Real-Time Tissue Elastography: A Noninvasive Technique to Evaluate Liver Damage after Brain Death in Animal Mode

Using brain-dead donors to obtain organs for transplant is an effective way to overcome the shortage of organ donors. The purpose of this study is to investigate ultrasound flow imaging and elastography as a simple, feasible, accurate and effective method for evaluation of liver damage after brain death using an animal model.

We established a brain-death model using 15 pigs. Brain death was induced by progressively increasing the intracranial pressure, and the brain-death state was maintained for 9 hours. Spectral Doppler imaging and elastography was used to evaluate hepatic hemodynamic parameters and tissue stiffness over the period of brain death.

Electron microscopy of the liver over the progress of brain death revealed gradual mitochondrial swelling (with rupture), expansion of the endoplasmic reticulum, and increased collagen in the extracellular matrix. Spectral Doppler imagin demonstrated that the HA-RI increased over time, which had statistically significant difference between the Bef-BD measurement and measurements at 3, 6, and 9 hours after brain death. Real time elastography of the liver revealed a gradual decrease of the mean relative strain value (MEAN) over the time, and a gradual increase in standard deviation of the relative strain value, complexity of low strain area, and skewness, suggesting that brain-death induced liver damage increases with time. The ROC curves showed that MEAN had the highest sensitivity, specificity, and accuracy for assessing liver injury.

Hepatic tissue damage induced by brain death increased over time. The HA-RI and liver stiffness index changes can be assessed by Doppler ultrasound and elastographic imaging. Our results showed that elastography is a useful method to evaluate liver damage after brain death.