Improved Detection Sensitivity of Line-Scanning Optical Coherence Microscopy

Abstract

Optical coherence microscopy (OCM) is a promising technology for high-resolution cellular-level imaging in human tissues. Line-scanning OCM is a new form of OCM that utilizes line-field illumination for parallel detection. In this study, we demonstrate improved detection sensitivity by using an achromatic design for line-field generation. This system operates at 830-nm wavelength with 82-nm bandwidth. The measured axial resolution is 3.9 μm in air (corresponding to ~2.9 μm in tissue), and the transverse resolutions are 2.1 μm along the line-field illumination direction and 1.7 μm perpendicular to line illumination direction. The measured sensitivity is 98 dB with 25 line averages, resulting in an imaging speed of ~2 frames/s (516 lines/s). Real-time, cellular-level imaging of scattering tissues is demonstrated using human-colon specimens.

Line-field confocal optical coherence tomography for high-resolution noninvasive imaging of skin tumors

“…39,40 Several OCM methods have been reported, depending on how the sample is illuminated. 41 In the point-scanning method, an en face image is acquired by raster scanning a single spot of illumination, as with a confocal microscope. 42 However, this method is not well suited for B-scan imaging in real time because of the acquisition time.…”

“…This is due to the absence of a confocal gate, which results in lower detection sensitivity when compared with point-scanning and line scanning OCM. 41 A FF-OCM device (SkinTell) was commercialized by the company Agfa Healthcare for application in dermatology. B-scan imaging of skin, in vivo and in real time, is possible with the SkinTell device but with a significantly reduced penetration compared with conventional OCT 46 and a reduced spatial resolution (3 μm) compared with high-resolution FF-OCM.…”

“…43 Compared with conventional TD-OCT (with a large DOF), the lower detection dynamic range of a line scan camera than a photodiode is thus compensated (at least partially) by a more efficient confocal spatial filtering of unwanted light and an improved signal collection due to the use of an objective with higher NA. Compared with conventional FD-OCT, the more efficient confocal spatial filtering resulting from the use of an objective with higher NA enables LC-OCT to image in highly scattering tissues such as skin to a depth approaching that reached by FD-OCT. 20 The confocal gate in LC-OCT, although less efficient than that achieved in point-scanning OCM, 41 provides an advantage of LC-OCT over FF-OCM that has no confocal gate. The larger amount of incoherent scattered light with full-field illumination compared with line illumination reduces the maximum usable optical power before the camera saturates.…”

A compact high‐speed full‐field optical coherence microscope for high‐resolution in vivo skin imaging

“…Furthermore, there is no confocal gating mechanism in FF‐OCM to reject out‐of‐focus light. The amount of light backscattered from the sample that does not contribute to the useful interferometry signal and that is incident onto the camera sensor is usually much larger than the amount of light that does contribute to the useful interferometry signal . A camera sensor with a large dynamic range is then required to resolve the contribution of the “useful” light among all the detected light.…”

Mirau-based line-field confocal optical coherence tomography

“…On the other hand, LC-OCT benefits from a confocal gate obtained with the line-scan camera that is optically conjugated with the illumination line to act as a confocal slit, along with the use of a relatively high NA microscope objective [2,17,18]. The confocal gate in LC-OCT, although less e cient than with point scanning and point detection, is beneficial for the imaging penetration depth in scattering samples [2,19]. Despite the lower detection sensitivity of TD-OCT over FD-OCT [20], the more e cient confocal spatial filtering enables LC-OCT to image in highly scattering tissues such as skin to a depth approaching that reached by FD-OCT [21].…”