In spectral-domain OCT, the speed is typically described as tens of thousands of A-scans per second. Which option correctly states this rate?

• A. Hundreds per second
• B. Thousands per second
• C. Tens of thousands per second
• D. Millions per second

Answer: (C)

In spectral-domain OCT, speed is described in A-scans per second because each A-scan is a depth profile obtained from a single spectral acquisition. The technology relies on a high-speed spectrometer and detector to capture many spectra per second and then convert each spectrum into an A-scan via Fourier transform. Clinically, SD-OCT systems typically operate in the tens of thousands of A-scans per second range (roughly 20–70 kA-scans/s, depending on the hardware). This makes tens of thousands per second the appropriate description of the rate. Rates in the hundreds or thousands per second are slower than what SD-OCT usually achieves, while millions per second exceed typical hardware capabilities, especially for standard SD-OCT setups.