DOI:10.2214/AJR.05.0750
AJR 2007; 189:W146-W149
© American Roentgen Ray Society
Multiple-Electrode Radiofrequency Ablation of Symptomatic Hepatic Cavernous Hemangioma
J. Louis Hinshaw1,
Paul J. Laeseke1,
Sharon M. Weber2 and
Fred T. Lee, Jr.1
1 Department of Radiology, University of Wisconsin, 600 Highland Ave., E3/311
CSC, Madison, WI 53792.
2 Department of Surgery, University of Wisconsin, Madison, WI.
Received May 2, 2005;
accepted after revision August 3, 2005.
Address correspondence to F. T. Lee, Jr.
WEB This is a Web exclusive article.
Keywords: cavernous hemangioma • liver • radiofrequency ablation
Introduction
Hepatic cavernous hemangioma is a common benign neoplasm of the
liver present in as many as 20% of bodies at autopsy
[1]. Hemangioma generally has a
benign course and rarely necessitates intervention of any kind. Some
hemangiomas, however, are symptomatic and can cause hepatic hemorrhage,
thrombocytopenia, and jaundice
[2]. Current medical therapy
for symptomatic hemangioma is largely ineffective, and surgical removal,
although effective, is associated with high morbidity
[3-5].
We describe the use of radiofrequency ablation in the minimally invasive
management of a large symptomatic hepatic hemangioma. When this article was
first submitted to and accepted for publication, it was the first to describe
use of a multiple-electrode radiofrequency ablation system based on a
switching algorithm in treatment of a tumor in a human
[6].
Case Report
A 48-year-old man presented with a history of multiple hepatic hemangiomas.
The dominant tumor, located in the peripheral right lobe of the liver, had
grown from 3.0 to 7.5 cm over the course of 9 years
(Fig. 1A). Over that time, the
patient had experienced worsening right upper quadrant pain exacerbated by
exertion. The patient had thoroughly investigated treatment options before
presentation and had refused surgery on several occasions. Because of the
large size of the tumor, radiofrequency ablation with standard
single-electrode techniques would have required prolonged treatment and
anesthesia time, and the decision was made to manage the tumor with a new
multiple-electrode radiofrequency switching controller (Cool-tip, Valleylab).
This system is based on switching between electrodes at each impedance spike
(a rapid increase in impedance greater than 30 ohms) or at a 30-second default
setting. Compared with a conventional single-electrode radiofrequency system,
the multiple-electrode device increases the duty cycle of the generator by
powering additional electrodes during the off time inherent in the standard
pulsing algorithm [7]. Because
tissue cooling after radiofrequency ablation is slow compared with heating,
large thermal lesions can be made when the electrodes are placed in proximity
to one other.
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Fig. 1A —48-year-old man with hepatic hemangioma. Contrast-enhanced CT scan
in portal venous phase before ablation shows characteristic peripheral nodular
enhancement within large hemangioma in right lobe of liver. Delayed images
showed areas of enhancement with centripetal filling.
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In this case, the hemangioma was managed with percutaneous CT and
sonographically guided multiple-electrode radiofrequency ablation. The patient
was given general anesthesia and placed in the left posterior oblique position
on the CT table. Because of the peripheral location of the tumor in direct
contact with the diaphragm, 1,000 mL of 5% dextrose in water was infused into
the peritoneal space. This technique is routinely used at our institution to
protect perihepatic structures in the management of peripheral liver tumors
[8,
9]. Under sonographic guidance,
three 4.0-cm exposure single electrodes (Cool-tip, Valleylab) were positioned
in a triangular array within the center of the hemangioma (Figs.
1B,
1C and
1D). A 16-minute ablation cycle
was performed with the switching controller under sonographic guidance. A zone
of decreased echogenicity (presumably due to clotting blood) was initially
found in the tumor surrounding the electrodes (Figs.
1E and
1F). Hyperechoic gas bubbles
then developed (Fig. 1G).
Temperatures greater than 50°C were obtained at each electrode, but the
hyperechoic zone did not appear to cover the entire tumor. Therefore,
electrodes were repositioned around the superior and inferior peripheries of
the tumor, and an additional 24 minutes of ablation were performed. At this
point, gas bubbles appeared to cover the entire tumor, and the electrodes were
removed by standard track. cauterization with a target temperature of
approximately 80°C.
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Fig. 1B —48-year-old man with hepatic hemangioma. B= oblique sagittal,
C= oblique coronal, D= oblique axial two-dimensional
reconstructions of unenhanced CT scans obtained during ablation show placement
of electrodes in triangular array within hemangioma.
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Fig. 1C —48-year-old man with hepatic hemangioma. B= oblique sagittal,
C= oblique coronal, D= oblique axial two-dimensional
reconstructions of unenhanced CT scans obtained during ablation show placement
of electrodes in triangular array within hemangioma.
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Fig. 1D —48-year-old man with hepatic hemangioma. B= oblique sagittal,
C= oblique coronal, D= oblique axial two-dimensional
reconstructions of unenhanced CT scans obtained during ablation show placement
of electrodes in triangular array within hemangioma.
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Fig. 1E —48-year-old man with hepatic hemangioma. Longitudinal sonographic
image of right lobe of liver before ablation shows large hyperechoic
hemangioma. Because of location of hemangioma, intercostal approach was
necessary.
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Fig. 1F —48-year-old man with hepatic hemangioma. Longitudinal sonographic
image obtained soon after initiation of ablation shows development of
hypoechoic region around electrodes that may represent evolving thrombus
within vascular spaces of hemangioma.
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Fig. 1G —48-year-old man with hepatic hemangioma. Longitudinal sonographic
image obtained later in ablation session shows evolution of ablation zone to
more typical appearance: gas bubbles infiltrating and obscuring ablated region
because of dirty acoustic shadowing.
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Fig. 1H —48-year-old man with hepatic hemangioma. Contrast-enhanced CT scan
in portal venous phase immediately after ablation shows no enhancement within
hemangioma. Intraperitoneal 5% dextrose in water (arrowhead) is
routinely used at our institution to protect perihepatic structures in
management of peripheral liver tumors.
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Dynamic contrast-enhanced CT immediately after the procedure showed
complete ablation of the hemangioma with no residual enhancement on delayed
images and minimal damage to adjacent normal liver
(Fig. 1H). The total procedure
time, including anesthesia induction, ablation, and CT after ablation was
approximately 3 hours.
The patient tolerated the procedure well and was discharged the next day
with no significant pain. Mild ileus and a bout of gastrointestinal reflux
resolved spontaneously within a few days of the procedure. The patient was
fully recovered from the procedure within 2 weeks. Within 2 months he had
returned to a normally vigorous lifestyle with complete resolution of the
right upper quadrant pain.
Discussion
Hepatic hemangioma is rarely symptomatic but can be associated with
abdominal pain and other poorly localized symptoms. The risk of rupture,
although low, increases with tumor size and can be associated with even
trivial trauma. In this case, the large hemangioma in the right lobe appeared
to cause substantial pain with exertion, decreasing the quality of life of an
otherwise highly active person. Surgical management of symptomatic hemangioma
involves either partial hepatectomy or enucleation, both of which are
associated with substantial recovery time and morbidity. Minimally invasive
alternatives, such as percutaneous arterial embolization, radiation therapy,
and hepatic artery occlusion, also have been used to manage hemangioma but
have not proved uniformly effective
[10,
11].
Radiofrequency ablation is a rapidly developing technique for the
management of abdominal and thoracic tumors. Extensive experience with
percutaneous radiofrequency ablation in the management of malignant hepatic
tumors has accumulated worldwide. Although local control rates with a single
treatment vary with tumor size, tumor type, and proximity to major hepatic
blood vessels, the procedure is widely accepted as safe and well tolerated.
For the management of benign tumors such as hemangioma, radiofrequency is a
near ideal technology because of the cauterizing effect of tissue heating, the
small size of the radiofrequency electrodes (17 gauge), and the lack of a
requirement to ablate every malignant cell. In the past, a major issue in
adequately managing a 7.5-cm tumor would have been the long treatment time.
Multiple consecutive overlapping ablations would have been necessary, each
ablation taking 6-12 minutes in ablation time alone. After each ablation, gas
bubbles, bleeding, and edema would have limited visualization of tumor margins
and electrode placement, making the formation of precisely overlapping
ablations increasingly difficult.
We found only one report
[12] of an evaluation of the
efficacy of percutaneous radiofrequency ablation in the management of
hemangioma. Although the results were promising (nine of 12 patients reported
partial or complete resolution of symptoms), the study was limited by ablation
times as long as 125 minutes (range, 8-125 minutes), although hemangiomas as
large as 9.5 cm in diameter (range, 2.5-9.5 cm) were managed. Unfortunately,
the reporting of methods and results in the article is imprecise. The three
treatment failures were not further classified as to size of hemangioma,
patient demographic features, or other factors that might have explained a
lack of clinical response. In addition, the technique used to follow symptom
relief is not defined, and the degree and time period of symptom relief among
patients who responded are unclear. These limitations make it difficult to
draw meaningful conclusions, but the promising results support the need for
further investigation.
A 2004 case report [13]
describes ablation of a 5-cm hemangioma (49 cm3), which
necessitated three consecutive ablations with a Cool-tip cluster electrode
activated for a total of 36 minutes. Cluster electrodes are composed of three
17-gauge electrodes spaced 5 mm apart in an equilateral triangle. By way of
comparison, in our case, using three single Cool-tip electrodes, we ablated a
hemangioma with a maximal diameter of 7.5 cm (166 cm3) in 40
minutes. The ability to run three electrodes simultaneously resulted in
ablation of 339% more tissue at the cost of only four additional minutes. This
finding is consistent with data derived from animal studies in which
multiple-electrode ablation with the switching controller improved system
performance enough to ablate approximately 200% more volume than with a
conventional Cool-tip cluster electrode
[6].
To our knowledge, this report is the first description of the treatment of
a human by use of multiple-electrode radiofrequency ablation with switching
technology. The basic principles of radiofrequency ablation are the same for
single- and multiple-electrode systems. In multiple-electrode mode, the system
takes advantage of the off time built into the standard pulsing algorithm to
power additional electrodes
[7]. Each electrode is
electrically independent and can be widely spaced for simultaneous creation of
multiple ablation zones. The electrodes also can be placed close to one
another to create a single large zone of ablation
[6]. In creation of a single
ablation zone with multiple electrodes, an important consideration is the
thermal synergy caused by vascular shielding. This phenomenon can cause
disproportionately large zones of ablation that must be taken into account in
ablation of tumors close to important structures prone to thermal injury, such
as bowel and gallbladder. In this case, peritoneal instillation of 5% dextrose
in water helped limit dia-phragmatic damage and decrease pain after the
procedure [8]. As the size of
ablation zones increases with technologic improvements in radiofrequency
systems, methods of preventing collateral damage will become increasingly
important to decrease the risk of severe complications.
During ablation, we noticed an unexpected evolution of the sonographic
characteristics of the hemangioma. The hypoechoic region that developed around
the electrodes early in ablation might have reflected thrombus formation in
reaction to damage to the endothelial lining of the tumor or to the direct
thrombotic effect of heat deposition. This echo pattern is not typical of
malignant tumors managed with radiofrequency. Later in the ablation,
hyperechoic gas bubbles formed within the areas of thrombus. The relative lack
of damage to the normal surrounding liver also is unusual for radiofrequency
ablation of malignant tumors and may reflect the substantial blood flow in
normal liver compared with the sluggish flow typical of hemangiomas. The
greater flow of blood in a normal liver may protect the organ.
We describe the first, to our knowledge, case of treatment of a human by
means of multiple-electrode radiofrequency technology based on switching
between electrodes. This system appears to rapidly ablate large volumes of
tissue by increasing the duty cycle of the radiofrequency generator and taking
advantage of the thermal synergy inherent in multiple-electrode ablation.
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Introduction
Case Report
