Hepatic extraction fraction (HEF):
The hepatic extraction fraction (HEF) is defined by the extraction of tracer by the liver and reflects hepatocyte function (ie: the efficiency of extraction of the radiotracer from the blood). It can be assessed visually or quantitatively. Visual inspection is usually adequate, but quantification may be required iun equivocal cases. The HEF is calculated by the ratio of the initial hepatocyte uptake divided by the peak vascular uptake:
HEF = (y intercept exponential fit liver response curve)
y max data value liver response curve
The normal HEF in the pediatric population is greater than 92%
J Nucl Med 1998; Howman-Giles R, et al. Hepatobiliary scintigraphy in infancty. 39: 311-319
