Research Article: Evaluation of rat liver with ARFI elastography: In vivo and ex vivo study

Date Published: May 23, 2019

Publisher: Public Library of Science

Author(s): Guillermo Carbonell, Juan de Dios Berná-Serna, Lidia Oltra, Carlos M. Martínez, Nuria Garcia-Carrillo, Florentina Guzmán-Aroca, Francisco Javier Salazar, José Tudela, Juan de Dios Berná-Mestre, Guy Cloutier.


The aim of this study was to compare in vivo vs ex vivo liver stiffness in rats with acoustic radiation force impulse (ARFI) elastography using the histological findings as the gold standard.

Eighteen male Wistar rats aged 16–18 months were divided into a control group (n = 6) and obese group (n = 12). Liver stiffness was measured with shear wave velocity (SWV) using the ARFI technique both in vivo and ex vivo. The degree of fibrosis, steatosis and liver inflammation was evaluated in the histological findings. Pearson’s correlation coefficient was applied to relate the SWV values to the histological parameters.

The SWV values acquired in the ex vivo study were significantly lower than those obtained in vivo (P < 0.004). A significantly higher correlation value between the degree of liver fibrosis and the ARFI elastography assessment was observed in the ex vivo study (r = 0.706, P < 0.002), than the in vivo study (r = 0.623, P < 0.05). Assessment of liver stiffness using ARFI elastography yielded a significant correlation between SWV and liver fibrosis in both the in vivo and ex vivo experiments. We consider that by minimising the influence of possible sources of artefact we could improve the accuracy of the measurements acquired with ARFI.

Partial Text

Non-alcoholic fatty liver disease (NAFLD) is one of the most common causes of chronic hepatopathy in adults, with a prevalence of up to 20–30% in developed countries [1]. This entity represents a wide spectrum of pathologies ranging from a simple steatosis (80–90% of cases) to steatohepatitis (10–20%) [2]. Moreover, in the absence of diagnosis and early treatment it can lead to a progressive liver fibrosis and subsequent liver cirrhosis [3].

The present study is a comparative analysis between liver parenchyma assessment using the ARFI technique in in vivo experiments, with the animals placed in the supine position and under heavy sedation to avoid any possible cardiac or respiratory artefacts, and in ex vivo experiments, after euthanisation of the animals and with the liver explants introduced into a container with physiological serum to minimise possible sources of artefact, such as those related to physiological factors (breathing, heartbeat), and improve the conditions in which we took the measurements.

This is the first experimental study to determine SWVs in the liver with the ARFI technique both in vivo and ex vivo. The SWVs are seen to be higher in vivo than those measured ex vivo. This suggests that various factors may alter the liver stiffness measurements. Furthermore, we detected some very high correlation values between SWV and the degree of liver fibrosis in both the in vivo and ex vivo experiments. In addition, a greater degree of correlation was identified in the ex vivo study, which confirms that by planning and optimising the determinations with ARFI to limit sources of artefact we can obtain more reliable, more accurate and more reproducible results. We consider that further studies are needed to clarify the possible role of ARFI in this issue.




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