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The optimization of needle electrode number and placement for irreversible electroporation of hepatocellular carcinoma.

Adeyanju OO, Al-Angari HM, Sahakian AV - Radiol Oncol (2012)

Bottom Line: We also found the distance between electrodes was far more important in influencing the outcome measures when compared with the depth of electrode insertion.Overall, the distribution of electric field is highly dependent upon the electrode configuration, but the optimal configuration can be determined using numerical modeling.Our findings can help guide the clinical application of IRE as well as the selection of the best optimization algorithm to use in finding the optimal electrode configuration.

View Article: PubMed Central - PubMed

ABSTRACT

Background: Irreversible electroporation (IRE) is a novel ablation tool that uses brief high-voltage pulses to treat cancer. The efficacy of the therapy depends upon the distribution of the electric field, which in turn depends upon the configuration of electrodes used.

Methods: We sought to optimize the electrode configuration in terms of the distance between electrodes, the depth of electrode insertion, and the number of electrodes. We employed a 3D Finite Element Model and systematically varied the distance between the electrodes and the depth of electrode insertion, monitoring the lowest voltage sufficient to ablate the tumor, V(IRE). We also measured the amount of normal (non-cancerous) tissue ablated. Measurements were performed for two electrodes, three electrodes, and four electrodes. The optimal electrode configuration was determined to be the one with the lowest V(IRE), as that minimized damage to normal tissue.

Results: The optimal electrode configuration to ablate a 2.5 cm spheroidal tumor used two electrodes with a distance of 2 cm between the electrodes and a depth of insertion of 1 cm below the halfway point in the spherical tumor, as measured from the bottom of the electrode. This produced a V(IRE) of 3700 V. We found that it was generally best to have a small distance between the electrodes and for the center of the electrodes to be inserted at a depth equal to or deeper than the center of the tumor. We also found the distance between electrodes was far more important in influencing the outcome measures when compared with the depth of electrode insertion.

Conclusions: Overall, the distribution of electric field is highly dependent upon the electrode configuration, but the optimal configuration can be determined using numerical modeling. Our findings can help guide the clinical application of IRE as well as the selection of the best optimization algorithm to use in finding the optimal electrode configuration.

No MeSH data available.


Related in: MedlinePlus

Depiction of the electrode configurations. (left) The purple circles represent active electrodes, and the lighter shaded electrodes are set to ground. The distance (d1) between electrodes and the depth of insertion (d2) was varied in the study.
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f1-rado-46-02-126: Depiction of the electrode configurations. (left) The purple circles represent active electrodes, and the lighter shaded electrodes are set to ground. The distance (d1) between electrodes and the depth of insertion (d2) was varied in the study.

Mentions: Mainly three different parameters of electrode configurations were analyzed for the study: 1) distance between electrodes 2) depth of electrode insertion 3) the number of electrodes. Basically, the parameter space for the distance between electrodes and the depth of electrode insertion was explored for three different electrode numbers: two, three, and four electrodes. The means of optimizing this was to increment the applied voltage at the active electrode(s) by 100 V intervals to the minimum value necessary to cover 95% of the tumor with an electric field sufficient to irreversibly electroporate the tumor tissue: VIRE. This electric field was set at 680 V/cm, as derived from Davalos et al..5 The voltage was iterated, and the criterion for tumor ablation was determined via the MATLAB™ environment. Also, we were able to visualize the region of irreversible electroporation (tissue ablation) using an isosurface plotted in the COMSOL® 3D environment. VIRE was determined at several electrode distances and depths, and the results were tabulated for two, three, and four electrodes. The seven different distances between the electrodes that were measured were 1 cm, 1.5 cm, 2 cm, 2.5 cm, 3 cm, 4 cm, and 5 cm. A distance of 1.9 cm was used for three electrodes as opposed to 2 cm to allow meshing with the electrodes close to the tumor border. The depths of insertion of the electrodes, as measured from the tumor’s spherical hemiline to the bottom of the electrodes, were 0.5 cm, 1 cm, 1.25 cm, and 1.5 cm (Figure 1). In previous studies (data not shown), we tested shallower depths, but they had exorbitantly large VIREs and thus were not included for these experiments.


The optimization of needle electrode number and placement for irreversible electroporation of hepatocellular carcinoma.

Adeyanju OO, Al-Angari HM, Sahakian AV - Radiol Oncol (2012)

Depiction of the electrode configurations. (left) The purple circles represent active electrodes, and the lighter shaded electrodes are set to ground. The distance (d1) between electrodes and the depth of insertion (d2) was varied in the study.
© Copyright Policy - open-access
Related In: Results  -  Collection

License 1 - License 2
Show All Figures
getmorefigures.php?uid=PMC3472940&req=5

f1-rado-46-02-126: Depiction of the electrode configurations. (left) The purple circles represent active electrodes, and the lighter shaded electrodes are set to ground. The distance (d1) between electrodes and the depth of insertion (d2) was varied in the study.
Mentions: Mainly three different parameters of electrode configurations were analyzed for the study: 1) distance between electrodes 2) depth of electrode insertion 3) the number of electrodes. Basically, the parameter space for the distance between electrodes and the depth of electrode insertion was explored for three different electrode numbers: two, three, and four electrodes. The means of optimizing this was to increment the applied voltage at the active electrode(s) by 100 V intervals to the minimum value necessary to cover 95% of the tumor with an electric field sufficient to irreversibly electroporate the tumor tissue: VIRE. This electric field was set at 680 V/cm, as derived from Davalos et al..5 The voltage was iterated, and the criterion for tumor ablation was determined via the MATLAB™ environment. Also, we were able to visualize the region of irreversible electroporation (tissue ablation) using an isosurface plotted in the COMSOL® 3D environment. VIRE was determined at several electrode distances and depths, and the results were tabulated for two, three, and four electrodes. The seven different distances between the electrodes that were measured were 1 cm, 1.5 cm, 2 cm, 2.5 cm, 3 cm, 4 cm, and 5 cm. A distance of 1.9 cm was used for three electrodes as opposed to 2 cm to allow meshing with the electrodes close to the tumor border. The depths of insertion of the electrodes, as measured from the tumor’s spherical hemiline to the bottom of the electrodes, were 0.5 cm, 1 cm, 1.25 cm, and 1.5 cm (Figure 1). In previous studies (data not shown), we tested shallower depths, but they had exorbitantly large VIREs and thus were not included for these experiments.

Bottom Line: We also found the distance between electrodes was far more important in influencing the outcome measures when compared with the depth of electrode insertion.Overall, the distribution of electric field is highly dependent upon the electrode configuration, but the optimal configuration can be determined using numerical modeling.Our findings can help guide the clinical application of IRE as well as the selection of the best optimization algorithm to use in finding the optimal electrode configuration.

View Article: PubMed Central - PubMed

ABSTRACT

Background: Irreversible electroporation (IRE) is a novel ablation tool that uses brief high-voltage pulses to treat cancer. The efficacy of the therapy depends upon the distribution of the electric field, which in turn depends upon the configuration of electrodes used.

Methods: We sought to optimize the electrode configuration in terms of the distance between electrodes, the depth of electrode insertion, and the number of electrodes. We employed a 3D Finite Element Model and systematically varied the distance between the electrodes and the depth of electrode insertion, monitoring the lowest voltage sufficient to ablate the tumor, V(IRE). We also measured the amount of normal (non-cancerous) tissue ablated. Measurements were performed for two electrodes, three electrodes, and four electrodes. The optimal electrode configuration was determined to be the one with the lowest V(IRE), as that minimized damage to normal tissue.

Results: The optimal electrode configuration to ablate a 2.5 cm spheroidal tumor used two electrodes with a distance of 2 cm between the electrodes and a depth of insertion of 1 cm below the halfway point in the spherical tumor, as measured from the bottom of the electrode. This produced a V(IRE) of 3700 V. We found that it was generally best to have a small distance between the electrodes and for the center of the electrodes to be inserted at a depth equal to or deeper than the center of the tumor. We also found the distance between electrodes was far more important in influencing the outcome measures when compared with the depth of electrode insertion.

Conclusions: Overall, the distribution of electric field is highly dependent upon the electrode configuration, but the optimal configuration can be determined using numerical modeling. Our findings can help guide the clinical application of IRE as well as the selection of the best optimization algorithm to use in finding the optimal electrode configuration.

No MeSH data available.


Related in: MedlinePlus