Magnetic Resonance Elastography for the Noninvasive Staging of Liver
Fibrosis
LAURENT HUWART,* CHRISTINE SEMPOUX,‡ ERIC VICAUT,§ NAJAT SALAMEH,* LAURENCE ANNET,*
ETIENNE DANSE,* FRANK PEETERS,* LEON C. TER BEEK,
JACQUES RAHIER,‡ RALPH SINKUS,¶ YVES HORSMANS,#
and BERNARD E. VAN BEERS
**Diagnostic Radiology Unit, ‡Department of Pathology, and #Department of Gastroenterology, Université Catholique de Louvain, St-Luc University Hospital, Brussels,
Belgium; §Department of Nuclear Medicine, Hôpital Lariboisière, and ¶Ecole Supérieure de Physique et de Chimie Industrielles, Université Denis Diderot, Paris,
France; and
Philips Medical Systems, Best, The Netherlands
See Jacqueminet S et al on page 828 in CGH;
See editorial on page 299.
Background & Aims: The purpose of our study
was to prospectively compare the success rate and
diagnostic accuracy of magnetic resonance elastog-
raphy, ultrasound elastography, and aspartate ami-
notransferase to platelets ratio index (APRI) mea-
surements for the noninvasive staging of fibrosis
in patients with chronic liver disease. Methods:
We performed a prospective blind comparison of
magnetic resonance elastography, ultrasound elas-
tography, and APRI in a consecutive series of pa-
tients who underwent liver biopsy for chronic liver
disease in a university-based hospital. Histopatho-
logic staging of liver fibrosis according to the
METAVIR scoring system served as the reference.
Results: A total of 141 patients were assessed. The
technical success rate of magnetic resonance elas-
tography was higher than that of ultrasound elas-
tography (133/141 [94%] vs 118/141 [84%]; P 
.016). Magnetic and ultrasound elastography, APRI
measurements, and histopathologic analysis of
liver biopsy specimens were technically successful
in 96 patients. The areas under the receiver operat-
ing characteristic curves of magnetic resonance
elasticity (0.994 for F > 2; 0.985 for F > 3; 0.998 for
F  4) were larger (P < .05) than those of ultra-
sound elasticity, APRI, and the combination of ul-
trasound elasticity and APRI (0.837, 0.709, and
0.849 for F > 2; 0.906, 0.816, and 0.936 for F > 3;
0.930, 0.820, and 0.944 for F  4, respectively).
Conclusions: Magnetic resonance elastography
has a higher technical success rate than ultrasound
elastography and a better diagnostic accuracy than
ultrasound elastography and APRI for staging liver
fibrosis.
Liver biopsy is the current reference examination forthe assessment of liver fibrosis. However, it is a costly
procedure that carries a small risk of severe complica-
tions and is difficult to accept for patients. In addition,
its accuracy remains debated because of sampling vari-
ability caused by the small size of the hepatic samples
and the heterogeneity of liver fibrosis.1 The noninvasive
assessment of liver fibrosis has become a real challenge
given that chronic liver diseases affect hundreds of mil-
lions of patients worldwide. Multiple data now empha-
size that fibrosis is dynamic and, with effective interven-
tion, reversible.2 Successful treatment of viral hepatitis,
autoimmune liver disease, alcohol-related disease, and
other chronic liver diseases results not only in clinical
improvement but also in decreased histologic fibrosis.
Although experimental studies have revealed targets to
prevent fibrosis progression in rodents, the efficacy of
most treatments has not been proven in humans. The
development of reliable noninvasive markers of liver fi-
brosis is essential to assess the prognosis of the disease
and the response to treatment.2,3
Several noninvasive methods have been proposed to stage
liver fibrosis, including biochemical tests and imaging
methods. The biochemical tests are composite scores (as-
partate aminotransferase to platelets ratio index [APRI],
FibroTest [BioPredictive, Paris, France], and so on) or serum
markers of fibrosis such as hyaluronic acid. However, the
value of these diagnostic methods remains debated.2,3
Abbreviations used in this paper: APRI, aspartate aminotransferase
to platelets ratio index; CI, confidence interval; MR, magnetic reso-
nance; ROC, receiver operating characteristics.
© 2008 by the AGA Institute
0016-5085/08/$34.00
doi:10.1053/j.gastro.2008.03.076
Imaging and Advanced Technology continued
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Among the imaging methods, elastography has been
shown to be a reliable method to stage liver fibrosis. It is
based on the observation that fibrosis leads to increased
tissue stiffness. Most clinical studies have been per-
formed with ultrasound elastography.4–6 Recently, mag-
netic resonance (MR) elastography has emerged as an
alternative method to assess liver elasticity.7–9 To the best
of our knowledge, no study has been reported about the
comparison of MR and ultrasound elastography for the
assessment of liver fibrosis.
Therefore, the purpose of our study was to prospectively
compare the technical success rate and diagnostic accuracy
of MR elastography, ultrasound elastography, and APRI
measurements for staging hepatic fibrosis in patients who
underwent liver biopsy for chronic liver disease.
Patients and Methods
Patients
This study was a single-center, prospective, blind
comparison of MR elastography, ultrasound elastogra-
phy, and APRI in a consecutive series of patients who
underwent liver biopsy in the Department of Gastroen-
terology of St-Luc University Hospital, Université
Catholique de Louvain, for suspicion of chronic diffuse
liver disease between November 2005 and February 2007.
The study protocol was in accordance with the Declara-
tion of Helsinki and was approved by the ethics commit-
tee of our institution. Patients were enrolled after giving
written informed consent. MR elastography, ultrasound
elastography, and APRI measurements were performed
within 2 days of liver biopsy. The order of the examina-
tions was not randomized because it was considered that
this order should not have influenced the results in
patients with chronic liver diseases. For organizational
reasons (access to the MR scanner), MR elastography was
performed immediately before ultrasound elastography.
A blood test, including measurements of aspartate ami-
notransferase levels and platelet counts, was systemati-
cally performed the day before the liver biopsy.
To assess the reproducibility of MR and ultrasound
elastography, these examinations were repeated within 1
month in all patients in whom MR elastography, ultra-
sound elastography, APRI measurements, and analysis of
liver biopsy specimens were technically successful and
who agreed to have repeated examinations.
MR Elastography
The 3-dimensional MR elastography method has
been described in detail previously.7,10,11 Briefly, low-fre-
quency longitudinal mechanical waves of 65 Hz were
transmitted into the right liver by a transducer placed
against the last ribs at the back of the patient in supine
position. The reconstruction of the local shear elasticity
requires the presence of shear waves inside the organ.
Shear waves were obtained by utilizing the fact that
longitudinal waves generate shear waves due to mode
conversion at interfaces everywhere inside the liver. The
reason to excite in the first place with longitudinal waves
is that these get less attenuated by tissue, leading to an
efficient way for shear wave generation deep inside the
body. Shear waves afterward become separated from the
longitudinal contribution by applying the curl operator
on the total displacement vector field.
Images were obtained on a 1.5-T whole-body MR scan-
ner (Gyroscan Intera; Philips Medical Systems, Best, The
Netherlands) using a 4-elements torso coil. Five sagittal
slices through the right liver were acquired with a slice
thickness of 4 mm, field of view of 250 mm, matrix size
of 642, echo time of 61 milliseconds, repetition time of
431 milliseconds, and 2 signal averages. The patients
breathed freely, and respiratory gating was performed
with a navigator on the right hemidiaphragm. Four dy-
namics were obtained by changing the phase offset be-
tween the mechanical excitation and the MR sequence to
assess the amplitude and phase of the displacement after
Fourier transformation. The motion-encoding gradients
were applied successively in the 3 orthogonal directions
to capture all the components of the 3-dimensional dis-
placement vector. The total acquisition time was about
20 minutes, depending on the efficiency of the respira-
tory gating navigator.
The phase images were analyzed with the Voigt model
to obtain shear elasticity maps, that is, the real part of the
complex shear modulus is attributed to the solid com-
ponent of the material while the imaginary part accounts
for losses. The shear elasticity (kPa) of the liver was
measured as the mean value within the largest rectangu-
lar region of interest that fitted into the liver on the
elasticity map of the central slice. The first series of
measurements (ie, within 2 days of liver biopsy) was
performed by a junior radiologist with 4 years of experi-
ence in MR imaging. The second series of measurements
(within the month) was performed by a junior physicist
with 2 years of experience in MR imaging. These 2 ob-
servers were blinded to the clinical, biochemical, and
ultrasound data of the patient and to the results of
histopathologic analysis.
Ultrasound Elastography
One-dimensional transient ultrasound elastogra-
phy measurements were performed with a FibroScan
(EchoSens, Paris, France). The technique and examina-
tion procedure have been described previously.5 This
method measures the velocity of the shear wave, which is
directly related to Young’s elastic modulus (kPa). It
should be noted that, within tissues, the Young’s modu-
lus equals 3 times the shear elasticity modulus measured
with the 3-dimensional MR elastographic method.
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