For medical device designers working with Pulsed Electric Field (PEF) systems, it is commonly known that generator output is not rated in watts. By understanding which PEF output characteristics are truly important, designers can be confident that a Pulsed Field Ablation (PFA) generator will work clinically and be competitive in the market. This article draws on Engenious team member experience developing PFA systems that are in the market today.
A PEF generator can deliver 250,000 watts instantaneously. But that same generator may average only 250 watts delivered during a treatment. Both numbers are technically correct. Neither measure is a good indicator of clinical performance.
A power specification typically assumes continuous output, but a pulsed electric field generator’s output is not continuous. PEF energy delivery is highly structured and heavily gated. A treatment is organized into packets, which contain bursts, which contain individual pulses. A single pulse might last 1.5 microseconds at 5kV across a 50-ohm load—that is 250kW in the instant it fires. But between bursts, the generator’s output is off. Between packets, the waveform may be idle for anywhere from hundreds of milliseconds to several seconds. Average power across the entire treatment timeline yields a modest wattage that suggests a benign, low-power device. But average power is not an accurate method for determining clinical effects.
The defining behavior of a PEF system? In our experience: the structured, short, high-energy pulse.
If average power does not characterize performance, what does? Here is how the Engenious team approaches it:
Pulse energy (specified in joules). Energy delivery is the clinically meaningful quantity. Experienced clinical research teams invest significant lab time deriving energy specifications that produce the desired tissue treatment effects. These specifications may address total energy delivered per burst, per packet, per treatment, or often some combination. Energy specifications map directly to biological effects and provide a benchmark for verification and real-time control.
Voltage. Voltage determines the field strength applied to the load. A PEF generator must produce target voltages accurately and repeatably. At common 5 kV output levels, small deviations in output voltage can translate to significant variations in the electric field delivered to tissue and variations in the resulting therapeutic effect.
Pulse waveshape. The shape of an energy pulse matters enormously. Rise time, fall time, flatness across the pulse peak, and consistency across a burst all affect the electroporation outcome. A generator that produces clean 1.5-microsecond pulses at 5kV is a fundamentally different device than one that produces ragged, ringing waveforms at the same nominal voltage.
Pulse/Burst/Packet timing. Pulse width, burst length, interburst delay, and interpacket delay combine to produce the desired biological effects and therapeutic outcome. If the generator drifts between pulses due to thermal effects or control loop lag, the delivered therapy is not what the algorithm specified.
Peak current. Tissue impedance is generally low, which means tens or even hundreds of amps can flow through the load. Designing a generator robust enough to handle this level of current is crucial to its long-term reliability. Because current flow and voltage together produce energy, knowing the maximum current flow also aids in determining how much energy storage capacity the generator requires.
When it comes to PEF devices, power specifications are a starting point at best, and a distraction at worst. That’s why Engenious emphasizes the clinically relevant parameters described above. It’s also why we engage with clients and clinicians early to develop requirements that produce repeatable clinical results and provide a reliable basis for verification.
PFA—Pulsed Field Ablation. A therapeutic technique that uses high-voltage electrical pulses to destroy targeted tissue through irreversible electroporation as opposed to thermal energy.
PEF—Pulsed Electric Field. The broader technology category; PFA is a clinical application of PEF. The terms are sometimes used interchangeably in medical device contexts, though PEF is the more general descriptor.
ESU—Electrosurgical Unit. A device that uses high-frequency electrical current to ablate, cut or coagulate tissue through thermal energy. ESUs are the established FDA category PFA generators are often regulated under, despite the different underlying mechanism.
RFG—Radio Frequency Generator. A generator that produces high-frequency alternating current for electrosurgical or ablation applications. RF ablation uses thermal energy to destroy tissue; often cited as the incumbent technology that PFA is positioned to improve upon in selectivity and safety profile.
