to probe sub-diffractional nanoscale tissue properties.
• The technique enables 3D imaging of these nanoscale features in biological samples.
• ISOCT offers a novel approach for in situ nanometer-scale tissue characterization.