Jay Patti
Gillian Lieberman, MD
Radiofrequency Ablation
Jay W. Patti Harvard Medical School
Gillian Lieberman, M.D.
September 2001
Jay Patti
Gillian Lieberman, MD
But first, 2 unknown quiz cases
Jay Patti
Gillian Lieberman, MDUnknown #1Diagnosis?
Spleen
Gallbladder
Liver
Jay Patti
Gillian Lieberman, MD
Situs inversus viscerum
• 1 in 10,000 to 15,000 adults in the United States
• levocardia in the presence of situs inversus.
• Can be associated with a single ventricle, pulmonary stenosis,
arterial transposition, VSDs, ASDs, atrioventricular septal
defect, anomalous pulmonary venous return, tricuspid atresia,
and pulmonary arterial hypoplasia or atresia.
• 50% of people with Primary Ciliary Dyskinesia (PCD) have
Kartegener's syndrome: situs inversus, chronic sinusitis and
otitis, and airways disease leading to bronchiectasis
• 25% of people with situs inversus have PCD
• If none of the above associated abnormalities are present then it
is usually asymtomatic
Jay Patti
Gillian Lieberman, MD Unknown #2 Diagnosis?
Jay Patti
Gillian Lieberman, MD Unknown #2
Jay Patti
Gillian Lieberman, MD Diagnosis:
THE PATIENT TOOK A BREATH
which moved the kidneys superior
and created an artifact that appears
as though there is a mass above the
left kidney. It is very important to keep
a wide angle when looking at an area
of suspected pathology. (It is
tempting to narrow ones field to the
area of interest.)
Jay Patti
Gillian Lieberman, MD
Radiofrequency Ablation
Is the process by which discrete quantities of
energy in the form of radiofrequency are deposited
in specific tissues in an attempt to cause
coagulative necrosis in a predetermined area.
(Cooking tumors in vivo)
Jay Patti
Gillian Lieberman, MD Patient History
• The 66 year old male patient was diagnosed with colon
cancer metastatic to the liver and received one treatment of
radiofrequency ablation with recurrence prior to being
referred to the interventional radiology team at BIDMC.
Jay Patti
Gillian Lieberman, MD Indication
• Radiofrequency ablation was first used in the treatment of
unresectable hepatocellular carcinoma. This patient
population provided a means to show that radiofrequency
is safe, useful, technically straightforward and inexpensive.
• Currently radiofrequency ablation is used to treat
hepatocellular carcinoma, colon metastases to the liver,
renal cell carcinoma, chordomas, osteoid osteomas,
fibroids, cutaneous metastases, and other tumors are under
investigation. It is currently FDA cleared for the “treatment
of soft tissue masses”
• Size and proximity to adjacent organs limits the use of
radiofrequency ablation.
Jay Patti
Gillian Lieberman, MD The Procedure
• Radiofrequency ablation can be preformed either percutaneously or
intraoperatively.
• The procedure is preformed under ultrasound or CT guidance. The
skin over the area of interest is cleaned with iodine and draped. It is
important to maintain sterile conditions as the resultant necrotic tissue
in the burned lesion is a nutrient rich broth for bacterial growth.
• The patient is provided with conscious sedation (benzodiazipine and
narcotic). Some patients experience severe pain during the procedure
which subsides after the treatment. Post-procedure patients may
experience a dull ache or may be pain free.
• It is also important to prevent collateral damage of adjacent organs.
Appropriate planning and intraprocedural monitoring of adjacent
structures is necessary.
• Ablation of the needle tract is believed to reduce seeding the tract.
Jay Patti
Gillian Lieberman, MD The Equipment
• THE BASICS:
A RF probe is a metal needle that is covered by a plastic material
on all but the tip of the probe. The tip makes direct contact with the
tissue in the treatment area.
• There are many different types of RF probes in use but the
two most common types are:
RITA probe - Has three, four or six umbrella shaped prongs which
can be deployed from with in the tumor.
Cool-tip - Single or multiple parallel probes that are internally
cooled during the procedure by a closed circuit cold water pump.
• Multiple grounding pads are used to complete the circuit.
Jay Patti
Gillian Lieberman, MD The Equipment
RITA Probe Radionics
http://www.radionics.com/
https://www.ritamedical.com/products.html
Jay Patti
Gillian Lieberman, MD
Pathophysiology of Tissue Damage
• The exposed tip of the probe emits radiofrequency in the range of 500
kHz. This energy excites the ions in the surrounding tissue which
through friction raises the temperature of the tissue.
• At temperatures above 50 degrees centigrade the tissue literally cooks
in vivo.
• The temperature is measured throughout the procedure by
thermometers on the exposed tips of the probe.
• Current methods of RFA have increased the area of tissue necrosis
from 1.6 cm diameter to 4-5 cm diameter.
• Temperature of 105 degrees centigrade for 10 minutes creates the ideal
sphere. Time to return to body temperature indicates quality of
treatment sphere.
• Treatment area should include a rim (margin) of healthy tissue to
reduce recurrence.
Jay Patti
Gillian Lieberman, MD Limitations
Char-Broil:
• The impedance of the tissue rises as the cellular framework becomes disrupted and the
tissues begin to char.
• The increased impedance acts as an insulation and hence isolates the energy producing
tip from more distant tissues.
Heat Sink:
• Tissue is continuously cooled by the relatively cool blood supply passing the cooking
tissue. This too prevents the heating of tissues distant from the site of treatment
Variable Heat Conduction:
• Some tumors conduct heat better than others, presumably due to vascularity and ionic
density although never specifically shown.
Neighboring Structures:
• Structures such as blood vessels use the heat sink effect as an internal protection.
Structures such as the gallbladder and loops of bowel do not have such internal defenses
and are particularly vulnerable to the increased temperatures.
Jay Patti
Gillian Lieberman, MD Working Around Limitations
Char-Broil:
• Most probes currently in use have internal safety mechanisms to limit both the increase
in impedance and temperature. The turn off or pulse (much like a microwave oven in
defrost mode) when they reach a defined level.
Heat Sink:
• The pringle maneuver is often used to reduce the heat sink effect while ablating a tumor
in the liver.
Variable Heat Conduction:
• Some tumors are better conductors of heat. This phenomenon can be beneficial in that
the tumor acts as vector for transferring heat to more tumor. Healthy tissue is hence
protected from the increased heat transferred to other malignant tissue. A cirrhotic liver
can also act as an insulator for the treatment area which aids in ablation (oven effect).
Neighboring Structures:
• Extra thermometers are often placed between the treatment area and the threatened
organ the local temperature can be monitored and treatment can be pulsed accordingly.
Jay Patti
Gillian Lieberman, MD Lost to Follow-up
The patient was lost to follow up for
five months and returned with the
following CT scan
(8 cm )
Jay Patti
Gillian Lieberman, MD The Sphere of Ablation
• Around every burn area is an area of tissue that has been heated but not killed.
This area is where most malignant cells evade ablation.
Damaged
Killed
Jay Patti
Gillian Lieberman, MD Expanding the Sphere
Current research is concentrating on creating larger yet
predictable spheres of ablation.
Injection of hypertonic fluids Chemoembolization
Multiple Probes Heat Activated Liposomes
Aimed at increasing tonicity of tissues
and decreasing impedance within
tumor
Two strike concept making the RF
area more succeptable to chemo or
vise versa.
Multiple treatment areas within the
same treatment session. This is
commonly used.
Liposomes that carry chemotherapy
across membranes can be activated by
heat.
Jay Patti
Gillian Lieberman, MD
Pretreatment with Doxorubicin
• This particular patient was chosen for a new protocol which involved
pretreatment with systemic doxorubicin.
• Patient was in the “48 hour Pre-treatment” group. Optimal timing of
treatments is currently under investigation.
• Recent studies by Goldberg et. al. (2001) in mice have showed the
ability to increase treatment area by possibly increasing the tumor cell
sensitivity to RFA.
• Diameter of treatment area has been shown to double with combined
treatment.
Jay Patti
Gillian Lieberman, MD CT Guidance
Jay Patti
Gillian Lieberman, MD Post Ablation Imaging
• Immediate post ablation imaging
has been shown to have limited
ability to correctly differentiate kill
area and residual tumor.
• The kill area will appear hypodense
and non enhancing
• The “Damaged Area” enhances as
there is vascular permeability and
inflammatory response.
• CT imaging is recommended after
2 weeks and is usually done at 6
weeks post ablation.
Jay Patti
Gillian Lieberman, MD
CT with contrast post procedure shows area of hypointesity consistent with coagulative
necrosis. Some mild enhancement can be seen in the periphery which may represent residual
tumor of inflammatory response
Jay Patti
Gillian Lieberman, MD Summary
Indication
hepatocellular carcinoma, colon metastases to the liver, renal cell carcinoma,
chordomas, osteoid osteomas, fibroids, cutaneous metastases, and other tumors
are under investigation.
Procedure
Using an insulated probe with the tip exposed, Radiofrequency is administered
at a specific site guided by CT or US.
Pathophysiology of Tissue Damage
Ionic agitation to ideal temperature Æ coagulative necrosis
Limitations and Working Around Them
Char Broil, Heat Sink, Tissue Conduction, Collateral Damage
Current RFA Research
Hypertonic Fluids, Chemoembolization, Multiple Probes, Liposomes
Jay Patti
Gillian Lieberman, MD
References
1. Goldberg SN, Saldinger PF, Gazelle GS, Huertas JC, Stuart KE, Jacobs T, Kruskal
JB. Percutaneous Tumor Ablation Increases Necrosis with Combined
Radiofrequency Ablation and Intratumoral Doxorubicin Injection in the Rat Breast
Tumor Model. Radiology 2001;220(2)420-427
2. Gazelle GS, Goldberg SN, Solbiati L, Livraghi T. Tumor Ablation with
Radiofrequency Energy. Radiology 2000;217:633-646
3. Livraghi T, Goldberg SN, Lazzaroni S, Meloni F, Solbiati L, Gazelle GS. Small
Hepatocellular Carcinoma: Treatment with Radiofrequency Ablation versus Ethanol
Ablation. Radiology 1999;210:655-661
4. MDConsult.com Surgery Text Book.
…… and many more
Jay Patti
Gillian Lieberman, MD
Acknowledgements
•Special thanks to Larry Barbaras and Cara Lyn D’amour, our Webmasters
•Dr. Gillian Lieberman
•Pamela Lepkowski
Radiofrequency Ablation
Slide Number 2
Unknown #1Diagnosis?
Situs inversus viscerum
Slide Number 5
Slide Number 6
Diagnosis:
Radiofrequency Ablation
Patient History
Indication
The Procedure
The Equipment
The Equipment
Pathophysiology of Tissue Damage
Limitations
Working Around Limitations
Lost to Follow-up
The Sphere of Ablation
Expanding the Sphere
Pretreatment with Doxorubicin
CT Guidance
Post Ablation Imaging
CT with contrast post procedure shows area of hypointesity consistent with coagulative necrosis. Some mild enhancement can be seen in the periphery which may represent residual tumor of inflammatory response
Summary
References
Acknowledgements
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