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| Surgery |
Contrast-Enhanced Ultrasonography of the Liver
2
Contrast-Enhanced Ultrasonography of the Liver
Bjørn Skjoldbye, MD BSc, Senior Consultant, Department of Surgical Gastroenterology, Herlev Hospital, University of Copenhagen, Denmark
Morten Høgholm Pedersen, MD Product Manager, Surgical Ultrasound, B-K Medical
Lisbeth Gorr Product Manager, Contrast Imaging, B-K Medical
A new B-K Medical technology enables our
transducers and ultrasound scanners to
be used for contrast-enhanced ultrasound
(CEUS) for abdominal, laparoscopic and
intraoperative applications.
New technological achievements and the
use of ultrasound contrast agents (UCA)
have given diagnostic ultrasound a new
edge. Combined with the scanner’s selective
detection of signals from the microbubbles,
the use of UCA introduces several new
advantages to the clinical use of ultrasound.
This application note discusses the uses of
CEUS in general, and its use for detecting
and characterizing focal liver lesions in
particular.
Background
Conventional B-mode ultrasound (US) is the
most commonly used imaging modality. The
sectional US images present slices of morphology
in real time without radiation hazards and with
an excellent cost-benefit ratio. Furthermore,
purpose-designed transducers have expanded the
usefulness of clinical ultrasound.
Doppler US adds important information about
vascular flow to B-mode US. However, Doppler US
is not useful for observing or quantizing blood
flow in small vessels and capillaries. It cannot
detect flow in the microvasculature because the
flow velocity there is as low as 1 mm/sec, which
is lower than the threshold of the tissue motion
filters applied in Doppler mode; the weak signals
from low velocity flow are therefore rejected.
Using a microbubble-based ultrasound contrast
agent (UCA) in combination with a dedicated
bubble-specific technology in the US scanner
makes it possible to measure flow in small
vessels and detect perfusion in capillary beds
– and extends the clinical utility of ultrasound
considerably.
Contrast-enhanced US (CEUS) has become a valuable clinical tool
Contrast-enhanced US (CEUS) has become a
valuable clinical tool to detect increased – as
well as decreased – vascularity in focal lesions as
well as in parenchymal tissue. CEUS possesses
the same virtues as conventional ultrasound,
providing a dynamic, non-invasive real-time
imaging modality for use in numerous clinical
applications.
The vascularity of tumor tissue differs from that of
normal parenchyma. Furthermore, the vascularity
of malignant lesions differs from that of benign
ones. CEUS detects these differences and may
be used to improve the sensitivity and accuracy
of detection and classification of tumors in the
parenchymal organs. Decreased vascularity in
ischemic or infarcted tissue may be visualized,
too.
The use of a UCA improves the detection of
malignant lesions in the liver by permitting the
evaluation of the contrast dynamics after infusion
of the UCA. This method is basically similar to
the procedures for performing contrast-enhanced
CT and MRI, but the CEUS analysis is done in real
time and without radiation hazards. CEUS-guided
interventions may be performed, too.
3
CEUS Technology
Optimal CEUS requires a UCA and an ultrasound
system with UCA-dedicated technology, such
as the B-K Medical Pro Focus. The UCA is
administered into a larger peripheral vein using
simple intravenous access. The incident US from
the transducer interacts with the microbubbles
in the bloodstream. These generate UCA-specific
signals that can be separated from other signals,
as well as from noise, by dedicated technology in
the scanner.
Ultrasound Contrast Agents
Current ultrasound contrast agents consist of
gaseous microbubbles, surrounded by a shell,
suspended in solution. Gaseous microbubbles not
only act as strong reflectors in the bloodstream.
When they are exposed to the mechanical energy
of a US pulse, they produce, in addition to a
conventional echo, a specific response related to
their physical properties such as elasticity and
resonance frequency. Thus the bubbles contribute
a nonlinear component to the echoes that are
reflected back to the transducer. This nonlinear
response consists of harmonic signals that are
multiples of the fundamental frequency.
The microbubbles’ nonlinear response depends on
the energy of the ultrasound pulse.
A thin flexible shell preserves the microbubbles’
ability to generate harmonics. The signal
generated by the microbubbles will be strongest
when the microbubbles’ resonance frequency
coincides with the frequency of the incident US-
pulse.
Low and High MI
The acoustic pressure of the US pulse is expressed
as the mechanical index (MI). The MI is related to
the transmit power that provides the initial energy
to the ultrasound pulse.
A US pulse with low acoustic pressure (low MI)
does not rupture the microbubbles but causes
them to oscillate with a fundamental frequency
and a set of harmonics, as mentioned above.
Increasing the acoustic pressure above a certain
threshold (high MI) causes the microbubbles
to burst. When the bubbles rupture, free gas is
released. This strongly scatters the incident US.
However, free gas in the blood pool dissolves
quickly, so the increased signal from scattering is
transient.
Optimal CEUS requires an ultrasound system with UCA-dedicated technology, such as
the B-K Medical Pro Focus
UCA may occasionally be used to enhance
conventional Doppler US. Doppler US requires an
intermediate- or high-MI transmit power. However,
the present UCA-specific technology in the US
scanners uses low MI for CEUS. High MI may
be used transiently to destroy bubbles during
continuous CEUS (see below). The purpose of this
is to clear a volume of microbubbles so that a new
wash-in of microbubbles can be observed in the
volume. The dynamic behavior of UCA cannot be
observed with high-MI CEUS.
Early, Intermediate and Late Phases
After the infusion of a UCA bolus in a peripheral
vein, a timer is activated so that the time after
injection is displayed on the screen of the US
scanner. After 10-25 seconds (arterial phase), the
UCA is detected in the parenchymal arteries but
not in the central veins. During the portal phase,
30-45 seconds after administration of the UCA
bolus, the UCA is detected in the portal vein.
Finally, the late phase starts when the UCA is
detected in the central veins and parenchyma is
enhanced.
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Contrast-Enhanced Ultrasonography of the Liver
Continuous or Transient CEUS Imaging
Continuous low-MI CEUS is the predominant
method for using UCA to evaluate focal lesions
in the liver or other parenchymal organs. It
requires a UCA designed for low-MI CEUS – such
as DEFINITY, Sonazoid or SonoVue, which produce
resonant frequencies suitable for abdominal
imaging while the MI is low enough to produce
minimal disruption of the microbubbles. Several
new UCA are on the way to the market, including
dedicated high-frequency CEUS agents. However,
their commercial availability depends on local and
regional regulations.
A UCA that consists of low solubility gases, such
as DEFINITY, Sonazoid or SonoVue, has resonance
frequencies suitable for abdominal low-MI CEUS.
Dynamic observation of such UCA for several
minutes makes real-time investigation of the
enhancement patterns of a lesion or tissue area
possible.
Levovist, a contrast agent used mainly for
ultrasound HSG (hysterosalpingography) and
ultrasonographic reflux studies of the urinary
system in children, requires higher MI settings,
so intermittent (transient) CEUS must be used
to avoid bursting the bubbles. SAE (Stimulated
Acoustic Emission) is a transient scanning
technique which may be used with Levovist to
display metastasis of the liver. SAE does not
require a CEUS-specific technology. It utilizes the
color Doppler mode but provides only transient
information. SAE is, however, widely considered
obsolete for detection and characterization of
focal lesions.
UCA is used primarily for enhancement of
microvasculature and parenchyma. Occasionally,
UCA may be used to enhance conventional
Doppler US.
Table 1 gives details of common contrast agents,
including their interior and shell substances.
Contrast-Specific Ultrasound Techniques
Because the microbubble contrast agents generate
harmonics, harmonic imaging allows CEUS to
become a very powerful diagnostic modality.
However, harmonic signals may be generated
not only by the microbubbles but also by the
tissue itself, as it expands and contracts in
Agent Manufacturer Resonance Range
Chemical Composition MI Level
DEFINITY® BMS 1.5–4 MHz Liposome/Perfluorocarbon Low < 0.4
Levovist® Schering 2–3 MHz Lipid/Air (galactose-based) High >0.6
Sonazoid® GE Healthcare 2–8 MHz Lipid/Perfluorocarbon Low < 0.4
SonoVue® Bracco 1.8–3.2 MHz Phospholipid/Sulfur hexafloride Low < 0.4
Table 1. Specifications of common ultrasound contrast agents. To find out whether a particular UCA is approved for a particular application in a particular country, contact the UCA manufacturer.
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response to the ultrasound waves. It is essential
to differentiate between harmonic signals from
the microbubbles and harmonics generated in
the tissue. The harmonic signals from the tissue
depend on the acoustical pressure (MI) of the
ultrasound pulses. At low MI, the generation of
harmonics from the tissue is negligible.
Novel low-MI multi-pulse techniques, such as
power modulation, have been developed to detect
non-linear signals from the microbubbles.
The Power Modulation Technique
The key to modern CEUS techniques is
differentiating between the signal produced by
the contrast agent’s microbubbles and the signal
reflected from tissue. New methods for this have
dramatically enhanced the image contrast-to-
tissue ratio.
B-K Medical scanners use a power modulation
technique for separating the signals. In each scan
line, the transducer emits pulses with full and half
amplitudes. These pulses are subtracted in the
scanner, to extract the nonlinear bubble signals
from the linear tissue signals. See Table 2.
Using this tissue subtraction technique provides
the best signal-to-noise ratio to differentiate
between echoes originating from the microbubbles
and those originating from the tissue.
Dynamic Enhancement Patterns
The UCA microbubbles are blood pool agents.
Observing the dynamic behavior of the
microbubbles in a lesion or tissue volume may
demonstrate the macro- and microvascular
properties of focal pathology in the liver or other
organs.
After administration of a bolus of UCA in a
peripheral vein, the microbubbles sequentially fill
the arteries, the portal veins and the parenchyma
of the liver as well as other organs. Similar to the
responses in contrast-enhanced CT and MR, the
CEUS response in the liver is generally observed in
three phases:
arterial phase (10-25 seconds after injection) -
portal phase (30-45 seconds after injection) -
late (parenchymal) phase (>120 seconds after -
injection)
As the bubbles pass through the blood vessels,
changes in the contrast-enhanced image
allow normal tissue to be differentiated from
pathological, based on the dynamics of the
different macro- and microvasculature in the
tissue types. Over time, the microbubbles are
distributed throughout the liver, so it appears
Transmit Echo from tissue Echo from bubbles
Half amplitude
Full amplitude
(2 x half ampl.) – full ampl.
1. Contrast mode before injection.
2. Contrast mode after injection.
Table 2: Principle of the power modulation technique. Linear response from the tissue is canceled by subtraction. A nonlinear response to the more powerful pulse will be different from the sum of the response to the two weaker pulses. Therefore, subtraction will give a non-zero result if a nonlinear (microbubble) response is present.
1 2
6
Contrast-Enhanced Ultrasonography of the Liver
a strong echo from the microbubbles but low
enough not to burst them. For best results, MI
must be as high as possible without bursting the
bubbles.1
The Pro Focus scanner has special contrast
imaging setups that have the MI optimized for the
transducer and the specific contrast agent being
used. With simultaneous B-mode and CEUS, the
low MI setting applies to both views.
Clinical Considerations
Before scanning with CEUS, you should make a
B-mode recording of the volume of interest.
After this, you should optimize the US scanner for
CEUS by selecting a setup appropriate for the type
of UCA and purpose of the scanning. The setup
specifies the appropriate MI levels and generally
generally contrast enhanced. Malignant lesions,
on the other hand, especially metastases which
represent non-liver tissue, appear hypoechoic.
Safety
UCA are widely considered safe and non-toxic.
Hypersensitivity may occur, but allergic reactions
are relatively rare, compared to reactions to X-ray
or MR contrast agents. Theoretically, UCA could
produce biological side effects, and the expected
clinical benefits of UCA versus the possible side
effects should always be evaluated, taking into
account the safety information provided by the
UCA manufacturer.
Methods and Equipment
Mechanical Index Is Important
The acoustic power must be sufficient to generate
CEUS Step by Step
The European Federation of Societies for Ultrasound in
Medicine and Biology (EFSUMB) recommends the following
steps for CEUS investigations.2
Note that in order to know which vascular phase an image
corresponds to, it is important to start the scanner’s timer
when you inject the contrast agent and to document the
various phases of the enhancement.
1. Perform a baseline B-mode US examination, possibly
also color and Doppler examinations.
2. Identify target lesions, and then keep the transducer
in a stable position.
3. Make sure your equipment is set for CEUS. (With
the Pro Focus, this means using one of the special
contrast setups.)
Low MI (<0.3) -
CHI-mode activated -
Simultaneous imaging activated -
4. Administer UCA.
Intravenous bolus of UCA followed by 5-10 ml saline flush -
(needle diameter not less than 20 gauge so mechanical impact does not break bubbles)
Start the timer on the scanner when you inject the UCA -
5. Scan continuously and document (see next step) the
investigation for at least 60-90 seconds to cover the
arterial and portal phases. For assessment of the
late phase, you may scan intermittently until you
observe that the UCA has disappeared from the liver
microvasculature.
6. Document the investigation on video or by storing
movie clips in the scanner. You can adjust the
length and number of clips, and you can record
continuously.
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includes a split-screen view to display the contrast
and B-mode images at the same time.
Note: Ultrasound images in this paper show
simultaneous B-mode and CEUS. Because the
MI is low, the quality of the B-mode image is
not optimal, but it is good enough to use for
orientation purposes.
In most cases, the contrast agent is administered
through a cannula in the cubital fossa and
followed by a flush of saline. A timer on the US
scanner must be activated as the UCA is injected.
Clinical Benefits
Research conducted over the past few years has
identified several potential clinical benefits of the
use of CEUS, including the following:
detection of liver metastasis -
characterization of liver lesions -
management of ablation therapy -
Detection of Liver Metastasis
Liver metastases appear hypoechoic in the portal
and late phases.
Clinical studies have shown that CEUS dramatically
improves the detection of liver metastasis
compared to what is found with conventional
US alone. Some studies even suggest that CEUS
detects lesions as well as contrast-enhanced CT.3
In conventional ultrasound examinations,
metastases may be overlooked because they
are very small or isoechoic, or because the liver
parenchyma appears heterogeneous and the
metastasis blends in with the background of the
ultrasound image.
CEUS has been found to increase the sensitivity of
detecting liver metastases from 40% to 84%.4
However, a few liver lesions localized in the
deepest regions of the parenchyma seen on other
imaging modalities will remain out of reach of
the transducer’s ultrasound beam. In these cases,
CEUS does not provide a solution.
Characterization of Liver Lesions
One of the important advantages of CEUS is the
continuous real-time information about contrast
agent uptake in the tissue. “The high reliability
is based on the markedly different contrast-
uptake patterns of the most common liver lesions
or pseudo lesions.”5 CT and MRI provide only
snapshots of information during the time period,
but contrast imaging provides the surgeon
with more information: “In our experience, the
examination of arterial inflow is very important
for lesion characterization. Due to the short time
window of arterial inflow, continuous observation
with [UCA] is superior to the one arterial image
taken with CT or MRI.”5
Differentiation between malignant and benign
lesions
When a tumor is detected, the important
distinction a surgeon needs to make is: benign
versus malignant. The perfusion kinetics
demonstrated by normal liver parenchyma and
pathological tissue seem to be key to making this
distinction.6 “Contrast-enhanced US may now offer
a definitive diagnosis for hemangiomas and FNHs
which would defer referral to more costly and/or
invasive procedures and any delay in the patient
management.”6
When a tumor is detected, the important distinction a surgeon needs to make is: benign versus malignant
A characteristic feature of malignant lesions,
particularly liver metastases, is that the
microbubbles wash out during the portal and
late phases. Hepatocellular carcinoma (HCC) can
show some enhancement in the late phase or may
appear isoenhanced.
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Contrast-Enhanced Ultrasonography of the Liver
Being able to save film clips of the changing
ultrasound image on the scanner allows the doctor
to carefully examine the dynamic patterns by
replaying the clips.
Table 3 describes the differing contrast uptake
patterns characteristic of various lesion types
over time. The patterns described are the most
common ones. The vascular pattern that a tumor
exhibits after a contrast agent is injected will vary,
however.
Hemangiomas display a characteristic centripetal
filling pattern: the enhancement starts in the
periphery and gradually fills the lesion towards
its center. (See Case 2.) Larger cavernous
hemangiomas may be seen filling the contrast
in patchy areas situated in the periphery of the
Phase: Time after injection of contrast agent
Lesion Type Arterial phase: 10-25 sec Portal phase: 30-45 sec Late phase >120 sec
BENIGN Contrast enhancement in benign lesions tends to be hyperenhancing relative to the liver parenchyma in the late phase.
Hemangioma Peripheral nodular enhancement
Progressive centripetal enhancement
Complete enhancement
FNH (focal nodular hyperplasia)
Spoke-wheel and hyper-enhancement after few seconds
Hyper- enhancement; hypoenhanc-ing central scar in 70%
Iso- or hyper-enhancementplus hypo-enhancing central scar
MALIGNANT A characteristic feature of malignant lesions, particularly liver metastases, is that the lesions appear hypoenhanced in the late phase.
HCC (hepatocellular carcinoma
Hyperechoic rim enhance-ment with chaotic vessels
Hypo- or iso- enhancement
Hypo- enhancement
Hypovascular metastasis
Hypo- reflective lesions with typical rim enhancement
Progressive hypo- enhancement
Hypo- enhancement
Hypervascular metastasis
Brightly enhancing hyper-reflective and homogeneous
Progressive hypo- enhancement
Hypo- enhancement
Table 3. Phases of contrast enhancement of focal liver lesions after injection of contrast agents. Note that over time, the microbubbles are distributed through the liver tissue, making it appear generally contrast enhanced. (Information in table adapted from Albrecht et al 2 and Albrecht 7.
9
lesion that gradually, often over several minutes,
fuse and cover all non-necrotic areas of the lesion.
The small, often capillary-laden, hemangioma may
be subject to very rapid enhancement where the
saturation of the entire lesion with the contrast
agent takes place in just a few seconds.
Malignant lesions tend to have blood primarily
supplied by arteries. This is why they may appear
more enhanced than the background parenchyma
in the arterial phase.
CEUS is a strong tool for monitoring radio frequency ablation (RFA) procedures
Management of Ablation Therapy
Various studies have indicated that CEUS is
a strong tool for monitoring radio frequency
ablation (RFA) procedures in percutaneous,
laparoscopic, or intraoperatively-guided tumor
ablations. “Contrast-enhanced US has a high
specificity and a good agreement with dynamic CT
or MRI in detecting residual viable tumoral areas.”8
“The introduction of second-generation contrast
agents in transabdominal ultrasound has
increased the sensitivity and the specificity
for detecting focal liver lesions. Their use also
allows for improved management during ablation
procedures.”9
Repeating CEUS after ablation allows the vascular
activity in the tumor and its surroundings before
and after RFA to be compared. If CEUS indicates
residual vital tumor tissue after an ablation, the
procedure may be extended or repeated until
treatment is considered sufficient.
Case Studies
An increasing body of research points to the
potential value of CEUS in connection with various
procedures, from the least invasive (percutaneous
abdominal scanning) to the most invasive
(intraoperative).
Intraoperative ultrasound has consistently been
shown to be significantly more sensitive than
other imaging techniques for detecting liver
malignancies.10, 11
Recent studies indicate that intraoperative
CEUS (CEIOUS) improves the accuracy of normal
intraoperative ultrasound (IOUS) and suggest
that it is an essential tool for use with patients
undergoing liver resection.12, 13
The following cases illustrate the spectrum of
procedures utilizing CEUS, including abdominal,
intraoperative and laparoscopic ultrasound
scannings.
10
Contrast-Enhanced Ultrasonography of the Liver
Benign Lesions
Case 1. Angioma: Percutaneous abdominal
CEUS and CE-CT
CEUS imaging of an angioma in the late phase and
the corresponding contrast-enhanced CT (CE-CT).
Investigation of the relation between the right
portal vein and the borders of a large angioma.
8820e transducer.
Case 2. Hemangioma
Characteristic centripetal filling pattern of a
hemangioma.
Late phase hyperechoic. 8820 transducer.
Case 2. Hemangioma
Figure 2a. Arterial phase. Figure 2b. Portal phase. Figure 2c. Late phase.
Case 1. Angioma
Figure 1a. CEUS view. Figure 1b. CE-CT view. Dotted rectangle shows area of CEUS view.
11
Malignant Lesions
Case 3. Liver metastasis: Percutaneous
abdominal scanning
66-yr-old male with rectal cancer. Abdominal
ultrasound of the abdomen is performed, and
several solid lesions are detected in the liver.
CEUS is performed in simultaneous CHI-mode
after administration of a bolus of 2.4 ml
SonoVue. 8820 transducer.
The dynamic contrast enhancement pattern is
recorded, with t=0 when the bolus is infused
intravenously followed with a flush of 5 ml
isotonic saline.
The appearance of the lesion as vascularly active
in the arterial phase, gradually shifting to an echo-
poor appearance in the enhanced parenchyma in
the late phase, is classic for a metastasis in the
liver.
Case 4. Liver metastasis: Percutaneous
abdominal scanning
Detection and characterization of a liver
metastasis from colorectal cancer deep in the
liver, segment VII. 8820e transducer.
Case 4. Liver metastasis
Figure 4a. Early portal phase. Figure 4b. Portal phase Figure 4c. Late phase.
Case 3. Liver metastasis
Figure 3a. Arterial phase. The lesion and the arteries in the liver tissue are enhanced. The liver tissue is seen without enhancement.
Figure 3b. Early portal phase. Enhancement of the portal vessels. The lesion and the liver parenchyma are seen with different enhancements.
Figure 3c. Late phase. The lesion appears echo poor in the still-enhanced parenchymal background.
12
Contrast-Enhanced Ultrasonography of the Liver
RF Ablation and Management
Case 5. CEUS monitoring of percutaneous
RF ablation
CEUS before and after US-guided percutaneous
RFA of a solitary liver metastasis in a 55-yr-old
female with breast cancer. 8820 transducer.
Case 6. Gastrointestinal stromal tumor
with RFA: Intraoperative monitoring
52-yr-old female with gastrointestinal stromal
tumor (GIST). Primary tumor in the small intestine
removed radically. New metastasis was detected
in the liver and treated with percutaneous RF
ablation 9 months later. Disease stabilized on
systemic therapy with Glivec®.
However, a new solitary metastasis was detected
in the liver two years later. IOUS with CEUS (8815
transducer) detected a small new metastasis on
the edge of the previously ablated volume (Fig 6a).
The recurrence was not seen on CT but was seen
with CEUS. The previously ablated area appears
empty of contrast activity as opposed to the active
Case 5. Percutaneous RFA monitoring
Figure 5a. Preparation for US-guided percutaneous RF ablation. In B-mode, target is seen as an echo-poor lesion on the puncture line.
Figure 5b. CEUS after 2.4 ml SonoVue administered intravenously. Markedly peripheral vascular activity (arrow) before RF treatment observed in all phases. Late phase shown here.
Figure 5c. Needle tip seen in target (arrow) during placement of RF device.
Figure 5d. Tines of the RF needle are unfolded and the treatment started.
Figure 5e. Immediately after a 19 min. RF ablation, lesion seen with heterogeneous changes in and around the lesion. Border of ablation volume cannot be clearly defined.
Figure 5f. Successful RF ablation confirmed. CEUS presents a 34 x 42 mm ablation volume (t = 38) with sharp borders and without vascular contrast activity. Ablation volume encapsulates target lesion, and no residual areas with vascular/contrast activity are defined.
Case 6. Gastrointestinal stromal tumor with RFA: Intraoperative monitoring
Figure 6a. Arterial phase Figure 6b. RFA performed. Figure 6.c. Ablation successful and complete.
Figure 7. Intraoperative CEUS identifies vascular activity on the posterior portion of primary RF-ablated metastasis on the liver. Repeated RF ablation required.
Figure 8. In B-mode (right) the ablation area appears irregular. In simultaneous CEUS, the ablation volume appears with a regular border and without internal vascular activity.
Cases 7 and 8. Intraoperative RFA monitoring
13
vascular appearance of the new metastasis. IOUS-
guided RFA is performed (Fig 6b), and IOUS with
CEUS after the ablation shows a successful and
complete ablation without contrast activity.
Case 7. Recurrent liver metastasis: Intraoperative RFA monitoringCEUS performed intraoperatively identifies
vascular activity on the posterior portion and a
primary RF-ablated metastasis in the liver. 8815
transducer.
Conclusion: CEUS helped to identify subtle signs
of recurrence, enabling the surgeon to determine
an optimal and immediate course of treatment.
Case 8 CEUS after intraoperative RFA of a
liver metastasis
Follow-up CEUS 5 weeks after RFA of liver
metastasis.
Case 5. Percutaneous RFA monitoring
Figure 5a. Preparation for US-guided percutaneous RF ablation. In B-mode, target is seen as an echo-poor lesion on the puncture line.
Figure 5b. CEUS after 2.4 ml SonoVue administered intravenously. Markedly peripheral vascular activity (arrow) before RF treatment observed in all phases. Late phase shown here.
Figure 5c. Needle tip seen in target (arrow) during placement of RF device.
Figure 5d. Tines of the RF needle are unfolded and the treatment started.
Figure 5e. Immediately after a 19 min. RF ablation, lesion seen with heterogeneous changes in and around the lesion. Border of ablation volume cannot be clearly defined.
Figure 5f. Successful RF ablation confirmed. CEUS presents a 34 x 42 mm ablation volume (t = 38) with sharp borders and without vascular contrast activity. Ablation volume encapsulates target lesion, and no residual areas with vascular/contrast activity are defined.
Case 6. Gastrointestinal stromal tumor with RFA: Intraoperative monitoring
Figure 6a. Arterial phase Figure 6b. RFA performed. Figure 6.c. Ablation successful and complete.
Figure 7. Intraoperative CEUS identifies vascular activity on the posterior portion of primary RF-ablated metastasis on the liver. Repeated RF ablation required.
Figure 8. In B-mode (right) the ablation area appears irregular. In simultaneous CEUS, the ablation volume appears with a regular border and without internal vascular activity.
Cases 7 and 8. Intraoperative RFA monitoring
14
Contrast-Enhanced Ultrasonography of the Liver
Laparoscopic CEUS
Conclusion
Conclusion
CEUS is proving to be a very valuable addition to
doctors’ toolkits, helping them detect lesions and
– by letting them observe contrast-uptake patterns
over time – helping them characterize the lesions
as well. In some cases, CEUS can perhaps replace
more expensive and time consuming procedures.
B-K Medical transducers and scanners can be
used for the entire spectrum of contrast imaging:
percutaneous to laparoscopic to intraoperative.
Note: Contrast-enhanced ultrasound of the liver
has not been approved by the FDA for use in the
USA.
Case 9. Liver metastasis: Laparoscopic
scanning (LUS)
8666 transducer.
Conclusion: CE-LUS (contrast-enhanced
laparoscopic ultrasound) detects more metastases
than B-mode LUS. LUS- or CE-LUS-guided biopsy is
possible.
Figure 9a. CE-LUS after administration of 2.4 ml bolus of SonoVue. Multiple small metastases detected by CE-LUS.
Figure 9b. Biopsy from liver metastasis performed (without contrast) after CE-LUS.
Case 9. Liver metastasis
15
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References
Trademarks
DEFINITY is a registered
trademark of Bristol-Myers
Squibb Medical Imaging.
Glivec is a registered trademark
of Novartis AG.
Levovist is a registered
trademark of Schering AG.
Sonazoid is a registered
trademark of GE Healthcare.
SonoVue is a registered
trademark of Bracco S.p.A.
Figure 9a. CE-LUS after administration of 2.4 ml bolus of SonoVue. Multiple small metastases detected by CE-LUS.
Figure 9b. Biopsy from liver metastasis performed (without contrast) after CE-LUS.
Case 9. Liver metastasis
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