Flow measurement without phase information in optical coherence tomography images

Area of Science:

• Biomedical Optics
• Medical Imaging
• Flowmetry

Background:

• Doppler optical coherence tomography (DOCT) enables depth-resolved flow measurements but is limited to flow parallel to the imaging beam and requires phase information.
• Conventional OCT, while widely used, does not inherently provide flow information.

Purpose of the Study:

• To develop and validate an alternative method for quantitative flow assessment using speckle patterns from conventional amplitude optical coherence tomography (OCT) images.
• To demonstrate flow imaging in all directions, overcoming the directional sensitivity of DOCT.

Main Methods:

• Utilized speckle characteristics in conventional OCT images, analyzing changes in spatial frequencies over time.
• Employed an Intralipid flow phantom to establish a quantitative relationship between speckle properties and flow velocity.
• Performed 2D imaging to visualize flow dynamics in a tube and in vivo hamster skin.

Main Results:

• A linear relationship was observed between the ratio of high to low OCT image spatial frequencies and flow velocity across various speeds.
• Successful visualization of flow in both a controlled phantom and biological tissue (hamster skin) was achieved.
• Demonstrated the feasibility of extracting flow information irrespective of direction, without relying on phase data.

Conclusions:

• Speckle analysis of conventional OCT images provides a viable, phase-independent method for quantitative flow measurement.
• This technique expands the capabilities of OCT for comprehensive hemodynamic assessment in biological tissues.
• Offers a promising alternative for flow imaging, particularly in scenarios where DOCT is limited.