Orthogonal polarization spectral imaging
Encyclopedia
Orthogonal polarization spectral imaging is a method for imaging small blood vessel
s in tissue like the nail bed or lip.
It uses a light source of linearly
polarized light with a wavelength of 550 nanometers, the isobestic point for hemoglobin
, thus imaging the erythrocytes as they are flowing through the small blood vessels. The reflected light orthogonal (at a 90° angle) to the emitted light is recorded, thus eliminating direct reflections. The depolarized light forms an image of the microcirculation on a CCD
, which can be captured through single frames or on videotape. The image produced is as if the light source is actually placed behind the desired target or transilluminated.
It has been validated, even under low hematocrit
circumstances.
Blood vessel
The blood vessels are the part of the circulatory system that transports blood throughout the body. There are three major types of blood vessels: the arteries, which carry the blood away from the heart; the capillaries, which enable the actual exchange of water and chemicals between the blood and...
s in tissue like the nail bed or lip.
It uses a light source of linearly
Linear polarization
In electrodynamics, linear polarization or plane polarization of electromagnetic radiation is a confinement of the electric field vector or magnetic field vector to a given plane along the direction of propagation...
polarized light with a wavelength of 550 nanometers, the isobestic point for hemoglobin
Hemoglobin
Hemoglobin is the iron-containing oxygen-transport metalloprotein in the red blood cells of all vertebrates, with the exception of the fish family Channichthyidae, as well as the tissues of some invertebrates...
, thus imaging the erythrocytes as they are flowing through the small blood vessels. The reflected light orthogonal (at a 90° angle) to the emitted light is recorded, thus eliminating direct reflections. The depolarized light forms an image of the microcirculation on a CCD
Charge-coupled device
A charge-coupled device is a device for the movement of electrical charge, usually from within the device to an area where the charge can be manipulated, for example conversion into a digital value. This is achieved by "shifting" the signals between stages within the device one at a time...
, which can be captured through single frames or on videotape. The image produced is as if the light source is actually placed behind the desired target or transilluminated.
It has been validated, even under low hematocrit
Hematocrit
The hematocrit or packed cell volume or erythrocyte volume fraction is the percentage of the concentration of red blood cells in blood. It is normally about 45% for men and 40% for women...
circumstances.