Imaging pancreatobiliary ductal system with optical coherence tomography: A review

Table 3 Comparison of different types of optical coherence tomography systems

Parameters	TD-OCT	SD-OCT	SS-OCT/OFDI
Mechanism	Interference signals are detected as a function of optical time delay between obj. and ref. arm.	Interference signals are detected with a camera as a function of optical frequency	Spectral fringes are mapped to time domain by use of a swept laser and are measured with a detector as a function of time
Major components	Broadband laser, optical delay line and a detector	Broadband laser, spectrometer and camera	Tunable laser, digitizer and a balanced detector
Spectrum	800 nm, 1000 nm, 1300 nm	800 nm, 1000 nm, 1300 nm	800 nm, 1000 nm, 1300 nm
Imaging depth	1-3 mm	1-3 mm	1-3 mm
Resolution	≥ 10 μm	1-10 μm	1-10 μm
Imaging speed (axial scan rate)	Slow ( ≤ 5 kHz)	Fast (20-150 kHz)	Fairly fast (20-400 kHz)
SNR	Low	High	High
Image quality	Moderate	Fairly high	High
Sensitivity	Low (70-90 dB)	High (85-105 dB)	High (≥ 100 dB)
Phase stability	Low	High	Moderate
Portability	Yes	Yes	Yes
System cost	Low	High	Moderate

SNR: Signal-to-noise ratio; dB: Decibel; TD-OCT: Time domain OCT; SD-OCT: Spectral-domain OCT; ODFI: Optical frequency domain imaging; SS-OCT: Swept source OCT.