Design, verification and validation of a spatially confined magnetic nanoparticle thermal therapy device for conformal thermal dose contouring.

BACKGROUND

Magnetic nanoparticle thermal therapy (MNTT) can localize heat within tumors, but non-uniform nanoparticle distribution can limit thermal dose coverage. Spatially confined MNTT (SC-MNTT) addresses this limitation by using a static magnetic field (SMF) to suppress heating outside a selected field-free region (FFR). However, SC-MNTT platforms require improved FFR steering and closed-loop temperature control.

PURPOSE: This study developed and validated a low-cost, four-permanent-magnet SC-MNTT platform for spatially selective heating, dynamic FFR steering, and controlled thermal dose delivery in phantom models.

METHODS

The device combined four permanent magnets, an induction coil, motion and heating control, fiber-optic thermometry, and autotuning proportional-integral-derivative (PID) control. SMF maps and alternating magnetic field (AMF) defined operating conditions. Three-vial verification experiments evaluated spatially selective heating under pulsed AMF exposure. Liver-phantom validation experiments tested pulsed heating and autotuning PID control using prescribed temperature setpoint, a CEM43 target of 8 [min], and a healthy-tissue limit of 39.50 [°C].

RESULTS

The four-magnet configuration shifted the FFR between selected targets and concentrated heating at the intended nanoparticle location. In three-vial experiments, the selected vial reached normalized heating intensity near 1.00, while non-target vials remained lower between 0.09-0.26, corresponding to selective heating with reduced off-target activation. In liver-phantom experiments, autotuning PID control maintained a mean target temperatures 43.44 ± 0.01 [°C], achieved prescribed CEM43 at selected tumor probes, and kept the designated healthy-tissue probe below the safety threshold. Mean overshoot remained below 1.1 [%].

CONCLUSION

The four-magnet SC-MNTT platform enabled repeatable in-plane FFR steering, spatially confined heating, and closed-loop thermal dose delivery in phantom models.