Optical analysis of the cirrhotic liver by near-infrared time-resolved spectroscopy

Purpose. To assess the histological severity of liver cirrhosis in relation to the optical properties of liver tissue. Methods. Various grades of liver cirrhosis were induced in rats by giving intraperitoneal injections of thioacetamide (TAA) over periods ranging from 4 to 16 weeks. The optical properties of the liver, absorption coefficient (mu(a)) and scattering coefficient (mu(s)'), were measured by near-infrared time-resolved spectroscopy. Results. Histological examination confirmed cirrhotic changes in the liver, which were more severe in the rats given TAA for longer periods. The mu(a) increased in the 4- and 8-week rats, then decreased in the 12- and 16-week rats. The mu(a) of the blood-free liver decreased as liver cirrhosis progressed. The hemoglobin concentration in the liver, calculated from the mu(a) values, increased in the 4- and 8-week rats and decreased in the 12- and 16-week rats. The mu(s)' decreased in the cirrhotic liver, probably reflecting the loss of volume of hepatocytes. The product of mu(a) and mu(s)' proved useful to evaluate the severity of cirrhosis. Conclusions. These results showed that the optical properties correlated well with the severity of liver cirrhosis, indicating that the clinical application of this method is encouraging.