Development of a Stent-Based Electrode For Radio Frequency Thermal Ablation Procedure

Tony Richard de Oliveira de Almeida

Development of a Stent-Based ElectrodeFor Radio Frequency Thermal Ablation Procedure

Dissertação para a obtenção do Grau de Doutor em EngenhariaElectrotécnica, na especialidade de Materiais e Campo


Electrotécnica, na especialidade de Materiais e Campo Electromagnéticos

Tese realizada sob orientação do Prof. Doutor Carlos Lemos Antunes

Coimbra, 23 de Novembro de 2012

www.uc.pt

OverviewOverview

• Motivation and Objectives• Motivation and Objectives

• Experimental Work

• Preliminary Tests

• Characterization of the Induced Lesion

• Numerical Analysis of the Geometry of the Electrode

• RF Ablation of a Cholangiocarcinoma: Numerical Simulation

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• RF Ablation of a Cholangiocarcinoma: Numerical Simulation

• Conclusions

• Future Work

Motivation and ObjectivesMotivation and Objectives

• Cancer is the world’s second biggest killer after • Cancer is the world’s second biggest killer after

cardiovascular disease

• Liver cancer is the third most common cause of death

• Colorectal cancer is the fourth most common cause of death.

• Oesophageal cancer is the sixth most common cause of death

• Diagnosis on an advanced stage

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• Palliative cares can be considered

• Self-expanding metallic stents (SEMS)


• Nitinol stents are used to reduce stricture problems• Nitinol stents are used to reduce stricture problems

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• In the last decades, radiofrequency (RF) energy has been • In the last decades, radiofrequency (RF) energy has been

increasingly used as an alternative method for minimally

invasive therapy for the treatment of primary and secondary

malignancies

• Primary and metastatic liver tumor

• Small renal carcinomas

• Lung

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• Lung

• Breast

• Bone tumors


• Several electrode • Several electrode

solutions have been

developed attempting to

heat a larger and regular

volume of tissue

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P. Mulier, et al., "Electrodes and multiple electrode systems for radiofrequency ablation: a proposal for updated terminology," European Radiology, vol. 15, pp. 798-808, April 2005.


• As nitinol stents can be used to reduce stricture problems of

duct organs, these can be considered as potential

electrodes for hyperthermia treatments

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Experimental WorkExperimental Work

• To verify the use of a commercial nitinol stent as RF ablation • To verify the use of a commercial nitinol stent as RF ablation

electrode

• To test a practical procedure for deploying the stent in place

and connect it to the RF power generator

• To characterize the biological samples used , as well as the

lesions induced, for numerical simulation

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lesions induced, for numerical simulation

• To validate the numerical model considered


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Connection to the RF power Connection to the RF power generator through a BI-PAL endoscopic biopsy forceps

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• Connection to the RF power generator through a BI-PAL • Connection to the RF power generator through a BI-PAL

endoscopic biopsy forceps

• Results obtained very similar to those in the preliminary tests

• The forceps did not show any damage or deformation after the

RF ablation

• It did not heat significantly and it could be used repeatedly

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• It did not heat significantly and it could be used repeatedly

Characterization of the Induced LesionCharacterization of the Induced Lesion

• Ex Vivo experimentation• Ex Vivo experimentation

• Bobine livers collected 2 hours after abating the animals

• Measurement of the electrical conductivity

• Numerical simulation

Thermoelectrical coupled field problem

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σ∇ ⋅ ∇ = 0V

ρ ∂ = ∇ ⋅ ∇ + ⋅ − − −∂

( )b b m

Tc k T h T T Q

tJ E



• Ex Vivo experimentation• Ex Vivo experimentation

• Bobine livers collected 2 hours after abating the animals

• Biliary self-expandable metallic stent

• Connection through modified BI-PAL biopsy forceps

• Temperature reading at 1 and 2 cm from the electrode

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• Measurement of the electrical conductivity

• Applied voltage of 25 to 100 V

• Procedures of 5, 10 and 15 minutes


50 V50 V50 V50 V

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5 min5 min 10 min10 min 15 min15 min


75V75V75V75V

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100 V100 V100 V100 V

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• Numerical simulation• Numerical simulation

σ∇ ⋅ ∇ = 0V

ρ ∂ = ∇ ⋅ ∇ + ⋅ − − −∂

( )b b m

Tc k T h T T Q

tJ E


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5 min5 min 15 min15 min


50 V50 V

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100V100V


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Impact of Geometry Impact of Geometry

• The proposed electrode is made from interlaced nitinol • The proposed electrode is made from interlaced nitinol

wires (helices)

• Most of commercially available electrodes resembles this

geometry

• It is intended to evaluate the effect of the geometry of the

stent-based electrode on the temperature distribution

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stent-based electrode on the temperature distribution

• Mesh density is varied according the number of helices

• Applied voltages from 25 to 100 V during 15 min


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50 V50 V 75 V75 V


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4 elements @50V50ºC isothermal4 elements @50V50ºC isothermal

24 elements @50V50ºC isothermal

24 elements @50V50ºC isothermal


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4 helices40 s @50 V4 helices40 s @50 V

24 helices40 s @50 V24 helices40 s @50 V

RF Ablation of a Cholangiocarcinoma RF Ablation of a Cholangiocarcinoma

• Finite element modelling of a stent-based electrode located • Finite element modelling of a stent-based electrode located

in the common bile duct

• Presence of major blood vessels

• Evaluation of the volume of the lesion – size and shape

• It was considered the modification of the electrical

conductivity of the tissue for altering the energy deposition

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conductivity of the tissue for altering the energy deposition

in the tissue


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σ∇ ⋅ ∇ = 0V

ρ ρ∂ = ∇ ⋅ ∇ + ⋅ − − − − ⋅∇∂

( )b b m b b b

Tc k T h T T Q C T

tJ E u

Chen and Holmes model


• RF ablation without saline infusion• RF ablation without saline infusion

• RF ablation with saline infusion

• Tumour segmented – middle segment with higher electrical

conductivity

• Diffusion of the saline solution

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RF Ablation of a CholangiocarcinomaRF Ablation of a Cholangiocarcinoma

No saline No saline

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20V20V


No saline No saline

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22V22V


No saline No saline

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35V35V


No saline No saline

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With salineWith saline

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With saline – Segmented TumourWith saline – Segmented Tumour

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ks = 3, after 300 sks = 3, after 300 s


With saline - SpreadingWith saline - Spreading

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ks = 3, s = 0.0017, after 300 sks = 3, s = 0.0017, after 300 s



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ks = 3, s = 0.00675, after 300 sks = 3, s = 0.00675, after 300 s



www.uc.pt24V, ks = 224V, ks = 2

ConclusionsConclusions

• It is believe that contributions to the area of RF ablation are • It is believe that contributions to the area of RF ablation are

introduced in this work

• It is proposed a stent-based electrode for hyperthermia

treatments of tumours located in tubular organs

• Experimental work showed that nitinol self-expandable

stents can be considered as potential electrodes for RF

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stents can be considered as potential electrodes for RF

ablation

• The results from numerical simulations were in good

agreement with those obtained experimentally

ConclusionsConclusions

• Considering that most stents available in the market • Considering that most stents available in the market

resemble the configuration considered, those can be

regarded as potential electrodes for RF ablation

• Numerical simulation of a RF ablation procedure on a

cholangiocarcinoma evinced that convective heat transfer

due to the major blood vessels has a significant impact on

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due to the major blood vessels has a significant impact on

temperature distribution

• It is possible to obtain a more regular volume considering

saline infusion. Still, the effect of convective heat is

significant

Future WorkFuture Work

• Further Ex Vivo and In Vivo experimentation is required for a • Further Ex Vivo and In Vivo experimentation is required for a

better assessment of the potential of the proposed

electrode

• Investigation can be directed to other solutions avoiding

physical connection to a power generator:

• Heating the stent with an external magnetic field

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• Heating the stent with an external magnetic field

• Nanoparticle fluid combination

• Alternative applications like electroporation

PublicationsPublications• C. F. L. Antunes, T. R. O. Almeida, N. Raposeiro, B. Gonçalves, and P. Almeida, “Effects of the geometry of a tubular

electrode on the temperature distribution in biological tissue,” in 14th Biennial IEEE Conference on Electromagnetic Field electrode on the temperature distribution in biological tissue,” in 14th Biennial IEEE Conference on Electromagnetic Field Computation, Chicago, USA, 2010

• C. F. L. Antunes, T. R. O. Almeida, N. Raposeiro, B. Gonçalves, and P. Almeida, “Thermal ablation in biological tissue using tubular electrode,” in 14th Biennial IEEE Conference on Electromagnetic Field Computation, Chicago, USA, 2010

• C. F. L. Antunes, T. R. O. Almeida, N. Raposeiro, B. Gonçalves, and P. Almeida, “A tubular electrode for radiofrequency ablation therapy,” in ICBET 2010 - International Conference on Biomedical Engineering and Technology, Paris, France, 2010.

• C. F. R. L. Antunes, T. R. Almeida, N. Raposeiro, B. Gonçalves, P. Almeida, and A. Antunes, “A tubular electrode for radiofrequency ablation therapy,” World Academy of Science, Engineering and Technology, no. 70, pp. 517–523, 2010

• C. F. L. Antunes, T. R. Almeida, and N. Raposeiro, “Finite element modeling of cholangiocarcinoma radiofrequency

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• C. F. L. Antunes, T. R. Almeida, and N. Raposeiro, “Finite element modeling of cholangiocarcinoma radiofrequency ablation,” in 10th International Conference of the European Bioelectromagnetic Association, Rome, Italy, 2011

• C. F. L. Antunes, T. R. Almeida, and N. Raposeiro, “Inducing thermal lesion on a cholangiocarcinoma considering a saline-enhanced radiofrequency ablation,” in EHE2011 – 4th International Conference on Electromagnetic Fields, Health andEnvironment, Coimbra, Portugal, 2011

• C. F. L. Antunes, T. R. Almeida, N. Raposeiro, B. Gonçalves, and P. Almeida, “Determination of lesion volume induced in biological tissue using a tubular electrode for radiofrequency ablation - numerical and experimental analysis,” in EHE2011 –4th International Conference on Electromagnetic Fields, Health and Environment, Coimbra, Portugal, 2011

PublicationsPublications• C. F. L. Antunes, T. R. Almeida, and N. Raposeiro, “Producing a regular volume for thermal lesion on a cholangiocarcinoma

considering a saline-enhanced radiofrequency ablation,” in XV International Symposium on Electromagnetic Fields in considering a saline-enhanced radiofrequency ablation,” in XV International Symposium on Electromagnetic Fields in Mechatronics, Electrical and Electronic Engineering. ISEF 2011, Funchal, Madeira Island (Portugal), 2011

• C. F. R. L. Antunes, T. R. Almeida, and N. Raposeiro , “Saline–enhanced RF ablation on a cholangiocarcinom a: a numerical simulation,” COMPEL – The International Jou rnal for Computation and Mathematics in Electrical and Electronic Engineering, vol. 31, no. 4, pp. 1055–10 66, 2012

• C. F. R. L. Antunes, T. R. O. Almeida, and N. Rapose iro, “Using a tubular electrode for radiofrequency abl ation: numerical and experimental analysis,” COMPEL – The In ternational Journal for Computation and Mathematics in Electrical and Electronic Engineering, vol. 31, no. 4, pp. 1077–1086, 2012

• C. F. R. L. Antunes, T. R. O. Almeida, and N. Rapose iro, “Producing a regular volume for thermal lesion on a cholangiocarcinoma considering a saline–enhanced rad iofrequency ablation,” Electrical Review, vol. 38, n o. 7b, pp. 24 – 27

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pp. 24 – 27 • 2012

• C. F. R. L. Antunes, T. R. O. Almeida, N. Raposeiro, B. Gonçalves, and P. Almeida, “Intraductal RF/stent ablation,” in CIRSE 2012 – Cardiovascular and Interventional Radiological Society of Europe, Lisbon, Portugal, 2012.

• C. F. R. L. Antunes, T. R. O. Almeida, N. Raposeiro , B. Gonçalves, and P. Almeida, “Using self-expandable metallicstents as electrodes for radiofrequency ablation (RF) in tubular organs: Ex vivo experimental preliminary research [submitted],” SIR2013 – Society of Interventional Radiol ogy, New Orleans, LA (USA), Apr. 13-18, 2013


Development of a Stent-Based ElectrodeFor Radio Frequency Thermal Ablation Procedure

Dissertação para a obtenção do Grau de Doutor em EngenhariaElectrotécnica, na especialidade de Materiais e Campo


Electrotécnica, na especialidade de Materiais e Campo Electromagnéticos

Tese realizada sob orientação do Prof. Doutor Carlos Lemos Antunes

Coimbra, 23 de Novembro de 2012

www.uc.pt

Health & Medicine

Development of a Stent-Based Electrode For Radio Frequency Thermal Ablation Procedure