1.5 Harmonic Imaging Sonography with microbubble contrast agent improves characterization of hepatocellular carcinoma.

Abstract

To investigate the usefulness of 1.5 Harmonic Imaging Sonography with the use of the contrast agent Levovist for the diagnosis of hepatocellular carcinoma (HCC) and for the evaluation of therapeutic response.
Phantom experiments were performed to compare the contrast effects of 2(nd) harmonic imaging and 1.5 Harmonic Imaging Sonography. 1.5 Harmonic Imaging Sonography was employed to examine 36 patients with HCC (42 nodules) before and after the treatment and to compare against the findings obtained using other diagnostic imaging modalities.
In 1.5 Harmonic Imaging Sonography, the tumor vessels of HCCs were clearly identified during the early phase, and late-phase images clearly demonstrated the differences in contrast enhancement between the tumor and surrounding hepatic parenchyma. Blood flow within the tumor was detected in 36 nodules (85.7%) during the early phase and in all 42 nodules (100%) during the late phase using 1.5 Harmonic Imaging Sonography, in 38 nodules (90.5%) using contrast-enhanced CT, in 34 nodules (81.0%) using digital subtraction angiography (DSA), and in 42 nodules (100%) using US CO(2) angiography. Following transcatheter arterial embolization, 1.5 Harmonic Imaging Sonography detected blood flow and contrast enhancement within the tumors that were judged to contain viable tissue in 20 of 42 nodules (47.6%). However, 6 of these 10 cases were not judged in contrast-enhanced CT. 1.5 Harmonic Imaging Sonography was compared with the US CO(2) angiography findings as the gold standard, and the sensitivity and specificity of these images for discerning viable and nonviable HCC after transcatheter arterial embolization were 100% and 100%, respectively.
1.5 Harmonic Imaging Sonography permits the vascular structures of HCCs to be identified and blood flow within the tumor to be clearly demonstrated. Furthermore, 1.5 Harmonic Imaging Sonography is potentially useful for evaluating the therapeutic effects of transcatheter arterial embolization on HCC.

Full text

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• LIVER CANCER •
1.5 Harmonic Imaging Sonography with microbubble contrast
agent improves characterization of hepatocellular carcinoma
Kouji Yamamoto, Katsuya Shiraki, Shigeo Nakanishi, Hiroyuki Fuke, Takeshi Nakano, Akira Hashimoto, Atsuya Shimizu,
Toshinobu Hamataki
ELSEVIER
PO Box 2345, Beijing 100023, China World J Gastroenterol 2005;11(36):5607-5613
www.wjgnet.com

World Journal of Gastroenterology ISSN 1007-9327
wjg@wjgnet.com © 2005 The WJG Press and Elsevier Inc. All rights reserved.
Kouji Yamamoto, Katsuya Shiraki, Shigeo Nakanishi, Hiroyuki
Fuke, Takeshi Nakano, First Department of Internal Medicine,
Mie University School of Medicine, Tsu, Mie 514-8507, Japan
Akira Hashimoto, Atsuya Shimizu, Department of Internal
Medicine, Saiseikai Matsusaka General Hospital, Matsusaka, Mie
515-8557, Japan
Toshinobu Hamataki, Sales Engineering Department, Toshiba
Medical Systems Corporation, Nagoya, Aichi 450-0003, Japan
Correspondence to: Katsuya Shiraki, MD, PhD, First Department
of Internal Medicine, Mie University School of Medicine, 2-174
Edobashi, Tsu, Mie 514-8507, Japan. katsuyas@clin.medic.mie-u.ac.jp
Telephone: +81-59-231-5015 Fax: +81-59-231-5201
Received: 2005-01-07 Accepted: 2005-02-18
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AIM: To investigate the usefulness of 1.5 Harmonic
Imaging Sonography with the use of the contrast agent
Levovist for the diagnosis of hepatocellular carcinoma
(HCC) and for the evaluation of therapeutic response.
METHODS: Phantom experiments were performed to
compare the contrast effects of 2nd harmonic imaging and
1.5 Harmonic Imaging Sonography. 1.5 Harmonic Imaging
Sonography was employed to examine 36 patients with
HCC (42 nodules) before and after the treatment and to
compare against the findings obtained using other
diagnostic imaging modalities.
RESULTS: In 1.5 Harmonic Imaging Sonography, the
tumor vessels of HCCs were clearly identified during the
early phase, and late-phase images clearly demonstrated
the differences in contrast enhancement between the
tumor and surrounding hepatic parenchyma. Blood flow
within the tumor was detected in 36 nodules (85.7%)
during the early phase and in all 42 nodules (100%) during
the late phase using 1.5 Harmonic Imaging Sonography,
in 38 nodules (90.5%) using contrast-enhanced CT, in 34
nodules (81.0%) using digital subtraction angiography
(DSA), and in 42 nodules (100%) using US CO2 angiography.
Following transcatheter arterial embolization, 1.5
Harmonic Imaging Sonography detected blood flow and
contrast enhancement within the tumors that were judged
to contain viable tissue in 20 of 42 nodules (47.6%).
However, 6 of these 20 cases were not judged in contrast-
enhanced CT. 1.5 Harmonic Imaging Sonography was
compared with the US CO2 angiography findings as the
gold standard, and the sensitivity and specificity of these
images for discerning viable and nonviable HCC after
transcatheter arterial embolization were 100% and 100%,
respectively.
CONCLUSION: 1.5 Harmonic Imaging Sonography
permits the vascular structures of HCCs to be identified
and blood flow within the tumor to be clearly demonstrated.
Furthermore, 1.5 Harmonic Imaging Sonography is
potentially useful for evaluating the therapeutic effects of
transcatheter arterial embolization on HCC.
© 2005 The WJG Press and Elsevier Inc. All rights reserved.
Key words: 1.5 Harmonic imaging sonography; Hepatocellular
carcinoma; Microbubble
Yamamoto K, Shiraki K, Nakanishi S, Fuke H, Nakano T,
Hashimoto A, Shimizu A, Hamataki T. 1.5 Harmonic Imaging
Sonography with microbubble contrast agent improves
characterization of hepatocellular carcinoma. World J
Gastroenterol 2005; 11(36): 5607-5613
http://www.wjgnet.com/1007-9327/11/5607.asp
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The usefulness of the peripheral ultrasound contrast agent
Levovist was originally thought to be limited to signal
enhancement in color/power Doppler ultrasonography[1,2].
Levovist is now employed for the diagnosis of hepatic
tumors, in which it has been found to enhance blood flow
signals and thus improve the visualization of hepatic tumor
vessels[3-5]. However, recent advances in ultrasonographic
technologies have led to the development of new imaging
techniques collectively referred to as “harmonic imaging”,
in which images are obtained using the 2nd harmonic
components of the ultrasound signal. Among these new
techniques, flash echo imaging (FEI) employs intermittent
transmission at high acoustic power to permit the
microbubbles to enter the scanning plane and thus to obtain
echoes with high sensitivity. In other words, FEI makes it
possible to acquire detailed images with high spatial
resolution in which only blood flow information is
extracted, making it easier to visualize tumor vessels. In
contrast ultrasonographic examination of hepatocellular
carcinoma (HCC), the microbubbles in Levovist cause higher
frequency signals to be generated by the tumor than by
normal hepatic parenchyma. Consequently, the contrast
resolution of the tumor and normal parenchyma is further
improved and minute blood vessels within the tumor can
be visualized[6-11]. One technique is digital subtraction imaging,

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5608 ISSN 1007-9327 CN 14-1219/ R World J Gastroenterol September 28, 2005 Volume 11 Number 36
which permits the contrast effect to be clearly identified
and is therefore employed for the diagnosis of hepatic
tumors[12-15]. In 2nd harmonic imaging, however, the presence
of tissue harmonic components may lead to poorer contrast
enhancement in some cases. In another method, Doppler
technology is used to eliminate tissue echoes and to visualize
the nonlinear behavior of the microbubbles[16-18], but this
method is susceptible to motion artifacts near the heart.
A new technology known as 1.5 Harmonic Imaging
Sonography has been developed to overcome these
problems. In this method, images are obtained using a band
that is intermediate between the fundamental and the
2nd harmonic components (Figure 1). In the 1.5 Harmonic
Imaging technique, a frequency band whose center frequency
is higher than the fundamental by a factor of 3/2 is extracted
and visualized. This frequency band is intermediate between
the fundamental and the second harmonic. It includes only
bubble echoes and is free of tissue echoes. This imaging
technique reduces tissue echoes without generating motion
artifacts such as those that are seen in the pseudo-Doppler
imaging technique. Contrast between tissues and bubbles is
improved by 20 dB or more compared with the 2nd harmonic
imaging technique. 1.5 Harmonic Imaging Sonography
involves the use of a transmission waveform in which the
bandwidth is limited and the leakage of fundamental
components is therefore reduced. The fundamental
components of tissue echoes are effectively separated from
the 2nd harmonic components, permitting images to be
obtained in an intermediate band that is almost completely
free from tissue echoes. When images are obtained in this
intermediate band, higher contrast can be achieved between
contrast agent and tissue echoes than in conventional 2nd
harmonic imaging. The echo from the tissue has only
fundamental and 2nd harmonic component. In the
intermediate band, there exists no tissue echo with the
dedicated transmission where the fundamental band width
and leakage are well controlled. On the other hand, bubble
echo has broadband harmonics in high mechanical index
(MI) contrast imaging. So high bubble/tissue signal ratio is
achieved in image with the component of that intermediate
band. Nevertheless, to our knowledge, there have been no
studies on the clinical application of 1.5 Harmonic Imaging
Sonography for the evaluation of hepatic tumors and
the assessment of therapeutic effects. The present study
was therefore conducted to investigate the clinical
usefulness of the ultrasound contrast agent Levovist for
the examination of HCCs and for the assessment of
therapeutic effects.
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Patients
This study was performed with approval from the
institutional review board, and informed consent was
obtained from each patient before undergoing this procedure.
From September 2002 and November 2003, we enrolled
in this study 36 patients with unresectable HCC, who had a
total of 42 hypervascular HCC nodules. The subjects in
the present study were 36 patients with 42 nodules that
were diagnosed as HCC based on histopathological
examination (n = 18) and diagnostic imaging findings (n = 24).
The study group comprised 36 patients with type C cirrhosis:
24 men and 12 women ranging in age from 41 to 78 years
and with a mean age of 62 years. The minimum tumor
diameter was 10 mm, the maximum tumor diameter was
73 mm, and the mean tumor diameter was 25.8±15.1 mm
(±SD). All those HCC nodules have been diagnosed by the
sonography. Before therapy, serum α-fetoprotein levels
(normal, <7 ng/mL) ranged from 4.7 to 928.6 ng/mL
(mean, 186.1 ng/mL). 12/36(33.3%) case showed normal
α-fetoprotein level.
Methods
Contrast-enhanced sonography examination
Ultrasound images were acquired using a diagnostic
ultrasound system (SSA-770A, Aplio, Toshiba) with phased-
array transducers operating at frequencies of approximately
2.5 and 3.0 MHz (PST-25AT and PST-30AT sector
transducers, Toshiba). The MI was set to 1.6, and the
transmission/reception frequencies were 1.4 MHz/3.0
MHz for 2nd harmonic imaging and 2.3 MHz/3.3 MHz in
phantom experiments and 1.7 MHz/2.5 MHz in clinical
study for 1.5 Harmonic Imaging Sonography. Contrast
images were acquired using FEI.
Phantom experiments were conducted to compare
images obtained by 2nd harmonic imaging and 1.5 Harmonic
Imaging Sonography (i.e., to compare tissue and microbubble
echo contrast between 2nd harmonic imaging and 1.5
Harmonic Imaging Sonography). The phantom consisted
of agar mixed with powdered graphite to simulate
attenuation in the living body (Nihonkai Medical; 0.6,
0.9 dB/cm/MHz). The tube in this phantom was filled
with the ultrasound contrast agent Levovist, which contains
particles composed of a mixture of galactose and palmitic
acid (SHU 508A, Levovist, Schering, Berlin, Germany;
concentration 300 mg/mL). Images of this phantom were
acquired using FEI.
In the clinical study, a total of 7 mL of Levovist at a
concentration of 300 mg/mL was injected as a single bolus
via a peripheral vein at a rate of 1 mL/s. Images were
acquired using FEI at intervals of 0.2 s. The early phase
was specified as the period of up to 60 s after the injection
of contrast agent, and the tumor vessels were observed
with the focal point set at the bottom of the tumor. Then,
after an interval of 4 min, the late phase was specified as
the period beginning at the 5-min time point, and ultrasound
transmission was performed once manually to observe
vascular enhancement (staining) of the tumor tissues. Images
Figure 1 Basic concept of 1.5 Harm onic Im aging Sonography. A high m icrobubble/
tissue ratio is obtained in the intermediate domain.
Bubble echo
broad band
1.5 Harmonic
Tissue echo
localized
1st 2nd 3rd frequency
Echo
intensity

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Yamamoto K et al. 1.5HI in HCC 5609
were recorded on S-VHS videotape immediately after the
injection of contrast agent. The patient was instructed to
hold his or her breath for 10-50 s after the injection of
Levovist in order to maintain a constant respiratory phase,
and early-phase images were obtained continuously.
Subsequently, the system was temporarily set to freeze mode
and the images stored in cine loop memory were recorded
onto the system hard disk. Five minutes after the injection,
late-phase images were observed for several seconds during
breath-holding and recorded onto the system hard disk.
Contrast-enhanced CT Contrast-enhanced CT was
performed in all patients before treatment. Contiguous
5-mm-thick axial CT scans were obtained with a HiSpeed
Advantage RP scanner (Lemage Supreme, General Electric
Yokogawa Medical Systems, Tokyo, Japan). A nonionic
contrast material, 100 mL of iopamidol (Iopamiron, Nippon
Schering, Osaka, Japan), was administered at a rate of
3 mL/s, and CT scans of the entire liver were obtained
twice: first at 20-40 s (arterial phase) after IV injection of
contrast material and then at 90 s (portal phase). Lesions
were considered to be hypervascular if they appeared denser
than the surrounding liver during the arterial phase.
Digital subtraction angiography Digital subtraction
angiography (DSA) images were obtained using a DSA
system (Infinix NB, Toshiba). The contrast agent was
injected via a catheter placed in the hepatic artery. The
presence or absence of tumor vessels was assessed. When
tumor vessels were identified, the tumor was considered to
be hypervascular. We performed transcatheter arterial
chemoembolization in all patients by selectively introducing
a coaxial microcatheter into a segmental branch or a
subsegmental branch of the hepatic artery and injecting a
mixture of iodized oil (Lipiodol, Guerbet, Aulnay-sous-Bois,
France; 3.0-10.0 mL/body) or epirubicin hydrochloride
(Farmorubicin, Pharmacia and Upjohn, Tokyo, Japan:
30-60 mg per body weight). We then preformed
embolization using 0.5 mm×0.5 mm×0.5 mm gelatin sponge
(Spongel, Yamamouchi Pharmaceuticals) in all patients.
These embolic materials were injected until the feeding
arteries were completely obliterated. If the blood supply
was from two different subsegmental arteries, both were
embolized. The effectiveness of transcatheter arterial
chemoembolization was evaluated by 1.5 Harmonic Imaging
Sonography and contrast-enhanced CT at 7 d after treatment.
US CO2 angiography In ultrasound angiography, after
the tumor was identified in a cross-sectional ultrasound
image, CO2 microbubbles were injected at a constant rate
during breath-holding via a catheter placed in the hepatic
artery. The CO2 microbubbles were prepared by adding
5 mL of autologous blood to 10 mL of CO2, connecting
the container to a three-way stopcock, and transferring the
mixture repeatedly approximately 30 times with a pump.
Ultrasound images were acquired using a diagnostic
ultrasound system (SSA-250A, Toshiba) with a 3.75-MHz
convex transducer. Images were simultaneously recorded
on videotape and magneto-optical disk from the time
immediately before the injection of CO2 microbubbles until
the time when tumor enhancement was observed. When
the tumor showed stronger enhancement than the
surrounding hepatic parenchyma, it was considered to be
hypervascular.
CT during arterial portography CT during arterial
portography (CTAP) was performed using a CT scanner
(Asteion, Toshiba, Tokyo Japan). For CTAP, 100 mL of
Iopamidol contrast medium (Iopamiron 150; Nihon
Schering, Osaka, Japan) was administered via a catheter
in the superior mesenteric artery at an estimated rate of
2.0 mL/s during sequential helical scanning of the liver.
For CT arteriography, 30-50 mL of contract medium
(Iopamiron 150) was administered via a catheter in the
proper hepatic, left, or right hepatic artery at an estimated
rate of 1.5-2.5 mL/s during sequential helical scanning of
the liver. Tumors that did not contain portal blood flow
were identified as low-absorption areas in the hepatic
parenchyma (portal perfusion defects).
Imaging analysis All the sonographic data were recorded
on videotape from the beginning of B-mode scanning. The
still images were stored on the hard disk of the unit by
reviewing the cine loop memory. The images obtained using
the above modalities were interpreted by three specialists in
diagnostic imaging. When a discrepancy occurred among
the interpreters, re-evaluation and discussion were done
for agreement. On contrast-enhanced imaging with 1.5
Harmonic Imaging Sonography, the presence of the
intratumoral blood flow signals on either the vessel image
or on the tumor parenchymal stain image was considered
as hypervascular or residual tumor due to inadequate
treatment. In contrast, the absence of the intratumoral blood
flow signals was evaluated as hypovascular or complete
response to the treatment. The contrast enhancement on
CT was reviewed by three radiologists without knowledge
of the 1.5 Harmonic Imaging Sonography results.
The sensitivity and specificity of 1.5 Harmonic Imaging
Sonography in detecting intratumoral blood flow signals on
the vessel tumor were determined using US CO2 angiography
as a gold standard[21,22]. The detectability of residual
tumor using contrast-enhanced 1.5 Harmonic Imaging
Sonography was compared with that of the tumors using
contrast-enhanced CT.
The data were analyzed with the χ2 test. A P value less
than 0.05 was considered significant.
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In vitro study
In the phantom experiments, the area occupied by the
contrast agent was shown as a gleaming white zone, with
the surrounding area corresponding to a tissue-equivalent
phantom composed of agar mixed with powdered graphite.
In oblique images, the echoes from the microbubbles
appeared as an oblique bright zone, and the surrounding
dark area corresponded to echoes from the agar phantom.
The images clearly demonstrated the improvement in tissue-
microbubble contrast in 1.5 Harmonic Imaging Sonography
as compared with 2nd harmonic imaging. In 1.5 Harmonic
Imaging Sonography, the contrast between tissues and
microbubbles was found to be clearly superior to that in 2nd
harmonic imaging (Figure 2).

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Clinical study
Blood vessels in all HCCs were more clearly depicted by
1.5 Harmonic Imaging Sonography than by 2nd harmonic
imaging (Figures 3A and C). Moreover, during the late phase,
1.5 Harmonic Imaging Sonography demonstrated the
surrounding hepatic parenchyma with higher contrast
enhancement than 2nd harmonic imaging, clearly depicting
the area of the tumor (Figures 3B and D).
In hypervascular HCCs, the blood vessels within the
tumor were clearly demonstrated during the early phase
(Figures 4B-D and 5A). In addition, late-phase images
revealed partial residual enhancement in all tumors, but with
less enhancement than the surrounding hepatic parenchyma
(Figures 3B and 5B).
With regard to the detection of blood flow signals within
the tumor in the 42 nodules, early-phase 1.5 Harmonic
Imaging Sonography revealed the tumor vessels in 36
nodules (85.7%). Late-phase images demonstrated
significantly lower enhancement of the tumor than the
surrounding hepatic parenchyma in all 42 nodules (100%).
Early-phase 1.5 Harmonic Imaging Sonography did not
show hypervascular enhancement in six nodules (14.3%),
and late-phase images confirmed that these six nodules were
not enhanced (P>0.05). As for the findings of other imaging
modalities, blood flow signals were detected within the tumor
in 39 nodules (92.9%) by contrast-enhanced CT, in 34
nodules (81.0%) by DSA, and in 42 nodules (100%) by US
CO2 angiography. CTAP showed a perfusion defect image
in all 42 nodules (100%, Table 1).
Contrast-enhanced CT did not show hypervascular
enhancement in three nodules (one small HCC nodule
measuring 10 mm in diameter and two nodule near the
heart), but 1.5 Harmonic Imaging Sonography was able to
Figure 3 A 74-year-old m an with C-type cirrhosis and HCC (15.4 m m in diam eter) in the right liver. Com parison of contrast im ages obtained by 1.5 Harm onic Im aging
Sonography and 2nd harmonic imaging. A: 1.5 Harmonic Imaging Sonography image obtained by real-time continuous sonography in the early phase (20 s after
injection). Abundant tumor vessels (arrows) with peripheral branching are seen; B: 1.5 Harmonic Imaging Sonography image obtained by real-time continuous
sonography in the late phase (5 min after injection). Residual enhancement of some tumor vessels is seen, but the boundary between the tumor and the hepatic
parenchyma is clearly demonstrated; C: 2nd harmonic imaging obtained by real-time continuous sonography in the early phase (20 s after injection). The abundant
and peripherally branching tum or vessels (arrows) cannot be clearly depicted; D: 2nd harm onic im aging obtained by real-tim e continuous sonography in the late phase
(5 min after injection). The boundary between the tumor and the hepatic parenchyma is somewhat obscure.
Figure 2 Comparison of contrast images obtained by 1.5 Harmonic Imaging
Sonography and 2nd harmonic imaging.
Figure 4 A 78-year-old man with C-type cirrhosis and HCC (73.3 mm in diameter) in the right liver. A: Right oblique conventional sonography image of the
liver shows a mixed-pattern nodule 73.3 mm in diameter in segment 6 that exhibits the typical characteristics of HCC; B: 1.5 Harmonic Imaging Sonography
image obtained by real-time continuous sonography in the early phase (20 s after injection) shows the tumor vessels; C and D: 1.5 Harmonic Imaging
Sonography images obtained by real-time continuous sonography in the early phase, 28 s (C) and 32 s (D) after injection, show abundant tumor vessels with
peripheral branching.
Second harmonic1.5 Harmonic
20 s 5 min20 s5 min
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demonstrate the tumor vessels even in these three nodules.
Furthermore, DSA failed to demonstrate tumor vessels in
eight nodules, while these vessels were successfully visualized
by 1.5 Harmonic Imaging Sonography. 1.5 Harmonic
Imaging Sonography were compared with the US CO2
angiography findings as the gold standard, and the sensitivity
and specificity of these images for discerning viable and
nonviable HCC after transcatheter arterial embolization were
100% and 100%, respectively.
With regard to treatment, 1.5 Harmonic Imaging
Sonography revealed residual blood flow signals within the
tumor in 20 (47.6%) of the 42 nodules that had been treated
by transcatheter arterial embolization. MRI, US CO2
angiography also revealed residual blood flow signals within
the tumor, but contrast-enhanced CT demonstrated residual
blood flow signals in only 14 nodules (33.3%). In the remaining
22 nodules (52.4%), no blood flow signal was observed
within the tumor by 1.5 Harmonic Imaging Sonography or
contrast-enhanced CT (Table 2, Figures 6 and 7).
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In the present study, phantom experiments were conducted
to investigate the usefulness of 1.5 Harmonic Imaging
Sonography. In 1.5 Harmonic Imaging Sonography, unlike
2nd harmonic imaging, images are obtained using a frequency
band that is lower than that of the 2nd harmonics, resulting
in a significant improvement of the contrast enhancement
non-uniformity that is frequently observed when a sector
transducer is used. In 1.5 Harmonic Imaging Sonography,
Figure 5 A 62-year-old man with C-type cirrhosis and HCC (18.9 mm in
diam eter) in segm ent 4 of the liver. A: 1.5 Harm onic Im aging Sonography im age
obtained by real-time continuous sonography in the early phase (28 s after
injection) shows abundant tumor vessels with peripheral branching; B: 1.5
Harmonic Imaging Sonography image obtained by real-time continuous
sonography in the late phase (5 m in after injection) shows residual enhancem ent
of some tumor vessels, but the boundary between the tumor and the hepatic
parenchyma is clearly depicted.
Figure 7 A 59-year-old woman with C-type cirrhosis and HCC (17.7 mm in diameter) in the right liver who had undergone transcatheter arterial chemoembolization
therapy with iodized oil and an anticancer drug. A: Transverse CT scan with iodized oil obtained 7 d after treatment shows incomplete retention of iodized oil within
the nodule; B and C: 1.5 Harmonic Imaging Sonography images obtained 34 s (B) and 5 min (C) after injection show partial enhancement. Right oblique 1.5
Harmonic Imaging Sonography image depicts residual tumor vessels within the tumor and subcapsular area (arrows), which is suggestive of possible recurrence
in this region.
Figure 6 A 73-year-old man with C-type cirrhosis and HCC (16.5 mm in diameter) in the right liver who had undergone transcatheter arterial chemoembolization
therapy with iodized oil and an anticancer drug. A: Transverse CT image with iodized oil obtained 7 d after treatment shows incomplete retention of iodized oil
within the nodule; B and C: 1.5 Harmonic Imaging Sonography images obtained 35 s (B) and 5 min (C) after injection show partial enhancement. Right oblique
1.5 Harmonic Imaging Sonography image depicts residual tumor vessels within the tumor and subcapsular area (arrows), which is suggestive of possible future
recurrence in this region.
TT
TT
ACB
ACB
TT
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