The effects of metallic implants on electroporation therapies: feasibility of irreversible electroporation for brachytherapy salvage.
OBJECTIVE
Electroporation-based therapies deliver brief electric pulses into a targeted volume to destabilize cellular membranes. Nonthermal irreversible electroporation (IRE) provides focal ablation with effects dependent on the electric field distribution, which changes in heterogeneous environments. It should be determined if highly conductive metallic implants in targeted regions, such as radiotherapy brachytherapy seeds in prostate tissue, will alter treatment outcomes. Theoretical and experimental models determine the impact of prostate brachytherapy seeds on IRE treatments.


METHODS
This study delivered IRE pulses in nonanimal, as well as in ex vivo and in vivo tissue, with and in the absence of expired radiotherapy seeds. Electrical current was measured and lesion dimensions were examined macroscopically and with magnetic resonance imaging. Finite-element treatment simulations predicted the effects of brachytherapy seeds in the targeted region on electrical current, electric field, and temperature distributions.


RESULTS
There was no significant difference in electrical behavior in tissue containing a grid of expired radiotherapy seeds relative to those without seeds for nonanimal, ex vivo, and in vivo experiments (all p > 0.1). Numerical simulations predict no significant alteration of electric field or thermal effects (all p > 0.1). Histology showed cellular necrosis in the region near the electrodes and seeds within the ablation region; however, there were no seeds beyond the ablation margins.


CONCLUSIONS
This study suggests that electroporation therapies can be implemented in regions containing small metallic implants without significant changes to electrical and thermal effects relative to use in tissue without the implants. This supports the ability to use IRE as a salvage therapy option for brachytherapy.
Radiology Research Unit, Department of Radiology, The Alfred Hospital, 1st Floor Philip Block, 55 Commercial Road, Melbourne, VIC, 3004, Australia. robert.neal@alfred.org.au.
Robert E
RE
Neal
William Buckland Radiotherapy Centre, The Alfred Hospital, 55 Commercial Road, Melbourne, VIC, 3004, Australia.
Ryan L
RL
Smith
Radiology Research Unit, Department of Radiology, The Alfred Hospital, 1st Floor Philip Block, 55 Commercial Road, Melbourne, VIC, 3004, Australia.
Helen
H
Kavnoudias
Department of Surgery, Monash University, 55 Commercial Road, Melbourne, VIC, 3004, Australia.
Franklin
F
Rosenfeldt
Department of Surgery, Monash University, 55 Commercial Road, Melbourne, VIC, 3004, Australia.
Ruchong
R
Ou
Department of Anatomical Pathology, The Alfred Hospital, 55 Commercial Road, Melbourne, VIC, 3004, Australia.
Catriona A
CA
Mclean
School of Biomedical Engineering and Sciences, Virginia Tech, 329 ICTAS Building, Stranger St. (MC 0298), Blacksburg, VA, 24061, USA.
Rafael V
RV
Davalos
Radiology Research Unit, Department of Radiology, The Alfred Hospital, 1st Floor Philip Block, 55 Commercial Road, Melbourne, VIC, 3004, Australia.
Kenneth R
KR
Thomson
D000818:Animals; D001918:Brachytherapy / Q000379:methods*; D017115:Catheter Ablation / Q000379:methods; D004285:Dogs; D004553:Electric Conductivity; D053672:Electrochemotherapy / Q000379:methods*; D018274:Electroporation / Q000379:methods*; D005240:Feasibility Studies; D008297:Male; D008670:Metals; D008954:Models, Biological; D008962:Models, Theoretical; D011467:Prostate; D016879:Salvage Therapy / Q000379:methods*; D011198:Solanum tuberosum
D008670:Metals