High-Frequency Nanosecond Pulsed Magnetic Field Generator Utilizing Stacked Spiral Coil for Subcutaneous Tumor Ablation in Vivo

To facilitate in vivo animal experiments exploring high-frequency nanosecond pulsed magnetic field therapy for tumor treatment, a specialized high-frequency nanosecond pulsed magnetic field generator has been developed. This generator is crafted for ablative subcutaneous tumors in vivo, and its waveform is adjustable, enabling the generation of triangular, trapezoidal, and step-like pulsed magnetic fields. In response to the semi-convex ellipsoidal structure of surface tumors, this article introduces a novel low-inductance stacked spiral coil. Utilizing a genetic algorithm, optimal structural parameters are determined to enable the coil to generate higher magnetic induction intensity in the tumor region under a specified output capacity of the current generator. Subsequently, a six-stage linear transformer driver (LTD)-type nanosecond pulsed current generator with a continuous flow circuit for inductive loads is developed, capable of stably outputting a pulsed current of 800 A. In conclusion, the test results confirm the pulsed current generator’s ability to consistently produce a pulsed current with a repetition frequency of 10 kHz, a pulsewidth of 800 ns, and an amplitude of 800 A on a
$2.6~\mu \text{H}$
inductive load. As a result, it can generate triangular, trapezoidal, and step-shaped pulsed magnetic field in the ellipsoidal surface tumor area with a diameter of
$10\times 8\times8$
mm. These fields exhibit a width of 800 ns, a maximum operating repetition frequency of 10 kHz, and an average magnetic induction intensity of 0.75 T. This lays the groundwork for the subsequent implementation of animal experiments.