Download Percutaneous Ablation of Hepatocellular Carcinoma

Percutaneous Ablation of
Hepatocellular Carcinoma:
A Pictorial Review
Ellen Cheang, MD
Jonah Hirschbein, MD
Radiology Resident
University of California Davis
Sacramento, California
Radiology Resident
University of California Davis
Sacramento, California
Bijan Bijan, MD, MBA, CIIP
Professor of Radiology & Nuclear Medicine (WOS)
University of California Davis
Sacramento, California
Nothing to disclose
Jonah Hirschbein, MD
Nothing to disclose
Bijan Bijan, MD, MBA, CIIP
Nothing to disclose
Cheang, Hirschbein & Bijan
Ellen Cheang, MD
Society of Abdominal Radiology - 2016
Disclosure
Surgical resection and orthotopic liver transplantation have curative
potential but fewer than 20% of patients are suitable candidates.
Percutaneous thermal ablation is considered the optimal treatment
of choice for focal unresectable HCC of early stage, reduction of
tumor burden in more advanced disease and as a bridge to
transplantation.
Imaging follow up after ablation is crucial to ensure that disease
recurrence is detected early.
MRI in particular has proven to be a powerful tool in post-ablation
imaging follow up.
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Hepatocellular carcinoma (HCC) is a common cancer with high
mortality and morbidity.
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Background
Review the appropriate post-ablation imaging follow up and
expected findings with an emphasis on MRI.
Illustrate the appearance of post-ablation disease recurrence.
Discuss the potential pitfalls of post-ablation imaging follow up.
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Compare and contrast radiofrequency ablation (RFA) and
microwave ablation (MWA) as treatment options for
hepatocellular carcinoma (HCC).
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Learning Objectives
MWA
Principle
Electric current in the
radiofrequency range producing
heat-based coagulation necrosis 1
Electromagnetic energy creates a
rapid and homogeneous heating 
coagulation necrosis 2
Heat sink effect
More heat sink effect  size of
ablation less predictable 3
Less heat sink effect  more
predictable ablation zone 4
Size of tumor
-
- Can use alone to treat tumors 5-8
cm 6
Procedural time
Longer
Shorter
Indications
Patients with early HCC who are
ineligible for surgical treatment due
to comorbidities, and in patients
who refuse resection or when there
is a need to preserve liver function.
Same
Effective for tumors <3 cm
RFA combined with TACE is
recommended for tumors > 3
cm 5
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RFA
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Comparison of RFA and MWA
MWA
Contraindications
Presence of metallic device,
decompensated ascites,
severe bleeding diathesis
(platelet <50,000),
hemostatic compromise7
same
Relative contraindications
Lesions near GI, biliary
system and heart
same
Rate of major
complications
2.2% 8
2.9% 9
Complete ablation rate
93% 10
95% 10
Local recurrence rate
5.2-20.9% 11-15
3.9-19% 11-15
Survival rate
68-100% at 1st year
24-78% at 4th year 11-15
68-100% at 1st year
24-78% at 4th year 11-15
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RFA
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Comparison of RFA and MWA
At most institutions, a 3 or 4-phase contrast enhanced CT is
performed immediately or within 1 month after ablation to assess
the technical success of treatment.
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Post-treatment imaging
MRI is more sensitive to detect smaller residual and recurrence
tumors with sensitivity up to 84% with MRI and 47% with CT
respectively 16-17.
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If ablation was technically successful, multiphase CT or MR may
be repeated at a 3-month intervals for evaluation of recurrence.
Abnormal findings
Ablation zone
Residual disease
Periablation zone
Recurrent disease
Biliary changes
Tumor seeding
Vascular changes
Biliary complications
Perihepatic changes
Vascular complications
Infection
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Normal Findings
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Post-treatment Imaging
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Normal post-treatment
changes
CT findings
MR findings
-
Refers to the area of
coagulative necrosis
induced by RFA
-
-
-
Should encompass the
treated tumor with a
circumferential margin of
5-10 mm around the tumor
***
Immediate post-op: The ablation
zone appears hypoattenuating or
heterogeneously
hyperattenuating because of
coagulative necrosis
Initial follow-up: the
ablation appears
hyperintense on T1,
hypointense on T2 due to
coagulative necrosis and
blood products.
-
Initial follow-up: the ablation
zone becomes homogeneously
hypoattenuating over time on
NECT.
The shape can be irregular due
to heat sink effect.
-
Marked hyperintensity on
T2 suggestive liquefactive
necrosis or biloma
-
No enhancement
-
Teaching points
-
Comparison of pre- and post ablation images is crucial to determine successful ablation. Ablation zone
should have circumferential margin of 5-10 mm around the tumor.
-
Tiny air bubbles caused by tissue necrosis may be seen within ablation zone immediately after RFA. This
finding should not mistaken for infection or abscess
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General characteristics
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Ablation zone
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Case 1: Ablation zone
Figure 1: 58 yo male who underwent RFA for hepatocelluar carcinoma (HCC)
A: Sonographic image of a patient being treated with radiofrequency ablation for hepatocellular carcinoma.
B: Axial CECT demonstrates a non-enhancing ablation zone indicating treatment success.
B
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A
D
E
F
Figure 1: 58 yo male who underwent RFA for hepatocelluar carcinoma (HCC)
Axial non-contrast T1 (C), early contrast enhanced arterial phase (D), delayed phase (E) and T2
images obtained 1 month after RFA reveal non-enhancing oval ablation zone. The findings suggests
adequate treatment without residual disease.
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C
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Case 1: Ablation zone
CT findings
MR findings
-
-
NECT: a sharply marginated,
hypoattenuating rim
-
T2: a subtle hyperintense
rim suggestive of
periablation edema
-
CECT: an ill-defined, thin rim
of enhancement on arterial
phase and sometimes persists on
portal venous phase.
-
post contrast MR: an illdefined, thin rim of
enhancement on arterial
phase and sometimes
persists on portal venous
phase
-
Periablation hyperemia due
to inflammatory reaction
and granulation tissue
formation induced from
thermal injury.
Peri-ablation changes
should progressively
decrease 4-9 months after
ablation.
Teaching points
-
The pattern of periablation enhancement is different from that of tumor, which is thick and nodular.
However, residual/recurrent tumor may be subtle and difficult. Careful comparison of pre- and postablation images is crucial and close follow up is necessary in equivocal cases.
-
Equivocal cases on CT or MR can be evaluated with PET/CT.
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General characteristics
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Peri-ablation changes
B
C
D
Figure 2: 68 yo M who underwent RFA for HCC.
A: Axial CECT image obtained 1 month after RFA demonstrates hypoattenuting ablation zone with an ill-defined
circumferential enhancement representing periablation hyperemia.
B: T2 weighted image obtained 3 months after RFA reveal a rim of hyperintensity represents periablation edema.
C& D: Early arterial image demonstrate a very subtle rim enhancement which persists on delayed phase.
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A
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Case 2: Periablation changes
F
G
H
Figure 2: 68 yo M who underwent RFA for HCC.
E: Follow up CECT image obtained 9 months after RFA no longer reveals rim enhancement.
F, G & H: Follow up T2 weighted, early arterial and portal venous contrast enhanced MR images obtained 12
months after RFA no longer demonstrate rim of T2 hyperintensity and rim enhancement.
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E
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Case 2: Periablation changes
CT findings
MR findings
-
-
NECT/CECT: focal biliary
dilatation adjacent to the
ablation zone.
-
T2: hyperintense focal
biliary dilation adjacent to
the ablation zone
-
No enhancement
-
No enhancement
-
Biliary changes after RFA
include biliary dilatation,
gallbladder edema and
hemobilia.
Transient bile duct dilatation
peripheral to the ablation
zone is a common finding,
which resolves as the ablation
decreases in size.
Teaching points
-
Persistent or increasing biliary dilation suggests irreversible damage to the bile ducts during RFA
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General characteristics
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Biliary changes
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Case 3: biliary dilatation
Figure 3: 60 yo female who underwent RFA of HCC in the left hepatic lobe.
A: Axial contrast enhanced CT obtained 3 months after RFA reveal mild biliary dilatation adjacent
to the ablation zone.
B: T2 weighted image obtained 6 months after RFA demonstrates persistent biliary dilatation
adjacent to the ablation zone.
B
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A
CT findings
MR findings
-
-
NECT: hyperattentuating
collection within the ablation
zone.
-
-
No enhancement
-
Small peripheatic hematoma
caused by mechanical injury
to hepatic or perihepatic
vesssels by electrodes
Variable appearance on
MRI depending on the age
of hemorrhage during and
after ablation
Mild or moderate bleeding
with stability in size is
reassuring in
hemodynamically stable
patient.
Teaching points
-
When hemorrhage is seen immediately after RFA, short term follow up within 24 hours may be indicated
to ensure stability in size.
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General characteristics
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Hematoma
Figure 4: 54 yo M who underwent RFA for HCC.
A: NECT obtained immediately after RFA demonstrates hyperattentuating hemorrhage within the
ablation zone.
B: Arterial phase CT immediately after RFA demonstrates hemorrhage without enhancement.
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Case 4: hematoma
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Abnormal post-treatment
changes
CT findings
MR findings
-
Caused by incomplete
coverage of tumor because of
large tumor size, inaccurate
targeting, satellite nodules or
heat sink effect.
-
-
-
MR (89%) offers a higher
sensitivity than CT (49%) in
detecting residual disease 1617.
CECT: residual disease
appears as an eccentric,
irregular, peripheral
enhancing nodule with early
arterial enhancement and
washout on delayed phase.
Focal, nodular T2
hyperintense focus adjacent
to the ablation zone with
corresponding early arterial
enhancement and washout
on delayed phase is
suggestive of residual
disease.
Teaching points
-
Careful comparison of pre- and post-ablation imaging are essential to evaluate for residual disease.
-
MR is more sensitive than CT in detecting residual disease.
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General characteristics
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Residual disease
B
C
D
Figure 5: 59 yo female who underwent RFA for HCC.
A & B: CECT obtained immediately after RFA demonstrates an early arterially enhancing nodule adjacent to the
ablation zone suspicious for residual disease. However, this nodule does not demonstrate wash out on delayed phase.
C & D: Dynamic contrast MR images obtained 3 months RFA confirms residual disease with early arterially
enhancement and washout on delayed phase.
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A
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Case 5: Residual disease
CT findings
MR findings
-
Development of tumor on follow
up imaging after tumor was
successfully ablated.
-
-
-
Recurrence manifest as a new
peripheral enhancing nodule.
-
Recurrence can also appear as an
irregular or asymmetric
thickening along the margin of
the ablation zone or as
new/progressively enlargement
of the ablation zone.
CECT: recurrence
appears as a new
eccentric, irregular,
peripheral enhancing
nodule with early arterial
enhancement and
washout on delayed
phase.
New focal, nodular T2
hyperintense focus adjacent
to the ablation zone with
corresponding early arterial
enhancement and washout
on delayed phase is
suggestive of recurrence.
Teaching points
-
The time period of development of recurrence can be variable and therefore regular follow up CT or MRI
is essential to assess for recurrence.
-
PET/CT can be an important diagnostic tool for equivocal cases.
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General characteristics
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Recurrent disease
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Case 6: recurrent disease
Figure 6: 49 yo female who underwent RFA for HCC.
A: Contrast T1 image prior to RFA reveals an arterially enhancing mass in the right hepatic lobe consistent with HCC.
B: CECT obtained 3 months after RFA demonstrates successful ablation without evidence of residual disease.
C & D: Dynamic contrast MR images obtained 12 months after RFA demonstrate a new nodule adjacent to the ablation
site with early arterially enhancement and washout on delayed phase, consistent with recurrence.
The time period of development of recurrent disease can be variable and
subtle. Therefore, regular follow CT and MR is essential for surveillance.
When CT and MR findings are equivocal, PET/CT can be an important
diagnostic method for early detection of recurrent disease.
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MR offers higher sensivity than CT in detecting residual/recurrence
disease because MR has better tumor tissue contrast.
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CT and MR pitfall
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Case 7: CT and MR pitfall
Figure 7: 63 yo male who underwent RFA for HCC.
A: CECT obtained 10 months after RFA did not show recurrence.
B & C: Dynamic contrast enhanced MR obtained 9 months after RFA demonstrates a new arterially enhancing
nodule superior to the ablation suspicious for recurrence. However, this nodule does not definitively reveal wash out
on delayed phase.
D: PET/CT confirmed recurrence at the ablation site.
MRI in particular has proven to be a powerful tool in postablation imaging follow up.
Detection of subtle recurrence can be extremely challenging.
PET/CT serves as an important diagnostic tool for equivocal
cases.
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Percutaneous ablation has emerged as a powerful and
versatile treatment option for HCC. Appropriate
interpretation of post-ablation imaging is crucial in the
optimization of patient outcomes, ensuring that recurrence is
caught as early as possible.
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Summary
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References
Radiology Resident
University of California Davis
Sacramento, California
[email protected]
Jonah Hirschbein, MD
Radiology Resident
University of California Davis
Sacramento, California
[email protected]
Bijan Bijan, MD, MBA, CIIP
Professor of Radiology & Nuclear Medicine (WOS)
University of California Davis
Sacramento, California
[email protected]
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Ellen Cheang, MD
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Contact