BLOOD VESSEL STATE EVALUATING DEVICE, BLOOD VESSEL STATE EVALUATING METHOD, AND COMPUTER-READABLE RECORDING MEDIUM STORING BLOOD VESSEL STATE EVALUATING PROGRAM

• US 20100121204A1
• Filed: 03/26/2008
• Published: 05/13/2010
• Est. Priority Date: 03/30/2007
• Status: Active Grant

• Current Assignee: Omron Healthcare Company Limited (Omron Corporation)
• Original Assignee: Omron Healthcare Company Limited (Omron Corporation)
• Inventors: Umeda, Shinya, Sato, Hironori, Ogura, Toshihiko, Utsuno, Hideo, Matsuhisa, Hiroshi
• Granted Patent: US 8,628,476 B2
• Time in Patent Office: Days
• US Class Current: 600/485
• CPC Class Codes: A61B 5/02007 Evaluating blood vessel condition, e.g. elasticity, compliance
• CPC Class Codes: A61B 5/0285 Measuring or recording phase velocity of blood waves
• CPC Class Codes: A61B 5/6824 Arm or wrist
• CPC Class Codes: A61B 5/6828 Leg

Abstract

A phase line tilt calculating unit (actual measurement) receives phase characteristics Pa(f) and Pb(f) outputted from frequency conversion units, and calculates phase difference characteristics of actual measurement based on a phase difference on each frequency component between the phase characteristics. A phase line tilt calculating unit (model) calculates phase difference characteristics between a transfer function Ga(f) and a transfer function Gb(f) calculated by a transfer function calculating unit, and outputs the calculated phase difference characteristics to a search unit. The search unit fits a variable k and determines a variable k_opt (optimum solution) in which a tilt g(k) and a tilt g_exp substantially match each other. The variable k_opt is an index indicating a degree of arterial sclerosis of a subject.

Claims

1. A blood vessel state evaluation device comprising:

a storage unit for storing a circulatory system model in which a blood vessel constituting a living body is divided into a plurality of zones and modeled, the circulatory system model including a shape value representing each of the plurality of zones;

a first measurement unit, attached to a first measurement site of the living body, for measuring a time waveform of a first biological signal;

a second measurement unit, attached to a second measurement site of the living body, for measuring a time waveform of a second biological signal in synchronization with the first measurement unit;

a first calculating unit for calculating a phase difference characteristics of actual measurement based on a phase difference on each frequency component between the first biological signal and the second biological signal;

a second calculating unit for calculating a phase difference characteristics between a first transfer function defined based on the circulatory system model in correspondence to a blood vessel passage to the first measurement site and a second transfer function defined based on the circulatory system model in correspondence to a blood vessel passage to the second measurement site, the first transfer function and the second transfer function including an elasticity variable indicating a degree of elastic force of the blood vessel; and

a search unit for determining the elasticity variable by fitting the phase difference characteristics calculated by the second calculating unit based on the phase difference characteristics of actual measurement calculated by the first calculating unit.

2. The blood vessel state evaluation device according to claim 1, further comprising a transfer function calculating unit for calculating the first and second transfer functions based on the shape value of each zone corresponding to the blood vessel passages to the first and second measurement sites, respectively.

3. The blood vessel state evaluation device according to claim 2, wherein

the transfer function calculating unit calculates the first and second transfer functions using a distribution constant model, having a blood pressure of the blood vessel and a blood flow rate as input variables, corresponding to each zone;

and

each distribution constant model includes a vertical impedance corresponding to easiness in flowing of blood in the corresponding zone, and a horizontal impedance including the elasticity variable.

4. The blood vessel state evaluation device according to claim 1, further comprising a pulse wave velocity calculating unit for calculating a pulse wave velocity in the blood vessel based on the elasticity variable fitted by the search unit.

5. The blood vessel state evaluation device according to claim 4, wherein the pulse wave velocity calculating unit calculates the pulse wave velocity based on the shape value of each zone corresponding to the blood vessel passage to the first measurement site and the shape value of each zone corresponding to the blood vessel passage to the second measurement site.

6. The blood vessel state evaluation device according to claim 1, wherein the circulatory system model includes a blood vessel diameter and a blood vessel length for the shape value.

7. The blood vessel state evaluation device according to claim 1, wherein the circulatory system model is obtained by classifying the blood vessel constituting the living body to a plurality of sections, and then modeling the blood vessel belonging to at least one section of the plurality of sections.

8. The blood vessel state evaluation device according to claim 7, wherein the blood vessel constituting the living body is classified to the plurality of sections based on a size of a blood vessel diameter.

9. The blood vessel state evaluation device according to claim 2, wherein the transfer function calculating unit adds a peripheral part model, in which a blood vessel not modeled in the circulatory system model of the blood vessels contained in each zone is modeled, to the circulatory system model corresponding to each zone, and then calculates the transfer function.

10. The blood vessel state evaluation device according to claim 9, wherein the transfer function calculating unit converts the circulatory system model of each zone based on a shape difference of the blood vessel to calculate the peripheral part model of the zone.

11. The blood vessel state evaluation device according to claim 9, wherein the transfer function calculating unit calculates the transfer function with a terminating end of the peripheral part model under a non-reflection condition.

12. The blood vessel state evaluation device according to claim 1, further comprising:

a first frequency conversion unit for calculating first phase characteristics indicating the phase on each frequency component from the first biological signal; and

a second frequency conversion unit for calculating second phase characteristics indicating the phase on each frequency component from the second biological signal;

wherein

the first calculating unit,

calculates differential phase data by taking a difference of first phase data and second phase data, and

calculates the phase difference characteristics of actual measurement by correcting a phase shift caused by a period delay in the differential phase data in units of phase corresponding to one or more periods.

13. The blood vessel state evaluation device according to claim 1, wherein the first calculating unit calculates the phase difference characteristics of actual measurement using a frequency component in which a coherence value between the first biological signal and the second biological signal is higher than a threshold value defined in advance.

14. A blood vessel state evaluation method for evaluating a state of a blood vessel constituting a living body using a circulatory system model in which the blood vessel constituting the living body is divided into a plurality of zones and modeled, wherein

the circulatory system model includes a shape value representing each of the plurality of zones;

the blood vessel state evaluation method comprising the steps of;

measuring a time waveform of a first biological signal from a first measurement site of the living body and measuring a time waveform of a second biological signal from a second measurement site of the living body;

calculating a phase difference characteristics of actual measurement based on a phase difference on each frequency component between the first biological signal and the second biological signal;

calculating a phase difference characteristics between a first transfer function defined based on the circulatory system model in correspondence to a blood vessel passage to the first measurement site and a second transfer function defined based on the circulatory system model in correspondence to a blood vessel passage to the second measurement site, the first transfer function and the second transfer function including an elasticity variable indicating a degree of elastic force of the blood vessel; and

determining the elasticity variable by fitting the phase difference characteristics between the first transfer function and the second transfer function based on the phase difference characteristics of actual measurement.

15. A computer readable recording medium stored with a blood vessel state evaluation program for evaluating a state of a blood vessel constituting a living body using a circulatory system model in which a blood vessel constituting the living body is divided into a plurality of zones and modeled, wherein

the circulatory system model includes a shape value representing each of the plurality of zones;

a calculation processing unit performing, in response to a command from the program, the steps of;

acquiring a time waveform of a first biological signal at a first measurement site of the living body and acquiring a time waveform of a second biological signal at a second measurement site of the living body;

calculating a phase difference characteristics of actual measurement based on a phase difference on each frequency component between the first biological signal and the second biological signal;

calculating a phase difference characteristics between a first transfer function defined based on the circulatory system model in correspondence to a blood vessel passage to the first measurement site and a second transfer function defined based on the circulatory system model in correspondence to a blood vessel passage to the second measurement site, the first transfer function and the second transfer function including an elasticity variable indicating a degree of elastic force of the blood vessel; and

determining the elasticity variable by fitting the phase difference characteristics between the first transfer function and the second transfer function based on the phase difference characteristics of actual measurement.