The effect of liver iron deposition on hepatic apparent diffusion coefficient values in cirrhosis.

OBJECTIVE: The purpose of this study was to assess the effect of hepatic iron deposition on apparent diffusion coefficient (ADC) values measured with single-shot echo-planar imaging (EPI) diffusion-weighted MRI (DWI) in patients with liver cirrhosis and in vitro.

MATERIALS AND METHODS: Fifty-two patients with liver cirrhosis who underwent breath-hold single-shot EPI DWI at 1.5 T before liver transplantation were retrospectively assessed. Estimated signal-to-noise ratio (SNRest) and ADC were measured in the right hepatic lobe (for b values of 50 and 500 s/mm2). SNRest and ADC were compared between patients stratified by pathologic iron grade using the Mann-Whitney test. Hepatic ADC values were correlated to T2* values using the Spearman correlation test in a subset of patients. In addition, a phantom consisting of solutions of varying iron concentrations was imaged with single-shot EPI DWI and T2* imaging, and iron concentration was correlated with ADC and T2*.

RESULTS: In phantoms, there was a decrease in ADC and T2* with increasing iron concentration (r=-0.95 and -0.92, respectively; p<0.05). Patients with hepatic siderosis had significantly lower SNRest and ADC compared with patients without siderosis (p<0.0001). SNRest at b=50 s/mm2 and b=500 s/mm2 and ADC had a significant negative correlation with pathologic iron grade (r=-0.67 to 0.77, p<0.0001). There was a significant correlation between liver T2* and ADC (r=0.83, p<0.0001).

CONCLUSION: Hepatic siderosis lowers liver ADC and should be taken into account when using ADC for diagnosing liver cirrhosis.