Early Detection of
Steatohepatitis in Fatty Rat Liver
by Using MR Elastography1
Najat Salameh, PhD
Benoıˆt Larrat, MSc
Jorge Abarca-Quinones,MSc
Ste´phane Pallu, PhD
Myle`ne Dorvillius, PhD
Isabelle Leclercq,MD, PhD
Mathias Fink, PhD
Ralph Sinkus, PhD
Bernard E. Van Beers,MD, PhD
Purpose: To assess the potential value of magnetic resonance (MR)
elastographic imaging to help detect nonalcoholic steato-
hepatitis in the fatty rat liver.
Materials and
Methods:
This study was approved by the regional ethics committee.
Fifty-four rats were imaged after being fed either a stan-
dard diet, a choline-deficient diet for up to 8 weeks to
induce steatohepatitis, or a 2-week orotic acid diet to
induce steatosis; or were imaged 48 hours after carbon
tetrachloride injection to model acute liver injury. MR
elastography was performed at 7.0 T to assess viscoelastic
liver parameters. Steatosis and fibrosis were quantified
with morphometric and biochemical analysis. Myofibro-
blast activation was assessed with morphometric analysis
of
-smooth muscle actin. Expression of transforming
growth factor 1 and procollagens 1 and 3 as markers of
fibrogenesis was evaluated with real-time reverse tran-
scription polymerase chain reaction. Inflammation was
scored at histologic analysis.
Results: In rats with steatohepatitis, mean elasticity (2.24 kPa 
0.19 [standard deviation] vs 1.82 kPa  0.22) and mean
viscosity (0.86 kPa  0.10 vs 0.59 kPa  0.12) increased
significantly (P  .005) after the 2-week orotic acid diet,
while steatosis, inflammation, myofibroblast activation,
and increase of other fibrogenesis markers were observed.
Fibrosis appeared only after 5 weeks. In rats with steato-
sis, viscosity increased (0.77 kPa  0.11, P  .005), elas-
ticity remained constant. In rats with acute liver injury,
elasticity (2.96 kPa  0.63) and viscosity (0.85 kPa 
0.22) increased (P  .005), while fibrogenesis and inflam-
mation were observed without substantial fibrosis or ste-
atosis. At multivariate analysis in all rats, liver elasticity
correlated only with myofibroblast activation (P  .001,
r  0.6).
Conclusion: The results suggest that in nonalcoholic fatty rat liver, MR
elastography may be useful in the early detection of steato-
hepatitis by showing increased elasticity and appearing
before fibrosis development, which was linked to myofi-
broblast activation.

RSNA, 2009
Supplemental material: http://radiology.rsna.org/lookup
/suppl/doi:10.1148/radiol.2523081817/-/DC1
1 From the Diagnostic Radiology Unit (N.S., J.A.Q., S.P.,
M.D., B.E.V.B.), and Laboratory of Gastroenterology (I.L.),
Universite´ Catholique de Louvain, St-Luc University Hospital,
Avenue Hippocrate 10, Brussels, Belgium; and Laboratoire
Ondes et Acoustique, Paris, France (B.L., M.F., R.S.). Re-
ceived October 13, 2008; revision requested December 2;
revision received February 7, 2009; accepted March 12;
final version accepted April 1. Supported by Fonds National
de la Recherche Scientifique (grant FRSM 3.4580.06). Ad-
dress correspondence to N.S. (e-mail: najat.salameh
@u-psud.fr ).
 RSNA, 2009
OR
IG
IN
AL
RE
SE
AR
CH

EX
PE
RI
M
EN
TA
L
ST
UD
IE
S
90 radiology.rsna.org ▪ Radiology: Volume 253: Number 1—October 2009
Note: This copy is for your personal, non-commercial use only. To order presentation-ready copies for
distribution to your colleagues or clients, use the Radiology Reprints form at the end of this article.

Nonalcoholic fatty liver disease is in-creasing in prevalence worldwide(1). It has reached epidemic pro-
portions in the United States, Europe,
and in most urban areas in the Third
World (2), and increasingly affects chil-
dren (3–5). Although no medication has
yet proved to be clearly effective against
steatohepatitis, promising new treat-
ments are currently under investigation in
large clinical trials (6,7).
The disease has two natural patterns:
Simple fatty liver, or simple steatosis, oc-
curs in about 80% of patients and follows
a benign clinical course. The second form
of the disease is nonalcoholic steatohepa-
titis, which is a potentially serious condi-
tion associated with a substantial increase
in morbidity and mortality. Nonalcoholic
steatohepatitis is characterized by the
presence of hepatic inflammation and fi-
brosis, in addition to steatosis. It may lead
to liver cirrhosis, terminal liver failure,
and hepatocellular carcinoma. Therefore,
it is important to distinguish nonalcoholic
steatohepatitis from steatosis (8). Cur-
rent biochemical tests and conventional
imaging lack accuracy for this purpose
(6). Thus, liver biopsy currently remains
the only reliable way of diagnosing and
staging nonalcoholic steatohepatitis.
MR imaging can be used to help
detect and grade liver steatosis (9–
11). However, it cannot help distin-
guish between steatohepatitis and
simple steatosis. Ultrasonographic
(US) elastography, and more recently,
magnetic resonance (MR) elastogra-
phy, have emerged as promising meth-
ods to help in the accurate diagnosis
and quantification of liver fibrosis. It
has been shown that the elasticity of
the liver increases with increasing se-
verity of fibrosis (12–22). Preliminary
studies in humans have shown that
transient US elastography may also be
a useful tool to score liver fibrosis in
nonalcoholic steatohepatitis (23,24).
However, the ability to determine an
early diagnosis of steatohepatitis be-
fore the occurrence of fibrosis without
performing a biopsy remains elusive.
It has been shown, by using ex vivo
rheometry, that liver elasticity increases
at early stages of liver injury, before the
deposition of fibrillar collagen (25). In-
crease of liver stiffness without fibrosis
has also been shown in patients with
acute viral hepatitis by using transient US
elastography (26). Inflammation and fibro-
genesis have been considered as potential
causes for this early increase of liver stiff-
ness. To our knowledge, this concept of
early increase in elasticity before the ap-
pearance of fibrosis has not been shown in
nonalcoholic fatty liver disease or validated
by using MR elastography. Therefore, the
aim of our study was to assess the potential
value of MR elastography for the noninva-
sive detection of nonalcoholic steatohepati-
tis in the fatty liver.
Materials and Methods
Animals
This study was approved by the regional
ethics committee for animal care (Ile de
France-Sud, Paris, France). The initial
study group included 55 male Sprague-
Dawley rats (mean weight, 268 g  53
[standard deviation], mean age, 9
weeks  2) that were housed individu-
ally in stainless steel wire cages and
maintained at a mean temperature of
21°C  1. The cages were placed in a
room with a 12-hour light-dark cycle. Of
these 55, 15 healthy rats had free access
to standard food and water; 12 of these
were used as controls and three were
used to assess the reproducibility of MR
elastography at 7.0 T.
Twenty-four rats were fed a choline-
deficient, L-amino acid–defined diet with-
out ethionine supplementation (Dyets
518753; Research Diets, New Brunswick,
NJ) ad libitum. Steatohepatitis obtained
by means of a choline-deficient diet is a
defined rat model of nonalcoholic steato-
hepatitis and has the strong advantage of
offering a clear delay between the occur-
rence of steatosis and of fibrosis (27,28).
To reach different stages of steatohepati-
tis, eight rats were fed this diet for 2
weeks; eight rats, for 5 weeks; and eight
rats, for 8 weeks. Eight rats were fed a
diet (A04; Scientific Animal Food & Engi-
neering, Augy, France) supplemented
with 5%orotic acid ad libitum for 2weeks
to induce simple steatosis (29). Finally,
eight rats received an intraperitoneal in-
jection of carbon tetrachloride at a dose
of 0.75mL per kilogram of body weight to
cause acute liver injury; imaging was per-
formed 48 hours after injection. One rat
in the 2-week choline-deficient diet group
died after administration of anesthetic
but before imaging. Therefore, the final
imaging group included 54 rats.
MR Elastography
Before imaging, the nonfasting rats were
anesthetized by using intraperitoneal in-
Published online before print
10.1148/radiol.2523081817
Radiology 2009; 253:90–97
Abbreviation:
SMA  smooth muscle actin
Author contributions:
Guarantors of integrity of entire study, N.S., J.A.Q., R.S.,
B.E.V.B.; study concepts/study design or data acquisition
or data analysis/interpretation, all authors; manuscript
drafting or manuscript revision for important intellectual
content, all authors; approval of final version of submitted
manuscript, all authors; literature research, N.S., B.L.,
J.A.Q., S.P., M.D., B.E.V.B.; experimental studies, N.S.,
B.L., J.A.Q., S.P., M.D., I.L., M.F., R.S.; statistical analy-
sis, N.S., R.S.; and manuscript editing, N.S., B.L., J.A.Q.,
S.P., M.D., I.L., R.S., B.E.V.B.
Authors stated no financial relationship to disclose.
Advances in Knowledge

In a model of rat steatohepatitis,
the viscoelasticity of the liver in-
creased relative to that of healthy
rats before fibrosis appeared.
 Only the hepatic viscosity in-
creased in a model of simple ste-
atosis, whereas both elasticity and
viscosity increased in a model of
acute liver injury.
 At multivariate analysis in all rats,
only myofibroblast activation was
significantly related to the elastic-
ity (P  .001, r  0.6).
Implication for Patient Care

The results in rats suggest that
early diagnosis of nonalcoholic
steatohepatitis in patients with
fatty liver is feasible by observing
increased hepatic elasticity at MR
elastography before the appear-
ance of fibrosis.
EXPERIMENTALSTUDIES: Imaging Steatohepatitis withMR Elastography in Rats Salameh et al
Radiology: Volume 253: Number 1—October 2009 ▪ radiology.rsna.org 91