Short coherence length doppler velocimetry system

Abstract

Apparatus for measuring the speed of blood in blood vessels in biological samples, for example, in retinal blood vessels, which apparatus includes: (a) a source of a beam of radiation having a principal wavelength, which radiation is substantially spatially coherent and has a temporal coherence length which is less than 1 picosecond; (b) a beam splitter for splitting the beam into a sample beam and reference beam; (c) optical apparatus for directing the sample beam to an area within the biological sample; (d) a reflector for reflecting the reference beam; (e) a detector for detecting an interference between the sample beam reflected from the area and the reflected reference beam and for generating an interference signal; (f) apparatus for altering an optical path length of the reference beam from the beam splitter to the detector at an alteration velocity; and (g) an analyzer for analyzing the interference signal to determine the speed of the blood in the area from a shift of a central frequency of a frequency spectrum of the interference signal from a frequency determined from the alteration velocity and the principal wavelength.

Description

technical field [0001] The invention relates to a short coherence length Doppler velocity measurement system. Background technique [0002] The human retina is sensitive to changes in the blood flow provided by the retinal vasculature. Such changes in blood flow, which may (a) result from specific ophthalmic disorders, such as vascular occlusion, or (b) occur with systemic diseases, such as diabetes or systemic hypertension, often lead to blindness. In view of this, an efficient and reproducible method for measuring blood flow in the retina is important for the diagnosis and treatment of retinal vascular diseases. [0003] Several instruments are known in the art for measuring / estimating blood flow velocity in the retina, but all have one or more disadvantages. One such prior art instrument is an ultrasound imaging system which measures the Doppler shift of reflected waves. Ultrasound imaging systems use the first technique to provide the user with output in a format know...

AI Technical Summary

Problems solved by technology

However, the standard LDV technique has several disadvantages

First, LDV technology has the disadvantage that it cannot provide three-dimensional positioning

Second, the LDV technique has a disadvantage that it simultaneously measures all blood flow velocities in a vessel (as we all know, the blood flow velocity is the fastest in the center of the vessel and the slowest in the vessel wall)

Third, the disadvantage of the LDDV technique is that it contains multiple scattering artifacts

Fourth, one disadvantage of LDV technology is that it relies on the reflection of the blood vessel wall as a "local oscillator" (the blood vessel wall provides a strong non-Doppler frequency shifted reference beam)

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