What are the scanning speeds of spectral domain OCT and time domain OCT?

What are the scanning speeds of spectral domain OCT and time domain OCT?

• A. SD: 400 A-scans per second; TD: 40,000 A-scans per second
• B. SD: 4,000 A-scans per second; TD: 400 A-scans per second
• C. SD: 40,000 A-scans per second; TD: 400 A-scans per second
• D. SD: 400 A-scans per second; TD: 4,000 A-scans per second

Answer: (C)

The main idea is that spectral-domain (Fourier-domain) OCT collects depth information much more quickly than time-domain OCT. In SD-OCT, the depth profile (A-scan) is obtained from the interference spectrum all at once with a spectrometer, so you can acquire many A-scans per second. In TD-OCT, the depth profile is built by mechanically sweeping the reference mirror to sample depths one by one, which limits speed to a few hundred A-scans per second. As a result, SD-OCT operates around tens of thousands of A-scans per second (commonly about 40,000 A-scans/s), while TD-OCT is much slower, around 400 A-scans per second. This is why the faster speeds are associated with spectral-domain systems and the slower speeds with time-domain systems.

The main idea is that spectral-domain (Fourier-domain) OCT collects depth information much more quickly than time-domain OCT. In SD-OCT, the depth profile (A-scan) is obtained from the interference spectrum all at once with a spectrometer, so you can acquire many A-scans per second. In TD-OCT, the depth profile is built by mechanically sweeping the reference mirror to sample depths one by one, which limits speed to a few hundred A-scans per second. As a result, SD-OCT operates around tens of thousands of A-scans per second (commonly about 40,000 A-scans/s), while TD-OCT is much slower, around 400 A-scans per second. This is why the faster speeds are associated with spectral-domain systems and the slower speeds with time-domain systems.