Electroporation Dosimetry for Percutaneous Tumor Ablation

How electroporation ablation works

In IRE, needle electrodes are placed percutaneously around the tumor. The generator delivers trains of microsecond electrical pulses — typically 70 to 100 pulses at voltages up to 3,000 V — between electrode pairs. These pulses create intense, localized electric fields that permanently disrupt the tumor cell membranes, triggering cell death through apoptosis rather than thermal coagulation.

Because the mechanism is non-thermal, IRE preserves the structural integrity of adjacent bile ducts, major vessels, nerves, and connective tissue. This makes it suitable for tumors close to the hepatic hilum, the portal vein, or the pancreatic duct — locations where radiofrequency or microwave ablation would cause collateral injury.

ECT operates on the same principle using lower-voltage reversible pulses, combined with intravenous chemotherapy agents (bleomycin or cisplatin). The transient membrane permeabilization dramatically increases intracellular drug uptake, enhancing cytotoxicity.

The electroporation dosimetry problem

The treated zone in IRE is determined entirely by where the electric field exceeds a tissue-specific lethal threshold — approximately 400 to 700 V/cm depending on tissue type. The ablation zone is invisible during the procedure.

The electric field distribution is three-dimensional and sensitive to several patient-specific factors:

• Individual tissue electrical conductivity, which varies with tumor type, necrosis, fat content, and hydration
• Exact electrode geometry — inter-electrode distances, placement angles, and depth
• Pulse parameters including voltage, pulse duration, and number of pulses
• Local anatomy (adjacent blood vessels conduct current differently from parenchyma)

Without patient-specific modeling, operators rely on manufacturer nomograms derived from population averages and ex vivo experiments. These provide no information about tumor coverage margins for the specific patient on the table. Studies have documented local recurrence rates of up to 90% when tumor coverage falls below 95% of the target volume.^[1]

Patient-specific electric field simulation

hapchot generates a three-dimensional simulation of the electric field distribution by solving the electrostatic equations on a finite element mesh derived from the patient's CT or MRI. The simulation uses:

• Actual electrode coordinates confirmed intra-operatively
• Tumor segmentation from pre-operative imaging
• Tissue-specific electrical conductivity values
• Real pulse parameters as entered by the operator

The output is a predicted ablation zone overlaid on the patient's anatomy. The operator can verify whether the predicted zone covers the tumor and its safety margin before any pulse is delivered. If coverage is insufficient, electrode positions can be adjusted and the simulation re-run — still before treatment begins.

The intra-operative phase uses elastic image registration to account for organ deformation and respiratory motion between the pre-operative scan and the procedure, generating an updated digital twin that reflects current anatomy.

Clinical evidence

Five peer-reviewed studies from INRIA MONC and the interventional radiology unit of Hôpital Avicenne (APHP) validate the numerical simulation approach underlying hapchot. The two most directly relevant to clinical dosimetry are below. See the research page for the full publication list.