Advances in Diagnostic Imaging - The Value of Contrast-Enhanced Ultrasound for Liver - L. Bolondi (Springer, Bio Med 1
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Advances in Diagnostic Imaging
The Value of Contrast-Enhanced Ultrasound for Liver
Advances
in Diagnostic
Imaging
The Value of
Contrast-Enhanced
Ultrasound for Liver
Editor
Luigi Bolondi
123
Editor
L
UIGI
B
OLONDI
Division of Internal Medicine
Department of Internal Medicine
and Gastroenterology
University of Bologna, Italy
Authors
R
ICCARDO
L
ENCIONI
C
LOTILDE
D
ELLA
P
INA
L
AUR A
C
ROCETTI
D
ANIA
C
IONI
Division of Diagnostic
and Interventional Radiology
Department of Oncology,
Transplants, and Advanced
Technologies in Medicine
University of Pisa, Italy
H
ANS
P
ETER
W
ESKOTT
Department of Internal Medicine
Klinikum Hannover, Germany
J
EAN
-M
ICHEL
C
ORREAS
1
A
HMED
K
HAIROUNE
1
A
NAIS
V
ALLET
-P
ICHARD
2
S
TANISLAS
P
OL
2
O
LIVIER
H
ÉLÉNON
1
Department of Adult Radiology
1
and Department of Hepatology
2
Necker University Hospital, Paris, France
ISBN-10 88-470-0457-8 Springer Milan Berlin Heidelberg New York
ISBN-13 978-88-470-0457-3 Springer Milan Berlin Heidelberg New York
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Introduction
It is well-known that, in the past few decades, imaging techniques,
and in particular ultrasonography, have led to great advances in
clinical hepatology. In fact, the widespread use of these techniques
resulted in the clinical discovery of hepatocellular carcinoma and
other liver tumours. Hepatocellular carcinoma was practically
unknown to the clinician before the advent of diagnostic ultra-
sound. Real-time ultrasonography remains the most frequently
used imaging procedure for the primary diagnosis of mass liver
lesions and for the survey of patients affected by chronic liver
diseases and tumours of the gastrointestinal tract.
In recent years, however, the imaging-based diagnosis of mass
liver lesions has become increasingly complicated due to the num-
ber and morphological variability of lesions that modern imag-
ing techniques are currently able to display. If the sensitivity in de-
tection has greatly increased, characterization has remained dif-
ficult and represents a critical challenge for the clinician. In this
perspective, the use of contrast agents with CT scan and MRI has
represented a significant advance, allowing not only the depic-
tion of different patterns of enhancement related to the different
vascular supply of each lesion, but also to the detection of a high-
er number of lesions that become visible in different phases of
vascular perfusion.
Hepatocellular carcinoma (HCC) most often displays a typ-
ical early arterial enhancement and a late washout of vascular
contrast agents. This pattern, when confirmed by two different
techniques, has been recognised by a panel of experts of the Eu-
ropean Association for the Study of the Liver (EASL) as a valid
VI
Introduction
criterion for the noninvasive diagnosis of HCC [1]. It is worth
noting that duplex Doppler techniques are able to display some
vascular abnormalities that characterise mass liver lesions; how-
ever, they are unable to display different phases of perfusion
and have a overall sensitivity far less than that of contrast-en-
hanced CT and MRI.
The availability of blood-pool contrast agents for ultrasound
(US) together with the development of US harmonic imaging
has opened up new perspectives both for the immediate char-
acterization of any mass lesion detected in the liver and for in-
creasing the sensitivity of ultrasonography in the detection of
liver metastases. The technique was initially based on digital
processing of nonlinear backscattered signals produced by the
breaking of first-generation microbubble contrast agents when
insonated by high acoustic pressure [mechanical index
(MI) = 0.8–1.2] US waves. Nevertheless, since these microbubbles
are destroyed by the high pressure, a certain amount of time (de-
pending on the blood perfusion velocity in the explored tissue)
must elapse to allow refilling of the microvessels by the contrast
agent. As a result, signals originating from microbubble de-
struction must be explored by an intermittent imaging modal-
ity. This method is technically complicated, affected by artefacts,
and does not allow continuous dynamic evaluation of vascular
perfusion. In addition, at high acoustic pressure, harmonic sig-
nals may be also produced by the surrounding tissue, thus lim-
iting the contrast resolution of the image.
More recently, contrast-specific software and technologies have
been developed that facilitate the analysis of harmonic signals
originating from the insonation of second-generation US con-
trast agents by using extremely low acoustic pressure
(MI = 0.04–0.1) US waves. These second-generation contrast
agents are based on the more stable perfluorocarbon-filled or
sulfur-hexafluoride-filled microbubbles and have a strong non-
linear harmonic response when insonated with low acoustic pres-
sure. A second-generation blood pool agent, BR1 (SonoVue; Brac-
co, Milan, Italy), consisting of phospholipid-stabilised shell mi-
crobubbles filled with sulfur hexafluoride gas, is licensed for use
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