LIMITATIONS OF MAGNETIC-RESONANCE-IMAGING IN MEASUREMENT OF HEPATIC IRON

To evaluate the usefulness of magnetic resonance imaging for the quant itative determination of hepatic iron, we examined 43 patients with th alassemia major and assessed the influence of pathologic changes in th e liver on the precision of estimates of the hepatic iron concentratio n. Tissue signal intensities were measured from magnetic resonance T1- weighted images derived from gradient-echo (GE) pulse sequences and th e ratio of the signal intensity of liver to muscle calculated. By excl uding patients (n = 9) having a signal intensity ratio (SIR) less than or equal to 0.2, a linear relationship with hepatic iron was found an d subsequent analyses were limited to these 34 patients. In 27 patient s with hepatic fibrosis, an overall correlation of -0.848 was found be tween hepatic iron and SIR. By contrast, in the seven patients with no fibrosis. the correlation coefficient (-0.993) was significantly grea ter (P <.0001). Despite the differences in correlation, the regression line between hepatic iron and SIR for the patients with no fibrosis d id not differ significantly with respect to either slope or intercept from that of the patients with fibrosis. Thus, the presence of fibrosi s did not seem to affect the pattern of the relationship between hepat ic iron and the SIR, but rather to increase the variability of the rel ationship. Clinically, the presence of fibrosis makes estimates of hep atic iron derived from magnetic resonance imaging so variable as to be of little practical use in the management of transfusional iron overl oad. (C) 1997 by The American Society of Hematology.