Page 70 - PEN eBook July 2023

Design

As a technique for delivering electroporation, PFA is a non-thermal energy modality that has been
utilized for solid organ tumor ablation for some time. More recently, investigators have demonstrated
a unique safety profile and ablative efficacy related to its ability to selectively target cardiomyocytes

while sparing collateral damage to the connective tissue structure. This has driven significant
research into different pulse trains to determine the most effective approach for various use cases.

Established PFA approaches apply between 80 and 120 unipolar pulses, with a pulse duration of
50 to 100 ms and an electric field that exceeds 1,000 V/cm. While it can be effective, this typical IRE
protocol may evoke muscle contraction during the procedure, leading to pain for the patient and
causing displacement of the electrode needles.

Recently, a new type of IRE technique called high-frequency IRE (H-FIRE) has emerged. H-FIRE

uses a set of bipolar pulse bursts consisting of individual pulses with durations from 0.5 to 10 ms,
grouped into a burst of up to 100 ms.

As a specific example, there are multiple documented studies for the application of IRE to liver
tumors, with the earliest dating back to 2011. The tumors ranged in size from 2 mm to 100 mm,
although there was a high degree of commonality between the electrical parameters of the
IRE treatment. The applied voltage was always in the range of 1.5–3 kV/cm, with a duration of

70–100 µs, and the best results were obtained using plate electrodes to deliver 80 pulses of 100 ms
at 0.3 Hz, with an electrical field magnitude of 2.5 kV/cm across the tumor.

THE PFA CHALLENGE FOR POWER DESIGNERS

The primary challenge of power solution design for PFA systems is the need to deliver high-energy
HV pulses reliably and repeatably. For life-science applications, typically a power system in the
2- to 300-W region is all that is required. For surgical applications like PFA, individual pulses can be
up to 20 kW, with an average power for the system in the kilowatt region.

Figure 3: The primary challenge in PFA design is delivering precise HV waveforms.

70 JULY 2023 | www.powerelectronicsnews.com