Liver function testing apparatus

• US 5,154,176 A
• Filed: 11/26/1991
• Issued: 10/13/1992
• Est. Priority Date: 09/14/1988
• Status: Expired due to Fees

• Current Assignee: Sumitomo Electric Industries Limited (Sumitomo Corporation)
• Original Assignee: Sumitomo Electric Industries Limited (Sumitomo Corporation)
• Inventors: Kanda, Masahiko
• Primary Examiner(s): Smith, Ruth S.
• Application Number:
  US07/800,865
• Time in Patent Office: 322 Days
• Field of Search: 128/632, 128/633, 128/665, 128/666
• US Class Current: 600/479
• CPC Class Codes: A61B 5/0059 using light, e.g. diagnosis by transillumination, diascopy, fluorescence A61B5/0093, A61B5/1455, A61B5/02416 and A61B5/0261 take precedence
• CPC Class Codes: A61B 5/4244 liver

Abstract

A liver function testing apparatus measures n-times the values ΔlogT₁ and ΔlogT₂ corresponding to pulse wave signals obtained upon passage through a prescribed optical path in vital tissue. A sensor (30) having first and second light sources (3, 4) and a light receiving element (6) is attached to a testee (5) before injection of a specific dye. A value α₀ is calculated by using a statistical computation with two variables as to n ΔlogT₁ and ΔlogT₂ on the basis of an equation of ΔlogT₁ =α₀.ΔlogT₂.ΔlogT₁ and ΔlogT₂ corresponding to pulse wave signals are measured in response to intensity levels of first light and second light passing through the vital tissue during a prescribed time following an injection on the basis of decision outputs representing levels of the first light and the second light from the light sources after the specific dye is injected. A value Cg corresponding to a specific dye concentration in the blood is calculated from α₀ , ΔlogT₁ and ΔlogT₂. A simulation curve as a function of time changes of the result of the measurements is calculated by the application of the least squares method, thereby to obtain a blood plasma disappearance rate K and a T-minute retention rate R % of the specific dye on the basis of the simulation curve.

Claims

1. An apparatus for testing a liver to provide liver function information, comprising

(a) first light source means (3) for exposing vital tissue of a patient to a first light having a first wavelength (λ

₁) substantially absorbed by a specific dye removable by the liver and dosed into blood flowing through said vital tissue, and second light source means (4) for exposing said vital tissue to a second light having a second wavelength (λ

₂) substantially not absorbed by said specific dye,

(b) light receiving sensor means (6) positioned for detecting said first light and said second light after passing through said vital tissue,

(c) signal processing means for processing signals received from said light receiving sensor means,

(c1) said signal processing means including logarithmic circuit means (8) connected for receiving light intensity values from said light receiving sensor means (6) for logarithmically converting said light intensity values (T₁) of said first light and (T₂) of said second light detected by said light receiving sensor means (6) to form logarithmic signals log T₁ and log T₂,

(c2) sample and hold circuit means (9) connected to said logarithmic circuit means (8) for separating said logarithmic signals according to said first and second light wavelengths (λ

₁ and λ

₂), and

(c3) filter means (10,

     11) connected to said sample and hold circuit means (9) for setting maximum and minimum signal limits for forming signal values Δ

log T₁ and Δ

log T₂ prior to injecting said specific dye,

(d) a central processing unit (CPU) connected to said signal processing means for performing arithmetic operations,

(d1) said central processing unit including first arithmetic circuit means for calculating α

₀ from said signal values Δ

log T₁ divided by Δ

log T₂, said calculating being performed repeatedly as a statistical computation prior to a dye injection,

(d2) timing means for indicating a time for injecting said specific dye,

(d3) second arithmetic circuit means for providing signal values Δ

log T₁ (i) and Δ

log T₂ (i) during a fixed length of time following an injection of said specific dye, where i is a number from l to n,

(d4) third arithmetic circuit means for calculating α

from said signal values Δ

log T₁ (i) divided by Δ

log T₂ (i), said calculating being performed repeatedly as a statistical computation after a dye injection,

(d5) fourth arithmetic circuit means for calculating a specific dye concentration C_g based on said α

₀ and α

which represent changes in absorption quantities prior to and after injection of said specific dye, respectively,

(d6) fifth arithmetic circuit means for calculating in accordance with the least squares method from said specific dye concentration C_g, a simulation curve representing calculation results which are changing with time, and

(d7) sixth arithmetic circuit means for evaluating a blood plasma disappearance rate K and a T-minute retention rate R% of said specific dye based on said simulation curve,

(e) output means (17,

     18) connected to said central processing unit (CPU) for outputting liver function information obtained by said central processing unit, and

(f) light level setting means (2) connecting an output of said central processing unit to said first and second light source means (3,

     4) for adjusting light level limits for light emitted by said first and second light source means in response to signals received from said light receiving sensor means (6) prior to injection of said specific dye into a patient.

2. The apparatus of claim 1, wherein said first arithmetic means for calculating α

₀ prior to a dye injection include means for measuring Δ

log T₁ and Δ

log T₂ n times for calculating values C_g (t), assuming that Δ

log T₁ and Δ

log T₂ represent values corresponding to pulse wave signals expressing intensity levels of said first light and of said second light, and wherein said third arithmetic means for calculating α

after a dye injection includes means for forming α

(t) from n×

2 measurements by using a statistical computation based on two variables of Δ

log T₁ =α

(t).Δ

log T₂, and for obtaining;

space="preserve" listing-type="equation">C.sub.g (t)=β

(α

(t)-α

.sub.0)

where β

represents a constant.

3. The apparatus of claim 1, wherein said simulation curve for said specific dye concentration C_g calculated

by said fifth arithmetic circuit means is:

space="preserve" listing-type="equation">C.sub.g =A.e.sup.Bt

where

C_g ;

is a value of a specific dye concentration in blood,

t;

is the elapsed time in minutes after injection of said specific dye,

A, B;

are constants, and

wherein said sixth arithmetic circuit means for evaluating said blood plasma disappearance rate K and said T-minute retention rate R% operate on the basis of K=-B and R% =e^Bt wherein an elapsed time (t) is T-minutes following an injection of said specific dye, for expressing an intake of said specific dye in the liver.

4. The apparatus of claim 1, wherein both said first and third arithmetic circuit means for calculating α

₀ and α

respectively comprise means for performing a regression analysis.