Hepatic extraction fraction of hepatobiliary radiopharmaceuticals measuredusing spectral analysis

Measuring the hepatic extraction fraction (HEF) of a hepatobiliary radiopha rmaceutical helps to differentiate hepatocyte from biliary tract diseases, and it is generally performed using deconvolution analysis. In this study, we measured HEF using spectral analysis. With spectral analysis, HEF was ca lculated from (the sum of the spectral data obtained by spectral analysis - the highest frequency component of the spectrum) divided by (the sum of th e spectral data) x 100 (%). We applied this method to dynamic liver scintig raphic data obtained from six healthy volunteers and from 46 patients with various liver diseases, using Tc-99(m)-N-pyridoxyl-5-methyltryptophan (PMT) . We also measured HEF using deconvolution analysis, in which the modified Fourier transform technique was employed. The HEF values obtained by spectr al analysis correlated closely with those obtained by deconvolution analysi s (r = 0.925), suggesting our method is valid. The HEF values obtained by s pectral analysis decreased as the severity of liver disease progressed. The values were 100.0 +/- 0.0%, 94.7 +/- 13.6%, 76.2 +/- 27.4%, 45.7 +/- 15.6% , 82.7 +/- 24.2% and 95.2 +/- 11.8% (mean +/- S.D.) for the normal controls (n = 6), mild liver cirrhosis (n = 16), moderate liver cirrhosis (n = 11), severe liver cirrhosis (n = 5), acute hepatitis (n = 8) and chronic hepati tis groups (n = 6), respectively. The HEF was obtained more simply and rapi dly by spectral analysis than by deconvolution analysis. The results sugges t that our method using spectral analysis can be used as an alternative to the conventional procedure using deconvolution analysis for measuring HEF ( (C) 1999 Lippincott Williams & Wilkins).