LIVER FUNCTION TESTING APPARATUS

In a liver function testing apparatus, light sources (11, 12) expose vital tissue (15) to first light of a wavelength absorbed by the specific dye dosed into blood of the vital tissue to be taken in and removed by the liver and second light of a wavelength not absorbed by the dye. Optical pulses passing through the vital tissue are received by a light receiving element (13) and first and second outputs from element (13) are sampled by an A-D converter (30) to produce respective digital signals. Pulsation components of the outputs of the receiving light are detected by high-pass filters (51, 52) and amplifiers (53, 54). A coefficient of a linear regression expression between intensity values of the pulsation components and an average value using the sampled first and second outputs of the received light are determined for performing a biocalibration. A value correlated with a specific dye concentration in the blood is calculated based on sampling outputs during a prescribed period and based on the determined average value after injection of the specific dye. Thus, a coefficient of a simulation function as a time function, is obtained by using the method of least squares and a blood plasma disappearance rate and a retention rate are obtained on the basis of the coefficient of the simulation.