Surgery – Diagnostic testing – Detecting nuclear – electromagnetic – or ultrasonic radiation
Reexamination Certificate
2000-02-01
2003-04-29
Lateef, Marvin M. (Department: 3737)
Surgery
Diagnostic testing
Detecting nuclear, electromagnetic, or ultrasonic radiation
C600S428000, C600S310000, C600S476000, C600S500000, C600S502000, C600S504000, C356S319000, C356S450000, C356S484000, C356S027000, C356S028000, C356S028500
Reexamination Certificate
active
06556854
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a blood vessel imaging system for imaging blood vessels, and more particularly to a blood vessel imaging system which can image blood vessels with arteries and veins distinguished from each other. This invention also relates to a system for distinguishing arteries and veins from each other. This invention further relates to a system for measuring a frequency deviation of a measuring light beam, which has been irradiated to a scattering fluid for blood vessel imaging, or the like, due to a Doppler effect.
2. Description of the Related Art
In the clinical field, there has been a wide demand for imaging arteries and veins clearly distinguished from each other. For example, since arteriosclerosis generally starts at the periphery of the arteries, it will be useful in diagnosing arteriosclerosis if the inner walls of the peripheral arteries can be imaged distinguished from those of the veins.
There has been wide known angiography as a system for imaging blood vessels. However angiography is invasive, e.g., it involves administration of a contrast medium to the testee, which gives the testee causalgia and involves insertion of a catheter into an artery, and accordingly, it is difficult to perform angiography without staying the testee in the hospital.
Further there has been proposed technique for imaging a part of an organism on the basis of penetration of light through the part as disclosed in “IEEE Journal of Selected Topics in Quantum Electronics”, Vol. 2, p1008, 1996. In this imaging method, a light beam is projected onto a finger and light which travels straight through the finger while scattered in multiple scattering in the finger is detected by optical heterodyne detection. Then a cross-sectional image of the finger is obtained by use of a method of image reconstitution which has been employed in computed tomography. However, it has been impossible to recognize existence of a blood vessel by this method.
Further, there has been proposed technique in which the hollow of a hand is illuminated by light emitted from a plurality of LEDs and an image of blood vessels on the back side of the hand formed by light scattered inside the hand is taken as animation by a sensitive TV camera as disclosed in “Japanese ME Academy Magazine BME”, vol.8, No.5, pp.41, 1994. However, only subcutaneous veins or blood vessels in a relatively shallow part of the hand can be imaged by the technique and it is impossible to image arteries and veins clearly distinguished from each other by the technique.
SUMMARY OF THE INVENTION
In view of the foregoing observations and description, the primary object of the present invention is to provide a blood vessel imaging system which can image peripheral blood vessels such as peripheral arteries and the like in a relatively deep part of the hand or foot with the blood vessels clearly distinguished from other soft tissues and can image blood vessels with arteries and veins clearly distinguished from each other without exposing the testee to heavy load.
Another object of the present invention is to provide a system which can clearly distinguish arteries and veins from each other without exposing a testee to heavy load.
The specific object of the present invention is to provide a system which can measure a frequency deviation of a measuring light beam, which has been irradiated to a scattering fluid, due to a Doppler effect.
In blood vessel imaging systems in accordance with one aspect of the present invention, a blood vessel is basically imaged by projecting a measuring light beam onto an organism and detecting light scattered by the organism. A light homodyne detection system is applied in detecting the scattered light, thereby distinguishing an artery and a vein from each other on the basis of difference in flow rate of the blood between the artery and the vein. Further by combining the light homodyne detection system with an optical heterodyne detection system, the beat components of light detected by the light homodyne detection system are amplified.
That is, in accordance with a first aspect of the present invention, there is provided a blood vessel imaging system comprising
a measuring light source which emits a measuring light beam,
an optical homodyne interference system which splits first and second light beams from the measuring light beam, causes the first and second light beams to impinge upon the same irradiating point on an organism in different directions, and combines together the first and second light beams scattered at the irradiating point into a combined scattered light beam,
a scanning means which causes the first and second light beams to scan the organism,
an optical heterodyne detection system consisting of an optical heterodyne interference system which splits a third light beam from the measuring light beam and combines the third light beam with the combined scattered light beam emanating from the optical homodyne interference system into a combined output light beam, a frequency shifter which causes a frequency difference between the third light beam and the first and second light beams, and a beat component detecting means which detects beat components of the combined output light beam and outputs a beat component detection signal, and
an image signal generating means which generates an image signal on the basis of the frequency of the beat components, generated by the optical homodyne interference system, included in the beat component detection signal output from the optical heterodyne detection system.
For example, the image signal generating means generates an image signal representing artery parts of the organism when the frequency of the beat components generated by the optical homodyne interference system is higher than a predetermined threshold value, and generates an image signal representing vein parts of the organism when the frequency of the beat components generated by the optical homodyne interference system is not higher than the predetermined threshold value.
It is preferred that the blood vessel imaging system be provided with a position adjustment means which adjusts the positions of the organism and the optical homodyne interference system relative to each other to change the directions of incidence to the irradiating point of the first and second light beams.
It is preferred that the blood vessel imaging system be provided with an in-phase time detecting means for detecting in-phase times, at which the flow rate of blood in the blood vessel to be imaged becomes a predetermined value, and outputting a timing signal, and the image signal generating means samples the beat component detection signal at times, at which the flow rate of the blood is substantially maximized, on the basis of the timing signal and generates the image signal on the basis of the sampled beat component detection signal.
The in-phase time detecting means may be, for instance, a means for detecting the pulse wave of the organism, or a means for detecting the times at which the frequency of the beat components generated by the optical homodyne interference system takes a peak value.
When fluid is flowing in the irradiating point upon which the first and second light beams impinge in different directions, the frequencies of the first and second light beams scattered at the irradiating point are deviated by a Doppler effect.
Assuming, for the purpose of simplicity, that one of the first and second light beams passes through one of two points on a plane facing the organism and travels along an optical path passing through the optical axis after scattered and reflected by the organism and the other of the first and second light beams passes through the other of two points and travels along an optical path passing through the optical axis after scattered and reflected by the organism, frequency deviation of said one of the first and second light beams is &Dgr;f and that of the other is −&Dgr;f when the reflecting point has a velocity component. When the scattered fir
Sato Tomoo
Toida Masahiro
Tsujita Kazuhiro
Fuji Photo Film Co. , Ltd.
Lateef Marvin M.
Pass Barry
Sughrue & Mion, PLLC
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