  The intensity levels allowed by safety standards (ANSI or ICNIRP) limit the
amount of light that can be used in a clinical setting to image highly
scattering or absorptive tissues with Optical Coherence Tomography (OCT). To
achieve high-sensitivity imaging at low intensity levels, we adapt a detection
scheme -- which is used in quantum optics for providing information about
spectral correlations of photons -- into a standard spectral domain OCT system.
This detection scheme is based on the concept of Dispersive Fourier
Transformation, where a fibre introduces a wavelength-dependent time delay
measured by a single-pixel detector, usually a high-speed photoreceiver. Here,
we use a fast Superconducting Single-Photon Detector (SSPD) as a single-pixel
detector and obtain images of a glass stack and a slice of onion at the
intensity levels of the order of 10 pW. We also provide a formula for a
depth-dependent sensitivity fall-off in such a detection scheme which can be
treated as a temporal equivalent of diffraction-grating-based spectrometers.
