Surgery – Diagnostic testing – Detecting nuclear – electromagnetic – or ultrasonic radiation
Reexamination Certificate
1999-11-22
2003-02-18
Lateef, Marvin M. (Department: 3737)
Surgery
Diagnostic testing
Detecting nuclear, electromagnetic, or ultrasonic radiation
C600S476000, C600S310000, C356S319000, C356S450000, C356S484000
Reexamination Certificate
active
06522911
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates generally to an apparatus for imaging and displaying a blood vessel, and more particularly to an apparatus for imaging and distinguishing an artery from a vein or vice versa.
2. Description of the Related Art
In clinical diagnosis, there have been wide demands for imaging and discriminating an artery from a vein or vice versa. For example, arteriosclerosis generally arises from a peripheral portion. Therefore, if the inside diameter image of the artery in this peripheral portion can be discriminated from a venous image and imaged, it can be utilized as diagnostic information with respect to arteriosclerosis.
As an apparatus for imaging and displaying a blood vessel, an X-ray blood vessel contrast photographing apparatus has hitherto been widely known. However, this X-ray blood vessel contrast photographing places a great burden on a subject and the execution thereof usually requires admission to a hospital, so there is a problem that it is difficult to easily perform the X-ray blood vessel contrast photographing on an outpatient.
In contrast to this, a technique of imaging a part of a living organism by light fluoroscopy has also been proposed as indicated in Medical Society Journal of Japan, BME Vol. 8, No. 5, 1994, pp. 41-50. In this imaging technique by light fluoroscopy, however, it is extremely difficult to clearly image and distinguish an artery-from a vein or vice versa.
SUMMARY OF THE INVENTION
The present invention has been made in view of the aforementioned circumstances. Accordingly, it is an object of the present invention to provide an apparatus which places a lower burden on a subject and is capable of imaging and distinguishing an artery from a vein or vice versa.
A blood vessel imaging apparatus according to the present invention applies optical heterodyne detection to imaging such that high space resolution is ensured with respect to a living organism which is a scattering medium, and distinguishes an artery and vein by taking advantage of a difference in light absorption characteristic between oxyhemoglobin and deoxyhemoglobin in the blood.
More specifically, the blood vessel imaging apparatus according to the present invention comprises:
light source means for emitting a first measuring light beam and a second measuring light beam differing from the first measuring light beam, the first measuring light beam having a wavelength equal to a wavelength at an isosbestic point between oxyhemoglobin and deoxyhemoglobin in the blood of a living organism;
an incident optics system for causing the first measuring light beam and the second measuring light beam to be incident on the same part of the living organism;
scanner means for scanning the living organism with the first measuring light beam and the second measuring light beam;
a first optical heterodyne detection system equipped with a first optics system for synthesizing the first measuring light beam and a branched first measuring light beam transmitted through the living organism; a first frequency shifter for giving a difference in frequency between the first measuring light beam and the branched first measuring light beam; and first detection means for detecting a first beat component of the synthesized first measuring light beam and outputting a first beat component detection signal;
a second optical heterodyne detection system equipped with a second optics system for synthesizing the second measuring light beam and a branched second measuring light beam transmitted through the living organism; a second frequency shifter for giving a difference in frequency between the second measuring light beam and the branched second measuring light beam; and second detection means for detecting a second beat component of the synthesized second measuring light beam and outputting a second beat component detection signal; and
image signal generation means for generating an image signal, based on a value of the second beat component detection signal normalized by the first beat component detection signal.
In a preferred form of the present invention, the light source means emits a light beam of wavelength &lgr;
1
as the first measuring light beam and emits a light beam of wavelength &lgr;
2
as the second measuring light beam, and when it is assumed that a value of a beat component detection signal related to the measuring light beam of wavelength &lgr;
1
is I&lgr;
1
and a beat component detection signal related to the measuring light beam of wavelength &lgr;
2
is I&lgr;
2
, the image signal generation means generates the image signal, based on a value of log(I&lgr;
2
/I&lgr;
1
).
The wavelength &lgr;
1
of the first measuring light beam may be 805 nm and the wavelength &lgr;
2
of the second measuring light beam may be 760 nm. Also, the wavelength &lgr;
1
may be 805 nm and the wavelength &lgr;
2
may be 930 nm.
In another preferred form of the present invention, the light source means emits a light beam of wavelength &lgr;
1
as the first measuring light-beam and emits a light beam of wavelength &lgr;
2
and a light beam of wavelength &lgr;
3
as the second measuring light beam, and when a value of a beat component detection signal related to the measuring light beam of wavelength &lgr;
1
is assumed to be I&lgr;
1
, a beat component detection signal related to the measuring light beam of wavelength &lgr;
2
to be I&lgr;
2
, and a beat component detection signal related to the measuring light beam of wavelength &lgr;
3
to be I&lgr;
3
, the image signal generation means generates the image signal, based on a difference between a value of log(I&lgr;
2
/I&lgr;
1
) and a value of log(I&lgr;
3
/I&lgr;
1
).
In the case of employing three kinds of measuring light beams, as described above, the wavelengths &lgr;
1
, wavelength &lgr;
2
, and the wavelength &lgr;
3
are, for example, 805 nm, 760 nm, and 930 nm.
In still another preferred form of the present invention, the blood vessel imaging apparatus according to the present invention further comprises synchronous detection means for detecting a pulse wave of the artery of the living organism and performing the beat component detection of the first and second measuring light beams in synchronization with a predetermined phase of the pulse wave.
The arterial blood of a living organism includes oxyhemoglobin dominantly, while the venous blood includes deoxyhemoglobin dominantly.
FIG. 6
shows the absorption spectra of oxyhemoglobin and deoxyhemoglobin that are light-absorbing materials, along with the spectrum of water that determines the optical characteristics of the tissues of the human body. As shown in the figure, the spectrum of oxyhemoglobin has a characteristic of low absorption on the short wavelength side of the isosbestic point (wavelength 805 nm), while the spectrum of deoxyhemoglobin has a characteristic of low absorption on the long wavelength side of the isosbestic point.
On the other hand, the beat component detection signals, output by the above-mentioned first and second optical heterodyne detection systems, indicate the intensities of only the straight light portion transmitted through the living organism and the scattered light portion close thereto, excluding the influence of scattering of the living organism that is a scattering medium. The value of the beat component detection signal will become greater if absorption of the measuring light beam is less.
Hence, in consideration of the absorption spectra of
FIG. 6
, consider the case of using a light beam of wavelength &lgr;
1
=805 nm equal to the isosbestic point wavelength as the first measuring light beam and using, for example, a light beam of &lgr;
2
=760 nm (where the absorption of deoxyhemoglobin is particularly greater with respect to the absorption of oxyhemoglobin) as the second measuring light beam.
If, in the above case, the first and second measuring light beams are transmitted through the venous part in which deoxyhemoglobin is dominantly included, the second beat component detection signal t
Sato Tomoo
Toida Masahiro
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