Blood vessel detection device and method therefor
A blood vessel detection device comprises: a first irradiation unit for irradiating a predetermined site of a subject with light of a first wavelength that is absorbed less by hemoglobin or water and light of a second wavelength that is absorbed more by hemoglobin or water than the first wavelength; a second irradiation unit for irradiating the predetermined site with light of a third wavelength that is absorbed less by hemoglobin; a light intensity detection unit for detecting the intensity of light emitted from the subject at one or more positions spaced apart by a predetermined distance from the light irradiation positions of the first and second irradiation units or one or more contiguous positions; and a control unit that calculates blood vessel depth information, calculates blood vessel angle information, and determines an optimal position for measurement based on the blood vessel depth information and the blood vessel angle information.
1 . A blood vessel detection device comprising:
a first irradiation unit that irradiates a predetermined position of a subject with a light having a first wavelength with a smaller absorption by hemoglobin or by water and a light having a second wavelength with a larger absorption by hemoglobin or by water than that of the first wavelength;
a second irradiation unit that irradiates the predetermined position of the subject with a light having a third wavelength with a smaller absorption by hemoglobin;
a light intensity detection unit that detects a light intensity at not less than one position, the light intensity emitted from the subject at a predetermined distance or at continuous positions from irradiation positions of the lights from the first irradiation unit and the second irradiation unit; and
a controller that calculates blood vessel depth information based on light intensities of a plurality of wavelengths of either the first wavelength or both of the first wavelength and the second wavelength, calculates blood vessel angle information based on light intensities of not less than one wavelength of either the third wavelength or both of the first wavelength and the third wavelength, and determines a position suitable for measurement based on the blood vessel depth information and the blood vessel angle information.
2 . The blood vessel detection device according to claim 1 , wherein
the first wavelength is 750 nm or more and 850 nm or less, and the second wavelength is 500 nm or more and 600 nm or less, or 900 nm or more and 1200 nm or less.
3 . The blood vessel detection device according to claim 1 , wherein the third wavelength is 650 nm or more.
4 . The blood vessel detection device according to claim 1 , wherein the controller calculates the blood vessel depth information from Arithmetic expression 1 or Arithmetic expression 2,
(
blood
vessel
depth
information
)
∝
(
Arithmetic
expression
1
)
=
(
μ
eff
λ
2
μ
eff
λ
1
)
2
≅
μ
a
λ
2
μ
a
λ
1
[
Formula
12
]
where, in Arithmetic expression 1, μeff is an effective attenuation coefficient, λ1 and λ2 are the first wavelength, and μa is an absorption coefficient,
(
blood
vessel
depth
information
)
∝
(
Arithmetic
expression
2
)
=
1
-
(
μ
eff
λ
4
μ
eff
λ
3
-
1
)
(
μ
a
_
blood
λ
4
μ
a
_
blood
λ
3
-
1
)
[
Formula
13
]
where in Arithmetic expression 2, μeff is the effective attenuation coefficient, λ3 is the first wavelength, λ4 is the second wavelength, and μa is the absorption coefficient.
5 . The blood vessel detection device according to claim 1 , wherein the controller calculates the blood vessel angle information from Arithmetic expression 3 or Arithmetic expression 4,
(
blood
vessel
angle
information
)
=
(
Arithmetic
expression
3
)
=
I
5
λ
5
I
6
λ
5
[
Formula
14
]
where in Arithmetic expression 3, I n (n is the number of the light intensity detection units) is a light intensity detected by a nth light intensity detection unit, and λ5 is the third wavelength,
(
blood
vessel
angle
information
)
=
(
Arithmetic
expression
4
)
=
CV
μ
eff
λ
7
CVI
5
λ
6
[
Formula
15
]
where in Arithmetic expression 4, a numerator is a coefficient of variation CV of the effective attenuation coefficient μeff, a denominator is a coefficient of variation CV of the detected light intensity I n (n is the number of the light intensity detection units), λ6 is the third wavelength, and λ7 is the first wavelength.
6 . The blood vessel detection device according to claim 1 , wherein the irradiation unit has a direction regulation unit for enhancing rectilinear propagation of the irradiation light, on an irradiation surface of the irradiation unit, and the direction regulation unit includes a pinhole or a lens.
7 . A blood vessel detection method comprises:
irradiating a predetermined position of a subject with a light having a first wavelength with a smaller absorption by hemoglobin or by water, a light having a second wavelength with a larger absorption by hemoglobin or by water than that of the first wavelength, and a light having a third wavelength with a smaller absorption by hemoglobin;
detecting a light intensity at not less than one position, the light intensity emitted from the subject at a predetermined distance or at continuous positions from irradiation positions of the lights;
calculating blood vessel depth information based on light intensities of a plurality of wavelengths of either the first wavelength or both of the first wavelength and the second wavelength;
calculating blood vessel angle information based on not less than one light intensity of either the third wavelength or both of the first wavelength and the third wavelength; and
determining a position suitable for measurement based on the blood vessel depth information and the blood vessel angle information.