2.TRANSPLANTASYON 4. SUNUM

8/14/2019 2.TRANSPLANTASYON 4. SUNUM

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RFA for big liver tumoursRFA for big liver tumours

Dr Jean-Brice GAYETDr Jean-Brice GAYET

Dpartement dimagerie mdicaleDpartement dimagerie mdicale


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What are we talking about ?


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RF Ablation: 1996RF Ablation: 1996

Low-power generator (50 W)

3-cm-diameter ablation volume


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RF Ablation: 2003RF Ablation: 2003

High-power generator (250 W)

5-7 cm diameter Ablation Volume


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The Gold StandardThe Gold Standard

GOLD STANDARD

IS THE

SURGICAL RESECTION


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Why ?Why ?

The Motto of the surgeons basically is

IF IN DOUBT, CUT IT OUT!


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Approximately 80% of LiverApproximately 80% of Liver

Tumours are unresectableTumours are unresectable

Bilateral or multiple tumours

Difficult position Liver Health

Systemic health

Anything else you can think of


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What do you do to commitWhat do you do to commit

tumouricide on the rest?tumouricide on the rest?

Poison them

Starve them

Freeze them

Cook them


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Resection is made More Possible ifResection is made More Possible if

Combined with Other TechniquesCombined with Other Techniques

Resect AND Cook Resect AND Freeze

Resect AND Poison

Resect AND Poison AND cook

And so on


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Combine Resection and OtherCombine Resection and Other

ModalitiesModalities

Ablation treatments do NOT replace allresections, it enhances the possibility

of resection in combination with them

Multidisciplinary decisions +++


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Back to RFA


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First, HEAT it !


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Basic principle : Closed LoopBasic principle : Closed Loop

CircuitCircuit

Generator Dispersive electrode(ground pad)

RF needle

Input current

Output current


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Making RF LesionsMaking RF Lesions

High frequency alternating current

Ionic agitation

Frictional heating Heat generated concentrated at active electrode

Tissue near electrode is source of heat

No heat flows directly from the device


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Principles of RF Energy DeliveryPrinciples of RF Energy Delivery

Radiofrequency Probes heat by ionic

agitation only within 2 mm of the probe

surface

Tissue heating beyond this is by HEAT

conduction only


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Applied to BLTApplied to BLT

Pb of conducting heat against the convection

cooling of blood flow of a larger volume.

Requires the directly heated tissue (within 2mm of probe) to be as hot as possible

Pb of tissue dessication : will not conduct

electricity away from the probe hence

prematurely halting process.


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Stages of RF AblationStages of RF Ablation

Frictional

Heating

Conductive

Heating

Conduction Over Time . . .


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Key Ablation Process ComponentsKey Ablation Process Components

Heat generation Distance (r)

Current (I) Time (T)

Lesion size

Temperature Electrode size


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The extent and nature of thermal injury aredependent on two important factors, Temperature

& RF Application Duration.

(V. Krishnamurthy, Applied Radiology, Oct. 2003)


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Lesion Size Depends onLesion Size Depends on

Electrode Size and TemperatureElectrode Size and Temperature

0

2

4

6

8

30 50 70 90 110

Body

Temp

Cell

Death

Lesion

Size(cm)

Electrode Temperature (C)

SB XL &

Semi-Flex

(3 cm)

StarBurstSDE (2 cm)

SB XL &Semi- Flex

(5 cm)

SB XLi

(7 cm)


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Souvenirs, souvenirsSouvenirs, souvenirs


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Prior to the newer probesPrior to the newer probes

How (the hell) did people do this ?


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The Overlapping Mode The Overlapping Mode


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RF ablation with use of a regular five-sided prism model. A, Maximum transverse view of the tumor: Five target sites are determined to

guide electrode insertions. B, Same section asA: Five ablations are performed in the middle part of the

tumor. C, The section perpendicular toA: Two additional ablations are performed at the

two poles of the tumor. The tumor can be effectively ablated with seven ablationspheres.xindicates the target site of the ablationthat is, the ablation spherecenter.

Chen VIR 2004Chen VIR 2004


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Predictable Lesions goldPredictable Lesions gold

standardstandard Temperature

Monitor heat Thermocouples (Real-time measurement) Check temps at end to ensure cell death

Monitor duration Consistent & Reproducible


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Methods of Control of EnergyMethods of Control of Energy

DeliveryDelivery Global impedance measurement, no regional

differentiation. Global impedance measurement and indirect

central temperature measurement by coolingwater temperature. Direct measurement of regional peripheral

temperatures with power control feedbacksystem.

Direct regional peripheral temperature endpoint,control of rehydration by impedance during fullpower application.


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A few medical and non-medical considerations


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Radionics / Tyco

200 Watt generator that works by limiting

power (necessary to prevent desiccation of

tissue, due to excessive temperature, thataborts the procedure) in two ways

Duty cycle.

Internal cooling of the Radionics probe.


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The power is fully switched on & off

frequently, the ratio of on to off giving an

average power.

This causes shock waves that the patient

can sometimes feel. This is why it was

thought that general anaesthesia was

necessary.


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Excess power is removed by cooling the

tissue immediately in contact with the

probe by cooling the probe itself. This isanalogous to controlling your cars speed

with the brakes instead of the

accelerator.


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Remember that the energy deposited in the ablationvolume is useless until converted into the heat thatactually does the work

Measuring temperature is therefore the ONLY way toknow & control what is happening. Radionics probesonly measure the temperature of the cooling water, or, ifthat is switched offONLY the temperature of theCENTRE of the ablation. It is the PERIPHERAL

temperatures that are critical Radionics only senses the need to reduce power by total

impedance, not by temperature, nor with any zonaldifferential information.


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Boston

Power control is only by total impedance withoutany temperature sensing nor any regionalinformation. Power is manually adjusted by the

physician, needing constant attention.

The expanding probe tines are one third thethickness of RITAs which carry electrical circuits forthe temperature sensors and/or saline for infusion.They are much more easily diverted from theexpected deployment pattern.


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The probe has to be fully deployed at all times, sodifferent ablation sizes can only be accomplished byusing multiple probes, unlike RITAs probes which canbe scaled to different deployments (sizes) even duringan ablation if the clinical situation requires it.

There is no Cool-Down quality control (no temperaturesensing), so immediate contrast scanning is the onlyway to ensure complete ablation without risking anotherlater procedure.


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RITARITA

The whole unique point of RITAs technology is theuse of peripheral temperature sensing and feedbackpower control.

RITA uses analogue power controlled by temperaturefeedback and on commencement only uses enough powerto raise tissue temperatures by 1.5 C per second to preventshock waves. So local anaesthesia (& conscious sedation)

is usual when using RITA routinely in the liver.


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Because of the volumes & geometry involvedcoagulating the periphery is much more difficultthan the centre of the lesion. This is why

PERIPHERAL temperature sensors are important.If the cooling effect of blood flow has, more easilyinitially, been stopped in the centre, then it iseasier to ablate the periphery

by quickly & easily coagulating the centre first,subsequent extentions of the ablation outwardsproceed more easily so the entire ablation takesless time.


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Gold Standard of Lesion FormationGold Standard of Lesion Formation

Temperature MonitoringTemperature Monitoring Direct measurement of thermal cell death

In neurology temperature monitoring has provenitself safer and more effective than other

techniques (Cosman, Appl Neurophysiol 1988)

Cardiac catheter lesion size best correlated with

tissue-electrode interface temperature (Langberg,Circulation 1992)

In liver ablation electrode tip temperature is an

important index for efficient power control. (Chung,invest Radiol 1997)


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Now, you still need toCOOL it down


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Micro-Infusion Enhanced AblationMicro-Infusion Enhanced Ablation

Purpose Larger ablations (7cm) Shorter ablation times

Use Conduction (saline solution) Tissue hydration

Temperature

Precision Reliability Consistency


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Practical Limit to Size of SinglePractical Limit to Size of Single

AblationAblation Non-microinfusion expanding probes 5 cm

Non-microinfusion non-expanding

(cluster) cooled probes 5 cm Micro-infusion expanding probes 7 cm

Macro-infusing non-expanding probes uncontrolledlocation & size


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XLi infusion antennae(RITA)


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Was it REALLY useful ?


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Remember that one ?Remember that one ?


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Other solutionsOther solutions


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De Baere AJR 2001De Baere AJR 2001


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Bipolar / multipolar

no grounding pad (an active electrode and a closelyplaced grounding electrode).

The heat is generated not only around the activeelectrode, but also around the grounding electrode andin the space between the two. This is in contrast to the monopolar electrode, where heat is

generated only at the active electrode. Early clinical experience demonstrates that bipolar needles

produce a larger coagulation volume of 3-cm diameter by asingle application alone.

Absence of a grounding pad eliminates the risk of

grounding pad burns.


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Pulse RF ablation

increasing the volume of coagulation by increasing theRF energy deposition.

In this technique, higher energy deposition is alternated withlower energy deposition.

During periods of low energy deposition, the tissue around theelectrode cools down, allowing for even higher energydeposition during the next cycle of ablation.

This method allows for deeper heat penetration,creating a larger ablation zone.


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Combine TreatmentCombine Treatment


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RFA Angiographic BalloonRFA Angiographic Balloon

OcclusionOcclusion

Metastasis

Vascular occlusion choice : size of the metastasis

localisation / vessel

de Baere. AJR 2002


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TACE + RFATACE + RFA

Large tumors

Larger necrosis

more important Post

RFA syndromePOST TACE + RFAPOST TACE + RFA

PRE RFAPRE RFA


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To-be resolved question: how and when ?

TACETACE thenthen RFARFA

TACE + RFATACE + RFA

RFARFA thenthen TACETACE (15 days later)(15 days later)


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For What Big Tumours ?


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IndicationsIndications

HCC

Colo-rectal Liver Metastasis

Limited number of lesions

Size < 5 cm

Non resectable tumor

No extra hepatic lesions


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Metastasis - CI to SurgeryMetastasis - CI to Surgery

Lower rate compared to HCC cirrhotic

patients

Major liver resection

with or without portal embolisation Re-hepatectomy for patients with colon

cancer


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MetastasisMetastasis

Surgery Before

During

After Chemotherapy


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Chopra AJR 2003Chopra AJR 2003

C+CT immediatelyC+CT immediately

after procedureafter procedure

MetastasisMetastasis

IVb segmentIVb segment


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OtherOther

Hepatic adenoma / adenocarcinomaHepatic adenoma / adenocarcinoma

Endocrine Metastasis ?Endocrine Metastasis ?

Rare Unique Liver Breast Metastasis ?Rare Unique Liver Breast Metastasis ?


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What about complications ?What about complications ?

45 mm HCC Bilioma45 mm HCC Bilioma 44 months44 months

Kim AJR 2004


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ConclusionConclusion

Lack of Datas specifically on Large

Liver Tumour RFA

Combined Treatments

Technological Advances

2.TRANSPLANTASYON 4. SUNUM

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