Verification and validation in canine cadaver of an MPI-integrable RF head coil for magnetic particle hyperthermia

Magnetic particle hyperthermia (MPH), the mild heating of solid tumors with magnetic nanoparticles, is an emerging treatment modality used as an adjuvant to therapies such as ionizing radiation. MPH can be paired with magnetic particle imaging (MPI) hardware to improve thermal treatment planning, spatially confined heating, and thermal dose delivery. In this work, we describe the design, verification, and validation of a radiofrequency (RF) head coil designed to integrate into a clinical MPI scanner.

The RF coil was designed to accommodate an adult human head, provide a homogeneous (±10%) field along a 10 cm axial centerline, generate a peak magnetic flux density of 10 mT at 100 kHz, and be MPI compliant. Verification of the design consisted of a combination of magnetic field and nanoparticle heating measurements. To validate an MPI/MPH imaging and heating workflow, a canine cadaver was surgically prepared by implanting magnetic nanoparticles in the brain, followed by anatomical imaging, MPI, and heating with the head coil. To explore if the measured performance can be generalized to human treatment, we conducted a virtual MPH treatment of a human glioma.

Coil performance verification demonstrated RF fields as high as $B_{\text{peak}}=14$ mT at 100.4 kHz, while achieving hyperthermic temperatures in tumor phantoms. The MPI scan of the canine cadaver head revealed differences in signal intensity between particle injection sites, which correlated with temperature increases measured during heating. Computational simulation of a human head showcased the feasibility of this system to treat gliomas.

We successfully constructed, verified, and validated an MPI-compatible RF head coil for combined MPI/MPH therapy.