Open Journal of Me di cal Imaging, 2011, 1, 9-13
doi:10.4236/ojmi.2011.11002 Published Online September 2011 (http://www.SciRP.org/journal/ojmi)
Usefulness of Radiofrequency Ablation with the
PVT-350BTP Probe for the treatment of Hepatocellular
Carcinoma
Naoki Hotta*, Kazuo Masuko
Department of Inte rnal Medicine , Division of Hepatology, Masuko Memorial Hospital, Nagoya, Japan
Received Sept ember 5, 2011; revised September 13, 2011; accepted Sep tember 14, 2011
Abstract
Radiofrequency ablation (RFA) has been clinically employed in Japan, and its usefulness in the treatment of
hepatocellular carcinoma (HCC) has been reported by many researchers. In the present study, the convex
puncture probe PVT-350BTP, rather than a conventional convex probe, was used for RFA for the treatment
of HCC and its usefulness was assessed. At the same time, evaluation of the therapeutic effect using ultra-
sound contrast agent was investigated. The subjects were 20 patients (16 men and 4 women) with 20 HCC
nodules as confirmed by contrast CT or abdominal angiography. No nodules were ≤1.0 cm in diameter, 12
were 1.1 cm - 2.0 cm, and 8 were 2.1 cm - 3.0 cm. An Aplio diagnostic ultrasound system (Toshiba Medical
Systems, Tokyo, Japan) and the PVT-350BTP probe (Toshiba) were employed for RFA. The PVT-350BTP
supports puncture angles of 55, 70, 85, and 100 degrees. By mounting various types of puncture adapters on
the probe, 13 G to 22 G puncture needles can be used. The needle can easily be attached and detached by
operating a lever. Contrast echo studies with Levovist were performed before and after RFA, and the results
were evaluated using the Advanced Dynamic Flow (ADF) imaging technique. Puncture was performed suc-
cessfully using this probe for 20 cases with 20 nodules. It was confirmed that RFA with the PVT-350BTP
permits percutaneous treatment to be performed more reliably than with a conventional probe.
Keywords: Ultrasound, RFA, HCC，PVT-350BTP
1. Introduction
Radiofrequency ablation (RFA)[1-3] has been clinically
employed in Japan, and its usefulness in the treatment of
hepatocellular carcinoma (HCC) has been reported by
many researchers. RFA can be performed in various
ways: percutaneously, laparoscopically, via a small inci-
sion, or intraoperatively. In our department, we generally
perform echo-guided percutaneous RFA, and we are also
attempting RFA with 3D echo imaging.[4] In the present
study, we employed a convex puncture probe, the PVT-
350BTP, rather than a conventional convex probe, for
RFA for the treatment of HCC and assessed its useful-
ness. At the same time, evaluation of the therapeutic ef-
fect using ultrasound contrast agent was investigated.
2. Subjects and Methods
The subjects were 20 patients (16 men and 4 women)
with 20 HCC nodules as confirmed by contrast CT or
abdominal angiography. Their age range was 37 years to
83 years, with an average age of 65.9 years. All patients
were positive for HCV antibody. sixteen patients were
Child-Pugh class A and 4 were class B. No nodules were
1.0 cm in diameter, 12 were 1.1 cm - 2.0 cm, and 8
were 2.1 cm - 3.0 cm. Prior to the study, informed con-
sent to participate in the study was obtained from each
patient.
2.1. System and Probe Used
An Aplio diagnostic ultrasound system (Toshiba Medical
Systems, Tokyo, Japan) and the PVT-350BTP probe
(Toshiba) were employed. This probe supports four
puncture angles: 55 degrees, 70 degrees, 85 degrees, and
100 degrees. By mounting various types of puncture
adapters on the probe, 13 G to 22 G puncture needles can
be used. The needle can easily be attached and detached

N. HOTTA ET AL.
10
by operating a lever. With this probe, the tip of the nee-
dle or electrode is always located on the central axis of
the probe, and the needle or electrode can therefore be
observed even after it has been inserted into the patient's
body (Figure 1).
2.2. Ultrasound Contrast Agent and Imaging
Technique
LevovistTM (Nihon Schering Company, Osaka, Japan)
was used, with the bolus injection of 7 mL of Levovist at
a concentration of 300 mg/mL via a peripheral vein at a
rate of 1 mL/s. Advanced Dynamic Flow (ADF) was
employed as the contrast mode [5]. The injection of con-
trast agent was followed by a 10-mL physiological saline
flush. The imaging phases were specified as follows: the
early arterial phase (10 to 40 seconds after the injection
of contrast agent), the late vascular phase (41 seconds to
90 seconds after injection), and the post-vascular phase
(5 minutes after injection). Observation with continuous
transmission was performed up to 40 seconds after injec-
tion, followed by intermittent transmission (with an im-
aging interval of 1.0 second) for the next 50 seconds. In
the post-vascular phase, observation was performed us-
ing intermittent transmission (with an imaging interval of
1.5 seconds). The focus was set at the inferior margin of
the tumor.
Figure 1. The PVT-350BTP supports four puncture angles:
55 degrees, 70 degrees, 85 degrees, and 100 degrees. It has
only one needle slot, but 13 G to 22 G needles can be used
by adjusting the screw.
2.3. Evaluation of Therapeutic Effect
The therapeutic effect was evaluated using an Aquilion
helical CT scanner (Toshiba) with the slice thickness set
to 7 mm. The contrast agent Iopamiron (Nihon Schering)
was injected at a concentration of 70 mg/mL. The injec-
tion volume was 100 mL.
2.4. RFA Device
The Cool-tip RF system (Radionics, Burlington, MA)
and a single-type needle electrode (17 G) were used for
treatment. The electrode was inserted into the tumor and
ablation was performed while maintaining the impedance
at 90 W or less. The duration of a single ablation was 12
minutes. To evaluate the therapeutic effect, contrast echo
and dynamic CT studies were performed 3 days or 4
days after treatment.
Two representative cases are presented below.
Case 1: A 67-year-old man with chronic hepatitis C
who had been receiving treatment at a local hospital was
referred to our department in June 2006 for evaluation
due to an increase in the AFP value. Plain US (B-mode)
imaging showed a hypoechoic area measuring 1.5 cm in
diameter (Figure 2(a)). In contrast echo imaging, the
corresponding area was enhanced in the early arterial
phase in ADF mode (Figure 2(b)) and was less strongly
enhanced than the hepatic parenchyma in the post-vas-
cular phase (Figure 2(c)). RFA was performed using a
Radionics Cool-tip needle electrode at a puncture angle
of 100 degrees (Figure 2(d)). The duration of ablation
was 12 minutes. The procedure was performed success-
fully, with no side effects. Four days after treatment, the
presence of an adequate safety margin was confirmed by
CT and contrast echo examinations. It was judged that no
further RFA procedures were required, and the patient
was discharged from the hospital.
Case 2: A 78-year-old woman was referred to our de-
partment for treatment of a hepatic tumor. She had been
receiving treatment for hepatitis C at a local hospital. Her
family history and previous medical history were other-
wise unremarkable. In October 2006, an increased tumor
marker value was found in routine blood testing and a
hepatic tumor was detected by CT scanning, and the pa-
tient was referred to our department. In contrast CT
studies, a low-density area was observed in S3 in the
pre-contrast phase. The corresponding area was en-
hanced in the early arterial phase and appeared as a
low-density area in the late vascular phase. The patient
refused surgery or angiography and expressed a strong
preference for RFA. Informed consent was obtained
from the patient and her family, and RFA was performed.
Contrast echo was used to confirm the exact distance

N. HOTTA ET AL.
11
Figure 2. 67-year-old man. A hypoechoic area measuring 1.5 cm in diameter is seen in a plain US study (B-mode image ) (a).
The corresponding area is contrast enhanced in the early arterial phase in ADF mode (b), and is less strongly enhanced than
the hepatic parenchyma in the post-vasc ular phase (c). RFA was perfor med without side effects by using a puncture angle of
100 degrees (d).
Figure 3. 78-year-old woman. The tumor is enhanced in the early arterial phase in ADF mode (a). In the post-vascular phase,
blood flow in the tumor is less than that in the hepatic parenchyma (b).

N. HOTTA ET AL.
12
Figure 4. There was a risk of injuring the gallbladder in RFA at a puncture angle of 55 de grees (a). By using a puncture angle
of 100 degrees, RFA was performed without side effects (b).
between the tumor and the gallbladder. The tumor was
enhanced in the early arterial phase in ADF imaging
(Figure 3(a)). In the post-vascular phase, blood flow in
the tumor was less than in the hepatic parenchyma (Fig-
ure 3(b)). The distance from the gallbladder was judged
to be sufficient. At a puncture angle of 55 degrees (Fig-
ure 4(a)), however, there was a risk of injuring the gall-
bladder. A puncture angle of 100 degrees was therefore
selected, and the RFA procedure was performed suc-
cessfully without side effects (Figure 4(b)) [6]. In con-
trast echo and dynamic CT examinations performed after
RFA, no residual blood flow was observed within the
lesion and the presence of an adequate safety margin was
confirmed. It was judged that no further RFA procedures
were required.
3. Results
Puncture for RFA was successfully performed for 20
cases with 20 nodules using the PVT-350BTP. In 1 case
with a nodule in S8, a micro-convex probe was used in-
stead of the PVT-350BTP. The PVT-350BTP could have
been used in this case if artificial pleural effusion had
been employed [7], but we demonstrated in a previous
study that the micro-convex probe permits RFA to be
performed successfully without artificial pleural effusion
for the treatment of HCC nodules in S8, and we therefore
decided to use the micro-convex probe in this case.[8] In
the contrast echo examinations performed before the
RFA procedure in order to evaluate the therapeutic effect,
blood flowing into the tumor or contrast enhancement of
the tumor was observed in the early arterial phase in
every case. After the RFA procedure, no blood flowing
into the tumor was observed in the early arterial phase in
any of the cases. In the post-vascular phase, no supplying
vessels were observed and the lesion was seen as a per-
fusion defect. In dynamic CT as well, no residual blood
flow was observed in the early phase and the presence of
an adequate safety margin was confirmed in the late
phase in all cases. The evaluation results obtained by
contrast echo agreed with those obtained by dynamic CT,
although the number of cases was small.
4. Discussion
Remarkable advances have been made in diagnostic ul-
trasound systems in recent years, and echo-guided RFA
is employed at many institutions. The ultrasound probe
PVT-350BTP can provide images with the same scan-
ning angle as the standard convex probe supplied with
the Aplio system. As a result, scanning for treatment
planning and scanning for the actual puncture procedure
can be performed using the same probe. Although we
reported in a previous study that the micro-convex probe
is useful for the treatment of HCCs located immediately
below the diaphragm, treatment using the PVT- 350BTP
was judged to be difficult in 1 case in the present study.
For an HCC in the left lobe of the liver, however, RFA
could be performed safely with this probe by using a
puncture angle of 100 degrees. In addition, RFA could
also be performed safely for a tumor located near the
gallbladder by using a puncture angle of 100 degrees.
This puncture angle also permits RFA to be performed
safely for tumors adjacent to the intestines, for which
RFA with artificial ascites or laparoscopic RFA are con-
ventionally employed. The PVT-350BTP supports con-
trast mode, and we therefore employed contrast echo for
vascular studies. Since the approval of the ultrasound
contrast agent Levovist for clinical use at the end of
September 1999, contrast echo with Levovist has been
replacing echo-guided intra-arterial CO2 injection fol-
lowing intra-arterial catheterization.[9] There have been

13 N. HOTTA ET AL.
numerous reports on the usefulness of percutaneous con-
trast echo with Levovist in the detection and differential
diagnosis of hepatic tumors and in the evaluation of
therapeutic effects.[10-12] This is a noninvasive method
and can be applied to patients with impaired renal func-
tion or those who are allergic to the contrast agents that
are used in dynamic CT, X-ray angiography, or MRI.
One disadvantage is that this method cannot visualize
tumors located 10 cm or more from the liver surface be-
cause the acoustic pressure does not increase. In the pre-
sent study, none of the target tumors were located 10 cm
or more from the liver surface, and evaluation of the
therapeutic effect was successfully performed in all cases.
In evaluating the therapeutic effect of RFA, determining
the presence or absence of residual tumor is the main
objective. If an area showing blood flow in the pre-
treatment contrast echo study appears as an avascular
area in the post-treatment contrast echo study, the tumor
is judged to be necrotic. This method is also able to de-
tect residual small blood flow that may not be detectable
by CT. Even for the nodule that was located near the
gallbladder and for which the distance between the nod-
ule and the gallbladder could not be measured accurately
by CT or plain US, the use of ultrasound contrast agent
permitted the distance to be measured more accurately
and RFA treatment to be performed more safely. One
limitation is that the ultrasound contrast agent currently
available clinically in Japan is effective for only a short
time after injection. It is expected that this limitation will
be overcome with the development of new contrast
agents.[13]
5. Conclusions
The convex puncture probe PVT-350BTP permits per-
cutaneous RFA to be performed safely and effectively.
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