Optical Microangiography

A Label-Free 3-D Imaging Technology to Visualize and Quantify Blood Circulations Within Tissue Beds In Vivo

Ruikang K. Wang

(OMAG)

WHAT IS ANGIOGRAPHY & ANGIOGRAM

Angiography is technic imaging blood circulating paths, blocks or any other disturbances.

Mainly used to cardiovascular and neuroscience

Angiogram is a treatment to avoid that disturbances.

That means avoid to surgery(bypass or any open crane surgery).

INTRODUCTION

Recently developed volumetric 3D imaging technique. It is capable of producing 3D dynamic blood perfusion

within microcirculatory tissue in vivo. Its image contrast of OMAG image is based on Intrinsic

optical scattering signal is backscattered by moving blood cells in blood vessel.

Using spectral interferogram. cortical blood perfusion in the brain of small animals

and blood flow within human retina and choroid.

FEATURES Noninvasive and label free technique. Great value of resolution. Biomedical research, clinical diagnostics,

treatment of diseases. Accurate resolution micro vascular network. Simple imaging technique. Portable and easy to install.

WORKING PRINCIPLE OF OMAG Spatial frequency analysis. Separate signals that are backscattered by

moving particle(blood cells) and stuck particle(tissues).

And mathematically map and simultaneously.

Spectral interferogram to full range complex image.

The result is high resolution mapping dynamic capillary level resolution.

Avail micro structural image.

ADVANTAGES

In vivo Not using radio active medicine Highly accurate. Imaging up to capillary level. 3D information. Easy calculations. High speed Portable etc.

THEORITICAL ASPECTS Fourier transform to separate the optical (back scattered moving and stuck )signals.

Hilbert transform to discriminate the direction of moving blood cells.

In Fourier domain optical coherent transform(FDOCT) the spectral interference signal formed.

For using ultra high speed spectrometer ,between reference light and back scattered light.

CCD camera receives the dispersed optical signal.

FREQUENCY COMPONENT OF THE TISSUE SAMPLE

Fig. 1. Diagram of frequency components for different tissue sample. (A) Idealtissue sample (optically homogeneous sample) with no moving particles.(B) Real tissue sample (optically heterogeneous sample) with no moving particles.(C) Real tissue sample (optically heterogeneous sample) with movingparticles

MATHEMATICAL CALCULATION

Camera wavelength is λ. Assume wave numbers broad light source are k0 to

k0 +Δk, where k0 = 2π/λ0. each pixel can be written as a function of ki (i = 1,

2, . . ., N). as a function of ki (i = 1, 2, . . ., N) I(ki, t)DFlow = 2S(ki)ERa(z1,t1)[cos[2kin(z1, t1 )(z1

− vt)+ j sin[2kin(z1, t1 )(z1 − vt)]. I(ki) is the light intensity captured by the ith detector, S(ki) is the spectral density of the light

source at ki , r is the optical path length for the light travelled in the reference arm

BASIC OMAG

Schematic of the OMAG system used in this study to image thevelocities of blood flow. PC: polarization controller and CCD. The laser diodeemitting the light at 633 nm was used for aiming purposes during imaging.

SYSTEM SETUP A super luminescent diode (SLD) with a central

wavelength of 1310 nm. which provided an axial imaging resolution of∼13 μm in

air. The light was delivered onto a stationary mirror. The light was focused into a sample via an objective

lens. The light backscattered from the sample and reflected

from the reference mirror were recombined by a 2 × 2 optical fiber coupler.

Then was routed to a home-built high-speed spectrometer via the optical circulator.

The spectrometer consisted of a collimator of30 mm focal length, a 1200 lines/mm transmitting grating, an achromatic lens with 100 mm focal length, and a 14-bit, 1024 pixels InGaAs line scan camera.

RESULT AND IMAGING

small animals has proven invaluable in understandingmechanisms of human cerebrovascular diseases and brainmetabolis

ms.Fig. gives the cross-sectional micro structural image of thescanned tissue slice

Fig. indicates that thecurrent OMAG system is capable of imaging blood flowing incapillaries.

imaging results obtained from a corticaltissue volume of 2.2×2.2×1.7mm3 in a livemouse brain

while imaging time was less than ∼25 s

micro vascular blood perfusion was clearly delineated and localizedwithin the tissue volume

Doppler OMAG (DOMAG) To obtain quantitative blood flow information,

we have further advanced OMAG by combining the laser Doppler velocimetry technique with OMAG.

determine the velocities of blood flows within all vessels in the scanned tissue.

OMAG Offers Opportunity to Examine Cerebral Blood Perfusion Changes Globally and in Individual Vessels Over Cortex.

may be a useful tool for the investigation of diseases, where changes in blood perfusion play an important role in etiology,pathogenesis, prognosis, or response to treatments.

(A) OMAG, and (B) DOMAG images

DOMAG to quantify blood flows within scanned tissue.

CBF over the entire cortex of an adult mouse is imaged in vivo with the skull left intact

OMAG Images Human Retinaand Choroids The most recent development in imaging the

ocular blood perfusion in humans is to use phase resolved Doppler OCT.

DOCT uses optical phases in the interference signals to evaluate the blood flow.

Optical phases is very sensitive to the sample movement, optical heterogeneity of tissue

All of these results demonstrate that OMAG delivers superior imaging performance, not only in retina, but also in choroids, including the capability of imaging capillary vessels

OMAG Images the Blood Perfusion Within Human Retinaand Choroids

compared to the imaging results animal brain and the human retina

1) there is inevitable, severe motion in human retina imaging

a better approach than the current phase compensation method is needed to improve the OMAG performance imaging the capillary blood flows within the human retina

2) the capillary vessel density in human retina may be less than in the animal brain.

CONCLUSION high-resolution imaging of blood perfusion within

localized blood vessel. localization of blood perfusion in 3-D microstructures The use of contrast agents and newer imaging agents

administered into blood, for example, nanoparticles and micro bubbles may offer a potential to increase the light backscattered from the moving elements.

Easily implemented in both the hospital and research laboratory environments.

the visualization and quantification of the microcirculation are important for understanding

mechanisms and treatments, e.g., tumour angiogenesi. where ocular and retinal circulatory beds are very important in the diagnosis and

management of disorders, such as glaucoma, diabetic retinopathy, and age-related macular degeneration.

THANK YOU