An Instrument Using an Optical Sensor for Measuring Dye Disappearance in Blood and Its Clinical Evaluation for Hepatic Diseases

An instrument to measure hepatic function was developed as a medical application of optoelectronic technology. The study of Indocyanine green (ICG) clearance in blood is clinically used for the estimation of hepatic function. Multiple blood samplings, however, subject the patients to mental and physical stress. Furthermore, although it is necessary with this method to correctly measure the blood sampling time after ICG injection, it is difficult to accurately measure this time in an actual test. Thus, a measuring method without blood sampling has been desired. Although some preliminary studies employing a non-invasive method were undertaken, there were still problems for clinical usage. Therefore, in this paper, a description of an instrument for the non-invasive measurement of ICG clearance using an optical sensor attached to the fingertip is presented, and a calibration method before ICG injection is proposed to solve the problem of changing blood volume. Next, the results of the clinical evaluation of 470 cases are presented. Using this newly developed instrument, the values of ICG tests correlated well with the values calculated from the conventional blood sampling method.