The Video Tumor Fighter magnetic manipulation system

The Video Tumor Fighter (VTF) is a technique for producing a highly localized hyperthermia treatment for deep-seated brain tumors. A ferromagnetic seed is guided through the neural tissues by means of a magnetic field gradient produced by an external coil, and then heated by radio-frequency (rf) induction. The purpose of the work described here was to design, build, and test a motion control system enabling magnetic guidance of the seed. A 182-turn, 40 cm OD, 18 cm ID water-cooled coil is powered by twelve SCR-controlled deep-cycle batteries providing 600 A at 40 V (maximum). A maximum magnetic field gradient of approximately 2.0 T/m is generated at a point of ≈ 6.2 cm along the axis of the coil. The coil is mounted in a specially-designed goniometer that allows motion in the vertical and lateral directions, as well as azimuthal and polar rotations. In vivo studies on canine animal models with 5.0 mm diameter by 4.5 mm long NdBFe seeds resulted in anterior-posterior rectilinear motions, transverse motion through the corpus callosum, and circuital motions resulting in retrieval of the seed. Positioning could be managed to within ± 2 mm by adjusting the coil's current and location. The seed's pathway through the brain was monitored by superimposing real-time fluorograms onto preoperative MRI scans. No significant tissue damage was observed in post-mortem histological studies of the brain tissue. This work has pointed the way towards improvements to the guidance and imaging systems needed to facilitate the success of the Video Tumor Fighter in human clinical trials.

Note: Abstract extracted from PDF file via OCR.