US 7,072,045 B2 · High resolution optical coherence tomography with an improved depth range using an axicon lens

Abstract

In optical coherence tomography (OCT), Axial and lateral resolutions are determined by the source coherence length and numerical aperture of the sampling lens, respectively. While axial resolution can be improved using a broadband light source, there is a trade-off between lateral resolution and focusing depth when conventional optical elements are used. The incorporation of an axicon lens into the sample arm of the interferometer overcomes this limitation. Using an axicon lens with a top angle of 160 degrees, 10 μm or better-lateral resolution is maintained over a focusing depth of at least 6 mm. In addition to high lateral resolution, the focusing spot intensity is approximately constant over a greater depth range.

Claims9

Dependent claims

An improvement in a scanning optical coherence tomographic (OCT) system, which includes an interferometer with a sample arm for scanning a sample, the improvement comprises an axicon lens disposed in the sample arm to simultaneously achieve high lateral resolution and a greater depth of focus of the sample, the axicon lens in the sample arm being provided with spatially coherent light where the axicon lens comprises a phase masked array.

A method for phase-resolved optical tomography comprising:

providing a source of at least partially coherent radiation through an interferometer, the at least partially coherent radiation characterized by a phase;
phase modulating the radiation in the interferometer at a modulation frequency;
scanning the sample with the source of at least partially coherent radiation through the interferometer in a sequence of pixel line scans using an axicon lens to simultaneously achieve high lateral resolution and a greater depth of focus of the sample, the sample having fluid flow therein;
changing the phase of the at least partially coherent radiation in response to the fluid flow at each pixel of each pixel line scan;
detecting interference fringes of the radiation backscattered from the sample into the interferometer through the axicon lens;
processing the detected interference fringes to determine phase signals of the detected backscattered interference fringes at each pixel of the pixel line scans to determine the corresponding phase at each pixel in a data window;
comparing the phase between corresponding pixels in two line scans to generate a difference between the phase at the two corresponding pixels in two line scans whereby speckle is substantially reduced;
and generating a tomographic image of the fluid flow in the sample from the phase difference at each pixel,
performing the foregoing steps to achieve one of the following:
to diagnose cancer in the gastrointestinal (GI), respiratory, and urogenital tracts including larynx, bladder, uterine and cervix cancers;
to diagnose cancer in skin;
to diagnose cardiovascular disease;
to provide an in situ three-dimensional tomographic image and velocity profiles of blood perfusion in human skin at discrete spatial locations in either the superficial or deep dermis;
to determine burn depth in skin;
to provide guidance regarding the optimal depth for burn debridement prior to definitive closure;
to determine tissue perfusion and viability immediately after injury, wound closure, replantation, or transposition of either rotational or free skin flaps;
to evaluate the vascular status of a buried muscle flap covered by a split thickness skin graft;
to separately monitor perfusion in the superficial and deeper flap components;
to distinguish between arterial or venous occlusion;
to determine the presence and/or extent of adjacent post-traumatic arterial or venous vascular injury by providing in situ tomographic image and velocity profile of blood flow;
to monitor the effects of pharmacological intervention on skin microcirculation including the effects of vasoactive compounds or inflammatory mediators;
to determine transcutaneous drug penetration kinetics;
to evaluate the potency of penetration enhancers;
to determine the irritation caused by chemical compounds, by patch-test allergens and by ultraviolet radiation;
to compare the reactivity of the skin microcirculation in different age and ethnic groups;
to determine the extent of intestinal vascular insufficiency or infarction;
to conserve intestine by confining resection to nonvascularized segments;
to measure ocular, blood flow and birefringence for diagnosis of ocular disease;
to image three-dimensional tumor microvasculature;
to optimize radiation dosimetry by assessing and quantifying alterations in tissue microvascular and matrix structure;
to determine long-term alterations in microvascular haemodynamics and morphology in chronic diseases such as diabetes mellitus and arteriosclerosis;
to map cortical hemodynamics with high spatial resolution for brain research;
to provide surgical guidance for brain surgery;
to image flow dynamics in microchannels of micro-electro-mechanic system (MEMS) chips;
to characterize and monitor of flow velocity when the fluid is encapsulated in highly scattering materials such as fibrous substances or resin composites;
to accurately measure particle concentration and size, and fluid flow velocity profile;
to provide useful diagnostic information for process monitoring and quality control;
to provide measurements involving turbid fluid flow samples such as materials processing of paints, pigmented fluids, and other types of opaque liquids;
or to characterize and monitor dry particulate flow within conduits such as a jet stream.

36 more elements

Dependencies are inferred from the claim text.

Facts

Application

10/345,671Filed 16 Jan 2003 · us provisional application

Priority

16 Jan 2002

Published

US 2003/0218756 A127 Nov 2003

Granted

4 Jul 2006

Term ends

Not estimatedThe source records don’t support an estimate.

Classification8 codes

G01B 9/02027
Characterised by the beam path configuration: two or more interferometric channels or interferometers
G01B 9/0201
Characterised by controlling or generating intrinsic radiation properties: using temporal phase variation
G01B 9/02035
Characterised by particularly shaped beams or wavefronts: shaping the focal point, e.g. elongated focus
G01B 9/02045
Characterised by particular imaging or detection techniques: using the Doppler effect

High resolution optical coherence tomography with an improved depth range using an axicon lens

Life of this patent

High resolution optical coherence tomography with an improved depth range using an axicon lens

Life of this patent

Abstract

Claims9