What is the axial resolution of spectral-domain (SD) OCT?

What is the axial resolution of spectral-domain (SD) OCT?

• A. 8-10 microns
• B. 3-7 microns
• C. 1-2 microns
• D. 10-15 microns

Answer: (B)

The axial (depth) resolution in spectral-domain OCT is set mainly by how broad the light source’s spectrum is. A wider bandwidth shortens the coherence length, giving finer depth resolution. The practical formula for a Gaussian spectrum is approximately Δz ≈ 0.44 λ0^2 / Δλ, where λ0 is the center wavelength and Δλ is the spectral bandwidth. With common SD-OCT light sources in the near-infrared (roughly 800–900 nm or 1050–1300 nm) and bandwidths on the order of tens to a hundred nanometers, this typically yields an axial resolution in tissue of about 3 to 7 microns. That’s why 3–7 microns is the best-fit range. Values around 1–2 microns would require an unusually large bandwidth, while 8–15 microns would be coarser than what SD-OCT commonly achieves.

The axial (depth) resolution in spectral-domain OCT is set mainly by how broad the light source’s spectrum is. A wider bandwidth shortens the coherence length, giving finer depth resolution. The practical formula for a Gaussian spectrum is approximately Δz ≈ 0.44 λ0^2 / Δλ, where λ0 is the center wavelength and Δλ is the spectral bandwidth. With common SD-OCT light sources in the near-infrared (roughly 800–900 nm or 1050–1300 nm) and bandwidths on the order of tens to a hundred nanometers, this typically yields an axial resolution in tissue of about 3 to 7 microns. That’s why 3–7 microns is the best-fit range. Values around 1–2 microns would require an unusually large bandwidth, while 8–15 microns would be coarser than what SD-OCT commonly achieves.